Hydrogen engine system

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START

S1 SWitch ON Engine Key

S2 ROtate Starter

PaSt P

YES

S4 Ignite Plug

Past P ROtated 2 (Another Step)

Open SolenoidrS7 Control Valve END

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ated in the amount corresponding to the quantity of

HYDROGEN ENGINE SYSTEM heat transferred from the heat intermedium. In such a system as described above, on purpose of

FIELD OF THE INVENTION having the pressure of hydrogen at the predetermined The present invention is related to a hydrogen engine level, an inflow quantity of the exhaust gas into an ex system, a method for starting a hydrogen engine, a haust heat exchanger 67 and its inflow heat quantity are method for stopping a hydrogen engine, a metal hy controlled by an exhaust adjusting valve 68 which is dride container, a method for controlling heat of a netal actuated by the signals from a pressure controller 70. hydride container, a method for cooling a metal hydride O The temperture of the heat intermedium at the entrance container. side of the MH tank 65 will change in accordance with DESCRIPTION OF THE RELATED ART the changes of the inflow heat quantity into the exhaust heat exchanger 67.

In FIG. 14 is shown a hydrogen engine system utiliz For instance, if the pressure of hydrogen comes down ing metal hydride which is, for example, described in 5 below the predetermined level, the pressure controller "A trail manufacture of an engine system utilizing metal 70 will operate the exhaust adjusting valve 68 to send hydride" at page 247 of a collection 851 of "Autono the exhaust gas to the heat exchanger 67. As a result, the tive Technique Acadamic Seminors' published by Soci temperature of the circulating heat intermedium goes ety of Automotive Engineers, Inc. in May of 1985. up gradually and heats the alloy in the MH tank 65. In As shown in FIG. 14, an engine 61 is actuated with 20 this way, the amount of generated hydrogen increases, hydrogen generated in a metal hydride container and the pressure of hydrogen can be restored. (which will be called a MH tank hereinafer), and in an On the contrary, if the pressure goes up above the exhaust heat exchanger 67 the heat of its exhaust gas is, predetermined level, it will do reverse. via a heat intermedium pipe 27, transferred to heat inter In the system as described above, however, the time medium circulating in the MH tank 65 at a constant constant of the process in terms of the pressure control quantity of flow.

The heat intermedium is heat-exchanged with metal ler 70 is large because of the heat capacity of the heat hydride at the MH tank 65, and the MH tank 65 which intermedium circulating system including the exhaust has received heat releases hydrogen in accordance with heat exchanger 67, and the unstable changes of hydro the equilibruim conditions of the metal hydride deter gen pressures unavoidably come about based upon such mined by temperature and pressures. The heat ex 30 a time delay. Especially, when an engine load is sud changes at the MH tank are performed as described denly changed, the pressure of hydrogen is also largely below: changed, and it can be a factor to impede a stable opera Firstly, the heat flow Qin can be attained as below; tOn.

FIG. 15 shows the results of the operating simulations 35 of the system shown in FIG. 14.

(1), The axis of abscissas shows time (second), and the on conditions of axis of ordinates shows temperature (C.) and ten times

multiplied pressure of hydrogen (kg/cm2G). Engine

Average temperature of the heat intermedium in the loads are shown in the same figure, and full loads and idlings were repeated a few times. Just after starting the

Twin: Temperature of the heat intermedium at an en operation, hydrogen is generated excessively even at idling because hydrogen is occluded at its full amount at trance of the tank,

Tout: Temperature of the heat intermedium at an exit of the start of the operation.

When the MH engine 61 comes to its full load, the

Tn: Average temperature of the metal hydride in the hydrogen pressure is controlled around 8 kg/cm of a tank, predetermined level. At 1,200 seconds, however, the Ren: Heat resistance between the heat intermedium and hydrogen pressure exceeds the predetemined level in the alloy, large amount according to a rapid decrease of the en y: Specific weight of the heat intermedium, 50 gine load.

C: Specific heat of the heat intermedium, After that, during a long idling, the hydrogen pres F: Quantity of flow of the heat intermedium circulat sure is lowered because a little lack of heat quantity of ing in the tank. the exhaust gas prevents the intermedium temperature The alloy temperature T can be attained as below; from going up. About 6 minutes after a second full load

of 3,500 seconds, the hydrogen pressure manages to (2), 55 come to the predetermined level, but unstable changes

On = a-Fe (3), of the hydrogen pressure can not stop. In general, a driving mechanism of a hydrogen en on condition of gine, for example, that of a hydrogen engine with carbu a: Quantity of heat of hydrogen dissociation kcal/Nm 60 retors, has a pipe connecting a MH tank with the en Fe: Quantity of flow of the generated hydrogen, gine, and after hydrogen gas is pressure-adjusted by a Q: Quantity of flow of the heat losed at the surface of regulater provided at the pipe, the gas goes from the the tank, carburetor through an intake manifold to the inside of a Cn: Heat capacity of the alloy. combustion chamber where the gas is ignited by sparks If the MH tank 65 is heat-insulated, the Q can be 65 of a spark plug. Thus, the hydrogen gas is exploded to low. Accordingly, when the MH alloy comes to a heat start the engine.

equilibrium, a relationship Qwn=Qm can be attained An igniter has to be turned off to cease sparking the according to the (2) equation, and hydrogen is gener spark plug so that the engine stop. At almost the same

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time, the metal hydride stops being heated and the sup By the way, as another MH tank adopted in a hydro ply of hydrogen gas to the engine is cut off. gen engine for a vehicle, the one which is shown in However, the hydrogen gas in the pipe on its way to FIG. 18 has been also known. The MH tank 91 has a the engine is not burned and does not exhaust out of the substantially cylindrical tank body 92, in the inside of engine just where the engine stops. Accordingly, there which the metal hydride M is previously contained. remains hydrogen gas in the regulator, the carburetor, The generated hydrogen gas, as fuel, is provided into and the intake manifold of the engine. When the engine the hydrogen engine via a hydrogen gas pipe 93. restarts, the explosion outside the combustion chamber In this case, the heat intermedium for heating the occurs, which is usually called a backfire, because the metal hydride M is the cooling water which has been residual hydrogen gas makes hydrogen density higher 10 heated by cooling the hydrogen engine, and is the ex at the start of sparking. Ways to develop the art to haust gas of high temperature exhausting from the hy prevent the backfire at the start of the engine have been drogen engine. The heat intermedium circulates in the considered because the continuous backfires make the spiral pipes 94 provided in the tank body 92. The heat engine stop. exchanging efficiency can be improved because of this 15 spiral shape of the pipes 94.

As one of metal hydride tanks (MH tanks), the one In the aforementioned MH tank 91, however, there is which is shown in FIGS. 16 and 17 is well known (Japa a problem of unstable movement of the metal hydride nese Laid-Open Patent Publication No. 62-49100). M having the form of fine grain because only the pipes The MH tank 81 comprises a tank body 82 of cylin 93 and 94 are provided in the tank body 92. In other drical shape in which metal hydride metal hydride M of words, when the tank body 92 is loaded on a vehicle fine grain is previously provided. The metal hydride M which has to move hard during its operation, there is a occludes and release hydrogen gas in response to the heat exchanging reaction. A hydrogen gas introducing probability that the metal hydride M moves around and entrance 82a is provided at a bottom of the tank body vibration. Inunevenly is arranged in the tank body 92 because of the this case, the heat exchanging effectiveness 82, and a hydrogen gas discharging exit 82b is provided of the metal hydride M has to be lower. A large prob at a top of the tank body 82. In the tank body 82 are lem of uneven arrangement of the metal hydride M can provided a shelf 85 having a cylindrical frame 83 and be expected, especially, with plural hydrogen filters 84 which forms stories in the hard crosswise as well as back aand forklift which moves forth.

shelf 85, by which the inside of the tank body 82 is divided into many rooms. 30 SUMMARY OF THE INVENTION In the tank body 82 is provided a pipe 86 having heat It is an object of the present invention to provide a intermedium circulate therein which goes through the hydrogen engine system and a method for controlling inside of the tank body 82 in order to exchange heat heat of a metal hydride container which make the sup with the metal hydride M. ply of hydrogen to the engine stable and enable the In order that the metal hydride M which has previ 35 smooth operation of the whole system. ously occluded hydrogen gas might release the hydro Another object of the present invention is to provide gen gas, heat intermedium such as hot water is sent into a method for starting a hydrogen engine which enables the pipe 86, and the heat of the intermedium as reaction the smooth start of the engine by avoiding a backfire. heat brings about heat exchanging reaction, therefore, Further object of the present invention is to provide the metal hydride M releases the hydrogen gas. a method for stopping a hydrogen engine which ensures The generated hydrogen gas, then, goes out of the the fine start of the engine by avoiding a backfire at the tank body 82 through the hydrogen gas discharging exit restarting of the engine.

82b. Another object of the present invention is to provide On the other hand, in order to have the metal hydride a metal hydride container and a method for cooling the M, which has already released the hydrogen gas, oc 45 container which can avoid the expansion stress on metal clude the hydrogen gas again, heat intermedium such as hydride at the time of occluding hydrogen gas, which cold temperature water circulates in the pipe 86 while prevents higher manufacturing cost, and which will not the hydrogen gas keeps coming in from the hydrogen cause the substantial decrease of the capacity for having gas introducing entrance 82a. Accordingly, the metal the metal hydride.

hydride M occludes the hydrogen gas, and the reaction 50 Further object of the present invention is to provide heat generated then at the metal hydride M is released a metal hydride container which can prevent the un out of the tank body 82 via the heat intermedium. even arrangement of metal hydride and can more effec The metal hydride M then has cubical expansion at tively prevent the lowering of the heat exchanging the same time of releasing the reaction heat, but its efficiency of the metal hydride.

expansion stress is divided by the hierarchical shelf 85, 55 To achieve the above objects, a hydrogen engine so that the concentration of stress upon the tank body 82 system of the present invention comprises an engine, a and the like be prevented. metal hydride container which is connected with the In the aforementioned MH tank 81, however, the engine and provides the engine with hydrogen, heat hierarchical shelf 85 constituted of the frame 83 and the intermedium providing means which is connected with hydrogen filters 84 is provided in the tank body 82, and the meal hydride container and provides the metal hy to install the shelf 85 is a comprising procedure consid dride container with the heat intermedium, first control ering the interference with the pipe 86. Consequently, ling means which is connected with the heat interme there is a problem of higher cost because several manu dium providing means and controls the heat interme facturing steps are required to install the shelf 85. dium providing means so as to keep the temperature of Moreover, there is another problem that the substan 65 the heat inermedium which is delivered into the metal tial capacity for containing the metal hydride M has to hydride container at a constant value, and second con be smaller to the extent of the space required for the trolling means which is connected with the heat inter shelf 85 in the tank body 82. medium providing means between the first controlling

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means and the metal hydride container and controls the metal hydride container (which is referred to as a MH supply amount of the heat intermedium from the heat tank hereinafter) 5 which has metal hydride therein is intermedium providing means to the metal hydride thermally connected with the heat exchanger 7 via heat container. intermedium which circulates in a heat intermedium Other objectives of the present invention will become 5 pipe 12 by means of a circulator pump 6. A temperature apparent with an understanding of the embodiments switch 17 as a heat controlling device is connected with discussed later, and the appended claims. Further, many the heat intermedium pipe 12 at a heat intermedium advantages not mentioned in this specification will be entrance side of the MH tank 5. The temperature switch come obvious to one skilled in the art upon application 17 controls the exhaust adjusting valve 8 to adjust the of the present invention. O inflow amount of exhaust gas from the engine 1 to the BRIEF DESCRIPTION OF THE DRAWINGS heat exchanger 7, so that the temperature of the heat intermedium in the heat intermedium pipe 12 can be

FIG. 1 is a schematic diagram showing a hydrogen maintained substantially at the maximum level at the engine system of the first embodiment of the present heat intermedium entrance side of the MH tank 5. The

FIG. 2 is a schematic diagram showing a modified above temperature of the heat intermedium is kept at 85 C. in the present embodiment, but it goes without embodiment of the first embodiment,

FIG. 3 is a graph showing the results of the operating saying that this temperature value can change corre sponding to heat intermedium.

simulations of the system shown in FIG. 1, At the heat intermedium entrance side of the MH FIG. 4 is a schematic diagram showing an engine 20 tank 5, an adjusting valve 15 is provided at the heat starter of the second embodiment,

FIG. 5 is a flow chart showing a method for starting the MH tankpipe intermedium 12 and adjusts the inflow amount, into .

5, of the heat intermedium heated at the an engine by means of the starter of FIG. 4,

FIG. 6 is a schematic diagram showing an engine heat exchanger 7. At the heat intermedium pipe 12 stopping device of the third embodiment, 25 between the upstream side of the adjusting valve 15 and FIG. 7 is a flow chart showing a method for stopping a heat intermedium exit side of the MH tank 5, is pro an engine by means of the device of FIG. 6, vided a valve 16 which bypasses the heat intermedium FIG. 8 is a partially broken side view showing a metal in the heat intermedium pipe 12 in accordance with the hydride container of the fourth embodiment, inflow amount of the heat intermedium through the FIG. 9 is a sectional view taken along line IX-IX of 30 adjusting valve 15 into the MH tank 5 so as to prevent FIG. 8, the circulation of the heat intermedium from stopping. FIG. 10 is a partially broken plan view showing a With the MH tank 5 is connected a hydrogen pipe 14 group of pipes arranged at the top story, to provide the engine 1 with the hydrogen which the FIG. 11 is a partially broken prespective view show metal hydride in the MH tank 5 has generated. At the ing a hydrogen occluding alloy container of the fifth hydrogen pipe 14 is provided a pressure reducing valve embodiment, 9 which maintains the pressure of the hydrogen sup FIG. 12 is a partially broken plan view showing fins plied from the MH tank 5 to the engine 1 below a con and a cooling water pipe, stant level. The adjusting valve 15 controls the inflow FIG. 13 is a side view showing a metal hydride con amount of the heat intermedium into the MH tank 5 tainer loaded on a forklift, corresponding to the pressure of the supplied hydrogen FIG. 14 is a schematic diagram showing a hydrogen 40 in the hydrogen pipe 14.

engine system of a related art, A method for controlling heat of the above hydrogen FIG. 15 is a graph showing the results of the operat engine system is now described hereinafter; ing simulations of the system shown in FIG. 14, Exhaust gas from the engine 1 goes through the heat FIG. 16 is a sectional view showing a metal hydride 45 exchanger 7 and heats the heat intermedium in the pipe container of a related art, 12 up to the maximum temperature while being con FIG. 17 is a sectional view taken along line XVII trolled by the exhaust adjusting valve 8 in its inflow -XVII of FIG. 16, amount. The heated heat intermedium goes through the FIG. 18 is a partially broken side view showing a MH tank 5 and heats the metal hydride in the MH tank metal hydride container or a related art. SO 5 in accordance with its inflow amount which is ad DESCRIPTION OF THE PREFERRED justed by the adjusting valve 15. Accordingly, the metal EMBODIMENTS hydride generates hydrogen in the amount correspond The First Embodiment ing to the degree of the received heat, and the generated hydrogen is supplied to the engine 1 via the hydrogen

A hydrogen engine system of the first embodiment of 55 pipe 14 while being adjusted, in its pressure, by the the present invention is now described hereinafter refer pressure reducing valve 9.

ring to FIG. 1; In the above hydrogen engine system, temperature of A radiator 3 is connected with a hydrogen engine 1 the circulating heat intermedium is always maintained via a cooling water pipe 11 which is used for carrying at a maximum value if the capacity of heat source, the water to cool the engine . A temperature switch 4 and amount of exhaust gas in the present embodiment, is a cooling water pump 2 are connected between the sufficient. Accordingly, the quantity of heat into the radiator 3 and the engine 1, and the cooling water MH tank 5 is adjusted by changing the inflow amount of cooled at the radiator 3 is supplied to the engine 1 by the heat intermedium into the MH tank 5. means of the pump 2. The temperature of cooling water In a method for controlling heat of a hydrogen engine of the present embodiment is maintained, for example, 65 system of a related art as shown in FIG. 14, the quantity at 80 C. by means of the temperature switch 4. of heat into a MH tank is adjusted by heightening and A heat exchanger 7 is connected with the engine 1 via lowering the temperature Twof warm water according an exhaust pipe 13 and an exhaust adjusting valve 8. A to the equation (l). On the other hand, in the method for

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controlling heat in the present embodiment, the quan In the aforementioned modified embodiment, the tity of heat into the MH tank 5 is controlled by chang heat intermedium delivered from the engine 1 by the ing the inflow amount F of warm water. circulator pump 6 can be supplied directly to the MH Consequently, the unstable changes of hydrogen tank 5 without passing through the heat exhanger 7, so pressure can be lessened because the inflow amount of 5 that the heat exchanger 7 can be left out. Consequently, the heat intermedium into the MH tank 5 can be in the size of the hydrogen engine system can be smaller. stantly increased and decreased by opening and closing The Second Embodiment the adjusting valve 15 which has a quick response to the drastic changes on the amount of the hydrogen being The hydrogen engine system of the second embodi used. At a sudden drop of the load of the engine 1 dur 10 ment of the present invention is described hereinafter in ing idoling or the like, the abnormal increase of hydro details referring to FIGS. 4 and 5; gen pressure can be minimized when the inflow of the As shown in FIG. 4, metal hydride is contained in a heat intermedium into the MH tank 5 is stopped because MH tank 21, and generates hydrogen gas while being heated by exhaust gas, cooling water of high tempera the sensible heat of the heat intermedium in the MH tank 5 is low. 15 ture which has been heated at cooling an engine and so As described above, the method, of the present em on. A filter 22 communicating with the MH tank 21 bodiment, for controlling heat can lower the unstable removes foreign materials such as fine alloy powders changes of hydrogen pressure, which often occur in the mixed in the hydrogen gas. The purified hydrogen gas is related art due to the sudden change of the load. delivered to a pressure reducing valve 24 via a nonre 20 turn valve 23 arranged at a lower stage. The nonreturn

FIG. 3 shows the results of the operating simulations valve 23, when backfire occurs, prevents the flame from with the method, of the present embodiment, for con entering the MH tank 21. The pressure reducing valve trolling heat by using the same facility under the same 24 delivers operating conditions as those of the operating simula control valvethe25 hydrogen after gas to an electormagnetic reducing the pressure of the hy tions of the hydrogen engine system as shown in FIG. 25 drogen gas to the level which is predetermined based on

As shown in FIG. 3, the pressure exceeds the prede the safety of a pipe and so on. termined level just after starting the operation because over The electromagnetic control valve 25 can be changed of the reasons as explained above. The hydrogen pres b. Atbetween two positions, a position a and a position sure after a full load operation is, however, shown to be 30 delivered from theb shown the position pressure in FIG. 4, the hydrogen gas reducing valve 24 is pre extremely stable.

The gradual decrease of the heat intermedium tem magnetic control valve 25 is changedWhen vented from flowing downstream.

over the electro to the posi perature during a long idoling is due to the lack of the tion a, the hydrogen gas is pressure-adjusted approxi quantity of heat supplied from the engine 1. But if the mately to the atmospheric pressure at a regulator 26 quantity of heat is sufficient, the temperature of the heat 35 arranged at a lower stage, and then is delivered to a intermedium is maintained exactly at 85 C. carburetor 27 at a lower stage. In the carburetor 27, the In the modified embodiment of the first embodiment hydrogen gas is mixed up with the air coming through as shown in FIG. 2, a heat intermedium pipe 20 at the an air cleaner 28. The hydrogen gas, then, goes through heat intermedium exit side of the MH tank 5 is con nected with the cooling water pump 2 for delivering an intake manifold 30, and is compressed into a combus tion chamber (not shown). In the combustion chamber, cooling water to the engine 1 in stead of being con the hydrogen gas is burned at the sparking of a spark nected with the circulator pump 6 which has the heat plug. 31.

intermedium circulate. On the other hand, the circula An electric formation for actuating the electromag tor pump 6 is connected with the cooling water pipe 11 netic control valve 25 is now described; and delivers the hot cooling water as the heat interme 45 A controller 33 actuates and stops a starter 34 of an dium, which has been heated while cooling the engine, engine 29 based on the on and off operations of an en into the MH tank 5 by way of the heat exchanger 7 and gine key switch 32, and further ignites and stops igniting the adjusting valve 15. The rest of the structure is the the spark plug 31 by means of an ignitor 35 while count same as that of the first embodiment. ing time by means of a built-in timer therein according In the modified embodiment, the cooling water as the 50 to a prestored program. The controller 33 outputs sig heat intermedium which passes through the MH tank 5 nals to the electromagnetic control valve 25 to magne is cooled down due to the endothermic effect, when tize and demagnetize the valve 25, and changes over the hydrogen being generated, of the metal hydride in the valve 25 to either the position a or the position b, so that MH tank 5. The heat intermedium is, then, supplied to the MH tank 21 and the engine 29 communicate with the engine 1 via the cooling water pump 2, and cools the 55 each other or are cut off from each other. The control engine 1 with the cooling water from the radiator 3. ler 33 is also connected with an engine rotation sensor Namely, the MH tank 5 as a heat sink assists the cooling 36 which detects the rotation of the engine 29, and effect of the radiator 3 on the engine 1. Accordingly, monitors the rotation of the engine 29 according to the capacity and the size of the radiator 3 can be small, signals from the rotation sensor 36. so that the hydrogen engine system and consequently A method for controlling the start of the engine 29 as the whole vehicle which loads the hydrogen engine composed and formulated above is now described refer system can be manufactured in small size. Moreover, ring to FIG. 5;

the hydrogen engine system of the present modified Now, the engine 29 is being stopped, the electromag embodiment is suitable for the vehicle, which usually netic control valve 25 is kept at the position b, and the runs at low speed and tends to have its engine over 65 MH tank 21 and the enging 29 are being cut off from heated, such as a forklift because the cooling of the each other. Then, when the key switch 32 is turned on engine 1 is sufficiently performed by both the radiator 3 to start the engine 29, the controller 33 confirms it at and the MH tank 5. step S1 (Steps are referred to as Shereinafter.), and

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rotates the starter 34 to rotate the engine 29 idle at S2. mainifold 30 in the engine 29 or so since the last stop off The residual hydrogen gas, which has remained in the the engine 29 exhausts out of the engine 29. regulator 26, the carburetor 27, and the intake manifold Moreover, in the present embodiment, the judgement 30 since the last stop of the engine 29, therefore exhausts whether the residual hydrogen gas is still there or not is out of the engine 29. The controller 33 counts the time made based on time, but by means of detecting the of the idle rotation of the engine 29, and waits for a number of the rotation of the engine 29 rotated by the certain amount of time (It is 1.5 seconds in the present starter 34, the judgement on the presence of the residual embodiment) till the hydrogen gas which has remained hydrogen gas can be made based on the number of the since the last stop of the engine is completely exhausted. rotation.

After this amount of time has passed, the controller 33 10 The Third Embodiment sparks the spark plug 31 via the ignitor 35 at the next S4.

Moreover, after predetermined time (0.5 seconds) has The third embodiment of the present invention is passed at S5, namely, at the time when the spark plug 31 now described hereinafter referring to FIGS. 6 and 7; is completely ready for being sparked, at S6 the control The present embodiment shows a method for stop ler 33 checks, by means of signals from the engine rota 15 ping the same hydrogen engine system as that of the tion sensor 36, whether the engine 29 is surely rotating second embodiment.

or not. This is for avoiding such situation as the hydro As shown in FIG. 6, the electromagnetic control gen gas is supplied to the engine 29 while the engine 29 valve 25 is kept at the position a, and the engine 29 runs is not rotating because the starter 34 does not rotate due with the hydrogen gas supplied from the MH tank 21. to the death of the battery and so on. When it is judged 20 When the key switch 32 is turned off to stop the engine that the engine 29 is rotating, the controller 33 sends 29, the controller 33 comfirms it at the step S1 (Step will signals to the electromagnetic control valve 25 at S7, be referred to as Shereinafter.), and changes the posi and magnetizes the electromagnetic control valve 25 to tions of the electromagnetic control valve 25 from the change the positions from the position b to the position position a to the position b to cut off the MH tank and a. Then, the MH tank 21 and the engine 29 come to 25 the engine 29 from each other at S3 while driving the communicate with each other, and the hydrogen gas is ignitor 35 to keep the spark plug 31 of the engine 29 in delivered for the engine 29. Consequently, after the sparking conditions at S2. Accordingly, the hydrogen hydrogen gas is mixed with the air in the carburetor 27, gas no longer remains in the regulator 26, the carburetor the first explosion is performed in the combustion cham 27, the intake manifold 30 and so on because all the ber of the engine 29, and the engine 29 starts running. 30 hydrogen gas remaining at the downstream side of the By the way, when it is sensed that the engine 29 is not electromagnetic control valve 25 is compressed into the rotating at S6, the starter 34 and so on are considered to combustion chamber (not shown) with sucking actions be out of order, and the controller 33 takes different of a piston (not shown) moving in the engine 29 and is actions which are not described in the present embodi burned therein to exhaust into the atmosphere. et. 35 After the aformentioned residual hydrogen gas ex The engine 29 can stop as the key switch 32 is turned hausts out of the engine 29, if the controller 33 judges, off to stop sparking the spark plug 31 and to change the according to the signals from the engine rotation sensor positions of the electromagnetic control valve 25 from 36, that the engine 29 stops rotating at S4, the controller the postion a to the position b via the controller 33, and 33 stops sparking the spark plug 31 via the ignitor 35 as the metal hydride in the MH tank 21 stops being and completes the stopping operation of the engine 29. heated in an appropriate way. In the method for stopping the engine 29 as described As described above, the backfire is certainly pre above, all the hydrogen gas remaining in a route from vented in the aforementioned embodiment because the the electromagnetic control valve 25 to the combustion hydrogen gas remaining between the electromagnetic chamber of the engine 29 is compressed into the con control valve 25 and the combustion chamber of the 45 bustion chamber and is exploded to exhaust after the engine 29 completely exhausts out of the engine 29 by hydrogen gas stops being supplied from the MH tank 21 rotating the engine 29 idle prior to the real start of the to the engine 29 by means of a changing operation of the engine 29. electromagnetic control valve 25. Consequently, no Though the present embodiment is composed in such hydrogen gas remains in the engine 29 and its driving a way that the electromagnetic control valve 25 is SO circuit at the stop of the engine 29, so that the backfire changed over between the positions a and b by the due to the residual hydrogen gas can be avoided when controller 33 either to have the MH tank 21 and the the engine 29 starts again.

engine 29 communicate with each other or to have them In the present embodiment, the sparking operation is cut off from each other, it is also possible to have such finished after the engine 29 stops, but is can be modified, a formulation instead that the controller 33 has duty 55 for example, as described below;

control on the electromagnetic control valve 25 at the (1) The sparking number, after the electromagnetic start of the engine 29 to gradually increase the amount control valve 25 closes, of each cylinder of the engine of the hydrogen gas flowing into the combustion cham 29 is determined previously, and the sparking operation ber and to have the first explosion smoothly. does not continue after sparking is performed in the In the present embodiment, in order to supply the predetermined number.

hydrogen gas under the condition where the hydrogen (2) Once the engine 29 rotates in the predetermined gas is able to be ingited, the electromagnetic control number after the electromagnetic control valve 25 valve 25 waits for 0.5 seconds after the sparking of the closes, the sparking operation no longer continues. spark plug 31 to open. The electromagnetic control The Fourth Embodiment valve 25, however, can open either at sparking or just 65 before sparking as far as there is timing, at the start of A metal hydride tank (a MH tank) of the fourth en the engine 29, to make it sure to have the first explosion bodiment of the present invention is now described in after the hydrogen gas which has remained in the intake details hereinafter referring to FIGS. 8-10;

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As described in FIGS. 8 and 9, a MH tank 41 has a The low temperature water led through the low tem cylindrical tank body 42 previously containing the perature water introducing entrance 45 is firstly led to metal hydride M of fine grain which releases and/or one end of the group of pipes 44A at the top story and occludes hydrogen gas in reversible reactions accompa goes to the group of pipes 44B at the next lower story nied with heat exchanges. In the tank body 42 are pro after running zigzag along the pipe 43 of the group of vided pipes 43 which act as cooling intermedium circu pipes 44A at the top story. The low temperature water lating routes going through the inside of the tank body also runs zigzag along the pipe 43 of the group of pipes 42 and coming back to the hydrogen engine (not 44B and goes to the group of pipes 44C at the next shown) in order to heat or cool the metal hydride M. lower story. The low temperature water successively The pipes 43 contribute to the heat exchanging reaction O goes from the group of pipes 44C to the group of pipes by having low temperature water as cooling in 44G at the bottom story and then is led out of the tank temedium circulate therein when the metal hydride M body 42 via the connecting pipe 46 and the low temper occludes the hydrogen gas. When the metal hydride M ature water discharging exit 47. Accordingly, the low releases the hydrogen gas, the pipes 43 also contribute temperature water gradually moves from the upper to the heat exchanging reaction by having high temper 15 portion to the lower portion of the tank body 42 while ature water (for example, the cooling water which has moving in the longitudinal direction of the tank body 42 become of high temperature after cooling the hydrogen via the groups of pipes 44A-44G as shown as arrows in engine) as heating intermedium circulate therein. The FIG 9.

released hydrogen gas is supplied to the hydrogen en A reaction equation on the hydrogen gas (H2) occlu gine via a hydrogen gas pipe (not shown). sion of the metal hydride M can be shown as follows; In the present embodiment, the pipes 43 are provided in the tank body 42 in plural lines in parallel to extend in the longitudinal direction thereof and in plural stories vertically. In the above equation, Q means reaction heat. Namely, as shown in FIG. 9, groups of pipes 25 Accordingly, one of the important things on the hy 44A-44G made of plural lines of the pipes 43 are pro drogen gas occlusion is to release the reaction heat Q vided in the tank body 42 from the top portion to the out of the tank body 42 effectively, and removing the lower portion thereof in many stories. As shown in reaction heat Q from the tank body 42 outstandingly FIG. 10, in each of the groups of pipes 44A-44G, the promotes the hydrogen gas occlusion of the metal hy pipes 43 are connected with each other in zigzag shape 30 dride M. Another important thing is the relaxation of in its plan view. Moreover, as shown in FIG. 8, one end the expansion stress on the agglomerate metal hydride of each group of pipes 44A-44G in each story is succes M, which has not been reacted, at the hydrogen gas sively connected with the other end of each group occluding reaction.

44A-44G in such a way as the group of pipes 44A is In the present embodiment, the hydrogen gas occlu connected with the group of pipes 44B which is ar 35 sion by the metal hydride M, namely, the heat exchang ranged just below the group of pipes 44A, the group of ing reaction begins around the group of pipes 44A at the pipes 44B is connected with the group of pipes 44C, and top story which the low temperature water firstly the other groups such as the group of pipes 44D, the comes through and which the reaction heat is firstly group of pipes 44E, the group of pipes 44F, and the absorbed by, and gradually proceeds downward to an group of pipes 44G at the bottom story are successively area around the group of pipes 44G at the bottom story. connected with each other in a same manner in order to The cubical expansion of the metal hydride M accom have the low temperature water go from one group to panied with the hydrogen gas occlusion succesively another. proceeds from the upper portion to the lower portion of As shown in FIG. 8, a low temperature water intro the nonreacted agglomerate layer of the metal hydride ducing entrance 45 is provided at one end of the group M which is agglomerated in the tank body 42. In other of pipes 44A at the top story, and a low temperature words, the cubical expansion of the metal hydride M water discharging exit 47 is provided at one end of the begins at the upper portion of the tank body 42 where group of pipes 44G at the botton story via a connecting there is sufficient room for the expansion, and gradually pipe 46 extending upward. comes down to the lower portion. A number offins 48 of disc shape are provided at both 50 As a result, the hydrogen gas occlusion by the metal sides of each pipe 43 in the longitudinal direction hydride M can be performed with the room where the thereof along the length of the pipes 43. The fins 48 are nonreacted agglomerate metal hydride M escapes, in arranged having a predetermined interval between one other words, the hydrogen gas can be occluded while and another, and the metal hydride M can be filled in avoiding the generation of residual stress in the agglom the intervals. The fins 48, therefore, does not have any 55 erate layer of the nonreacted metal hydride M. The substantial influence on the capacity for containing the expansion stress on the nonreacted metal hydride M metal hydride M. agglomerated at the lower portion of the tank body 42 In case that the metal hydride M which has already is relaxed, therefore, the stress concentration on the released the hydrogen gas occludes the hydrogen gas tank body 42 and the pipes 43 or so can be relaxed. again, the hydrogen gas is led into the tank body 42 Moreover, in the present embodiment, the plural fins through the hydrogen gas introducing entrance (not 48 are provided at the pipes 43, so that the metal hy shown), and the low temperature water is also led into dride M is cooled effectively because of those fins 48 the tank body 42 through the low temperature water and that the efficiency of the heat exchange on the introducing entrance 45. At this time, the metal hydride metal hydride M is improved.

M, as shown in FIGS. 8 and 9, is agglomerated and is in 65 Furthermore, the movement of the metal hydride M a state of agglomerate layer leaving a little space at the can be restricted through the tank body 42 vibrates in top portion of the inside of the tank body 42 because of the longitudinal direction thereof, namely, in the direc having released the hydrogen gas. tion along which the pipe 43 extends. In other words,

Page 20

the movement of the metal hydride M in the longitudi The Fifth Embodiment nal direction of the tank body 42 is restricted and the metal hydride M can be prevented from being arranged The fifth embodiment of the present invention em unevenly in the tank body 42. bodied in a MH tank of a hydrogen engine for a forklift In the present embodiment as described above, the is now described in details hereinafter referring to expansion stress on the metal hydride M can be relaxed FIGS. 11 to 13;

only with the structure of the pipes 43 which directly As shown in FIG. 13, a MH tank 51 of the present contribute to the heat exchanging reactions of the metal embodiment is provided at a rear portion of a forklift 52. hydride M. Some other members for relaxing the expan O calAstank shown in FIG. 11, the MH tank 51 has a cylindri body 53 previously containing the metal hy sion stress, therefore, do not have to be provided in the dride M of tank body 42, unlike the alloy tank 81 of the related art based on thefine heat grain which releases the hydrogen gas exchanging reaction. A cooling water as shown in FIG. 16 of which the tank body 82 has the pipe 54, which goes through the tank body 53 and hierarchical shelf composed of the frame 83 and the which comes back to a hydrogen engine (not shown), as hydrogen filters 84. 15 a heating intermedium circulating route is provided to Consequently, the manufacturing steps of the MH heat the metal hydride M in the tank body 53. The tank 41 can be simplified, and the abatement of the cooling water pipe 54 is for having cooling water as space of the tank body 42 for containing the metal hy heating intermedium circulate therein. The cooling dride M can be prevented. water of high temperature which is discharged from the Comparing the MH tank 81 of the related art with the 20 hydrogen engine after cooling the hydrogen engine is MH tank 41 of the present embodiment, the manufac delivered to the tank body 53 and is used for the heat turing cost for the present embodiment is half as much exchanging reaction of the metal hydride M in the tank as that of the related art. As for the containing capacity body 53.

of the metal hydride M, the capacity of the metal hy In the present embodiment, the cooling water pipe 54 dride M of the present embodiment is 1.6 times larger 25 is provided extending along the length of the tank body than that of the related art. The MH tank 41 of the 53. As shown in FIG. 12, a number of fins 55 of disc present embodiment shows remarkable superiority over shape are provided at both sides, in the longitudinal the related art in terms of the manufacturing cost and direction, of the cooling water pipe 54 along the length the substantial capacity. of the cooling water pipe 54 as well as the fourth em 30 bodiment. Each fin 55 is arranged having a predeter

On the other hand, in order to release the hydrogen mined interval between one and another, and the metal gas out of the metal hydride M after the aforementioned hydride M is filled in the intervals. hydrogen gas occlusion is completed, the high tempera ture water goes through the pipes 43 and the heat of the loaded in present

In the parallel embodiment, the tank body 53 is with the crossing direction of the high temperature water is given to the metal hydride M 35 forklift 52 which moves hard in the crossing direction, as reaction heat. In this case, the released hydrogen gas therefore each fin 55 is arranged crossing the crossing is led out of the tank body 42 through a hydrogen gas direction of the forklift 52. d discharging exit (not shown). In the present embodi Moreover, the hydrogen gas which is released as a ment, a number of fins 48 are provided at the pipes 43, result of the heat exchanging reaction of the metal hy so that the heat exchange with the metal hydride M can dride M is supplied to the hydrogen engine via a hydro be done efficiently, and that the hydrogen gas can be gen gas pipe 56 led from the tank body 53. released effectively. Accordingly, when the cooling water of high tem The present embodiment can be modified as follows; perature discharged from the hydrogen engine goes (l) Though the group of pipes 44A-44G at each story through the cooling water pipe 54, the metal hydride M is provided zigzag in a plan view in the present embodi 45 in the tank body 53 is heated, and the hydrogen gas is ment, they can also be provided in a latticed shape in a released due to the heat exchanging reaction. At this plan view. time, each fin 55 functions to heat the metal hydride M (2) Though the pipes 43 at each story is provided as effectively, the efficiency of heat exchange on the metal the group of pipes 44A-44G running zigzag, they can 50 hydride M is improved.

also be a single pipe. Moreover, if the tank body 53 vibrates with its hard (3) Though the present embodiment is so composed movement in the longitudinal direction thereof, namely, that the group of pipes 44A-44G at each story is con in the crossing direction of the forklift 52 during the operation of the forklift 52, the movement of the metal nected with each other at their one ends to have the low hydride M is restricted because of each fin 55. In other temperature water run from the group of pipes 44A at 55 words, the top story to the group of pipes 44G at the bottom stricted the movement of the metal hydride M is re in the longitudinal direction of the tank body story successively, it can be composed in such a way 53, that the group of pipes 44A-44G at each story is pro beingandarranged the metal hydride M can be prevented from unevenly in the tank body 53.

vided independently and the circulation of the low temperature water is shifted successively, so that the lated art shown incomparing

The results of the MH tank 91 of the re

FIG. 17 with the MH tank 51 of the low temperature water runs through the group of pipes present embodiment are now referred to; The compari 44A at first and runs through the group of pipes 44G at son is made in terms of the uneven arrangement of the last. metal hydride M, namely, the differences of the layer (4) Though the MH tank 41 is used for a hydrogen levels of the metal hydride M between the right end and engine system in the present embodiment, it can be 65 the left end of each MH tank 91, 51, which is examined applied for all the apparatuses and devices, other than after both the MH tanks 91 and 51 are loaded on the the hydrogen engine system, which need the supply of forklifts 52 and have been used there for three months. hydrogen gas. The defference of the layer levels of the related art is

Page 21

20%. On the other hand, that of the present embodi for detecting the temperature of the heat transfer ment is 0%. There is no uneven arrangement of the medium delivered to the container and valve metal hydride M in the present embodiment. Conse means for controlling the amount of the heat trans quently, the MH tank 51 of the present embodiment has fer medium delivered to the heating means in re outstanding superiority over the MH tank 91 of the sponse to the temperature of the heat transfer me related art in terms of the uneven arrangement of the dium.

metal hydride M. 2. A hydrogen engine system according to claim 1, Moreover, the results of comparing the MH tank 91 wherein the heating means comprises:

of the related art with the MH tank 51 of the present a heat exchanger;

embodiment under the same conditions as above in O an exhaust pipe connected between the engine and terms of the heat transfer efficiency of the metal hydride the heat exchanger for delivering the exhaust gases M is now described; The heat transfer efficiency of the from the engine to the heat exchanger; and related art is lowered by 35%. On the other hand, that a circulation pipe system connected between the heat of the present embodiment does not change. Namely, exchanger and the container for circulating a heat the lowering of the heat transfer efficiency, in other 5 exchange medium heated by the exhaust gases in words, that of the heat exchange efficiency on the metal the exchanger so as to transfer heat to the con hydride M can be prevented because the uneven ar tainer.

rangement of the metal hydride M can be prevented in 3. A hydrogen engine system according to claim 2, the MH tank 51 of the present embodiment. In addition, wherein the valve means comprises a gas adjusting the efficient heating via the fins 55 can also prevent the 20 valve connected to the exhaust pipe. lowering of the heat exchange efficiency more effec 4. A hydrogen engine system according to claim 2, tively. wherein the circulation pipe system includes a bypass The present embodiment can be modified as follows; pipe for bypassing the container, and a valve disposed (1) Though the fins 55 are provided at the cooling water pipe 54 which extends along the length of the 25 therein for opening and closing the bypass pipe. 5. A hydrogen engine system according to claim 1, tank body 53 in the present embodiment, fins can also be wherein the heating means comprises: provided at a cooling water pipe which extends cross a heat exchanger;

ing the length of a tank body. an exhaust pipe connected between the engine and (2) Though the fins 55 of disc shape are provided in the heat exchanger for delivering the exhaust gases the present embodiment, fins of square shape, triangle 30 from the engine to the heat exchanger; and shape, sector shape and so on can also be provided. a circulation pipe system interconnecting the engine, (3) Though the cooling water of the hydrogen engine is used as heating intermedium in the present embodi the heat exchanger and the container for circulat ment, the exhaust gas of the hydrogen engine can be ing the coolant heated by the exhaust gases in the used as heat intermedium 35 heat exchanger so as to transfer heat to the con (4) Though the MH tank 51 is used for the hydrogen tainer.

engine of a forklift, the MH tank 51 can also be applied 6. A hydrogen engine system according to claim 1, for the hydrogen engine of others and for all the appara wherein the heating means has a circulation pipe con tuses and devices which need the supply of the hydro nected between the engine and the container directly. 7. A hydrogen engine system comprising:

gen gas. 40

As many apparently widely different embodiments of a container for accommodating a metal hydride this invention may be made without departing from the which generates hydrogen when the metal hydride spirit and scope thereof, it is to be understood that the is heated;

invention is not limited to the specific embodiments a hydrogen activated engine having a coolant inlet thereof except as defined in the appended claims. 45 and outlet, and input for hydrogen coupled to an What is claimed is: output of said container, and an exhaust gas outlet; 1. A hydrogen engine system comprising: cooling means provided with a fluid coolant and a container for accommodating a metal hydride coupled to said coolant inlet and outlet of the en which generates hydrogen when the metal hydride gine for circulating said coolant thereto; is heated; 50 heating means coupling at least one of said engine an engine activated by hydrogen supplied from the outlets in heat transfer relation to said container for container, the engine exhausting gases when oper supplying to said container a medium transporting ated; thermal energy for heating the metal hydride; cooling means for cooling the engine by supplying control means for controlling said heating means to coolant to the engine; 55 regulate the heating of the metal hydride and to heat transfer medium comprising at least one of the prevent the pressure in said container from increas exhaust gases and the coolant; ing excessively, said control means comprising a heating means connected with the container for heat temperature sensor connected to said heating ing the metal hydride, the heating means being means for detecting the temperature of said me arranged to recycle heat energy from the heat dium supplied to said container, and valve means transfer medium; and responsively coupled to said temperature sensor control means for controlling the heating means to and disposed between said heating means and said regulate the heating of the metal hydride and to at least one engine outlet for controlling the prevent the pressure in the container from increas amount of heat transferred from said engine to said ing excessively, the control means comprising a 65 heating means and thereby to said container. temperature sensor connected to the heating means

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UNITED STATES PATENT AND TRADEMARK OFFICE

CERTIFICATE OF CORRECTION

PATENT NO. : 5,092, 28 Page 1 of 2

NVENTOR(S) : Iwaki et al.

it is certified that error appears in the above-identified patent and that said Letters Patent is hereby corrected as shown below:

Column l, line 17:

"Acadamic" should read --Academic-line 20, after"container" insert --65--; line 55, " (Qwm-Qm)" should read -- (Qwm-Qmt Qm) -- line 62, "losed" should read --lost--.

Col. 2, line 62, "regulater" should read --regulator --. Col. 3, line 27, "forms" should read --form-- ; line 30, "rooms" should read -- chambers-- ; line 32, "circulate" should read -- circulating-- ; line 4l should not be a separate paragraph ; line 57, "be" should read -- is -- ; line 6l, "comprising" should read --complicated--.

Col. 7, line ll "idoling" should read --idling--; line l6, "method," should read --method--; lines l6 and l7, "embodiment," should read --embodiment--; line 2l, "method, of the present embodiment," should read --method of the present embodiment--; line 32, "idoling" should read --idling--; line 4l, "in stead" should read --instead--. Col. 8, line 23, "elector magnetic" should read --electromagnetic--; line 65, "enging" should read

Col. 10, line l, "off" should read -- of--.

Page 23

UNITED STATES PATENT AND TRADEMARK OFFICE

CERTIFICATE OF CORRECTION

NVENTOR (S) : Iwaki et al. It is certified that error appears in the above-identified patent and that said Letters Patent is hereby corrected as shown below:

"defference" should read -- difference--. Col. 16, line 45, "and" should read --an--. Signed and Sealed this

Thirty-first Day of August, 1993

BRUCE LEHMAN

Attesting Officer Commissioner of Patents and Trademarks