Method and device for fuel proportioning in a gas-powered combustion engine

Page 1 — bibliographic record

Page 2

Drawing sheet — no readable text.

Page 3

Drawing sheet — no readable text.

Page 4

METHOD AND DEVICE FOR FUEL possible in a gas-powered combustion engine in varying PROPORTIONING IN A GAS-POWERED external conditions. Further objects are to maintain good COMBUSTION ENGINE reliability of a mechanical gas mixer and achieve at mod BACKGROUND OF THE INVENTION erate cost Stable emission and torque levels. The invention relates to a method for fuel proportioning a method These objects are achieved according to the invention by in a gas-powered combustion engine. It also relates to a tion engineof fuel which proportioning for a gas powered combus includes: mixing gas after reduction device for Such fuel pro portioning. thereof with air to form a gas/air mixture and Supplying the Gas intended for driving a gas engine is usually Stored at gas/air mixture to the engine; monitoring a parameter in the high pressure. After pressure reduction in one or more engine exhaust which is related to the proportion of air and Stages, the as is mixed with air in correct proportions for gas in the mixture, and when the value of the parameter good combustion. A larger or Smaller quantity of gas and air deviates from a Set-value, if at essentially the same time the is Supplied, depending on the load. engine is operating in a predetermined situation, adjusting Mixing of gas and air usually takes place in a mechanical the value of the parameter back to its Set-value by adjusting type of mixer which has to be set for the particular quality 15 the pressure level brought about by the pressure reduction. of gas by applying a manual basic Setting for maintaining the According to an advantageous embodiment of the invention intended ratio between gas and air during load variation. it is appropriate to use the air/fuel ratio as the parameter When Steady conditions prevail, the desired good combus monitored in the engine's exhaust gases and to carry out tion result is achieved, but if the gas proportion changes, e.g. adjustment at full load and within a limited engine Speed because of pressure change, gas quality change or any other range. Effecting adjustment in this manner makes it possible reason, an adjustment is required to restore the correct to limit the need for adjustment so that it need only be proportions of gas and air and hence achieve the intended effected relatively infrequently. Adjustment being also car good combustion. A need for adjustment of this kind may ried out automatically by means of Suitable equipment arise, for example, from refuelling. There have also been achieves good operating results.

found to be relatively large differences in the quality of gas 25 A device proposed according to the invention for fuel fuel available in different geographical areas. This means proportioning in a gas-powered combustion engine includes: that the manufacture of gas engines has to include individual a pressure regulator for reducing the pressure of gas Supplied adaptation of each engine according to the market or geo graphical area for which it is intended. The way gas engines thereto, a mixer arranged after the pressure regulator for receiving the reduced pressure gas from the pressure regu are often used means that they are always refuelled from the

Same filling Stations. In Such cases it is Sufficient, at least for lator

and mixing the reduced pressure gas with air to form gas/air mixture, an exhaust Sensor arranged in the outlet of a certain time, to abide by the manufacturer's original the engine;

Setting, but the fact that without adjustment the engine resetting thea proportion control unit connected to the exhaust Sensor for cannot be used in other geographical areas or use fuel from of an output signal from of the gas/air mixture as a function other fuel filling stations does of course limit the possibili 35 operating Sensor connected toexhaust the the

Sensor; and at least one control unit for indicating ties of using Such an engine in, for example, a vehicle the operating State of the engine. The control unit is con intended to travel considerable distances.

nected to an actuator coupled to the pressure regulator and

From the operating point of View it would be a great advantage if adjustment could be effected automatically. isoutput arranged to activate the actuator when the value of the signal from the exhaust Sensor deviates from a

This would not only mean that any careleSSneSS or forget 40 predetermined Set-value, if at essentially the same time the fulness on the occasion of refuelling need not cause bad operating Sensor indicates that a predetermined operating combustion but also that a difficult operation could be Situation prevails, to adjust the pressure level of the reduced obviated. It would thus be easier for gas-powered vehicles to preSSure gas to reset the output signal from the exhaust use fuel from different filling Stations, thereby facilitating Sensor to the predetermined Set-value thereof. Such a device lengthy journeys. 45 makes it possible to use a conventional mechanical gas

Like a diesel engine, a gas-powered combustion engine mixer, with the latters accompanying advantages. usually operates with exceSS air, i.e. with an air/fuel ratio Moreover, only relatively infrequently does the device pro greater than 1.0. This means that the oxygen content of the posed according to the invention need to come into action. exhaust gases cannot be measured by means of the conven The exhaust Sensor used is advantageously a 2 probe for tional type of 2 probe which is usually employed for 50 measuring gasoline engines to aim at a value of about 1.0, Since what advantages )ofvalues the greater than 1.0. Further features and invention are indicated by the following is required is a different type of 2 probe which can monitor detailed description and patent claims. higher values. AS Such a probes have now reached the Other features and advantages of the present invention market, various designs have been proposed whereby con will become apparent from the following description of the tinuous adaptation and correction of the air/fuel ratio takes invention which refers to the accompanying

drawings.

place in the actual mixer on the basis of Signals from the 2.

SCSO. BRIEF DESCRIPTION OF THE DRAWINGS Also known is the use of electronically controlled gas injection whereby a control unit calculates and proportions of Thean invention is explained in more detail below by means embodiment depicted in the drawings, in which:

the required gas quantity on the basis of various operating 60

FIG. 1 shows schematically a device implemented data.

according to the invention for fuel proportioning in a gas

A disadvantage of these Solutions is that they are rela powered tively Sensitive and require a great deal of maintenance. combustion engine,

FIG.2 shows an end view of a settable pressure controller

SUMMARY OF THE INVENTION 65 for the device in FIG. 1, and

One object of the invention is to use Simple means to FIG. 3 shows a section taken along with the line III-III make Simple and reliable and yet precise fuel proportioning in FIG. 2.

Page 5

DETAILED DESCRIPTION OF THE In normal Steady operating conditions the mixer 5 brings PREFERRED EMBODIMENTS about desired proportions of air and gas So that the engine A device 1 implemented according to the invention for can be operated at a predetermined air/fuel ratio which is fuel proportioning includes a first gas line 2 via which gas controlled and monitored by means of the exhaust sensor 10. at a certain pressure is led from a gas Source (not depicted Changes in ambient temperature and in gas quality, which in detail) in the form of a gas tank into a gas regulator 3 for may for example arise from refuelling, may cause a change preSSure reduction. From the gas regulator 3 the gas then in the value. Wear in the mixer 5 may also possibly alter proceeds at reduced pressure via another line 4 to a mixer 5 the value, thereby affecting the engine's emission level in which the incoming gas is mixed with air which is and torque. According to the invention, it is possible, while Supplied via a third line 6. The resulting proportions of air the engine continues to operate, for the outlet pressure from and gas are Such that the air/gas ratio 2 has a value exceeding the gas regulator 3 to be automatically adjusted as necessary 1.0, i.e. a lean mixture. From the mixer 5 the mixture of gas for monitoring and correcting a value change. This is and air is led via a line 7 to a combustion engine 8 in which achieved automatically by the control unit 11 activating the the mixture is burnt before leaving the engine 8 via an actuator for a long enough time to make the control device exhaust line 9 in order gradually to be led out, possibly via 15 17 reset the pressure regulator to a preSSure which results in a catalyst, to the Surrounding atmosphere. In the exhaust line the desired a value represented by a predetermined output 9 there is close to the engine an exhaust sensor 10 to detect the value of a parameter of the exhaust gases, here a 2 probe Voltage from the probe 10. Gas pressure adjustment is for detecting the value or oxygen content of the exhaust advantageously carried out according to the invention when gases. In this example the combustion engine takes the form the engine is operating at full load, which is indicated by the of a piston type of engine intended for gas operation and is Sensor 14 on the throttle Shaft and, within a certain engine intended to be used as the drive engine in a vehicle, e.g. a Speed range, indirectly by the Sensor 18. Adjustment at full heavy-duty bus. load will result in correct resetting in the worst operating A control unit 11 is connected via a line 12 to the exhaust Situation, which is when correct adjustment is most critical. sensor 10 and via a line 13 to an operating sensor 14 for It is also possible to use a differently defined operating detecting the operating conditions in which the engine 8 is 25 Situation.

operating. The operating Sensor 14 is mounted on the mixer After adjustment has been effected and the desired Set 5 and is arranged to detect the rotational position of the value for 2 has again been reached, the engine is run latter's throttle shaft (not depicted). The operating sensor 14 conventionally with the pressure regulator Setting constant can thus detect whether the engine 8 is, for example, running and unchanged until a further adjustment becomes at full load or not. In alterative embodiments other ways of necessary, e.g. because of a change of gas quality arising detecting whether the engine is running at full load may be from refuelling. Adjustment thus takes place relatively infre used. The control unit 11 controls via a line 15 an actuator quently and normally required changes in fuel quantity are 16 which via a control device 17 can act upon the pressure catered for by the driver by means of the mechanical mixer regulator 3 in order to reset the latter's outlet pressure. 5. The fact that adjustment takes place during operation In addition to the operating Sensor 14 mounted on the 35 ensures good combustion and a stable emission level. mixer 5 to detect the engine's operating State, there is also Although the present invention has been described in a sensor 18 which is mounted directly on the engine 8 and relation to particular embodiments thereof, many other is connected via a line 19 to the control unit 11. This sensor 18 is a Speed Sensor which detects the Speed of the engine. variations apparent to and modifications and other uses will become those skilled in the art. It is preferred, therefore,

Together with the Sensor 14, it thus detects the engine's 40 that the present invention be limited not by the specific prevailing operating situation. disclosure herein, but only by the appended claims. The mixer 5 takes the form of a mechanical type of mixer, What is claimed is:

e.g. of IMPCO(E) make type 200D, intended for use in 1. Method for fuel proportioning in a gas-powered com engines. The pressure regulator 3 takes the form of a bustion engine, which comprises: preSSure regulator provided with Setting facilities, e.g. of 45 Supplying gas to a pressure reduction device to reduce the IMPCO(E) make, type T-PEV-1. Such a pressure regulator 3 preSSure of the gas, is depicted in more detail in FIGS. 2 and 3. This pressure mixing the gas after pressure reduction with air to form a regulator has a housing 20 into which gas at a certain gas/air mixture;

preSSure is Supplied via an inlet 21 and out of which the gas flows at a lower pressure via an outlet 22. An adjusting 50 Supplying the gas/air mixture to the engine; Spring 23 for adjusting the ratio between the inlet and outlet monitoring the value of a parameter in an exhaust gas of preSSures is arranged in the housing 20. The housing 20 is the engine, which parameter is related to the proportion usually provided with an adjusting Screw which can be acted of air and gas in the gas/air mixture; upon manually to alter the tension of the adjusting Spring 23. monitoring the engine to determine when a predetermined In the embodiment depicted here, however, the adjusting 55 operating situation of the engine is occurring, and Screw is replaced by the actuator 16 and the control device when the monitored value of the parameter deviates from 17 whereby the actuator 16 can move the control device 17 a predetermined Set-value, if at essentially the same in either direction represented by the double-headed arrow time the engine is monitored to be operating in a 24 to alter the tension in the adjusting Spring 23 and hence predetermined operating situation, adjusting the pres alter the outlet pressure. The actuator 16 may advanta 60 Sure level brought about by the pressure reduction to geously be mounted on the pressure regulator 3 but may of return the parameter to its Set-value, and course also be fastened elsewhere, e.g. directly to the engine, not adjusting the pressure level based on deviation of the provided that its distance from the housing 20 is well value of the measured parameter from the Set value defined. when the engine is monitored to not be operating in the Instead of the mixer and pressure regulator indicated 65 predetermined operating situation. above it is of course possible to use other similar types of 2. Method according to claim 1, wherein a lambda ().) mixer and pressure regulators. value of the exhaust gas is used as the monitored parameter.

Page 6

S 6 3. Method according to claim 1, wherein the predeter 7. Device according to claim 5, wherein the operating mined operating situation for adjustment is when the engine Sensor is a Sensor for indicating a predetermined operating operates at full load. situation in the form of full load. 4. Method according to claim 2, wherein the predeter 8. Device according to claim 5, wherein the operating mined operating situation for adjustment is when the engine Sensor is a Sensor which is coupled to a throttle shaft of the operates at full load. engine and is arranged to detect a full load position. 5. Device for fuel proportioning in a gas-powered com 9. Device according to claim 5, wherein the operating bustion engine for vehicles comprising: Sensor is a Speed Sensor arranged on the engine. a pressure regulator for reducing pressure of gas Supplied 10. Device for fuel proportioning in a gas-powered com thereto:

bustion engine for vehicles, comprising:

a preSSure regulator for reducing pressure of gas Supplied a mixer arranged after the pressure regulator for receiving thereto;

the reduced pressure gas from the pressure regulator, a mixer arranged after the pressure regulator for receiving mixing the reduced preSSure gas with air to form a the reduced pressure gas from the pressure regulator, gas/air mixture and Supplying the gas/air mixture to the 15 mixing the reduced preSSure gas with air to form a engine; gas/air mixture and Supplying the gas/air mixture to the an exhaust Sensor arranged in an exhaust of the engine to engine;

measure a parameter of an exhaust gas, an exhaust Sensor arranged in an exhaust of the engine to a control unit connected to the exhaust Sensor for resetting measure a parameter of an exhaust gas, the proportion of the gas/air mixture as a function of the a control unit connected to the exhaust Sensor for resetting measured parameter; and the proportion of the gas/air mixture as a function of the measured parameter; and at least one operating Sensor connected to the control unit at least one operating Sensor connected to the control unit for Sensing the operating situation of the engine; for Sensing the operating situation of the engine, an actuator connected to the control unit, the actuator an actuator connected to the control unit, the actuator being coupled to the pressure regulator the control unit 25 being coupled to the pressure regulator, the control unit being operable to activate the actuator when the value being operable to activate the actuator when the value of the measured parameter of an exhaust gas measured of the measured parameter of an exhaust gas measured by the exhaust Sensor deviates from a predetermined by the exhaust Sensor deviates from a predetermined Set-value, if at essentially the same time the operating Set-value, if at essentially the same time the operating Sensor Senses that a predetermined operating Situation Sensor Senses that a predetermined operating Situation of the engine prevails, to adjust the pressure level of the of the engine prevails to adjust the pressure level of the reduced pressure gas to reset the value of the parameter reduced pressure gas to reset the value of the parameter to the predetermined set-value thereof; and to the predetermined set-value thereof; and the control unit deactivates the actuator when the Set the control unit does not activate the actuator when the

value is reached. operating Sensor does not Sense the engine is operating 6. Device according to claim 5, wherein the measured in the predetermined operating Situation. parameter is lambda (2) and the exhaust sensor is a 2 probe for measuring ) values greater than 1.0. k k k k k