JP4787665B2 - engine - Google Patents

Description

The present invention includes a combustion chamber that compresses and burns an air-fuel mixture, and a three-way catalyst unit that processes exhaust gas discharged from the combustion chamber in a three-way catalyst system,
The present invention relates to an engine configured to cause stoichiometric combustion of the air-fuel mixture, and to treat exhaust gas discharged from the combustion chamber during the stoichiometric combustion through the three-way catalyst unit.

As described above, the air-fuel mixture is formed in the intake passage or in the intake system of the combustion chamber in the intake stroke or the compression stroke, and the mixture is combusted in the combustion chamber in a stoichiometric manner (that is, at the stoichiometric air-fuel ratio). In the engine, during the stoichiometric combustion, exhaust gas having a low oxygen concentration, that is, exhaust gas in which the air-fuel ratio is maintained at the stoichiometric air-fuel ratio is discharged from the combustion chamber.
The exhaust gas in which the air-fuel ratio is maintained at the stoichiometric air-fuel ratio is passed through the three-way catalyst unit and processed by the three-way catalyst method, and the exhaust gas is combined with NOx (nitrogen oxide) contained in the exhaust gas. CO (carbon monoxide) and HC (hydrocarbon) contained can be removed.
In this three-way catalyst method, the stoichiometric air-fuel ratio of the exhaust gas is used to balance the oxidizing component and the reducing component contained in the exhaust gas, and then a catalyst containing platinum or rhodium (three-way catalyst). ) In order to simultaneously remove NOx, CO, and HC emissions contained in the exhaust gas, and the exhaust gas in a state where the reducing component and the oxidizing component are not balanced, for example, excess air Such exhaust gas with a high air-fuel ratio cannot be treated by such a three-way catalyst method.

  In addition, an engine provided with a three-way catalyst unit in this manner maintains the air-fuel ratio of the exhaust gas at the stoichiometric air-fuel ratio, and the exhaust gas is always processed by the three-way catalyst unit. A rated load range in which the air-fuel ratio of the air-fuel mixture taken into the combustion chamber is always maintained at the stoichiometric air-fuel ratio and the amount of fuel supplied to the combustion chamber per cycle is set within a relatively high rated load range. Of course, the stoichiometric combustion is also performed in a partial load region in which the fuel supply amount is set within a partial load range lower than the rated supply amount. However, this engine has a problem in that the pumping loss increases and the efficiency decreases by reducing the opening of the throttle valve in the partial load region.

  Therefore, as an engine capable of reducing the NOx emission amount while suppressing an increase in pumping loss, the throttle valve is configured by increasing the EGR amount to the combustion chamber in the partial load region where the fuel supply amount is reduced within the partial load range. By reducing the amount of air supplied to the combustion chamber without reducing the degree of opening, the air-fuel mixture containing a large amount of exhaust gas is stoichiometrically combusted in the combustion chamber, and the exhausted exhaust gas with the stoichiometric air-fuel ratio passes through the three-way catalyst section. And an engine that can always remove NOx contained in the exhaust gas satisfactorily (see, for example, Patent Document 1).

  Another engine that can reduce NOx emissions while suppressing an increase in pumping loss is combustion without reducing the throttle valve opening in the partial load range where the fuel supply amount is reduced within the partial load range. By maintaining the air supply amount to the chamber relatively high, the air-fuel mixture is burned lean (that is, at a high air-fuel ratio in which the fuel is leaner than the stoichiometric air-fuel ratio) in the combustion chamber, and the combustion chamber in the expansion stroke or exhaust stroke By supplying fuel to the exhaust gas, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is set to the stoichiometric air-fuel ratio, and the exhaust gas with the stoichiometric air-fuel ratio is passed through the three-way catalyst unit, so that NOx contained in the exhaust gas is always An engine that can be removed satisfactorily is known (see, for example, Patent Document 2).

  In addition, when the lean combustion is performed in the partial load region as described above and exhaust gas with a high air-fuel ratio is discharged from the combustion chamber, the ignition timing is retarded and the EGR amount is increased without using the three-way catalyst unit. For example, a technique for reducing the NOx emission amount is known (see, for example, Patent Document 3).

JP 2004-144052 A JP 11-294229 A JP 2005-226491 A

However, as in the engines described in Patent Documents 1 and 2, exhaust gas with a stoichiometric air-fuel ratio is always discharged from the combustion chamber while suppressing an increase in pumping loss in the partial load region, and the exhaust gas is transferred to the three-way catalyst unit. In an engine configured to pass and process, NOx contained in the exhaust gas can always be satisfactorily removed by the three-way catalyst unit, but further efficiency improvement may be required particularly in a partial load region.
In particular, when the engine is used as a drive source of the heat pump system, the engine load greatly fluctuates according to the fluctuation of the air conditioning load of the heat pump system. It is desired to improve the coefficient of performance of the heat pump system.

  Further, in such an engine-driven heat pump system, in 12 modes assuming load fluctuations, it is stipulated that the average emission amount of NOx be suppressed to a specified amount or less. It is desirable to improve the efficiency of the maximum.

  The present invention has been made in view of the above-described problems, and its object is to perform stoichiometric combustion of an air-fuel mixture and distribute exhaust gas discharged from a combustion chamber during the stoichiometric combustion through a three-way catalyst unit. In the engine configured as described above, it is possible to achieve the maximum efficiency while appropriately reducing the average NOx emission amount from the high load range to the partial load range. For example, such an engine is driven by a heat pump system. It is in providing a technique that can improve the coefficient of performance satisfactorily when used as a source.

In order to achieve the above object, an engine according to the present invention includes a combustion chamber that compresses and burns an air-fuel mixture, and exhausts a three-way catalyst unit that processes exhaust gas discharged from the combustion chamber in a three-way catalyst system. Prepare for the road
An engine configured to perform stoichiometric combustion of the air-fuel mixture and distribute exhaust gas discharged from the combustion chamber during the stoichiometric combustion through the three-way catalyst unit;
As an exhaust gas bypass means that can exhaust the exhaust gas discharged from the combustion chamber by bypassing the three-way catalyst part, as an empty gas path that connects the inlet side and the outlet side of the three-way catalyst part of the exhaust path And a switching valve for switching a supply destination of the exhaust gas discharged from the combustion chamber between the three-way catalyst unit and the bypass passage,
The rated load operation in which the stoichiometric combustion is performed in the rated load range where the fuel supply amount per cycle is set within the rated load range, and the exhaust gas supply destination is set to the three-way catalyst unit by the exhaust gas bypass means . And the air-fuel mixture is lean burned in a partial load range where the fuel supply amount is set within a partial load range lower than the rated load range, and the exhaust gas supply means is used as the bypass path in the exhaust gas bypass means . Comprising a control means for performing load control in a form of executing the first partial load operation to be an operating state to perform,
Exhaust gas air-fuel ratio setting means capable of setting the air-fuel ratio of the exhaust gas discharged from the combustion chamber to the stoichiometric air-fuel ratio in a state where the fuel supply amount is set within the partial load range;
In the partial load region, the control means sets the exhaust gas air-fuel ratio setting means in a non-operating state to perform the first partial load operation; sets the exhaust gas air-fuel ratio setting means to an operating state; It is configured to perform a partial load operation switching operation for switching between a state in which the second partial load operation to be in an inoperative state is performed,
The control means executes the first partial load operation in an intermediate load range in which the fuel supply amount is set in an intermediate load range which is a higher side in the partial load range, and the fuel supply amount is set in the partial load range. The partial load operation switching operation is performed in a form in which the second partial load operation is executed in a low load region set within a low load range which is the lower side of the above.

According to the first characteristic configuration, the exhaust gas bypass means exhausts the bypass path as an empty gas path that connects the inlet side and the outlet side of the three-way catalyst portion of the exhaust path, and the combustion chamber. A switching valve for switching the supply destination of the exhaust gas between the three-way catalyst unit and the bypass path is provided, and in the load control of the control means, by controlling the operation of the exhaust gas bypass means, from the rated load range By improving the efficiency in the partial load range while appropriately reducing the average emission amount of NOx over the partial load range to, for example, a predetermined amount or less, the maximum efficiency can be improved. The coefficient of performance can be improved satisfactorily when used as a drive source for a heat pump system.

That is, in the load control of the control means, the rated load operation is executed in the rated load region, the air-fuel mixture is stoichiometrically burned in the combustion chamber, and the exhaust gas having the stoichiometric air-fuel ratio is discharged from the combustion chamber. In such stoichiometric combustion, NOx is easily generated, so that the exhaust gas bypass means is deactivated, and the stoichiometric air-fuel ratio exhaust gas discharged from the combustion chamber is circulated to the three-way catalyst section. Therefore, NOx contained in the exhaust gas can be removed well.
On the other hand, in the load control of the control means, in the partial load region, the first partial load operation is executed, the air-fuel mixture is lean burned in the combustion chamber, and high air-fuel ratio exhaust gas rich in oxygen is emitted from the combustion chamber. Discharged. In such lean combustion, since NOx is difficult to be generated, the exhaust gas bypass means is activated, and exhaust gas with a high air-fuel ratio that is discharged from the combustion chamber and cannot be processed by the three-way catalyst method is converted into the three-way. Since the catalyst part is bypassed and discharged, pressure loss when exhaust gas is discharged can be reduced and efficiency can be improved.

That is, in the rated load range, the exhaust gas is processed by the three-way catalyst unit by the rated load operation, while in the partial load range, the air-fuel mixture is lean burned by the first partial load operation, so that the partial load range from the rated load range. The average emission amount of NOx over the range can be reduced to a predetermined amount or less, for example.
Furthermore, in the partial load region, lean combustion is performed by the first partial load operation to reduce the fuel supply amount. For example, it is possible to reduce the output without having to reduce the opening of the throttle valve, thereby increasing the pumping loss. Furthermore, since the exhaust gas is discharged by bypassing the three-way catalyst unit, the pressure loss during the exhaust gas discharge can be reduced, and as a result, the average exhaust amount of NOx is appropriately reduced. , Maximum efficiency can be improved.

Note that the lean combustion includes so-called stratified combustion in which a rich mixture existing in the vicinity of the spark plug in the combustion chamber is spark-ignited and a lean mixture existing in the surroundings is combusted, or premixed gas is burned at a high compression ratio. Known lean combustion such as premixed compression ignition combustion that compresses and performs self-ignition combustion can be employed.
When stoichiometric combustion is performed by spark ignition in the rated load operation and premixed compression ignition combustion is performed in the first partial load operation, the compression ratio at the rated load operation is changed to the compression ratio at the first partial load operation. As a method for reducing the compression ratio, for example, a known method such as increasing the advance amount with respect to the bottom dead center of the intake valve closing timing of the intake stroke may be employed. it can.
Further, according to the first characteristic configuration, the control means can perform the second partial load operation different from the first partial load operation by performing the partial load operation switching operation. Then, by executing the second partial load operation, the exhaust gas air-fuel ratio setting means is in an operating state while the fuel supply amount is within a relatively low partial load range as in the first partial load operation. Then, the air-fuel ratio of the exhaust gas discharged from the combustion chamber is set to the stoichiometric air-fuel ratio, and further, the exhaust gas bypass means is deactivated, and the exhaust gas of the stoichiometric air-fuel ratio is sent to the three-way catalyst unit. Since it is distributed, NOx contained in the exhaust gas is removed well.
Therefore, the control means can switch between the first partial load operation capable of improving the efficiency and the second partial load operation capable of satisfactorily removing NOx by performing the partial load switching operation in the partial load region.
Further, according to the first characteristic configuration, in addition to performing the rated load operation in the rated load region, the exhaust gas in the low load region on the lower side of the partial load region is the same as in the rated load operation. By executing the second partial load operation in which the three-way catalyst part removes NOx well, the average NOx emission amount from the rated load range to the low load range can be further reduced.
Further, since the average emission amount of NOx can be further reduced in this way, the exhaust gas bypass means is set in the three-load operation state in the middle load region higher than the low load region in the partial load region. When performing the first partial load operation that exhausts exhaust gas by bypassing the catalyst section, if you want to reduce NOx emissions, such as retarding the ignition timing or increasing the EGR amount, set a reduction target for NOx emissions. As a result, the retard width of the ignition timing and the increase width of the EGR amount can be minimized to further improve the efficiency.
In general, the operation time in the rated load region and the low load region is relatively shorter than the operation time in the medium load region. Therefore, in the rated load range and the low load range where the operation time is relatively short, the rated load operation and the second partial load operation in which the exhaust gas bypass means is deactivated are executed, and the exhaust gas of the stoichiometric air-fuel ratio is reduced. The first partial load operation in which the exhaust gas bypass means is activated in the middle load range where the NOx is removed well by the three-way catalyst unit and the average NOx emission amount is appropriately reduced while the operation time is relatively long. This can be done to maximize efficiency.

According to a second characteristic configuration of the engine according to the present invention, in addition to the first characteristic configuration, the exhaust gas air-fuel ratio setting means increases the EGR amount to determine the air-fuel ratio of the exhaust gas discharged from the combustion chamber. The point is that it is configured to be set to.

According to the second characteristic configuration, the exhaust gas air-fuel ratio setting means reduces the amount of fuel supplied to the combustion chamber per cycle in the partial load range within a relatively low partial load range. With a relatively simple configuration of increasing the amount, the amount of air supplied to the combustion chamber per cycle can be reduced, and a stoichiometric air-fuel mixture containing a large amount of exhaust gas can be supplied to the combustion chamber. The stoichiometric air-fuel ratio exhaust gas can be discharged from the combustion chamber.

An embodiment of an engine according to the present invention will be described based on the drawings.
An engine 100 shown in FIG. 1 includes a combustion chamber 1 that compresses and burns an air-fuel mixture M, and a three-way catalyst unit 10 that processes exhaust gas discharged from the combustion chamber 1 in a three-way catalyst system. 1, the air-fuel mixture M is stoichiometrically combusted, and the exhaust gas E discharged from the combustion chamber 1 during the stoichiometric combustion is circulated to the three-way catalyst unit 10 for processing. Explained.

  The engine 100 reciprocates the piston in the cylinder and opens / closes the intake valve 2 and the exhaust valve 4 to perform various strokes of intake, compression, combustion / expansion, and exhaust in the combustion chamber 1. Is output as a rotational motion of the crankshaft by a connecting rod, and this configuration is the same as a normal four-stroke engine.

  The intake passage 3 connected to the combustion chamber 1 via the intake valve 2 is provided with a mixer 12 having a venturi structure in which the diameter of the intake passage 3 is reduced. The mixer 12 flows through the intake passage 8. The air A that flows through the venturi structure at a high speed generates a pressure drop. By using this pressure drop, the fuel G, which is the gas fuel, the city gas (13A), flows through the intake passage 3. A is supplied to A to form an air-fuel mixture M in the intake passage 3.

  Further, a fuel control valve 13 capable of adjusting the fuel supply amount to the mixer 12 is provided in the fuel supply path 14 leading to the mixer 12.

  The control means 31 on which an engine control unit (hereinafter referred to as ECU) 30 comprising a computer functions controls the fuel control valve 13 in accordance with the crank angle, so that one intake stroke, that is, one cycle. The fuel supply amount to the pertinent combustion chamber 1 can be set.

  The exhaust passage 5 connected to the combustion chamber 1 via the exhaust valve 4 is provided with a three-way catalyst unit 10 for treating the exhaust gas E discharged from the combustion chamber 1 by a three-way catalyst method. Further, the three-way catalyst unit 10 causes the exhaust gas E having a stoichiometric air-fuel ratio, that is, the exhaust gas E in a state where the oxidizing component and the reducing component contained are balanced, to flow through the three-way catalyst, and to the exhaust gas E. It is configured to simultaneously remove NOx, CO, and HC emissions contained therein, and a known three-way catalyst such as a catalyst containing platinum or rhodium can be used as the three-way catalyst.

  Further, the exhaust passage 5 is connected to a bypass passage 6 for communicating the inlet side and the outlet side of the three-way catalyst unit 10 and the supply destination of the exhaust gas E discharged from the combustion chamber 1 in the exhaust passage 5 is three-way. A switching valve 7 for switching between the catalyst unit 10 side and the bypass path 6 side is provided.

  Then, the exhaust gas bypass means 32 in which the ECU 30 functions has the three-way exhaust gas E as the three-way catalyst unit 10 in an attitude (the attitude indicated by the one-dot chain line in FIG. 1). From the state in which the exhaust gas is circulated through the catalyst unit 10 and discharged, the exhaust valve E is circulated through the bypass passage 6 so that the switching valve 7 communicates with the exhaust valve 4 side and the bypass passage 6 (the posture indicated by the solid line in FIG. 1). The exhaust gas E discharged from the combustion chamber 1 is configured as means capable of being discharged by bypassing the three-way catalyst unit 10 in the form of switching to the discharge state.

  Further, the engine 100 is provided with an EGR path 20 that communicates the space between the exhaust valve 1 and the switching valve 7 in the exhaust path 5 and the space between the mixer 12 and the intake valve 2 in the intake path 3. Therefore, so-called EGR can be performed in which a part of the exhaust gas E discharged to the exhaust passage 5 is supplied to the combustion chamber 1 through the EGR passage 20 and the intake passage 3. Further, an EGR control valve 21 is provided in the EGR passage 20, and the supply amount of the exhaust gas E to the combustion chamber 1, that is, the EGR amount can be adjusted by adjusting the opening degree of the EGR control valve 21.

  An oxygen sensor 23 that detects the oxygen concentration of the exhaust gas E discharged from the combustion chamber 1 is provided in the space between the exhaust valve 4 and the switching valve 7 in the exhaust passage 5.

  The exhaust gas air-fuel ratio setting means 33 that the ECU 30 functions is a low oxygen concentration in which the oxygen concentration of the exhaust gas E detected by the oxygen sensor 23 is substantially zero from the state in which the EGR amount is reduced by reducing the opening of the EGR control valve 21. By increasing the EGR amount by increasing the opening of the EGR control valve 21 until the concentration is reached, the fuel supply amount per cycle will be described later regardless of the air-fuel ratio of the air-fuel mixture M sucked into the combustion chamber 1. Even when it is set within a relatively low partial load range, the air-fuel ratio of the exhaust gas E can be set to the stoichiometric air-fuel ratio.

  Further, the control means 31 is configured to perform load control in such a manner that the output is changed by changing the fuel supply amount per cycle by adjusting the opening of the fuel control valve 13, and adjusting the opening of the throttle valve. Thus, an increase in pumping loss due to the throttle valve opening being reduced in the partial load region is suppressed as compared with an engine that performs load control in a manner that changes the output by changing the intake amount into the combustion chamber.

  Further, as shown in FIG. 2, the control means 31 performs a rated load operation in which the air-fuel mixture M is stoichiometrically burned in the combustion chamber 1 in the rated load region, and the air-fuel mixture M is generated in the combustion chamber 1 in the partial load region. In the form of performing the first partial load operation in which the lean combustion is performed, the operation state is switched.

  That is, the control means 31 performs the rated load operation in a rated load range where the fuel supply amount per cycle is set within a relatively high rated load range, and the mixture M of the theoretical air-fuel ratio is always generated in the mixer 12. The fuel control valve 13 is controlled so that the stoichiometric air-fuel mixture M is formed and supplied to the combustion chamber 1. Then, the stoichiometric combustion is performed in such a manner that the stoichiometric air-fuel ratio mixture M is compressed in the combustion chamber 1 and spark ignition combustion is performed by the spark plug 15 in a state where the EGR amount is set to be substantially low. During this rated load operation, by performing such stoichiometric combustion, the stoichiometric air-fuel ratio exhaust gas E, that is, the exhaust gas E having substantially zero oxygen concentration, is discharged from the combustion chamber 1 to the exhaust passage 5. .

  During the rated load operation, the control means 31 causes the exhaust gas bypass means 32 described above to be in an inoperative state, and causes the stoichiometric air-fuel ratio exhaust gas E to flow through the three-way catalyst unit 10 to be discharged. The NOx contained is well removed by the three-way catalyst method.

  On the other hand, the control means 31 performs the first partial load operation in the partial load region where the fuel supply amount per cycle is set within the partial load range lower than the rated load range, and initially in the intake stroke. Is a fuel-lean mixture M having a high air-fuel ratio is sucked into the combustion chamber 1, and in a later period, a mixture M having a substantially stoichiometric air-fuel ratio is sucked into the combustion chamber 1. The air-fuel ratio of the air-fuel mixture M formed in the mixer 12 is changed so that the air-fuel mixture M having a stoichiometric air-fuel ratio exists and the air-fuel mixture M having a high air-fuel ratio exists therearound. Then, with the EGR amount set to a low value of substantially zero, the air-fuel mixture M is compressed in the combustion chamber 1, and the stoichiometric air-fuel ratio mixture M in the vicinity of the spark plug 15 is spark-ignited and combusted by the spark plug 15. Thus, the stratified charge combustion is performed in a form in which the surrounding air-fuel mixture M having a high air-fuel ratio is burned, and the stratified combustion is lean combustion because the air-fuel ratio of the air-fuel mixture M in the entire combustion chamber 1 is a high air-fuel ratio. . During this first partial load operation, by performing such lean combustion in a state where the EGR amount is set to be substantially low, exhaust gas E having a high air-fuel ratio, that is, oxygen concentration, from the combustion chamber 1 to the exhaust passage 5 However, the relatively high exhaust gas E is discharged.

  During the first partial load operation, the control means 31 operates the exhaust gas bypass means 32 described above to operate, and discharges the exhaust gas E by bypassing the three-way catalyst unit 10 and exhausting the exhaust gas E. The pressure loss at the time of discharge is reduced, and the efficiency is improved.

  Note that, in the rated load operation and the first partial load operation, the exhaust gas air-fuel ratio setting means 33 described above is inactivated, and the EGR amount to the combustion chamber 1 is set to a lower value of substantially zero EGR. .

  Further, as shown in FIG. 2, the control means 31 performs the first partial load operation in which the exhaust gas bypass means 32 is operated as described above to improve the efficiency and the exhaust gas air-fuel ratio setting in the partial load region. The stoichiometric air-fuel ratio exhaust gas E is discharged from the combustion chamber 1 to the exhaust passage 5 with the means 33 in the activated state, and the exhaust gas bypass means 32 is deactivated to pass the stoichiometric air-fuel ratio exhaust gas E through the three-way catalyst unit 10. A partial load operation switching operation for switching between a state in which the second partial load operation in which NOx is favorably removed is performed is performed.

  Specifically, the control means 31 executes the first partial load operation in the middle load range in which the fuel supply amount per cycle is set within the middle load range which is the higher side within the partial load range. In the low load range where the fuel supply amount per cycle is set within the low load range, which is the lower side within the partial load range, the partial load operation switching operation is performed in the form of executing the second partial load operation. .

  That is, in the low load region, the second partial load operation is performed, and stratified combustion is performed in the combustion chamber 1 as in the first partial load operation. However, in the second partial load operation, the exhaust gas air-fuel ratio setting means 33 is activated, so that the amount of air supplied to the combustion chamber 1 per cycle is reduced, and a large amount of exhaust gas is generated in the entire combustion chamber 1. The stoichiometric air-fuel mixture 1 including E is combusted, and as a result, the stoichiometric air-fuel ratio exhaust gas E is discharged from the combustion chamber 1.

  Then, during the second partial load operation, the control means 31 causes the exhaust gas bypass means 32 described above to be in an inoperative state, causes the stoichiometric air-fuel ratio exhaust gas E to flow through the three-way catalyst unit 10 and discharges the exhaust gas. The NOx contained in E is well removed by the three-way catalyst method.

  Further, in such a rated load range and a low load range where the operation time is relatively short, the exhaust gas E having a stoichiometric air-fuel ratio is circulated to the three-way catalyst unit 10 and NOx contained in the exhaust gas E is converted by the three-way catalyst method. By removing it satisfactorily, it is possible to reduce the average emission amount of NOx in 13 modes assuming load fluctuations.

  Further, in the middle load region where the operation time is relatively long, the ignition by the spark plug 15 is performed when the first partial load operation in which the exhaust gas bypass means 32 is operated and the three-way catalyst unit 10 is bypassed to discharge the exhaust gas E is performed. You may comprise so that NOx discharge | emission amount reduction, such as retarding of a timing and the increase in EGR amount by the EGR control valve 21, may be aimed at. However, as described above, the NOx emission reduction target in the middle load range can be relaxed by the good removal of NOx in the other load range, so that the ignition timing is excessively retarded and the EGR amount is excessive. It is possible to suppress a decrease in efficiency due to a large increase and further improve the efficiency.

[Another embodiment]
In the form above Symbol embodiment, the exhaust gas air-fuel ratio setting means 33, although the air-fuel ratio of the exhaust gas E discharged from the combustion chamber 1 by increasing the EGR amount was configured to set to the stoichiometric air-fuel ratio, the combustion chamber When the air-fuel mixture M is burned lean, fuel is supplied to the combustion chamber 1 in the expansion stroke or exhaust stroke, so that the air-fuel ratio of the exhaust gas E discharged from the combustion chamber 1 is set to the stoichiometric air-fuel ratio, etc. Alternatively, another configuration may be used.

  An engine according to the present invention is an engine configured to perform stoichiometric combustion of an air-fuel mixture and distribute exhaust gas discharged from a combustion chamber during the stoichiometric combustion through a three-way catalyst unit for processing. The maximum efficiency can be improved while appropriately reducing the average emission amount of NOx over the partial load range, and for example, when used as a drive source of such a heat pump system, the coefficient of performance is improved satisfactorily It can be effectively used as an engine that can be used.

Schematic configuration diagram of the engine Diagram showing engine operating condition

Explanation of symbols

1: Combustion chamber 6: Bypass path 7: Switching valve 10: Three-way catalyst unit 20: EGR path 30: Engine control unit (ECU)
31: Control means 32: Exhaust gas bypass means 33: Exhaust gas air-fuel ratio setting means 100: Engine A: Air G: Fuel M: Air-fuel mixture E: Exhaust gas

Claims (2)

The mixture provided with a combustion chamber for burning by compression, comprising a three-way catalyst unit for treating an exhaust gas discharged from the combustion chamber in a three-way catalyst system in the exhaust path,
An engine configured to perform stoichiometric combustion of the air-fuel mixture and distribute exhaust gas discharged from the combustion chamber during the stoichiometric combustion through the three-way catalyst unit;
As an exhaust gas bypass means that can exhaust the exhaust gas discharged from the combustion chamber by bypassing the three-way catalyst part, as an empty gas path that connects the inlet side and the outlet side of the three-way catalyst part of the exhaust path And a switching valve for switching a supply destination of the exhaust gas discharged from the combustion chamber between the three-way catalyst unit and the bypass passage,
The rated load operation in which the stoichiometric combustion is performed in the rated load range where the fuel supply amount per cycle is set within the rated load range, and the exhaust gas supply destination is set to the three-way catalyst unit by the exhaust gas bypass means . And the air-fuel mixture is lean burned in a partial load range where the fuel supply amount is set within a partial load range lower than the rated load range, and the exhaust gas supply means is used as the bypass path in the exhaust gas bypass means . Comprising a control means for performing load control in a form of executing the first partial load operation to be an operating state to perform,
Exhaust gas air-fuel ratio setting means capable of setting the air-fuel ratio of the exhaust gas discharged from the combustion chamber to the stoichiometric air-fuel ratio in a state where the fuel supply amount is set within the partial load range;
In the partial load region, the control means sets the exhaust gas air-fuel ratio setting means in a non-operating state to perform the first partial load operation; sets the exhaust gas air-fuel ratio setting means to an operating state; It is configured to perform a partial load operation switching operation for switching between a state in which the second partial load operation to be in an inoperative state is performed,
The control means executes the first partial load operation in an intermediate load range in which the fuel supply amount is set in an intermediate load range which is a higher side in the partial load range, and the fuel supply amount is set in the partial load range. An engine configured to perform the partial load operation switching operation in a form in which the second partial load operation is executed in a low load range set within a low load range which is a lower side of the engine.   The engine according to claim 1, wherein the exhaust gas air-fuel ratio setting means is configured to increase the EGR amount and set the air-fuel ratio of the exhaust gas discharged from the combustion chamber to a stoichiometric air-fuel ratio.

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