JP6351215B2 - Engine system - Google Patents

Description

  The present invention relates to an engine that outputs shaft power by compressing and burning an air-fuel mixture in a combustion chamber, and stoichiometric combustion that sets an air-fuel ratio of the air-fuel mixture combusted in the combustion chamber within a stoichiometric range according to the engine load. Control means for switching the combustion mode of the engine between a mode and a lean combustion mode in which an air-fuel ratio of an air-fuel mixture combusted in the combustion chamber is set within a lean range where the fuel is leaner than the stoichiometric range. Related to the engine system.

This type of engine system includes a stoichiometric combustion mode in which the combustion mode of the engine sets the air-fuel ratio of the air-fuel mixture within the stoichiometric range (for example, about 1.0 in terms of excess air ratio) according to the engine load, and the air-fuel mixture. It is possible to switch between a lean combustion mode in which the air-fuel ratio is set within a lean range exceeding the stoichiometric range (for example, 1.4 to 1.6 in terms of excess air ratio).
Further, as such an engine system, a compression type heat pump circuit having a compressor that uses engine shaft power as a drive source is provided, and the rotational speed of the engine is controlled based on the heat load of the heat pump circuit such as an air conditioning load. Is known (see, for example, Patent Document 1).

In such an engine system, in a predetermined stoichiometric region where the engine load is relatively large, the engine combustion mode is set to the stoichiometric combustion mode, and an operation emphasizing output is performed, and conversely, a predetermined lean where the engine load is relatively small. In the region, the engine combustion mode is set to the lean combustion mode, and the efficiency-oriented operation is performed.
That is, the control means switches the combustion mode from the stoichiometric combustion mode to the lean combustion mode when the engine load changes from the stoichiometric region to the lean region, and conversely, the engine load increases from the lean region to the stoichiometric region. When changed, the combustion mode is switched from the lean combustion mode to the stoichiometric combustion mode.

JP 2008-286066 A

In the stoichiometric combustion mode set in the stoichiometric region, the amount of heat input to the engine is increased in order to obtain a high output, but the heat capacity of the air-fuel mixture is relatively small, so the combustion temperature in the combustion chamber is relatively high. Therefore, the heat resistance of components such as exhaust valves exposed to high temperatures may be a factor that determines the life and maintenance frequency of the engine system. Therefore, in terms of life and the like, it is desirable to set the combustion mode switching load value as high as possible so that the integrated operation amount in the stoichiometric combustion mode is as short as possible.
However, in terms of emissions, there are cases where it is better not to make the integrated operation amount in the stoichiometric combustion mode too short in other aspects, such as a stoichiometric combustion mode in which NOx in exhaust gas can be completely removed with a three-way catalyst. It is difficult to uniquely determine the combustion mode switching load value.
In the present application, the integrated operation amount indicates an amount related to a load on the engine accumulated in each combustion mode. For example, the integrated operation time, an integrated value (that is, work amount) in the operation time of the engine load, etc. Can be set as the integrated operation amount.

Further, since the required load on the engine varies depending on the demand situation on the consumer side and the application of the system, when switching the combustion mode according to the engine load as described above, the stoichiometric combustion mode and the lean combustion mode This also changes the balance of the integrated operation amount.
In particular, when the stoichiometric combustion operation ratio, which is the ratio of the integrated operation amount in the stoichiometric combustion mode to the total integrated operation amount, exceeds the appropriate value at the time of design, components such as exhaust valves exposed to high temperatures are predicted. In some cases, heat damage may occur earlier, resulting in a problem in terms of life, such as the engine life being less than expected. Furthermore, there may be a problem in efficiency such that the high efficiency by the lean combustion mode cannot be sufficiently exhibited and the overall efficiency is lowered.

  The present invention has been made paying attention to such a point, and an object thereof is to provide an efficiency in an engine system configured to be able to switch the engine combustion mode between a stoichiometric combustion mode and a lean combustion mode in accordance with the engine load. And a technique capable of switching the combustion mode in an appropriate state in terms of performance and life such as emission.

To achieve this object, an engine system according to the present invention includes:
An engine that outputs shaft power by compressing and burning an air-fuel mixture in a combustion chamber;
A stoichiometric combustion mode in which the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is set within the stoichiometric range according to the engine load, and the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is less than the stoichiometric range. An engine system comprising control means for switching the combustion mode of the engine between a lean combustion mode set within a lean range,
A compression heat pump circuit having a compressor using the shaft power of the engine as a drive source;
Comprising recording means for recording actual data of required load as a heat load of the heat pump circuit;
The actual data is data including a specific time period in which the operation in the stoichiometric combustion mode is less than other time periods in one day in the past,
The control means has a combustion mode switching load value that is a threshold of an engine load when switching the combustion mode between the stoichiometric combustion mode and the lean combustion mode, and a combustion mode in a preset stoichiometric combustion suppression period In a form in which the switching load value is made larger than the combustion mode switching load value in a period other than the stoichiometric combustion suppression period, a switching load value correction process for correcting the combustion mode switching load value is executed ,
The control means requests the engine load in accordance with the heat load of the heat pump circuit, and based on the actual data of the required load recorded in the recording means, the specific time zone in one day The point is to set the stoichiometric combustion suppression period .

According to this feature configuration, the threshold value of the engine load when the switching load value correction process is executed in the preset stoichiometric combustion suppression period and the combustion mode is switched between the stoichiometric combustion mode and the lean combustion mode. The combustion mode switching load value is set to a value larger than a period other than the stoichiometric combustion suppression period.
Then, in the stoichiometric combustion suppression period, the combustion mode switching load value is set to be larger, so that when the engine load is reduced, the stoichiometric combustion mode is switched to the lean combustion mode at the earliest possible timing. Conversely, when the engine load is increasing, the lean combustion mode is switched to the stoichiometric combustion mode as late as possible. Therefore, since the operation in the lean combustion mode is actively performed, the stoichiometric combustion operation ratio decreases, approaches an appropriate ratio, and transitions to an appropriate state capable of improving life and efficiency. become.
On the other hand, during periods other than the stoichiometric combustion suppression period, the combustion mode switching load value is set to be small, so that when the engine load is decreasing, the stoichiometric combustion mode is switched to the lean combustion mode as late as possible. . Conversely, when the engine load is increasing, the lean combustion mode is switched to the stoichiometric combustion mode as soon as possible. Therefore, since the operation in the stoichiometric combustion mode will be actively performed, the stoichiometric combustion operation ratio increases and approaches an appropriate ratio, and it is possible to improve the emission by the three-way catalyst or the like. Transition can be made.
Therefore, according to the present invention, in an engine system configured to switch the engine combustion mode between the stoichiometric combustion mode and the lean combustion mode in accordance with the engine load, in an appropriate state in terms of performance and life such as efficiency and emission. A technique capable of switching the combustion mode can be provided.
Further, according to the present feature configuration, the record data of the required load is recorded in the recording means, so that the operation in the stoichiometric combustion mode has not been performed in the past from the recorded record data. In addition, it is possible to recognize a period in which the followability to the required load is not a problem even if the switching to the stoichiometric combustion mode is suppressed. If the recognized period is set as the stoichiometric combustion suppression period, it is possible to efficiently prevent the stoichiometric combustion operation ratio from excessively exceeding the appropriate value in accordance with the past required load performance.

A further characteristic configuration of the engine system according to the present invention is as follows .
Before SL control means lies in controlling the rotational speed of the engine based on the heat load of the heat pump circuit.

The engine system according to the present application includes a compression type heat pump circuit having a compressor that uses the engine shaft power as a drive source, as in this characteristic configuration, and the control means is an engine corresponding to the heat load of the heat pump circuit. It is preferable that the target rotational speed is obtained and the target rotational speed is set so as to increase as the heat load of the heat pump circuit increases.

A further characteristic configuration of the engine system according to the present invention is as follows.
The control means measures the ratio of the accumulated operation amount in the stoichiometric combustion mode with respect to the total accumulated operation amount as a stoichiometric combustion operation ratio, and increases the stoichiometric combustion suppression period as the measured stoichiometric combustion operation ratio increases. The point is that the stoichiometric combustion suppression period is corrected according to the stoichiometric combustion operation ratio in the specific time zone of one day .

  According to this feature configuration, as the stoichiometric combustion operation ratio increases, the stoichiometric combustion suppression period in which the combustion mode switching load value is set larger by the switching load value correction processing is expanded, and combustion in the stoichiometric combustion mode is performed over a long period of time. The mode switching timing can be delayed. Therefore, it is possible to further prevent the stoichiometric combustion operation ratio from excessively exceeding the appropriate value.

A further characteristic configuration of the engine system according to the present invention is as follows.
The control means measures the ratio of the accumulated operation amount in the stoichiometric combustion mode with respect to the total accumulated operation amount as a stoichiometric combustion operation ratio, and when the measured stoichiometric combustion operation ratio is a predetermined set ratio or more, the engine The point is that a stoichiometric combustion suppression process for suppressing the switching of the combustion mode to the stoichiometric combustion mode is executed.

According to this characteristic configuration, when the measured stoichiometric combustion operation ratio is equal to or higher than a predetermined set ratio determined as an appropriate value at the time of design, even if it is a period other than the stoichiometric combustion suppression period, The stoichiometric combustion suppression process is executed, and switching of the combustion mode to the stoichiometric combustion mode is suppressed. Therefore, the combustion mode is maintained as lean as possible.
Then, compared with the case where the stoichiometric combustion operation ratio is less than the set ratio, an increase in the integrated operation amount in the stoichiometric combustion mode is suppressed, and thus it is further prevented that the stoichiometric combustion operation ratio exceeds an appropriate value excessively. .

The block diagram which shows the whole structure of the engine system which concerns on embodiment of this invention. Graph showing the allocation of stoichiometric area and lean area to engine load The graph explaining the fluctuation state of the heat load and engine load of the heat pump circuit The figure which shows the processing flow of a 1st stoichiometric combustion suppression process. The figure which shows the processing flow of a 2nd stoichiometric combustion suppression process The figure which shows the processing flow of switching load value correction processing

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the engine system includes an engine 1 that compresses and burns an air-fuel mixture M in a combustion chamber 2 and outputs a driving force, and a control unit that controls the output of the engine 1 according to a required load. The apparatus 20 etc. are provided.
Furthermore, the engine system of the present embodiment is provided with a compression heat pump circuit 30 having a compressor 31 driven by the engine 1, and is configured as an engine-driven heat pump system. The heat load of the heat pump circuit 30 is received as a required load, and the rotational speed of the engine 1 (the rotational speed of the output shaft 7) is controlled based on the thermal load.

Connected to the combustion chamber 2 of the engine 1 are an intake passage 3 for sucking the air-fuel mixture M and an exhaust passage 4 through which exhaust gas E discharged from the engine 1 flows.
A fuel supply path 6 for supplying a fuel gas G such as natural gas city gas is connected to the intake path 3 via a mixer 5.
The air A sucked from the end of the intake passage 3 and the fuel gas G supplied from the fuel supply passage 6 are mixed by the mixer 5, and the mixture M is sucked into the combustion chamber 2 through the intake passage 3. In the combustion chamber 2, the air-fuel mixture M is compressed, and is ignited by a spark plug (not shown) in a compressed state to burn and expand, whereby the output shaft 7 is rotated and driving force is output, The exhaust gas E generated by the combustion is exhausted through the exhaust passage 4. That is, the engine 1 is configured in a normal four-cycle type.
Furthermore, the engine 1 is gear-coupled to the output shaft 7 and forcibly rotates the output shaft 7 by driving a battery (not shown) when the engine 1 is started, and the rotational speed of the engine 1, that is, A rotation speed sensor 9 for detecting the rotation speed of the engine 1 is provided.
The cell motor 8 is controlled by the control device 20, and the detection information of the rotation speed sensor 9 is configured to be input to the control device 20.

The fuel supply passage 6 is provided with a fuel supply valve 10 capable of adjusting the air-fuel ratio of the air-fuel mixture M by adjusting the supply amount of the fuel gas G, and the intake passage 3 is mixed to be sucked into the combustion chamber 2. A throttle valve 11 capable of adjusting the intake amount of the air M is provided.
The exhaust passage 4 includes an oxygen concentration sensor 12 for detecting the oxygen concentration of the exhaust gas E, a three-way catalyst 13 through which the exhaust gas E can pass, and a temperature of the exhaust gas E immediately after leaving the three-way catalyst 13. A catalyst temperature sensor 14 serving as a catalyst temperature detecting means for detecting the temperature 13 is provided.
The fuel supply valve 10 and the throttle valve 11 are controlled by the control device 20, and the detection information of the oxygen concentration sensor 12 and the detection information of the catalyst temperature sensor 14 are configured to be input to the control device 20, respectively. Yes.
The oxygen concentration sensor 12 is provided at a location upstream of the three-way catalyst 13 in the exhaust passage 4, and the catalyst temperature sensor 14 is provided at a location downstream of the three-way catalyst 13 in the exhaust passage 4.
As an oxygen concentration sensor for detecting the oxygen concentration of the exhaust gas E, in addition to the oxygen concentration sensor 12 provided on the upstream side of the three-way catalyst 13 in the exhaust passage 4, it is provided on the downstream side of the three-way catalyst 13 in the exhaust passage 4. The detection information of the oxygen concentration sensor may also be input to the control device 20. The catalyst temperature sensor 14 may be provided inside the three-way catalyst 13.

  In the compression heat pump circuit 30, in addition to the compressor 31, an outdoor heat exchanger 32, an indoor heat exchanger 33, an expansion valve 34, and a destination of the refrigerant compressed by the compressor 31 are exchanged outdoors. A four-way valve 35 and the like for switching between the heat exchanger 32 side and the indoor heat exchanger 33 side are provided. The indoor heat exchanger 33 and the expansion valve 34 are installed in an indoor unit Ui installed in a room that is an air-conditioning target space, and members other than the indoor heat exchanger 33 and the expansion valve 34, that is, the engine 1 and the compressor. 31, the outdoor heat exchanger 32, the four-way valve 35, and the like are installed in an outdoor unit Ue installed outside the air-conditioning target space.

The compressor 31 is connected to the engine 1 by the power transmission mechanism 40 and drives the compressor 31 by the shaft power of the engine 1 to compress the refrigerant, thereby air conditioning such as cooling operation and heating operation as will be described later. It is configured to drive.
The power transmission mechanism 40 includes an engine-side pulley 41 fixed to the output shaft 7 of the engine 1, a compressor-side pulley 43 connected to the drive shaft of the compressor 31 via an electromagnetic clutch 42, and the engine-side pulley 41. And a belt 44 wound around the compressor side pulley 43 and the like.
The operation of the electromagnetic clutch 42 is controlled by the control device 20. In other words, the electromagnetic clutch 42 is switched on and off by the control device 20, whereby the transmission connection between the engine 1 and the compressor 31 is interrupted, and the shaft power of the engine 1 is transmitted to the compressor 31 and the coaxial power. Is switched to a state in which is not transmitted to the compressor 31.

When the compression heat pump circuit 30 is in a cooling operation, the discharge side of the compressor 31 is connected to the outdoor heat exchanger 32 and the inflow side of the compressor 31 is the indoor heat, as indicated by a solid line as the state of the four-way valve 35 in FIG. The four-way valve 35 is switched so as to be connected to the exchanger 33. When the four-way valve 35 is switched in this way, the high-temperature and high-pressure refrigerant vapor compressed by the compressor 31 flows into the outdoor heat exchanger 32, and the outdoor heat exchanger 32 functions as a condenser. In the heat exchanger 32, the high-temperature and high-pressure refrigerant vapor dissipates heat and condenses by heat exchange with the outside air. In addition, the condensed refrigerant liquid passes through the expansion valve 34 and is reduced in temperature and pressure to flow into the indoor heat exchanger 33. The indoor heat exchanger 33 functions as an evaporator, and the indoor heat exchanger 33 has a low temperature. The low-pressure refrigerant liquid absorbs heat and evaporates by heat exchange with room air. Then, the refrigerant circulates through the heat pump circuit 30 in such a form that the evaporated refrigerant vapor is returned to the compressor 31.
That is, the indoor heat exchanger 33 is configured to cool the air-conditioning target space by using the cold generated when the refrigerant liquid absorbs heat and evaporates.

On the other hand, when heating the compression heat pump circuit 30, the discharge side of the compressor 31 is connected to the indoor heat exchanger 33 and the inflow side of the compressor 31 is connected as shown by a broken line as the state of the four-way valve 35 in FIG. The four-way valve 35 is switched so as to be connected to the outdoor heat exchanger 32. When the four-way valve 35 is switched in this way, the high-temperature and high-pressure refrigerant vapor compressed by the compressor 31 flows into the indoor heat exchanger 33, and the indoor heat exchanger 33 functions as a condenser. In the heat exchanger 32, the high-temperature and high-pressure refrigerant vapor dissipates heat and condenses by heat exchange with room air. In addition, the condensed refrigerant liquid passes through the expansion valve 34 and is cooled to low temperature and pressure and flows into the outdoor heat exchanger 32. The outdoor heat exchanger 32 functions as an evaporator, and the outdoor heat exchanger 32 has a low temperature. The low-pressure refrigerant liquid absorbs heat and evaporates by heat exchange with room air. Then, the refrigerant circulates through the heat pump circuit 30 in such a form that the evaporated refrigerant vapor is returned to the compressor 31.
That is, the indoor heat exchanger 33 is configured to perform heating or the like of the air-conditioning target space by using the heat generated when the refrigerant vapor dissipates heat and condenses.

The shaft power for driving the compressor 31 by the engine 1 is, for example, in the cooling operation, the temperature of the outside air that is the heat radiation destination of the refrigerant vapor in the outdoor heat exchanger 32, or the heat absorption source of the refrigerant liquid in the indoor heat exchanger 33 It is according to the heat load calculated | required from the temperature of indoor air which is, the pressure state of a refrigerant | coolant, a flow state, etc. In other words, when the compressor 31 is connected to the engine 1 by the power transmission mechanism 40, the engine 1 is required to have an engine load corresponding to the air conditioning load (heat load) in the compression heat pump circuit 30. become.
On the other hand, the control device 20 obtains the target rotational speed according to the air conditioning load, and opens the throttle valve 11 so that the rotational speed of the engine 1 detected by the rotational speed sensor 9 becomes the target rotational speed. To adjust the intake amount of the air-fuel mixture M to the combustion chamber 2. Thus, so-called throttle valve output control for controlling the output of the engine 1 is performed.

  The control device 20 adjusts the opening degree of the fuel supply valve 10 while monitoring the oxygen concentration detected by the oxygen concentration sensor 12, thereby adjusting the air-fuel ratio of the air-fuel mixture M combusted in the combustion chamber 2 within the stoichiometric range ( For example, the stoichiometric combustion mode set within about 1.0 in terms of excess air ratio and the air-fuel ratio of the air-fuel mixture M combusted in the combustion chamber 2 are within a lean range exceeding the stoichiometric range (for example, 1. The combustion mode of the engine 1 can be switched freely between the lean combustion mode set to 4 to 1.6).

Although not shown in the drawings, the remote controller of the engine-driven heat pump system is provided with a temperature setting unit that sets the air conditioning target temperature, and a room temperature sensor that detects the temperature of the air conditioning target space. Is provided. The setting information of the temperature setting unit and the detection information of the room temperature sensor are input to the control device 20, and the control device 20 is detected by the air conditioning target temperature set by the temperature setting unit and the room temperature sensor. A deviation from the temperature of the air-conditioning target space is obtained as a heat load of the heat pump circuit 30.
Then, the target rotational speed of the engine 1 is set so as to increase as the heat load of the heat pump circuit 30 increases, and the throttle valve output control is executed so that the rotational speed of the engine 1 becomes the set target rotational speed. Then, the opening degree of the throttle valve 11 is adjusted.

Further, referring also to FIG. 2, the engine load changes with the control of the rotational speed of the engine 1 by the throttle valve output control, but the stoichiometric region in which the engine load becomes a predetermined combustion mode switching load value L0 or more. In SA (the downward slanted line portion in FIG. 2), the combustion mode of the engine 1 is set to the stoichiometric combustion mode, and in the lean region LA (dot portion in FIG. 2) where the engine load is less than the combustion mode switching load value L0, The combustion mode of the engine 1 is set to the lean combustion mode.
That is, the threshold value between the stoichiometric region SA and the lean region LA corresponds to a combustion mode switching load value L0 that is a threshold value of the engine load when switching between the stoichiometric combustion mode and the lean combustion mode.

For example, as shown in FIG. 2, the control device 20 has a relatively small engine load in the engine load region corresponding to the product of the engine speed and the rotational torque applied to the output shaft 7 of the engine 1. It has an engine load map that defines a lean area LA set as an area and a stoichiometric area SA set as an area with a higher engine load than the lean area.
When the engine load is in the lean region LA as indicated by points P1 and P2 in FIG. 2, the oxygen concentration of the exhaust gas E detected by the oxygen concentration sensor 12 is set according to the air-fuel ratio within the lean range. In order to adjust the supply amount of the fuel gas G so as to achieve the lean target concentration, the opening degree of the fuel supply valve 10 is adjusted to set the combustion mode of the engine 1 to the lean combustion mode.
On the other hand, when the engine load is in the stoichiometric region SA as indicated by points P3, P4, and P5 in FIG. 2, the oxygen concentration of the exhaust gas E detected by the oxygen concentration sensor 12 depends on the air-fuel ratio within the stoichiometric range. In order to adjust the supply amount of the fuel gas G so as to be a set stoichiometric target concentration (for example, substantially zero), the opening of the fuel supply valve 10 is adjusted, and the combustion mode of the engine 1 is changed to the stoichiometric combustion mode. Set.

That is, the combustion mode of the engine 1 changes from the lean combustion mode at the timing when the engine load enters the stoichiometric region SA across the boundary lines BL1 and BL2 from the lean region LA as the rotational speed and torque of the engine 1 increase. Switch to stoichiometric combustion mode. On the other hand, as the rotational speed or rotational torque of the engine 1 decreases, the combustion mode of the engine 1 changes from the stoichiometric combustion mode at the timing when the engine load enters the lean region LA across the boundary lines BL1 and BL2 from the stoichiometric region SA. Switch to lean combustion mode.
For example, as shown by the solid line arrow (point P1 → point P2 → point P3) in FIG. 2, when the engine load increases, the engine load increase locus (point P2 → point P3) and the boundary line BL2 The engine load corresponding to the intersection of the combustion mode switching load value L0 (between the stoichiometric combustion mode and the lean combustion mode), which is a threshold value of the engine load when switching the combustion mode between the stoichiometric combustion mode and the lean combustion mode. The engine is switched to the stoichiometric combustion mode from the lean combustion mode at the timing when the rotational speed of the engine 1 becomes equal to or higher than the combustion mode switching load value L0.

Referring to FIG. 1, the three-way catalyst 13 is configured by supporting a noble metal component such as platinum, palladium, or rhodium on an inorganic carrier such as alumina, for example, in which an oxidizing component and a reducing component are balanced. By passing the exhaust gas E having the theoretical equivalent ratio, NOx, CO and HC emissions in the exhaust gas E are simultaneously removed.
That is, when the engine 1 is operated in the stoichiometric combustion mode, when the exhaust gas E passes through the three-way catalyst 13, NOx in the exhaust gas E is reduced, and CO and HC are oxidized. , CO and HC are removed simultaneously.
On the other hand, when the engine 1 is operated in the lean combustion mode, when the exhaust gas E passes through the three-way catalyst 13, CO and HC are mainly oxidized and removed. Since NOx is scarcely contained, NOx emissions are suppressed to a specified value or less.

  The control device 20 suppresses switching to the stoichiometric combustion mode, measuring means 21 that measures the stoichiometric combustion operation ratio that is the ratio of the stoichiometric combustion mode integrated operation time that is the integrated operation time in the stoichiometric combustion mode with respect to the total integrated operation time. It functions as the setting means 22 for setting the power stoichiometric combustion suppression period, and further has a recording means 23 composed of a nonvolatile memory or the like for recording the past data of the heat load of the heat pump circuit 30.

  Specifically, the measuring means 21 is an integrated operation time in the lean combustion mode, an integrated operation time in the lean combustion mode, and an integrated operation time in the stoichiometric combustion mode as the integrated operation time in each of the stoichiometric combustion mode and the lean combustion mode. Each stoichiometric combustion mode integrated operation time is measured, and the ratio of the stoichiometric combustion mode integrated operation time to the total integrated operation time, which is the sum of the measured lean combustion mode integrated operation time and stoichiometric combustion mode integrated operation time, is stoichiometric combustion. Calculated as the driving ratio.

Further, the setting means 22 is configured to switch to the stoichiometric combustion mode, such as a period when the operation in the stoichiometric combustion mode has not been performed in the past, based on the actual heat load data recorded in the recording means 23. The period in which the followability of the heat pump circuit 30 to the heat load is not a problem even when switching is suppressed is recognized. For example, such a period includes the middle period of spring and autumn, Saturday, Sunday, public holidays, and the time zone from 18:00 to 9:00 in the next morning, because the heat load of the heat pump circuit 30 is relatively low. It can be recognized as a period in which driving is not performed much.
And the setting means 22 sets the period recognized in this way as a stoichiometric combustion suppression period which should suppress the switch to stoichiometric combustion mode.

  The control device 20 is configured to appropriately execute stoichiometric combustion suppression processing and switching load value correction processing, which will be described later, when switching the combustion mode of the engine 1 between the stoichiometric combustion mode and the lean combustion mode. Details of each processing flow will be described below.

[Stoichi combustion suppression processing]
The stoichiometric combustion suppression process is a process for switching the combustion mode in an appropriate state in terms of performance and life such as efficiency and emission, and the engine load corresponding to the heat load of the heat pump circuit 30 is in the stoichiometric region SA. Even if it exists, it is comprised as a process which suppresses switching to the stoichiometric combustion mode of the combustion mode of the engine 1. FIG.
In addition, the control device 20 has a plurality of types of suppression operations that suppress switching of the combustion mode of the engine 1 to the stoichiometric combustion mode. Hereinafter, these plural types of suppression operations will be described with reference to FIG.
As shown by the broken line in FIG. 3, it is assumed that the heat load of the heat pump circuit 30 fluctuates between the stoichiometric area SA and the lean area LA. Here, the fluctuation of the heat load of the heat pump circuit 30 shows, for example, a typical fluctuation of the heat load in one day. The heat load temporarily enters the stoichiometric area SA immediately after startup, and thereafter It changes in the lean area LA in the period until noon, changes in the stoichiometric area SA in the period from noon to evening, and changes in the lean area LA in the period until the subsequent stop.
And the fluctuation pattern of an engine load at the time of performing a stoichiometric combustion suppression process with multiple types of suppression operation with respect to the heat load of the heat pump circuit 30 which fluctuates in this way is shown by the continuous line of FIG.

First, as the first suppression operation, as shown by the arrow X in FIG. 3, by suppressing the increasing tendency of the engine load, the switching of the combustion mode of the engine 1 to the stoichiometric combustion mode is suppressed. Has been.
Specifically, in this first suppression operation, when the heat load of the heat pump circuit 30 is rapidly increased at the time of startup or the like, and the increase is temporary, the engine load increases slowly. As a result, the engine load is prevented from temporarily entering the stoichiometric region SA. As a result, the combustion mode of the engine 1 is maintained in the lean combustion mode, and the excessive increase in the stoichiometric combustion operation ratio is good. To be prevented.

Next, as the second suppression operation, as shown by the arrow Y in FIG. 3, the switching of the combustion mode of the engine 1 to the stoichiometric combustion mode is intermittently prohibited, whereby the combustion mode of the engine 1 is changed. It is supposed to suppress switching to the stoichiometric combustion mode.
Specifically, in the second suppression operation, when the thermal load of the heat pump circuit 30 changes in the stoichiometric region SA, the engine load is defined as the thermal load at regular time intervals of about several tens of minutes to one hour. Irrespectively, the engine 1 is forcibly shifted to the vicinity of the upper limit of the lean region LA, and the combustion mode of the engine 1 is forcibly changed to the lean combustion mode.
In this second suppression operation, switching to the stoichiometric combustion mode is not completely prohibited, so that the cumulative operation in the stoichiometric combustion mode is ensured while appropriately ensuring the followability of the engine load to the heat load of the heat pump circuit 30. An increase in the amount is suppressed, and an excessive increase in the stoichiometric combustion operation ratio is favorably prevented.

Next, as the third suppression operation, although not shown in the figure, the switching of the combustion mode of the engine 1 to the stoichiometric combustion mode is continuously prohibited by continuously prohibiting the switching of the combustion mode of the engine 1 to the stoichiometric combustion mode. It is supposed to suppress.
Specifically, in the third suppression operation, switching to the stoichiometric combustion mode is completely prohibited, thereby further suppressing an increase in the cumulative operation amount in the stoichiometric combustion mode, and an excessive increase in the stoichiometric combustion operation ratio. Even better prevented.

Further, when executing the stoichiometric combustion suppression process, the control device 20 selects the suppression operation to be executed from the plurality of suppression operations based on the actual load data of the heat pump circuit 30 recorded in the recording unit 23. Is configured to do.
That is, from the actual data of the heat load of the heat pump circuit 30, it is predicted how the current engine load will change in the future, and the followability of the engine load with respect to the heat load with respect to the predicted change of the engine load, A suppression operation that achieves an appropriate balance such as the stoichiometric combustion operation ratio is selected from the plurality of types of suppression operations and employed.
For example, when it can be predicted that the engine load temporarily enters the stoichiometric region and then returns to the lean combustion region, the first suppression operation is adopted and executed, and the increasing tendency of the engine load is alleviated.
Further, when it is predicted that the engine load continuously shifts to the stoichiometric region, the second to third suppression operations are adopted and executed, and the switching of the combustion mode of the engine 1 to the stoichiometric combustion mode is continuously performed. Or it is prohibited intermittently.
Furthermore, the control device 20 is configured to execute a first stoichiometric combustion suppression process and a second stoichiometric combustion suppression process as the stoichiometric combustion suppression process. Details of each stoichiometric combustion suppression process will be described below. explain.

(First stoichiometric combustion suppression process)
The first stoichiometric combustion suppression process is configured as a process that suppresses switching of the combustion mode of the engine 1 to the stoichiometric combustion mode in a preset stoichiometric combustion suppression period.
Further, the control device 20 is able to cope with the heat load of the heat pump circuit 30 even if the switch to the stoichiometric combustion mode is suppressed, such as in the middle of spring / autumn, Saturday, Sunday, public holidays, or from 18:00 to 9:00 the next morning. A period in which the followability is not a problem is set in advance as a stoichiometric combustion suppression period.
Hereinafter, the first stoichiometric combustion suppression process will be described based on the flowchart shown in FIG.
In the first stoichiometric combustion suppression process, when it is determined that the current time is the preset stoichiometric combustion suppression period (step # 11), the engine load corresponding to the heat load of the heat pump circuit 30 is in the stoichiometric region SA. Even so, one of the suppression operations is selected and executed as described above (step # 12). As a result, switching of the combustion mode of the engine 1 to the stoichiometric combustion mode is suppressed, and the stoichiometric combustion operation ratio is prevented from excessively exceeding the appropriate value.

Further, in step # 11, the stoichiometric combustion suppression period may be set in advance by direct input by the user, but the control device 20 can determine the heat load of the heat pump circuit 30 recorded in the recording means 23. The stoichiometric combustion suppression period is set based on the actual data.
Specifically, the control device 20 refers to past performance data, and suppresses switching to the stoichiometric combustion mode, such as a period when the operation in the stoichiometric combustion mode is not performed in the past. A period in which the followability of the heat pump circuit 30 to the heat load is not a problem is recognized, and the recognized period is set as the stoichiometric combustion suppression period. If the stoichiometric combustion suppression period is set in this way, it is efficiently prevented that the stoichiometric combustion operation ratio excessively exceeds the appropriate value in accordance with the past heat load performance.

Further, the control device 20 performs the first stoichiometric combustion suppression process. It is configured to correct the stoichiometric combustion suppression period according to the stoichiometric combustion operation ratio in such a manner that the stoichiometric combustion suppression period set in advance as described above is expanded as the stoichiometric combustion operation ratio measured by the measuring means 21 is larger. Yes.
That is, if it can be judged that it is not preferable in terms of performance or life that the stoichiometric combustion operation ratio is relatively large and further increased, for example, in the middle of spring and autumn, Saturday, Sunday, public holidays, 18:00 to 9:00 the next morning The stoichiometric combustion suppression period set as the time zone is expanded before and after that.
For example, if the time period from 18:00 to 9:00 is set as the stoichiometric combustion suppression period, the period before and after that period is expanded by 3 hours, and the time period from 15:00 to 12:00 noon is stoichiometric. It can be a combustion suppression period.

(Second stoichiometric combustion suppression process)
Next, the second stoichiometric combustion suppression process is a process for suppressing the switching of the engine combustion mode to the stoichiometric combustion mode when the stoichiometric combustion operation ratio measured by the measuring means 21 is equal to or greater than a predetermined set ratio. It is configured.
Hereinafter, the second stoichiometric combustion suppression process will be described based on the flowchart shown in FIG.
Specifically, in the second stoichiometric combustion suppression process, the stoichiometric combustion operation ratio measured by the measuring means 21 is, for example, a set ratio (for example, 25) corresponding to the stoichiometric combustion operation ratio assumed when designing the life of the engine 1. In the case of above (step # 21), even if the engine load corresponding to the heat load of the heat pump circuit 30 is in the stoichiometric region SA, as described above, one of the suppression operations is selected and executed. (Step # 22). Then, compared to the case where the stoichiometric combustion operation ratio is less than the set ratio, an increase in the integrated operation amount in the stoichiometric combustion mode is suppressed, and as a result, the stoichiometric combustion operation ratio is prevented from exceeding an appropriate value. Become.

[Switching load value correction processing]
The switching load value correction process is a process for switching the combustion mode in an appropriate state in terms of performance and life such as efficiency and emission, and the combustion mode switching load value in a preset stoichiometric combustion suppression period. The process is configured to correct the combustion mode switching load value in a form that is larger than the combustion mode switching load value in a period other than the stoichiometric combustion suppression period.
Hereinafter, the switching load value correction processing will be described based on the flowchart shown in FIG.

In this switching load value correction process, it is determined whether or not the present time is a preset stoichiometric combustion suppression period (step # 31).
If it is determined in step # 31 that the current time is the stoichiometric combustion suppression period, a predetermined set adjustment width a is added to the current combustion mode switching load value L0 to obtain a new combustion mode switching load value L0. In this manner, the combustion mode switching load value L0 is increased (step # 33). As a result, the operation in the lean combustion mode is actively performed, and the further increase in the stoichiometric combustion operation ratio Rs is suppressed, and the improvement in life and efficiency is emphasized.

  On the other hand, if it is determined in step # 31 that the current time is not the stoichiometric combustion suppression period, a predetermined set adjustment width b is subtracted from the current combustion mode switching load value L0 to obtain a new combustion mode switching load value L0. In this manner, the combustion mode switching load value L0 is decreased. As a result, the operation in the stoichiometric combustion mode is actively performed, and the further decrease in the stoichiometric combustion operation ratio Rs is suppressed, and emphasis is placed on the improvement of emission by the three-way catalyst 13 or the like. It becomes a state.

In order to limit the setting range of the combustion mode switching load value L0 to the predetermined upper limit value L0max or less in step # 33, a value obtained by adding a predetermined setting adjustment width a to the combustion mode switching load value L0 is the upper limit. Whether or not the value is maintained below the value L0max is determined (step # 32), and only when it is determined that the value is maintained, the combustion mode switching load value L0 is increased in step # 33.
The upper limit L0max is set as the maximum value of the engine load that can be operated in the lean combustion mode. For example, the upper limit value L0max can be determined as the engine load when the throttle valve 11 is fully opened in the lean combustion mode. it can.

In order to limit the setting range of the combustion mode switching load value L0 to the predetermined lower limit value L0 min or more in step # 35, the value obtained by subtracting the predetermined setting adjustment width b from the combustion mode switching load value L0 is the lower limit before that. It is determined whether or not the value is maintained at or above the value L0min (step # 34). Only when it is determined that the value is to be maintained, the combustion mode switching load value L0 is decreased at step # 35.
The lower limit L0min is set as the minimum value of the engine load that can be operated in the stoichiometric combustion mode. For example, it is determined as the engine load when the opening of the throttle valve 11 is minimized in the stoichiometric combustion mode. be able to.

[Another embodiment]
Finally, other embodiments of the present invention will be described. Note that the configuration of each embodiment described below is not limited to being applied independently, and can be applied in combination with the configuration of other embodiments as long as no contradiction arises.

(1) In the above embodiment, the controller 20 is configured to execute the stoichiometric combustion suppression process separately from the switching load value correction process. However, processes other than the switching load value correction process are appropriately omitted. It doesn't matter.

(2) In the above-described embodiment, the example in which the compression heat pump circuit 30 including the compressor 31 using the shaft power of the engine 1 as a drive source is provided as the rotational load of the engine 1 has been described, but the compression heat pump circuit 30 is provided. In addition, another rotational load such as a generator may be provided.

The present invention includes an engine that outputs shaft power by compressing and burning an air-fuel mixture in a combustion chamber;
A stoichiometric combustion mode in which the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is set within the stoichiometric range according to the engine load, and the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is less than the stoichiometric range. The present invention can be suitably used as an engine system including control means for switching the combustion mode of the engine between a lean combustion mode set within a lean range.

1: Engine 2: Combustion chamber 7: Output shaft 13: Three-way catalyst 20: Control device (control means)
23: recording means 30: heat pump circuit 31: compressor 42: electromagnetic clutch E: exhaust gas L0: combustion mode switching load value Rs: stoichiometric combustion operation ratio SA: stoichiometric region LA: lean region

Claims (4)

An engine that outputs shaft power by compressing and burning an air-fuel mixture in a combustion chamber;
A stoichiometric combustion mode in which the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is set within the stoichiometric range according to the engine load, and the air-fuel ratio of the air-fuel mixture combusted in the combustion chamber is less than the stoichiometric range. An engine system comprising control means for switching the combustion mode of the engine between a lean combustion mode set within a lean range,
A compression heat pump circuit having a compressor using the shaft power of the engine as a drive source;
Comprising recording means for recording actual data of required load as a heat load of the heat pump circuit;
The actual data is data including a specific time period in which the operation in the stoichiometric combustion mode is less than other time periods in one day in the past,
The control means has a combustion mode switching load value that is a threshold of an engine load when switching the combustion mode between the stoichiometric combustion mode and the lean combustion mode, and a combustion mode in a preset stoichiometric combustion suppression period In a form in which the switching load value is made larger than the combustion mode switching load value in a period other than the stoichiometric combustion suppression period, a switching load value correction process for correcting the combustion mode switching load value is executed ,
The control means requests the engine load in accordance with the heat load of the heat pump circuit, and based on the actual data of the required load recorded in the recording means, the specific time zone in one day An engine system that sets the stoichiometric combustion suppression period . Before SL control means obtains a target rotational speed of the engine in response to the heat load of the heat pump circuit, according to claim 1 for setting the target rotational speed so as to increase as the thermal load is large of the heat pump circuit Engine system.   The control means measures the ratio of the accumulated operation amount in the stoichiometric combustion mode with respect to the total accumulated operation amount as a stoichiometric combustion operation ratio, and increases the stoichiometric combustion suppression period as the measured stoichiometric combustion operation ratio increases. The engine system according to claim 1 or 2, wherein the stoichiometric combustion suppression period is corrected according to the stoichiometric combustion operation ratio in the specific time zone of one day.   The control means measures the ratio of the accumulated operation amount in the stoichiometric combustion mode with respect to the total accumulated operation amount as a stoichiometric combustion operation ratio, and when the measured stoichiometric combustion operation ratio is a predetermined set ratio or more, the engine The engine system according to any one of claims 1 to 3, wherein a stoichiometric combustion suppression process is performed to suppress switching of the combustion mode to the stoichiometric combustion mode.

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