JP2018178842A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of improving fuel economy by controlling a swirl flow.SOLUTION: An ECU 60 includes a charging heat quantity calculating section 110, a loss calculating section 120, a heat efficiency calculating section 130, and a valve control section 150. The charging heat quantity calculating section calculates a charging heat quantity Qi on the basis of a supply fuel quantity to an engine 1. The loss calculating section 120 calculates a total loss Qloss of an exhaust loss Qex, a pump loss Qp, a mechanical loss Qm, and a cooling loss Qr. The heat efficiency calculating section 130 calculates heat efficiency E of the engine 1 on the basis of the charging heat quantity Qi and the total loss Qloss. The valve control section 150 controls SCV opening so that the heat efficiency E approaches a maximum value on the basis of the variation in the heat efficiency E when the SCV opening is varied.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls a swirl control valve for generating a swirl flow (a swirling flow) in a combustion chamber.

  In order to improve the fuel efficiency of the internal combustion engine, it is necessary to reduce the loss in the internal combustion engine and to improve the thermal efficiency.

  The losses in internal combustion engines include cooling losses. The cooling loss is roughly classified into a cooling loss due to flow and a cooling loss due to spray collision. The cooling loss due to the flow is the loss caused by the heat transfer to the cylinder wall, the cylinder head, the piston, etc. by the gas flowing in the combustion chamber. The cooling loss due to the spray collision is a loss caused by the injected fuel being burned in the combustion chamber and colliding with a cylinder wall or the like in a high temperature state.

  When the swirl flow in the combustion chamber is strong, the cooling loss due to the flow increases. Conversely, when the swirl flow in the combustion chamber is weak, the cooling loss due to the spray collision increases. JP-A-2015-161216 (Patent Document 1) discloses a technique for reducing the cooling loss by controlling the swirl flow in consideration of such a trade-off relationship.

JP, 2015-161216, A

  However, in the technology described in JP-A-2015-161216, the swirl flow is controlled in consideration of only the cooling loss, and the other losses are not considered. Among losses in the engine, there are mechanical loss, exhaust loss and pump loss in addition to the cooling loss. For example, narrowing the intake path to strengthen the swirl flow may increase pump loss. Therefore, in the technique described in JP-A-2015-161216, although the cooling loss can be suppressed, other losses may increase, and as a result, the fuel efficiency may be deteriorated.

  The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a control device of an internal combustion engine capable of improving fuel consumption by controlling a swirl flow.

  The present invention relates generally to a control device for an internal combustion engine. The internal combustion engine includes a combustion chamber and a swirl control valve for generating a swirl flow in the combustion chamber. The control device includes an input heat amount calculation unit that calculates an amount of heat input based on the amount of fuel supplied to the internal combustion engine; a loss calculation unit that calculates an energy loss related to the swirl flow in the internal combustion engine; Based on the thermal efficiency calculation unit that calculates the thermal efficiency of the internal combustion engine and the change in thermal efficiency when changing the opening degree of the swirl control valve, the opening degree of the swirl control valve is controlled so that the thermal efficiency approaches the maximum value. And a valve control unit.

  Preferably, the valve control unit ends the control of the degree of opening of the swirl control valve when the exhaust gas temperature of the internal combustion engine exceeds a threshold.

  Preferably, when the pressure in the combustion chamber exceeds a threshold, the valve control unit ends the control of the opening degree of the swirl control valve.

  Preferably, the loss calculating unit calculates the energy loss based on a plurality of parameter values indicating the state of the internal combustion engine. The loss calculation unit acquires a part of the plurality of parameter values from the sensor installed in the internal combustion engine, and estimates the rest of the plurality of parameter values from the parameter values acquired from the sensor.

  Preferably, the control device further includes an initial opening setting unit that sets an initial opening according to the operating condition of the internal combustion engine. The valve control unit searches for the optimum opening degree while changing the opening degree of the swirl control valve from the initial opening degree using the hill climbing method, and controls the opening degree of the swirl control valve to the optimum opening degree.

  Preferably, the loss calculating unit calculates a total loss of the exhaust loss, the pump loss, the mechanical loss and the cooling loss as an energy loss.

  According to the present invention, the fuel efficiency of the internal combustion engine can be improved by controlling the swirl flow in consideration of the thermal efficiency.

FIG. 1 is a schematic configuration diagram of an engine shown as an example of an internal combustion engine according to the present embodiment. It is a figure showing an example of arrangement of a swirl control valve. It is a figure which shows an example of the relationship between the opening degree (SCV opening degree) of a swirl control valve, and thermal efficiency. It is a block diagram showing composition concerning control of SCV opening in ECU. It is a flow chart which shows a flow of processing of SCV control by a valve control part. It is a flow chart which shows a flow of processing of SCV control by a valve control part concerning modification 1. It is a flowchart which shows the flow of a process of SCV control by the valve control part which concerns on the modification 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated.

(Whole engine configuration)
FIG. 1 is a schematic configuration diagram of an engine shown as an example of an internal combustion engine according to an embodiment of the present invention. As shown in FIG. 1, the engine 1 has a plurality of cylinders 28. In FIG. 1, the engine 1 is shown as having four cylinders 28, but the number of cylinders 28 is not limited thereto.

  The engine 1 includes an air cleaner 12, a turbocharger 14, an intercooler 20, an intake manifold 22, and a throttle valve 24.

  The air cleaner 12 is provided in the intake passage and cleans the intake air by adsorbing impurities contained in the air taken in from the intake port 10.

  The turbocharger 14 includes a compressor 16 and a turbine 18. The compressor 16 is provided in the intake passage. The turbine 18 is provided in the exhaust passage. The compressor 16 and the turbine 18 are mechanically connected to each other and rotate integrally. The energy of the exhaust gas is received to rotate the turbine 18, and the intake air is pressurized by the compressor 16 that rotates in conjunction with the turbine 18.

  The intercooler 20 is provided between the turbocharger 14 (compressor 16) and the intake manifold 22. The intercooler 20 cools the intake air pressurized by the compressor 16 to a high temperature. The intercooler 20 may be air cooled or water cooled.

  The throttle valve 24 is provided upstream of the intake manifold 22 to adjust the amount of intake air. The opening degree of the throttle valve 24 is controlled by an ECU (Electronic Control Unit) 60.

  Each cylinder 28 has a plurality of intake ports. Although each cylinder 28 is shown in FIG. 1 as having two intake ports, the number of intake ports is not limited to this. Each cylinder 28 also has a plurality of exhaust ports. In FIG. 1, each cylinder 28 is shown as having two exhaust ports, but the number of exhaust ports is not limited to this. In each cylinder 28, a swirl control valve (SCV) 30 is provided at one of the two intake ports.

  FIG. 2 is a view showing an arrangement example of the swirl control valve (SCV) 30 in each cylinder 28. As shown in FIG. Referring to FIG. 2, a piston 76 is provided in the cylinder 28, and an intake port 72 and an exhaust port 74 are provided at the top of the cylinder 28. In FIG. 2, of the two intake ports, an intake port 72 provided with the swirl control valve 30 is shown. Also for the exhaust port, an exhaust port 74 of one of the two exhaust ports is shown.

  A swirl control valve 30 is provided at the intake port 72. The swirl control valve 30 is operated in the direction to throttle the air flow rate of the intake port 72, and the amount of air supplied from the intake port 72 to the combustion chamber 78 and the amount of air supplied from the other intake port to the combustion chamber 78 The swirl flow can be generated in the combustion chamber 78 by providing a difference in The opening degree of the swirl control valve 30 (hereinafter referred to as the SCV opening degree) is controlled by the ECU 60.

  Referring back to FIG. 1, engine 1 further includes an exhaust manifold 32, an exhaust filter 34, an EGR passage 38, an EGR valve 40, an EGR cooler 42, a low pressure EGR device 44, and an exhaust throttle valve 52. Equipped with

  The turbine 18 of the turbocharger 14 is provided downstream of the exhaust manifold 32, and rotates by receiving exhaust gas whose flow velocity is increased by narrowing the cross-sectional area of the exhaust passage on the blade. The exhaust filter 34 is provided downstream of the turbocharger 14 (turbine 18) and captures particulate matter in the exhaust gas. A catalyst device that purifies the exhaust gas using a catalyst may be combined with the exhaust filter 34.

  The EGR passage 38 connects the exhaust manifold 32 to the intake manifold 22 and allows part of the exhaust gas to recirculate from the exhaust manifold 32 to the intake manifold 22. The EGR valve 40 is provided in the EGR passage 38, and the opening degree is controlled by the ECU 60. The EGR cooler 42 is provided in the EGR passage 38 and cools the exhaust gas returned to the intake manifold 22 through the EGR passage 38.

  The low pressure EGR device 44 includes a low pressure EGR passage 46, an EGR cooler 48, and a low pressure EGR valve 50. The low pressure EGR passage 46 connects the exhaust passage downstream of the exhaust filter 34 (that is, downstream of the turbine 18 of the turbocharger 14) with the intake passage upstream of the compressor 16 of the turbocharger 14. A portion of the exhaust gas is recirculated from the downstream to the upstream of the compressor 16. The EGR cooler 48 is provided in the low pressure EGR passage 46 and cools the exhaust gas returned to the intake passage through the low pressure EGR passage 46. The low pressure EGR valve 50 is provided in the low pressure EGR passage 46, and the opening degree is controlled by the ECU 60.

  The low pressure EGR device 44 is lower in temperature than an EGR device (also referred to as a "high pressure EGR device" with respect to the low pressure EGR device 44) configured by the EGR passage 38, the EGR valve 40, and the EGR cooler 42. Enables a large amount of exhaust gas circulation. By using the low pressure EGR device 44 and the high pressure EGR device in combination, an effective NOx reduction can be realized.

  The exhaust throttle valve 52 is provided in the exhaust passage 36 downstream of the point where the low pressure EGR device 44 is connected in the exhaust passage. Although the exhaust throttle valve 52 is not essential, by throttling the exhaust throttle valve 52 when the low pressure EGR device 44 is activated, exhaust gas can be efficiently recirculated to the intake passage through the low pressure EGR passage 46.

  The engine 1 further includes a sensor group 25 and an ECU (Electronic Control Unit) 60.

  The sensor group 25 includes a plurality of sensors that detect various parameters indicating the state of the engine 1. The sensor group 25 includes, for example, a piston speed, an intake temperature, an engine coolant temperature, a throttle opening degree, a supercharging pressure, an in-cylinder pressure, an exhaust pressure, an exhaust temperature, an oil temperature, a fresh air amount (sucked from Amount of gas), the amount of EGR (the amount of gas recirculated by EGR), etc. are detected.

  The ECU 60 is a control device including a central processing unit (CPU), a storage device, an input / output buffer and the like (all not shown). The ECU 60 receives signals indicating various parameters detected by the sensor group 25. The ECU 60 controls each device of the engine 1 based on the respective signals. As one example, the ECU 60 controls the fuel injection amount so that the engine 1 is operated at a desired operating point according to the traveling condition of the vehicle. The various controls (processes) executed by the ECU 60 are not limited to the process by software, and may be processed by dedicated hardware (electronic circuit).

(Outline of control of SCV opening)
In order to improve the fuel efficiency of the internal combustion engine having the configuration as shown in FIG. 1, it is essential to improve the thermal efficiency of the internal combustion engine. The heat input to the internal combustion engine (proportional to the amount of fuel injected) is consumed for work (power) and loss. Among these, losses are roughly classified into exhaust loss, pump loss, mechanical loss, and cooling loss. Exhaust losses indicate the energy that is dumped as exhaust. Pump loss refers to the loss caused by intake and exhaust resistance. Mechanical losses are indicative of losses caused by the frictional resistance of the machine. The cooling loss represents energy lost due to contact between the combustion gas and the cylinder wall surface.

  As described above, the cooling loss is roughly classified into a cooling loss due to flow and a cooling loss due to spray collision. The cooling loss due to flow tends to increase as the swirl flow becomes stronger. On the other hand, the cooling loss due to the spray collision tends to increase as the swirl flow becomes weaker. In general, when the cooling loss is reduced by the control of the swirl flow, the exhaust temperature tends to increase and the exhaust loss increases. And if the swirl control valve 30 is controlled in the closing direction to suppress the cooling loss due to the spray collision and the swirl flow is intensified, the intake resistance increases and the pump loss tends to increase. Furthermore, it is conceivable that the in-cylinder pressure changes as the cooling loss increases or decreases due to the control of the swirl flow, and the mechanical loss increases or decreases. Thus, the control of the swirl flow increases or decreases various losses.

  FIG. 3 is a view showing an example of the relationship between the opening degree (SCV opening degree) of the swirl control valve 30 and the thermal efficiency. Here, the thermal efficiency is a value indicating the ratio of work to the amount of heat input. As shown in FIG. 3, the thermal efficiency changes in accordance with the SCV opening, and exhibits a maximum value when the SCV opening takes a certain value. However, the optimum SCV opening when the thermal efficiency is near the maximum value changes depending on the operating conditions (fuel injection amount, engine rotation speed, etc.). Therefore, the ECU 60 according to the present embodiment controls the SCV opening degree so that the thermal efficiency approaches the maximum value each time the operating condition changes.

(Configuration of ECU 60)
FIG. 4 is a block diagram showing a configuration related to control of the SCV opening in the ECU 60. As shown in FIG. As shown in FIG. 4, the ECU 60 includes an input heat quantity calculation unit 110, a loss calculation unit 120, a thermal efficiency calculation unit 130, an initial opening setting unit 140, a valve control unit 150, and a storage unit 160. .

  The heat input calculation unit 110 calculates the heat input Qi by multiplying the fuel injection amount by a predetermined proportional coefficient.

  The loss calculation unit 120 calculates an energy loss associated with the swirl flow in the engine 1. The energy loss associated with swirl flow is a loss that fluctuates in response to changes in the strength of the swirl. The loss calculation unit 120 includes an exhaust loss calculation unit 121, a pump loss calculation unit 122, a mechanical loss calculation unit 123, and a cooling loss calculation unit 124. The loss calculating unit 120 calculates the total loss Qloss (= Qex + Qp + Qm + Qr) of the exhaust loss Qex, the pump loss Qp, the mechanical loss Qm, and the cooling loss Qr calculated by each of these units as an energy loss.

  The exhaust loss calculation unit 121 calculates an exhaust loss Qex from the exhaust temperature. The pump loss calculation unit 122 calculates the pump loss Qp based on the gas amount (fresh air amount, EGR amount), the supercharging pressure, the throttle opening degree, and the exhaust pressure. The mechanical loss calculation unit 123 calculates the mechanical loss Qm based on the geometrical drawing value (for example, a value indicated by a Striebeck diagram), the piston speed, the in-cylinder pressure, the oil temperature, and the engine coolant temperature. The cooling loss calculation unit 124 calculates the cooling loss Qr based on the heat input, the in-cylinder pressure, and the theoretical thermal efficiency.

  The thermal efficiency calculation unit 130 calculates the thermal efficiency E (= (Qi−Qloss) / Qi) from the input heat quantity Qi and the total loss Qloss.

  The initial opening degree setting unit 140 sets the initial opening degree (base opening degree) of the swirl control valve 30 in accordance with the operating condition of the engine 1. The initial opening setting unit 140 outputs, to the valve control unit 150, a control start instruction to which the set initial opening is added.

  Immediately after the engine 1 is started, the initial opening degree setting unit 140 sets an initial opening degree according to the operating condition at a timing when the operating condition is stable. Thereafter, the initial opening setting unit 140 sets the initial opening each time the operating condition of the engine 1 changes. The initial opening degree setting unit 140 calculates the feature amount according to the operating condition of the engine 1 in the latest predetermined period, and when the difference with the previous feature amount stored in the storage unit exceeds the threshold, the operating condition is Judge that it has changed. For example, the initial opening setting unit 140 calculates the average value of the fuel injection amount and the average value of the engine rotational speed in the latest predetermined period as the above-mentioned feature value. The initial opening degree setting unit 140 determines that the operating condition has changed when the average value of the fuel injection amount exceeds the predetermined threshold or when the average value of the engine rotational speed exceeds the predetermined threshold. When it is determined that the operating condition has changed, the initial opening degree setting unit 140 stores the feature amount corresponding to the operating condition of the latest predetermined period in the storage unit 160 as the previous feature amount.

  The initial opening degree setting unit 140 stores in advance information in which the feature amount is associated with the initial opening degree, and sets an initial opening degree according to the feature amount based on the information. The information is, for example, a table in which the feature amount is associated with the initial opening degree, and is created in advance by experiment or the like.

  The valve control unit 150 controls the swirl control valve 30 so as to be one SCV opening selected from the plurality of stages of SCV openings.

  When the control start instruction is received, the valve control unit 150 controls the SCV opening degree so that the thermal efficiency E approaches the maximum value based on the change of the thermal efficiency E when changing the SCV opening degree. Specifically, the valve control unit 150 searches for the optimal SCV opening while changing the SCV opening from the initial opening using a hill climbing method. When finding the optimal SCV opening, the valve control unit 150 ends the search process, and maintains the opening of the swirl control valve 30 at the optimal SCV opening. Details of control of the SCV opening degree in the valve control unit 150 will be described later.

  The storage unit 160 stores data used when the initial opening degree setting unit 140 and the valve control unit 150 execute processing. For example, the storage unit 160 stores, as the previous feature amount, the feature amount corresponding to the operating condition of the latest predetermined period when it is determined by the initial opening degree setting unit 140 that the operating condition has been changed.

(Method of controlling SCV opening by valve controller)
The flow of processing of SCV control by the valve control unit 150 will be described with reference to FIG. FIG. 5 is a flowchart showing a flow of processing of SCV control by the valve control unit 150.

  When receiving the control start instruction from the initial opening degree setting unit 140, the valve control unit 150 changes the SCV opening degree of the swirl control valve 30 to the initial opening degree added to the control start instruction in step S1.

  Next, in step S2, the valve control unit 150 acquires, from the thermal efficiency calculation unit 130, the thermal efficiency E (0) calculated from various parameter values when the swirl control valve 30 is at the initial opening degree. The thermal efficiency calculation unit 130 calculates the thermal efficiency E (0) based on the input heat quantity Qi and the total loss Qloss calculated from various parameter values when the swirl control valve 30 is at the initial opening degree.

  Next, in step S3, the valve control unit 150 changes the SCV opening degree to the closing direction side by one step from the initial opening degree. Further, the valve control unit 150 sets a variable k indicating the number of times of change of the SCV opening degree to 1, and stores direction information indicating that the first control direction is the closing direction in the storage unit 160.

  Next, in step S4, the valve control unit 150 acquires from the thermal efficiency calculation unit 130 the thermal efficiency E (k) (E (1) in the first step S4) calculated from various parameter values at the current SCV opening.

  Next, at step S5, the valve control unit 150 calculates the thermal efficiency E (k-1) (E (0) at the first step S5) calculated at the previous time and the thermal efficiency E (k) calculated at the step S4 (first In step S5, E (1)) is compared to determine whether the thermal efficiency E has increased since the previous time.

  If the thermal efficiency E is increasing (YES in S5), the valve control unit 150 adds 1 to the variable k (step S6). Thereafter, the valve control unit 150 changes the SCV opening degree by one step in the same direction as the k-1th control direction indicated by the direction information stored in the storage unit 160 (step S7). Furthermore, in step S7, the valve control unit 150 stores, in the storage unit 160, direction information indicating the k-th control direction (either the closing direction or the opening direction). If it is determined YES in the first step S5, the valve control unit 150 changes the SCV opening by one step in the closing direction in step S7, and the direction information indicating that the second control direction is the closing direction Are stored in the storage unit 160.

  On the other hand, if the thermal efficiency E has not increased (NO in S5), the valve control unit 150 adds 1 to the variable k (step S8). Thereafter, the valve control unit 150 changes the SCV opening degree by one step in the direction opposite to the k-1th control direction indicated by the direction information stored in the storage unit 160 (step S9). Furthermore, in step S9, the valve control unit 150 stores, in the storage unit 160, direction information indicating the k-th control direction (either the closing direction or the opening direction). When it is determined as NO in the first step S5, the valve control unit 150 changes the SCV opening by one step in the opening direction in step S9, and indicates the direction information indicating that the second control direction is the opening direction. Are stored in the storage unit 160.

  Next, in step S10, the valve control unit 150 determines whether the variable k is 2 or less. If the variable k is 2 or less (YES in S10), the process returns to step S4.

  If the variable k exceeds 2 (NO in S10), the valve control unit 150 determines whether the k-1th control direction is the same as the kth control direction (step S11). If the k−1-th control direction and the k-th control direction are the same (YES in S11), the process returns to step S4. If the k−1-th control direction is different from the k-th control direction (YES in S11), the process ends.

  According to the above process, it is recognized by the process of the first steps S5 to S9 whether the initial opening is on the side of the opening direction or on the side of the closing direction with respect to the optimal SCV opening. If the initial opening is closer to the opening than the optimum SCV opening, the thermal efficiency E is increased by changing the SCV opening to the closing direction in step S3. Therefore, if the initial opening is closer to the opening than the optimum SCV opening, YES is determined in step S5, and storage unit 160 stores direction information indicating that the second control direction is the closing direction. . Conversely, when the initial opening degree is closer to the closing direction than the optimal SCV opening degree, the thermal efficiency E is lowered by controlling the SCV opening degree to the closing direction side in step S3. Therefore, if the initial opening is closer to the closing direction than the optimal SCV opening, NO is determined in step S5, and the direction information indicating that the second control direction is the opening direction is stored in the storage unit 160. . Therefore, depending on whether the second control direction is the closing direction or the opening direction, it is recognized whether the initial opening degree is the opening direction side or the closing direction side with respect to the optimal SCV opening degree.

  If the initial opening is closer to the opening than the optimum SCV opening (that is, if the second control direction is the closing direction), steps S4 to S11 are repeated, whereby the thermal efficiency E is closest to the maximum value. Until then, the SCV opening is controlled stepwise in the closing direction. If the SCV opening is further changed by one step in the closing direction after the thermal efficiency E approaches the maximum value, the thermal efficiency E decreases. Therefore, in step S9, the SCV opening degree is returned in the opening direction by one step, and the process ends. Thereby, the swirl control valve 30 is controlled to the optimum SCV opening degree at which the thermal efficiency E is closest to the maximum value. As a result, the fuel consumption of the engine 1 is improved.

  Similarly, when the initial opening is closer to the closing direction than the optimum SCV opening (that is, when the second control direction is the closing direction), steps S4 to S11 are repeated to maximize the thermal efficiency E. The SCV opening is controlled stepwise in the opening direction until it is closest to the value. If the SCV opening is further changed by one step in the opening direction after the thermal efficiency E approaches the maximum value, the thermal efficiency E decreases. Therefore, in step S9, the SCV opening degree is returned by one step in the closing direction, and the process is ended. Thereby, the swirl control valve 30 is controlled to the optimum SCV opening degree at which the thermal efficiency E is closest to the maximum value. As a result, the fuel consumption of the engine 1 is improved.

  The process shown in FIG. 5 is executed each time the operating condition of the engine 1 is changed. As a result, the swirl control valve 30 is appropriately controlled so that the SCV opening degree becomes optimum according to the operating conditions of the engine 1.

(Modification 1)
When the SCV opening degree is controlled so that the thermal efficiency E approaches the maximum value, it is conceivable that the exhaust gas temperature rises due to the reduction of the cooling loss. Therefore, when the exhaust gas temperature exceeds a preset threshold value (upper limit value), the valve control unit 150 sets the opening degree of the swirl control valve 30 so that the exhaust gas temperature does not exceed the endurance temperature of the exhaust manifold 32. The process of controlling the SCV opening degree may be ended so that the thermal efficiency E approaches the local maximum while maintaining the current opening degree. The threshold is set to a temperature lower than the endurance temperature of the exhaust manifold 32.

  A flow of processing of SCV control of the valve control unit 150 according to the first modification will be described with reference to FIG. FIG. 6 is a flowchart showing a flow of processing of SCV control by the valve control unit 150 according to the first modification.

  In SCV control in the first modification, step S20 is executed before step S10. In step S20, the valve control unit 150 determines whether the exhaust gas temperature has exceeded a threshold. If the exhaust gas temperature does not exceed the threshold (NO in S20), the process proceeds to S10. On the other hand, when the exhaust gas temperature exceeds the threshold (YES in S20), the valve control unit 150 ends the process of controlling the SCV opening. Thus, the exhaust temperature can be prevented from exceeding the endurance temperature of the exhaust manifold 32.

(Modification 2)
When controlling the SCV opening degree so that the thermal efficiency E approaches the maximum value, it is conceivable that the in-cylinder pressure increases with the increase of the thermal efficiency. Therefore, when the in-cylinder pressure exceeds a preset threshold value (upper limit value), the valve control unit 150 opens the opening degree of the swirl control valve 30 so that the in-cylinder pressure does not exceed the limit of the cylinder. Alternatively, the process of controlling the SCV opening may be ended so that the thermal efficiency E approaches the maximum value. In addition, the said threshold value is set in consideration of mechanical durability, such as a cylinder.

  A flow of processing of SCV control of the valve control unit 150 according to the second modification will be described with reference to FIG. 7. FIG. 7 is a flowchart showing a flow of processing of SCV control by the valve control unit 150 according to the second modification.

  In SCV control in the second modification, step S30 is executed before step S10. In step S30, the valve control unit 150 determines whether the in-cylinder pressure exceeds a threshold. If the in-cylinder pressure does not exceed the threshold (NO in S30), the process proceeds to S10. On the other hand, if the in-cylinder pressure exceeds the threshold (YES in S30), the valve control unit 150 ends the process of controlling the SCV opening. This can prevent the in-cylinder pressure from exceeding the limit of the cylinder.

(Modification 3)
The loss calculation unit 120 acquires from the sensor group 25 some of a plurality of parameter values used to calculate the exhaust loss Qex, the pump loss Qp, the mechanical loss Qm, and the cooling loss Qr, and acquires the rest from the sensor group 25. You may estimate based on the parameter value which was Thereby, the number of sensors can be reduced and the cost of the engine 1 can be suppressed.

  For example, the loss calculation unit 120 calculates the VN turbo throttle area coefficient proportional to the exhaust gas passage area in the turbine 18 of the turbocharger 14, the fresh air amount (g / s), and the fuel injection amount (g / s), The exhaust pressure (kPa) is estimated by the following equation (1) based on the supercharging pressure (kPa).

Exhaust pressure = (fresh air amount + fuel injection amount) x supercharging pressure / VN turbo throttle area coefficient ... (1)
In addition, the loss calculation unit 120 calculates the exhaust pressure (kPa) calculated by the above equation (1), the fuel injection amount (g / s), the equivalence ratio, and the boost pressure (kPa) as follows. The exhaust temperature is estimated by equation (2) of

Exhaust temperature = fuel injection amount × equivalent ratio × supercharging pressure / exhaust pressure (2)
(Modification 4)
In the above description, the thermal efficiency calculation unit 130 calculates the thermal efficiency E based on the total loss Qloss of the exhaust loss Qex, the pump loss Qp, the mechanical loss Qm, and the cooling loss Qr. However, a loss with a small amount of fluctuation due to a change in the strength of the swirl flow may be omitted. For example, if the strength of the swirl flow is changed but the fluctuation of the mechanical loss Qm is small enough to ignore, the thermal efficiency calculation unit 130 adds the exhaust loss Qex, the pump loss Qp and the cooling loss Qr to a total loss (= Qex + Qp + Qr). The thermal efficiency E may be calculated based on the above.

  As described above, the engine 1 shown in FIG. 1 includes the combustion chamber 78 and the swirl control valve 30 for generating a swirl flow in the combustion chamber 78. As shown in FIG. 4, the ECU (control device) 60 includes an input heat amount calculation unit 110, a loss calculation unit 120, a thermal efficiency calculation unit 130, and a valve control unit 150. The heat input calculation unit 110 calculates the heat input Qi based on the amount of fuel supplied to the engine 1. The loss calculation unit 120 calculates an energy loss associated with the swirl flow in the engine 1. The thermal efficiency calculation unit 130 calculates the thermal efficiency E of the engine 1 based on the input heat quantity Qi and the loss. The valve control unit 150 controls the SCV opening so that the thermal efficiency E approaches the maximum value, based on the change in the thermal efficiency E when changing the SCV opening. Thus, the swirl flow is controlled such that the thermal efficiency E approaches the maximum value. As a result, the fuel consumption of the engine 1 is improved.

  Preferably, when the exhaust gas temperature exceeds the threshold value, the valve control unit 150 maintains the opening degree of the swirl control valve 30 at the current opening degree and ends the control of the SCV opening degree. Thus, the exhaust temperature can be prevented from exceeding the endurance temperature of the exhaust manifold 32.

  Preferably, when the pressure (in-cylinder pressure) in the combustion chamber 78 exceeds the threshold, the valve control unit 150 maintains the opening degree of the swirl control valve 30 at the current opening degree and ends the control of the SCV opening degree. This can prevent the in-cylinder pressure from exceeding the limit of the cylinder.

  Preferably, the loss calculation unit 120 calculates the energy loss based on a plurality of parameter values indicating the state of the engine 1. The loss calculation unit 120 may acquire some of the plurality of parameter values from the sensor group 25 installed in the engine 1 and estimate the rest of the plurality of parameter values from the parameter values acquired from the sensor group 25. Thereby, the number of sensors installed in the engine 1 can be reduced, and the cost of the engine 1 can be suppressed.

  Preferably, the ECU 60 further includes an initial opening setting unit 140 that sets an initial opening according to the operating conditions of the engine 1. The valve control unit 150 searches for the optimum SCV opening while changing the SCV opening from the initial opening using the hill climbing method, and controls the opening of the swirl control valve 30 to the optimum SCV opening searched for. Thus, the time required for searching for the optimum SCV opening using the hill climbing method in the valve control unit 150 can be shortened compared to the case where the fixed initial opening is set regardless of the operating conditions.

  Preferably, the loss calculating unit 120 calculates the total loss Qloss of the exhaust loss Qex, the pump loss Qp, the mechanical loss Qm, and the cooling loss Qr as the above-described energy loss. Thus, the thermal efficiency E is accurately calculated.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  Reference Signs List 1 engine, 10 intake ports, 12 air cleaners, 14 turbochargers, 16 compressors, 18 turbines, 20 intercoolers, 22 intake manifolds, 24 throttle valves, 25 sensor groups, 28 cylinders, 30 swirl control valves, 32 exhaust manifolds, 34 exhaust filters , 36 exhaust passage, 38 EGR passage, 40 EGR valve, 42, 48 EGR cooler, 44 EGR device, 46 low pressure EGR passage, 50 low pressure EGR valve, 52 exhaust throttle valve, 60 ECU, 72 intake port, 74 exhaust port, 76 Piston, 78 combustion chamber, 110 input heat amount calculation unit, 120 loss calculation unit, 121 exhaust loss calculation unit, 122 pump loss calculation unit, 123 mechanical loss calculation unit, 124 cooling loss calculation unit, 130 thermal efficiency Out portion, 140 initial opening setting unit, 150 a valve control unit, 160 storage unit.

Claims (6)

A control device for an internal combustion engine, the internal combustion engine comprising: a combustion chamber; and a swirl control valve for generating a swirl flow in the combustion chamber,
The controller is
An input heat amount calculation unit that calculates the amount of heat input based on the amount of fuel supplied to the internal combustion engine;
A loss calculating unit that calculates an energy loss related to the swirl flow in the internal combustion engine;
A thermal efficiency calculation unit that calculates the thermal efficiency of the internal combustion engine based on the input heat quantity and the energy loss;
A valve control unit for controlling the opening degree of the swirl control valve such that the thermal efficiency approaches a maximum value based on a change in the heat efficiency when the opening degree of the swirl control valve is changed; Control device.   The control device for an internal combustion engine according to claim 1, wherein the valve control unit ends the control of the opening degree of the swirl control valve when the exhaust gas temperature of the internal combustion engine exceeds a threshold.   The control device for an internal combustion engine according to claim 1, wherein the valve control unit ends the control of the opening degree of the swirl control valve when the pressure in the combustion chamber exceeds a threshold. The loss calculation unit calculates the energy loss based on a plurality of parameter values indicating the state of the internal combustion engine.
The loss calculation unit acquires part of the plurality of parameter values from a sensor installed in the internal combustion engine, and estimates the rest of the plurality of parameter values from the parameter values acquired from the sensor. A control device of an internal combustion engine according to any one of 3. The system further comprises an initial opening setting unit configured to set an initial opening according to the operating condition of the internal combustion engine,
The valve control unit searches for the optimum opening degree while changing the opening degree of the swirl control valve from the initial opening degree using a hill climbing method, and controls the opening degree of the swirl control valve to the optimum opening degree. The control device of an internal combustion engine according to any one of claims 1 to 4.   The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the loss calculation unit calculates a total loss of an exhaust loss, a pump loss, a mechanical loss, and a cooling loss as the energy loss.

Images