JP6443374B2 - Engine control device - Google Patents

Description

  The technology disclosed herein relates to a control device that controls an engine with a turbocharger.

  Conventionally, as an engine equipped with a turbocharger, an engine in which a bypass passage that bypasses the turbine is provided in the exhaust passage and a waste gate valve is provided in the bypass passage is known (see, for example, Patent Document 1). ). In such an engine, by controlling the opening degree of the waste gate, the flow rate of the exhaust gas passing through the turbine is adjusted, and the driving force of the compressor, that is, the supercharging pressure by the operation of the turbocharger is controlled. .

Japanese Patent Laid-Open No. 08-061074

  As a method for controlling the opening degree of the waste gate valve in the engine as described above, a target charging efficiency which is a target value of the charging efficiency corresponding to the travel request from the driver is obtained, and the supercharging pressure is determined based on the target charging efficiency. It is conceivable to calculate a target boost pressure, which is a target value of, and set the opening of the waste gate valve to an opening required to realize the target boost pressure.

  However, with the waste gate valve opening control based on such target charging efficiency, the waste gate valve is fully closed when the flow rate through the compressor is relatively large, such as when the engine is operating at high load and high speed. By doing so, even if the supercharging pressure is increased as much as possible in a state where all of the exhaust gas passes through the turbine, a charging efficiency that cannot be realized may be set as the target charging efficiency. In this case, the waste gate valve continues to be fully closed aiming at a target supercharging pressure for a target charging efficiency that cannot be realized.

  In this case, the exhaust pressure (primary exhaust pressure) on the upstream side of the turbine rises over a relatively long time, so that the exhaust efficiency is lowered, which may cause misfire and deterioration of fuel consumption. In addition, since the compressor is required to have a work rate higher than the performance, the compressor may over-rotate. In addition, the controllability of the supercharging pressure by the turbocharger is remarkably deteriorated, and the engine operation control including the waste gate valve opening control may fail.

  The technology disclosed herein has been made in view of such a point, and the purpose thereof is to suppress the occurrence of misfire due to an increase in exhaust pressure, deterioration of fuel consumption, and excessive rotation of the compressor, and This is to prevent the controllability of the supercharging pressure from deteriorating significantly.

  In order to achieve the above object, the technique disclosed herein devised a method for setting the target charging efficiency so that the charging efficiency that cannot be achieved even if the waste gate valve is fully closed is not set to the target charging efficiency.

Specifically, the technology disclosed herein includes a turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and a waste provided in a bypass passage that bypasses the turbine in the exhaust passage. The present invention is directed to an engine control device including a gate valve. The control device includes a target charging efficiency setting unit that sets a target charging efficiency that is a target value of the engine charging efficiency, and a valve control unit that controls the opening of the waste gate valve based on the target charging efficiency. The target charging efficiency setting unit has a limit value of a compressor passage flow rate that is a flow rate of intake air passing through the compressor, and an intake air density set based on the limit value and an upstream pressure of the compressor, Is used to set an upper limit value of the target charging efficiency according to the operating state of the engine, and the target charging efficiency is limited so that the target charging efficiency does not exceed the upper limit value.

  According to this configuration, the target charging efficiency setting unit sets the target charging efficiency, and the valve control unit controls the opening degree of the waste gate valve based on the target charging efficiency. Thereby, the flow rate of the exhaust gas flowing through the bypass passage, that is, the flow rate of the exhaust gas bypassing the turbine is adjusted, and the supercharging pressure due to the operation of the turbocharger is adjusted.

  At this time, the target charging efficiency is set so as not to exceed the upper limit value of the target charging efficiency set according to the operating state of the engine, so that the target charging efficiency cannot be realized even when the waste gate valve is fully closed. Therefore, it is possible to prevent the waste gate valve from being fully closed and to shorten the period during which the waste gate valve is fully closed. Thereby, generation | occurrence | production of the misfire resulting from the raise of exhaust pressure and the deterioration of a fuel consumption can be suppressed. In addition, according to such waste gate valve opening control, the compressor is not required to have a work rate higher than the performance, so that the compressor can be prevented from over-rotating and the controllability of the supercharging pressure is remarkably high. It can be prevented from getting worse.

  In the engine control apparatus, it is preferable that the target charging efficiency setting unit variably sets an upper limit value of the target charging efficiency in accordance with the engine speed.

  The filling efficiency of the engine varies depending on the engine speed. Therefore, if the upper limit value of the target charging efficiency is a fixed value, the target charging efficiency is limited so that the target charging efficiency does not exceed such a relatively lower upper limit value although the realizable charging efficiency is larger than the upper limit value depending on the engine speed. As a result, the output performance of the engine may be degraded.

  On the other hand, according to the above configuration, since the upper limit value of the target charging efficiency is variably set according to the engine speed, the upper limit value of the target charging efficiency can be changed according to the operating state of the engine. As a result, the upper limit value of the target charging efficiency can be set in accordance with the charging efficiency that can be realized in accordance with the operating state of the engine, so that the output performance of the engine decreases due to the setting of the upper limit value for the target charging efficiency. Can be prevented.

The technology disclosed herein also includes a turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and a waste gate valve provided in a bypass passage that bypasses the turbine in the exhaust passage. The engine control device is provided. The control device includes a target charging efficiency setting unit that sets a target charging efficiency that is a target value of the engine charging efficiency, and a valve control unit that controls the opening of the waste gate valve based on the target charging efficiency. The target charging efficiency setting unit calculates an upper limit value of the target charging efficiency according to an operating state of the engine, limits the target charging efficiency so that the target charging efficiency does not exceed the upper limit value, The charging efficiency setting unit also variably sets an upper limit value of the target charging efficiency according to the engine speed, and the target charging efficiency setting unit is further set to a compressor passing flow rate that is a flow rate of intake air passing through the compressor. It has a certain limit value, to set the upper limit of the target charging efficiency based on the limit value.

  The charging efficiency of the engine depends on the flow rate through the compressor, and the flow rate through the compressor is one of the parameters indicating the operating state of the compressor. The compressor flow rate has a limit in the same manner as the rotation speed of the compressor is limited, and the compressor has an operation region in which the compressor flow rate chokes. In the operation region where the compressor passage flow rate chokes, the compressor is over-rotated.

  According to the above configuration, it is possible to variably set the upper limit value of the target charging efficiency in accordance with the engine speed only by setting a fixed limit value for the compressor passage flow rate. In addition, by setting the limit value of the compressor passage flow rate to be less than the choking flow rate, it is possible to avoid operating the compressor in the operation region where the compressor passage flow rate is choked. Thereby, the controllability of the supercharging pressure can be prevented from deteriorating significantly by preventing the compressor from over-rotating.

  According to the engine control apparatus, it is possible to suppress the occurrence of misfire due to an increase in exhaust pressure, the deterioration of fuel consumption, and the excessive rotation of the compressor, and it is possible to prevent the controllability of the supercharging pressure from being significantly deteriorated.

It is a schematic block diagram of an engine. It is a functional block diagram of ECU. It is a flowchart which shows the opening degree control of a WG valve. It is an image figure of a compressor performance map. It is a block diagram which shows the setting method of target filling efficiency.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of an engine 1 to which a control device according to this embodiment is applied.

  The engine 1 is a spark ignition direct injection engine with a supercharger. As shown in FIG. 1, the engine 1 mainly burns a mixture of intake air (air) and fuel, and the engine body 3. An intake passage 5 through which intake air introduced into the engine flows, an exhaust passage 7 through which exhaust gas generated by combustion of the air-fuel mixture in the engine body 3 flows, and a turbocharger that supercharges intake air using the energy of the exhaust gas 8, an external EGR mechanism 9 for performing external EGR, sensors for detecting information used for controlling the engine 1, and an ECU (Engine Control Unit) 11 for controlling the engine 1 as a whole. .

<Engine body>
The engine body 3 includes a cylinder block 15 in which a plurality of cylinders 13 (for example, four, only one is shown in FIG. 1) are provided in series, and a cylinder head 17 disposed on the cylinder block 15. Inside the cylinder block 15 and the cylinder head 17, although not shown, a water jacket through which engine coolant flows is provided.

  Each cylinder 13 is fitted with a piston 21 that divides a combustion chamber 19 for burning the air-fuel mixture so as to reciprocate. The piston 21 is connected to the crankshaft 25 via a connecting rod 23. Further, the engine body 3 is provided with a fuel injection device 27 called an injector. The fuel injection device 27 injects fuel (for example, gasoline) toward the combustion chamber 19 at a predetermined timing in accordance with a control signal from the ECU 11.

  In the cylinder head 17, an intake port 29 and an exhaust port 31 that are opened on the ceiling surface of the combustion chamber 19 are formed for each cylinder 13. The intake port 29 is provided with an intake valve 33 that opens and closes the opening on the combustion chamber 19 side. On the other hand, the exhaust port 31 is provided with an exhaust valve 35 for opening and closing the opening on the combustion chamber 19 side.

  The cylinder head 17 is further provided with an intake camshaft 34 that drives the intake valve 33 and an exhaust camshaft 36 that drives the exhaust valve 35. The intake camshaft 34 and the exhaust camshaft 36 are connected to the crankshaft 25 via a power transmission mechanism (not shown).

  The intake camshaft 34 rotates in conjunction with the crankshaft 25 to drive the intake valve 33 back and forth between an open position and a closed position. By this driving, the intake valve 33 opens and closes the intake port 29 at a predetermined timing. Similarly, the exhaust camshaft 36 rotates in conjunction with the crankshaft 25 to drive the exhaust valve 35 back and forth between an open position and a closed position. By this driving, the exhaust valve 35 opens and closes the exhaust port 31 at a predetermined timing.

  The cylinder head 17 includes an intake valve timing variable mechanism (VVT: Variable Valve Timing, hereinafter referred to as “intake VVT”) 37 for increasing or decreasing the rotation angle phase of the intake camshaft 34, and an exhaust camshaft 36. There is provided an exhaust valve timing variable mechanism (hereinafter referred to as “exhaust VVT”) 38 for advancing or retarding the rotation angle phase.

  The intake VVT 37 is configured using, for example, an electromagnetic valve. The opening / closing timing of the intake valve 33 is continuously changed according to the advance operation or the retard operation by the intake VVT 37. On the other hand, the exhaust VVT 38 is configured using, for example, a hydraulic solenoid valve. The opening / closing timing of the exhaust valve 35 is continuously changed according to the advance operation or retard operation by the exhaust VVT 38.

  The cylinder head 17 is provided with a spark plug 39 for igniting the air-fuel mixture in the combustion chamber 19 for each cylinder 13. The spark plug 39 generates a spark at a predetermined timing in accordance with a control signal from the ECU 11 and explosively burns the air-fuel mixture using the spark. By this explosion combustion, the piston 21 reciprocates in the cylinder 13, and the reciprocating motion of the piston 21 is converted into the rotational motion of the crankshaft 25 and output as torque (rotational power).

<Intake passage>
In the intake passage 5, in order from the upstream side, an air cleaner 40 that purifies the intake air by removing foreign matters such as dust contained in the air sucked from outside, a compressor 41 that boosts the intake air that passes through, and the intake air that passes through An intercooler 43 for cooling, a throttle valve 45 for adjusting the flow rate of intake air introduced into the engine body 3, and a surge tank 47 for temporarily storing intake air supplied to the engine body 3 are provided.

  The intake passage 5 is further provided with an intake bypass passage 49 that connects the downstream side and the upstream side of the compressor 41. The intake bypass passage 49 is provided with a bypass valve 51 that adjusts the flow rate of intake air flowing through the intake bypass passage 49. The bypass valve 51 is, for example, a so-called on / off valve that can switch the intake bypass passage 49 between a fully closed state and a fully opened state.

  The intake bypass passage 49 and the bypass valve 51 constitute a mechanism for circulating a part of the intake air supercharged by the compressor 41 to the upstream side of the compressor 41. The bypass valve 51 is opened according to a control signal from the ECU 11 when, for example, a phenomenon of intake backflow in the compressor 41 called surging is predicted to occur.

  The portion of the intake passage 5 downstream of the surge tank 47 is constituted by an intake manifold 52 having a plurality of independent intake passages branched for each cylinder 13 of the engine body 3, although not shown in detail. The surge tank 47 is included in the intake manifold 52.

<Exhaust passage>
In the exhaust passage 7, in order from the upstream side, a turbine 53 that is rotated by exhaust gas passing through, and harmful air pollution such as NOx (nitrogen oxide), CO (carbon monoxide), and HC (hydrocarbon) contained in the exhaust gas. An exhaust purification device 55 for purifying the substance is provided.

  The exhaust purification device 55 is formed by using, for example, two catalytic converters 61 that internally support an exhaust purification catalyst such as a three-way catalyst. The portion of the exhaust passage 7 upstream of the exhaust bypass passage 57 includes an exhaust manifold 60 having a plurality of independent exhaust passages branched for each cylinder 13 of the engine body 3, although not shown in detail.

  The exhaust passage 7 is further provided with an exhaust bypass passage 57 for bypassing the exhaust gas flowing through the exhaust passage 7 by bypassing the turbine 53. The exhaust bypass passage 57 is provided with a waste gate valve (hereinafter referred to as “WG valve”) 59 for adjusting the flow rate of the exhaust gas flowing through the exhaust bypass passage 57. The WG valve 59 is a so-called linear valve that can change the opening of the exhaust bypass passage 57 continuously or in multiple stages between a fully open state and a fully closed state.

<Turbocharger>
The turbocharger 8 includes the compressor 41 provided in the intake passage 5 and the turbine 53 provided in the exhaust passage 7. The compressor 41 and the turbine 53 are connected via a shaft and rotate integrally. In the turbocharger 8, when the turbine 53 rotates in response to the exhaust flow, the compressor 41 sends the intake air to the downstream side using the rotational force of the turbine 53, and compresses (supercharges) the intake air.

<External EGR mechanism>
The external EGR mechanism 9 circulates through the EGR passage 63 that recirculates part of the exhaust discharged to the exhaust passage 7 to the intake passage 5, the EGR cooler 65 that cools the exhaust recirculated through the EGR passage 63, and the EGR passage 63. And an EGR valve 67 for controlling the exhaust gas recirculation amount, that is, the EGR flow rate.

  The EGR passage 63 connects the intake manifold 52 and the exhaust manifold 60, and allows the manifolds 52 and 60 to communicate with each other. The EGR cooler 65 and the EGR valve 67 are provided in the EGR passage 63 in order from the upstream side (exhaust passage 7 side). The EGR valve 67 is a linear valve that can change the opening of the EGR passage 63 continuously or in multiple stages between a fully open state and a fully closed state.

<Sensors>
Sensors are provided in the engine main body 3, the intake passage 5, the exhaust passage 7, and the external EGR mechanism 9 described above.

  Specifically, in the engine body 3, a crank angle sensor 69 that detects the rotation angle of the crankshaft 25, a water temperature sensor 70 that detects an engine water temperature that is the temperature of engine cooling water in the water jacket, and an intake camshaft. An intake cam angle sensor 71 for detecting the cam angle 34 and an exhaust cam angle sensor 72 for detecting the cam angle of the exhaust camshaft 36 are provided.

  In the intake passage 5, an air flow sensor 73 is provided between the air cleaner 40 and the compressor 41 to detect the intake flow rate. The air flow sensor 73 has a built-in temperature sensor that detects the intake air temperature. Further, the intake air passage 5 between the compressor 41 and the throttle valve 45 and on the downstream side of the intercooler 43 has a first intake pressure that detects the pressure of the intake air compressed by the turbocharger 8, that is, the supercharging pressure. A sensor 75 is provided.

  The intake passage 5 is further provided with a throttle opening sensor 77 that detects the opening of the throttle valve 45. The intake passage 5 on the downstream side of the throttle valve 45, specifically the surge tank 47, is provided with a second intake pressure sensor 79 that detects the intake manifold pressure that is the pressure in the surge tank 47. The second intake pressure sensor 79 includes a temperature sensor that detects the intake manifold temperature, which is the temperature in the surge tank 47.

In the exhaust passage 7, a WG opening degree sensor 81 that detects the opening degree of the waste gate valve 59 is provided. Further, O ₂ sensors 83 and 85 are provided in the exhaust passage 7 between the turbine 53 and the exhaust purification device 55 and the exhaust passage 7 between the two catalytic converters 61, respectively. The detection values of these two O ₂ sensors 83 and 85 are used for feedback control of the air-fuel ratio in the combustion chamber 19.

  The external EGR mechanism 9 is provided with an EGR opening sensor 87 that detects the opening of the EGR valve 67. Further, the EGR passage 63 between the EGR cooler 65 and the EGR valve 67 is provided with an exhaust pressure sensor 89 that detects an EGR valve upstream pressure that is an exhaust pressure upstream of the EGR valve 67.

  In addition, the engine 1 includes an atmospheric pressure sensor 91 that detects the atmospheric pressure, a vehicle speed sensor 93 that detects the speed of the automobile, an accelerator sensor 95 that detects the accelerator opening according to the amount of depression of the accelerator pedal, and the like.

  The detected values of these various sensors 69 to 95 are output to the ECU 11 during driving of the automobile.

<ECU>
The ECU 11 is activated by a hardware such as an internal memory such as a CPU (Central Processing Unit), a ROM (Read Only Memory) or a RAM (Random Access Memory), a basic control program such as an OS (Operating System), and a specific function activated on the OS. And a computer configured with software including an application program that comprehensively controls the operation of the engine 1 including the opening degree control of the WG valve 59 based on the detection values of the sensors. The ECU 11 is an example of a control device for the engine 1.

FIG. 2 shows a functional configuration diagram of the ECU 11 with a focus on the portion related to the opening degree control of the WG valve 59. As shown in FIG. 2, the ECU 11 functionally exits the WG valve control unit 101 that controls the opening degree of the WG valve 59 and the exhaust port 31 of the fresh air introduced from the intake port 29 to the cylinder 13. A fresh air blow-through rate calculating unit 103 that calculates a fresh air blow-through rate Pt that is a ratio of fresh air, and a target filling efficiency setting that sets a target charging efficiency ηc _tar that is a target value of the charging efficiency according to the operating state of the engine 1 Unit 105 and a storage unit 107 for storing various data.

  The WG valve control unit 101 controls the opening degree of the WG valve 59 in accordance with control based on a target value of output torque required for the engine 1 (hereinafter referred to as “target torque”), that is, so-called torque base control. In the torque base control, including the opening of the WG valve 59, the opening of the throttle valve 45, the bypass valve 51 and the EGR valve 67, the ignition timing by the ignition plug 39, the opening and closing timing of the intake valve 33 and the exhaust valve 35, fuel injection The control value set in the control device such as the amount is variously changed so as to achieve the target torque.

  In such torque-based control, depending on the operating state of the engine 1, there may be a valve overlap that opens both the intake valve 33 and the exhaust valve 35 during the intake stroke. In such a case, fresh air taken into the cylinder 13 through the intake port 29 is discharged from the exhaust port 31 as it is. The valve overlap is set, for example, when it is desired to promote scavenging of the cylinder 13, to decrease the temperature of the cylinder 13, or to increase the flow rate of exhaust gas passing through the turbine 53.

  The opening control of the WG valve 59 in the torque base control will be described below with reference to FIG. FIG. 3 is a flowchart showing the opening degree control of the WG valve 59.

  As shown in FIG. 3, the WG valve control unit 101 first detects the operating state of the engine 1 (step S1). Specifically, the engine speed obtained from the detection value of the crank angle sensor 69, the vehicle speed detected by the vehicle speed sensor 93, the accelerator opening detected by the accelerator sensor 95, the gear ratio, and the like relate to the operating state of the engine 1. Information is read into the ECU 11.

  Next, the WG valve control unit 101 uses the information (accelerator opening degree, vehicle speed, gear ratio) regarding these driving states, refers to the acceleration map stored in advance in the storage unit 107, and determines the acceleration according to the accelerator opening degree. A target value (hereinafter referred to as “target acceleration”) is acquired (step S2). In the acceleration map, the accelerator opening and the vehicle speed and the acceleration corresponding to them are defined in association with each gear ratio. The target acceleration is set by comparing the accelerator opening, the vehicle speed, and the gear ratio with the acceleration map.

Subsequently, the WG valve control unit 101 acquires a target torque necessary for realizing the target acceleration based on the vehicle speed and the accelerator opening (step S3). Then, the WG valve control unit 101 acquires a target charging efficiency ηc _tar necessary for realizing the target torque (step S4). The target charging efficiency ηc _tar is set by the target charging efficiency setting unit 105 so as not to exceed an upper limit value (upper limit charging efficiency ηc _max ) variably set according to the engine speed. A method for setting the target charging efficiency ηc _tar will be described in detail later.

Next, the WG valve control unit 101 obtains a target boost pressure by referring to a boost pressure map stored in advance in the storage unit 107 based on the target charging efficiency ηc _tar and the engine speed (step) S5). In the supercharging pressure map, the target charging efficiency ηc _tar and the engine speed and the target supercharging pressure corresponding to them are defined in association with each other. The target supercharging pressure is set by comparing the target charging efficiency ηc _tar set by the target charging efficiency setting unit 105 and the engine speed with the supercharging pressure map.

  Furthermore, the WG valve control unit 101 acquires a target value of the flow rate of the exhaust gas passing through the turbine 53 (hereinafter referred to as “target turbine flow rate”) based on the target supercharging pressure (step S6). Specifically, the target turbine flow rate is acquired based on the target compressor output, which is the target value of the driving force of the compressor 41, the engine speed, and the like. The target compressor output is obtained based on the target boost pressure.

  Next, the WG valve control unit 101 sets a target WG opening that is a target value of the opening of the WG valve 59 necessary for realizing the target turbine flow rate (step S7). Specifically, the target WG opening is obtained based on the target turbine flow rate and the total exhaust flow rate. Then, the WG valve control unit 101 outputs a control signal for driving the opening degree of the WG valve 59 so that the opening degree of the WG valve 59 becomes the target WG opening degree, and controls the opening degree of the WG valve 59. (Step S8).

In the opening degree control of the WG valve 59 as described above, the target charging efficiency setting unit 105 calculates the upper limit charging efficiency ηc _max that is the upper limit value of the target charging efficiency ηc _tar according to the operating state of the engine 1, efficiency [eta] c _tar limits the target charging efficiency [eta] c _tar so as not to exceed the upper limit charging efficiency [eta] c _max. In order to calculate the upper limit charging efficiency ηc _max , the fresh air blow-through rate Pt calculated by the fresh air blow-through rate calculation unit 103 is required.

  The fresh air blow-off rate calculating unit 103 refers to a blow-through rate map stored in advance in the storage unit 107 and acquires a basic value of the fresh air blow-through rate Pt. In the blow-through rate map, the overlap amount (that is, the overlap period) and the intake pressure of the intake valve 33 and the exhaust valve 35 are defined in association with the basic value of the new air blow-through rate Pt corresponding thereto. The basic value of the new air blow-through rate Pt is acquired by comparing the overlap amount of the intake valve 33 and the exhaust valve 35 and the intake pressure with the blow-through rate map.

  Here, the intake manifold pressure detected by the second intake pressure sensor 79 is used as the intake pressure. The overlap amount of the intake valve 33 and the exhaust valve 35 is obtained from the opening / closing timing of the intake valve 33 and the opening / closing timing of the exhaust valve 35. The opening / closing timing of the intake valve 33 is obtained from the cam angle of the intake camshaft 34 detected by the intake cam angle sensor 71. The opening / closing timing of the exhaust valve 35 is obtained from the cam angle of the exhaust camshaft 36 detected by the exhaust cam angle sensor 72.

  The fresh air blow-off rate calculating unit 103 further refers to a correction map stored in advance in the storage unit 107 and acquires a correction term for the fresh air blow-through rate Pt. In the correction map, the engine speed and the correction term for the fresh air blow-through rate Pt corresponding thereto are defined in association with each other. The correction term for the fresh air blow-through rate Pt is acquired by comparing the engine speed with the correction map.

  Then, the fresh air blow-off rate calculating unit 103 calculates the fresh air blow-through rate Pt by multiplying the correction value thus acquired by the basic value of the fresh air blow-through rate Pt.

The target charging efficiency setting unit 105 includes a required charging efficiency calculation unit 109 that calculates a required charging efficiency ηc _req that is a required value of the charging efficiency according to a driving request from the driver, and an upper limit charging that calculates an upper limit charging efficiency ηc _max. An efficiency calculation unit 111.

  The required charging efficiency calculation unit 109 calculates the required charging efficiency based on the target torque, the engine speed, and the target indicated average effective pressure that is a target value of the indicated average effective pressure. The target indicated mean effective pressure is calculated based on the target torque, the mechanical resistance and the pump loss (pumping loss) that become torque loss.

The upper limit charging efficiency calculation unit 111 has a predetermined limit value Q _lim set in advance for the compressor passage flow rate that is the flow rate of the intake air passing through the compressor 41. The compressor passage flow rate is one of the parameters indicating the operation state of the compressor 41. A method for setting the limit value Q _{lim for} the compressor passage flow rate will be described below with reference to FIG. FIG. 4 is an image diagram of a compressor performance map.

  The turbocharger 8 has a compressor performance as shown in FIG. 4 as a compressor performance map.

  In the compressor performance map, a so-called surge region (a region with a diagonal line rising to the right) is defined in a region where the flow rate through the compressor is smaller than the surge line SL indicated by a broken line in FIG. The surge region is defined by the relationship between the compressor passage flow rate and the compressor pressure ratio. In this surge region, the compressor pressure ratio is too high with respect to the flow rate through the compressor, so that a phenomenon in which the intake air supercharged by the compressor 41 flows back to the compressor 41, so-called surging may occur.

  In the compressor performance map, a so-called choke region (a region with a diagonal line rising to the left) is defined in a region where the flow rate through the compressor is larger than the choke line CL indicated by the broken line in FIG. The choke region is defined by the flow rate through the compressor. In this choke region, a phenomenon called choke occurs in which the compressor 41 is over-rotated and the compressor flow rate is further restricted.

The compressor 41 is stably operated in an operation region between the surge line SL and the choke line CL. Further, the engine 1 has a compressor passage flow rate necessary to satisfy the output performance required in the WOT (Wide-Open Throttle) state. Therefore, the limit value Q _lim of the compressor passage flow rate is set between the compressor passage flow rate required in the WOT state and the compressor passage flow rate defining the choke line CL.

FIG. 5 is a block diagram showing a method for setting the target charging efficiency ηc _tar by the target charging efficiency setting unit 105. The upper limit charging efficiency calculation unit 111 sets the upper limit charging efficiency ηc _max variably according to the engine speed based on the limit value Q _lim of the compressor passage flow rate.

Specifically, as shown in FIG. 5, the upper limit charging efficiency calculation unit 111 first determines the compressor upstream pressure that is the pressure of the intake air upstream of the compressor 41 and the intake air temperature detected by the air flow sensor 73. Thus, the intake air density ρ _ia on the upstream side of the compressor 41 is calculated by the following equation (1).
ρ _ia = (1 ÷ T) × (P ÷ Ra) (1)
Here, “T” is the compressor upstream temperature (intake air temperature) [K]. “P” is the compressor upstream pressure [Pa]. The compressor upstream pressure corresponds to atmospheric pressure. For this reason, the atmospheric pressure detected by the atmospheric pressure sensor 91 is used as the compressor upstream pressure. “Ra” is the gas constant [J / K · mol] of air.

Next, the upper limit charging efficiency calculation unit 111 multiplies the intake air density ρ _ia thus calculated by the limit value Q _lim of the compressor passage flow rate described above, thereby _obtaining the maximum value that is the maximum value of the mass flow rate of the compressor passage flow rate. The mass flow rate M _comp is calculated.

Further, the upper limit charging efficiency calculation unit 111 converts the maximum mass flow rate M _comp into a cylinder flow rate that is a flow rate of intake air introduced into the cylinder 13 by the following equation (2) based on the engine speed. Then, the maximum cylinder flow rate M _cyl which is the maximum value of the cylinder flow rate is calculated.
M _cyl = M _comp ÷ (Rf _eng ÷ 30) (2)
Here, “Rf _eng ” is the engine speed.

Then, the upper limit charging efficiency calculation unit 111 sets the maximum cylinder flow rate M _cyl calculated in this manner to the air blow rate Pt or the standard state (the state defined by a predetermined temperature or pressure, the same applies hereinafter) The upper limit charging efficiency ηc _max is calculated by converting the charging efficiency into consideration in consideration of the density and the volume of the cylinder 13. More specifically, the upper limit charging efficiency calculation unit 111 subtracts the fresh air blow-through rate Pt calculated by the fresh air blow-off rate calculation unit 103 from 1, and thereby the new charge flow rate of fresh air charged into the cylinder 13. A gas filling amount V _ia is calculated. Then, the upper limit charging efficiency calculation unit 111 divides the fresh air charging flow rate V _ia by the air density in the standard state (about 1.2 kg [kg / m ³ ]) and the volume of the cylinder 13 respectively. Then, the upper limit filling efficiency ηc _max is calculated.

The target filling efficiency setting unit 105 compares the required filling efficiency ηc _req calculated by the required filling efficiency calculation unit 109 with the upper limit filling efficiency ηc _max calculated by the upper limit filling efficiency calculation unit 111, and the smaller of them Is set to the target charging efficiency ηc _tar . That is, when the required filling efficiency ηc _req is equal to or lower than the upper limit filling efficiency ηc _max , the required filling efficiency ηc _req is set to the target filling efficiency ηc _tar , and the required filling efficiency ηc _req is larger than the upper limit filling efficiency ηc _max In this case, the upper limit charging efficiency ηc _max is set to the target charging efficiency ηc _tar .

According to these goals charging efficiency [eta] c _tar setting method, since the target charging efficiency [eta] c _tar is set to the upper limit does not exceed the charging efficiency [eta] c _max achievable in accordance with the operating condition of the engine 1, the target charging efficiency [eta] c _The charging efficiency is not set so high that _tar cannot be realized even when the WG valve 59 is fully closed, and the period during which the WG valve 59 is fully closed is shortened.

  Therefore, according to the ECU 11 of the engine 1 according to this embodiment, it is possible to suppress the occurrence of misfire and the deterioration of fuel consumption due to the increase in exhaust pressure. In addition, since the compressor 41 is not required to have a work rate higher than the performance, the compressor 41 can be prevented from over-rotating, and the controllability of the supercharging pressure can be prevented from being significantly deteriorated. As a result, the reliability of the turbocharger 8 can be ensured, the operation control of the engine 1 can be stabilized, and the drivability and fuel consumption of the automobile can be prevented from deteriorating.

  As described above, a preferred embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments in which changes, replacements, additions, omissions, and the like have been made as appropriate. Moreover, it is also possible to combine each component demonstrated by the said embodiment into a new embodiment. In addition, the constituent elements described in the accompanying drawings and the detailed description may include constituent elements that are not essential for solving the problem. For this reason, it should not be immediately recognized that these non-essential components are essential because they are described in the accompanying drawings and detailed description.

  For example, the following embodiment may be configured as follows.

In the above embodiment, the upper limit charging efficiency ηc _max is set based on a certain limit value Q _lim preset for the compressor passage flow rate, but this is not limitative. The limit value Q _lim may be a variable value that is changed depending on other parameters. Further, the upper limit charging efficiency ηc _max may be variably set according to the operating state of the engine 1 with reference to a parameter different from the compressor passage flow rate.

  Moreover, although the said embodiment demonstrated the example calculated | required by what is called a L-Jetronic system which makes a compressor flow volume the detection value of the airflow sensor 73, it does not restrict to this. The compressor passage flow rate includes the opening degree of the throttle valve 45 detected by the throttle opening degree sensor 77, the supercharging pressure detected by the first intake pressure sensor 75, and the intake manifold pressure detected by the second intake pressure sensor 79. Further, it may be obtained by a so-called D Jetronic method that is calculated based on the intake manifold temperature.

  As described above, the technique disclosed herein is useful for an engine control device including a turbocharger.

DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Engine body, 5 ... Intake passage, 7 ... Exhaust passage, 8 ... Turbocharger,
9 ... External EGR mechanism, 11 ... ECU (engine control device), 13 ... Cylinder,
15 ... Cylinder block, 17 ... Cylinder head, 19 ... Combustion chamber, 21 ... Piston,
23 ... Connecting rod, 25 ... Crankshaft, 27 ... Fuel injection device,
29 ... Intake port, 31 ... Exhaust port, 33 ... Intake valve, 34 ... Intake camshaft,
35 ... Exhaust valve, 36 ... Exhaust camshaft, 37 ... Intake VVT, 38 ... Exhaust VVT,
39 ... Spark plug, 40 ... Air cleaner, 41 ... Compressor,
43 ... Intercooler, 45 ... Throttle valve, 47 ... Surge tank,
49 ... Intake bypass passage, 51 ... Bypass valve, 52 ... Intake manifold,
53 ... Turbine, 55 ... Exhaust gas purification device, 57 ... Exhaust gas bypass passage,
59 ... Waste gate valve, 60 ... Exhaust manifold, 61 ... Catalytic converter,
63 ... EGR passage, 65 ... EGR cooler, 67 ... EGR valve,
69 ... Crank angle sensor, 70 ... Water temperature sensor, 71 ... Intake cam angle sensor,
72 ... Exhaust cam angle sensor, 73 ... Air flow sensor, 75 ... First intake pressure sensor,
77 ... Throttle opening sensor, 79 ... Second intake pressure sensor, 81 ... WG opening sensor,
83, 85 ... O ₂ sensor, 87 ... EGR opening sensor, 89 ... Exhaust pressure sensor,
91 ... Atmospheric pressure sensor, 93 ... Vehicle speed sensor, 95 ... Accelerator sensor,
101 ... WG valve control unit, 103 ... New air blowout rate calculation unit,
105 ... target filling efficiency setting unit, 107 ... storage unit, 109 ... required filling efficiency calculation unit,
111 ... upper limit filling efficiency calculation unit

Claims (3)

A turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and a wastegate valve provided in a bypass passage that bypasses the turbine in the exhaust passage. And
A target charging efficiency setting unit that sets a target charging efficiency that is a target value of the charging efficiency of the engine;
A valve control unit for controlling the opening degree of the waste gate valve based on the target filling efficiency,
The target filling efficiency setting unit is
Having a limit value of the compressor passage flow rate, which is the flow rate of the intake air passing through the compressor, and
The upper limit value of the target charging efficiency according to the engine operating state is calculated using the limit value and the intake air density set based on the upstream pressure of the compressor, and the target charging efficiency is the upper limit value. An engine control device that limits the target charging efficiency so as not to exceed. The engine control device according to claim 1,
The target charging efficiency setting unit sets an upper limit value of the target charging efficiency variably according to the engine speed. A turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and a wastegate valve provided in a bypass passage that bypasses the turbine in the exhaust passage. And
A target charging efficiency setting unit that sets a target charging efficiency that is a target value of the charging efficiency of the engine;
A valve control unit for controlling the opening degree of the waste gate valve based on the target filling efficiency,
The target charging efficiency setting unit calculates an upper limit value of the target charging efficiency according to an operating state of the engine, and limits the target charging efficiency so that the target charging efficiency does not exceed the upper limit value,
The target charging efficiency setting unit also sets an upper limit value of the target charging efficiency variably according to the engine speed,
The target charging efficiency setting unit further has a limit value of a compressor passing flow rate that is a flow rate of intake air passing through the compressor, and sets an upper limit value of the target charging efficiency based on the limit value. Engine control device.

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