JP5182139B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine.

  There is a cooling device for cooling the exhaust of an internal combustion engine. Some cooling devices are provided between an exhaust port of an internal combustion engine and an exhaust manifold, and others are provided around the exhaust manifold (see Patent Document 1). As the refrigerant flows through the cooling device, the exhaust is cooled.

JP-A 63-208607

  The refrigerant flowing in the cooling device is radiated by a radiator or the like. However, if the cooling water is not sufficiently dissipated by the radiator due to the operating conditions and conditions of the internal combustion engine, the cooling efficiency of the exhaust may be reduced.

  An object of the present invention is to provide a control device for an internal combustion engine in which a decrease in exhaust cooling efficiency is suppressed.

  The object is to provide a cooling device that is provided on a path through which the refrigerant flows and that cools the exhaust gas of the internal combustion engine by circulating the refrigerant, and the amount of heat that is transferred from the exhaust gas to the cooling water in the cooling device. This can be achieved by a control device for an internal combustion engine that includes a heat amount estimation unit that estimates and an engine control unit that determines whether or not to execute exhaust temperature suppression control that suppresses the temperature of the exhaust gas according to the heat amount.

  Depending on the amount of heat transferred from the exhaust gas to the cooling water in the cooling device, whether or not to execute the control for suppressing the exhaust temperature is determined. For example, when the estimated heat amount is equal to or greater than the threshold value, the exhaust temperature is suppressed. By doing so, the amount of heat transferred from the exhaust to the cooling water can be suppressed. As a result, the temperature of the cooling water can be reduced, and a reduction in the cooling efficiency of the exhaust can be prevented.

  The said structure WHEREIN: The said heat quantity estimation part can employ | adopt the structure which estimates the integrated heat amount which integrated | accumulated the heat amount transmitted from the said exhaust_gas | exhaustion to the said cooling water over predetermined time.

  In the above-described configuration, a radiator disposed on the refrigerant path is provided, and the engine control unit estimates a heat radiation allowable heat amount that is radiated from the refrigerant by the radiator, and depends on the heat amount and the heat radiation allowable heat amount. A configuration for determining whether or not to execute the exhaust gas temperature suppression control can be adopted.

  In the above-described configuration, a radiator disposed on the refrigerant path is provided, and the engine control unit estimates a heat radiation allowable heat amount that is radiated from the refrigerant by the radiator, and depends on the integrated heat amount and the heat radiation allowable heat amount. Thus, it is possible to adopt a configuration that determines whether or not to execute the exhaust gas temperature suppression control.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine by which the fall of the cooling efficiency of exhaust_gas | exhaustion was suppressed can be provided.

FIG. 1 is an explanatory diagram of an embodiment of a control device for an internal combustion engine. FIG. 2 is a diagram illustrating a path of cooling water. FIG. 3 is a flowchart showing an example of control executed by the ECU. FIG. 4 is a timing chart showing a case where the exhaust gas temperature suppression control is executed. FIG. 5 is a timing chart showing a case where the exhaust gas temperature suppression control is executed based on the integrated heat quantity.

  Embodiments will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram of an embodiment of a control device for an internal combustion engine. The engine 10 has a pair of banks 12L and 12R. The banks 12L and 12R are arranged to be inclined with respect to each other. The engine 10 is a so-called V-type engine. The bank 12L has a cylinder group including three cylinders 14L. Similarly, the bank 12R has a cylinder 14R.

  The bank 12L is provided with a fuel injection valve 15L that directly injects fuel into the cylinder 14L. Similarly, the bank 12R is also provided with a fuel injection valve 15R that directly injects fuel into the cylinder 14R. An intake passage 4L and an exhaust manifold 5L are connected to the bank 12L, and an intake passage 4R and an exhaust manifold 5R are connected to the bank 12R. The intake passages 4L and 4R merge on the upstream side, and a throttle valve 6 for adjusting the intake air amount and an air flow meter 18 for detecting the intake air amount are provided at the merged portion.

  Catalysts 20L and 20R are provided at the lower ends of the exhaust manifolds 5L and 5R, respectively. The catalysts 20L and 20R purify the exhaust discharged from the cylinders on the banks 12L and 12R side, respectively. Air-fuel ratio sensors 9L and 9R are attached to the exhaust manifolds 5L and 5R, respectively.

  A cooling device 40L is provided between the exhaust port (not shown) of the bank 12L and the exhaust manifold 5L. Similarly, a cooling device 40R is provided between the exhaust port (not shown) of the bank 12R and the exhaust manifold 5R. The cooling devices 40L and 40R correspond to cooling devices.

  The cooling devices 40L and 40R are configured such that cooling water flows around the pipes of the exhaust manifolds 5L and 5R, respectively. The cooling devices 40L and 40R will be described later in detail. Temperature sensors 9aL and 9bL are provided in the exhaust manifold 5L so as to sandwich the cooling device 40L. The temperature sensor 9bL is disposed upstream of the cooling device 40L, and the temperature sensor 9aL is disposed downstream of the cooling device 40L. Similarly, temperature sensors 9aR and 9bR are arranged in the exhaust manifold 5R.

  The opening degree of the throttle valve 6 is individually controlled for each of the banks 12L and 12R by ECUs (Electronic Control Units) 7L and 7R. Further, the amount of fuel injected from the fuel injection valves 15L and 15R is also individually controlled by the ECUs 7L and 7R. The ECUs 7L and 7R can cut the fuel injected from the fuel injection valves 15L and 15R. The ECUs 7L and 7R correspond to a heat quantity estimation unit and an engine control unit, which will be described in detail later.

  The air-fuel ratio sensors 9L and 9R output detection signals corresponding to the exhaust air-fuel ratio to the ECUs 7L and 7R, respectively. The ECUs 7L and 7R perform feedback control of the air-fuel ratio by controlling the fuel injection amounts to the cylinders 14L and 14R based on the outputs from the air-fuel ratio sensors 9L and 9R, respectively. The feedback control is to control the fuel injection amount so that the detected air-fuel ratio of the exhaust gas becomes the target air-fuel ratio. The ECUs 7L and 7R can communicate bidirectionally via the communication line 8. By exchanging information via the communication line 8, the ECUs 7 </ b> L and 7 </ b> R can refer to information related to operation states of other banks for operation control of the banks in charge.

  The temperature sensors 9aL, 9bL, 9aR, 9bR output detection signals corresponding to the exhaust temperature to the ECUs 7L, 7R, respectively. Based on the signal from the temperature sensor 9bL, the ECU 7L detects the temperature of the exhaust before being cooled by the cooling device 40L, that is, the temperature of the exhaust before flowing into the cooling device 40L. Further, based on a signal from the temperature sensor 9aL, the ECU 7L detects the temperature of the exhaust after being cooled by the cooling device 40L, that is, the temperature of the exhaust after flowing out of the cooling device 40L. Similarly, the ECU 7R detects the exhaust temperature before and after the inflow of the cooling device 40R.

  FIG. 2 is a diagram illustrating a path of cooling water (refrigerant). As shown in FIG. 2, a radiator 72, an inlet 74, a pump 76, and the like are arranged on the cooling water path. The main path 82 circulates cooling water in the order of the inlet 74, the pump 76, the engine 10, and the radiator 72. The main path 82 circulates cooling water from the rear joint portion 19 of the engine 10 to the radiator 72. The auxiliary path 88 circulates cooling water in the order of the inlet 74, the pump 76, the engine 10, the cooling devices 40L and 40R, and the V bank pipe 60. The auxiliary path 88 includes branch paths 86L and 86R that branch from the rear joint portion 19 and allow cooling water to flow through the cooling devices 40L and 40R, respectively.

  The pump 76 is electric and operates based on commands from the ECUs 7L and 7R. The cooling water flows from the inlet 74 to the engine 10. The cooling water first flows into the block-side water jacket 11w of the engine 10, and then flows into the head-side water jackets 12Lw and 12Rw. The cooling water discharged from the head side water jackets 12 </ b> Lw and 12 </ b> Rw joins at the rear joint unit 19. A main path 82 and an auxiliary path 88 are connected to the rear joint portion 19. The cooling water flowing through the main path 82 flows from the rear joint portion 19 to the radiator 72, and the cooling water radiates heat at the radiator 72.

  A flow sensor 34L and a cooling device 40L are arranged on the branch path 86L. Cooling water flows through the cooling device 40L. When the cooling water flows through the cooling device 40L, the temperature of the exhaust discharged from the cylinder 14L of the bank 12L can be lowered. The same applies to the branch path 86R, the flow sensor 34R, and the cooling device 40R.

  Water temperature sensors 52L and 54L are respectively arranged before and after the cooling device 40L. Similarly, water temperature sensors 52R and 54R are arranged before and after the cooling device 40R, respectively. The water temperature sensors 52L and 54L output detection signals to the ECU 7L, and the water temperature sensors 52R and 54R output detection signals to the ECU 7R. The ECU 7L can detect the temperature of the cooling water before flowing into the cooling device 40L based on the output from the water temperature sensor 52L, and can detect the temperature of the cooling water flowing out of the cooling device 40L based on the output from the water temperature sensor 54L. Similarly, the ECU 7R can detect the temperature of the cooling water before flowing into the cooling device 40R and the temperature of the cooling water after flowing out based on the outputs from the water temperature sensors 52R and 54R.

  The ECUs 7L and 7R determine the state of the cooling water in the cooling devices 40L and 40R according to the outputs from the water temperature sensors 52L, 54L, 52R and 54R, and change the operating state of the engine 10 according to the determination result. Below, the control which ECU7L and 7R perform is demonstrated.

  FIG. 3 is a flowchart showing an example of control executed by the ECUs 7L and 7R. The ECUs 7L and 7R detect the temperature of the cooling water based on the outputs from the water temperature sensors 52L, 54L, 52R and 54R, and further detect the flow rate of the cooling water based on the outputs from the flow sensors 34L and 34R ( Step S1).

  Specifically, the ECU 7L detects the temperature TLin before inflow and the temperature TLout after outflow output from the water temperature sensor 54L based on the output from the water temperature sensor 52L. The ECU 7R detects the temperature TRin before inflow and the temperature TRout after outflow output from the water temperature sensor 54R based on the output from the water temperature sensor 52R. Further, the ECU 7L detects the flow rate QL of the cooling water flowing into the cooling device 40L based on the output from the flow rate sensor 34L. The ECU 7R detects the flow rate QR of the cooling water flowing into the cooling device 40R based on the output from the flow sensor 34R.

  Next, the ECUs 7L and 7R estimate the amount of heat Qa to be transferred from the exhaust gas to the cooling water in the cooling devices 40L and 40R, respectively (step S2). The ECUs 7L and 7R correspond to a heat quantity estimation unit. The amount of heat Qa is estimated using the following equation.

  Qa = kL * (TLout−TLin) * QL + kR * (TRout−TRin) * QR (1)

  In the above equation (1), kL and kR are correction coefficients. The correction coefficients kL and kR are values determined in consideration of the surface area, heat transfer coefficient, heat conductivity, and exhaust pipe thickness of the exhaust system, respectively. The surface area of the exhaust system is, for example, the surface area of the pipe of the exhaust manifold 5L exposed to the cooling water in the cooling device 40L. The heat transfer coefficient is, for example, the heat transfer coefficient of the exhaust manifold 5L. The heat conductivity is, for example, the heat transfer coefficient of cooling water. The thickness of the exhaust pipe is, for example, the thickness of the pipe of the exhaust manifold 5L in the cooling device 40L.

  Next, the ECUs 7L and 7R estimate the heat radiation allowable heat amount Qmax (step S3). The heat radiation allowable heat amount Qmax is determined using the following equation.

  Qmax = k * (Tα−Ta) * S (2)

  In the above formula (2), Tα is the upper limit temperature of the cooling water obtained from the operating state of the engine 10. The upper limit temperature Tα is calculated based on, for example, a map stored in advance in one of the ECUs 7L and 7R. In this map, for example, the upper limit temperature Tα of the cooling water is associated with the engine speed, the engine load, and the like. The upper limit temperature Tα of the cooling water is set to an upper limit that does not hinder the operation of the engine 10.

  Ta is the outside air temperature. The outside air temperature Ta may be calculated based on, for example, an outside air temperature sensor (not shown) mounted on the vehicle, or may be estimated by other known estimation methods. S is a heat dissipation area where the radiator 72 is exposed to the outside air and the cooling water is dissipated. k is a correction coefficient determined in consideration of heat transfer coefficient, heat conductivity, vehicle speed, and the like. The correction coefficient k may be changed according to the vehicle speed. For example, the correction coefficient k may be increased as the vehicle speed increases. The heat radiation allowable heat quantity Qmax is the heat quantity that the cooling water can radiate to the outside air by the radiator 72. The amount of heat that can be radiated by the radiator 72 varies depending on the vehicle speed and the like. According to the above equation (2), the higher the outside air temperature Ta or the smaller the heat radiation area S of the radiator 72, the smaller the heat radiation allowable heat amount Qmax.

  Next, the ECUs 7L and 7R determine whether or not the heat quantity Qa exceeds the heat radiation allowable heat quantity Qmax (step S4). When the heat quantity Qa is less than the heat radiation allowable heat quantity Qmax, the ECUs 7L and 7R end this series of controls. When the heat quantity Qa exceeds the heat radiation allowable heat quantity Qmax, the ECUs 7L and 7R execute exhaust temperature suppression control (step S5).

  The exhaust gas temperature suppression control is to control to the rich side by controlling the fuel injection amount as compared with the air-fuel ratio at the time of normal feedback control. Thereby, the rise in exhaust temperature is suppressed. Further, the exhaust temperature suppression control may be control that suppresses an increase in the exhaust temperature by limiting the intake air amount. For example, the intake air amount is controlled so that the opening degree of the throttle valve 6 is less than a certain value. Thereby, since the amount of oxygen burned decreases, the temperature rise of exhaust gas is suppressed.

  By suppressing the exhaust gas temperature, it is possible to suppress the amount of heat transferred from the exhaust gas to the cooling water in the cooling devices 40L and 40R. As a result, the cooling water can be maintained at a heat quantity that can be radiated by the radiator 72. As described above, a reduction in exhaust cooling efficiency is suppressed.

  FIG. 4 is a timing chart showing a case where the exhaust gas temperature suppression control is executed. Although the heat radiation allowable heat amount Qmax varies depending on the operation state, the exhaust temperature suppression control is executed only when the heat amount Qa exceeds the heat radiation allowable heat amount Qmax. Thereby, the deterioration of the emission accompanying execution of exhaust temperature suppression control can be suppressed.

  Next, a modified example of estimating the amount of heat transferred from the exhaust to the cooling water will be described. The ECUs 7L and 7R estimate the integrated heat quantity ΣQa by integrating the heat quantity Qa estimated by the above equation (1) over a predetermined time. The ECUs 7L and 7R execute the exhaust temperature suppression control only when the integrated heat quantity ΣQa exceeds the heat radiation allowable heat quantity Qmax. FIG. 5 is a timing chart showing a case where the exhaust gas temperature suppression control is executed based on the integrated heat quantity. By determining whether or not the exhaust temperature suppression control can be executed based on the integrated heat quantity, it is possible to prevent the exhaust temperature suppression control from being repeatedly executed and stopped in a short period of time. Thereby, deterioration of drivability is suppressed.

  Next, a modification of the method for estimating the heat quantity Qa will be described. Below, the modification of the type | formula which estimates calorie | heat amount Qa is described.

  Qa = kvL * (TvLout−TvLin) * QvL + kvR * (TvRout−TvRin) * QvR (3)

  The above equation (3) is an equation for estimating the heat quantity Qa from the exhaust gas temperature. kvL and kvR are correction coefficients. The correction coefficients kvL and kvR are values determined in consideration of the exhaust system surface area, heat transfer coefficient, heat conductivity, and exhaust pipe thickness, respectively.

  TvLout is the temperature of the exhaust gas that has passed through the cooling device 40L, and is detected by the temperature sensor 9aL. TvLin is the temperature of the exhaust gas before passing through the cooling device 40L, and is detected by the temperature sensor 9bL. TvRout is the temperature of the exhaust gas that has passed through the cooling device 40R, and is detected by the temperature sensor 9aR. TvRin is the temperature of the exhaust gas before passing through the cooling device 40R, and is detected by the temperature sensor 9bR. QvL and QvR indicate the flow rates of the exhaust gas flowing into the cooling devices 40L and 40R, respectively. The exhaust flow rates QvL and QvR are detected by the ECUs 7L and 7R based on outputs from exhaust flow sensors (not shown) provided in the exhaust manifolds 5L and 5R, respectively. The exhaust flow sensor is a known sensor. The above formula (3) is useful when a water temperature sensor that detects the temperature of the cooling water before and after flowing into the cooling devices 40L and 40R cannot be provided.

  Next, a method for estimating the heat quantity Qa without detecting the exhaust flow rate will be described. By using the following equation, the heat quantity Qa can be estimated without detecting the exhaust flow rate.

  Qa = kvL * (TvLout−TvLin) * Ga / 2 + kvR * (TvRout−TvRin) * Ga / 2 (4)

  In the above formula (4), Ga is the amount of intake air. In the above equation (4), it is assumed that half of the intake air amount Ga detected by the air flow meter 18 is introduced into the banks 12L and 12R, respectively, and the intake air amount Ga and the exhaust flow rate are proportional. The above formula (4) is useful when an exhaust flow sensor cannot be provided.

  Next, a method for estimating the heat quantity Qa without detecting the exhaust temperature before flowing into the cooling devices 40L and 40R will be described. By using the following equation, the heat quantity Qa can be estimated without detecting the exhaust temperature before flowing into the cooling devices 40L and 40R.

  Qa = kvL * (TvLout−Tv0) * QvL + kvR * (TvRout−Tv0) * QvR (5)

  Tv0 is the exhaust temperature estimated from the operating conditions of the engine 10. For example, the ECUs 7L and 7R estimate the exhaust gas temperature Tv0 based on a map in which the exhaust gas temperature is associated with the engine speed, the fuel injection amount, the load, and the like. This is useful when the temperature sensors 9bL and 9bR cannot be provided.

  Next, a method for estimating the heat quantity Qa without detecting the exhaust gas flow rate and the exhaust gas temperature before flowing into the cooling devices 40L and 40R will be described. By using the following equation, the heat quantity Qa can be estimated without detecting the exhaust gas flow rate and the exhaust gas temperature before flowing into the cooling devices 40L and 40R.

  Qa = kvL * (TvLout−Tv0) * Ga / 2 + kvR * (TvRout−Tv0) * Ga / 2 (5)

  This is useful when the sensor for detecting the exhaust flow rate or the temperature sensors 9bL and 9bR cannot be provided.

  The ECUs 7L and 7R estimate the integrated heat quantity ΣQa by integrating over a predetermined period using the above equations (3) to (5), and compare with the heat radiation allowable heat amount Qmax estimated by the above equation (2). Accordingly, it may be determined whether or not the exhaust temperature suppression control can be executed.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

7L, 7R ECU
12L, 12R Bank 5L, 5R Exhaust manifold 6 Throttle valve 9L, 9R Air-fuel ratio sensor 9aL, 9bL, 9aR, 9bR Temperature sensor 10 Engine 14L, 14R Cylinder 15L, 15R Fuel injection valve 18 Air flow meter 20L, 20R Catalyst 40L, 40R Cooling Equipment 52L, 52R, 54L, 54R Water temperature sensor 82 Main path 88 Auxiliary path

Claims (4)

A cooling device that is provided on a path through which the refrigerant flows and that cools the exhaust of the internal combustion engine by circulating the refrigerant inside;
A heat quantity estimating unit for estimating a heat quantity transferred from the exhaust to the cooling water in the cooling device;
An internal combustion engine control apparatus comprising: an engine control unit that determines whether or not to execute exhaust temperature suppression control that suppresses the temperature of the exhaust gas according to the amount of heat.   2. The control device for an internal combustion engine according to claim 1, wherein the heat quantity estimation unit estimates an integrated heat quantity obtained by integrating a heat quantity transmitted from the exhaust gas to the cooling water over a predetermined time. A radiator disposed on the refrigerant path;
The engine control unit estimates a heat radiation allowable heat amount to which the refrigerant is radiated by the radiator, and determines whether or not to execute the exhaust temperature suppression control according to the heat amount and the heat radiation allowable heat amount. The control apparatus for an internal combustion engine according to claim 1. A radiator disposed on the refrigerant path;
The engine control unit estimates a heat radiation allowable heat amount to which the refrigerant is radiated by the radiator, and determines whether or not to execute the exhaust temperature suppression control according to the integrated heat amount and the heat radiation allowable heat amount. The control apparatus for an internal combustion engine according to claim 2, wherein the control apparatus is an internal combustion engine.

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