JP2015045296A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an excess rise of temperatures of an electric actuator and its drive circuit while suppressing lowering of drivability, in an internal combustion engine having a VCR mechanism.SOLUTION: When a drive system temperature Tmot of a VCR mechanism reaches a limit temperature TLmot1, a manipulated variable of an electric actuator is limited as a first stage of fail motion. When an engine temperature Teng reaches a limit temperature TLeng1, or when the drive system temperature Tmot reaches a limit temperature TLmot2 (>TLmot1), a limit range of a compression ratio is limited as a second stage of the fail motion. When the drive system temperature Tmot reaches a limit temperature TLmot3 (>TLmot2), the electric actuator is stopped as a third stage of the fail motion. When the engine temperature Teng reaches a limit temperature TLeng2 (>TLeng1), an output of an internal combustion engine is limited.

Description

  The present invention relates to a control device for an internal combustion engine having a variable compression ratio (VCR) mechanism.

  In an internal combustion engine equipped with a VCR mechanism, for example, if the compression ratio is frequently changed according to the engine operating state, the electric power consumed by the electric actuator increases, and the electric actuator and its drive circuit may excessively generate heat. is there. In addition, since the compression ratio of the VCR mechanism is variable by the link mechanism, if the temperature of the link mechanism rises excessively as the ambient temperature rises, the clearance between the links in the link connecting portion becomes small, and the link connecting portion There is a risk of sticking. For this reason, as described in Japanese Patent Application Laid-Open No. 2009-185629 (Patent Document 1), a technique for prohibiting a change in the compression ratio when the temperature of the electric actuator exceeds a limit temperature has been proposed.

JP 2009-185629 A

  However, if the change of the compression ratio is prohibited when the temperature of the electric actuator exceeds the limit temperature, the compression ratio cannot be changed until the temperature condition permitting the change of the compression ratio is satisfied. There was a risk of lowering.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that prevents the temperature of an electric actuator and its drive circuit from excessively rising while suppressing a decrease in drivability.

  Therefore, in the present invention, in an internal combustion engine provided with a VCR mechanism in which the compression ratio is variable by the electric actuator, when the temperature of the internal combustion engine exceeds a predetermined temperature, the drive current supplied to the electric actuator is reduced.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the temperature of an electric actuator and its drive system rises excessively, suppressing the fall of drivability.

1 is a system diagram illustrating an example of an internal combustion engine for a vehicle. It is a flowchart which shows an example of a control program. It is explanatory drawing of the map which sets a limit temperature dynamically. It is explanatory drawing of the map which sets the control range of a compression ratio dynamically. It is explanatory drawing of the map which sets the maximum operation amount dynamically. It is explanatory drawing of the content restrict | limited according to engine temperature and drive system temperature.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an internal combustion engine for a vehicle.

  The internal combustion engine 1 includes a cylinder block 2, a piston 4 fitted in a cylinder bore 3 of the cylinder block 2 so as to be reciprocally movable, a cylinder head 10 in which an intake port 5 and an exhaust port 6 are formed, an intake port 5 and an exhaust port. An intake valve 7 and an exhaust valve 8 that open and close the opening end of the port 6 are provided.

  The piston 4 is connected to the crankshaft 9 via a connecting rod (connecting rod) 13 including a lower link 11 and an upper link 12. A combustion chamber 14 is formed between the crown surface 4 a of the piston 4 and the lower surface of the cylinder head 10. A spark plug 15 is attached to substantially the center of the cylinder head 10 forming the combustion chamber 14.

  The internal combustion engine 1 also includes a variable valve lift mechanism 21 that makes the valve lift amount and operating angle of the intake valve 7 variable, a variable valve timing mechanism 22 that makes the phase of the intake valve 7 open relative to the crankshaft 9 variable, The VCR mechanism 23 that changes the compression ratio by changing the top dead center position of the piston 4 is provided.

  For example, as disclosed in Japanese Patent Application Laid-Open No. 2003-172112, the variable valve lift mechanism 21 changes the angular position of the control shaft by an actuator such as an electric motor, thereby increasing the maximum valve lift amount of the intake valve 7. Increase or decrease. The variable valve lift mechanism 21 increases or decreases the operating angle (open period angle) in conjunction with an increase or decrease in the maximum valve lift amount.

  The variable valve timing mechanism 22 changes the phase of the intake camshaft 24 with respect to the crankshaft 9 to advance or retard the central phase of the operating angle while keeping the operating angle of the intake valve 7 constant.

  The VCR mechanism 23 changes the compression ratio of the internal combustion engine 1 by changing the top dead center position of the piston 4 with a structure disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-276446. Hereinafter, an example of the VCR mechanism 23 will be described.

  The crankshaft 9 has a plurality of journal portions 9 a and a crankpin portion 9 b, and the journal portion 9 a is rotatably supported by a main bearing (not shown) of the cylinder block 2. The crankpin portion 9b is eccentric from the journal portion 9a, and the lower link 11 is rotatably connected thereto. The upper link 12 is rotatably connected to one end of the lower link 11 by a connecting pin 25 at the lower end side, and is rotatably connected to the piston 4 by a piston pin 26 at the upper end side. The control link 27 is pivotally connected to the other end of the lower link 11 by a connecting pin 28 at the upper end side, and is pivotally connected to the lower part of the cylinder block 2 via the control shaft 29 at the lower end side. Specifically, the control shaft 29 is rotatably supported by the engine body (cylinder block 2) and has an eccentric cam portion 29a that is eccentric from the center of rotation. A lower end part fits rotatably. The rotation position of the control shaft 29 is controlled by a compression ratio control actuator 30 using an electric motor. Here, the compression ratio control actuator 30 is an example of an electric actuator.

  In the VCR mechanism 23 using such a multi-link type piston-crank mechanism, when the control shaft 29 is rotated by the compression ratio control actuator 30, the center position of the eccentric cam portion 29a, that is, the engine body (cylinder block) The relative position with respect to 2) changes. As a result, when the swing support position at the lower end of the control link 27 changes, the stroke of the piston 4 changes, and the position of the piston 4 at the piston top dead center (TDC) becomes higher or lower. The compression ratio is changed. At this time, when the operation of the compression ratio control actuator 30 is stopped, the control link 27 is rotated with respect to the eccentric cam portion 29a of the control shaft 29 by the reciprocation of the piston 4, and the compression ratio is shifted to the low compression ratio side. To do.

An electronic control throttle 41 that adjusts the intake air amount of the internal combustion engine 1 by changing the opening area of the intake system is disposed in the intake system of the internal combustion engine 1.
The variable valve lift mechanism 21, the variable valve timing mechanism 22, the VCR mechanism 23, the electronic control throttle 41, and the power transistor 43 that controls the current flowing to the primary side of the ignition coil are controlled by a control device 31 incorporating a computer. It is controlled according to the operating state of the internal combustion engine 1 and the like.

  The control device 31 includes an engine temperature sensor 32 that detects the temperature (engine temperature) Teng of the internal combustion engine 1, a drive system temperature sensor 33 that detects the temperature (drive system temperature) Tmot of the compression ratio control actuator 30, and a vehicle speed VSP. Signals of the vehicle speed sensor 34 that performs the detection and the outside temperature sensor 35 that detects the outside temperature TO are input.

  The engine temperature sensor 32 is, for example, a temperature sensor attached to the internal combustion engine 1 and directly detects the temperature of the internal combustion engine 1. The engine temperature sensor 32 may be a temperature sensor that has a high correlation with the engine temperature, for example, a lubricant temperature or a coolant temperature of the internal combustion engine 1.

  The drive system temperature sensor 33 is, for example, a temperature sensor attached to the compression ratio control actuator 30 and directly detects the temperature of the compression ratio control actuator 30 that is a part of the drive system of the VCR mechanism 23. The drive system temperature sensor 33 may estimate the temperature from a drive current supplied to the compression ratio control actuator 30, for example. The drive system temperature sensor 33 is not limited to detecting or estimating the temperature of the compression ratio control actuator 30, but is a temperature sensor that directly detects the temperature of the drive circuit, and a drive current supplied to the compression ratio control actuator 30. The temperature may be estimated, or the temperature of the compression ratio control actuator 30 and its drive circuit may be detected or estimated.

  The vehicle speed sensor 34 is, for example, a sensor that outputs a pulse proportional to the rotational speed of the output shaft of a transmission (not shown). The outside air temperature sensor 35 is a sensor that detects the temperature of the engine room (engine room). For example, the output of a hot-wire air flow meter that detects the intake air flow rate can also be used.

  Then, the control device 31 diagnoses whether or not there is a possibility that the VCR mechanism 23 and its drive system may be affected by heat based on the output signals of the sensors. The failure operation (evacuation operation) is executed step by step from the one with little influence (drivability) to the user.

  FIG. 2 shows an example of the control content of the VCR mechanism 23 that is repeatedly executed by the control device 31 every predetermined time when the control device 31 is activated. The control device 31 executes a fail operation of the VCR mechanism 23 and its drive system in accordance with a control program stored in a nonvolatile memory such as a flash ROM (Read Only Memory).

  In step 1 (abbreviated as “S1” in FIG. 2, the same applies hereinafter), the control device 31 reads the engine temperature Teng and the drive system temperature Tmot from the engine temperature sensor 32 and the drive system temperature sensor 33, respectively. Here, when the drive system temperature sensor 33 detects the temperature of the compression ratio control actuator 30 and its drive circuit, it is only necessary to select the one having a high detection temperature in order to preferentially protect the thermally severe one. .

  In step 2, the control device 31 performs limit temperature (threshold values) TLeng1 and TLeng2 for executing the compression ratio limitation and the engine output limitation according to the engine temperature Teng, and the operation amount limitation according to the drive system temperature Tmot. Limit temperatures (threshold values) TLmot1, TLmot2, and TLmot3 for executing compression ratio limitation and electric actuator stop are calculated. The limit temperatures TLeng1 and TLeng2 are limit values required from the engine temperature Teng, and have a magnitude relationship of TLeng1 <TLeng2. The limit temperatures TLmot1, TLmot2, and TLmot3 are limit values required from the drive system temperature of the VCR mechanism 23, and have a magnitude relationship of TLmot1 <TLmot2 <TLmot3. In the following description, “TL” is used to indicate the entire temperature limit. The limit temperature TLeng2 is an example of the limit temperature.

  Here, the control device 31 may read the vehicle speed VSP and the outside air temperature TO from the vehicle speed sensor 34 and the outside air temperature sensor 35, respectively, and dynamically set the limit temperature TL according to these. That is, as the vehicle speed VSP increases, more traveling wind enters the engine room and the cooling performance of the VCR mechanism 23 and its drive system is improved, so that the limit temperature TL can be further increased. Further, as the outside air temperature TO becomes lower, the difference between the temperature of the VCR mechanism 23 and its drive system becomes larger, and the amount of heat radiated from the VCR mechanism 23 and its drive system increases, so that the limit temperature TL is made larger. be able to. For this reason, the control device 31 moves the limit temperature TL corresponding to the vehicle speed VSP and the outside temperature TO by referring to a map in which the limit temperature TL suitable for the vehicle speed and the outside temperature is set as shown in FIG. Can be set automatically. In addition, the map shown in FIG. 3 is calculated | required by experiment etc. and is provided for every limiting temperature TL, for example.

  In step 3, the control device 31 determines whether or not the engine temperature Teng is higher than the limit temperature TLeng2, that is, whether or not the engine temperature Teng has reached the limit temperature TLeng2 for executing the engine output limit. If it is determined that the engine temperature Teng is greater than the limit temperature TLeng2, the control device 31 proceeds to step 4 (Yes), while if it is determined that the engine temperature Teng is equal to or lower than the limit temperature TLeng2, the process proceeds to step 5 Proceed to No (No).

  In step 4, the control device 31 executes engine output restriction. Here, as the engine output restriction, for example, a reduction in the amount of fuel supplied to the internal combustion engine 1 or a reduction in the intake air amount by the electronic control throttle 41 can be executed. In this way, since the output of the internal combustion engine 1 is limited and the amount of heat generation is suppressed, the temperature of the VCR mechanism 23 integrated with the internal combustion engine 1 and its drive system (particularly, the compression ratio control actuator 30). Can be reduced.

  In step 5, the control device 31 determines whether or not the drive system temperature Tmot is higher than the limit temperature TLmot3, in other words, whether or not the drive system temperature Tmot has reached the limit temperature TLmot3 that stops the compression ratio control actuator 30. . Then, if it is determined that the drive system temperature Tmot is higher than the limit temperature TLmot3, the control device 31 proceeds to step 6 (Yes), while if it is determined that the drive system temperature Tmot is equal to or lower than the limit temperature TLmot3, the process is performed. Proceed to step 7 (No).

  In step 6, the control device 31 stops supplying the drive current to the compression ratio control actuator 30 and stops the compression ratio control actuator 30. In this way, the amount of heat generated in the compression ratio control actuator 30 becomes 0 (zero), so that an increase in temperature of the compression ratio control actuator 30 can be suppressed. When the compression ratio control actuator 30 is stopped, the compression ratio shifts to the low compression ratio side, but the internal combustion engine 1 can be continuously operated at the compression ratio.

  In step 7, the control device 31 determines whether or not the engine temperature Teng is higher than the limit temperature TLeng1, that is, whether or not the engine temperature Teng has reached the limit temperature TLeng1 for executing the compression ratio limitation. If it is determined that the engine temperature Teng is higher than the limit temperature TLeng1, the control device 31 proceeds to step 9 (Yes), while if it is determined that the engine temperature Teng is equal to or lower than the limit temperature TLeng1, the process proceeds to step 8 Proceed to No (No).

  In step 8, the control device 31 determines whether or not the drive system temperature Tmot is higher than the limit temperature TLmot2, in other words, whether or not the drive system temperature Tmot has reached the limit temperature TLmot2 for executing the compression ratio limit. If it is determined that the drive system temperature Tmot is higher than the limit temperature TLmot2, the control device 31 proceeds to step 9 (Yes), while if it is determined that the drive system temperature Tmot is equal to or lower than the limit temperature TLmot2, the process is performed. Proceed to step 10 (No).

  In step 9, the control device 31 executes compression ratio limitation. That is, the control device 31 limits the target compression ratio according to the operating state of the internal combustion engine 1 to a compression ratio control range (fixed value) that can suppress the heat generation amount of the compression ratio control actuator 30.

  At this time, the control device 31 may dynamically set the control range of the compression ratio according to the engine temperature Teng or the drive system temperature Tmot. That is, as shown in FIG. 4, the control device 31 refers to a map in which a control range (upper limit value and lower limit value) adapted to the engine temperature or the drive system temperature is set, and sets the engine temperature Teng or the drive system temperature Tmot. Set the control range of the corresponding compression ratio. In this map, when the engine temperature or the drive system temperature rises to some extent, the upper limit value gradually decreases and the lower limit value gradually increases to gradually narrow the control range of the compression ratio. As shown, the compression ratio is constant. The compression ratio indicated by A in the figure takes a value that allows combustion at a low load and does not cause preignition (pre-ignition). Note that the map shown in FIG. 4 represents an example obtained by, for example, experiments.

  The control device 31 refers to a map in which a correction coefficient suitable for the engine temperature or the drive system temperature is set, and sets the control range of the compression ratio based on the correction coefficient corresponding to the engine temperature Teng or the drive system temperature Tmot. You may make it correct | amend the upper limit value and lower limit value to demarcate, respectively. In this case, an upper limit correction and a lower limit correction may be used as the correction coefficients. In this way, the upper limit value and the lower limit value can be set individually.

  In step 10, the control device 31 determines whether or not the drive system temperature Tmot is higher than the limit temperature TLmot1, that is, whether or not the drive system temperature Tmot reaches the limit temperature TLmot1 that limits the operation amount of the compression ratio control actuator 30. Determine. If it is determined that the drive system temperature Tmot is higher than the limit temperature TLmot1, the control device 31 proceeds to step 11 (Yes), while if it is determined that the drive system temperature Tmot is equal to or lower than the limit temperature TLmot1, the process is performed. End (No).

  In step 11, the control device 31 limits the operation amount of the compression ratio control actuator 30. That is, when the control device 31 changes the compression ratio according to the operating state of the internal combustion engine 1, the operation speed (change speed) or the drive amount (duty ratio, gain, etc.) of the compression ratio control actuator 30 is limited to a fixed value. Then, the amount of heat generated in the compression ratio control actuator 30 is suppressed.

  At this time, the control device 31 may dynamically set the operation speed or the drive amount of the compression ratio control actuator 30 according to the drive system temperature Tmot. That is, as shown in FIG. 5, the control device 31 refers to a map in which the maximum operation speed or maximum drive amount suitable for the drive system temperature is set, and the maximum operation speed or maximum drive amount according to the drive system temperature Tmot. Set. In this map, when the drive system temperature rises to some extent, the operation amount gradually decreases as the drive system temperature rises, and finally the operation amount becomes constant. Note that the map shown in FIG. 5 represents an example obtained by, for example, experiments.

  According to the control device 31 of the VCR mechanism 23, for example, the compression ratio is frequently changed according to the operating state of the internal combustion engine 1, thereby limiting the drive system temperature Tmot of the compression ratio control actuator 30 and its drive circuit. When the temperature TLmot1 is reached, the operation amount of the compression ratio control actuator 30 is limited as the first stage of the fail operation. In a state where the operation amount of the compression ratio control actuator 30 is limited, the speed of changing the compression ratio by the VCR mechanism 23 is decreased and the drivability is slightly decreased, but the drive current supplied to the compression ratio control actuator 30 is decreased. The amount of heat generated by the compression ratio control actuator 30 and its drive circuit is reduced. At this time, if the maximum operation amount is dynamically set according to the drive system temperature Tmot, the heat generation of the compression ratio control actuator 30 and its drive circuit can be effectively suppressed.

  Despite limiting the operation amount of the compression ratio control actuator 30, the drive system temperature Tmot further increases for some reason and reaches the limit temperature TLmot2, or the engine temperature Teng becomes the limit temperature due to a change in the operating state of the internal combustion engine 1. When TLeng1 is reached, the control range of the compression ratio is limited as the second stage of the fail operation. In a state where the control range of the compression ratio is limited, the operation frequency of the compression ratio control actuator 30 is reduced, so that the drive current supplied to the compression ratio control actuator 30 is further reduced as compared with the first stage, and the compression ratio control is performed. The amount of heat generated by the actuator 30 and its drive circuit is further reduced. At this time, if the control range of the compression ratio is dynamically set according to the engine temperature Teng or the drive system temperature Tmot, the heat generation of the compression ratio control actuator 30 and its drive circuit can be effectively suppressed.

  If the drive system temperature Tmot further rises for some reason and reaches the limit temperature TLmot3 even though the compression ratio control range is limited, as a third stage of the fail operation, the drive current to the compression ratio control actuator 30 is reduced. Supply is interrupted and the amount of heat generated becomes zero. For this reason, as compared with the second stage, the drive current supplied to the compression ratio control actuator 30 is further reduced, and the heat generation amount of the compression ratio control actuator 30 and its drive circuit is further reduced. At this time, the compression ratio control actuator 30 stops and the compression ratio shifts to the low compression ratio side. Even in this state, the internal combustion engine 1 can be driven. For example, the vehicle is moved to a service factory or the like. It is possible to realize limp home control that enables conveyance.

  When the engine temperature Teng further rises according to the operating state of the internal combustion engine 1 and reaches the limit temperature TLeng2 even though the compression ratio control actuator 30 is stopped, the output of the internal combustion engine 1 is the fourth stage of the fail operation. Is limited. In a state where the output of the internal combustion engine 1 is limited, the amount of heat generated in the internal combustion engine 1 is reduced, and the temperature increase of the compression ratio control actuator 30 integrated with the internal combustion engine 1 and its drive circuit can be suppressed. At this time, since the amount of heat generated in the internal combustion engine 1 is reduced, the temperature rise of the internal combustion engine 1 is suppressed, and the VCR mechanism 23 incorporated therein can be protected. For this reason, it is possible to prevent the VCR mechanism 23 from being affected by heat.

  Therefore, as the engine temperature Teng and the drive system temperature Tmot rise, as shown in FIG. 6, as the first to fourth stages of the fail operation, the operation amount limitation, the compression ratio limitation, the electric actuator stop, and the engine output limitation are performed. Are executed sequentially. The drivability decreases in the order of operation amount limitation, compression ratio limitation, electric actuator stop, and engine output limitation. However, since the fail operation is executed in stages, a decrease in drivability can be suppressed.

  Therefore, according to the present embodiment, it is possible to prevent the temperature of the compression ratio control actuator 30 and its drive system from excessively rising while suppressing a decrease in drivability.

  Since the compression ratio control actuator 30 and its drive circuit are integrated with the internal combustion engine 1, the drive system temperature Tmot and the engine temperature Teng are highly correlated. For this reason, since the drive system temperature Tmot is considered to indirectly indicate the engine temperature Teng, the drive system temperature Tmot can also be regarded as the engine temperature Teng.

  Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.

(A) The control device for an internal combustion engine according to claim 1 or 2, wherein a drive current supplied to the electric actuator is reduced by limiting a control range of a compression ratio by the electric actuator. .
In this way, since the operating frequency of the electric actuator is reduced, the drive current supplied to the electric actuator is reduced. For this reason, the emitted-heat amount of an electric actuator and its drive circuit can be reduced.

(B) The control device for an internal combustion engine according to (a), wherein the compression ratio is dynamically set according to the temperature of the internal combustion engine.
In this way, heat generation of the electric actuator and its drive circuit can be effectively suppressed.

(C) The control device for an internal combustion engine according to claim 1 or 2, wherein the drive current supplied to the electric actuator is reduced by stopping the electric actuator.
In this way, since the heat generation amount of the electric actuator becomes 0, the heat generation amount of the electric actuator and its drive circuit can be reduced.

(D) when the temperature of the internal combustion engine exceeds the predetermined temperature, the operation amount of the electric actuator is limited as the temperature of the internal combustion engine rises, the control range of the compression ratio controlled by the electric actuator is limited, The control device for an internal combustion engine according to any one of claims 1 to 3, and (a) to (c), wherein the electric actuator is sequentially stopped.
In this way, when the temperature of the internal combustion engine exceeds a predetermined temperature, the operation amount limitation, the compression ratio limitation, the electric actuator stop and the engine output limitation are executed in stages as a fail operation. Can be suppressed.

(E) When the temperature of the internal combustion engine reaches a limit temperature higher than the predetermined temperature, the output of the internal combustion engine is limited. The control apparatus for an internal combustion engine according to any one of (d).
In this way, the amount of heat generated in the internal combustion engine is reduced, and an increase in the temperature of the electric actuator integrated with the internal combustion engine and its drive circuit can be suppressed. At this time, since the amount of heat generated in the internal combustion engine is reduced, the temperature rise of the internal combustion engine is suppressed, and the VCR mechanism incorporated therein can be protected.

(F) The predetermined temperature is dynamically set in accordance with a vehicle speed and an outside air temperature, according to any one of claims 1 to 3, and (a) to (e). Control device for internal combustion engine.
In this way, a fail operation can be performed in consideration of the heat dissipation characteristics of the electric actuator and its drive circuit.

(G) The control device for an internal combustion engine according to claim 3, wherein the operation amount is an operation speed or a drive amount of the electric actuator.
If it does in this way, the drive current supplied to an electric actuator can be reduced by restricting the operation speed or drive amount of an electric actuator.

(H) The operation speed or driving amount of the electric actuator is dynamically set according to the temperature of the internal combustion engine.
In this way, heat generation of the electric actuator and its drive circuit can be effectively suppressed.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 23 VCR mechanism 30 Compression ratio control actuator 31 Control apparatus 32 Engine temperature sensor 33 Drive system temperature sensor

Claims (3)

In an internal combustion engine equipped with a variable compression ratio mechanism that makes the compression ratio variable by an electric actuator,
Reducing the drive current supplied to the electric actuator when the temperature of the internal combustion engine exceeds a predetermined temperature;
A control device for an internal combustion engine. As the temperature of the internal combustion engine increases, the drive current supplied to the electric actuator is greatly reduced.
The control apparatus for an internal combustion engine according to claim 1. By limiting the operation amount of the electric actuator, the drive current supplied to the electric actuator is reduced.
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by the above.