JP6477278B2 - Control device for variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable compression ratio mechanism capable of changing an engine compression ratio.

  Conventionally, a variable compression ratio internal combustion engine including a variable compression ratio mechanism that changes the engine compression ratio of the internal combustion engine in accordance with the rotational position of a control shaft is known. Patent Document 1 discloses a technique for restricting the operation of the drive motor or stopping the operation of the drive motor in accordance with the temperature of the drive motor that changes and holds the rotational position of the control shaft.

JP 2009-185629 A

  In the variable compression ratio mechanism, a load corresponding to the engine torque repeatedly acts on the control shaft during engine operation. Therefore, the drive motor that drives the control shaft is required to have a motor torque that supports a high load and load. There is a concern that the current flowing through the motor increases, and the motor temperature is excessively increased and the motor torque is reduced accordingly.

  The present invention has been made in view of such circumstances. When the motor temperature is high, the load / load acting on the drive motor side from the control shaft is reduced to suppress the heat generation of the drive motor. It is aimed.

  A control apparatus for a variable compression ratio internal combustion engine according to the present invention includes a variable compression ratio mechanism that changes an engine compression ratio according to a rotational position of a control shaft that is rotatably supported by an engine body, and a rotational position of the control shaft. And a drive motor that is changed and held, and is configured such that the reduction ratio of the rotational power transmission path from the drive motor to the control shaft changes according to the rotational position of the control shaft.

  And a motor temperature acquisition means for detecting or estimating the motor temperature of the drive motor, and when the motor temperature becomes equal to or higher than a predetermined temperature, the rotational position of the control shaft is increased so that the reduction ratio of the rotational power transmission mechanism is increased. To change.

  According to the present invention, when the motor temperature is higher than the predetermined temperature, the reduction ratio of the rotational power transmission mechanism is increased by changing the rotational position of the control shaft, so that the load / load acting from the control shaft to the drive motor side is reduced. In order to reduce this, it is possible to suppress further heat generation on the drive motor side, improve the reliability and durability of the drive motor, and ensure the holding torque of the drive motor, resulting in inadvertent fluctuation of the control shaft The fluctuation of the compression ratio can be suppressed.

The schematic block diagram which shows the variable compression ratio mechanism which concerns on one Example of this invention. The perspective view which shows a part of variable compression ratio internal combustion engine of the said Example. The characteristic view which shows the relationship between the reduction ratio of a connection mechanism, and an engine compression ratio. The flowchart which shows the flow of control which concerns on one Example of this invention. The flowchart which shows the flow of control which concerns on the other Example of this invention. Explanatory drawing which shows the link structure which concerns on the said Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. First, a variable compression ratio mechanism using a multi-link piston-crank mechanism according to an embodiment of the present invention will be described with reference to FIGS. Since this mechanism is known as described in the above-mentioned Japanese Patent Application Laid-Open No. 2009-185629, etc., only a brief description will be given.

  A piston 3 of each cylinder is slidably fitted in a cylinder 2 and a crankshaft 4 is rotatably supported on a cylinder block 1 constituting a part of an engine body of the internal combustion engine. The variable compression ratio mechanism 10 includes a lower link 11 rotatably attached to the crankpin 5 of the crankshaft 4, an upper link 12 connecting the lower link 11 and the piston 3, and the engine body side such as the cylinder block 1. A control shaft 14 rotatably supported; a control eccentric shaft portion 15 provided eccentric to the control shaft 14; and a control link 13 connecting the control eccentric shaft portion 15 and the lower link 11. ing. The piston 3 and the upper end of the upper link 12 are connected via a piston pin 16 so as to be relatively rotatable, and the lower end of the upper link 12 and the lower link 11 are connected via a first connecting pin 17 so as to be relatively rotatable. The upper end of the link 13 and the lower link 11 are connected to each other via a second connecting pin 18 so as to be relatively rotatable, and the lower end of the control link 13 is rotatably attached to the control eccentric shaft portion 15.

  A drive motor 20 (see FIG. 2 and the like) is connected to the control shaft 14 via a connection mechanism 21, and the rotational position of the control shaft 14 is changed and held by the drive motor 20, thereby the lower link 11. As the posture changes, the piston stroke characteristics including the piston top dead center position and the piston bottom dead center position change, and the engine compression ratio changes. Therefore, by controlling the drive motor 20 by the control unit 40, the engine compression ratio can be controlled according to the engine operating state.

  On the side wall 7 on the intake side of the oil pan upper 6A that is fixed below the cylinder block 1 as the engine body, a housing 22 that houses the coupling mechanism 21 and a drive motor 20 are arranged along the longitudinal direction of the engine. ing.

  As shown in FIGS. 1 and 2, the control shaft 14 disposed in the engine body and the rotating shaft 23 of the coupling mechanism 21 disposed in the housing 22 are coupled by a lever 24. In this embodiment, the rotating shaft 23 is configured integrally with the output shaft of the speed reducer (not shown). However, the rotating shaft 23 is configured separately from the output shaft of the speed reducer, and both are integrated. A rotating structure may be used.

  One end of the lever 24 and the tip of the first arm portion 25 extending radially outward from the center of the control shaft 14 are connected to each other via a third connecting pin 33 so as to be relatively rotatable. The distal end of the second arm portion 27 extending outward in the radial direction and the other end of the lever 24 are connected via a fourth connecting pin 35 so as to be relatively rotatable. In FIG. 2, the fourth connection pin 35 is omitted, and a pin connection hole 35 </ b> A of the rotating shaft 23 into which the fourth connection pin 35 is fitted is illustrated. The side wall 7 on the intake side of the oil pan upper 6A is formed with a slit-like communication hole through which the lever 24 is inserted.

The coupling mechanism 21 is provided with a speed reducer that decelerates the output of the drive motor 20 and transmits it to the control shaft 14 side. As the speed reducer, a wave gear device or a cyclo speed reducer that can obtain a large speed reduction ratio is used. Further, the reduction ratio by the link structure including the lever 24, the first arm portion 25, and the second arm portion 27 is configured to change according to the rotational position of the control shaft 14. That is, when the control shaft 14 is rotated, the engine compression ratio is changed and the postures of the first arm portion 25, the second arm portion 27, and the lever 24 are changed, so that the rotational power transmission path from the motor 20 to the control shaft 14 is changed. The reduction ratio will also change. Specifically, as shown in FIG. 3, basically, when the control shaft 14 rotates to the low compression ratio side, the reduction ratio of the rotational power transmission path from the motor 20 to the control shaft 14 is increased. In the vicinity of the maximum compression ratio, when the control shaft 14 rotates to the high compression ratio side, the reduction ratio is increased.
Next, a specific structure capable of obtaining the relationship between the engine compression ratio and the reduction ratio as shown in FIG. 3 will be described with reference to FIG. As shown in FIG. 6A, the length 24C of the lever 24 is set longer than the lever length 24B in a posture in which the first and second arm portions 25, 27 and the lever 24 are orthogonal to each other. In other words, when one of the first arm portion 25 or the second arm portion 27 is orthogonal to the lever 24, the angle between the other of the first arm portion 25 or the second arm portion 27 and the lever 24 is an acute angle. In addition, the length 24C of the lever 24 is set. Further, as shown in FIG. 6B, the angle formed by the lever 24 and the first arm portion 25 is an obtuse angle when the compression ratio is low and an acute angle when the compression ratio is high, and the control eccentric shaft portion 15 of the control shaft 14 is The control shaft 14 is disposed on the side closer to the rotation shaft 23. According to the link layout as described above, the reduction ratio becomes the minimum reduction ratio near the intermediate compression ratio, and the reduction ratio gradually increases from the vicinity of the intermediate compression ratio toward the high compression ratio side or the low compression ratio side. Maximum reduction ratio on the low compression ratio side.

  FIG. 4 is a flowchart showing the control flow of the present embodiment. This routine is repeatedly executed by the control unit 40, for example, every predetermined period (for example, every 10 ms). In step S11, it is determined whether or not the motor temperature, which is the temperature of the drive motor 20, is equal to or higher than a predetermined temperature. This motor temperature is estimated using the detection value of the oil temperature sensor 41 which detects the oil temperature of an internal combustion engine, for example.

  If the motor temperature is not equal to or higher than the predetermined temperature, the process proceeds to step S12, and this routine is terminated without limiting the engine compression ratio. On the other hand, if the motor temperature is equal to or higher than the predetermined temperature, the process proceeds to step S13, and the engine compression ratio is converted to the low compression ratio side so that the reduction ratio of the rotational power transmission path from the motor 20 to the control shaft 14 is increased. Thus, for example, even if the motor temperature becomes higher than a predetermined temperature when the engine is heavily loaded, the load / load applied to the drive motor 20 can be reduced by increasing the reduction ratio of the rotational power transmission path from the motor 20 to the control shaft 14. By suppressing the motor heat generation amount, the durability and reliability of the drive motor 20 can be improved. In addition, by setting the operating point with a high reduction ratio of the rotational power transmission path from the motor 20 to the control shaft 14 to the low compression ratio side, the running performance of the vehicle is not impaired even at high motor temperatures.

  Furthermore, by estimating the motor temperature using the oil temperature of the oil temperature sensor 41 that is used for general purposes, the motor temperature sensor becomes unnecessary, and the cost can be reduced.

  However, the method for detecting or estimating the motor temperature is not limited to this, and for example, the vehicle temperature obtained by the vehicle speed sensor 42 and the intake air temperature obtained by the intake air temperature sensor 43 may be estimated in addition to the oil temperature. good. In this case, the motor temperature can be estimated with higher accuracy. Further, the motor temperature may be detected directly using a motor temperature sensor that actually detects the motor temperature, or the motor temperature may be estimated from the operation history.

  FIG. 5 is a flowchart showing the flow of control according to another embodiment, and the processes in steps S11 and S12 are the same as those in FIG. In the variable compression ratio mechanism 10, when the drive motor 20 is stopped by a load acting from the piston side, the control shaft 14 rotates as much as possible to the low compression ratio side. Therefore, in this embodiment, when the motor temperature is equal to or higher than the predetermined temperature, the process proceeds from step S11 to step S13A, and the operation of the drive motor 20 is stopped. In this case, as the drive motor 20 stops operating, the control shaft 14 shifts to the low compression ratio side, which is a mechanically stable point, and the rotation from the motor 20 to the control shaft 14 is similar to the above embodiment. In addition to suppressing the load and load applied to the drive motor 20 by increasing the reduction ratio of the power transmission path, the motor heat generation amount can be reduced, and the durability and reliability of the drive motor 20 can be improved. By stopping the motor 20, it is possible to further suppress the motor heat generation while suppressing the power consumption.

    As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes. For example, in the above embodiment, as shown in FIG. 6, the protruding direction of the first arm portion 25 and the protruding direction of the second arm portion 27 with respect to a straight line passing through the center of the control shaft 14 and the center of the rotating shaft 23. Are set in the same direction, but the protruding direction may be set in the opposite direction.

DESCRIPTION OF SYMBOLS 10 ... Variable compression ratio mechanism 14 ... Control shaft 20 ... Drive motor 21 ... Connection mechanism 40 ... Control part 41 ... Oil temperature sensor 42 ... Vehicle speed sensor 43 ... Intake temperature sensor

Claims (5)

A variable compression ratio mechanism that changes the engine compression ratio according to the rotational position of a control shaft that is rotatably supported by the engine body;
A drive motor for changing / holding the rotational position of the control shaft;
Have
According to the rotational position of the control shaft, the reduction ratio of the rotational power transmission path from the drive motor to the control shaft is configured to change,
And it has a motor temperature acquisition means for detecting or estimating the motor temperature of the drive motor,
A control apparatus for a variable compression ratio internal combustion engine, wherein the rotational position of the control shaft is changed so that a reduction ratio of the rotational power transmission path is increased when the motor temperature is equal to or higher than a predetermined temperature. When the control shaft rotates to the low compression ratio side, the reduction ratio of the rotational power transmission path is configured to be high,
When the motor temperature becomes the predetermined temperature or higher, and changes the engine compression ratio by changing the rotational position of the control shaft so a reduction ratio is increased in the rotation power transmission path in the low compression ratio side The control apparatus for a variable compression ratio internal combustion engine according to claim 1. When the control shaft rotates to the low compression ratio side, the reduction ratio of the rotational power transmission path is configured to be high,
When the motor temperature becomes the predetermined temperature or higher, the control device for a variable compression ratio internal combustion engine according to claim 1, characterized in that stopping the drive motor so that the speed reduction ratio of the rotation power transmission path is high.   The motor temperature acquisition means calculates the motor temperature based on at least one of the engine oil temperature detected by the oil temperature sensor, the vehicle speed detected by the vehicle speed sensor, and the intake air temperature detected by the intake air temperature sensor. The control apparatus for a variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein the controller is estimated. The variable compression ratio internal combustion engine according to any one of claims 1 to 4, wherein when the control shaft rotates toward a high compression ratio that increases an engine compression ratio, a reduction ratio of the rotational power transmission path increases. Control device.

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