JP5906589B2 - Fault diagnosis device for internal combustion engine - Google Patents

Description

  The present invention relates to a failure diagnosis apparatus for an internal combustion engine having a variable compression ratio mechanism.

  Conventionally, a wave gear reduction mechanism using elastic deformation of a flexible gear is known. For example, Patent Document 1 discloses a transmission ratio variable mechanism that changes a transmission ratio between a steering angle of a steering wheel and a turning angle of a steered wheel by driving an actuator that is positioned between the steering wheel and the steered wheel. Discloses a configuration in which a wave gear reduction mechanism is incorporated.

  In this patent document 1, the rotation angle of the input shaft of the transmission ratio variable mechanism connected to the steering handle and the transmission ratio variable mechanism connected to the steered wheels on both sides of the rack shaft via a rack and pinion type gear device. The rotation angle of the output shaft and the operating angle of the actuator that drives the transmission ratio variable mechanism are detected, and the steering angle, turning angle, and operating angle are determined from the relationship between the steering angle, the turning angle, and the operating angle. Among the sensors to be detected, the failure determination of the sensor that detects the relative rotation angle is performed.

JP 2000-351383 A

  However, in this Patent Document 1, although the relative displacement of the angle between the input shaft and the output shaft of the transmission ratio variable mechanism can be specified, it is not possible to specify the minute angle deviation caused by wear in the wave gear reduction mechanism. . That is, the wear in the wave gear reduction mechanism cannot be detected, and a failure of the wave gear reduction mechanism due to wear in the wave gear reduction mechanism cannot be determined. When wear in the wave gear reduction mechanism progresses, the wave gear reduction mechanism may idle, which adversely affects members and mechanisms to which rotation is transmitted via the wave gear reduction mechanism.

  Claim 1 of the present invention has a wave gear speed reduction mechanism provided between a control shaft of a variable compression ratio mechanism and an actuator for changing the rotational position of the control shaft, and keeps the engine compression ratio constant. When the compression ratio holding torque generated by the actuator is greater than or equal to a preset value, the meshing rate between the gears in the wave gear reduction mechanism decreases, and it is determined that there is a failure due to wear in the wave gear reduction mechanism. It is characterized by doing. According to a second aspect of the present invention, there is provided a wave gear reduction mechanism provided between a control shaft of the variable compression ratio mechanism and an actuator for changing the rotational position of the control shaft, and an initial position on the high compression ratio side. When the time from the initial position on the low compression ratio side to the initial position on the low compression ratio side or the time from the initial position on the low compression ratio side to the initial position on the high compression ratio side is equal to or less than a predetermined time, The meshing rate of the gears in the wave gear reduction mechanism decreases, and it is determined that there is a failure due to wear in the wave gear reduction mechanism.

  According to the present invention, it is possible to detect a failure due to a decrease in the meshing rate in the wave gear reduction mechanism using the actuator torque.

The explanatory view showing typically the variable compression ratio mechanism which consists of a double link type piston-crank mechanism of an internal-combustion engine to which the present invention was applied. Explanatory drawing which showed typically the wave gear reduction mechanism which concerns on this invention. Explanatory drawing which showed typically the wave gear reduction mechanism which concerns on this invention. Explanatory drawing which showed typically the wave gear reduction mechanism which concerns on this invention. The flowchart which shows the flow of control of the failure determination of the wave gear reduction mechanism which concerns on this invention. The flowchart which shows the flow of control of the other failure determination of the wave gear reduction mechanism which concerns on this invention. Flowchart showing the flow of control failure determination of the wave gear drive structure according to the reference example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a variable compression ratio mechanism including a multi-link type piston-crank mechanism of an internal combustion engine to which the present invention is applied. As shown in the drawing, a piston 1 is slidably disposed in a cylinder 6 formed in a cylinder block 5, and one end of an upper link 11 can swing on the piston 1 via a piston pin 2. It is connected to. The other end of the upper link 11 is rotatably connected to one end portion of the lower link 13 via a first connecting pin 12. The lower link 13 is swingably attached to the crankpin 4 of the crankshaft 3 at the center thereof. The piston 1 receives a combustion pressure from a combustion chamber defined above. The crankshaft 3 is rotatably supported on the cylinder block 5 by a crank bearing bracket 7.

  One end of a control link 15 is rotatably connected to the other end of the lower link 13 via a second connecting pin 14. The other end of the control link 15 is swingably supported by a fixed portion of the internal combustion engine having the cylinder block 5 as a main component, and a swing fulcrum 16 is provided for changing the engine compression ratio. It can be displaced with respect to the engine body. Specifically, a circular eccentric cam 19 is eccentrically provided on the control shaft 18 extending in parallel with the crankshaft 3, and the other end of the control link 15 is rotatably fitted on the outer peripheral surface of the eccentric cam 19. Match. The control shaft 18 is rotatably supported between the crank bearing bracket 7 and the control bearing bracket 8.

  Therefore, when the rotational position of the control shaft 18 is changed to change the engine compression ratio, the center position of the eccentric cam 19 serving as the swing fulcrum 16 of the control link 15 moves relative to the engine body. As a result, the movement restraint condition of the lower link 13 by the control link 15 changes, the stroke position of the piston 1 with respect to the crank angle, that is, the top dead center position and the bottom dead center position, and the engine compression ratio is changed accordingly. become.

  The rotational position of the control shaft 18 is changed and held by a drive motor 20 as an actuator. A wave gear reduction mechanism 21 is provided in the power transmission path from the drive motor 20 to the control shaft 18. The wave gear reduction mechanism 21 has a function as a reduction device that reduces the rotation of the drive motor 20 and transmits it to the control shaft 18 as will be described later.

  The control unit 10 is a digital computer system that stores and executes various control processes. The control unit 10 outputs a control signal to the drive motor 20 of the variable compression ratio mechanism according to the engine operation state, and controls the operation thereof. The output shaft sensor 22 as an actuator rotation amount detecting means for detecting the rotational position of the output shaft 20a (see FIG. 3), the current sensor 23 for detecting the motor driving current when the driving torque is generated in the driving motor 20, etc. Signals from various sensors are input. Then, in the control unit 10, a failure determination of the wave tooth reduction mechanism 21 is performed from the drive torque generated in the drive motor 20 as will be described later.

  The output shaft sensor 22 is a non-contact type sensor using a Hall IC element, and is provided on the rear end side of the drive motor 20 as shown in FIGS. A circular plate (not shown) in which a large number of slits are formed is attached to the rear end portion of the output shaft 20a of the drive motor 20 so as to face the output shaft sensor 22, for example, other than the slits. An output signal is output to the control unit 10 so as to be high at the portion, and low at the slit portion. In the control unit 10, the rotation amount of the output shaft 20 a can be detected from the number of times that the slit portion has passed, that is, from the count number of the pulse signal corresponding to the rotation number of the drive motor 20.

  The wave gear reduction mechanism 21 will be described with reference to FIGS. The wave gear reduction mechanism 21 is fixed to a fixed part such as a cylinder block 5 or a casing of an internal combustion engine, and has a rigid internal gear 31 having an inner tooth (spline) 32 formed on the inner periphery thereof, and an inner side of the internal gear 31. The external teeth (splines) 34 that are arranged concentrically with each other and have two teeth fewer than the internal teeth 32 are formed on the outer periphery, and the flexible external gear 33 that rotates together with the control shaft 18, and this flexible external gear A wave generator 35 having an elliptical outline disposed inside the gear 33 is roughly constituted.

  The internal gear 31 has an annular shape, and a number of bolt holes 36 into which fixing bolts for fixing to a fixing portion of the internal combustion engine are fitted are intermittently formed in the circumferential direction. In order not to be deformed like this, it is made of a metal material harder than the flexible external gear 33.

  The flexible external gear 33 has a thin bottomed cylindrical shape including a disk-shaped bottom portion 37 and a cylindrical portion 38, and external teeth 34 are formed on the outer peripheral surface of the cylindrical portion 38. The cylindrical portion 38 of the flexible external gear 33 has a cylindrical shape before the wave generator 35 having an elliptical outline is attached to the inside, but the wave generator 35 having an elliptical outline is attached to the inside. In this state, as shown in FIG. 4, the cylindrical portion 38 is bent into an elliptical shape. The flexible external gear 33 is concentrically connected to the flange portion 40 (see FIG. 3) of the control shaft 18 by a fixing bolt 39 while the bottom portion 37 of the flexible external gear 33 is fitted to a convex portion (not shown) at one end of the control shaft 18. Fixed to.

  The wave generator 35 is fixed to the output shaft 20a of the drive motor 20, and rotates together with the output shaft 20a. The wave generator 35 has a ball bearing 41 that can be bent and deformed concentrically attached to the outside thereof. The inner ring 42 inside the ball bearing 41 is attached to the outer periphery of the wave generator 35, and the outer ring 43 outside is attached to the wave generator 35 so as to be relatively rotatable. 2 to 4, 44 is a ball of the ball bearing 41.

  As shown in FIG. 4, the wave gear speed reduction mechanism 21 configured in this way has a flexible outer surface at two locations facing each other across the center of the wave generator 35 in the longitudinal direction of the wave generator 35. The gear 33 and the internal gear 31 are engaged with each other. As a result, when the wave generator 35 rotates, the meshing position of the internal teeth 32 and the external teeth 34 moves in the circumferential direction, and when the wave generator 35 rotates once, the flexible external gear 33 has a difference in the number of teeth. Move in the direction of rotation by two sheets. That is, power is transmitted from the output shaft 20 a of the drive motor 20 to the control shaft 18 with a large reduction ratio.

  In the wave gear reduction mechanism 21, the number of teeth that the inner teeth 32 and the outer teeth 34 mesh with each other is large, and the friction of the meshed portions is large. Further, the reduction ratio in the wave gear reduction mechanism 21 is large. Therefore, it is difficult for the drive motor 20 to be rotated by torque from the control shaft 18 side (internal combustion engine side). Therefore, in order to keep the engine compression ratio constant, the rotational position of the control shaft 18 is maintained to the extent that the drive motor 20 is less likely to be rotated by torque from the control shaft 18 side (internal combustion engine side). Thus, the compression ratio holding torque of the drive motor 20 required can be reduced.

  However, if the inside of the wave gear speed reduction mechanism 21 is worn, the meshing rate of the internal teeth 32 and the external teeth 34 in the toothed gear speed reduction mechanism 21 decreases, and the friction at the meshing portion of the internal teeth 32 and the external teeth 34 occurs. Therefore, the drive motor 20 is easily rotated by torque from the control shaft 18 side (internal combustion engine side). That is, in the wave gear reduction mechanism 21, if the inside is worn and the meshing rate is reduced, the drive motor 20 at the time of holding the rotational position of the control shaft 18 in order to maintain the engine compression ratio correspondingly. The compression ratio holding torque increases.

  In addition, when wear in the wave gear reduction mechanism 21 progresses and the wave gear reduction mechanism 21 idles, the movement of the main moving parts (link member, control shaft) of the variable compression ratio mechanism becomes unexpected, and the internal combustion engine It may adversely affect the operation of the engine.

  As shown by arrows in FIG. 3, places where wear is considered in the wave gear speed reduction mechanism 21 are portions where the ball 44 and the outer ring 43 and the ball 44 and the inner ring 42 are in contact with each other (a wear expected place A). ), And the internal teeth 32 of the internal gear 31 and the external teeth 34 of the flexible external gear 33 mesh with each other (a wear assumed location B).

  Therefore, the failure of the wave gear reduction mechanism 21 due to internal wear is detected by detecting the wear state in the wave gear reduction mechanism 21 using the motor torque generated in the drive motor 20.

  Specifically, when the internal combustion engine is operating, the drive current of the drive motor 20 when the engine compression ratio is kept constant is detected by the current sensor 23, and the current value at this time is regarded as the compression ratio holding torque. If the compression ratio holding torque is equal to or greater than a predetermined value (predetermined torque) that is a torque required to keep the engine compression ratio constant when there is no wear inside the wave gear reduction mechanism 21, the wave gear It is determined that the meshing rate of the internal teeth 32 and the external teeth 34 is reduced in the speed reduction mechanism 21, and a failure due to internal wear has occurred in the wave gear speed reduction mechanism 21.

  That is, a failure due to a decrease in the meshing rate of the wave gear reduction mechanism 21 can be detected using the motor torque generated in the drive motor 20.

  If it is determined that there is a failure, for example, the engine compression ratio is set so that the input load from the internal combustion engine to the wave gear reduction mechanism 21 is reduced, or a warning lamp provided on the instrument panel of the vehicle is turned on. You may make it notify a driver | operator that the failure of the wave gear reduction mechanism 21 has generate | occur | produced.

  FIG. 5 is a flowchart showing the flow of control for failure determination of the wave gear reduction mechanism 21 using the compression ratio holding torque.

  In S11, it is determined whether or not the engine compression ratio is kept constant. If the engine compression ratio is kept constant, the process proceeds to S2, and if not, the current routine is terminated. In S12, the motor drive current when the compression ratio holding torque is generated in the drive motor 20 in the state where the rotational position of the output shaft 20a of the drive motor 20 is feedback-controlled is used as the compression ratio holding torque at this time. It detects with the sensor 23 and progresses to S13. In S13, it is determined whether or not the compression ratio holding torque is larger than the predetermined torque. Specifically, it is determined whether or not the current value detected by the current sensor 23 is larger than a preset current value corresponding to a predetermined torque. It is determined that the wave gear speed reduction mechanism 21 has occurred. If it is smaller, the current routine is terminated assuming that a failure due to internal wear has not occurred in the wave gear reduction mechanism 21.

  In addition, when a constant torque is generated in the drive motor 20 with the internal combustion engine stopped, if the inside of the wave gear reduction mechanism 21 is worn, the internal teeth 32 and the external teeth in the toothed gear reduction mechanism 21 are removed. Since the meshing rate of the teeth 34 is reduced and the friction at the meshing portion of the internal teeth 32 and the external teeth 34 is reduced, the drive motor 20 can easily rotate the control shaft 18 correspondingly.

  For example, in the initial position learning of the variable compression ratio mechanism performed by abutting the control shaft 18 against the low compression ratio side stopper and the high compression ratio side stopper while the internal combustion engine is stopped, The drive motor 20 is driven at a constant duty ratio. If the inside of the wave gear reduction mechanism 21 is worn and the meshing rate is reduced, the control shaft 18 is easily rotated by the drive motor 20. The time required to rotate 18 from a state where it abuts against the stopper on the low compression ratio side (initial position on the low compression ratio side) to a state where it abuts against the stopper on the high compression ratio side (initial position on the high compression ratio side) is short. Become.

  Therefore, even during initial position learning of the variable compression ratio mechanism performed while the internal combustion engine is stopped, by detecting the wear state in the wave gear reduction mechanism 21 using the motor torque generated in the drive motor 20, A failure of the wave gear reduction mechanism 21 due to internal wear can be detected.

  Specifically, in the initial position learning of the variable compression ratio mechanism performed when the internal combustion engine is stopped, the low compression ratio is changed from the state in which the control shaft 18 abuts against the stopper on the high compression ratio side (initial position on the high compression ratio side). The initial position learning time, which is the time required to rotate to the state where it abuts against the stopper on the side (the initial position on the low compression ratio side), and if the initial position learning time is equal to or less than a preset predetermined time T, In the wave gear reduction mechanism 21, the meshing rate of the internal teeth 32 and the external teeth 34 is reduced, and it is determined that a failure due to internal wear has occurred in the wave gear reduction mechanism 21. Here, the predetermined time T described above is required to rotate the control shaft 18 from the initial position on the high compression ratio side to the initial position on the low compression ratio side when there is no wear in the wave gear reduction mechanism 21. It's time.

  In addition, instead of the time required to rotate the control shaft 18 from the initial position on the high compression ratio side to the initial position on the low compression ratio side, the control shaft 18 is changed from the initial position on the low compression ratio side to the initial position on the high compression ratio side. Even using the time required to rotate to the position, it is possible to detect a failure of the wave gear reduction mechanism 21 due to internal wear.

  FIG. 6 is a flowchart showing the flow of control for failure determination of the wave gear reduction mechanism 21 using the initial position learning time of the variable compression ratio mechanism.

  In S21, it is determined whether or not the initial position learning of the variable compression ratio mechanism that is performed in a state where the internal combustion engine is stopped is performed. If the initial position learning is being performed, the process proceeds to S22. finish. In S22, the initial position learning time described above is detected. In S23, it is determined whether or not the detected initial position learning time is equal to or less than a predetermined time T set in advance. If the detected initial position learning time is equal to or less than the predetermined time T, the process proceeds to S24, and the failure due to internal wear is a wave gear deceleration. It is determined that the problem has occurred in the mechanism 21. If it is not less than the predetermined time T, the current routine is terminated assuming that no failure due to internal wear has occurred in the wave gear reduction mechanism 21.

  Further, when wear progresses inside the wave gear reduction mechanism 21, rattling of the meshing portion of the internal teeth 32 and the external teeth 34 in the wave gear reduction mechanism 21 increases. Therefore, when there is a backlash in the meshing portion of the internal gear 32 and the external tooth 34 in the dynamic gear speed reduction mechanism 21, the drive is performed until the initial position on the high compression ratio side or the low compression ratio side is reached, compared with the case where there is no backlash. When the motor 20 is rotated, the drive motor 20 rotates excessively by this backlash.

Therefore, as a reference example, when learning the initial position of the variable compression ratio mechanism, the reference for the rotation amount of the output shaft 20a of the drive motor 20 corresponding to the initial position on the high compression ratio side or the low compression ratio side of the variable compression ratio mechanism. By comparing the value with the amount of rotation of the output shaft 20a of the drive motor 20 at the initial position, the wear state in the wave gear reduction mechanism 21 can be detected, and the failure of the wave gear reduction mechanism 21 due to internal wear is detected. Can be detected.

  Specifically, in a state where the meshing portion of the internal gear 32 and the external gear 34 in the wave gear reduction mechanism 21 is not rattled, the control shaft 18 projects against the stopper on the low compression ratio side with respect to the output of the output shaft sensor 22. An initial count value corresponding to the rotational position of the output shaft 20a from the applied state until it hits the stopper on the high compression ratio side is assigned.

  The count value of the pulse signal detected by the output shaft sensor 22 with the control shaft 18 abutted against the high compression ratio side stopper, and the initial count value when the control shaft 18 is abutted against the high compression ratio side stopper When the detected count value does not coincide with the initial count value, the meshing portion of the internal gear 32 and the external gear 34 in the wave gear reduction mechanism 21 is rattled, and a failure due to internal wear causes a wave gear reduction mechanism. 21 is determined to have occurred.

  Further, the count value of the pulse signal detected by the output shaft sensor 22 with the control shaft 18 abutted against the stopper on the low compression ratio side, and the initial count value when the control shaft 18 is abutted against the stopper on the low compression ratio side If the detected count value does not match the initial count value, it may be determined that a failure due to internal wear has occurred in the wave gear reduction mechanism 21.

  If the initial count value is set so as to increase from the low compression ratio side to the high compression ratio side, it is detected with respect to the initial count value when judging when abutting against the stopper on the high compression ratio side. When the count value increases, it is determined that a failure due to internal wear has occurred in the wave gear reduction mechanism 21. Further, in the case of making a determination when abutting against the stopper on the low compression ratio side, when the detected count value becomes smaller than the initial count value, a failure due to internal wear occurs in the wave gear reduction mechanism 21. It is determined that

  FIG. 7 is a flowchart showing a flow of control for failure determination of the wave gear reduction mechanism 21 using the count value of the pulse signal of the output shaft sensor 22.

  In S31, it is determined whether or not the initial position learning of the variable compression ratio mechanism that is executed in a state where the internal combustion engine is stopped. If the initial position learning is in progress, the process proceeds to S32. Otherwise, the current routine is executed. finish. In S32, by the initial position learning, the control shaft 18 is rotated until it comes into contact with the stopper on the high compression ratio side or the stopper on the low compression ratio side. In S33, the count value of the pulse signal of the output shaft sensor 22 in a state where the control shaft 18 is abutted against the stopper is detected. In S34, the count value of the pulse signal detected by the output shaft sensor 22 with the control shaft 18 abutted against the stopper is compared with the initial count value when the control shaft 18 is abutted against the stopper, and the detected count is compared. If the value does not match the initial count value, the process proceeds to S35, where it is determined that a failure due to internal wear has occurred in the wave gear reduction mechanism 21. When the detected count value coincides with the initial count value, it is determined that a failure due to internal wear has not occurred in the wave gear reduction mechanism 21, and the current routine is terminated.

  If a torque sensor is provided on the output shaft 20a of the drive motor 20 and the motor torque generated in the drive motor 20 can be directly detected, a failure of the wave gear reduction mechanism 21 due to internal wear can be detected from the detected motor torque. It is also possible to detect. If the inside of the wave gear reduction mechanism 21 is worn, the motor torque when the drive motor 20 is driven is smaller than that when the inside is not worn, and therefore the inside of the wave gear reduction mechanism 21 is worn. If the motor torque in a state where it is not stored is stored, a failure of the wave gear reduction mechanism 21 due to internal wear can be detected.

DESCRIPTION OF SYMBOLS 20 ... Drive motor 21 ... Wave gear reduction mechanism 22 ... Output shaft sensor 31 ... Internal gear 32 ... Internal tooth 33 ... Flexible external gear 34 ... External tooth 35 ... Wave generator 36 ... Bolt hole 37 ... Bottom part 38 ... Tube part 39 ... Bolt 40 ... Flange 41 ... Ball bearing

Claims (2)

A variable compression ratio mechanism capable of changing an engine compression ratio by changing at least one of a top dead center position and a bottom dead center position of a piston of an internal combustion engine by changing a rotational position of a control shaft by an actuator;
A wave gear reduction mechanism that is provided between the actuator and the control shaft and decelerates rotation of the output shaft of the actuator and transmits the rotation to the control shaft;
Actuator torque detection means for detecting actuator torque generated in the actuator,
The actuator torque is a compression ratio holding torque that is generated by the actuator when the engine compression ratio is kept constant. When the compression ratio holding torque is equal to or greater than a predetermined value, the wave gear reduction mechanism A failure diagnosis device for an internal combustion engine , wherein the meshing rate of the internal gears decreases and it is determined that there is a failure due to wear in the wave gear reduction mechanism . A variable compression ratio mechanism capable of changing an engine compression ratio by changing at least one of a top dead center position and a bottom dead center position of a piston of an internal combustion engine by changing a rotational position of a control shaft by an actuator;
A wave gear reduction mechanism that is provided between the actuator and the control shaft and decelerates rotation of the output shaft of the actuator and transmits the rotation to the control shaft;
Actuator torque detection means for detecting actuator torque generated in the actuator,
The actuator torque is obtained during initial position learning of the variable compression ratio mechanism by rotating the control shaft to an initial position on the high compression ratio side and an initial position on the low compression ratio side while the internal combustion engine is stopped. A constant torque generated by the actuator,
The time until the initial position on the high compression ratio side changes to the initial position on the low compression ratio side, or the time until the initial position on the low compression ratio side changes to the initial position on the high compression ratio side is set in advance. An internal combustion engine failure diagnosing device, characterized in that , when the time is not longer than a predetermined time, the meshing rate of the gears in the wave gear reduction mechanism decreases and it is determined that there is a failure due to wear in the wave gear reduction mechanism .

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