JP2005069147A - Variable valve system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve system of an internal combustion engine, lifting an engine valve with desired valve characteristic for securing the engine output while not requiring continuous drive to an actuator when a sensor is abnormal. <P>SOLUTION: An engine includes: a working angle varying mechanism for varying the working angle of an intake valve by a motor; a rotating angle sensor for detecting the rotating angle of a motor; and a holding mechanism for mechanically holding the working angle varying mechanism when the holding condition on the working angle is satisfied (the working angle is the maximum value). An electronic control device outputs a holding and transition control command value for putting the working angle varying mechanism in a held state by the holding mechanism to the motor (step 120, 130). After that output, when an intake air quantity varying with a change in the working angle does not satisfy a holding fitting condition suitable for the holding condition (the intake air quantity is above a determination value), the holding and transition control command value is again output to the motor (step 140 to 160). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine that can vary at least one of an intake valve and an exhaust valve provided in the internal combustion engine.

  In recent years, for example, in an internal combustion engine mounted on a vehicle, it has been proposed to provide a variable valve gear that makes valve characteristics such as an operating angle of an intake valve and a maximum lift amount variable according to an engine operating state. . According to this technique, for example, in a low rotation and low load region of an internal combustion engine, the operating angle of the intake valve is reduced to control the amount of air taken into each cylinder through the intake port (intake air amount). By this control, the pumping loss caused by the throttle valve opening control can be reduced, and the fuel consumption can be improved. Also, in the high rotation and high load range, the operating angle of the intake valve can be increased, and the increase in output can be secured by improving the intake charging efficiency.

  As one of the variable valve operating devices, for example, Patent Document 1 describes a technique for continuously changing the operating angle of an intake valve by changing the rotation angle of a control shaft by an actuator such as an electric motor. In this variable valve operating apparatus, the rotation angle of the control shaft is detected by a sensor such as a potentiometer, and the actual operating angle of the intake valve is calculated based on the rotation angle. Further, the target operating angle of the intake valve is calculated based on the engine operating state. When the sensor is normal, the energization of the actuator is feedback-controlled so that the actual working angle becomes the target working angle.

  On the other hand, when the sensor is abnormal, the rotation angle of the control shaft cannot be accurately detected, and accurate calculation of the actual working angle and feedback control based on the actual working angle cannot be performed. On the other hand, since the rotation angle of the control shaft is regulated within a predetermined range by pins, stoppers, etc., the operating angle of the intake valve is held at either the minimum value or the maximum value by switching the rotation direction of the control shaft. It is possible. Therefore, when the sensor is abnormal, either the minimum value or the maximum value is set as the target operating angle. The energization of the actuator is subjected to open loop control so that the target operating angle set in this way is achieved.

In addition to Patent Document 1 described above, Patent Document 2 and Patent Document 3 shown below are listed as prior art documents according to the present invention.
JP 2002-54466 A JP 2000-314329 A JP 2002-349215 A

  By the way, when the sensor is abnormal, it is necessary to energize the actuator continuously in order to keep the working angle of the intake valve at the minimum value or the maximum value, and various electronic parts including an electric motor have a performance capable of withstanding continuous energization. Required. However, using electronic parts that satisfy these requirements inevitably increases costs.

  For this, a mechanism for holding the control shaft at the rotation angle (holding angle) corresponding to the minimum value or the maximum value is provided, and the electric motor is based on the expected energization amount for rotating the control shaft to this holding angle. It is conceivable that the energization is stopped after the energization.

  However, at the expected energization amount, the control shaft may not actually be rotated to the holding angle due to various factors such as a change in the driving state of the vehicle and a change over time of the variable valve gear. Moreover, although it rotated once to the holding angle, it may remove | deviate from a holding angle after that. In these cases, since the intake valve does not lift at a predetermined operating angle, a predetermined amount of air cannot be obtained, and the required engine output cannot be secured and drivability may deteriorate. Such a problem can occur not only in the intake valve, but also in a variable valve apparatus that varies the valve characteristics of the exhaust valve.

  The present invention has been made in view of such circumstances, and its purpose is to lift an engine valve with desired valve characteristics for ensuring engine output while eliminating the need for continuous driving of the actuator when the sensor is abnormal. An object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can be made to operate.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, there is provided a variable valve mechanism that has at least one of an engine valve working angle and a maximum lift amount in an internal combustion engine as a valve characteristic, and changes the valve characteristic by an actuator that operates according to a control command value. A variable valve operating apparatus for an internal combustion engine, comprising: a sensor that detects a valve characteristic of the engine valve; and when the sensor is normal, a control command value corresponding to a detection result of the sensor is output to the actuator. A holding mechanism that mechanically holds the variable valve mechanism in its current state when a predetermined holding condition for valve characteristics is satisfied, and the variable valve mechanism is held by the holding mechanism when the sensor is abnormal. The control command value for holding transition to enter the state to output is output to the actuator, and after the output, the change in the valve characteristic is applied. If the parameter does not meet the holding corresponding condition corresponding to the holding condition regarding the operating state of the internal combustion engine that changes Te, and a control means for outputting the holding transition control command value again the actuator.

  According to the above configuration, when the sensor is normal, a control command value corresponding to the detection result is output to the actuator, and the actuator is operated to change the valve characteristic of the engine valve to a target characteristic.

  On the other hand, when the sensor is abnormal, it becomes impossible to output a control command value corresponding to the detection result of the sensor. However, if the holding condition for the valve characteristic of the engine valve is satisfied, the variable valve mechanism can be held in the state at that time by the holding mechanism. From this, when the sensor is abnormal, instead of the control command value according to the detection result of the sensor, a holding transition control command value for setting the variable valve mechanism to be held by the holding mechanism is output to the actuator. The The valve characteristics are changed by the operation of the actuator in accordance with the hold transition control command value. By this change, basically, the holding condition for the valve characteristics is satisfied, and the variable valve mechanism is mechanically held in the state at that time by the holding mechanism. At this time, if the holding condition is appropriately set in relation to the engine output, the engine output is ensured by satisfying the holding condition as described above. Further, during the holding period, the variable valve mechanism need not be held at that time by the actuator, and the output of the holding transition control command value to the actuator can be stopped.

  However, the holding shift control command value is not a value reflecting the detection result of the sensor, and thus is an expected value. For this reason, due to various factors such as changes in the operating state of the internal combustion engine and changes over time of the variable valve mechanism, the changed valve characteristics may not actually satisfy the holding condition and may not be held by the holding mechanism. is there. In addition, even if the valve characteristic satisfies the holding condition and the holding mechanism performs the holding once, the holding condition may not be satisfied after that.

  In this regard, according to the first aspect of the present invention, the parameter relating to the operating state of the internal combustion engine that changes in accordance with the change in the valve characteristic after the above-described holding transition control command value is output has the holding condition corresponding to the holding condition. It is determined whether the corresponding conditions are met. If the parameter does not satisfy the holding condition, the holding shift control command value is output to the actuator again. In response to this output, the actuator is actuated to change the valve characteristics and satisfy the holding condition.

  Thus, when the valve characteristic satisfies the holding condition when the sensor is abnormal, it is not necessary to continue to output the holding transition control command value to the actuator for continuous driving of the variable valve mechanism. There is no need to use a highly durable actuator or the like. Further, even if the valve characteristic does not satisfy the holding condition, or once the holding condition is satisfied but is not satisfied after that, the variable valve mechanism is held by the holding mechanism, and the engine valve is It is possible to ensure engine output by lifting with valve characteristics.

  According to a second aspect of the present invention, in the first aspect of the present invention, the control means, after the output of the holding transition control command value, if the parameter satisfies the holding appropriate condition, Assume that the output of the holding transition control command value is stopped for a predetermined time.

  According to the above configuration, if the parameter relating to the operating state of the internal combustion engine satisfies the holding appropriate condition after the holding transition control command value is output when the sensor is abnormal, the variable valve mechanism is It can be said that it is in the state which can be hold | maintained by. Accordingly, in this case, the output of the control command value for holding transition is stopped for a predetermined time, but the holding mechanism can hold the variable valve mechanism in the state at that time (the valve characteristic satisfies the holding condition). Is possible. For this reason, it is not necessary to use a highly durable actuator, and the effect of the invention according to claim 1 is further ensured.

  According to a third aspect of the present invention, in the second aspect of the present invention, the control means sets the holding transition control command value if the parameter does not satisfy the holding proper condition after the predetermined time has elapsed. It is assumed that the signal is output again to the actuator.

  Here, even if the parameter once satisfies the holding condition according to the output of the holding transition control command value and the valve characteristic satisfies the holding condition, the parameter may not satisfy the holding condition after that. In this regard, according to the third aspect of the present invention, after the output of the holding transition control command value is stopped for a predetermined time, it is determined whether or not the parameter satisfies the holding appropriate condition. If the holding appropriate condition is not satisfied, the holding shift control command value is output to the actuator again. In response to this output, the actuator is operated to change the valve characteristics to satisfy the holding condition. Therefore, the variable valve mechanism can be held in the current state by the holding mechanism, and the engine output can be secured.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the holding condition is that the operating angle or the maximum lift amount is maximized.
According to the above configuration, when the sensor is abnormal, the actuator is operated by the output of the holding transition control command value to change the valve characteristic. As a result of this change, when the engine valve operating angle or maximum lift amount is maximized and the holding condition is satisfied, even if the output of the holding transfer control command value is stopped, the holding mechanism causes the variable valve mechanism to Retained. Therefore, for example, when the variable valve mechanism changes the valve characteristic of the intake valve, the intake valve is lifted with the valve characteristic that maximizes the operating angle or the maximum lift amount. As a result, the required amount of air can be sucked into the internal combustion engine to ensure engine output.

  According to a fifth aspect of the invention, in the invention according to any one of the first to fourth aspects, the variable valve mechanism changes a valve characteristic of an intake valve, and relates to an operating state of the internal combustion engine. The parameter is an intake air amount or an intake pressure that changes as the valve characteristic is changed by the variable valve mechanism, and the holding appropriate condition is that the parameter is larger than a predetermined value.

  According to the above configuration, when the valve characteristic of the intake valve is changed, the intake air amount and the intake pressure also change with the change. In this way, the intake air amount and intake pressure that are correlated with the valve characteristics are used as parameters relating to the operating state of the internal combustion engine, and these are used to determine the success or failure of the holding appropriate conditions. Even without this, it is possible to determine whether or not the variable valve mechanism is held by the holding mechanism.

  According to a sixth aspect of the invention, in the invention according to any one of the first to fifth aspects, the actuator is a motor that rotates an output shaft when energized and changes a valve characteristic of the engine valve by the rotation. Suppose there is.

  According to the above configuration, when the sensor is abnormal, the holding transition control command value for setting the variable valve mechanism to be held by the holding mechanism is output. The energization according to this output rotates the output shaft of the motor and changes the valve characteristics. With this change, when the holding condition for the valve characteristics is satisfied and the variable valve mechanism is held in that state by the holding mechanism, the variable valve mechanism need not be held in that state by the motor. Therefore, it is not necessary to continue energizing the motor.

  According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the apparatus further includes a rotation restricting member that restricts the output shaft of the motor from rotating beyond an angle corresponding to the holding condition of the valve characteristic. When the sensor is abnormal, the control means energizes the motor until the current flowing through the motor becomes larger than a predetermined value due to the restriction of the rotation restricting member.

  According to the above configuration, a certain rotation angle of the output shaft of the motor corresponds to the holding condition, and when the output shaft tries to rotate beyond this rotation angle, the rotation is restricted by the rotation restricting member. When the motor is continuously energized in such a state where the rotation is restricted, the current flowing through the motor increases. For this reason, it becomes possible to determine whether or not the variable valve mechanism is in a state of being held by the holding mechanism based on the comparison result between the current and the predetermined value. And it can be ensured that the variable valve mechanism is held by the holding mechanism by energizing the motor until the current becomes larger than the predetermined value.

  According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the variable valve mechanism includes a control shaft that is moved in an axial direction by the actuator, and a control shaft on the control shaft. Each of the input arm and the output arm provided to be swingable, the control shaft, and a slider provided between the input arm and the output arm. The swing is transmitted to the output arm through the slider to drive the engine valve, and the displacement of the slider accompanying the movement of the control shaft in the axial direction by the actuator causes the input arm and the output arm to move. It is assumed that the valve characteristic is changed by changing the relative phase difference.

  According to the above configuration, when the camshaft of the internal combustion engine rotates, in the variable valve mechanism, the input arm is swung around the control shaft by the camshaft. This swing is transmitted to the output arm via the slider, and the output arm swings. The corresponding engine valve is driven by the swinging output arm, and air is sucked into the internal combustion engine or exhaust gas is discharged from the internal combustion engine.

  Further, when the control shaft is driven by the actuator and moved in the axial direction, the slider is displaced along with the movement, and the relative phase difference between the input arm and the output arm is changed according to the displacement, and the valve characteristic of the engine valve is changed. Be changed. Here, if the valve characteristic is, for example, the working angle of the engine valve that is substantially proportional to the relative phase difference, the working angle is small when the relative phase difference is small, and the working angle increases as the relative phase difference increases.

  In an internal combustion engine equipped with such a type of variable valve mechanism, when the sensor is abnormal, a control command value for holding transition for setting the variable valve mechanism to be held by the holding mechanism is output to the actuator. When the control shaft and the slider are displaced in the axial direction by the operation of the actuator according to the holding transition control command value, the relative phase difference between the input and output arms is changed according to the displacement, and the valve characteristics of the engine valve are changed. Be changed. By this change, basically, the holding condition for the valve characteristics is satisfied, and the variable valve mechanism is mechanically held in the state at that time by the holding mechanism. At this time, if the holding condition is appropriately set in relation to the engine output, the engine output is ensured by satisfying the holding condition as described above. Further, during this holding period, the actuator does not have to hold the control shaft and the slider in the axial direction so as not to be displaced, and the output of the holding transfer control command value to the actuator can be stopped.

  After the holding transition control command value is output, if the parameter relating to the operating state of the operating state of the internal combustion engine does not satisfy the holding proper condition corresponding to the holding condition, the holding shift control command value is output to the actuator again. . In response to this output, the actuator operates to displace the control shaft and slider in the axial direction, thereby changing the valve characteristics and satisfying the holding condition.

  Therefore, even in an internal combustion engine equipped with the variable valve mechanism of the above type, the effect of the invention of claim 1 can be obtained with certainty.

(First embodiment)
A first embodiment in which the present invention is embodied in a vehicular multi-cylinder gasoline engine (hereinafter simply referred to as an engine) as an internal combustion engine will be described below with reference to FIGS.

  As shown in FIGS. 1 and 2, the engine 11 includes a cylinder block 13 having a plurality of cylinders 12 and a cylinder head 14 mounted thereon. A piston 15 is accommodated in each cylinder 12 so as to be able to reciprocate. Each piston 15 is connected to a crankshaft 16 (see FIG. 2) that is an output shaft via a connecting rod (not shown). The reciprocating motion of each piston 15 is converted into rotational motion by the connecting rod and then transmitted to the crankshaft 16.

  A space surrounded by the piston 15, the cylinder 12 and the cylinder head 14 is a combustion chamber 17. The cylinder head 14 is provided with an intake port 18 and an exhaust port 19 that communicate with each combustion chamber 17.

  In order to open and close these intake / exhaust ports 18, 19, an intake valve 21 and an exhaust valve 22 are supported on the cylinder head 14 for each cylinder 12 so as to reciprocate as engine valves. The intake / exhaust valves 21 and 22 are always urged upward by a valve spring 23. This urging direction is a direction (valve closing direction) in which the intake and exhaust ports 18 and 19 are closed.

  An intake cam shaft 25 having an intake cam 24 is rotatably supported by a support wall 26 substantially above the intake valve 21 in the cylinder head 14 (see FIG. 2). Similarly, an exhaust camshaft 27 is rotatably supported substantially above the exhaust valve 22 in the cylinder head 14. The intake / exhaust camshafts 25 and 27 are drivingly connected to the crankshaft 16 by a timing chain 28, a sprocket (not shown) and the like. Then, the rotation of the crankshaft 16 is transmitted to the intake / exhaust camshafts 25, 27 through the timing chain 28 and the like, and the intake / exhaust valves 21, 22 are reciprocated (lifted) by the rotation of the camshafts 25, 27. The intake / exhaust ports 18 and 19 are opened and closed.

  An intake passage (not shown) is connected to the intake port 18, and air outside the engine 11 passes through the intake passage and the intake port 18 and is taken into the combustion chamber 17. A fuel injection valve (not shown) for injecting fuel toward the combustion chamber 17 is attached to the intake passage corresponding to each cylinder 12. The injected fuel mixes with the intake air introduced into the combustion chamber 17 through the intake port 18 and becomes an air-fuel mixture. Note that the fuel injection valve may be attached to the cylinder head 14 instead of the intake passage so that the fuel is directly injected into the combustion chamber 17.

  A spark plug 29 is attached to the cylinder head 14 corresponding to each cylinder 12. The air-fuel mixture is ignited by electric sparks of the spark plug 29 and explodes and burns. The piston 15 is reciprocated by the high-temperature and high-pressure combustion gas generated at this time, the crankshaft 16 is rotated, and the driving force (output torque) of the engine 11 is obtained.

On the other hand, an exhaust passage (not shown) is connected to the exhaust port 19, and exhaust gas generated in the combustion chamber 17 is discharged to the outside of the engine 11 through the exhaust port 19, the exhaust passage, and the like.
As shown in FIG. 2, at the end of the engine 11 on the timing chain 28 side (left end in FIG. 2), the relative rotational phase of the intake camshaft 25 with respect to the crankshaft 16 is adjusted, and the valve characteristics of the intake valve 21 are adjusted. There is provided a valve timing variable mechanism 31 for advancing or retarding the valve timing (opening / closing period) which is a part of the valve timing. Further, the engine 11 is provided with a variable operating angle mechanism 32 that continuously changes the operating angle and the maximum lift amount, which are part of the valve characteristics of each intake valve 21. These valve timing variable mechanism 31 and operating angle variable mechanism 32 constitute a variable valve mechanism. Here, the operating angle of the intake valve 21 is an angle range for the rotation of the crankshaft 16 from the start of the intake valve 21 to the closing of the valve (see FIG. 10). The maximum lift amount of the intake valve 21 is the amount of movement when the intake valve 21 moves (lifts) to the lowest position. The exhaust valve 22 is not provided with such a variable valve mechanism.

  The operating angle variable mechanism 32 includes an intermediary driving mechanism 33 provided for each cylinder 12, one support pipe 34, one control shaft 35 and one operating angle variable actuator that are common to all the intermediary driving mechanisms 33. It has.

  The support pipe 34 is disposed so as to extend in the arrangement direction of the cylinders 12 (the left-right direction in FIG. 2), and is fixed to the support wall portion 26 as described above. Note that this direction is referred to as an “axial direction” when it is not necessary to distinguish, and when it is necessary to distinguish, it is referred to as an arrow A direction or an arrow B direction. An arrow A direction is a direction approaching the timing chain 28 described above, and is a direction in which the operating angle and the maximum lift amount of the intake valve 21 are reduced. An arrow B direction is a direction away from the timing chain 28, and is a direction in which the operating angle and the maximum lift amount are increased. Due to the through-fixation, the support pipe 34 cannot move in the axial direction and cannot rotate.

  The control shaft 35 is inserted into the support pipe 34 so as to be capable of reciprocating in the axial direction. In order to displace the control shaft 35 in the axial direction and adjust the position in the axial direction, as shown in FIGS. 3 and 4, a rotating body 38 is disposed on the end of the control shaft 35 via a ball screw 37. Is provided. The rotating body 38 is rotatable with respect to the control shaft 35, but displacement in the axial direction is restricted. A worm wheel 39 made of a spur gear is attached to the rotating body 38 so as to be integrally rotatable.

  A motor 41 as a variable working angle actuator is disposed in the vicinity of the rotating body 38. In this embodiment, a direct current motor (DC motor) that generates a rotational force (torque) proportional to or substantially proportional to the current is used as the motor 41. A drive circuit 42 that drives the motor 41 is connected to a battery 44 via a fuse 43.

  On the output shaft 45 of the motor 41, a worm 46 made of a screw-shaped gear is attached, and this worm 46 is engaged with the worm wheel 39. The worm wheel 39 and the worm 46 constitute a worm gear. As is well known, since the friction between the worm wheel 39 and the worm 46 is large, the worm gear is used when transmitting rotation with a large reduction ratio. The worm gear is characterized in that a large load is required to rotate the worm 46 from the worm wheel 39 side.

  The worm gear functions as a holding mechanism 47 for mechanically holding the variable working angle mechanism 32 in the state at that time when predetermined holding conditions for the valve characteristics (working angle, maximum lift amount) are satisfied. The holding condition is that the valve characteristic becomes a characteristic for securing the intake air amount for evacuation travel of the vehicle, and here, “the working angle is the maximum value” is the holding condition.

  In order to restrict the rotation of the output shaft 45, a pin 48 is fixed to the rotating body 38. In the cylinder head 14 and the like, a pair of stoppers 51 and 52 are provided as rotation restricting members at locations corresponding to both ends of the movable range of the pin 48. When the worm wheel 39 is rotated by the motor 41 in the counterclockwise direction, which is the direction in which the pin 48 approaches the stopper 51, the control shaft 35 is displaced in the direction of arrow A (the direction in which the operating angle and the maximum lift amount are reduced). Be made. When the pin 48 is abutted against the stopper 51, further counterclockwise rotation is restricted by the stopper 51. On the contrary, when the worm wheel 39 is rotated by the motor 41 in the clockwise direction, which is the direction in which the pin 48 approaches the stopper 52, the control shaft 35 moves in the direction of arrow B (the direction in which the working angle and the maximum lift amount are increased). ). When the pin 48 is abutted against the stopper 52, further rotation in the clockwise direction is restricted by the stopper 52. Thus, the worm wheel 39 can rotate within an angular range in which the movement of the pin 48 is restricted by the stoppers 51 and 52.

  Each intermediate drive mechanism 33 is provided between the intake camshaft 25 and the intake valve 21 (see FIG. 1). As shown in FIGS. 5 to 7, each mediation drive mechanism 33 includes an input arm 53 and a pair of output arms 54 and 55 arranged on both sides in the axial direction. The input arm 53 and the output arms 54 and 55 are connected to each other at their opposite ends by fitting. The input arm 53 and the output arms 54 and 55 of each intermediary drive mechanism 33 are disposed between the support wall portions 26 and 26, and the movement in the axial direction is restricted by the support wall portions 26 and 26 (see FIG. 7).

  The input arm 53 includes a pair of support pieces 56, 56, and a roller 58 is supported by a shaft 57 at the tips of both support pieces 56, 56. Each of the output arms 54 and 55 includes a base circular portion 59 and a nose 61 having a substantially triangular shape and a cam surface 61a that is curved in a concave shape.

  A power transmission slider 62 is disposed between the support pipe 34 and the input arm 53 and the output arms 54 and 55. The slider 62 is supported on the support pipe 34 so as to be rotatable and movable in the axial direction. In order to connect the slider 62 to the control shaft 35 so that power can be transmitted, a groove 63 extending in the circumferential direction is formed on the inner peripheral surface of the slider 62. The groove 63 communicates with the outside of the slider 62 through a through hole 64 provided in the slider 62 (see FIG. 8). In the support pipe 34, elongated holes 65 extending in the axial direction are formed at locations corresponding to the respective mediation drive mechanisms 33. A locking pin 66 inserted through the above-described through hole 64 is disposed in the groove 63 and the long hole 65, and one end thereof (the lower end in FIGS. 7 and 8) is press-fitted and fixed to the control shaft 35. Yes. Further, a bush 67 is fixed to the other end portion (the upper end portion in FIGS. 7 and 8) of the locking pin 66 located in the groove portion 63.

  Therefore, as described above, the support pipe 34 is fixed to the cylinder head 14 (support wall portion 26). However, as the control shaft 35 moves in the axial direction, the locking pin 66 is inserted into the long hole 65 of the support pipe 34. By moving in, the slider 62 can be moved in the axial direction via the bush 67. Further, since the slider 62 itself is locked to the locking pin 66 and the bush 67 by the groove 63 extending in the circumferential direction, the axial position is determined by the locking pin 66 and the bush 67. It can be rotated about the axis.

  In order to transmit power between the input arm 53 and the slider 62, a helical spline 53a that is twisted clockwise toward the output arm 54 side is formed on the inner peripheral surface of the input arm 53. Correspondingly, as shown in FIG. 6, a helical spline 62 a twisted in the same direction is formed in an intermediate portion of the outer peripheral surface of the slider 62 in the axial direction, and this meshes with the helical spline 53 a of the input arm 53 described above. Are combined.

  Further, in order to transmit power between the output arms 54 and 55 and the slider 62, the inner peripheral surfaces of the output arms 54 and 55 are opposite to the helical spline 53 a of the input arm 53, that is, the input arm 53. Helical splines 54b and 55c that are twisted in the counterclockwise direction as they move away from the output arm 54 are formed. Correspondingly, helical splines 62b and 62c twisted in the same direction are formed at both ends in the axial direction of the outer peripheral surface of the slider 62, and these are meshed with the helical splines 54b and 55c of the output arms 54 and 55, respectively. ing. Thus, the helical splines 53a and 62a and the helical splines 54b, 55c, 62b and 62c are twisted in the opposite directions. For this reason, the slider 62 rotates while being displaced in the same direction in conjunction with the axial movement of the control shaft 35, so that a torsional force in the opposite direction is applied to the input arm 53 and the output arms 54 and 55. The relative phase difference between the input arm 53 and the output arms 54 and 55 changes. Also, by setting the helical direction of the helical splines 53a, 54b, 55c, 62a, 62b, and 62c, the relative phase difference between the input / output arms 53 to 55 causes the slider 62 to move in the direction of arrow A (direction in which the working angle is reduced). It becomes smaller as it is displaced.

  As shown in FIG. 1, the roller 58 of each intermediary drive mechanism 33 is in contact with the intake cam 24 of the intake camshaft 25, and a substantially downward force by the intake cam 24 is generated by the rotation of the intake camshaft 25. 58. Further, a spring 68 is disposed between the support piece 56 and the cylinder head 14 in a compressed state, and the roller 58 is always pressed against the intake cam 24 by the spring 68. The input arm 53 swings up and down with the control shaft 35 as a fulcrum so that a substantially downward force that changes according to the cam profile of the intake cam 24 and an upward force by the spring 68 are balanced.

  On the other hand, a rocker arm 69 is disposed between the intake valve 21 and the output arms 54 and 55, and the swing of the output arms 54 and 55 is transmitted to the intake valve 21 via the rocker arm 69. That is, each rocker arm 69 is supported by an adjuster 71 at a base end portion (left end portion in FIG. 1) 69a so as to be swingable, and in contact with the intake valve 21 at a tip end portion (right end portion in FIG. 1) 69b. Yes. Then, the urging force of the valve spring 23 is applied to the tip end portion 69 b of the rocker arm 69 through the intake valve 21, and the roller 72 of the rocker arm 69 is in contact with the base circular portion 59 or the nose 61 of both the output arms 54 and 55. .

  Accordingly, when the intake camshaft 25 rotates, in the mediation drive mechanism 33, the input cam 53 swings up and down around the control shaft 35 by the intake cam 24. This swing is transmitted to the output arms 54 and 55 via the slider 62, and the output arms 54 and 55 swing up and down. By these swinging output arms 54 and 55, the corresponding intake valves 21 are driven and opened. As the valve is opened, air is sucked from the intake port 18 into the combustion chamber 17.

  Further, when the control shaft 35 is moved in the axial direction by the motor 41, the relative phase difference between the input arm 53 and each of the output arms 54 and 55 is changed with respect to the swinging direction of the input / output arms 53 to 55. . With this change, the valve characteristics (working angle and maximum lift amount) of each intake valve 21 change continuously. When the slider 62 is displaced by the maximum amount in the direction of arrow A and the relative phase difference is small, both the operating angle and the maximum lift amount are small, and the intake air amount per cylinder is small. When the relative phase difference increases with the movement of the slider 62 in the arrow B direction, both the operating angle and the maximum lift amount increase, and the intake air amount increases.

  As shown in FIGS. 1 and 6, in the intermediate drive mechanism 33, a substantially downward force is applied to the roller 58 of the input arm 53 by the intake cam 24. This force is transmitted to the slider 62 through the helical splines 53a and 62a. As described above, the helical splines 53a and 62a are twisted clockwise toward the output arm 54 side. A load in the direction of arrow A acts on the slider 62 as a thrust direction force determined by the twist direction and the force from the intake cam 24.

  On the other hand, the valve spring 23 applies a substantially upward force to the output arms 54 and 55 via the intake valve 21 and the rocker arm 69. This force is transmitted to the slider 62 through the helical splines 54b and 55c and 62b and 62c. As described above, the helical splines 54b, 55c and 62b, 62c are twisted in the opposite direction to the helical splines 53a, 62a. A load in the direction of arrow A acts on the slider 62 as a thrust force determined by these twist directions and the force from the valve spring 23.

Thus, the slider 62 tends to move in the direction of arrow A due to the load acting through the input arm 53 and the load acting through both the output arms 54 and 55.
9A and 9B show the state of the mediation drive mechanism 33 when the motor 41 moves the control shaft 35 by the maximum amount in the direction of arrow B in FIG. The slider 62 is located at the end in the arrow B direction in the movable range. At this time, the relative phase difference between the input arm 53 and the output arms 54 and 55 is maximized.

  In particular, FIG. 9A shows a state where the intake cam 24 is in contact with the roller 58 of the mediation drive mechanism 33 at the base circle portion 24a. In this state, a portion close to the nose 61 in the base circular portion 59 of both the output arms 54 and 55 is in contact with the roller 72 of the rocker arm 69. For this reason, the intake valve 21 is closed (the lift amount is “0”).

  When the intake camshaft 25 rotates, the roller 58 is pushed down by the nose 24b, and the input arm 53 swings downward. This swing is transmitted to the output arms 54 and 55 via the slider 62, and the output arms 54 and 55 swing downward. By these swings, the cam surface 61a of the nose 61 immediately contacts the roller 72 of the rocker arm 69, and the roller 72 is pushed using substantially the entire range of the cam surface 61a as shown in FIG. 9B. Lower. By this depression, the rocker arm 69 swings downward with the base end portion 69a as a fulcrum, the distal end portion 69b of the rocker arm 69 largely depresses the intake valve 21, and the intake port 18 is greatly opened (opened). The working angle and the maximum lift amount are maximized. As the intake valve 21 is opened, the amount of air flowing into the combustion chamber 17 from the intake port 18 is maximized.

  When the control shaft 35 is moved in the direction of arrow A in FIG. 2 by the motor 41 from the above state, the slider 62 is displaced in the same direction while rotating in conjunction with it. The rotation of the slider 62 applies torsional forces in opposite directions to the input arm 53 and the output arms 54 and 55, and the relative phase difference between the input arm 53 and the output arms 54 and 55 changes. The relative phase difference decreases as the displacement amount of the slider 62 increases.

  When the base circle part 24 a of the intake cam 24 contacts the roller 58 of the mediation drive mechanism 33, the contact point of the base circle part 59 of the output arms 54 and 55 with the roller 72 of the rocker arm 69 moves away from the nose 61. For this reason, even if the output arms 54 and 55 swing, the roller 72 of the rocker arm 69 continues to contact the base circle 59 without contacting the cam surface 61a of the nose 61 for a while.

  Thereafter, the cam surface 61a pushes down the roller 72, and the rocker arm 69 is swung downward with the base end portion 69a as a fulcrum. However, the roller 72 is initially separated from the nose 61, so that the cam surface 61a can be used. Less. As a result, the rocking angle of the rocker arm 69 becomes small, and both the operating angle and the maximum lift amount become small. In this way, the intake valve 21 opens the intake port 18 with a smaller working angle and maximum lift than at the maximum. As the intake valve 21 is opened, the amount of air flowing into the combustion chamber 17 from each intake port 18 decreases according to the amount of displacement of the slider 62 in the arrow A direction.

  Thus, by adjusting the position of the slider 62 through the control shaft 35 by the motor 41, the operating angle of the intake valve 21 driven by the output arms 54 and 55 between the lift amount patterns shown in the graph of FIG. It is possible to continuously adjust the maximum lift amount.

  As shown in FIG. 3, various sensors for detecting the state of each part are attached to the vehicle. As a part of these sensors, a crank angle sensor 75, a pair of rotation angle sensors 76 and 77, an air flow meter 78, and an intake pressure sensor 79 are used. The crank angle sensor 75 detects a crank angle that is a rotation angle of the crankshaft 16. The detection value of the crank angle sensor 75 is also used when detecting the engine rotation speed, which is the rotation speed of the crankshaft 16. Each rotation angle sensor 76, 77 detects the rotation angle (motor rotation angle) of the output shaft 45 of the motor 41 through the rotation angle of the worm wheel 39 in order to detect the valve characteristics (working angle and maximum lift amount) of the intake valve 21. To detect. The air flow meter 78 detects the intake air amount that is the amount of air flowing through the intake passage, and the intake pressure sensor 79 detects the intake pressure that is the pressure of intake air in the intake passage.

  Here, the relationship shown in FIG. 11 is observed between the motor rotation angle and the valve characteristics (working angle, maximum lift amount). 11 indicates a region where the rotation of the output shaft 45 of the motor 41 is restricted when the pin 48 hits the stoppers 51 and 52. The movable range of the output shaft 45 of the motor 41 includes a variable area and a holding area. In the variable region, the operating angle is minimized when the pin 48 is in contact with one stopper 51, and the operating angle increases as the output shaft 45 rotates toward the side where the pin 48 moves away from the stopper 51. In the variable region, when the pin 48 approaches the stopper 52 and the motor rotation angle reaches a predetermined value X, the operating angle becomes maximum. In the holding area, the maximum value of the operating angle in the variable area described above is held regardless of the rotation of the output shaft 45. Accordingly, if the rotation angle of the worm wheel 39 is detected by the rotation angle sensors 76 and 77, the actual operating angle of the intake valve 21 can be uniquely determined from the detection result.

  The holding area is set for the following reason. As described above, the load on the side (arrow A direction) that reduces the operating angle is applied to the slider 62 through the input arm 53 and the output arms 54 and 55. This load is also transmitted to the motor 41 via the control shaft 35, the ball screw 37, and the like. If the load exceeds the force (holding force) for holding the worm wheel 39 in a stopped state when the energization of the motor 41 is stopped, the output shaft 45 of the motor 41 rotates to the balanced position and the slider 62 is moved. There is a risk of movement in the direction of arrow A. Therefore, in order to prevent the operating angle from being affected even if the slider 62 moves slightly as described above, a holding region is provided in which the operating angle is maintained at the maximum value even if the motor rotation angle changes.

  As shown in FIG. 3, the vehicle is provided with an electronic control unit (ECU) 81 as a control means for controlling each part of the motor 41 and the like based on signals from the various sensors 75 to 79. . The ECU 81 is configured around a microcomputer, and a central processing unit (CPU) performs arithmetic processing according to a control program, initial data, a control map, and the like stored in a read-only memory (ROM). Various controls are executed based on this. The calculation result by the CPU is temporarily stored in a random access memory (RAM). In addition, the ECU 81 includes a current detection circuit 82 that detects a current value (also referred to as a motor current value) that flows through the motor 41.

  As one of the controls performed by the ECU 81, there is a working angle control of the intake valve 21. In this control, the target operating angle is calculated based on parameters relating to the operating state of the engine 11, such as the engine speed and the engine load. The engine load is obtained based on, for example, parameters (including intake pressure) related to the intake air amount of the engine 11. On the other hand, based on the rotation angle detected by the rotation angle sensors 76 and 77, the actual operating angle of the intake valve 21 corresponding to the rotation angle is calculated. The energization of the motor 41 is feedback-controlled so that the actual operating angle becomes the target operating angle described above. By controlling the energization of the motor 41 in this way, the operating angle (maximum lift amount) of the intake valve 21 is adjusted to a value suitable for the operating state of the engine 11.

  When the rotation angle sensors 76 and 77 are abnormal, accurate information on the motor rotation angle cannot be obtained, and accurate calculation of the actual working angle and feedback control based on the actual working angle cannot be performed. However, if the holding condition (the operating angle is the maximum value) for the valve characteristic of the intake valve 21 is satisfied, the operating angle variable mechanism 32 can be held in that state by the holding mechanism 47. Therefore, the ECU 81 diagnoses the rotation angle sensors 76 and 77 in addition to the operating angle control, and performs a fail-safe process when one of the sensors 76 and 77 is abnormal. Next, specific contents of the fail-safe process will be described with reference to the flowchart shown in FIG.

  In step 100, the ECU 81 first determines whether any one of the rotation angle sensors 76 and 77 is abnormal. In this determination, for example, it is determined whether or not the deviation of the motor rotation angle detected by both rotation angle sensors 76 and 77 is larger than a predetermined value. Here, if both the rotation angle sensors 76 and 77 are normal, the motor rotation angle detected by them should be the same value. From this, when the deviation is larger than a predetermined value, it is determined that one rotation angle sensor 76 (or 77) is abnormal. However, in this case, it is difficult to specify the rotation angle sensor 76 (or 77) that is abnormal.

  If the determination condition of step 100 is not satisfied (sensor normal), each process of the fail safe routine is terminated. On the other hand, if the determination condition of step 100 is satisfied (sensor abnormality), the process proceeds to step 110. In step 110, as a holding transition control command value for setting the operating angle of the intake valve 21 to a value that satisfies the holding condition (maximum value), energization / non-energization is performed at the duty ratio D1 and the duty ratio D1. The time T1 to be calculated is calculated. The duty ratio is a ratio of the energization time in one cycle including the energization time and the non-energization time.

  Subsequently, in step 120, the energization time for the motor 41 is controlled by the duty ratio D1. In step 130, it is determined whether or not the time T1 has elapsed since the processing of step 120 was started. If this determination condition is not satisfied, the process returns to step 120. If the determination condition is satisfied, the process proceeds to step 140. As described above, in steps 120 and 130, the process of controlling the energization time over time T 1 by the duty ratio D 1 is performed by using the holding transition control command value for setting the operating angle variable mechanism 32 to be held by the holding mechanism 47. This corresponds to the process of outputting to 41.

  Here, generally, when the operating angle and the maximum lift amount of the intake valve 21 are small, the intake air amount is small, and the intake air amount increases as the operating angle and the maximum lift amount increase. Therefore, even if it is not based on the detection results of the rotation angle sensors 76 and 77, by using the actual intake air amount by the air flow meter 78, the operating angle and the maximum lift amount of the intake valve 21 are estimated, and they are maximized. It is possible to determine whether or not Therefore, in step 140, it is determined whether the intake air amount by the air flow meter 78 is larger than a predetermined determination value α. Here, as the determination value α, an intake air amount that can be taken when the operating angle of the intake valve 21 reaches the maximum value or a value close thereto is set. Note that the determination condition in step 140 corresponds to a holding appropriate condition corresponding to the holding condition (the operating angle is the maximum value).

  If the determination condition of step 140 is not satisfied, the operating angle is not the maximum value despite the output of the holding transition control command value, and the operating angle variable mechanism 32 is still held by the holding mechanism 47. It is thought that it is not in a state. Therefore, in step 150, the energization time for the motor 41 is controlled by the predetermined duty ratio D2. In step 160, it is determined whether or not a predetermined time T2 has elapsed from the start of the processing in step 150. If this determination condition is not satisfied, the process returns to step 150. If the determination condition is satisfied, the process proceeds to step 190. In this way, in steps 150 and 160, the process of controlling the energization time over time T2 by the duty ratio D2 corresponds to the process of outputting the holding transition control command value to the motor 41 again when the holding appropriate condition is not satisfied. To do.

  On the other hand, when the determination condition of step 140 is satisfied, it is considered that the operating angle is the maximum value and the operating angle variable mechanism 32 is held by the holding mechanism 47. Therefore, in step 170, the duty ratio is set to “0”, and the energization time of the motor 41 is controlled (energization is stopped). Next, in step 180, it is determined whether or not a predetermined time T3 has elapsed from the start of processing in step 170. If this determination condition is not satisfied, the process returns to step 170. If the determination condition is satisfied, the process proceeds to step 190.

  In step 190 which has shifted from step 160 or 180, it is determined whether or not a predetermined engine stop condition is satisfied. Examples of the engine stop condition include “the starter switch is turned off”. If this determination condition is not satisfied, the process returns to step 140 described above. And the process of step 140-190 is repeatedly performed over the period until an engine stop condition is satisfied. By these processes, the energization time is controlled or the energization is stopped by the duty ratio D2. When the determination condition of step 190 is satisfied, the series of processing of the fail safe routine is ended.

  When each process is performed according to the above-described fail-safe routine, the motor rotation angle, the duty ratio in energization control, and the intake air amount change as shown in FIGS. 13 and 14, for example.

  When it is detected that either one of the rotation angle sensors 76 and 77 is abnormal at the timing t1 in FIG. 13, processing is performed in the order of steps 100 → 110 → 120 → 130. When the energization time is controlled by the duty ratio D1, the output shaft 45 of the motor 41 rotates toward the side where the pin 48 approaches the stopper 52, and the control shaft 35 and the slider 62 move in the arrow B direction. In the mediation drive mechanism 33, the relative phase difference between the input arm 53 and each of the output arms 54 and 55 increases, the operating angle and the maximum lift amount of the intake valve 21 increase, and the intake air amount increases.

  If the intake air amount is larger than the determination value α at the timing t2 when the time T1 has elapsed from the start of control of the energization time based on the duty ratio D1, the processing is performed in the order of steps 140 → 170. The duty ratio is set to “0”, and energization to the motor 41 is stopped. This energization stop is continued from timing t2 to timing t3 when time T3 elapses by the processing of steps 170 → 180. If the engine stop condition is not satisfied and the situation where the intake air amount is larger than the determination value α continues after timing t3, the process is performed in the order of steps 180 → 190 → 140 → 170, and the energization stop is continued. This energization stop is continued until the determination condition of step 180 is satisfied, that is, until timing t4 when time T3 elapses from timing t3. If the intake air amount continues to be larger than the determination value α after timing t14, the process is performed in the order of steps 140 → 170 → 180 → 190 → 140. Through a series of these processes, the energization stop over time T3 is repeatedly performed until the engine stop condition is satisfied.

  On the other hand, FIG. 14 shows that the intake air amount once exceeds the determination value α by the control of the energization time based on the duty ratio D1, but the intake air amount during the energization stop period (timing t2 to t3) by the steps 170 and 180. This shows a case where the value decreases and becomes smaller than the judgment value α. In this case, the determination condition of step 140 is not satisfied, and processing is performed in the order of steps 140 → 150. The energization time is controlled over time T2 by the duty ratio D2. This control increases the operating angle and the maximum lift amount of the intake valve 21 and increases the intake air amount. In the course of this increase, the intake air amount becomes larger than the determination value α. The control of the energization time based on the duty ratio D2 is performed until the determination condition of step 160 is satisfied, that is, from timing t3 to timing t5 when the time T2 elapses. If the intake air amount is greater than the determination value α at timing t5, the determination condition of step 140 is satisfied, so that the processing is performed in the order of step 190 → 140 → 170 and the energization is stopped as in FIG. . This energization stop is continued until the determination condition of step 180 is satisfied. Thereafter, if the situation where the intake air amount is larger than the determination value α continues, processing is performed in the order of steps 140 → 170 → 180 → 190 → 140, and a situation occurs where the intake air amount is smaller than the determination value α. For example, processing is performed in the order of steps 140 → 150 → 160 → 190 → 140. Thus, during the period until the engine stop condition is satisfied, the energization time is controlled or the energization is stopped by the duty ratio D2 according to the intake air amount.

According to the first embodiment described in detail above, the following effects can be obtained.
(1) The output shaft 45 is rotated by energization, and the motor 41 that changes the operating angle and the maximum lift amount of the intake valve 21 by the rotation is used as a variable operating angle actuator. When the rotation angle sensor 76 or 77 is abnormal, a holding transition control command value for setting the operating angle variable mechanism 32 to be held by the holding mechanism 47 is used instead of the control command value according to the detection result. The output is made to the drive circuit 42 (steps 120 and 130). The valve characteristic (working angle, maximum lift amount) is changed by the operation of the motor 41 in accordance with the holding transition control command value, and basically the holding condition for the valve characteristic is satisfied. The mechanism 32 is held in its current state. Therefore, during this holding period, it is not necessary to hold the operating angle variable mechanism 32 in the state at that time by the motor 41, and the output of the holding transition control command value to the motor 41 is stopped, that is, the motor 41. Can be de-energized (step 170). There is no need to continue energizing the motor 41, and various electronic components including the highly durable motor 41 need not be used. As a result, it is possible to avoid an increase in cost associated with using a highly durable electronic component.

  (2) As shown in FIG. 11, a holding region is set for the relationship between the motor rotation angle and the working angle, and in this region, the working angle is set to the maximum value regardless of the motor rotation angle. For this reason, if the load in the direction of arrow A (direction to reduce the operating angle) is applied to the slider 62 during engine operation, if the motor rotation angle is within this holding region when the rotation angle sensors 76 and 77 are abnormal, for example. Even when the energization of the motor 41 is stopped, it is possible to suppress the motor rotation angle from deviating from the holding region against the load. The load changes according to the operating state such as the engine speed, but the operating angle can be maintained at the maximum value regardless of the change. As a result, the working angle control can be performed with high accuracy, and it can be suppressed that the working angle varies and the rotation of the crankshaft 16 becomes unstable.

  (3) Since the holding transition control command value is not a value reflecting the detection results of the rotation angle sensors 76 and 77, it is an expected value. For this reason, due to various factors such as changes in the operating state of the engine 11 and changes in the working angle variable mechanism 32 over time, the changed valve characteristics do not actually satisfy the holding conditions and are not held by the holding mechanism 47. There is a fear. Further, even if the valve characteristic satisfies the holding condition and the holding mechanism 47 holds the valve once, the holding condition may not be satisfied after that.

  In this regard, in the first embodiment, after the holding transition control command value is output, the amount of intake air that changes in accordance with the change in the valve characteristic is greater than the holding appropriate condition (determination value α) corresponding to the holding condition. ) Is satisfied (step 140). If the intake air amount does not satisfy the holding appropriate condition, the holding shift control command value is output again (steps 150 and 160). In response to this output, the motor 41 operates, and the intake air amount changes accordingly, and the holding proper condition is satisfied.

  In this way, even if the operating angle does not satisfy the holding condition or once satisfies the holding condition, but does not satisfy the holding condition after that, the operating angle variable mechanism 32 is held by the holding mechanism 47, and the intake air The valve 21 can be lifted with a valve characteristic that provides a predetermined amount of intake air.

  (4) When the rotation angle sensor 76 or 77 is abnormal, after the holding transition control command value is output, if the intake air amount satisfies the holding appropriate condition, the operating angle variable mechanism 32 is held by the holding mechanism 47. It can be said that it is in a state to obtain. Therefore, in this case, energization to the motor 41 is stopped for the time T3 (steps 170 and 180), but the operating angle variable mechanism 32 is held by the holding mechanism 47 in the current state (the valve characteristic satisfies the holding condition). can do. For this reason, the effect of said (1) that it is not necessary to use a highly durable electronic component can be made more reliable.

  (5) Even if the intake air amount once satisfies the holding appropriate condition in accordance with the output of the holding transition control command value, the intake air amount may not satisfy the holding appropriate condition thereafter. In this regard, in the first embodiment, after the energization of the motor 41 is stopped for the time T3, it is determined whether or not the intake air amount satisfies the holding appropriate condition (steps 170 → 180 → 190 → 140). If the holding appropriate condition is not satisfied, the holding shift control command value is output again (step 140 → 150). In response to this output, the motor 41 is actuated to change the operating angle to satisfy the holding condition. Therefore, it is possible to reliably lift the intake valve 21 at a predetermined operating angle (maximum value) while eliminating the need for continuous energization of the motor 41.

  (6) The holding condition is that the operating angle becomes the maximum value. For this reason, when the rotation angle sensor 76 or 77 is abnormal, if the motor 41 is operated by the output of the holding transfer control command value and the operating angle is maximized and the holding condition is satisfied, the output of the holding transfer control command value is output. Even when the operation is stopped, the holding mechanism 47 can hold the variable operating angle mechanism 32 in the current state. Therefore, the intake valve 21 can be lifted by the valve characteristic with the maximum operating angle and the maximum lift amount by the operating angle variable mechanism 32, and the required amount of air is sucked into the combustion chamber 17 of the engine 11 and the vehicle is retracted. Therefore, engine output can be secured.

  (7) When the operating angle and the maximum lift amount of the intake valve 21 are changed, the intake air amount also changes with the change. In this regard, in the first embodiment, the amount of intake air that has a correlation with the valve characteristics is used as a parameter relating to the operating state of the engine 11, and this is used to determine the success or failure of the appropriate holding condition (step 140). For this reason, it is possible to determine whether or not the operating angle variable mechanism 32 is held by the holding mechanism 47 without using the detection result of the rotation angle sensor 76 or 77.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment in the content of the holding transition control command value output when the rotation angle sensor 76 or 77 is abnormal. Here, a phenomenon is used in which the motor current value increases rapidly when the motor 41 is energized after the pin 48 hits the stopper 52. The motor current value when this phenomenon occurs is also called a motor lock current. FIG. 15 is a flowchart showing the fail safe routine corresponding to FIG. 12 described above, and FIGS. 16 and 17 are timing charts corresponding to FIGS. 13 and 14 described above. Since mechanical parts such as the operating angle variable mechanism 32 are the same as those in the first embodiment, description thereof will be omitted.

  In the fail-safe routine shown in FIG. 15, first, in step 200, it is determined whether one of the rotation angle sensors 76 and 77 is abnormal. If this determination condition is not satisfied (sensor normal), the process of the fail-safe routine is terminated. If satisfied (sensor abnormality), the process proceeds to step 210. In step 210, the energization time for the motor 41 is controlled by the duty ratio D11. Here, the duty ratio D11 is set to a value that allows the operating angle to be a value that satisfies the holding condition (maximum value) when energization is performed for a certain period of time with the duty ratio D11. .

  Next, in step 220, it is determined whether a motor lock current is detected. In this determination, it is determined whether or not the motor current value detected by the current detection circuit 82 is larger than a predetermined lock determination value β. The lock determination value β is set to a value larger than the value that the motor current value can take when the pin 48 moves between the stoppers 51 and 52. If the determination condition in step 220 is not satisfied, the process returns to step 210 described above. Therefore, the energization time for the motor 41 is controlled by the duty ratio D11, and the output shaft 45 of the motor 41 is rotated by the current corresponding to the energization time. As a result of this rotation, the pin 48 hits the stopper 52. If energization is continued thereafter, the motor current value becomes larger than the lock determination value β. When the pin 48 is in contact with the stopper 52 or when the pin 48 is close to the stopper 52, the motor rotation angle belongs to the holding region described above. In this holding region, even if the energization to the motor 41 is stopped, the operating angle is basically held at the maximum value. As described above, in steps 210 and 220, the process of controlling the energization time based on the duty ratio D11 until the motor lock current is detected is for holding transition for setting the operating angle variable mechanism 32 to be held by the holding mechanism 47. This corresponds to the process of outputting the control command value to the motor 41.

  If the determination condition of step 220 is satisfied, the duty ratio is set to “0” in step 230 and energization of the motor 41 is stopped. Next, in step 240, it is determined whether or not a predetermined time T11 has elapsed from the start of the processing in step 230. If this determination condition is not satisfied, the process returns to step 230. If the determination condition is satisfied, the process proceeds to step 250. In this way, when the motor lock current is detected, the energization of the motor 41 is stopped for the time T11.

  Subsequently, in steps 250 to 300, processing similar to that in steps 140 to 190 in the first embodiment is performed. In step 250, it is determined whether the amount of intake air by the air flow meter 78 is greater than a determination value α. If this determination condition is not satisfied, the working angle is once maximized, but it is considered that the working angle has decreased during energization stop. Therefore, in step 260, the energization time for the motor 41 is controlled by the predetermined duty ratio D12. In step 270, it is determined whether or not a predetermined time T12 has elapsed from the start of the processing in step 260. If this determination condition is not satisfied, the process returns to step 260. If the determination condition is satisfied, the process proceeds to step 300. As described above, in steps 260 and 270, the process of controlling the energization time over time T12 by the duty ratio D12 corresponds to the process of outputting the holding transition control command value to the motor 41 again when the holding appropriate condition is not satisfied. To do.

  On the other hand, when the determination condition of step 250 is satisfied, the operating angle is the maximum value, and it is considered that the operating angle variable mechanism 32 is held by the holding mechanism 47. Therefore, in step 280, the duty ratio is set to “0” and the energization to the motor 41 is stopped. Next, in step 290, it is determined whether or not a predetermined time T13 has elapsed from the start of processing in step 280. If this determination condition is not satisfied, the process returns to step 280, and if it is satisfied, the process proceeds to step 300.

  In step 300, which has shifted from step 270 or 290, it is determined whether an engine stop condition is satisfied. If this determination condition is not satisfied, the process returns to step 250 described above. And the process of step 250-300 is repeatedly performed over the period until an engine stop condition is satisfied. By these processes, the energization time is controlled or the energization is stopped by the duty ratio D12. When the determination condition of step 300 is satisfied, a series of processing of the fail safe routine is ended.

  When each process is performed according to the above-described fail safe routine, the motor rotation angle, the duty ratio in the energization control, the motor current value, and the intake air amount change as shown in FIG. 16 or FIG.

  When it is detected that one of the rotation angle sensors 76 and 77 is abnormal at the timing t11 in FIG. 16, the processing is performed in the order of steps 200 → 210. When the energization time for the motor 41 is controlled by the duty ratio D11, the output shaft 45 of the motor 41 rotates toward the side where the pin 48 approaches the stopper 52, and the control shaft 35 and the slider 62 move in the arrow B direction. In the mediation drive mechanism 33, the relative phase difference between the input arm 53 and each of the output arms 54 and 55 increases, the operating angle and the maximum lift amount of the intake valve 21 increase, and the intake air amount increases. In the course of this increase, the intake air amount becomes larger than the determination value α.

  Even if the pin 48 hits the stopper 52, if the motor lock current is generated at the timing t12 by energization, the determination condition of step 220 is satisfied. In this case, the process of step 230 is performed, the duty ratio is set to “0”, and the energization to the motor 41 is stopped. This energization stop is continued from timing t12 until timing t13 when time T11 elapses. Even after timing t13, if the situation where the intake air amount is larger than the determination value α continues, the processing is performed in the order of step 250 → 280, and the energization stop is continued. This energization stop is continued until the determination condition of step 290 is satisfied, that is, until timing t14 when time T13 elapses from timing t13. If the intake air amount continues to be larger than the determination value α after the timing t14, the processing is performed in the order of steps 250 → 280 → 290 → 300 → 250. Through these series of processes, the energization stop over time T13 is repeatedly performed during the period until the engine stop condition is satisfied.

  On the other hand, FIG. 17 shows that the intake air amount once exceeded the determination value α by the control of the energization time based on the duty ratio D11, but during the energization stop period (timing t12 to t13) according to the processing of steps 230 and 240, The case where the amount of intake air decreases and becomes smaller than the judgment value α is shown. In this case, the determination condition of step 250 is not satisfied, and processing is performed in the order of steps 250 → 260 → 270. The energization time for the motor 41 is controlled over time T12 by the duty ratio D12. This control increases the operating angle and the maximum lift amount of the intake valve 21 and increases the intake air amount. In the course of this increase, the intake air amount becomes larger than the determination value α. The control of the energization time based on the duty ratio D12 is continued until the determination condition of Step 270 is satisfied, that is, from the timing t13 to the timing t15 when the time T12 elapses. When the amount of intake air is greater than the determination value α at timing t15, processing is performed in the order of steps 250 → 280, and energization is stopped. This energization stop is continued until the determination condition of step 290 is satisfied, that is, until timing t16 when time T13 elapses from timing t15. If the situation where the intake air amount is larger than the determination value α continues after timing t16, the processing is performed in the order of steps 250 → 280 → 290 → 300 → 250, and a situation occurs where the intake air amount is less than the determination value α. For example, processing is performed in the order of steps 250 → 260 → 270 → 300 → 250. Thus, during the period until the engine stop condition is satisfied, the energization time is controlled or the energization is stopped by the duty ratio D12 according to the intake air amount.

Therefore, according to the second embodiment, the following effects can be obtained in addition to the above (1) to (7).
(8) If the output shaft 45 tries to rotate even after the pin 48 hits the stopper 52, the motor current value becomes larger than the lock determination value β. In the second embodiment, this phenomenon is used to determine whether or not the operating angle variable mechanism 32 is held by the holding mechanism 47 based on the comparison result between the motor current value and the lock determination value β. I am doing so. For this reason, by controlling the energization time for the motor 41 until the motor current value becomes larger than the lock determination value β based on the determination result, the operating angle variable mechanism 32 is surely held by the holding mechanism 47. be able to.

Note that the present invention can be embodied in another embodiment described below.
Generally, when the operating angle (maximum lift amount) of the intake valve 21 is small, the intake pressure is low, and the intake pressure increases as the operating angle (maximum lift amount) increases. Therefore, in each of the above-described embodiments, the intake pressure may be changed to the intake air amount, and the engine operating state may be changed in accordance with the change in the operating angle of the intake valve 21. In this case, the processing content of step 140 in FIG. 12 and step 250 in FIG. 15 is “whether the intake pressure by the intake pressure sensor is higher than a predetermined determination value”. It can be estimated whether or not the operating angle of the intake valve 21 is maximized even with such a change.

  A mechanism other than the worm gear described above may be employed as the holding mechanism. For example, when a ball screw type motor is used as an actuator, a stopper that protrudes into the ball groove and stops the movement of the ball may be provided as a holding mechanism. In this case, the movement (stroke) of the control shaft in the axial direction is restricted by stopping the movement of the ball, and the variable valve mechanism is held in that state.

  ・ "The operating angle or the maximum lift amount is a predetermined value other than the maximum value" is used as a holding condition for the valve characteristics, and when this holding condition is satisfied, the holding mechanism holds the variable valve mechanism. It may be.

  The variable valve mechanism may be one in which one of the operating angle and the maximum lift amount of the intake / exhaust valves 21 and 22 is a valve characteristic, and the valve characteristic is changed by an actuator that operates according to a control command value.

The present invention can also be applied to an internal combustion engine provided with a variable valve mechanism that changes the valve characteristics of the exhaust valve 22 instead of or in addition to the intake valve 21.
A variable working angle mechanism or a variable maximum lift amount mechanism other than the type used in each embodiment may be used as a variable valve mechanism.

-An electric actuator other than the motor described above may be used as the actuator of the variable valve mechanism. An actuator other than the electric actuator may be used.
A sensor other than the rotation angle sensors 76 and 77 described above may be used as a sensor for detecting the valve characteristics of the intake / exhaust valves 21 and 22.

  The diagnosis (abnormality detection) of the rotation angle sensor in steps 100 and 200 of the fail safe routine may be performed in a manner different from the above embodiments.

The fragmentary sectional view of the engine upper part in a 1st embodiment which materialized the present invention. The top view which shows the cylinder head upper part containing a working angle variable mechanism. 6 is a schematic diagram showing a relationship between a working angle variable mechanism, a holding mechanism, and the like. The partial perspective view which shows a holding mechanism. The perspective view which shows a mediation drive mechanism. The side view which shows the slider etc. in a mediation drive mechanism. Sectional drawing which shows the internal structure of a mediation drive mechanism. The fragmentary sectional view which shows the relationship between the control shaft, support pipe, slider, etc. in a mediation drive mechanism. (A), (b) is a fragmentary sectional view which shows the effect | action of a mediation drive mechanism. The characteristic view which shows the valve characteristic of an intake / exhaust valve. The characteristic view which shows the relationship between a motor rotation angle and a working angle. The flowchart which shows the procedure of a fail safe process. The timing chart which shows the aspect of a motor rotation angle, a duty ratio, and the change of intake air amount. The timing chart which shows the aspect of a motor rotation angle, a duty ratio, and the change of intake air amount. The flowchart which shows the procedure of the fail safe process in 2nd Embodiment of this invention. The timing chart which shows the aspect of a change of a motor rotation angle, a duty ratio, a motor electric current value, and intake air amount. The timing chart which shows the aspect of a change of a motor rotation angle, a duty ratio, a motor electric current value, and intake air amount.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 21 ... Intake valve (engine valve), 22 ... Exhaust valve (engine valve), 25 ... Intake camshaft, 27 ... Exhaust camshaft, 32 ... Working angle variable mechanism (variable valve operating mechanism) 35) control shaft, 41 ... motor (actuator), 45 ... output shaft, 47 ... holding mechanism, 51, 52 ... stopper (rotation restricting member), 53 ... input arm, 54, 55 ... output arm, 62 ... Slider, 76, 77 ... Rotation angle sensor, 81 ... ECU (control means), α ... judgment value, β ... lock judgment value.

Claims (8)

A variable valve mechanism that changes at least one of a working angle and a maximum lift amount of an engine valve in an internal combustion engine as a valve characteristic and changes the valve characteristic by an actuator that operates according to a control command value, and detects the valve characteristic of the engine valve A variable valve operating apparatus for an internal combustion engine that outputs a control command value according to a detection result of the sensor to the actuator when the sensor is normal.
A holding mechanism that mechanically holds the variable valve mechanism in its current state when a predetermined holding condition for the valve characteristic is satisfied;
When the sensor is abnormal, a control signal value for holding transition for setting the variable valve mechanism to be held by the holding mechanism is output to the actuator, and after the output, changes according to the change of the valve characteristics. An internal combustion engine comprising: a control means for outputting the holding transition control command value to the actuator again when a parameter relating to an operating state of the internal combustion engine does not satisfy a holding proper condition corresponding to the holding condition. Variable valve gear. The control means stops the output of the hold transition control command value for a predetermined time after the output when the parameter satisfies the hold appropriate condition after the output of the hold shift control command value. A variable valve operating apparatus for an internal combustion engine according to claim 1. 3. The variable valve for an internal combustion engine according to claim 2, wherein the control means outputs the holding transition control command value to the actuator again if the parameter does not satisfy the holding proper condition after the predetermined time has elapsed. apparatus. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the holding condition is that the operating angle or the maximum lift amount is maximized. The variable valve mechanism changes the valve characteristic of the intake valve, and the parameter relating to the operating state of the internal combustion engine is an intake air amount or an intake pressure that changes as the valve characteristic is changed by the variable valve mechanism. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the holding appropriate condition is that the parameter is larger than a predetermined value. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the actuator is a motor that rotates an output shaft when energized and changes a valve characteristic of the engine valve by the rotation. The motor further comprises a rotation restricting member for restricting the output shaft of the motor from rotating beyond an angle corresponding to the holding condition of the valve characteristic, and the control means is configured to prevent a current flowing through the motor when the sensor is abnormal. The variable valve operating apparatus for an internal combustion engine according to claim 6, wherein the motor is energized until it becomes larger than a predetermined value due to restriction of the rotation restricting member. The variable valve mechanism is
A control shaft that is moved in the axial direction by the actuator;
An input arm and an output arm provided on the control shaft so as to be swingable,
The control shaft and a slider provided between the input arm and the output arm are provided, and the swing of the input arm by the cam shaft of the internal combustion engine is transmitted to the output arm via the slider. The engine valve is driven, and the valve characteristic is changed by changing the relative phase difference between the input arm and the output arm due to the displacement of the slider accompanying the axial movement of the control shaft by the actuator. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 7.

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