JP2008051111A - Valve driving system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve driving system using a motor for efficiently opening/closing intake valves or exhaust valves of an internal combustion engine having a plurality of cylinders. <P>SOLUTION: The valve driving system 10 to be applied for the internal combustion engine 1 having the plurality of cylinders 2 drives the intake valves 4 or the exhaust valves 5 of the cylinders 2. The valve driving system 10 comprises a plurality of valve drive devices 11A, 11B provided for driving the intake valves 4 or the exhaust valves 5 in the mutually different cylinders 2 of the internal combustion engine 1 and each having the electric motor 12 as a driving source for generating rotating motion and a power transmission mechanism 13 for converting the rotating motion of the electric motor 12 into the opening/closing motion of the valves 4, 5 to be driven and transmitting it, and a motor control device 40 for controlling the operation of the electric motor 12 of each of the plurality of valve drive devices depending on the operated condition of the internal combustion engine 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a valve drive system that drives the intake valve or exhaust valve of an internal combustion engine.

  An intake valve and an exhaust valve of a general internal combustion engine are opened and closed by power extracted from a crankshaft of the internal combustion engine. In recent years, however, attempts have been made to drive intake valves and exhaust valves by electric motors. For example, Patent Document 1 discloses a valve drive device that opens and closes an intake valve by driving a camshaft with a motor. Further, a valve drive device that is intended for an EGR valve, but converts the rotation of the motor into a linear opening / closing motion of the valve using a screw mechanism provided in the valve stem is also known (patent). Reference 2).

JP-A-8-177536 JP-A-10-73178

  The device that converts the rotation of the motor into a valve opening / closing motion by a screw mechanism requires a large amount of motor rotation required to open and close the valve and is inefficient. It is not suitable as a drive device for valves and exhaust valves.

  On the other hand, when the camshaft is rotated by a motor, the intake valve and the exhaust valve can be driven efficiently. However, in a multi-cylinder internal combustion engine generally used as a power source for vehicles, a camshaft is shared between a plurality of cylinders arranged in a row. If such a shared camshaft is simply driven by a motor, a change in the operation of the camshaft affects the operating characteristics of all intake valves and exhaust valves driven by the camshaft. Therefore, the degree of freedom of operation characteristics obtained by controlling the motor is not so high.

Accordingly, the present invention can efficiently open and close an intake valve or an exhaust valve of an internal combustion engine having a plurality of cylinders with a motor, and can further increase the degree of freedom related to the operation characteristics of each valve. an object of the present invention is to provide a valve drive system of the engine.

The valve drive system of the present invention is applied to an internal combustion engine having a plurality of cylinders, and is a valve drive system for an internal combustion engine for driving an intake or exhaust valve provided in each cylinder. Are provided to drive the valves of the cylinders different from each other, and an electric motor as a driving source for generating a rotational motion, and the rotational motion of the electric motor is converted into an opening / closing motion of a valve to be driven using a cam And a plurality of valve drive devices each having a power transmission mechanism for transmitting and transmitting, and motor control means for controlling the operation of the electric motor of each of the plurality of valve drive devices according to the operating state of the internal combustion engine. The motor control means sets a control amount of the electric motor in consideration of a control state related to the intake or exhaust characteristics of the internal combustion engine, and relates to the intake or exhaust characteristics of the internal combustion engine. The Rukoto further include an abnormality judging means for judging the presence or absence of abnormality of the valve-driving system on the basis of the correction amount with respect to the control amount of the electric motor given by consideration of the control state, to solve the problems described above (claim 1).

According to the valve drive system of the present invention, by providing a plurality of valve drive devices, it is possible to give appropriate operation characteristics according to the operating state of the internal combustion engine to the intake valves or the exhaust valves of the plurality of cylinders. Can do .

It can not be controlled to the target as the intake characteristics or exhaust characteristics of the intake valves or operating the internal combustion engine if the deviation from the target of the control of the exhaust valves, fuel economy, performance degradation, inconveniences such as reduction of exhaust emissions occur. On the other hand, according to the valve drive system of the present invention, the control amount of the electric motor is adjusted so that the shift is reduced if the control state is deviated from the target in consideration of the control state relating to the intake or exhaust characteristics. Such inconvenience can be eliminated.

When any abnormality occurs in the valve drive system, the absolute value of the control amount of the electric motor becomes excessive or excessive, or the change amount of the control amount becomes excessive. By monitoring the correction amount relating to the control amount of the electric motor in the valve drive system of the present invention, it is possible to determine whether or not an abnormality has occurred in the valve drive system without using an abnormality detection sensor.

Na us, in the valve drive system of the present invention, may be driven intake valve or the exhaust valve of each different cylinders of a plurality of valve drive. Therefore, the valve driving device may be provided independently for each cylinder, or a valve driving device may be provided independently for the intake valve and the exhaust valve of each cylinder. On the other hand, some or all of the valve drive devices may drive intake valves or exhaust valves of two or more cylinders different from each other. In particular, if the intake valve open period or the exhaust valve open period is not overlapped between cylinders, even if the intake valve or exhaust valve of those cylinders is driven by a common electric motor, each cylinder The operation characteristics of the intake valve or the exhaust valve can be changed without being affected by the operation of the intake valve or the exhaust valve driven by a common electric motor.

In the valve drive system of the present invention, the motor control means calculates a friction torque acting on the rotation of the cam for each crank angle of the internal combustion engine, and calculates the calculated friction torque to a target air-fuel ratio and a current air-fuel ratio. The deviation from the air-fuel ratio of the motor is changed so as to be eliminated, and the drive current loaded on the electric motor is calculated as the control amount based on the friction torque after the change. The abnormality may be determined when the torque change exceeds an allowable level (claim 2). In this case, the friction torque acting on the cam rotation is changed so as to eliminate the difference between the target air-fuel ratio and the current air-fuel ratio, and the drive current of the electric motor is changed based on the friction torque after the change. Calculated. That is, the output torque of the electric motor is controlled without excess or deficiency corresponding to the increase or decrease of the friction torque. For this reason, it is possible to suppress variations in the rotational speed of the cam due to the influence of fluctuations in the friction torque, and to accurately control the cam operating characteristics with respect to the target value. Further, since the drive current of the electric motor is calculated based on the friction torque thus changed, and the output torque of the electric motor is controlled by the drive current, the valve drive system does not depend on only the control target value. The output torque of the electric motor can be appropriately controlled according to the actual state. Even if the drive current of the electric motor is normal, if the friction torque is significantly changed, there is a possibility that one of the valve drive systems has malfunctioned and the intake or exhaust valves are not driven correctly. high. In this embodiment, when the change of the friction torque exceeds the allowable level, it is determined that the valve drive system is abnormal, so that the abnormality can be appropriately determined. In addition, it is not necessary to provide a separate sensor for monitoring the operating state of the valve drive system for abnormality diagnosis, and an increase in cost can be prevented.

In order to realize such an abnormality determination, for example, the motor control means includes a peak value of a variation amount of the friction torque with respect to a predetermined base friction torque and a maximum lift of a crank angle of the internal combustion engine to which the peak value is given. The friction torque is changed by correcting at least one of a deviation amount from a position, and the abnormality determination unit is configured to detect the friction torque when an increase / decrease amount of at least one of the peak value and the deviation amount exceeds a threshold value. It may be determined that the abnormality is the case where the change in the value exceeds the allowable level (Claim 3).

Contact name the friction torque in the present invention means a rotation resistance which is loaded to the drive source of the cam based on a mechanical structure from the electric motor up to the intake valve or exhaust valve. The frictional force generated in the mechanism from the drive source to the intake or exhaust valve increases the friction torque in the positive direction, and the repulsive force of the spring means (valve spring) that pushes the intake and exhaust valves back in the closing direction is Increase friction torque in the negative direction. When controlling the electric motor, it is necessary to output the torque necessary to rotate the cam against the friction torque, and the control of the electric motor is realized by increasing or decreasing the control variable (parameter) associated with the output torque. Is done. The setting and adjustment of the control amount of the electric motor in the present invention means such setting and adjustment of the control variable.

When said unfavorable action torque is a negative value, it may be performed generator by the electric motor by driving the electric motor at a rotational movement of the cam side (claim 4). This increases the efficiency of the valve drive system in the case, or to reduce the battery capacity required for driving the cam, as possible out to set a smaller generating capacity of alternator mounted as a generator on a vehicle.

Motor rotation position detection means for detecting the rotation position of the electric motor is attached to the electric motor, and the motor control means is a cam position for specifying the rotation position of the cam based on the detection result of the rotation position of the electric motor. You may provide a specific means (Claim 5 ). By estimating the cam position from the rotational position of the motor, there is no need to provide separate sensors for detecting the cam position.

Set in the case of the M, N> M, and N, when M is an integer no common divisor other than 1, the N 6 or less: the reduction ratio between the cam and the electric motor N (Claim 6 ). With such a setting, the initial position of the cam can be easily detected, and detection errors can be suppressed.

The motor control means rotates the electric motor according to a predetermined condition when the internal combustion engine is in a predetermined state, and drives the electric motor that appears in correlation with a change in the friction torque of the cam during the rotation. may be provided with an initialization means to grasp the rotation position of the cam based on a change in state (claim 7). The friction torque of the cam correlates with the opening / closing state of the intake valve or the exhaust valve by the cam, and the friction torque is generally reversed in the vicinity of the cam position where the lift amount of the intake valve or the exhaust valve becomes maximum. On the other hand, the friction torque affects the driving state of the electric motor. For example, if the output torque of the electric motor is kept constant, the rotational speed of the motor decreases as the friction torque increases, and the rotational speed of the motor increases as the friction torque decreases. If the rotation speed of the electric motor is kept constant, the output torque of the motor increases as the friction torque increases, and the output torque of the motor decreases as the friction torque decreases. If such a correlation is utilized, the position of the cam can be specified only by monitoring the driving state of the motor. It should be noted that the cam position is determined at the time when such a change has occurred by utilizing the fact that the change in the rotational speed or the change in the output torque of the electric motor at the start of opening or closing of the intake valve or exhaust valve becomes a predetermined state. May be specified. In this case, the driving power required to specify the cam position can be reduced. Further, when the internal combustion engine is stopped, interference between the intake valve or the exhaust valve and the piston can be avoided.

The initialization means rotates the electric motor when the internal combustion engine is stopped to grasp the rotational position of the cam, and stores and holds information indicating the grasped rotational position of the cam even during the stop period of the internal combustion engine. The motor control means specifies the rotational position of the cam based on the information stored in the storage device and starts control of the electric motor at the next start of the internal combustion engine. (Claim 8 ). In this case, it is not necessary to perform processing by the initialization means to grasp the rotational position of the cam when starting the internal combustion engine. Therefore, the internal combustion engine can be started quickly.

It said motor control means may be provided with a valve rotation executing device which drives the electric motor to rotate the valve about its axis at a predetermined timing in stopping the internal combustion engine (claim 9). In this case, the carbon attached to the valve and its seat (valve seat) can be scraped off by rotating the valve. It is also possible to prevent uneven wear of the valve by changing the contact position of the valve with respect to a driving member such as a rocker arm around the axis of the valve.

The motor control means includes a drive mode of the electric motor according to an operating state of the internal combustion engine, a forward rotation mode for driving the electric motor only in a forward rotation direction, and a forward / reverse rotation mode for rotating the electric motor forward and backward. Mode switching means for switching between them may be provided (claim 10 ). In this case, the cam amount is limited by rotating the cam forward and backward at low rotation and low load, and the cam is rotated at high speed and with small torque by inertia of the camshaft etc. at high rotation and high load. The driving state of the cam can be properly used.

Before SL motor control means, the working angle of the driven valve lift characteristic, or at least one of the operating characteristics of the maximum lift amount so as to change the operation of the electric motor to the operating state of the internal combustion engine It can be controlled accordingly (claim 11 ). In this case, the operation of the intake valve and the exhaust valve can be changed more flexibly as compared with the conventional valve drive device that changes only the opening / closing timing. Note that the operating angle changes if the rotational speed of the electric motor is increased or decreased while the intake valve or the exhaust valve is open, and the lift characteristics change if the rotational speed changes, that is, the acceleration changes. The lift characteristic is grasped as a characteristic relating to the correspondence relationship between the lift amount of the intake valve or the exhaust valve and the crank angle. Regarding the lift amount, the intake valve or exhaust valve is controlled by switching the cam rotation direction and reversing the cam at an earlier stage than reaching the maximum lift position where the lift amount of the intake valve or exhaust valve reaches the maximum. The lift amount can be limited to be smaller than the maximum lift amount.

  As described above, according to the valve drive system of the present invention, by providing a plurality of valve drive devices, each of the intake valves or the exhaust valves of the plurality of cylinders corresponds to the operating state of the internal combustion engine. Appropriate operating characteristics can be given. In particular, when at least one of the operating angle, the lift characteristic, or the maximum lift amount of the intake valve or the exhaust valve is changed by the operation control of the electric motor, the conventional valve drive device that changes only the opening / closing timing. In comparison, the operation of the intake valve and the exhaust valve can be changed more flexibly.

[First Embodiment]
FIG. 1 shows an internal combustion engine 1 incorporating a valve drive system according to a first embodiment of the present invention. The internal combustion engine 1 is configured as a multi-cylinder in-line gasoline engine in which a plurality (four in the figure) of cylinders (cylinders) 2... 2 are arranged in one direction, and a piston 3 is mounted on each cylinder 2 so as to be movable up and down. ing. Two intake valves 4 and two exhaust valves 5 are provided above each cylinder 2, and these intake valves 4 and exhaust valves 5 are linked to the vertical movement of the piston 3 to drive the valve drive system 10. By being opened and closed at, intake to the cylinder 2 and exhaust from the cylinder 2 are performed.

  The valve drive system 10 includes valve drive devices 11A... 11A, one provided on the intake side of each cylinder 2, and valve drive devices 11B ... 11B provided one on the exhaust side of each cylinder 2. Yes. These valve drive devices 11A and 11B both drive the intake valve 4 or the exhaust valve 5 using cams. The configuration of the valve driving device 11A is equal to each other, and the configuration of the valve driving device 11B is equal to each other. FIG. 2 shows intake and exhaust valve drive devices 11 </ b> A and 11 </ b> B provided in association with one cylinder 2. The valve driving devices 11A and 11B have similar configurations to each other. First, the intake side valve driving device 11A will be described.

  The intake-side valve drive device 11 </ b> A has an electric motor (hereinafter sometimes abbreviated as a motor) 12 as a drive source, and power transmission for converting the rotational movement of the motor 12 into a linear opening / closing movement of the intake valve 4. And a mechanism 13. As the motor 12, a DC brushless motor or the like capable of controlling the rotation speed is used. The motor 12 incorporates rotational position detection means such as a resolver and a rotary encoder for detecting the rotational position.

  The power transmission mechanism 13 includes one camshaft 14A, a gear train 15 that transmits the rotational motion of the motor 12 to the camshaft 14A, a rocker arm 16 that drives the intake valve 4, a camshaft 14A, and a rocker arm 16 And a valve characteristic adjusting mechanism 17 interposed therebetween. The cam shaft 14A is provided independently for each cylinder 2. In other words, the cam shaft 14 </ b> A is divided for each cylinder 2. The gear train 15 is synchronized with the motor 12 by transmitting the rotation of the motor gear 18 attached to the output shaft (not shown) of the motor 12 to the cam drive gear 20 integrated with the cam shaft 14A via the intermediate gear 19. To rotate the cam shaft 14A.

  As shown in FIGS. 3 and 4, the cam shaft 14A is provided with a single cam 21A so as to be integrally rotatable. The cam 21A is formed as a kind of plate cam in which a part of a base circle coaxial with the cam shaft 14A is expanded. The profiles (outer contours) of the cam 21A are equal among all the valve drive devices 11A. The profile of the cam 21A is set so as not to generate a negative curvature over the entire circumference, that is, to draw a convex curved surface outward in the radial direction.

  The rocker arm 16 is provided so as to be swingable about the support shaft 22. The intake valve 4 is urged toward the rocker arm 16 by the valve spring 23, whereby the intake valve 4 comes into close contact with a valve seat (not shown) of the intake port and the intake port is closed. The other end of the rocker arm 16 is in contact with the adjuster 24. When the adjuster 24 pushes up the other end of the rocker arm 16, the rocker arm 16 is kept in a state where one end thereof is in contact with the upper end of the intake valve 4.

  The valve characteristic adjusting mechanism 17 functions as an intermediary means for transmitting the rotational motion of the cam 21A to the rocker arm 16 as a rocking motion, and changes the correlation between the rotational motion of the cam 21A and the rocking motion of the rocker arm 16. This also functions as a lift amount and working angle changing means for changing the lift amount and working angle of the intake valve 4.

  As shown in FIG. 5, the valve characteristic adjusting mechanism 17 includes a support shaft 30, an operation shaft 31 disposed through the center of the support shaft 30, and a first ring 32 disposed on the support shaft 30. , And two second rings 33 and 33 arranged on both sides thereof. The support shaft 30 is fixedly attached to a cylinder head or the like of the internal combustion engine 1. The operation shaft 31 is reciprocated in the axial direction (R direction and F direction in FIG. 6) with respect to the support shaft 30 by an actuator (not shown). The first ring 32 and the second ring 33 are supported so as to be slidable in the axial direction and swingable in the circumferential direction with respect to the support shaft 30. A roller follower 34 is rotatably attached to the outer periphery of the first ring 32, and a nose 35 is formed on the outer periphery of the second ring 33.

  As shown in FIG. 6, a slider 36 is provided on the outer periphery of the support shaft 30. The slider 36 is slidable in the axial direction integrally with the operation shaft 31 with respect to the support shaft 30 by engaging a long hole 36 c extending in the circumferential direction with a pin 37 attached to the operation shaft 31. The support shaft 30 is formed with an axial long hole (not shown) that allows the pin 37 to move in the axial direction. A first helical spline 36a and second helical splines 36b and 36b disposed so as to sandwich the first helical spline 36a are integrally provided on the outer periphery of the slider 36. The twisting direction of the second helical spline 36b is opposite to the twisting direction of the first helical spline 36a. On the other hand, a helical spline 32a meshing with the first helical spline 36a is formed on the inner periphery of the first ring 32, and a helical spline 33a meshing with the second helical spline 36b is formed on the inner periphery of the second ring 33. Yes.

  As apparent from FIG. 4, the valve characteristic adjusting mechanism 17 is configured so that the roller follower 34 faces the cam 21 </ b> A and the nose 35 faces one end of the rocker arm 16 corresponding to each intake valve 4. Attached to. When the roller follower 34 comes into contact with the nose portion 21 a and is pushed down along with the rotation of the cam 21 </ b> A, the first ring 32 that supports the roller follower 34 rotates on the support shaft 30, and the rotational motion is transmitted via the slider 36. The second ring 33 is transmitted to the second ring 33 and rotates in the same direction as the first ring 32. The rotation of the second ring 32 causes the nose 35 to push down one end of the rocker arm 16, whereby the intake valve 4 is displaced downward against the valve spring 23 and the intake port is opened. When the nose portion 21a gets over the roller follower 34, the intake valve 4 is pushed up by the force of the valve spring 23 and the intake port is closed. In this way, the rotational movement of the cam shaft 14A is converted into the opening / closing movement of the intake valve 4.

  Further, in the valve characteristic adjusting mechanism 17, when the operation shaft 31 is displaced in the axial direction and the slider 36 is slid with respect to the support shaft 30 as indicated by arrows R and F in FIG. The second ring 33 rotates in opposite directions with respect to the circumferential direction. When the slider 36 is moved in the direction of arrow F, the first ring 32 rotates in the direction of arrow P and the second ring 33 rotates in the direction of arrow Q to increase the circumferential distance between the roller follower 34 and the nose 35. . On the other hand, when the slider 36 is moved in the arrow R direction, the first ring 32 rotates in the arrow Q direction and the second ring 33 rotates in the arrow P direction, so that the circumferential distance between the roller follower 34 and the nose 35 is increased. Decrease. As the distance between the roller follower 34 and the nose 35 increases, the amount by which the nose 35 pushes down the rocker arm 16 increases, and the lift amount and operating angle of the intake valve 4 also increase accordingly. Therefore, the lift amount and operating angle of the intake valve 4 increase as the operating shaft 31 is operated in the direction of arrow F in FIG.

  According to the valve drive device 11A configured as described above, the motor 12 causes the cam shaft 14A to be unidirectional at a speed half the rotational speed of the crankshaft of the internal combustion engine 1 (hereinafter referred to as a basic speed). By driving continuously, the intake valve 4 can be driven to open and close in synchronism with the rotation of the crankshaft, in the same manner as a general mechanical valve drive device that drives the valve with power from the crankshaft. Further, the lift amount and operating angle of the intake valve 4 can be changed by the valve characteristic adjusting mechanism 17. Furthermore, according to the valve drive device 11A, by changing the rotational speed of the camshaft 14A by the motor 12 from the basic speed, the relative relationship between the phase of the crankshaft and the phase of the camshaft 14A is changed, and the intake valve 4 operation characteristics (valve opening timing, valve closing timing, lift characteristics, operating angle, maximum lift amount) can be variously changed.

  On the other hand, as shown in FIG. 2, in the valve drive device 11B on the exhaust valve 5 side, unlike the valve drive device 11A, two cams 21B are provided on the cam shaft 14B, the valve characteristic adjusting mechanism 17 is omitted, and 2 Two cams 21B directly drive the rocker arms 16 respectively. The other parts of the valve drive device 11B are common to the valve drive device 11A, and the description of those common parts is omitted. Similar to the cam 21A, the profile of the cam 21B is a convex curved surface over the entire circumference. Regarding the exhaust valve 5 as well, the operating characteristics of the exhaust valve 5 can be changed variously by changing the driving speed of the camshaft 14B by the motor 12 of the valve drive device 11B.

  As shown in FIG. 2, a motor control device 40 is provided in the valve drive system 10 in order to control the operation characteristics of the motor 12 of the valve drive devices 11A and 11B. The motor control device 40 is configured as a computer having a microprocessor and RAM and ROM as main storage devices thereof, and controls the operation of each electric motor 12 according to a valve control program stored in the ROM. In FIG. 2, the valve driving devices 11 </ b> A and 11 </ b> B of one cylinder 2 are shown, but the motor control device 40 is also used for the valve driving devices 11 </ b> A and 11 </ b> B of other cylinders 2.

  The motor control device 40 includes an A / F sensor 41 that outputs a signal corresponding to the air-fuel ratio of exhaust gas, and an opening degree of a throttle valve that adjusts the intake air amount, as input means for information necessary for controlling the electric motor 12. A throttle opening sensor 42 that outputs a signal corresponding to the accelerator pedal, an accelerator opening sensor 43 that outputs a signal corresponding to the accelerator pedal opening, an air flow meter 44 that outputs a signal corresponding to the intake air amount, and an angle of the crankshaft. Crank angle sensors 45 that output corresponding signals are connected to each other. The electric motor 12 may be controlled by using a value obtained from a predetermined function equation or a map instead of the actual measurement values obtained by these sensors. An output signal from a position detection sensor built in the motor 12 is also input to the motor control device 40.

  Next, control of the motor 12 by the motor control device 40 will be described. In the following, the control of the motor 12 for driving the intake valve 4 of one cylinder 2 will be described, but the same applies to the control of the motor 12 for driving the other intake valves 4. The same applies to the motor 12 that drives the exhaust valve 5.

  FIG. 7 shows a motor drive control routine that the motor control device 40 repeatedly executes at a constant cycle in order to change the output torque of the motor 12 in accordance with the operating state of the internal combustion engine 1. By executing the motor drive control routine of FIG. 7, the motor control device 40 functions as motor control means. In this motor drive control routine, the motor control device 40 first detects the rotational position of the cam 21A based on, for example, the position detection sensor of the motor 12 and the reduction ratio of the gear train 15 in step S1. In step S1, the motor control device 40 functions as cam position specifying means.

  Next, in step S2, the operating state of the internal combustion engine 1 necessary for determining the operation content of the intake valve 4 is detected. For example, the rotational speed (rotational speed) of the internal combustion engine 1, the load factor, and the like are detected based on the output signals of the sensors 41 to 45 described above. In the subsequent step S3, the operation content of the intake valve 4 is determined based on the detection result of the operating state of the internal combustion engine 1. For example, parameters such as the lift amount to be given to the intake valve 4, the phase of the camshaft 14A, the rotational speed, etc. are determined in accordance with the current operating state.

  In subsequent step S4, an estimated value TF of the cam friction torque is obtained by the following equation (1). Here, the rotational resistance loaded on the motor 12 based on the mechanical configuration from the motor gear 18 to the intake valve 4 or the exhaust valve 5 is referred to herein as cam friction torque.

TF (θ + θ3) = Tf + f1 (Tf1, θmax−θ1, θ + θ3) + f2 (
Tf2, θmax + θ2, θ + θ3) (1)
Here, Tf is the base friction torque, f1 is a polynomial approximation function that describes the fluctuation component of the cam friction torque generated by the push back action of the cam 21A by the valve spring 23, and f2 is generated by the push action of the cam 21A by the valve spring 23. A polynomial approximation function describing a fluctuation component of the cam friction torque, θ is a crank angle at the time of execution of control, and θ3 is a time constant determined according to the motor 12. Hereinafter, the equation (1) will be described with reference to FIGS.

  FIG. 8 shows a correspondence relationship between the crank angle θ, the valve lift (the lift amount of the intake valve 4), the cam friction torque TF (θ), and the drive current I (θ) of the motor 12. However, the cam friction TF is shown in a positive direction, that is, a direction that becomes resistance to the rotation of the cam 21A in association with the downward direction in FIG. Further, FIG. 8 shows the cam friction torque TF and the drive current I of the motor 12 when the valve lift amount is changed in two levels. That is, the case where the valve lift amount is large is indicated by a thick line, and the case where the valve lift amount is large is indicated by a thin line.

  As is apparent from FIG. 8, the base friction torque Tf of the first term of the equation (1) acts in the positive direction, and its value is constant regardless of the crank angle θ. That is, the base friction torque Tf indicates a basic rotational resistance applied to the motor 12 when the cam 21A is rotated. Next, the reference position is set at an appropriate position on the horizontal axis in FIG. 8, and the valve lift is the maximum value at a position where the crank angle θ is advanced by θmax from the reference position (hereinafter referred to as the maximum lift position). In this case, the cam friction torque TF (θ) increases in the positive direction with respect to the base friction torque Tf in the process of opening the intake valve 4 before reaching the maximum lift position θmax and exhibits a peak. In the process of closing, the base friction torque Tf decreases in the negative direction. Such a change in the friction torque TF (θ) is such that when the cam 21A opens the intake valve 4 against the valve spring 23, the repulsive force of the valve spring 23 pushes the cam 21A back in the direction opposite to its rotational direction. This is because the repulsive force of the valve spring 23 acts to push the cam 21A in the rotational direction after the repulsive force of the valve spring 23 exceeds the peak.

  Strictly speaking, the fluctuation amount of the cam friction torque TF corresponding to the arbitrary crank angle θ from the base friction torque Tf can be calculated mechanically or mechanically from the configuration of the valve drive device 11A. However, the correlation between the crank angle θ and the variation amount of the cam friction torque TF indicates that the peak values Tf1 and Tf2 of the variation amount of the cam friction torque with respect to the base friction torque Tf and the crank angles at which the peak values Tf1 and Tf2 are given. It can be approximately expressed by a function having θ as deviations θ1 and θ2 from the maximum lift position θmax. The second terms f1 and f2 in the above equation (1) are approximate functions obtained from such a viewpoint. Information for specifying these approximate functions is recorded in the ROM of the motor control device 40.

  The maximum lift position θmax is determined in the process of step S3 in FIG. Further, as shown in FIG. 9, there is a correlation between the maximum lift amount of the intake valve 4 and the base friction torque Tf, peak values Tf1 and Tf2, and crank angle deviation amounts θ1 and θ2, and these relationships are pre- It is recorded in the map format in the ROM of the control device 40. Accordingly, in the process of step S4, the motor control device 40 first obtains the base friction torque Tf, peak values Tf1, Tf2, and crank angle deviation amounts θ1, θ2 corresponding to the current maximum lift amount by referring to the map in the ROM. Then, the cam friction torque TF is obtained by substituting these values and the current crank angle θ specified based on the output of the crank angle sensor 45 into the equation (1). However, when these values are corrected in step S10 or S11 described later, the correction is reflected and the cam friction torque TF is obtained.

  However, when the motor 12 has a response delay and the response delay is given as the crank angle θ by the time constant θ3, the crank angle θ advances by the time constant θ3 from the current crank angle θ. It is necessary to obtain the cam friction torque TF at this time. Therefore, the time constant θ3 is added to the crank angle θ in each of the second term and the third term in the equation (1). Instead of the polynomial approximation functions f1 and f2, the cam friction torque fluctuation component may be obtained by a physical model.

  Returning to FIG. 7, the description will be continued. After calculating the cam friction torque TF, the process proceeds to step S5, where the cam friction torque TF (θ + θ3) is multiplied by a predetermined gain α to obtain the drive current I (θ) of the motor 12 to be given at the present time. In the subsequent step S6, the drive current I (θ) for the motor 12 is set and the motor 12 is driven. As is apparent from FIG. 8, the change in the cam friction torque TF (θ) is reflected in the motor drive current I (θ) given in step S6 by being advanced by the motor time constant θ3. Therefore, when the cam friction torque TF (θ) becomes larger than the base friction torque Tf (when it changes to the lower side in FIG. 8), the output torque of the motor 12 increases accordingly, and the cam friction torque TF (θ ) Becomes smaller than the base friction torque Tf (when it changes to the upper side in FIG. 8), the output torque of the motor 12 also decreases accordingly. Thereby, the output torque of the motor 12 is controlled without excess or deficiency.

  After driving the motor 12, the process proceeds to step S7, where it is determined whether or not the difference between the current drive current I (θ) and the standard drive current I (θ) is within a predetermined threshold λ. The standard drive current I (θ) is a drive current obtained without considering the correction in step S10 or step S11. If it is determined in step S7 that the value is within the threshold λ, the process proceeds to step S8, and a value obtained by subtracting the target air-fuel ratio (target A / F) from the air-fuel ratio (measured A / F) detected by the A / F sensor 41 is a predetermined threshold value. Judge whether or not β or less. Here, the target A / F is a target value of the air-fuel ratio set according to the operating state of the internal combustion engine 1. Since the valve operating characteristics of the intake valve 4 are appropriately set according to the operating state of the internal combustion engine (see step S3), the target A / F is determined as long as the operation state of the intake valve 4 is properly controlled. It corresponds to the air-fuel ratio that will be obtained.

  When the measurement A / F increases beyond the target A / F by exceeding the threshold β and the condition of step S8 is denied, that is, the actual air-fuel ratio deviates more than the threshold β to the rich side with respect to the target air-fuel ratio. If YES in step S10, the flow advances to step S10, and at least one parameter of the crank angle deviation amounts θ1 and θ2 and the cam friction torque fluctuation amounts peak values Tf1 and Tf2 to be substituted into the equation (1) is determined according to the map of FIG. Decrease from the specified value by an amount corresponding to the difference in air-fuel ratio. The decrease in the peak values Tf1 and Tf2 means that these values are changed so as to approach the base friction torque Tf. Due to such a change, the intake valve 4 is controlled in a relatively closing direction, that is, in a direction in which the lift amount is reduced. Accordingly, in step S10, the difference between the measurement A / F and the target A / F is eliminated by reducing the lift amount of the intake valve 4 and relatively reducing the intake air amount.

  On the other hand, if the condition in step S8 is affirmed, the process proceeds to step S9, and it is determined whether or not the value obtained by subtracting the measurement A / F from the target A / F is equal to or less than a predetermined threshold γ. If the condition in step S9 is positive, the current motor drive control routine is terminated. On the other hand, when the measurement A / F decreases below the target A / F by exceeding the threshold γ and the condition of step S9 is denied, that is, the actual air-fuel ratio is leaner than the threshold γ with respect to the target air-fuel ratio. If there is a large deviation, the process proceeds to step S11, and at least one parameter of the crank angle deviation amounts θ1 and θ2 and the cam friction torque fluctuation values Tf1 and Tf2 to be substituted into the equation (1) is set in FIG. Increase from the value specified by the map by an amount corresponding to the difference in air-fuel ratio. The increase in the peak values Tf1 and Tf2 means that these values are changed so as to be away from the base friction torque Tf. Due to such a change, the intake valve 4 is controlled in a direction in which the intake valve 4 opens relatively, that is, in a direction in which the lift amount increases. Therefore, in step S11, the lift between the measurement A / F and the target A / F is eliminated by increasing the lift amount of the intake valve 4 to relatively increase the intake air amount.

  After correcting the variables θ1, θ2, Tf1 or Tf2 in step S10 or S11, the process proceeds to step S12. In step S12, it is determined whether or not the increase / decrease amount of the parameter is larger than the threshold value Ψ. If it is within the threshold Ψ, the process returns to step S4 to calculate the cam friction torque TF. At this time, the corrected values are used for the variables θ1, θ2, Tf1, and Tf2 corrected in step S10 or S11.

  On the other hand, if it is determined in step S12 that the increase / decrease amount is larger than the threshold value Ψ, the valve drive device 11A is regarded as abnormal, and the process proceeds to step S13 to give a predetermined warning to inform the driver of the valve drive device 11A abnormality. I do. For example, a warning light on a vehicle instrument panel is turned on or blinked. Then, the process proceeds to step S15, a predetermined retreat travel process is started, and the motor drive control routine is finished. Further, when the difference in the drive current I (θ) exceeds the threshold λ in step S7, it is regarded as an abnormality of the motor 12, and the process proceeds to step S14 to give a predetermined warning to inform the driver of the abnormality of the motor 12. . For example, a warning light on a vehicle instrument panel is turned on or blinked. Then, the process proceeds to step S15.

  According to the above embodiment, since the output torque of the motor 12 is controlled without excess or deficiency in accordance with the increase or decrease of the cam friction torque, the variation in the rotational speed of the cam shaft 14A due to the influence of the fluctuation of the cam friction torque is suppressed, The operating characteristics of the cam 21A can be accurately controlled with respect to the target value. Therefore, the fuel consumption and power performance of the internal combustion engine 1 are improved, and deterioration of exhaust emission is prevented.

  Further, since the deviation of the air-fuel ratio is specified and the output torque of the motor 12 is controlled so that the deviation is corrected, it depends on the actual state of the valve drive device 11A without depending only on the control target value. Thus, the output torque of the motor 12 can be properly controlled. For example, when the state of the valve driving device 11A is different from that at the time of setting the approximate functions f1 and f2 in FIG. 8 and the map in FIG. 9 due to individual differences and aging of the valve driving device 11A, the difference is different. Appears as an air-fuel ratio shift. Therefore, if the drive current of the motor 12 is controlled so as to correct the deviation of the air-fuel ratio, as a result, the operating characteristics of the intake valve 4 can be appropriately controlled while correctly reflecting the state of the valve drive device 11A. Since the corrected drive current of the motor 12 correctly reflects the lift amount and phase of the intake valve 4, the intake air amount into the cylinder 2 is determined based on the corrected drive current of the motor 12. It can also be calculated correctly.

  Furthermore, according to the above-described embodiment, when the drive current of the motor 12 is set to be significantly larger or smaller than the standard drive current, it is determined that the motor 12 is abnormal (step S7 → S14), and the air-fuel ratio is determined. When the correction amount (increase / decrease amount) of the parameter corresponding to the deviation is larger than the allowable level, it is determined that the valve drive device is abnormal (steps S12 → S13), thereby causing the motor control device 40 to function as an abnormality determination unit. ing. If the drive current of the motor 12 is too large or too small compared to the standard drive current, there is a high possibility that the motor 12 is not operating normally, and even if the drive current is normal, the deviation of the air-fuel ratio is eliminated. When the correction amount necessary for the engine is excessively large in the positive direction or the negative direction, there is a high possibility that one of the valve drive devices 11A is abnormal and the intake valve 4 is not driven correctly. An abnormality in the valve drive system 10 can be appropriately determined. As described above, since the abnormality of the motor 12 and the valve drive device 11A is determined based on the correction amount of the drive current of the motor 12, a sensor for monitoring the operation state of the valve drive device 11A needs to be provided separately for abnormality diagnosis. Cost increase can be prevented.

  The correction of the motor output torque in steps S8 to S11 and the determination of the presence / absence of an abnormality in step S7 or S12 are not unique to the motor output torque feedforward control based on the estimation of the friction torque, but are used for various controls relating to the motor 12. You may carry out in combination. For example, also for feedback control of the output torque of the motor 12 based on the rotational speed of the crankshaft, the output torque can be corrected and the abnormality can be determined as in the example of FIG.

  In the above-described embodiment, the increase / decrease amount obtained in step S10 or S11 is preferably stored in the storage device in the motor control device 40 as the correction amount of the friction torque TF. The storage device in this case is preferably a non-volatile memory such as a backup RAM backed up by a vehicle battery or a rewritable flash ROM that does not require the supply of power for holding the memory. If such a storage device is used, the correction amount is maintained even after the ignition switch is turned off and the internal combustion engine 1 is stopped, and the cam is referenced with reference to the stored correction value from the next start of the internal combustion engine 1. The friction torque TF can be calculated appropriately.

  The feedforward control of the motor output torque based on the prediction of the cam friction torque described above may be executed in parallel with other control related to the motor output torque, or may be executed alone. For example, the cam angle feedback control based on the crank angle detected by the crank angle sensor 45 and the above-described cam friction torque feedforward control may be performed in parallel.

  The valve drive system 10 of the present embodiment has several features in addition to the basic configuration described above for controlling the operation of the intake valve 4 and the exhaust valve 5 in accordance with the operating state of the internal combustion engine 1. . This will be described in order below. Various mechanisms or structures of the intake-side valve drive device 11A described below are also provided in the exhaust-side valve drive device 11B unless otherwise specified, and exhibit the same effects as the valve drive device 11A. It is.

(About cam position detection)
In the valve drive system 10 of the present embodiment, the position of the cam 21A is specified using the rotational position detection means of the motor 12 (see step S1 in FIG. 7). As the rotational position detecting means, a pair of magnetic pole sensors is preferably used. In the magnetic pole sensor, the same number of S poles and N poles are arranged around the output shaft, and while the output shaft rotates in the order of S pole → N pole → S pole or N pole → S pole → N pole. A rotation signal of 0 ° to 360 ° is output. In a normal motor, the number of magnetic poles of the magnetic pole sensor is matched to the number of magnetic poles of the motor 12. For example, if the motor 12 is a 4-pole pair (a pair of S and N poles), the magnetic pole sensor is a 4-pole pair, and if the motor 12 is an 8-pole pair, the magnetic pole sensor is an 8-pole pair. However, in this embodiment, a single pole pair of magnetic pole sensors is used as the position detection sensor of the motor 12 regardless of the number of poles of the motor 12. In this way, since the rotational position of the output shaft of the motor 12 and the output signal of the position detection sensor correspond to 1: 1, there is an advantage that the rotational position of the motor 12 can be easily determined. In particular, when the speed ratio between the motor 12 and the cam shaft 14A is 1: 1, the rotational position of the motor 12 and the rotational position of the cam 21A correspond to 1: 1. This is advantageous because it represents the rotational position of 21A.

  On the other hand, when the reduction ratio from the motor 12 to the camshaft 14A cannot be set to 1: 1 due to the convenience of the gear train 15, etc., it is uniquely determined which rotational position of the cam 21A the rotational position of the motor 12 corresponds to. Since it cannot be determined, the rotational position of the cam 21 </ b> A cannot be controlled unless an initialization operation for specifying the correspondence between the two is performed. The initialization operation can be performed by actually driving the cam 21A and detecting which rotational position of the motor 12 is associated with the predetermined cam angle, but the reduction ratio from the motor 12 to the cam 21A is When N: M (where N> M, and N and M are integers having no common divisor other than 1), the rotational position of the motor 12 corresponding to a specific cam angle among the cam angles 0 to 360 ° (motor The angle) is present at N positions, that is, every 360 / N ° between the cam angles of 0 to 360 °. For example, when the reduction ratio is set to N: M = 5: 3 as shown in FIG. 10, the cam 21A rotates three times while the motor 12 rotates five times, so the cam 21A rotates once. Any one of the five positions (indicated by black circles in the figure) corresponds to a cam angle of 0 °. Therefore, the smaller N is, the easier it is to detect the cam position. If the motor angle corresponding to a specific cam angle is set every 60 ° or more than that in view of the margin for erroneous detection, N is preferably 6 or less.

(Cam initialization operation)
Next, an initialization operation related to the cam position will be described. FIG. 11 shows a cam position initialization routine executed by the motor control device 40 to initialize the cam position. By executing the cam position initialization routine of FIG. 11, the motor control device 40 functions as initialization means. In this routine, the motor control device 40 first activates the motor 12 in step S21 to rotate the cam 21A. At this time, the rotational speed of the motor 12 is fed back using a position signal from the rotational position sensor, and the output torque of the motor 12 is controlled so that the rotational speed is constant. The output torque is controlled by increasing or decreasing the drive current. In the subsequent step S22, cam friction torque is detected using the feedback-controlled drive current. In the next step S23, it is determined whether or not the motor 12 has rotated by an amount corresponding to one rotation of the cam 21A. If not completed, the process returns to step S22. If the cam 21A makes one rotation, the cam is stopped in step S24, and the process proceeds to step S25.

  In step S25, the correspondence between the position of the cam 21A and the rotational position of the motor 12 is specified based on the detection result of the cam friction torque. That is, as shown in FIG. 12A, if the motor speed is constant, there is a correlation between the cam friction torque and the motor output torque, and the cam friction torque from the position Pa where the cam 21A starts to open the intake valve 4 is correlated. Output torque increases, the cam friction torque and the motor output torque are reversed at the position Pb where the nose portion 21a of the cam 21A reaches the extension line of the intake valve 4, the intake valve 4 is completely closed, and the cam 21A is The cam friction torque and the motor output torque converge to the respective base values at the separated position Pc. However, in practice, there is an influence of the motor time constant as shown in FIG. 8, but the time constant of the motor 12 is ignored in FIG.

  If such a relationship between the cam friction torque and the motor output torque is used, at least one of the cam positions Pa, Pb, and Pc is determined, and the correspondence between the determined position and the rotational position of the motor 12 is determined. Can be grasped. Then, using this correspondence, the current cam position (cam angle) is specified in step S25 of FIG. In the subsequent step S26, information on the cam position specified by the initialization operation is stored, and then the initialization operation routine is finished.

  According to the above processing, since the cam position can be specified from the change in the motor output torque, there is an advantage that it is not necessary to separately provide a sensor for detecting the cam position. However, the present invention is not limited to the specification of the cam position based on the motor output torque. For example, as shown in FIG. 12B, when the cam 21A is rotated while holding the motor output torque constant, the rotational speed of the motor 12 varies according to the cam friction torque. Therefore, the motor speed or acceleration may be acquired using a signal from the rotational position sensor of the motor 12, and the cam position may be specified from the change in the speed or acceleration. In any case, the cam position can be specified by monitoring various physical quantities having a correlation with the cam friction torque change.

  The above-described cam position initialization routine can be performed when the internal combustion engine 1 is started or stopped. Specifically, when the ignition switch is turned on, the cam position initialization routine is executed prior to the cranking operation, or the motor control is performed when the ignition switch is turned off and it is confirmed that the internal combustion engine 1 is stopped. Prior to shutting off the power supply to the device 40, a cam position initialization routine is executed. When initialization is performed when the ignition switch is turned on, the obtained cam position information may be stored in various storage devices as long as the motor control device 40 can refer to the information. On the other hand, when initialization is performed when the ignition switch is turned off, the information on the obtained cam position is backed up by a vehicle battery, or a rewritable flash that does not require the supply of power for memory retention. Store in a non-volatile memory such as ROM. By using such a storage device, initialization is not required when the internal combustion engine 1 is started, and control of the cam 21A can be started immediately using the stored cam position.

  Further, the execution timing of the cam position initialization routine is not limited to immediately after the ignition switch is turned on or off, and may be appropriately performed as necessary as long as it does not affect the operation of the internal combustion engine 1. For example, the cam position initialization routine may be executed while the idling stop is being executed, or during the so-called reduced cylinder operation in which the combustion is stopped in some cylinders for deceleration or the like, the idle cylinder (combustion is stopped). The cam initialization routine may be executed for the cam 21A corresponding to the cylinder).

(About power generation using cam rotation)
In FIG. 8 described above, the cam friction torque TF (θ) is always greater than 0, and the drive current is supplied to the motor 12 through one rotation of the cam 21A. However, depending on the magnitude relationship between the magnitude of the force with which the valve spring 23 pushes the cam 21A and the base friction torque Tf, the cam friction torque TF becomes negative as shown in FIG. The output shaft may be driven to rotate. When such a state occurs, as shown in FIG. 14, the motor (also called a motor generator) 12 generates electric power, and the battery 51 is charged with the obtained electric power via the inverter circuit 50. Thus, an appropriate load may be applied to the rotation of the cam 21A.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the cam friction torque is predicted and the output torque of the motor 12 is controlled. However, in this embodiment, the change in the rotational speed (rotational speed) of the internal combustion engine 1 based on the operating state of the internal combustion engine 1. And the output torque of the motor 12 is controlled according to the prediction result. The mechanical configuration of the valve drive devices 11A and 11B is the same as that in the first embodiment.

  FIG. 15 is a block diagram of a control system implemented in the motor control device 40 according to the second embodiment of the present invention. This configuration may be realized by a combination of a CPU and software, or may be realized by a hardware circuit. In this embodiment, the requested cam angle as the control target value is calculated based on the crank angle detected by the crank angle sensor 45 and the valve timing (requested valve timing) required according to the operating state of the internal combustion engine 1. The A deviation between the requested cam angle and an actual cam angle (actual cam angle) given as input information is acquired, and the output torque of the motor 12 is PID-controlled based on the deviation.

  Further, in the control system of FIG. 15, several parameters related to the change in the rotation speed of the internal combustion engine 1 (for example, the accelerator opening, the intake air amount, the fuel injection amount) are monitored. Then, the correction amount of the output torque corresponding to these parameters is obtained using a predetermined map. If the vehicle is equipped with an automatic transmission, the shift position may be monitored as a parameter. The shift position can be obtained by referring to the shift diagram of the transmission. The correspondence relationship between each parameter and the correction amount may be obtained by a bench fit test or computer simulation.

  Then, a value obtained by adding the correction amount of the output torque obtained based on the map to the output torque obtained by the PID control is output as the required torque. The motor control device 40 controls the drive current of the motor 12 based on the required torque.

  In the above embodiment, the change in the rotational speed of the internal combustion engine 1 is predicted indirectly through the accelerator opening, etc., and the correction amount of the motor output torque is given from the map according to the predicted result. As a result, the output torque of the motor 12 is feedforward controlled. Therefore, the responsiveness of the cam drive speed to the change in the rotational speed of the internal combustion engine 1 can be improved.

  FIG. 16 shows an example of feedforward control of the cam output torque when a change in the rotational speed is predicted based on the accelerator opening. In the figure, the feed forward torque means the correction amount of the output torque specified from the map in the control system of FIG. 15, and is not the required torque itself. In the example of FIG. 16, the feedforward torque is increased by a predetermined amount for a certain period A in response to the rapid increase in the accelerator opening. The rotational speed of the internal combustion engine 1 increases as the accelerator opening increases, but if no feedforward torque is applied, the actual cam angle as shown by the two-dot chain line in FIG. Is accompanied by a delay. For example, if the output torque of the motor 12 is only feedback controlled based on the rotational speed of the internal combustion engine 1, such cam angle deviation may occur. However, when feed-forward torque is applied, the cam response can be improved by making the required cam angle substantially coincide with the actual cam angle.

  FIG. 17 shows an example of cam output torque feedforward control when a change in the rotational speed is predicted based on the shift position. In this example, when a downshift request is given based on the shift diagram of the transmission, the feedforward torque is increased by a predetermined amount for a certain period B corresponding to the request. Although the rotational speed of the internal combustion engine 1 is increased by executing the downshift, if no feedforward torque is applied, the actual cam angle is changed to the actual cam angle as shown by a two-dot chain line in the figure with respect to the required cam angle shown in the figure. Response delay occurs. However, when feed-forward torque is applied, the cam response can be improved by making the requested cam angle substantially coincide with the actual cam angle even during downshifting.

  In addition to the above, the change in the rotation speed may be predicted with reference to various parameters correlated with the change in the rotation speed of the internal combustion engine 1. Note that the feedforward control of the motor output torque based on the prediction of the rotational speed change may be executed in parallel with other control related to the motor output torque, or may be executed independently. For example, at least one of the cam angle feedback control based on the crank angle detected by the crank angle sensor 45 and the feed forward control based on the prediction of the cam friction torque in the first embodiment and the feed in the second embodiment. You may implement forward control in parallel.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the present embodiment, the drive mode of the motor 12 of each valve drive device 11A, 11B is switched between the normal rotation mode and the normal rotation mode in accordance with the operating state of the internal combustion engine 1. The forward rotation mode is a mode in which the motor 12 is continuously rotated in a predetermined direction (forward rotation direction), and the forward / reverse rotation mode is a mode in which the rotation direction of the motor 12 is appropriately switched between the forward rotation direction and the reverse rotation direction. is there. The mechanical configuration of the valve driving devices 11A and 11B is the same as that of the first embodiment.

  FIG. 18 shows an example of the switching condition regarding the drive mode of the motor 12. In this example, the motor drive mode is switched based on the rotational speed and load of the internal combustion engine 1, and the forward rotation mode is applied at high rotation and high load, and the forward rotation mode is applied at low rotation and low load. In the forward / reverse rotation mode, the cams 21A and 21B are switched to the maximum lift position, that is, the maximum lift to the intake valve 4 or the exhaust valve 5 by switching the rotation direction of the motor 12 at an arbitrary position while the intake valve 4 or the exhaust valve 5 is opened. The intake valve 4 or the exhaust valve 5 can be closed before reaching the position where the quantity is given.

  That is, as shown in FIG. 19, when the maximum lift amount when the motor 12 is rotated in the forward rotation mode is La, the motor 12 is temporarily turned on before the cams 21A and 21B reach the maximum lift position θmax in the forward / reverse rotation mode. When stopped and then reversed, the maximum lift amount of the intake valve 4 and the exhaust valve 5 can be limited to a smaller Lb. Thereby, an excessive increase in the amount of intake air can be prevented. Further, it is possible to realize a decompression function (a function of opening the intake valve 4 or the exhaust valve 5 to lower the compression pressure) with excellent responsiveness by selecting the forward / reverse rotation mode at the start. On the other hand, if the forward rotation mode is applied at the time of high load and high rotation, the cams 21A and 21B can be rotated at a high speed with a relatively small torque using the inertia of the cams 21A and 21B, the gear train 15 and the like.

  The lift amount Lb in the forward / reverse rotation mode may be changed as appropriate according to the operating state of the internal combustion engine 1. In order to make the lift amount Lb variable, the rotation angle of the cam 21A may be increased or decreased by the motor control device 40 in accordance with the lift amount Lb.

  FIG. 20 shows a drive mode determination routine that the motor control device 40 repeatedly executes at an appropriate cycle during operation of the internal combustion engine 1 in order to switch the drive mode of the motor 12. When the motor control device 40 executes this drive mode determination routine, the motor control device 40 functions as a lift amount control unit and a mode switching unit.

  In the drive mode determination routine of FIG. 20, the motor control device 40 acquires the rotational speed and load of the internal combustion engine 1 in step S31, and in the subsequent step S32, the current operation state of the internal combustion engine 1 is correct according to the conditions shown in FIG. It is determined whether or not it is in an area for selecting a rotation mode. Then, the forward rotation mode or the forward / reverse rotation mode is selected according to the determination result (step S33 or S34), and then the drive mode determination routine is finished.

  In determining the drive mode, not only the engine speed and the engine load but also various parameters correlated with the operating state of the internal combustion engine 1 may be referred to. Further, the switching condition between the forward rotation mode and the forward rotation mode is not limited to the example of FIG. 18 and may be changed as appropriate. The feedforward control of the first and second embodiments described above can be used to control the output torque of the motor 12 in the forward rotation mode.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the present embodiment, the motor control device 40 is caused to function as a valve rotation execution means by causing the motor control device 40 to execute the cleaning control routine of FIG. 21 at a predetermined time when the internal combustion engine 1 is stopped. The mechanical configuration of the valve drive devices 11A and 11B is the same as that in the first embodiment.

  In the cleaning control routine of FIG. 21, the motor control device 40 starts high-speed rotation of the motor 12 in step S41, and determines whether or not a predetermined time has elapsed from the start of rotation of the motor 12 in step S42. Then, when the predetermined time has elapsed, the process proceeds to step S43, and the motor 12 is stopped.

  As described above, when the motor 12 is rotated at a high speed while the internal combustion engine 1 is stopped, the intake valve 4 is opened and closed at a high speed as shown in FIG. 22, and the surging phenomenon of the valve spring 23 causes the valve spring 23 to move relative to the intake valve 4. The load is reduced and the intake valve 4 rotates about the axis of the stem 4a. Thereby, carbon adhering between the intake valve 4 and the valve seat 60 is removed. Further, as the intake valve 4 rotates, the contact portion of the stem upper end portion 4b with the rocker arm 16 is displaced in the circumferential direction, so that the stem upper end portion 4b is substantially in the circumferential direction as shown by a hatched region in FIG. Uniform wear. Incidentally, if the stem 4a does not rotate, only a specific portion of the stem upper end 4b contacts the rocker arm 16, and the stem upper end 4b is unevenly worn as shown by the hatched area in FIG. Although the case of the intake valve 4 has been described above as an example, the cleaning control routine of FIG. 21 is similarly executed for the exhaust valve 5.

  The execution timing of the cleaning control routine of FIG. 21 is suitable when a long-term stop of the internal combustion engine 1 can be expected, for example, by removing the ignition key. However, it is not necessary to execute the cleaning control routine of FIG. 21 every time the internal combustion engine 1 is stopped, the carbon adhesion state to the intake valve 4 and the exhaust valve 5, and the progress of wear of the stems of the intake valve 4 and the exhaust valve 5 Depending on the situation, the execution time may be determined appropriately.

The perspective view which shows the principal part of the valve drive system which concerns on the 1st Embodiment of this invention. The perspective view which shows the structure of the valve drive device provided corresponding to one cylinder. The perspective view from another direction of a valve drive device. The perspective view from another direction of a valve drive device. The perspective view of a valve characteristic adjustment mechanism. The perspective view which cuts and shows a valve characteristic adjustment mechanism partially. The flowchart which shows the procedure of the motor drive control routine which the control apparatus of FIG. 2 performs. The figure which shows an example of the relationship between a crank angle, a valve lift, a cam friction torque, and a motor drive current. The figure which shows an example of the correspondence of the maximum lift amount of a valve | bulb, a crank angle, and a cam friction torque. The figure which shows an example of the correspondence of a cam angle and a motor angle. The flowchart which shows the procedure of the cam position initialization routine which the control apparatus of FIG. 2 performs. The figure which shows an example of the correlation of a motor speed, a cam friction torque, and a motor output torque. The figure which shows the example from which cam friction torque becomes negative. The figure which shows the structure for performing regenerative electric power generation with the motor for a cam drive. The block diagram of the control system for predicting the change of the rotation speed of an internal combustion engine and controlling the output torque of a motor in the 2nd Embodiment of this invention. The figure which shows an example of the control implement | achieved by the control system of FIG. The figure which shows the other example of the control implement | achieved by the control system of FIG. The figure which shows the conditions for switching the drive mode of a motor between the normal rotation mode and the normal rotation mode in the 3rd Embodiment of this invention. . The figure which shows the correspondence of the crank angle in each of normal rotation mode and normal rotation mode, and a valve lift and motor rotation speed. The figure which shows the drive mode discrimination | determination routine which a control apparatus performs for the setting of a drive mode. The flowchart which shows the procedure of the cleaning control routine which a control apparatus performs in order to implement the cleaning of an intake valve or an exhaust valve. The figure which shows a mode that it operates by operating an intake valve at high speed. The figure which compares and shows the abrasion condition of the stem upper-end part when cleaning control is performed (a) and when it is not performed (b).

Explanation of symbols

1 Internal combustion engine 2 Cylinder
DESCRIPTION OF SYMBOLS 4 Intake valve 5 Exhaust valve 10 Valve drive system 11A, 11B Valve drive device 12 Electric motor 13 Power transmission mechanism 15 Gear train 21A, 21B Cam 23 Valve spring 40 Motor control device (Motor control means, abnormality determination means, cam position specification means , Initialization means, valve rotation execution means, lift amount control means, mode switching means)

Claims (17)

A valve drive system for an internal combustion engine, applied to an internal combustion engine having a plurality of cylinders, for driving an intake or exhaust valve provided in each cylinder,
An electric motor provided as a drive source for generating a rotational motion provided to drive the valves of different cylinders of the internal combustion engine, and the rotational motion of the electric motor converted into an opening / closing motion of a valve to be driven and transmitted A plurality of valve drive devices each having a power transmission mechanism to perform,
Motor control means for controlling the operation of the electric motor of each of the plurality of valve drive devices in accordance with the operating state of the internal combustion engine;
A valve drive system for an internal combustion engine, comprising:   The motor control means controls the operation of the electric motor in accordance with the operating state of the internal combustion engine so that at least one of the operating characteristic of the valve to be driven, the lift characteristic, or the maximum lift amount changes. The valve drive system according to claim 1, wherein the valve drive system is controlled.   The valve drive system according to claim 1 or 2, wherein the power transmission mechanism uses a cam to convert the rotational motion of the electric motor into the opening / closing motion.   The valve drive system according to claim 3, wherein the motor control unit sets a control amount of the electric motor in consideration of a change in friction torque acting on rotation of the cam.   5. The valve drive system according to claim 3, wherein the motor control unit sets a control amount of the electric motor in consideration of a control state relating to an intake or exhaust characteristic of the internal combustion engine.   The motor control means corrects the control amount of the motor so that the air-fuel ratio is controlled to a predetermined target value in consideration of a control state related to the air-fuel ratio as the characteristic of the internal combustion engine. The valve drive system according to claim 5.   An abnormality determining means is provided for determining whether or not there is an abnormality in the valve drive system based on a correction amount for the control amount of the electric motor given by taking into account a control state relating to the intake or exhaust characteristics of the internal combustion engine. The valve drive system according to claim 5 or 6.   The motor control means predicts a change in the rotational speed of the internal combustion engine based on a change in the operating state of the internal combustion engine, and sets the control amount of the electric motor in consideration of the prediction result. The valve drive system according to claim 3.   4. When the friction torque acting on the rotation of the cam takes a negative value, the electric motor is driven by the rotational movement on the cam side, and electric power is generated by the electric motor. 9. The valve drive system according to any one of items 8.   Motor rotation position detection means for detecting the rotation position of the electric motor is attached to the electric motor, and the motor control means is a cam position for specifying the rotation position of the cam based on the detection result of the rotation position of the electric motor. The valve drive system according to any one of claims 3 to 9, further comprising a specifying unit.   N is set to 6 or less when the reduction ratio between the electric motor and the cam is N: M (where N> M, and N and M are integers having no common divisor other than 1). The valve drive system according to claim 10.   The motor control means rotates the electric motor according to a predetermined condition when the internal combustion engine is in a predetermined state, and drives the electric motor that appears in correlation with a change in the friction torque of the cam during the rotation. The valve drive system according to any one of claims 3 to 11, further comprising an initialization unit that grasps the rotational position of the cam based on a change in state.   The initialization means rotates the electric motor when the internal combustion engine is stopped to grasp the rotational position of the cam, and stores and holds information indicating the grasped rotational position of the cam even during the stop period of the internal combustion engine. The motor control means specifies the rotational position of the cam based on the information stored in the storage device and starts control of the electric motor at the next start of the internal combustion engine. The valve drive system according to claim 12, wherein:   The said motor control means is provided with the valve rotation execution means which drives the said electric motor so that the said valve may rotate to the surroundings of the axis line in the predetermined time when the said internal combustion engine stops. The described valve drive system.   The motor control means is a lift amount control for driving the electric motor forward and reverse so that a lift amount of the valve is limited to a predetermined value smaller than a maximum lift amount obtained when the cam is rotated once. 4. A valve drive system according to claim 3, comprising means.   The motor control means includes a drive mode of the electric motor according to an operating state of the internal combustion engine, a forward rotation mode for driving the electric motor only in a forward rotation direction, and a forward / reverse rotation mode for rotating the electric motor forward and backward. The valve drive system according to claim 3, further comprising mode switching means for switching between the two. An electric motor as a drive source that generates rotational motion;
A power transmission mechanism that converts the rotational motion of the electric motor into the opening / closing motion of a valve to be driven and transmits the same;
Motor control means for controlling the operation of the electric motor such that at least one of the operating angle of the valve to be driven, the lift characteristic, or the maximum lift amount changes according to the operating state of the internal combustion engine; ,
A valve drive apparatus for an internal combustion engine, comprising:

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