JP2007239694A - Actuator and variable valve structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator wherein the rotating motion of an output shaft is restricted when an external load is operated on the output shaft at stopping operation, and to provide a variable valve structure for an internal combustion engine. <P>SOLUTION: The actuator comprises an outer rotor 31 to be rotated with a motor, an inner shaft 21 inserted into the outer rotor 31 for outputting rotating motion thereto, a clutch cam 27, a spring 36, and a brake mechanism 25. The clutch cam 27 moves the inner shaft 21 from a first position to a second position in the axial direction when relative rotating motion occurs between the outer rotor 31 and the inner shaft 21. The spring 36 energizes the inner shaft 21 toward the first position. The brake mechanism 25 restricts the rotation of the inner shaft 21 when the inner shaft 21 is at the first position, and permits the rotation of the inner shaft 21 when it is at the second position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to an actuator and a variable valve mechanism for an internal combustion engine. More specifically, the present invention has an output shaft that outputs a rotary motion, and when the operation is stopped, the output shaft is rotated from the outside to the output shaft. The present invention relates to an actuator in which a load is assumed to be reversely input and a variable valve mechanism for an internal combustion engine.

  With respect to conventional actuators, for example, Japanese Patent Application Laid-Open No. 2005-9487 aims to effectively suppress illegal movement of a valve when the engine speed may increase beyond the allowable speed. An engine valve device is disclosed (Patent Document 1). In the engine valve operating device disclosed in Patent Document 1, the intake valve and the exhaust valve are driven by the intake camshaft and the exhaust camshaft, respectively, via the valve lift / valve timing variable mechanism. The variable valve lift / valve timing mechanism is connected to an actuator motor that outputs rotational motion.

Japanese Patent Laid-Open No. 2003-113905 discloses a geared motor that is small and inexpensive and has a braking force (Patent Document 2). The take-up drum around which the fishing line is wound is fixed to the geared motor disclosed in Patent Document 2. A load is always applied to the winding drum in one direction. The geared motor incorporates a one-way clutch to restrict the rotation of the take-up drum and keep the fishing line stopped.
Japanese Patent Laid-Open No. 2005-9487 JP 2003-113905 A

  In the variable valve mechanism mounted on the engine, it is desirable to set the valve characteristic suitable for starting when the engine is stopped and to start the engine while maintaining the state. On the other hand, in the engine valve operating device disclosed in Patent Document 1 described above, the elastic force of the valve spring that urges the intake valve and the exhaust valve in the valve closing direction acts on the valve lift / valve timing variable mechanism. Therefore, the set valve operating characteristics cannot be maintained after the engine is stopped. In this case, it is necessary to drive the valve lift / valve timing variable mechanism against the elastic force of the valve spring at the next engine start, and a large output torque is required for the motor. Further, if it is attempted to maintain the valve operating characteristics after the engine is stopped, it is necessary to supply a holding current to the motor.

  On the other hand, the geared motor disclosed in Patent Document 2 described above incorporates a one-way clutch in order to regulate the rotation of the output shaft when a load is applied to the output shaft of the actuator from the outside. However, the one-way clutch is provided assuming a load applied only in one direction, and the rotation of the output shaft cannot be restricted with respect to a load applied in the opposite direction. The load acting on the variable valve mechanism by the elastic force of the valve spring is assumed to be both forward rotation and reverse rotation. For this reason, the one-way clutch cannot maintain the valve operating characteristics after the engine is stopped.

  Accordingly, an object of the present invention is to solve the above-described problem, and an actuator that restricts the rotational movement of the output shaft when an external load is applied to the output shaft when the operation is stopped, and an internal combustion engine including the actuator. A variable valve mechanism is provided.

  An actuator according to the present invention is formed in a hollow shape and is rotated by a motor, an inner rotor that is inserted into the outer rotor and outputs a rotational motion, and a motion conversion mechanism provided in the outer rotor and the inner shaft. And an elastic member and a brake mechanism provided on the inner shaft. The inner shaft is provided so as to be rotatable relative to the outer rotor and to be movable in the axial direction. The motion conversion mechanism moves the inner shaft in the axial direction from the first position to the second position when a relative rotational motion is generated between the outer rotor and the inner shaft due to the rotation of the outer rotor. The elastic member applies an axial elastic force to the inner shaft and biases the inner shaft toward the first position. The brake mechanism restricts the rotation of the inner shaft when the inner shaft is in the first position, and allows the rotation of the inner shaft when the inner shaft is in the second position.

  According to the actuator configured as described above, when the outer rotor is rotated by the motor, the restriction of the rotation of the inner shaft by the brake mechanism is released. The inner shaft rotates together with the outer shaft, and rotational motion is output from the inner shaft. On the other hand, when the motor is not energized and the outer rotor is stopped, the rotation of the inner shaft can be regulated by the brake mechanism even if a load may be applied to the inner shaft from the outside.

  Preferably, the actuator further includes a speed reduction mechanism connected to the inner shaft. According to the actuator configured in this manner, when the outer rotor is stopped, the rotation of the inner shaft can be reliably restricted with respect to a larger load acting on the inner shaft from the outside.

  Preferably, the brake mechanism includes a brake disc and a brake pad. The brake disc is provided integrally with the inner shaft, and is disposed on the opposite side of the elastic member in the axial direction of the inner shaft. The brake pad is provided facing the brake disc. When the inner shaft is in the first position, the brake disk and the brake pad are pressed against each other by the elastic force of the elastic member. When the inner shaft is in the second position, the brake disc and the brake pad are separated. According to the actuator configured in this way, it is possible to switch between regulation and allowance of rotation of the inner shaft by the brake mechanism in conjunction with the movement of the inner shaft in the axial direction.

  Further preferably, the motion conversion mechanism is a cam mechanism including a first cam surface and a second cam surface. The first cam surface is formed on the inner shaft and extends around the axis while being displaced in the axial direction of the inner shaft. The second cam surface is formed on the outer rotor. The second cam surface is in contact with the first cam surface, and slides with the first cam surface when a relative rotational movement occurs between the outer rotor and the inner shaft. According to the actuator configured in this manner, the inner shaft can be moved in the axial direction with a simple and reliable configuration.

  Preferably, a friction reducing member for reducing sliding resistance between the first cam surface and the second cam surface is provided. According to the actuator configured in this way, the sliding resistance between the first cam surface and the second cam surface, which is an obstacle when the inner shaft is moved in the axial direction, is reduced, so that the actuator can be smoothly operated. Can achieve a healthy exercise.

  A variable valve mechanism for an internal combustion engine according to the present invention includes any one of the actuators described above. According to the variable valve mechanism of the internal combustion engine configured as described above, even when the holding current is not supplied to the motor, the rotation of the inner shaft is restricted and the operation of the variable valve mechanism is stopped. be able to. For this reason, if the variable valve mechanism is set to the optimum valve characteristic at the time of starting immediately before the internal combustion engine is stopped, the valve characteristic can be maintained until the internal combustion engine is started again.

  As described above, according to the present invention, when a load is applied to the output shaft from the outside when operation is stopped, the actuator that restricts the rotational movement of the output shaft and the variable valve mechanism of the internal combustion engine including the actuator are provided. Can be provided.

  Embodiments of the present invention will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a state when the actuator is stopped according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing the internal structure of the actuator in FIG. The actuator shown in the figure is used for a variable valve mechanism of an internal combustion engine mounted on a vehicle. The variable valve mechanism may be a variable valve lift amount mechanism that makes the lift amount of the valve variable, or may be a variable valve timing mechanism that makes the timing for opening and closing the valve variable.

  1 and 2, the actuator 10 includes an outer rotor 31 and an inner shaft 21, a motor 40 that applies a rotational force to the outer rotor 31, a spring 36 that applies an elastic force to the inner shaft 21, and an inner A brake mechanism 25 that restricts the rotational movement of the shaft 21 and a clutch cam 27 provided on the outer rotor 31 and the inner shaft 21 are provided. The actuator 10 includes a self-locking mechanism that automatically restricts the rotational movement of the inner shaft 21 that is the output shaft when the supply of current to the motor 40 is stopped.

  The outer rotor 31 has a cylindrical shape extending along the central axis 101. A hollow portion 32 is formed in the outer rotor 31. A motor magnet 42 is fixed to the outer peripheral surface of the outer rotor 31. A motor coil 41 is disposed on the outer periphery of the motor magnet 42. The motor 40 is constituted by the motor magnet 42 and the motor coil 41. The motor 40 is, for example, a brushless motor.

  The motor coil 41 is fixed to an outer case 47 as a case body. The outer case 47 accommodates each component included in the actuator 10. Bearings 45 are disposed on both sides of the motor magnet 42. The outer rotor 31 is supported by the bearing 45 so as to be rotatable with respect to the outer case 47. By energizing the motor coil 41, the outer rotor 31 rotates around the central axis 101.

  FIG. 3 is a diagram showing the shape of the cam surface formed on the outer rotor in FIG. In the figure, the shape of the outer rotor viewed from three directions is shown.

  With reference to FIGS. 1 to 3, the outer rotor 31 has a cam surface 33 as a second cam surface. The cam surface 33 faces the axial direction of the central shaft 101. The cam surface 33 is formed so as to go around the central axis 101 while being displaced in the axial direction of the central axis 101. The cam surface 33 is formed so as to go around the central axis 101 while changing the angle of the central axis 101 with respect to the axial direction. The cam surface 33 is formed by a curved surface that continuously extends around the central axis 101.

  The cam surface 33 includes a peak portion 33p protruding in the axial direction of the central shaft 101 and a concave valley portion 33q. The peaks 33 p and valleys 33 q are alternately arranged around the axis of the central axis 101. Two peaks 33p and valleys 33q are provided every 90 ° around the axis of the central axis 101. The cam surface 33 may be formed so that the number of the peak portions 33p and the valley portions 33q is other than two.

  The inner shaft 21 is inserted into the hollow portion 32. The inner shaft 21 outputs a rotational motion by rotating together with the outer rotor 31. The inner shaft 21 extends along the central axis 101. One end and the other end of the inner shaft 21 along the axial direction of the central shaft 101 extend outside the hollow portion 32. A brake disc portion 24 is integrally provided at one end of the inner shaft 21. The other end of the inner shaft 21 is connected to a mechanism that transmits the rotational motion output from the inner shaft 21 to the internal combustion engine and changes the valve operating characteristics of the internal combustion engine. In the present embodiment, a spline 29 in which teeth are arranged around the central axis 101 is formed at the other end of the inner shaft 21.

  The inner shaft 21 has a cam surface 23 as a first cam surface. The cam surface 23 has the same shape as the cam surface 33. The cam surface 23 faces the side opposite to the cam surface 33. The cam surface 23 has a shape in surface contact with the cam surface 33. The cam surface 23 and the cam surface 33 constitute a clutch cam 27.

  The inner shaft 21 is provided so as to be rotatable relative to the outer rotor 31 around the central axis 101. Further, the inner shaft 21 is provided so as to be movable along the axial direction of the central axis 101.

  The spring 36 is arranged side by side in the axial direction of the brake disc portion 24 and the central shaft 101. The spring 36 is formed from a coil spring. The spring 36 is provided in a compressed and deformed state in the outer case 47, and applies an elastic force along the axial direction of the central shaft 101 to the brake disk portion 24. The outer case 47 is provided with a thrust bearing 38. The thrust bearing 38 supports the spring 36 so as to be rotatable about the central axis 101. With such a configuration, the spring 36 rotates with the inner shaft 21 around the central axis 101.

  A brake pad 34 is provided on the opposite side of the spring 36 with respect to the brake disk portion 24. The brake pad 34 is fixed to the outer case 47. The brake disc portion 24 and the brake pad 34 are provided to face each other along the axial direction of the central shaft 101. The spring 36 biases the brake disc portion 24 toward the brake pad 34. The brake disc 25 and the brake pad 34 constitute a brake mechanism 25.

  One end side of the inner shaft 21 is called a rear side, and the other end side is called a front side. When energization of the motor coil 41 is stopped, the inner shaft 21 moves to the front side while the cam surface 23 follows the cam surface 33 due to the elastic force of the spring 36. The inner shaft 21 moves to a position where the concave and convex portions of the cam surfaces 23 and 33 match each other and the cam surface 23 and the cam surface 33 are in surface contact. At this time, the brake disc portion 24 and the brake pad 34 are pressed against each other by the elastic force of the spring 36. A frictional force is generated between the brake pad 34 and the brake disc portion 24, and the rotational motion of the inner shaft 21 provided integrally with the brake disc portion 24 is restricted.

  FIG. 4 is a cross-sectional view showing a state when the actuator in FIG. 1 is operated. FIG. 5 is a perspective view showing the position of the cam surface of the actuator in FIG. Referring to FIGS. 4 and 5, when energization to motor coil 41 is started, outer rotor 31 starts to rotate around central axis 101 and is relatively rotated between outer rotor 31 and inner shaft 21. Movement occurs.

  Along with this relative rotational movement, the cam surface 33 pushes the inner shaft 21 to the rear side while sliding with the cam surface 23. The brake disk portion 24 moves in the axial direction of the central shaft 101 against the elastic force of the spring 36 and is separated from the brake pad 34. Thereby, the lock | rock of the rotational motion of the inner shaft 21 by the brake mechanism 25 is cancelled | released. When the inner shaft 21 advances to a predetermined position, the cam surface 33 and the cam surface 23 are caught, and the inner shaft 21 starts to rotate together with the outer rotor 31. In the present embodiment, when the motor coil 41 is energized, the brake mechanism 25 can release the lock regardless of which direction the inner shaft 21 rotates.

  In order to move the inner shaft 21 to the front side by following the cam surface 23 and the cam surface 33 when the energization to the motor coil 41 is stopped, the force for pushing the inner shaft 21 by the elastic force of the spring 36 is used. However, it needs to be larger than the loss torque of the motor 40. On the other hand, when energization of the motor coil 41 is started, the torque generated by the motor 40 needs to be larger than the torque for releasing the lock by the brake mechanism 25.

  The actuator 10 according to the first embodiment of the present invention is formed in a hollow shape and is rotated by a motor 40. The inner rotor 21 is inserted into the outer rotor 31 and outputs rotational motion. The outer rotor 31 and the inner rotor 21 are rotated. A clutch cam 27 as a motion conversion mechanism provided on the shaft 21, a spring 36 as an elastic member, and a brake mechanism 25 provided on the inner shaft 21 are provided.

  The inner shaft 21 is provided so as to be rotatable relative to the outer rotor 31 and movable in the axial direction. The clutch cam 27 moves the inner shaft 21 to the first position (the position shown in FIGS. 1 and 2) when the outer rotor 31 rotates to cause a relative rotational movement between the outer rotor 31 and the inner shaft 21. To the second position (position shown in FIGS. 4 and 5) in the axial direction. The spring 36 applies an elastic force in the axial direction to the inner shaft 21 and biases the inner shaft 21 toward the first position. The brake mechanism 25 restricts the rotation of the inner shaft 21 when the inner shaft 21 is in the first position, and allows the rotation of the inner shaft 21 when the inner shaft 21 is in the second position.

  According to the actuator 10 configured as described above in Embodiment 1 of the present invention, after the operation of the internal combustion engine is stopped, the inner shaft 21 is rotated around the central axis 101 by the elastic force of the valve spring disposed in the internal combustion engine. The rotational force of On the other hand, in the present embodiment, the rotational movement of the inner shaft 21 is restricted by the brake mechanism 25 regardless of whether forward or reverse rotational force acts on the inner shaft 21 around the central axis 101. Can do. For this reason, if the inner shaft 21 is positioned so that the valve operating characteristic suitable for starting the internal combustion engine can be obtained immediately before the operation of the internal combustion engine is stopped, the holding current is not supplied to the motor 40. When the internal combustion engine is started again, an appropriate valve operating characteristic can be obtained.

  FIG. 6 is a perspective view showing a modification of the actuator in FIG. Referring to FIG. 6, in this modification, a recess 62 that opens to the cam surface 23 is formed in the inner shaft 21. A bearing 61 is accommodated in the recess 62. The bearing 61 has an inner ring 64 fixed to the inner shaft 21 and a rotatable outer ring 63. The outer ring 63 includes an outer peripheral surface 63 a that faces the cam surface 33 and continues to the cam surface 23.

  With such a configuration, when a relative rotational motion is generated between the inner shaft 21 and the outer rotor 31, the outer peripheral surface 63a and the cam surface 33 come into contact with each other. Thereby, the friction between the cam surface 23 and the cam surface 33 can be reduced, and the loss torque generated by the clutch cam 27 can be kept small.

  FIG. 7 is a diagram schematically showing a connection form between the actuator and the internal combustion engine in FIG. Referring to FIG. 7, actuator 10 further includes a harmonic drive gear 51 disposed between inner shaft 21 and internal combustion engine 53. The harmonic drive gear 51 is connected to a spline 29 formed at one end of the inner shaft 21. The harmonic drive gear 51 decelerates the rotational motion output from the inner shaft 21 and transmits it to the internal combustion engine 53.

  With such a configuration, even when the reverse input acting on the inner shaft 21 from the internal combustion engine 53 side after the operation of the internal combustion engine is large, the rotational motion of the inner shaft 21 can be more reliably regulated.

  In the present embodiment, the case where the present invention is applied to a variable valve mechanism of an internal combustion engine has been described. However, the present invention is not limited to this. For example, the present invention is applied to a steering operation force assist mechanism mounted on a vehicle. Also good. The present invention can be applied to a general actuator driven by a motor.

(Embodiment 2)
FIG. 8 is a perspective view showing a state when the actuator is stopped in the second embodiment of the present invention. In the drawing, the outer rotor is shown in a transparent manner in order to facilitate understanding of the internal structure of the actuator. FIG. 9 is a cross-sectional view of the actuator along the line IX-IX in FIG. The actuator in the present embodiment has basically the same structure as that of the actuator 10 in the first embodiment. Hereinafter, the description of the overlapping structure will not be repeated.

  Referring to FIGS. 8 and 9, in the present embodiment, instead of clutch cam 27 in FIG. 1, ball 67 guided in guide groove 66 formed in inner shaft 21 is provided as a motion conversion mechanism. ing.

  The outer rotor 31 and the inner shaft 21 have an inner peripheral surface 31b and an outer peripheral surface 21a that face each other. The guide groove 66 is formed in the outer peripheral surface 21a. The guide groove 66 is formed to extend in a U shape along the surface of the outer peripheral surface 21a. The guide groove 66 has a bottom portion 66m that becomes the bottom of the U-shape on the rear side, and end portions 66n that become both ends of the U-shape on the front side. The guide groove 66 is formed on the outer peripheral surface 21 a so as to circulate around the axis while being displaced in the axial direction of the inner shaft 21.

  The outer rotor 31 is formed with a recess 68 that is recessed from the inner peripheral surface 31b. The ball 67 is accommodated in the recess 68. The ball 67 is rotatably accommodated in the recess 68. The ball 67 is disposed so as to be sandwiched between the wall surface of the recess 68 and the wall surface of the guide groove 66. With such a configuration, when a relative rotational movement occurs between the inner shaft 21 and the outer rotor 31, the ball 67 moves along the guide groove 66 while being held in the recess 68.

  When the motor coil 41 is energized, the ball 67 is positioned at the bottom 66 m of the guide groove 66. At this time, the brake disc portion 24 and the brake pad 34 are pressed against each other, and the rotational movement of the inner shaft 21 is restricted.

  FIG. 10 is a cross-sectional view showing a state when the actuator in FIG. 8 is operated. Referring to FIG. 10, when energization of motor coil 41 is started and a relative rotational movement occurs between inner shaft 21 and outer rotor 31, ball 67 is guided while being held in recess 68. It is guided by the groove 66 and moves from the bottom 66m toward the end 66n. Accordingly, the inner shaft 21 is pushed out to the rear side, and the brake disc portion 24 and the brake pad 34 are separated from each other.

  According to the actuator according to the second embodiment of the present invention configured as described above, the same effects as those described in the first embodiment can be obtained.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which shows the state at the time of the stop of the actuator in Embodiment 1 of this invention. It is sectional drawing which shows the internal structure of the actuator in FIG. It is a figure which shows the shape of the cam surface formed in the outer rotor in FIG. It is sectional drawing which shows the state at the time of the action | operation of the actuator in FIG. It is a perspective view which shows the position of the cam surface of the actuator in FIG. It is a perspective view which shows the modification of the actuator in FIG. It is the figure which represented typically the form of the connection of the actuator in FIG. 1, and an internal combustion engine. It is a perspective view which shows the state at the time of the stop of the actuator in Embodiment 2 of this invention. It is sectional drawing of the actuator along the IX-IX line in FIG. It is sectional drawing which shows the state at the time of the action | operation of the actuator in FIG.

Explanation of symbols

  10 Actuator, 21 Inner shaft, 23, 33 Cam surface, 24 Brake disc, 25 Brake mechanism, 27 Clutch cam, 31 Outer rotor, 34 Brake pad, 36 Spring, 40 Motor, 51 Harmonic drive gear, 61 Bearing, 66 Guide Groove, 67 balls.

Claims (6)

An outer rotor formed in a hollow shape and rotated by a motor;
An inner shaft that is inserted into the outer rotor, outputs a rotational motion, is rotatable relative to the outer rotor, and is movable in the axial direction;
When the outer rotor and the inner shaft are provided with a relative rotational movement between the outer rotor and the inner shaft, the inner shaft is moved from the first position to the second position. A motion conversion mechanism that moves axially to a position;
An elastic member that applies an elastic force in the axial direction to the inner shaft and biases the inner shaft toward the first position;
A brake mechanism provided on the inner shaft that restricts rotation of the inner shaft when the inner shaft is in the first position and allows rotation of the inner shaft when the inner shaft is in the second position. And an actuator.   The actuator according to claim 1, further comprising a speed reduction mechanism connected to the inner shaft. The brake mechanism is provided integrally with the inner shaft, and includes a brake disc disposed on the opposite side of the elastic member in the axial direction of the inner shaft, and a brake pad provided to face the brake disc. Including
When the inner shaft is in the first position, the brake disk and the brake pad are pressed against each other by the elastic force of the elastic member, and when the inner shaft is in the second position, the brake disk and the brake The actuator according to claim 1, wherein the actuator is separated from the brake pad.   The motion conversion mechanism is formed on the inner shaft, and is formed on the outer rotor, the first cam surface extending around the axis while being displaced in the axial direction of the inner shaft, and the first cam surface And a second cam surface that slides with the first cam surface when a relative rotational movement occurs between the outer rotor and the inner shaft. The actuator according to any one of 1 to 3.   The actuator according to claim 4, wherein a friction reducing member that reduces sliding resistance between the first cam surface and the second cam surface is disposed.   A variable valve mechanism for an internal combustion engine, comprising the actuator according to any one of claims 1 to 5.

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