JP2005214088A - Ball screw actuator mechanism for variable compression ratio engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable compression ratio capable of increasing the response speed with respect to an actuator mechanism using a slide screw, reducing power consumption during driving, and compensating for the drawback of being easy to move with reaction force due to the high efficiency of a ball screw. A ball screw actuator mechanism for an engine is provided.
A ball screw actuator mechanism 1 for moving a reciprocating operation element of a variable compression ratio engine forward and backward. The mechanism 1 includes a ball screw 2, a rotation transmission system 30 that transmits the rotation of the motor 34 to the nut 5 of the ball screw 2, and a clutch 3 interposed in the rotation transmission system 30. In the ball screw 2, a nut 5 is rotatably installed with respect to the housing 7, and the screw shaft 4 can only move forward and backward. The clutch 3 is a reverse input limiting type that transmits rotation from the input member 16 to which the drive of the motor 34 is input to the nut 5, but blocks transmission of rotation from the nut 5 to the input member 16.
[Selection] Figure 1

Description

  The present invention relates to a ball screw actuator mechanism for a variable compression ratio engine that is used in a variable compression ratio engine that changes the compression ratio by changing the top dead center position of a piston.

  In automobiles, actuators using motors are being applied, and these technologies are also applied to engine control to develop high output and low fuel consumption. For example, Patent Document 1 proposes an engine that realizes high output and low fuel consumption by making the compression ratio variable and controlling the engine to the compression ratio according to the operating condition or output. In this proposed example, an actuator using a feed screw mechanism is a mechanism for controlling the actuator.

As the feed screw mechanism, a slide screw such as a square screw is used. There are two reasons why a sliding screw is used. One is that it can be manufactured at a relatively low cost, and the other is that the rotational output, which is the output of the motor, can be converted into linear motion, and the reduction ratio can be changed with an appropriate lead. It can be done.
In the wheel steering device, a combination of a ball screw and a reverse input limiting type clutch is disclosed in Patent Document 2.
JP 2002-138867 A JP 2003-81106 A

  However, when a slide screw is used as a ball screw actuator for a variable compression ratio engine, the difference between the starting torque and the rotational torque is large, and a very large motor torque is required at the time of differential. Therefore, the response speed is low. Further, there is a problem that the power consumption is large because the friction loss is large during operation and the heat generation or the load on the motor is large.

As a feed screw mechanism for solving these problems, there is a ball screw. However, since the ball screw has been conventionally used for precision positioning applications such as machine tools, it is very expensive and has not been used in automobiles. . However, in recent years, since it has been widely used for electric power steering, the development of low-cost processing and equipment has advanced, and it has entered a cost category that can be used for automobiles.
However, when using a ball screw, there is a problem to be solved with respect to the sliding screw. This is because the ball screw has high transmission efficiency, so that the nut easily turns against the axial reaction force that the actuator receives from the operating point, and the position cannot be maintained.

  An object of the present invention is to increase the response speed to an actuator mechanism using a slide screw, reduce power consumption during driving, and compensate for the disadvantage of being easy to move with reaction force due to the high efficiency of the ball screw. It is an object of the present invention to provide a ball screw actuator mechanism for a variable compression ratio engine.

The ball screw actuator mechanism for a variable compression ratio engine according to the present invention is used in a variable compression ratio engine that changes the compression ratio by changing the top dead center position of the piston according to the reciprocating position of the reciprocating element. The ball screw actuator mechanism for a variable compression ratio engine to be operated has the following configuration.
The ball screw actuator mechanism includes a ball screw in which a plurality of balls are interposed between a screw shaft and a screw groove of the nut, the nut is rotatably installed with respect to a housing, and the screw shaft is only movable forward and backward. A rotation transmission system for transmitting the rotation of the motor to the nut of the ball screw, and a clutch interposed in the rotation transmission system, the clutch rotating from the input member to which the drive of the motor is input to the nut However, a reverse input limiting type clutch that cuts off rotation transmission from the nut to the input member is used.

  According to this configuration, the rotation of the motor is transmitted to the nut of the ball screw through the clutch, converted into a linear motion of the screw shaft by the ball screw, and transmitted to the reciprocating operation element of the engine. Since the ball screw is used as a motion conversion mechanism for rotation and linear motion, the transmission efficiency is high, the response speed is increased as compared with the sliding screw mechanism, and the power consumption can be reduced. Since the ball screw has high transmission efficiency, the nut tries to rotate by the axial force applied to the screw shaft from the reciprocating operator. However, since the reverse input limit type is used for the clutch, the nut rotates from the motor side. Is prevented and the rotation of the nut is prevented. Further, since the rotation from the nut to the motor side is prevented, it is not necessary to pass a large current to the motor to hold the position with the braking force by the motor, and this also saves power. In addition, motor burnout and the like are prevented.

The reverse input limiting type clutch includes, for example, a clutch outer ring fixed to the housing, a rotatable clutch inner ring positioned on the inner periphery of the clutch outer ring, and a plurality of engagements interposed between the clutch outer ring and the clutch inner ring. It may have a combination and a retainer for holding the plurality of engagement elements, and the retainer may be an input member.
In this case, the engagement element comprises a roller, and a cam surface that forms a wedge-shaped space for engaging the engagement element between the clutch inner ring and the clutch outer ring is provided on the outer diameter surface of the clutch inner ring. It is good also as what has a connection means which connects an inner ring | wheel via a predetermined play in a rotation direction.

In the case of each configuration according to the present invention, the clutch may be a two-way clutch. This two-way clutch is a reverse input limiting type that transmits rotation from the input member to the nut in any of the forward and reverse rotation directions, but blocks transmission of rotation from the nut to the input member.
The clutch may be of a reverse input limiting type, and may be a sprag type, that is, a sprag that uses a sprag as the engagement element.

  The ball screw actuator mechanism for a variable compression ratio engine according to the present invention is used in a variable compression ratio engine that changes the compression ratio by changing the top dead center position of the piston according to the reciprocating position of the reciprocating element. A ball screw actuator mechanism to be operated, which includes a ball screw in which a nut is rotatably installed with respect to a housing and a screw shaft can only move forward and backward, and a rotation transmission system that transmits the rotation of a motor to the nut of the ball screw. A reverse input limiting clutch that transmits rotation from the input member to which the motor drive is input to the nut, but blocks transmission of rotation from the nut to the input member. As a result, the response speed of the actuator mechanism using a sliding screw is increased, and power consumption during driving is reduced. It can compensate for the disadvantage move easily by the reaction force due to the high efficiency of the ball screw.

  A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, the variable compression ratio engine ball screw actuator mechanism 1 includes a ball screw 2 having a screw shaft 4 and a nut 5, a rotation transmission system 30 for transmitting the rotation of a motor 34 to the nut 5 of the ball screw 2, and The clutch 3 interposed in the rotation transmission system 30 and the housing 7 are provided. The motor 34 is installed in the housing 7. The screw shaft 4 is connected to an advance / retreat operation element 72 in the variable compression ratio mechanism 70 of the engine or is integrated with the advance / retreat operation 72.

The ball screw 2 has a plurality of balls (not shown) interposed between the screw shaft 4 and the thread groove of the nut 5. The ball 5 is picked up and circulated through the nut 5. A circulation path (not shown) is provided. The circulation path is constituted by a piece member or a return tube.
The nut 5 of the ball screw 2 is rotatably installed with respect to the housing 7 by bearings 8 at both ends of the nut. The screw shaft 4 is engaged with the housing 7 via a rotation prevention means (not shown) such as a spline or a key, and can only advance and retreat in the axial direction but cannot rotate.

  The rotation transmission system 30 transmits the drive of the motor output gear 36 provided on the motor output shaft 34 a of the motor 34 to a nut outer peripheral gear 37 provided in a fixed state on the outer periphery of the nut 5. The clutch 3 is provided between the motor output gear 36 and the nut outer peripheral gear 37.

  The clutch 3 is a reverse input restriction type two-way clutch, and a type that transmits rotation from the input member 16 to the nut 5 but blocks transmission of rotation from the nut 5 to the input member 16 is used. The clutch 3 includes a clutch inner ring 13, a clutch outer ring 14, a plurality of engagement elements 15, and a cage 19. The clutch 3 is a roller clutch, and the plurality of engaging elements 15 are rollers. The illustrated one has one roller, but two rollers may be arranged, and a spring may be arranged between them.

The clutch outer ring 14 is fixedly installed in the housing 7 in parallel with the screw shaft 4 of the ball screw 2.
As shown in an enlarged view in FIG. 2, the clutch inner ring 13 is rotatably provided in a concentric position in the clutch outer ring 14 via a plurality of engagement elements 15 made of the roller. The clutch inner ring 13 has shaft portions 13a and 13b protruding on both sides, and is rotatably supported by the housing 7 and the cage 19 through bearings 41 and 42 provided on the outer periphery of the shaft portions 13a and 13b. Has been. A clutch output gear 38 is integrally or non-rotatably provided on the outer periphery of one shaft portion 13 a of the clutch inner ring 13, and the clutch output gear 38 meshes with a nut outer peripheral gear 37. The clutch inner ring 13 and the clutch output gear 38 constitute a clutch output member 39.

  The retainer 19 is a member that holds the plurality of engagement elements 15, and includes a bottomed cylindrical portion 19a and a shaft portion 19b that protrudes in the axial direction at the center of the outer bottom surface of the cylindrical portion 19a. The outer periphery of the cylindrical portion 19 a is rotatably supported on the inner periphery of the clutch outer ring 14 via a bearing 17. A clutch input gear 44 is provided on the shaft portion 19 b of the cage 19 in a non-rotating state, and the clutch input gear 44 is engaged with the motor output gear 36. The cage 19 and the clutch input gear 44 constitute the input member 16 of the clutch 3.

  As shown in FIG. 3, the inner surface of the clutch outer ring 14 that faces the clutch inner ring 13 is a cylindrical surface 23. The clutch inner ring 13 is formed with cam surfaces 24 at a plurality of locations in the circumferential direction on the outer diameter surface, and the engagement elements 15 are disposed between the cam surfaces 24 and the cylindrical surface 23 of the clutch outer ring 14. The cam surface 24 is a surface that forms a wedge space for engaging the engagement element 15 between the cam surface 24 and the cylindrical surface 23 of the clutch outer ring 14. The cam surface 24 is a flat surface, and forms a wedge space in both forward and reverse directions as the wedge space. The wedge spaces on both sides are, for example, symmetrical.

  The retainer 19 has pockets 25 for retaining the engagement elements 15 at a plurality of locations in the circumferential direction of the cylindrical portion 19a. The pocket 25 is formed in a circumferential width of the cage in which the engagement element 15 fits with play. In the pocket 25, elastic bodies 25 that urge the engaging element 15 toward the center of the pocket 25 are disposed on both sides of the engaging element 15. The elastic body 26 is made of, for example, a leaf spring and is attached to the cage 19. In the drawing, in order to make the configuration easy to understand, the mutual relations of the radial dimensions of the clutch inner ring 13, the cage 19 and the like are different from those in FIG.

  The cage 19 and the clutch inner ring 13 are connected by a connecting means 20 with play in the rotational direction. The connecting means 20 is formed by inserting a switching pin 21 that protrudes in the axial direction from a side surface of the cage 19 that faces the side surface of the clutch inner ring 13 into a loose fitting recess 22 provided on the side surface of the clutch inner ring 13. is there.

  The engagement element 15 is formed in a cylindrical shape of the cam surface 24 and the clutch outer ring 14 from a central position of the cam surface 24 that is a neutral position (position shown in FIG. 3) where the clutch inner ring 13 is not engaged with the clutch inner ring 13. It can move to the engagement operation position P2 (FIG. 4) which is the most approach position to the wedge space formed with the surface 23. This movement is possible in both forward and reverse directions, and the engagement element 15 is movable relative to the clutch inner ring 13 by a distance twice as long as the neutral position and the engagement operation position P2. The amount of play in the rotational direction between the cage 19 and the clutch inner ring 13, that is, the amount of play X allowed by the switching pin 21 and the loose fitting recess 22 (the amount of play on one side) is determined by the engagement element 15. Is set to be substantially the same as the amount of movement from the neutral position to the engagement operation position P2.

  The operation of the above configuration will be described. When the input member 16 comprising the clutch input gear 44 and the retainer 19 is rotated from the state shown in FIG. 3 in the clockwise direction as shown in FIG. 4A by driving the motor 34, the input member 16 is held as shown in FIG. The device 19 rotates relative to the clutch inner ring 13 by the amount of play in the rotational direction of the connecting means 20. Due to the rotation of the retainer 19, the engagement element 15 moves to the engagement operation position P2. When the retainer 19 continues to rotate from this state, the retainer 19 and the clutch inner ring 13 are connected via the switching pin 21, so that the clutch inner ring 13 rotates together with the retainer 19, and the nut 5 of the ball screw 2 is rotated. Rotation is transmitted. Even when the input member 16 rotates counterclockwise, the rotation is transmitted from the input member 16 to the nut 5 via the clutch inner ring 13 by the same action as described above. The rotation of the nut 5 is converted into an advance / retreat operation of the screw shaft 4.

  Contrary to the above, when a reverse input is applied to the screw shaft 4 of the ball screw 2 from the outside, the forward / backward movement is converted into the rotation of the nut 5, but the rotation is blocked by the clutch 3. Thus, the forward / backward movement of the screw shaft 4 is prevented. That is, when the nut 5 is rotated counterclockwise by the reverse input from the state of FIG. 3, the clutch inner ring 13 is rotated counterclockwise with respect to the cage 19 of the input member 16 as shown in FIG. Then, the engagement element 15 relatively moves to the engagement operation position P2. The engagement element 15 that has come to this position P2 is about to move toward the narrower side of the wedge space and is locked, and the clutch inner ring 13 is locked to the fixed clutch outer ring 14 via the engagement element 15. As a result, the nut 5 meshed with the clutch inner ring 13 by the gears 37 and 38 does not rotate any more, and the rotation of the nut 5 is not transmitted to the input member 16. That is, the reverse input from the nut 5 is prevented from being transmitted to the input member 16. Even when the rotation of the nut 5 by the reverse input is clockwise, transmission to the input member 16 is prevented by the same action.

  According to the ball screw actuator mechanism 1 for a variable compression ratio engine of this configuration, the rotation of the motor 34 is transmitted to the nut 5 of the ball screw 2 through the clutch 3 and converted into a linear motion by the ball screw 2 to reciprocate the engine. It is transmitted to the child 72. Since the ball screw 2 is used as a motion conversion mechanism for rotation and linear motion, the transmission efficiency is high, the response speed is increased as compared with the sliding screw mechanism, and the power consumption can be reduced. For example, it can be expected that power consumption of about 1/3 of the sliding screw mechanism is sufficient. Since the ball screw 2 has high transmission efficiency, the nut 5 tries to rotate by the axial force applied to the screw shaft 4 from the reciprocating operation element 72. However, since the reverse input limiting type is used for the clutch 3, the nut 5 Therefore, the rotation of the nut 5 is prevented, and the rotation of the nut 5 is prevented. Further, since the rotation from the nut 5 to the motor 34 side is prevented, it is not necessary to pass a large current to the motor 34 to hold the position of the reciprocating operation element 72 of the engine by the braking force by the motor 34. Electric power is planned. In addition, motor burnout and the like are prevented.

  FIG. 5 shows an example of a variable compression ratio engine using the ball screw actuator mechanism 1 of this embodiment. In each cylinder 52 of the cylinder block 51, a piston 53 is disposed so as to be movable up and down, and a piston pin 55 of each piston 53 and a crank pin 57 of a crankshaft 56 are a variable link ratio mechanism of a multi-link type. 70 are mechanically connected to each other. A counterweight 58 is provided on the crankshaft 56.

  The variable compression ratio mechanism 70 has a lower link 61 whose one end is fitted to the crank pin 57 so as to be relatively rotatable, an upper link 62 that connects the lower link 61 and the piston pin 55, and the crankshaft 16. And a control shaft 63 extending. An eccentric cam 64 is eccentrically provided on the control shaft 63, and the eccentric cam 64 and the lower link 62 are connected by a control link 65. A control plate 56 is provided on the control shaft 63, and a pin 73 provided at the tip of the reciprocating operation element 72 is slidably engaged with a slit 67 provided in the control main body 56.

  A ball screw actuator mechanism 1 according to the embodiment of FIG. 1 is provided as an actuator for moving the reciprocating operation element 72 back and forth. The reciprocating operation element 72 may be connected to the screw shaft 4 in the ball screw actuator mechanism 1 or may be composed of the screw shaft 4.

  In the variable compression ratio mechanism configured as described above, when the reciprocating operation element 72 is advanced and retracted by the ball screw actuator mechanism 1, the control plate 56 connected thereto by the pin 73 is rotated. By the rotation of the control plate 56, the position of the eccentric cam 64 serving as the swing fulcrum of the control link 65 changes, the posture of the lower link 61 and the upper link 62 changes, and the top dead center position due to the reciprocating motion of the piston 53. Changes. For this reason, the compression ratio of the combustion chamber partitioned by the piston 53 in the cylinder 52 changes. Thus, the compression ratio is variable by moving the reciprocating operation element 72 back and forth.

  FIG. 6 shows a ball screw actuator mechanism 1A for a variable compression ratio engine according to another embodiment of the present invention. In this embodiment, the clutch 3 is provided on the outer periphery of the nut 5 of the ball screw 2 in place of the configuration in which the clutch 3 is provided in parallel with the screw shaft 4 of the ball screw 2 in the first embodiment. In this embodiment, the parts functionally corresponding to those of the first embodiment are denoted by the same reference numerals, and description thereof is partially omitted.

  The nut 5 of the ball screw 2 is rotatably supported at one end (the left side in FIG. 6) in the main body 7 a of the housing 7 via a bearing 8. The bearing 8 is a double-row angular ball bearing, and its inner ring 9 is a split type. The inner ring 9 of the bearing 8 fitted to the outer periphery of the nut 5 presses the width surface of one end against the flange 5b integrally formed on the outer periphery of the nut 5, and the other end width surface is the outer diameter surface of one end portion of the nut 5. It is fastened and fixed in the axial direction by tightening with an inner ring fixing nut 11 that is screwed onto the inner ring. Further, the outer ring 10 of the bearing 8 fitted to the inner periphery of the housing body 7a presses the width surface at one end against the stepped portion 7c formed at the inner periphery of the housing body 7a, and the width surface at the other end of the housing main body 7a. It is fastened and fixed in the axial direction by tightening with an outer ring fixing nut 12 screwed into the inner diameter surface of 7a.

  The clutch 3 is a reverse input restriction type two-way clutch. A clutch 3 that transmits rotation from the input member 16 to the nut 5 but blocks transmission of rotation from the nut 5 to the input member 16 is used. The clutch 3 includes a clutch inner ring 13, a clutch outer ring 14, a plurality of engagement elements 15, and a cage 19.

  The clutch inner ring 13 is fitted to the outer periphery of a cylindrical portion 5 c (on the right side in FIG. 1) provided at the other axial end of the nut 5 in a non-rotating state with respect to the nut 5. The clutch outer ring 14 is positioned concentrically with the clutch inner ring 13 on the outer periphery of the clutch inner ring 13. The clutch outer ring 14 is fixed to the inner periphery of the housing body 7a and becomes a member on the fixed side. The plurality of engagement elements 15 are composed of rollers and are interposed between the clutch inner ring 13 and the clutch outer ring 14. The retainer 19 is a member that retains the plurality of engagement elements 15.

  The input member 16 is a hollow shaft, and the other end (the right side in FIG. 6) of the screw shaft 4 is inserted into the input member 16 so as to freely advance and retract. The input member 16 is rotatably supported by bearings 17 and 18 at a position facing the nut 5 in the housing body 7a in the axial direction. A ring-shaped cage 19 that is inserted between the clutch inner ring 13 and the clutch outer ring 14 and holds the engagement element 15 is integrally formed at one end portion (left side in FIG. 1) of the input member 16. Yes. That is, the cage 19 is a member that becomes a part of the input member 16. The input member 16 and the clutch inner ring 13 are connected by the connecting means 20 with play in the rotational direction. The connecting means 20 includes a circumferential pin provided on the end surface of the clutch inner ring 13 facing the input shaft 15, such as a switching pin 21 protruding in the axial direction from the end surface facing the nut 5 of the input shaft 16. It is inserted into the loose fitting recess 22 made of.

  The surface facing the clutch inner ring 13 on the inner diameter surface of the clutch outer ring 14 is a cylindrical surface 23. In the clutch inner ring 13, as in FIG. 3 showing the first embodiment, cam surfaces 24 are formed at a plurality of positions in the circumferential direction on the outer diameter surface, and each of these cam surfaces 24 and the cylindrical surface 23 of the clutch outer ring 14. The engagement element 15 is disposed between the two. The cam surface 24 is a surface that forms a wedge space in which the engagement element 15 is engaged with the cylindrical surface 23 of the clutch outer ring 14. The cam surface 24 is a flat surface, and forms a wedge space in both forward and reverse directions as the wedge space. The wedge spaces on both sides are symmetrical. The retainer 19 has a pocket 25 for retaining each engagement element 15. The pocket 25 is formed in a circumferential width of the cage in which the engagement element 15 fits with play. In the pocket 25, elastic bodies 25 that urge the engaging element 15 toward the center of the pocket 25 are disposed on both sides of the engaging element 15. The elastic body 26 is made of, for example, a leaf spring and is attached to the cage 19.

  The engagement element 15 is formed in a cylindrical shape of the cam surface 24 and the clutch outer ring 14 from a central position of the cam surface 24 that is a neutral position (position shown in FIG. 3) where the clutch inner ring 13 is not engaged with the clutch inner ring 13. It can move to the engagement operation position P2 (FIG. 4) which is the most approach position to the wedge space formed with the surface 23. This movement is possible in both forward and reverse directions, and the engagement element 15 is movable relative to the clutch inner ring 13 by a distance twice as long as the neutral position and the engagement operation position P2. The amount of play in the rotational direction between the cage 19 and the clutch inner ring 13, that is, the amount of play X allowed by the switching pin 21 and the loose fitting recess 22 (the amount of play on one side) is determined by the engagement element 15. Is set to be substantially the same as the amount of movement from the neutral position to the engagement operation position P2.

  A gear 27 is provided on the outer periphery of the input member 16, and a gear 28 of a speed reducer that reduces the rotational output of a motor (not shown) enters through an opening 7d formed in a part of the housing body 7a and inputs. It is engaged with the gear 27 of the member 16. Thereby, the rotational output of the motor is decelerated by the reduction gear and transmitted to the input shaft 16.

  Since the operation of the ball screw actuator mechanism 1A of this embodiment is the same as that of the first embodiment, description thereof is omitted.

  7 to 13 show still another modification of the clutch used as the reverse input limiting means. The clutch 3B in this example uses an engaging element 15B made of sprags. The outer ring 14B is fixed to a stationary housing (FIG. 1). An inner diameter surface of the outer ring 14 </ b> B is formed by a circumferential surface 89. Inside the outer ring 14B, an input member 16B and a clutch inner ring 13B are inserted from both sides along the axis, and a cylindrical outer cage 19Ba is press-fitted and fixed to the outer diameter surface of the input member 16B. The clutch inner ring 13B serves as a clutch output member. The outer diameter surface of the clutch inner ring 13B is formed on a cylindrical surface 88 coaxial with the cylindrical surface 89 of the outer ring 14B, and a cylindrical inner cage 19Bb is fixed to the cylindrical surface 88 by a switch pin 21B. A plurality of pockets 25Ba and 25Bb are formed at equal intervals in the circumferential direction in the outer retainer 19Ba and the inner retainer 19Bb, respectively, and the opposing pockets 25Ba and 25Bb have an engaging element 15B made of sprags and an engaging element. An elastic body 26B that holds 15B is incorporated. The elastic body 26B is made of a spring such as a leaf spring.

  As shown in FIG. 9, the engaging member 15B made of sprags has two cam surfaces 92 and 93 having a radius of curvature R1 centered on O1 on the outer diameter side and a radius of curvature R2 centered on O2 on the inner diameter side. When the cam surface 94 is tilted in the circumferential direction, the cam surfaces 92 and 94 (the cam surfaces 93 and 94 when tilted in the opposite direction) are the cylindrical surface 89 of the outer ring 14B and the cylinder of the clutch inner ring 13B. It comes into contact with the surface 88 and enters an engaged operation state (a state in which the clutch can be engaged). When the input member 16B is in a state of being neutral with the clutch inner ring 13B in the circumferential direction, the elastic body 26B presses and raises the engaging member 15B made of sprags from both sides, and the cylindrical surfaces 88 and 89 and the engaging member 15 Are held in a neutral position where they are not engaged.

  On the other hand, as shown in FIG. 8, a switch pin 21B extending in the radial direction is fixed to the surface of the clutch inner ring 13B, and the tip of the switch pin 21B is formed by a square hole or the like provided in the peripheral surface of the outer cage 19Ba. It is inserted in the loose fitting recess 22B. These switch pins 21B and loose fitting recesses 22B constitute a connecting means 20B. A rotational play X that allows the outer cage 19Ba (input member 16B) and the clutch inner ring 13B to rotate relative to each other is formed between the circumferential side walls of the loose fitting recess 25B and the switch pin 21B. . In FIG. 8, the size of the play X in the rotational direction is set to be approximately the same as the amount of rotation required to move from the neutral position where the engagement element 15B made of sprags is not engaged to the engagement operation position. .

  The operation of the clutch 6B having this configuration will be described. When the input member 16B is in a circumferentially neutral state with the clutch inner ring 13B, the engaging element 15B is kept in a neutral state in which it is not engaged between the cylindrical surfaces 88 and 89 by the urging of the elastic body 26B as shown in FIG. Be drunk. Now, as shown in FIG. 11, when the input member 16B rotates in the direction of the arrow, the outer cage 19Ba fixed to the input member 16B also starts to rotate. Due to the rotation of the outer cage 19Ba, the elastic body 26B tilts the sprag engagement element 15B, and the cam surfaces 92 and 94 (or 93 and 94) of the engagement element 15B are respectively the cylindrical surface 89 of the outer ring 14A and the clutch inner ring 13B. The cylinder surface 88 is engaged, and the engagement operation state is obtained. However, at this time, the rotation of the outer cage 19Ba causes the switch pin 21B fixed to the inner wall surface of the loose fitting recess 22B and the clutch inner ring 13B to contact at the contact point A, so that the input member 16B (outer cage 19Ba) and The clutch inner ring 13B (inner retainer 19Bb) and the engagement element 15B start to rotate together. At this time, the engagement element 15B is engaged and activated, but the clutch inner ring 13B begins to rotate, so that it receives and clamps a load on the side where the outer ring 14B stands by friction at the contact point with the cylindrical surface 89. Without rotation, the rotation of the input member 16B is transmitted to the clutch inner ring 13B.

  On the other hand, when a reaction force is generated on the clutch inner ring 13B side and the clutch inner ring 13B attempts to rotate in the direction of the arrow in FIG. 12, the sprag engagement member 15B has a predetermined wedge angle α with the inner and outer cylindrical surfaces 88. Since it is engaged between the clutches 89, the rotation of the clutch inner ring 13B stops and is not transmitted to the input member 16B. At this time, considering the state in which the input member 16B is rotated from the state in which the engagement element 15B is engaged as shown in the figure, first, when the input member 16B is rotated clockwise in FIG. 12, the outer cage 19Ba Since the wall surface of the loose fitting recess 22B and the switch pin 21B are in contact with each other, the clutch inner ring 13B is also rotated clockwise, and the engagement element 15B is idled by receiving frictional force in a direction to stand by contact with the cylindrical surface 89 of the outer ring 14B. The clutch inner ring 13B is rotated by the input member 16B. On the other hand, when the input member 16B is rotated counterclockwise in FIG. 13, the side surface of the pocket 25Ba of the outer cage 19Ba comes into contact with the engaging element 15B at the contact point B, and is engaged between the inner and outer cylindrical surfaces 88 and 89. Since the engaged engagement element 15B is raised and the engagement is released, reverse rotation is possible.

  In each of the above-described embodiments, the case where a two-way clutch is used as the clutch 3 is described as an example. However, a reverse input restriction type one-way clutch may be used. In the case of a one-way clutch, for example, rotation from the input member to the nut is transmitted in all directions, but rotation transmission from the nut to the input member is interrupted only in either the forward or reverse direction. Such a one-way clutch forms a wedge space in one direction instead of a configuration in which a bidirectional wedge space is formed between the inner ring 13 and the outer ring 14 in the two-way clutch type clutch 3 shown in FIG. It is obtained by.

  In each of the above embodiments, the clutches 3 and 3B are of a roller type or a sprag type. However, the clutch 3 may be of a reverse input limiting type, for example, a spring clutch type.

1 is a longitudinal sectional view of a ball screw actuator mechanism for a variable compression ratio engine according to a first embodiment of the present invention. It is an expanded sectional view of the clutch part of the ball screw actuator mechanism. It is a cross-sectional view of the clutch. It is operation | movement explanatory drawing of the clutch. It is sectional drawing which shows an example of the variable compression ratio engine using the ball screw actuator mechanism. It is sectional drawing of the ball screw actuator mechanism for variable compression ratio engines concerning other embodiment of this invention. It is a longitudinal cross-sectional view of the clutch in the ball screw actuator mechanism for variable compression ratio engines concerning further another embodiment of this invention. It is a cross-sectional view of the clutch. It is explanatory drawing of the engaging element which consists of a sprag of the clutch. It is explanatory drawing of the operation state of the clutch. It is explanatory drawing of the other operation state of the clutch. It is explanatory drawing of the other operation state of the clutch. It is explanatory drawing of the other operation state of the clutch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Variable screw ratio engine ball screw actuator mechanism 2 ... Ball screw 3, 3A ... Clutch 4 ... Screw shaft 5 ... Nut 13 ... Clutch inner ring 14 ... Clutch outer ring 15, 15A, 15B ... Encoder 16 ... Input members 19, 19B ... Retainer 20, 20B ... Connection mechanism 21, 21B ... Switching pin 22,22B ... Free fitting recess 24 ... Cam surface 70 ... Variable compression ratio mechanism 72 ... Reciprocating operator

Claims (4)

A ball screw actuator mechanism for a variable compression ratio engine that is used in a variable compression ratio engine that changes the compression ratio by changing the top dead center position of the piston according to the reciprocating position of the reciprocating element. ,
A ball screw in which a plurality of balls are interposed between a screw shaft and a screw groove of the nut, the nut is rotatably installed with respect to the housing, and the screw shaft is allowed to advance and retreat, and the motor rotates the ball. A rotation transmission system for transmitting to the nut of the screw, and a clutch interposed in the rotation transmission system, the clutch transmits the rotation from the input member to which the drive of the motor is input to the nut; A ball screw actuator mechanism for a variable compression ratio engine, characterized in that it is a reverse input limiting clutch that blocks transmission of rotation to the input member.   2. The clutch according to claim 1, wherein the clutch includes a clutch outer ring fixed to the housing, a rotatable clutch inner ring positioned on an inner periphery of the clutch outer ring, and a plurality of engagement elements interposed between the clutch outer ring and the clutch inner ring. And a ball screw actuator mechanism for a variable compression ratio engine having a retainer for holding the plurality of engagement elements, and the retainer serves as an input member.   3. The retainer according to claim 2, wherein the engagement element comprises a roller, and a cam surface that forms a wedge-shaped space for engaging the engagement element between the clutch inner ring and the clutch outer ring is provided on an outer diameter surface of the clutch inner ring. And a clutch-equipped ball screw having coupling means for coupling the inner ring and the clutch inner ring in a rotational direction via a predetermined play. The ball screw with a clutch according to any one of claims 1 to 3, wherein the clutch portion is a two-way clutch.

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