Drive mechanism

Abstract

To provide a drive mechanism which has an excellent lock function, is saved in electric power, and is simple.SOLUTION: A drive mechanism K includes a motor M having a drive shaft Ma, and a speed reduction part G which has a first shaft s1 receiving rotation of the drive shaft Ma, and transmits the rotation to a driving object while reducing the speed of the rotation. The drive mechanism K further includes a switch part C which switches, in coordination with the rotation of the drive shaft Ma, between an unlock state in which the rotation of the first shaft s1 is allowed in the rotation of the drive shaft Ma, and a lock state in which the rotation of the first shaft s1 is regulated in a stop of the drive shaft Ma.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive mechanism including a motor and a speed reduction unit that transmits the driving rotation of the motor to a driving target while reducing the speed.

Background Art

[0002] Conventionally, as such a drive mechanism, there is, for example, one disclosed in Patent Document 1 (see paragraphs

[0006] to

[0007] and FIG. 3).

[0003] This drive mechanism is a steer-by-wire type steering device that converts the rotation of the output shaft of a steering actuator into a linear motion by a linear motion mechanism unit and transmits this to a steering link mechanism. In this device, an outer ring member 13 is arranged concentrically with the outer diameter side of the rotary output shaft 7, a carrier 14 is supported rotatably with respect to the rotary output shaft 7, and planetary rollers 16 supported by this carrier 14 are screwed into the outer ring member 13.

[0004] The planetary roller 16 and the outer ring member 13 are screwed together by a spiral ridge 25 and a circumferential groove 26. The rotation and revolution of the planetary roller 16 are converted into an axial movement, and each planetary roller 16 moves relatively axially with respect to the outer ring member 13 or the rotary output shaft 7. The axial movement of the outer ring member 13 corresponding to the relative movement of each planetary roller 16 is transmitted to the arm of the steering link mechanism, and the steering wheel is steered.

[0005] According to this configuration, the rotation of the rotary output shaft of the steering actuator is converted into the axial movement of the outer ring member by the rotation and revolution of the planetary roller. Therefore, not only does the mechanism of the planetary roller function as a conversion mechanism that converts a rotational force into a linear motion, but it also serves as a speed reduction mechanism, enabling miniaturization and shortening of the axial length. As a result, the steering mechanism of the steer-by-wire type steering device can be housed within the wheelhouse, and a large amount of interior space can be secured. Also, by using a planetary roller as a conversion mechanism that converts a rotational force into a linear motion, load holding is possible, and power saving is also possible while preventing reverse input from the steering wheel during straight driving of the vehicle. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2013-95310 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the conventional drive mechanism described above, the cross-sections of the spiral protrusions 25 and circumferential grooves 26 on the planetary roller 16 and outer ring member 13 are trapezoidal in order to prevent reverse input from the steering wheels when the vehicle is moving in a straight line. However, with this configuration, the mechanical efficiency from the drive rotation from the rotary output shaft to the conversion of linear motion decreases, and there are problems such as the motor becoming larger.

[0008] Thus, the conventional drive mechanism described above has various problems that need to be solved, and there was a need for a drive mechanism that provides good locking functionality when the object to be driven is not in motion, is energy-efficient, and is simple to use. [Means for solving the problem]

[0009] (Feature composition) The characteristic configuration of the drive mechanism according to the present invention is: A motor having a drive shaft supported by a housing, A reduction unit having an input shaft coaxial with the rotation axis of the drive shaft, which reduces the rotation of the drive shaft, A clutch is provided between the drive shaft and the input shaft, and in conjunction with the rotation of the drive shaft, it enters an unlocked state where the rotation of the input shaft is permitted when the drive shaft rotates, and enters a locked state where the rotation of the input shaft is restricted when the drive shaft stops. The system comprises a cylindrical member that rotates upon receiving rotational drive from the reduction unit, and a linear member that screws into the cylindrical member and converts the rotation of the cylindrical member into reciprocating motion. The aforementioned clutch, A friction plate support is mounted to the input shaft so as to rotate integrally with the input shaft in a coaxial manner and so as to be movable along the axis, The friction plate support surface and the end face of the drive shaft are distributed and arranged along the circumferential direction of the axis, and a plurality of cam surfaces and a ball that contacts each of the plurality of cam surfaces, Between the outer circumferential portion of the friction plate support and the inner circumferential surface of the housing, a friction plate is provided in which an annular first friction plate, which is integrally rotatable with respect to the outer circumferential surface and relatively movable in a direction along the axis, and an annular second friction plate, which is non-rotatable with respect to the inner circumferential surface and relatively movable in a direction along the axis, are alternately arranged along the axis. The second friction plate and the friction plate support are pressed together along the axis by an annular pressing plate, A biasing member held in the housing and pressing the pressing plate, The key is that it is equipped.

[0010] (effect) In the non-powered state where the motor is not driven, the switching part is maintained in the locked state in the drive mechanism of this configuration. Therefore, power saving can be achieved when controlling a drive target that is always maintained in the non-powered state.

[0011] Also, since one motor performs the locking operation and unlocking operation of the switching part and the output to the reduction part, the number of components is reduced and cost reduction is possible.

[0012]

[0013] (Effect) In this configuration, when the drive shaft of the motor is not rotating, the pressing plate is pressed against the friction plate and the input shaft is in the locked state. However, when the motor operates, the drive shaft rotates and the rotation-linear motion conversion part releases the pressing of the pressing plate. With such a pressing type clutch using a biasing member, miniaturization of the device is easy and a drive mechanism with excellent mounting property can be obtained.

[0014] Also, since the rotation-linear motion conversion part is arranged coaxially with the rotation axis of the friction plate, the dimension in the radial direction outside the diameter in the switching part is easily reduced, and miniaturization of the drive mechanism is possible.

[0015] Furthermore, since the clutch is provided coaxially with the drive shaft of the motor, it is also easy to configure a connection part to directly transmit the rotational driving force of the motor to the clutch, and a drive mechanism with good mechanical efficiency can be obtained.

[0016]

[0017] (Effect) In the case of a clutch having a cam surface and a ball as in this configuration, the pressing plate can be easily released from pressing due to the effect of the cam surface accompanying the rotation of the drive shaft. The cam surface is provided on the member opposite to the side holding the ball among the drive shaft and the pressing plate, but in addition, it can also be provided on the side holding the ball. Since the ball rolls on the cam surface, the frictional loss can be reduced by providing the cam surface on both members. Such an arrangement of the cam surface and the ball is relatively simple. Therefore, it becomes easy to install a clutch with a simplified and downsized configuration.

[0018] Also, by adjusting the inclination angle of the cam surface, it is easy to set the intermittent responsiveness of the clutch with respect to the rotation angle of the drive shaft. Therefore, the applicable range of the drive mechanism can be expanded.

[0019]

[0020]

Brief Description of the Drawings

[0021] [Figure 1] Cross-sectional view showing the drive mechanism according to the first embodiment [Figure 2] Perspective view showing the main part of the clutch according to the first embodiment [Figure 3] Cross-sectional view showing the drive mechanism according to the second embodiment

Modes for Carrying Out the Invention

[0022] 〔First Embodiment〕 (Overview) The drive mechanism K according to the present invention is used, for example, in an actuator for an electric steering device of a vehicle. The electric steering device is incorporated in, for example, a steering link 1 of a front wheel or a rear wheel, and the direction of the wheel is determined by adjusting the length of a linear motion part 2 by driving a motor M.

[0023] Figures 1 and 2 show the drive mechanism K according to this embodiment. The drive mechanism K includes a motor M and a reduction unit G to drive the linear motion section 2 of the steering link 1, which is the object to be driven. The linear motion section 2 includes a cylindrical member 2a that rotates on the outside and a linear motion member 2b that is screwed into the inside of the cylindrical member 2a via a ball screw 3 and moves back and forth. A part of the linear motion member 2b is provided with, for example, a convex guide portion 2b1, and this guide portion 2b1 is guided by a groove portion 1a formed on the inner surface of the steering link 1, so that the linear motion member 2b can move back and forth without rotation. A large-diameter gear g4 is provided on the outer circumference of the cylindrical member 2a and is driven by the output gear g3 of the reduction unit G. The cylindrical member 2a and the large-diameter gear g4 function as the third shaft s3 of the reduction unit G.

[0024] (Deceleration section) The reduction unit G consists of a first shaft s1, which is an input shaft s1 driven by the drive shaft Ma of the motor M described later, and a second shaft s2 having an output gear g3. Both the first shaft s1 and the second shaft s2 are supported at both ends by bearings. The first shaft s1 is provided with a small-diameter first gear g1, and the second shaft s2 is provided with a large-diameter second gear g2. The second shaft s2 is further provided with a small-diameter output gear g3, which meshes with a large-diameter gear g4 on the cylindrical member 2a, which is the third shaft s3. Thus, the reduction unit G of this embodiment has a three-stage gear train.

[0025] The gears in the reduction unit G are all spur gears and are simply constructed. Using spur gears reduces friction due to gear tooth meshing, resulting in a highly efficient gear transmission mechanism.

[0026] (motor) The first shaft s1 of the reduction unit G receives rotational drive input from the drive shaft Ma of the motor M. The configuration of the motor M is arbitrary; for example, various DC motors driven by 12V can be used. The motor M is driven by a separately provided control unit ECU, which sets the rotational speed and direction according to various operating conditions.

[0027] (clutch) It is desirable that the linear motion member 2b be completely stopped when no steering instruction is given. However, the reverse input acting from the wheels on the steering link 1 etc. will cause the reduction unit G and the drive shaft Ma of the motor M to rotate in a driven manner. The reverse input acting on the linear motion member 2b causes the cylindrical member 2a to rotate in a driven manner via the ball screw 3. Since the reduction unit G that meshes with the cylindrical member 2a is composed of spur gears, the second shaft s2 and the first shaft s1 also rotate in a driven manner. Furthermore, the drive shaft Ma of the motor M which is linked to the first shaft s1 may also rotate in a driven manner when the motor M is not energized.

[0028] Therefore, in this embodiment, a switching unit C is provided to prevent the driven rotation. The switching unit C is a so-called clutch C1 and comprises at least one friction plate P that rotates in accordance with the motor M, a pressing plate Q positioned opposite the friction plate P, and a biasing member F that presses the pressing plate Q against the friction plate P. A rotation-to-linear motion conversion unit is formed which is provided coaxially with the rotation axis X of the friction plate P and releases the pressure on the pressing plate Q.

[0029] This switching unit C releases the pressure between the pressure plate Q and the friction plate P when the drive shaft Ma of the motor M rotates, resulting in an unlocked state where rotation of the first shaft s1 is permitted. Conversely, when the drive shaft Ma is stopped, the pressure plate Q is pressed against the friction plate P, restricting the rotation of the first shaft s1 and resulting in a locked state.

[0030] More specifically, as shown in Figures 1 and 2, a friction plate support H is provided between the drive shaft Ma and the first shaft s1. The friction plate support H has a disc-shaped base H1, and one side of the base H1 is provided with a cylindrical boss H2. The first shaft s1 is slidably engaged inside this boss H2.

[0031] Multiple cam surfaces C1a are formed on the other surface of the base H1, along the circumference of the rotation axis X of the first shaft s1. The cam surfaces C1a are formed as V-shaped recesses, with the center lower and both sides higher along the circumferential direction. A ball C1b abuts against each of these cam surfaces C1a, and the balls C1b are held in recesses Ma1 formed on the end face of the drive shaft Ma. In other words, when the drive shaft Ma rotates in either the forward or reverse direction, it drives the rotation of the balls C1b, and these balls C1b ride up onto either the left or right side of the V-shaped cam surface C1a. As a result, the friction plate support H is pushed toward the first shaft s1 along the rotation axis X.

[0032] The larger the angle of the cam surface C1a, the greater the amount of extrusion of the base H1 relative to the rotation angle of the drive shaft Ma, which allows for quicker release of the pressure between the friction plates P described later.

[0033] Alternatively, the cam surface C1a may be formed on the end face of the drive shaft Ma, and the ball C1b may be held by the base H1. Furthermore, the cam surface C1a is provided on the drive shaft Ma and the pressing plate Q opposite to the side that holds the ball C1b, but it can also be provided on the side that holds the ball C1b. Since the ball C1b rolls against the cam surface C1a, providing the cam surface C1a on both members can reduce frictional losses.

[0034] Thus, with a clutch C1 comprising a cam surface C1a and a ball C1b, the pressure on the pressure plate Q is easily released by the effect of the cam surface C1a in response to the rotation of the drive shaft Ma. In addition, the arrangement of such a cam surface C1a and ball C1b is relatively simple. Therefore, the installation of a compact clutch C1 with a simplified configuration becomes easy. Furthermore, by adjusting the inclination angle of the cam surface C1a, the intermittent response of the clutch C1 to the rotation angle of the drive shaft Ma can be easily set. Therefore, the range of applications for the drive mechanism K can be expanded.

[0035] As shown in Figure 2, the base H1 is in contact with the annular pressure plate Q via a thrust bearing 4. The pressure plate Q is constantly biased toward the base H1 by a plurality of biasing members F that provide a reaction force at the bottom of the housing 5. Here, a coil spring Fa is used as the biasing member F, and a retaining hole 6 is formed in the housing 5 and the pressure plate Q to receive this coil spring Fa. The depth of this retaining hole 6 is set such that even when the pressure plate Q is pushed back until it contacts the housing 5, the coil spring Fa does not completely compress inside the retaining hole 6.

[0036] The outer surface of the base H1 is substantially cylindrical, but at least one protrusion 7 is formed thereon, extending along the axis of rotation X. Multiple friction plates P are arranged on the outer surface of the base H1. There are two types of friction plates P: one is a first friction plate P1, which has at least one notch 8 on its annular inner edge and is configured to engage with the protrusion 7 of the base H1; the other is a second friction plate P2, which has a notch 8 on its annular outer edge. At least one protrusion 7 also extends along the axis of rotation X from the inner surface of the housing 5, and the notch 8 of the second friction plate P2 engages with this protrusion 7.

[0037] In other words, the biasing member F causes the pressing plate Q to press against the first friction plate P1 and the second friction plate P2, thereby preventing relative rotation of both friction plates P, and locking the central base H1. The second friction plate P2 is positioned on the outermost side that contacts the pressing plate Q to prevent it from rotating.

[0038] By incorporating the clutch C1 described above, the drive mechanism K maintains the switching section C in a locked state when the motor M is not being driven and is not energized. Therefore, since it is normally maintained in an energized state, power saving can be enhanced.

[0039] If a press-type clutch C1 using a biasing member F is used, it is easy to miniaturize and obtain a drive mechanism K that is easy to mount. Furthermore, since a single motor M performs both the locking and unlocking operations of the switching unit C and the output to the reduction unit G, the number of components is reduced, making cost reduction possible.

[0040] Because the clutch C1, which is the rotation-to-linear motion conversion unit, is arranged coaxially with the rotation axis X of the friction plate P, the diameter of the clutch C1, especially in the radial outward direction, can be easily reduced, making it possible to miniaturize the drive mechanism K. Furthermore, since the clutch C1 is provided coaxially with the drive shaft Ma of the motor M, it is easy to configure the connection part to directly transmit the rotational driving force of the motor M to the clutch C1, resulting in a mechanically efficient drive mechanism K.

[0041] [Second Embodiment] Figure 3 shows a second embodiment of the present invention. Here, the switching unit C is positioned on the outside, and the components are configured in the order of reduction unit G, motor M, and switching unit C. The configuration of the reduction unit G and motor M is the same, and the base H1 is slidably engaged with the drive shaft Ma of the motor M. A first friction plate P1 and a second friction plate P2 are arranged on the outer circumference of the base H1, and a pressing plate Q is in contact with the second friction plate P2. A biasing member F is provided between the housing 5 and the pressing plate Q. However, the operating mechanism of the switching unit C differs from that of the first embodiment.

[0042] Here, a second motor M2 is used as the switching unit C. The second motor M2 is located further outside the switching unit C, and its second drive shaft Ma2 is screwed into the pressure plate Q. A male threaded portion 9 is formed at the tip of the second drive shaft Ma2, and a female threaded portion 10 that screws into the male threaded portion 9 is formed on the inner surface of a boss portion H2 formed in the center of the pressure plate Q. The pitch of the male threaded portion 9 and the female threaded portion 10 is set appropriately so that the pressure plate Q can move quickly when the second drive shaft Ma2 rotates. In this case, if the power supply to the second motor M2 is released, the position of the pressure plate Q may become unstable. However, in this embodiment, the pressure plate Q is constantly biased toward the second friction plate P2 by the biasing member F, so the switching unit C can maintain its locked state even when the second motor M2 is not energized.

[0043] The second motor M2 is operated under the control unit ECU. During this process, the second motor M2 rotates in forward and reverse directions while coordinating with motor M. This changes the pressure state of the pressure plate Q against the second friction plate P2, and switches the lock state and unlock state of the switching unit C.

[0044] With this configuration, the rotation of the reduction unit G can be restricted when the second motor M2 is not energized. When driving the motor M to change the state of the steering link, the second motor M2 unlocks the motor M, and then the rotational drive of the motor M can be immediately output to the reduction unit G, resulting in a drive mechanism K with excellent control responsiveness.

[0045] [Other Embodiments] In the second embodiment described above, if the pitch between the male screw portion 9 and the female screw portion 10 is small and the second drive shaft Ma2 is difficult to rotate due to reverse input from the motor M, the biasing member F can be omitted. In other words, if the second motor M2 is driven to press the pressing plate Q against the second friction plate P2, and the power supply is stopped while the pressing state of the pressing plate Q is maintained, then the biasing member F is unnecessary.

[0046] In the clutch C1 described above, it is preferable that the rotational drive of the drive shaft Ma is efficiently transmitted to the base H1 after the pressure between the friction plates P is released. To achieve this, it is preferable to provide a contact surface between the end face of the drive shaft Ma and the surface of the base H1 that can transmit rotational force to each other along the circumferential direction. In other words, after the pressure between the friction plates P is released by the ball C1b and the cam surface C1a, the contact surfaces come into contact when the drive shaft Ma is further rotated. This allows the rotational driving force to be transmitted from the drive shaft Ma to the base H1, and prevents the ball C1b and the cam surface C1a from receiving torque from the rotational drive. As a result, wear on the ball C1b and the cam surface C1a is reduced, and the durability of the clutch C1 is improved. [Industrial applicability]

[0047] The drive mechanism of the present invention can be widely used in various actuators that operate an object to be driven using a motor and a reduction unit. [Explanation of Symbols]

[0048] C Switching section C1 Clutch C1a Cam surface C1b Ball F biasing member G reduction section K drive mechanism M Motor Ma drive shaft M2 Second motor P friction plate Q Pressure plate s1 input axis X Rotation axis

Claims

【Request Item 1】

1. A motor having a drive shaft supported by a housing, A reduction unit having an input shaft coaxial with the rotation axis of the drive shaft, which reduces the rotation of the drive shaft, A clutch is provided between the drive shaft and the input shaft, and in conjunction with the rotation of the drive shaft, it enters an unlocked state where the rotation of the input shaft is permitted when the drive shaft rotates, and enters a locked state where the rotation of the input shaft is restricted when the drive shaft stops. The device comprises a cylindrical member that rotates upon receiving rotational drive from the reduction unit, and a linear member that screws into the cylindrical member and converts the rotation of the cylindrical member into reciprocating motion. The aforementioned clutch, A friction plate support is mounted to the input shaft so as to rotate integrally with the input shaft in a coaxial manner and so as to be movable along the axis, The friction plate support surface and the end face of the drive shaft are distributed and arranged along the circumferential direction of the axis, and a plurality of cam surfaces and a ball that contacts each of the plurality of cam surfaces, Between the outer circumferential portion of the friction plate support and the inner circumferential surface of the housing, an annular first friction plate is engaged with the outer circumferential portion so as to be integrally rotatable with respect to the outer circumferential portion and so as to be relatively movable in a direction along the axis. Furthermore, annular second friction plates, which engage with the inner circumferential surface in a manner that is non-rotatable and movable relative to the axis, are arranged alternately along the axis of friction plates, The second friction plate and the friction plate support are pressed together along the axis by an annular pressing plate, A drive mechanism comprising a biasing member held in the housing and pressing the pressing plate.

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