Electric actuator and electric parking brake device

Abstract

Provided is an electric actuator in which the number of movable parts in a motion conversion mechanism is small, and which has quietness of a small striking sound when an electrical driving part is operated. This electric actuator comprises: an electrical driving source which generates a rotary motion as a driving force; and a motion conversion mechanism which converts the rotary motion into a linear motion. The motion conversion mechanism has: a first member which is prevented from a rotary motion and a linear motion; and a second member which engages with the first member and rotates relative to the first member, thereby generating a linear motion, wherein the second member is rotationally driven by the driving force of the electrical driving source.

Description

[Technical Field]

[0001] The present invention relates to an electric parking brake device that includes an electric actuator and a parking brake mechanism operated thereby. [Background technology]

[0002] The electric actuator in the electric parking brake device disclosed in Patent Document 1 comprises a motor and a motion conversion mechanism that converts the rotational driving force of the motor into linear motion, and this motion conversion mechanism is composed of a male screw member that is supported on the actuator case and allows only linear motion, and a female screw member that is threadedly engaged with the male screw member and is supported on the actuator case and allows only rotation, and the male screw member is rotated by the driving force of the motor, thereby generating linear motion in the male screw member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5960534 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the motion conversion mechanism of the above-mentioned electric actuator disclosed in Patent Document 1, both the male screw member and the female screw member must generate rotational or linear motion, so there is unavoidable play in their moving parts, which causes a hammering sound when driven by the motor, i.e., the electric drive unit.

[0005] The present invention has been made in consideration of such circumstances, and aims to provide an electric parking brake device that has a quiet electric actuator that reduces the number of moving parts in the motion conversion mechanism and produces little impact noise when the electric drive unit is driven, and a parking brake mechanism that is operated by the electric actuator. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides an electric actuator, the electric actuator comprising an electric drive source capable of generating rotational motion as a driving force, and a motion conversion mechanism for converting the rotational motion into linear motion, the motion conversion mechanism having a first member that is prevented from rotating and linear motion, and a second member that engages with the first member and generates linear motion by rotating relative to the first member, teeth The driving force of the electric drive source R Rotational drive is transmitted through the spline The electric drive unit corresponds to the motor 12 in the embodiment of the present invention described later, and the first and second members correspond to the male threaded cylindrical shaft 25 and the female threaded cylindrical shaft 26, respectively.

[0007] In addition to the first feature, the present invention has a second feature in that the first member and the second member are engaged by screwing.

[0008] Furthermore, in addition to the second feature, the present invention has a third feature in that the second member is provided with a lubricant reservoir facing the threaded portion of the first member. The lubricant reservoir corresponds to grease reservoir 28 in an embodiment of the present invention described below.

[0009] Furthermore, in addition to any one of the first to third features, the present invention has a fourth feature in that the first member is fixed to an actuator case that houses the motion conversion mechanism.

[0010] Furthermore, the present invention is an electric parking brake device, the electric parking brake device is provided with a parking brake mechanism that is brought into a braking state by the operation of an electric actuator, the electric actuator is provided with an electric drive source that generates rotational motion as a driving force, and a motion conversion mechanism that converts the rotational motion into linear motion, the motion conversion mechanism has a first member that is prevented from rotating and linear motion, and a second member that generates linear motion by rotating relative to the first member, to The driving force of the electric drive source R Rotational drive is transmitted through the spline The fifth feature is that the parking brake mechanism is brought into a braking state by the above.

[0011] Furthermore, in addition to the fifth feature, the present invention has a sixth feature in that the second member is connected to the parking brake mechanism via a transmission member, and a bearing that allows relative rotation between the second member and the transmission member is interposed between the two members. The transmission member corresponds to output cable 14 in an embodiment of the present invention described below.

[0012] Furthermore, in addition to the sixth feature, the present invention has a seventh feature in that the first member is provided with a hollow portion through which the transmission member is inserted.

[0013] Furthermore, in addition to the sixth or seventh feature, the present invention has an eighth feature in that the second member and the transmission member are connected via an elastic member, which corresponds to a group of disc springs 37 in an embodiment of the present invention to be described later.

[0014] According to the first feature of the present invention, of the first and second members constituting the motion conversion mechanism, the first member is prevented from rotating and moving linearly, thereby reducing the number of moving parts in the motion conversion mechanism and contributing to improving the quietness of the electric actuator.

[0015] According to the second feature of the present invention, the first member and the second member are engaged by screwing together, so that the second member itself can generate linear motion as the second member rotates.

[0016] According to the third feature of the present invention, the threaded portion of the first member faces the lubricating oil reservoir of the second member, thereby lubricating the threaded portions of both members and allowing the second member to rotate smoothly while threaded.

[0017] According to the fourth feature of the present invention, the first member is fixed to a case that houses the motion conversion mechanism including the first member, thereby making it possible to reliably prevent rotation and linear motion of the first member.

[0018] According to the fifth aspect of the present invention, it is possible to provide an electric parking brake device that is very quiet.

[0019] According to a sixth feature of the present invention, the second member is connected to the parking brake mechanism via a transmission member, and a bearing is interposed between the second member and the transmission member to allow relative rotation between the two members, thereby preventing transmission of rotational motion from the second member to the transmission member.

[0020] According to the seventh feature of the present invention, a hollow portion is provided in the first member through which the transmission member is inserted, so that the transmission member can be connected to the second member without being obstructed by the first member.

[0021] According to the eighth feature of the present invention, when the parking brake mechanism is put into a braking state by pulling the transmission member due to the linear movement of the second member, a repulsive force is stored in the elastic member between the second member and the transmission member, thereby suppressing loosening of the parking brake mechanism and the transmission member, and stabilizing the braking state of the parking brake mechanism. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a vertical cross-sectional side view showing an electric actuator according to a first embodiment of the present invention in an inoperative state. [Figure 2] FIG. 4 is a vertical cross-sectional side view showing the electric actuator in an operating state. [Figure 3] FIG. [Figure 4] FIG. 10 is a longitudinal sectional side view of a main part of an electric actuator in an operating state, showing a second embodiment of the present invention. [Figure 5] FIG. 3 is a longitudinal cross-sectional view showing a main part of the electric actuator in a non-operating state. DETAILED DESCRIPTION OF THE INVENTION

[0023] First, a first embodiment of the present invention will be described with reference to the accompanying drawings 1 to 3. FIG.

[0024] 1 and 3, the electric actuator A comprises an actuator case 10 and an actuator mechanism 11 housed therein. In this electric actuator A, the direction in which an output cable 14 (described later) extends from the actuator case 10 is the front, and the opposite direction is the rear.

[0025] The actuator case 10 has a cylindrical motor case portion 10a, a cylindrical output case portion 10b arranged adjacent to and parallel to the motor case portion 10a, and a gear case portion 10c connecting the rear end of the motor case portion 10a to the middle portion of the output case portion. The front end of the motor case portion 10a is a removable cap 10a'.

[0026] Furthermore, the actuator case 10 is divided into a front half case body 10A including the main part of the motor case portion 10a and a rear half case cover 10B to enable assembly and disassembly of the actuator mechanism 11. The case body 10A and the case cover 10B are made of synthetic resin.

[0027] The actuator mechanism 11 is composed of a motor 12 housed in the motor case section 10a, an output cable 14 that extends to the outside by passing through a cable outlet 13 in the front end wall of the output case section 10b, a reduction gear train 20 housed in the gear case section 10c that reduces the rotational driving force of the rotor shaft 17 of the motor 12 and transmits it from the pinion gear 18 to a ring-shaped final gear 19, and a motion conversion mechanism 21 housed in the output case section 10b that converts the rotational motion of the final gear 19 into linear motion and transmits it to the output cable 14.

[0028] The final gear 19 is rotatably supported by a cylindrical support shaft 23 that is integral with the output case portion 10b. The final gear 19 is housed in an arc-shaped gear housing 24 of the output case portion 10b such that its axial movement is restricted.

[0029] The motion conversion mechanism 21 is composed of an externally threaded cylindrical shaft 25 having an anchor flange 25b fixed to the front end wall of the output case portion 10b by molding or the like and having an external thread 25a formed on its outer peripheral surface, and an internally threaded cylindrical shaft 26 having an internal thread 26a formed on its inner peripheral surface to be threaded onto the external thread 25a, and the final gear 19 is slidably fitted onto the external peripheral surface of the internally threaded cylindrical shaft 26 via a spline 27. A hollow portion 25c of the externally threaded cylindrical shaft 25 is connected to the cable outlet 13.

[0030] In this way, the male threaded cylindrical shaft 25 is fixed to the output case portion 10b, and the final gear 19 allows the female threaded cylindrical shaft 26 to move axially while integrally rotating and driving the female threaded cylindrical shaft 26. The female threaded cylindrical shaft 26 can move axially within the output case portion 10b with a certain stroke, that is, between a non-operating position (state in Figure 1) close to the anchor flange 25b and an operating position (state in Figure 2) farthest from the anchor flange 25b, by changing the position of engagement with the male threaded cylindrical shaft 26 through its rotation. The male threaded cylindrical shaft 25 and the female threaded cylindrical shaft 26, which are engaged with each other, are in an irreversible relationship in which relative rotation does not occur due to thrust load.

[0031] The male thread 25a of the male threaded cylindrical shaft 25 is formed over the entire length of the male threaded cylindrical shaft 25, while the female thread 26a of the female threaded cylindrical shaft 26 is formed on a part of the front end side of the female threaded cylindrical shaft 26, and a grease reservoir 28 surrounding the female thread 26a is formed on the other inner surface, and grease 28 is stored in this grease reservoir 28.

[0032] The output cable 14 is connected to the female threaded cylindrical shaft 26 as follows.

[0033] That is, the output cable 14 is arranged by being inserted through the cable outlet 13 of the actuator case 10 and the hollow portion 25c of the male threaded cylindrical shaft 25. A boss of a flange-shaped cable inner terminal 14a is fixed to the rear end of this output cable 14 by brazing or the like.

[0034] Meanwhile, an annular recess 30 having an annular step 30a is provided on the inner circumference of the rear end of the male threaded cylindrical shaft 25, and this annular recess 30 accommodates an annular support plate 31 that abuts against the annular step 30a, a bearing plate 32 that is supported on this support plate 31, and the cable inner terminal 14a that is rotatably and slidably supported on this bearing plate 32, and a circlip 33 that prevents the cable inner terminal 14a from coming off the annular recess 30 is engaged with the inner peripheral surface of the opening of the annular recess 30. Grease is applied around the periphery of the bearing plate 32. Thus, this bearing plate 32 plays a role in preventing the rotation of the support plate 31 from being transmitted to the cable inner terminal 14a.

[0035] A bellows-type dustproof boot 34 is attached between the outer periphery of the cable outlet 13 of the actuator case 10 and the middle part of the output cable 14 to cover the output cable 14 therebetween.

[0036] A cable outer terminal 14b is fixed to the outer end of the output cable 14, and this cable outer terminal 14b is connected to a parking brake mechanism P in a known drum brake B. Thus, the electric actuator A and the parking brake mechanism P constitute the electric parking brake device of the present invention.

[0037] Next, the operation of this first embodiment will be described.

[0038] When the parking brake mechanism P is in a non-braking state, in the electric actuator A, as shown in Fig. 1, the female threaded cylindrical shaft 26 is held in a non-operating position close to the anchor flange 25b of the male threaded cylindrical shaft 25. In the illustrated example, the forward and reverse rotation of the motor 12 causes the final gear 19 to rotate counterclockwise and clockwise, and the male thread 25a and female thread 26a that are threaded together are formed as right-hand threads.

[0039] Now, when the motor 12 is driven in the forward direction to operate the parking brake mechanism P, the rotation is slowed down by the reduction gear train 20 and transmitted to the final gear 19, which then drives it to rotate counterclockwise. The counterclockwise rotation of this final gear 19 is then transmitted to the female threaded cylindrical shaft 26 via the spline 27, and this female threaded cylindrical shaft 26 rotates counterclockwise relative to the male threaded cylindrical shaft 25 fixed to the actuator case 10, causing it to move linearly rearward, i.e., away from the anchor flange 25b of the male threaded cylindrical shaft 25, while sliding on the spline 27 of the final gear 19, and this thrust force is transmitted to the cable inner terminal 14a via the support plate 31 and the bearing plate 32, pulling the output cable 14 to the operating position shown in Fig. 2, and putting the parking brake mechanism P into an operating state, i.e., into a braking state.

[0040] At this time, since the cable inner terminal 14a is supported on the support plate 31 via the bearing plate 32, even if the support plate 31 rotates together with the female threaded cylindrical shaft 26, the rotation is blocked by the bearing plate 32, and the cable inner terminal 14a does not rotate. In this way, twisting of the output cable 14 can be prevented.

[0041] When the parking brake mechanism P is in the braking state, a sensor (not shown) detects a predetermined load state (e.g., current value) of the motor 12, thereby stopping the forward rotation of the motor 12. The operating state of the parking brake mechanism P is maintained by the irreversible transmission function of the male threaded cylindrical shaft 25 and the female threaded cylindrical shaft 26 that are screwed together.

[0042] Next, when the motor 12 is rotated in the reverse direction, the above action proceeds in the opposite direction, causing the female threaded cylindrical shaft 26 to retreat to its original inoperative position, thereby returning the parking brake mechanism P to its non-braking state.

[0043] By fixing the male threaded cylindrical shaft 25 to the actuator case 10 via the anchor flange 25b as described above, in the motion conversion mechanism 21, the only moving part that causes hammering noise when the motor 12 rotates forward and backward is the sliding engagement portion of the spline 27 between the final gear 19 and the female threaded cylindrical shaft 26. Moreover, since the spline 27 is provided on the outer peripheral surface of the female threaded cylindrical shaft 26, which has the largest diameter in the motion conversion mechanism 21, the play in the rotational direction between the final gear 19 and the female threaded cylindrical shaft 26 caused by the sliding clearance of the spline 27 is small. Therefore, the hammering noise caused by this play is extremely small. In this way, the quietness of the electric actuator A can be achieved.

[0044] Furthermore, when the electric actuator A shown in Figure 1 is in an inoperative state, the grease reservoir 28 inside the female threaded cylindrical shaft 26 surrounds the male thread 25a of the male threaded cylindrical shaft 25, lubricating the male thread 25a. As the female threaded cylindrical shaft 26 rotates, the entire threaded portion of the male thread 25a and the female thread 26a can be lubricated, thereby allowing the female threaded cylindrical shaft 26 to rotate smoothly.

[0045] Furthermore, the output cable 14 passes through the hollow portion 25c of the male threaded cylindrical shaft 25, and the cable inner terminal 14a fixed to the inner end of this output cable 14 is connected to the inner end of the female threaded cylindrical shaft 26, so that the output cable 14 can be connected to the female threaded cylindrical shaft 26 without being obstructed by the male threaded cylindrical shaft 25, thereby improving space efficiency.

[0046] Next, a second embodiment of the present invention will be described with reference to FIGS.

[0047] The annular recess 30 at the rear end of the female threaded cylindrical shaft 26 accommodates, from the front, a first support plate 31, a group of disc springs 37, a second support plate 36, a bearing plate 32, and a cable inner terminal 14a, and a circlip 33 that prevents these from coming off the annular recess 30 is engaged with the rear end of the annular recess 30. The group of disc springs 37 is formed by stacking a plurality of disc springs 37 with the orientation of their tapered surfaces alternately changed.

[0048] Other configurations are the same as those of the first embodiment, so in FIGS. 4 and 5, parts corresponding to those of the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0049] 4, first, when the female threaded cylindrical shaft 26 is driven toward the operating position (toward the arrow Y1) by the forward rotation of the motor 12 (FIG. 1) to put the parking brake mechanism P (FIG. 1) into the braking state, if the traction force applied to the output cable 14 exceeds the set load of the group of disc springs 37, the group of disc springs 37 is compressed between the first and second support plates 31, 36, and when the female threaded cylindrical shaft 26 reaches the operating position that puts the parking brake mechanism P into the braking state, the group of disc springs 37 is sufficiently compressed and a predetermined repulsive force is accumulated. Therefore, if the parking brake mechanism P or the output cable 14 becomes loose when the motor 12 is stopped, the loosening or slackening will be suppressed by the repulsive force of the group of disc springs 37, and a stable braking state of the parking brake mechanism P can be ensured.

[0050] Next, as shown in FIG. 5 , in order to return the parking brake mechanism P from the activated state to the deactivated state, the motor 12 is rotated in the reverse direction to drive the female threaded cylindrical shaft 26 toward the deactivated position (toward the arrow Y2). This causes the parking brake mechanism P to return to the deactivated state, the disc springs 37 to become free, and the cable inner terminal 14a comes into contact with the circlip 33. This retraction of the female threaded cylindrical shaft 26 causes the first support plate 31 to press against the tip surface of the stationary male threaded cylindrical shaft 25. The resulting reaction force compresses the disc springs 37 between the first support plate 31 and the circlip 33. When the load on the motor 12 resulting from the generation of this compression reaction force reaches a predetermined value (current value), a sensor (not shown) detects this value as a stop signal, thereby stopping the reverse rotation of the motor 12. The compressive load acting on the disc springs 37 also acts on the output cable 14, eliminating play from the output cable 14.

[0051] The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various design changes can be made without departing from the present invention as described in the claims.

[0052] For example, the electric actuator A can be used to operate a parking brake mechanism in a disc brake. Also, the disc springs 37 can be replaced with compression coil springs.

[0053] This application claims priority to Japanese Patent Application No. 2022-166512, filed October 17, 2022. The entire disclosure of Japanese Patent Application No. 2022-166512, filed October 17, 2022, including the specification, claims, drawings, and abstract, is incorporated herein by reference in its entirety. [Explanation of symbols]

[0054] A... Electric actuator P····Parking brake mechanism 10. Actuator case 12. Electric drive source (motor) 14 Transmission member (output cable) 21. Motion conversion mechanism 25... First member (male threaded cylindrical shaft) 25a Male thread 26... Second member (internal thread cylindrical shaft) 26a Female thread 28 Lubricant reservoir (grease reservoir) 32 Bearing (bearing plate) 37 Elastic member (disc spring)

Claims

1. An electric actuator, the electric actuator comprising: an electric drive source capable of generating rotational motion as a driving force; a motion conversion mechanism for converting the rotational motion into linear motion, The motion conversion mechanism a first member that is prevented from rotational and linear movement; a second member that engages with the first member and generates linear motion by rotating relative to the first member; An electric actuator, wherein the second member receives rotational drive force from the electric drive source via a spline.

2. 2. The electric actuator according to claim 1, An electric actuator, characterized in that the first member and the second member are engaged by threaded engagement.

3. 3. The electric actuator according to claim 2, An electric actuator, characterized in that the second member is provided with a lubricating oil reservoir facing the threaded portion of the first member.

4. The electric actuator according to any one of claims 1 to 3, An electric actuator, wherein the first member is fixed to an actuator case that houses the motion conversion mechanism.

5. An electric parking brake device, the electric parking brake device comprising: Equipped with a parking brake mechanism that is braked by the operation of an electric actuator, The electric actuator includes an electric drive source that generates rotational motion as a driving force, and a motion conversion mechanism that converts the rotational motion into linear motion, the motion conversion mechanism has a first member that is prevented from rotating and linearly moving, and a second member that generates linear motion by rotating relative to the first member, An electric parking brake device, characterized in that the parking brake mechanism is activated by rotational drive caused by the driving force of the electric drive source being transmitted to the second member via a spline.

6. 6. The electric parking brake device according to claim 5, The second member is connected to the parking brake mechanism via a transmission member, An electric parking brake device, characterized in that a bearing is interposed between the second member and the transmission member to allow relative rotation between the two members.

7. 7. The electric parking brake device according to claim 6, The electric parking brake device, wherein the first member has a hollow portion through which the transmission member is inserted.

8. The electric parking brake device according to claim 6 or 7, An electric parking brake device, characterized in that the second member and the transmission member are connected via an elastic member.

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