Electric actuator and electric parking brake device

Abstract

Provided is an electric actuator that reduces the number of movable parts of a motion conversion mechanism, and that is quiet when an electric drive unit is operating. An electric actuator provided with an electric drive source that generates a rotational motion as a driving force, and a motion conversion mechanism that converts the rotational motion into a linear motion, the motion conversion mechanism having: a first member that is prevented from rotational motion and linear motion; a second member that engages with the first member and that generates a linear motion by rotating relative to the first member; the second member is driven to rotate by the driving force of an electric driving source.

Description

Technical Field

[0001] The present invention relates to an electric actuator and an electric parking brake device having a parking brake mechanism operated by the electric actuator. Background Art

[0002] The electric actuator in the electric parking brake device disclosed in Patent Document 1 has a motor and a motion conversion mechanism that converts the rotational driving force of the motor into linear motion. The motion conversion mechanism is composed of an externally threaded component that is supported on the actuator housing and is designed to only allow linear motion, and an internally threaded component that is threadedly connected to the externally threaded component and is designed to only allow rotation on the actuator housing. The externally threaded component is driven to rotate using the driving force of the motor, thereby causing the externally threaded component to generate linear motion.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent document 1: (Japan) Patent No. 5960534. Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] However, in the motion conversion mechanism of the above-mentioned electric actuator disclosed in Patent Document 1, since both the external thread component and the internal thread component need to generate rotational motion or linear motion, there is inevitable play in these movable parts, which is the reason why knocking sounds are generated when the motor, i.e., the electric drive unit, is driven.

[0008] The present invention is completed in view of the above situation, and therefore, its purpose is to provide an electric actuator with a reduced movable part of the motion conversion mechanism and a quietness with less knocking sound when the electric drive part is driven, and an electric parking brake device having a parking brake mechanism that works through the electric actuator.

[0009] Technical solutions for solving technical problems

[0010] In order to achieve the above-mentioned purpose, the first feature of the present invention is an electric actuator, which has: an electric drive source that generates rotational motion as a driving force; a motion conversion mechanism that converts the rotational motion into a linear motion; the motion conversion mechanism has: a first component that is prevented from rotating and linear motion; a second component that engages with the first component and generates linear motion by rotating relative to the first component; the second component is driven to rotate using the driving force of the electric drive source. It should be noted that the electric drive source corresponds to the motor 12 of the embodiment of the present invention described later, and the first and second components correspond to the external threaded cylindrical shaft 25 and the internal threaded cylindrical shaft 26, respectively.

[0011] Furthermore, in addition to the first feature, the present invention has a second feature that the first member and the second member are engaged with each other by screwing.

[0012] In addition to the second feature, the third feature of the present invention is that the second member is provided with a lubricating oil reservoir facing the threaded portion of the first member. The lubricating oil reservoir corresponds to the grease reservoir 28 in the embodiment of the present invention described later.

[0013] Furthermore, in addition to any one of the first to third features, the present invention has a fourth feature that the first member is fixed to an actuator housing that houses the motion conversion mechanism.

[0014] In addition, the fifth feature of the present invention is an electric parking brake device, which has a parking brake mechanism that is in a braking state by utilizing the operation of an electric actuator, and the electric actuator has: an electric drive source that generates rotational motion as a driving force; a motion conversion mechanism that converts the rotational motion into linear motion; the motion conversion mechanism has: a first component that is prevented from rotating and linear motion; a second component that generates linear motion by rotating relative to the first component; the parking brake mechanism is put into a braking state by the second component being driven to rotate by utilizing the driving force of the electric drive source.

[0015] In addition, based on the fifth feature, the sixth feature of the present invention is that the second component is connected to the parking brake mechanism via a transmission component, and a bearing is installed between the second component and the transmission component to allow the two components to rotate relative to each other. It should be noted that the transmission component corresponds to the output cable 14 in the embodiment of the present invention described later.

[0016] Furthermore, in addition to the sixth feature, the present invention has a seventh feature that the first member is provided with a hollow portion through which the transmission member is inserted.

[0017] In addition, the eighth feature of the present invention is that the second member and the transmission member are connected via an elastic member. It should be noted that the elastic member corresponds to a disc spring 37 group in an embodiment of the present invention described later.

[0018] 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 linearly moving, so that the movable parts in the motion conversion mechanism can be reduced, thereby contributing to improving the quietness of the electric actuator.

[0019] According to the second feature of the present invention, the first member and the second member are engaged with each other by screwing, so that the second member itself can generate linear motion along with the rotational motion of the second member.

[0020] According to the third aspect of the present invention, the threaded portion of the first member faces the lubricant reservoir of the second member, so that the threaded connection portion of the two members can be lubricated, and the threaded connection rotation of the second member can be performed smoothly.

[0021] According to the fourth aspect of the present invention, by fixing the first member to the housing that accommodates the motion conversion mechanism including the first member, the rotation and linear motion of the first member can be reliably prevented.

[0022] According to the fifth feature of the present invention, a highly quiet electric parking brake device can be provided.

[0023] According to the sixth feature of the present invention, the second member is connected to the parking brake mechanism via the transmission member, and a bearing is provided between the second member and the transmission member to allow relative rotation of the two members, thereby preventing the transmission of rotational motion from the second member to the transmission member.

[0024] According to the seventh aspect of the present invention, by providing the first member with the hollow portion through which the transmission member is inserted, the transmission member can be connected to the second member without being hindered by the first member.

[0025] According to the eighth feature of the present invention, when the parking brake mechanism is in a braking state by the traction of the transmission member realized by the linear motion of the second member, the elastic member between the second member and the transmission member accumulates rebound force, thereby suppressing the loosening of the parking brake mechanism and the loosening of the transmission member, and stabilizing the braking state of the parking brake mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a longitudinal sectional view showing the electric actuator according to the first embodiment of the present invention in a non-operating state.

[0027] Figure 2 It is a longitudinal sectional view showing the electric actuator in a working state.

[0028] Figure 3 This is an exploded perspective view of the electric actuator.

[0029] Figure 4 FIG. 2 shows a second embodiment of the present invention and is a longitudinal sectional view of a main part of an electric actuator in an operating state.

[0030] Figure 5 It is a longitudinal sectional view showing the main parts of the electric actuator in a non-operating state. DETAILED DESCRIPTION

[0031] First, refer to the attached Figure 1 to Figure 3 A first embodiment of the present invention will be described.

[0032] exist Figure 1 and Figure 3 In FIG. 1 , the electric actuator A is composed of an actuator case 10 and an actuator mechanism 11 housed in the actuator case 10. In the electric actuator A, the extending direction from the actuator case 10 to an output cable 14 described later is defined as the front, and the opposite direction is defined as the rear.

[0033] The actuator housing 10 includes a cylindrical motor housing portion 10a, a cylindrical output housing portion 10b arranged parallel to the motor housing portion 10a, and a gear housing portion 10c connecting the rear end of the motor housing portion 10a and the middle portion of the output housing portion. The front end of the motor housing portion 10a forms a detachable cover 10a'.

[0034] The actuator housing 10 is divided into a housing body 10A of the front half including the main part of the motor housing 10a and a housing cover 10B of the rear half so as to enable assembly and disassembly of the actuator mechanism 11. The housing body 10A and the housing cover 10B are made of synthetic resin.

[0035] The actuator mechanism 11 includes a motor 12 housed in a motor housing portion 10a, an output cable 14 extending to the outside through a cable outlet 13 passing through a front end wall of an output housing portion 10b, a reduction gear set 20 housed in a gear housing portion 10c and reducing the speed of the rotational driving force of a rotor shaft 17 of the motor 12 from a pinion gear 18 to an annular final gear 19, and a motion conversion mechanism 21 housed in the output housing portion 10b and converting the rotational motion of the final gear 19 into a linear motion and transmitting it to the output cable 14.

[0036] The final gear 19 is rotatably supported by a cylindrical support shaft 23 integral with the output housing portion 10b and is housed in an arc-shaped gear housing 24 of the output housing portion 10b so that axial movement thereof is restricted.

[0037] The motion conversion mechanism 21 includes: an external threaded cylindrical shaft 25 having an anchoring flange 25b fixed to the front end wall of the output housing portion 10b by molding or the like, and having an external thread 25a formed on the outer circumference thereof; an internal threaded cylindrical shaft 26 having an internal thread 26a formed on the inner circumference thereof to be threadedly engaged with the external thread 25a; and the final gear 19 is slidably engaged with the outer circumference of the internal threaded cylindrical shaft 26 via a spline 27. The hollow portion 25c of the external threaded cylindrical shaft 25 is connected to the cable outlet 13.

[0038] In this way, the externally threaded cylindrical shaft 25 is fixed to the output housing portion 10b, and the final gear 19 integrally drives the internally threaded cylindrical shaft 26 to rotate, while allowing the internally threaded cylindrical shaft 26 to move axially. Moreover, the internally threaded cylindrical shaft 26 changes the threaded engagement position with the externally threaded cylindrical shaft 25 through the rotation, thereby having a certain stroke in the axial direction in the output housing portion 10b, that is, it can be in the non-working position (close to the anchor flange 25b) Figure 1 state) and the working position farthest from the anchor flange 25b ( Figure 2 The externally threaded cylindrical shaft 25 and the internally threaded cylindrical shaft 26 which are threadedly coupled to each other are in an irreversible relationship in which relative rotation does not occur due to a thrust load.

[0039] The external thread 25a of the externally threaded cylindrical shaft 25 is formed over the entire length of the externally threaded cylindrical shaft 25. On the other hand, the internal thread 26a of the internally threaded cylindrical shaft 26 is formed on a portion of the front end side of the internally threaded cylindrical shaft 26. On the other inner circumferential surface of the internally threaded cylindrical shaft 26, a grease reservoir 28 is formed surrounding the internal thread 26a, and the grease reservoir 28 stores grease.

[0040] The output cable 14 is connected to the internally threaded cylindrical shaft 26 as follows.

[0041] That is, the output cable 14 is inserted through the cable outlet 13 of the actuator housing 10 and the hollow portion 25c of the male threaded cylindrical shaft 25. A flange-shaped projection of the cable inner terminal 14a is fixed to the rear end of the output cable 14 by brazing or the like.

[0042] On the other hand, an annular recess 30 having an annular segment 30a is provided on the inner periphery of the rear end portion of the internal threaded cylindrical shaft 26, and the annular support plate 31 abutting against the annular segment 30a, a bearing plate 32 supported by the support plate 31, and the cable inner terminal 14a supported by the bearing plate 32 in a rotatable and slidable manner are accommodated in the annular recess 30, and a spring ring 33 that prevents the cable inner terminal 14a from being separated from the annular recess 30 is locked on the inner peripheral surface of the opening of the annular recess 30. Grease is applied around the bearing plate 32. In addition, the bearing plate 32 can play a role in not transmitting the rotation of the support plate 31 to the cable inner terminal 14a.

[0043] A bellows-type dust boot 34 is installed between the outer peripheral portion of the cable outlet 13 of the actuator housing 10 and the middle portion of the output cable 14 so as to cover the output cable 14 therebetween.

[0044] A cable external terminal 14b is fixedly mounted on the outer end of the output cable 14, and the cable external terminal 14b is connected to a parking brake mechanism P in a known drum brake B. The electric parking brake device of the present invention is composed of the electric actuator A and the parking brake mechanism P.

[0045] Next, the operation of the first embodiment will be described.

[0046] When the parking brake mechanism P is in the non-braking state, Figure 1 As shown, in the electric actuator A, the internal threaded cylindrical shaft 26 is held in a non-operating position close to the anchoring flange 25b of the external threaded cylindrical shaft 25. However, in the example shown in the figure, the final gear 19 is rotated in the counterclockwise direction / clockwise direction by the forward / reverse rotation of the motor 12, and the threaded external thread 25a and the internal thread 26a are formed into a right-hand spiral pattern.

[0047] At present, in order to operate the parking brake mechanism P, when the motor 12 is driven in the forward direction, the rotation of the motor is decelerated by the reduction gear set 20 and transmitted to the final gear 19, driving the final gear 19 to rotate in the counterclockwise direction. Then, the counterclockwise rotation of the final gear 19 is transmitted to the internal threaded cylindrical shaft 26 via the spline 27, so that the internal threaded cylindrical shaft 26 rotates counterclockwise relative to the external threaded cylindrical shaft 25 fixed to the actuator housing 10, thereby sliding on the spline 27 of the final gear 19 and moving linearly in the rear direction, that is, in the direction away from the anchoring flange 25b of the external threaded cylindrical shaft 25, and the thrust is transmitted to the cable inner terminal 14a via the support plate 31 and the bearing plate 32, pulling the output cable 14 to Figure 2 working position, so that the parking brake mechanism P is in a working state, i.e. a braking state.

[0048] At this time, the inner cable terminal 14a is supported on the support plate 31 via the bearing plate 32. Therefore, even if the support plate 31 rotates together with the internal threaded cylindrical shaft 26, the rotation is blocked by the bearing plate 32. Therefore, the inner cable terminal 14a does not rotate. In this way, the output cable 14 can be prevented from being twisted.

[0049] When the parking brake mechanism P is in the braking state, the predetermined load state (e.g., current value) of the motor 12 is detected by a sensor (not shown) to stop the forward rotation of the motor 12. Then, the working state of the parking brake mechanism P is maintained by the irreversible transmission function of the external threaded cylindrical shaft 25 and the internal threaded cylindrical shaft 26 that are threadedly coupled to each other.

[0050] Next, if the motor 12 is reversed, the above-mentioned action is performed in the opposite direction, and the internally threaded cylindrical shaft 26 retreats to the initial non-operating position, so that the parking brake mechanism P can be restored to the non-braking state.

[0051] However, as described above, the external threaded cylindrical shaft 25 is fixed to the actuator housing 10 via the anchor flange 25b, so that in the motion conversion mechanism 21, the movable part that causes the knocking sound when the motor 12 rotates forward / reverse is only the sliding fitting part formed by the spline 27 between the final gear 19 and the internal threaded cylindrical shaft 26. In addition, the spline 27 is provided on the outer peripheral surface of the internal threaded cylindrical shaft 26 with the largest diameter in the motion conversion mechanism 21, so the clearance in the rotation direction between the final gear 19 and the internal threaded cylindrical shaft 26 caused by the sliding clearance of the spline 27 is small. Therefore, the knocking sound caused by the clearance becomes extremely small. In this way, the quietness of the electric actuator A can be achieved.

[0052] And, in Figure 1 In the non-working state of the electric actuator A shown, the grease reservoir 28 in the internal threaded cylindrical shaft 26 surrounds the external thread 25a of the external threaded cylindrical shaft 25, so that the external thread 25a is in a lubricated state. Therefore, as the internal threaded cylindrical shaft 26 rotates, the entire threaded connection between the external thread 25a and the internal thread 26a can be lubricated, allowing the internal threaded cylindrical shaft 26 to smoothly rotate in thread connection.

[0053] Furthermore, the output cable 14 passes through the hollow portion 25c of the externally threaded cylindrical shaft 25 and connects the cable inner terminal 14a fixedly installed at the inner end of the output cable 14 to the inner end of the internally threaded cylindrical shaft 26, so that the output cable 14 can be connected to the internally threaded cylindrical shaft 26 without being hindered by the externally threaded cylindrical shaft 25, thereby improving space utilization.

[0054] Next, through Figure 4 and Figure 5 A second embodiment of the present invention will be described.

[0055] The annular recess 30 at the rear end of the internally threaded cylindrical shaft 26 accommodates the first support plate 31, the disc spring 37 group, the second support plate 36, the bearing plate 32 and the inner cable terminal 14a in order from the front, and the spring ring 33 that prevents these structures from escaping from the annular recess 30 is locked at the rear end of the annular recess 30. The disc spring 37 group is formed by alternately switching the directions of the conical surfaces of the plurality of disc springs 37 and overlapping the plurality of disc springs 37.

[0056] The other structures are the same as those in the first embodiment. Figure 4 and Figure 5 In the present invention, the same reference numerals are used for portions corresponding to the configuration of the first embodiment, and description thereof will be omitted.

[0057] And, if Figure 4 As shown, first, in order to make the parking brake mechanism P ( Figure 1 ) is in braking state and through motor 12 ( Figure 1) is driven toward the working position (towards arrow Y1) by the positive rotation of the internal threaded cylindrical shaft 26, if the traction force applied to the output cable 14 exceeds the set load of the disc spring 37 group, the disc spring 37 group is gradually compressed between the first and second support plates 31 and 36, and when the internal threaded cylindrical shaft 26 reaches the working position where the parking brake mechanism P is in a braking state, the disc spring 37 group is fully compressed and a predetermined rebound force is accumulated. Therefore, when the drive motor 12 is stopped, if the parking brake mechanism P is loosened and the output cable 14 is relaxed, the loosening and relaxation will be suppressed by the rebound force of the disc spring 37 group, which can ensure that the parking brake mechanism P is in a stable braking state.

[0058] Next, if Figure 5 As shown, in the process of driving the internal threaded cylindrical shaft 26 toward the non-operating position (towards arrow Y2) by the reverse rotation of the motor 12 in order to restore the parking brake mechanism P from the operating state to the non-operating state, the parking brake mechanism P is restored to the non-operating state. When the disc spring 37 group just becomes free, the cable inner terminal 14a contacts the circlip 33, causing the internal threaded cylindrical shaft 26 to retreat further. Due to the retreat of the internal threaded cylindrical shaft 26, the front end surface of the external threaded cylindrical shaft 25 that is pressed by the first support plate 31 is compressed between the first support plate 31 and the circlip 33 by its reaction force. When the load of the motor 12 accompanied by the generation of the compression reaction force reaches a predetermined value (current value), the sensor not shown in the figure detects the predetermined value as a stop signal to stop the reverse rotation of the motor 12. Then, the above-mentioned compressive load acting on the disc spring 37 group acts on the output cable 14, which can eliminate the clearance from the output cable 14.

[0059] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various design changes can be made without departing from this invention described in a patent claim.

[0060] For example, the electric actuator A can be used to operate a parking brake mechanism in a disc brake. Furthermore, the disc spring 37 group can be replaced with a compression coil spring.

[0061] This application claims priority based on Japanese patent application No. 2022-166512, filed on October 17, 2022. This application refers to and cites all the disclosed contents of Japanese patent application No. 2022-166512, filed on October 17, 2022, including the specification, claims, drawings, and abstract.

[0062] Description of Reference Numerals

[0063] A. Electric actuator;

[0064] P, parking brake mechanism;

[0065] 10. Actuator housing;

[0066] 12. Electric drive source (motor);

[0067] 14. Transmission components (output cables);

[0068] 21. Motion conversion mechanism;

[0069] 25. The first component (externally threaded cylindrical shaft);

[0070] 25a, external thread;

[0071] 26. The second component (internal threaded cylindrical shaft);

[0072] 26a, internal thread;

[0073] 28. Lubricating oil storage part (grease storage part);

[0074] 32. Bearing (bearing plate);

[0075] 37. Elastic component (disc spring).

Claims

1. An electric actuator, characterized in that: The electric actuator has: an electric drive source capable of generating a rotational motion as a driving force; a motion conversion mechanism that converts the rotational motion into a linear motion; The motion conversion mechanism has: a first member which is prevented from rotational and linear motion; A second component engaged with the first component and generating a linear motion by rotating relative to the first component; The second member is rotationally driven by the driving force of the electric driving source.

2. The electric actuator according to claim 1, characterized in that: The first component and the second component are engaged with each other by screwing.

3. The electric actuator according to claim 2, 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, characterized in that: The first member is fixed to an actuator housing that accommodates the motion conversion mechanism.

5. An electric parking brake device, characterized in that: The electric parking brake device includes a parking brake mechanism that is in a braking state by the operation of an electric actuator. The electric actuator comprises: an electric drive source that generates a rotational motion as a driving force; a motion conversion mechanism that converts the rotational motion into a linear motion; The motion conversion mechanism comprises: a first component which is prevented from rotating and linear motion; and a second component which generates linear motion by rotating relative to the first component. The parking brake mechanism is activated by the second member being driven to rotate by the driving force of the electric drive source.

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

7. The electric parking brake device according to claim 6, characterized in that: The first member is provided with a hollow portion through which the transmission member is inserted.

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

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