Rotation control device

Abstract

The shock-absorbing components of the rotation control device maintain a high level of noise reduction over a long period of time. [Solution] The device comprises an electromagnet 15, an armature 13 attracted to the electromagnet 15, a release spring 10 that returns the armature 13 attracted to the electromagnet 15, a stopper part 11 that receives the armature 13 moved by the spring force of the release spring 10, and a case 4 that houses the electromagnet 15 and the stopper part 11. The state of rotation control switches according to the movement of the armature 13 by the electromagnet 15 or the release spring 10. Inside the case 4, an ethylene propylene diene rubber (EPDM) shock-absorbing member 18 is provided to reduce the collision noise of the armature 13. The lubricant that lubricates the movable parts housed in the case 4 is a grease using a polyglycol base oil.

Description

Technical Field

[0001] This invention relates to a rotation control device such as a clutch or brake that controls rotation.

Background Art

[0002] Conventionally, as a device that controls rotation using electromagnetic force, an electromagnetic clutch that transmits and blocks rotation and an electromagnetic brake that brakes and holds rotation have been used. Generally, an electromagnetic clutch or electromagnetic brake houses an electromagnetic mechanism that switches the rotation control state according to the switching between the excited and non-excited states in a case. As the electromagnetic mechanism, it includes an electromagnet, an armature attracted by the electromagnet, a separation spring that returns the armature attracted by the electromagnet, and a stopper portion that receives the armature moved by the spring force of the separation spring, and there is a structure in which the rotation control state is switched according to the movement of the armature by the electromagnet or the separation spring.

[0003] For example, there is one that includes an inner member, an outer member that surrounds the inner member, a clutch mechanism that transmits and blocks rotational torque between the inner member and the outer member, and a case that surrounds the outer member and houses the clutch mechanism. The clutch mechanism includes an engaging element disposed between the outer member and the inner member, a retainer that holds the engaging element and is disposed so as to be movable in the circumferential direction between an engaging position where it engages with the outer member and the inner member and a release position where the engagement is released, an electromagnet attached to the case, a rotor axially opposed to the electromagnet, an armature attracted to the rotor by the electromagnet, and a stopper portion that receives the armature separated from the rotor by the spring force, and there is a rotation control device provided so as to switch the transmission and blocking of rotational torque according to the axial movement of the armature by the electromagnet or the separation spring (for example, Patent Documents 1 and 2).

[0004] An armature, which is moved by an electromagnet or separation spring, needs to be stopped at a predetermined position by a stopper or the like, but it is undesirable for the armature to make a collision noise at this time. The generation of collision noise is a particular problem in the field of automobiles in recent years, where high levels of quietness are required (for example, steer-by-wire steering systems). In order to prevent such collision noise and improve the quietness of the rotation control device, the rotation control device of Patent Document 1 has an impact absorbing member that reduces the armature collision noise provided inside the case. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-138999 [Patent Document 2] Patent No. 7330794 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1 proposes using a rubber molded body or a resin molded body as a shock-absorbing member in the rotation control device, but the specific material names have not been considered.

[0007] While impact-absorbing components formed from rubber or resin molded materials offer superior noise reduction compared to those using metal springs, they are susceptible to deterioration and deformation due to heat and the surrounding chemical environment. Therefore, there are concerns that their long-term stability in noise reduction may be compromised depending on the material selection and environmental conditions. In recent years, with the electrification of vehicles, quietness has become increasingly important, making it crucial to maintain the long-term effectiveness of collision noise suppression measures in rotational control systems.

[0008] In light of the above-mentioned background, the problem that this invention aims to solve is to stably maintain a high noise reduction effect by the shock-absorbing member of the rotation control device over a long period of time. [Means for solving the problem]

[0009] To achieve the above objectives, this invention adopts a rotation control device configuration 1 comprising an electromagnet, an armature attracted to the electromagnet, a separation spring for returning the armature attracted to the electromagnet, a stopper portion for receiving the armature moved by the spring force of the separation spring, a case housing the electromagnet and the stopper portion, and an impact absorbing member provided inside the case for reducing the collision noise of the armature, wherein the rotation control state switches in accordance with the movement of the armature by the electromagnet or the separation spring, the impact absorbing member being made of ethylene propylene diene rubber (EPDM), and the lubricant for lubricating the movable part housed in the case being a grease using a polyglycol-based oil.

[0010] According to the above configuration 1, a shock-absorbing member made of ethylene propylene diene rubber (EPDM), which has a low compression set, is used as a rubber shock-absorbing member with a high sound-dampening effect. Furthermore, the movable parts inside the case are lubricated with a grease using a polyglycol-based oil that has low chemical aggressiveness towards the EPDM. This makes it possible to stably maintain the high sound-dampening effect of the shock-absorbing member of the rotation control device over a long period of time.

[0011] In the above configuration 1, a configuration 2 can be adopted, which comprises an inner member, an outer member surrounding the inner member, and a clutch mechanism for transmitting and interrupting rotational torque between the inner member and the outer member, wherein the clutch mechanism has an engagement surface formed on the inner circumference side of the outer member, an engagement surface formed on the inner member, an engaging element disposed between the engagement surface of the outer member and the engagement surface of the inner member, and a retainer that is circumferentially movable between an engagement position that holds the engaging element and engages the outer member and the inner member, and a release position that disengages the engagement, and is provided to switch between transmitting and interrupting the rotational torque in accordance with the axial movement of the armature by the electromagnet or the separation spring.

[0012] According to the above configuration 2, rotational torque is transmitted by the engagement of the engaging element with the inner member and the outer member, making it possible to create a rotation control device with excellent capacity.

[0013] In the above configuration 2, configuration 3 can be adopted in which the surface roughness (Ra) of the engagement surface of the outer member and the surface roughness (Ra) of the engagement surface of the inner member are each 0.1 or more and 3.2 or less.

[0014] According to the above configuration 3, when the clutch mechanism is engaged, the engaging element is prevented from becoming slippery due to the oil film on the respective engagement surfaces of the outer and inner members, and the engaged state of the clutch mechanism can be stably maintained.

[0015] Configuration 4 can be adopted, which is a steer-by-wire system equipped with a rotation control device relating to any one of the above configurations 1 to 3. [Effects of the Invention]

[0016] As described above, by adopting the above configuration 1, this invention makes it possible to stably maintain a high noise reduction effect by the shock-absorbing member of the rotation control device over a long period of time. [Brief explanation of the drawing]

[0017] [Figure 1] Cross-sectional view showing a rotation control device according to the first embodiment of this invention. [Figure 2] Cross-sectional view along line II-II in Figure 1 [Figure 3] Figure 1 shows an exploded perspective view of the retainer, stopper, and armature. [Figure 4] Cross-sectional view along line IV-IV in Figure 2 [Figure 5] Figure 1 shows a magnified view of the area near the armature. [Figure 6] Figure 2 shows the retainer in the state where it has moved from the engaged position to the disengaged position. [Figure 7] A rotation control device according to a second embodiment of this invention is shown in relation to Figure 5. [Figure 8] Figure showing the rotation control device according to the third embodiment of the present invention corresponding to FIG. 5 [Figure 9] Figure showing the rotation control device according to the fourth embodiment of the present invention corresponding to FIG. 5 [Figure 10] Figure showing the rotation control device according to the fifth embodiment of the present invention corresponding to FIG. 5 [Figure 11] Figure showing the rotation control device according to the sixth embodiment of the present invention corresponding to FIG. 5 [Figure 12] Schematic diagram showing a vehicle steering device incorporating the rotation control device of FIG. 1

Embodiments for Carrying Out the Invention

[0018] FIG. 1 shows a rotation control device 1 according to a first embodiment as an example of the present invention. This rotation control device 1 includes an inner member 2, an outer member 3 surrounding the inner member 2, a clutch mechanism that transmits and interrupts rotational torque between the inner member 2 and the outer member 3, and a case 4 that surrounds the outer member 3 and houses the clutch mechanism.

[0019] Here, the direction along the central axis of the relative rotation of the inner member 2 and the outer member 3 is referred to as the "axial direction", and the direction orthogonal to the central axis is referred to as the "radial direction". Also, the circumferential direction centered on the central axis is referred to as the "circumferential direction".

[0020] The case 4 has a cylindrical shape with both ends open. The inner member 2 and the outer member 3 each have one end housed in the case 4 and the other end protruding from the case 4. The inner member 2 has an inner ring portion 2a provided in the portion housed in the case 4. The outer member 3 has an outer ring portion 3a provided in the portion housed in the case 4. A plurality of engaging elements 5a, 5b are arranged between the inner circumference of the outer ring portion 3a and the inner ring portion 2a. Rollers are adopted as the engaging elements 5a, 5b. A retainer 6 for holding these engaging elements 5a, 5b is arranged around the inner ring portion 2a.

[0021] Case 4 consists of a cylindrical case body 4a and a lid 4b attached to the case body 4a. A radially outward-facing flange portion 4c is integrally formed on the case body 4a without any seams. The lid 4b is fixed to the flange portion 4c with bolts (not shown). The case body 4a is made of, for example, a non-magnetic metal (aluminum alloy, copper alloy, etc.). On the other hand, the lid 4b is made of, for example, a magnetic metal (iron, silicon steel, etc.).

[0022] The lid 4b has an annular plate portion 4d that abuts axially with the flange portion 4c of the case body 4a, a cylindrical portion 4e that extends axially from the annular plate portion 4d along the inner circumference of the case body 4a, and a cylindrical opening portion 4f that extends from the annular plate portion 4d on the side opposite to the case body 4a.

[0023] The inner member 2 is an axis to which rotation is input from the outside. The outer member 3 is an axis to which rotation is output to the outside. Other machines in which this rotation control device 1 is incorporated include, for example, steering devices in vehicles, ships, or construction machinery.

[0024] The inner member 2 is rotatably supported by a rolling bearing 7. The rolling bearing 7 is positioned between the inner circumference of the cylindrical opening portion 4f of the cover 4b and the inner member 2. The inner member 2 is formed as a seamless, integrated member including the inner ring portion 2a. The inner member 2 may be divided into two parts, the shaft body and the inner ring, and the shaft end may be formed by joining the shaft body and the inner ring using a serration fitting or the like so that they rotate together. The inner member 2 is formed of, for example, a magnetic material (iron, silicon steel, etc.).

[0025] The outer member 3 is formed as a seamless, integrated member including the outer ring portion 3a. The outer member 3 is arranged in a single line coaxially with the inner member 2. The outer member 3 may be divided into two parts, the shaft body and the outer ring, and the shaft body and the outer ring may be joined by a serration fitting or the like to form the outer ring portion so that they rotate together. The outer member 3 is rotatably supported by a rolling bearing 8. The rolling bearing 8 is positioned between the inner circumference of the case body 4a and the outer member 3. An intermediate bearing 9 is incorporated between the inner circumference of the outer ring portion 3a and the inner ring portion 2a, connecting the outer ring portion 3a and the inner ring portion 2a so that they can rotate relative to each other.

[0026] As shown in Figure 2, the outer circumference of the inner ring portion 2a is provided with a plurality of engagement surfaces 2b at equal intervals in the circumferential direction. The engagement surfaces 2b consist of a front cam surface portion 2c and a rear cam surface portion 2d positioned behind the front cam surface portion 2c in the forward rotation direction of the inner ring portion 2a. On the inner circumference of the outer ring portion 3a, an engagement surface 3b is provided in a cylindrical shape, facing radially from the engagement surfaces 2b.

[0027] Between the engaging surface 2b and the engaging surface 3b, a pair of engaging elements 5a and 5b are incorporated, facing each other in the circumferential direction with a separation spring 10 in between. Of this pair of engaging elements 5a and 5b, the front engaging element 5a in the forward rotation direction is positioned between the front cam surface 2c and the engaging surface 3b, and the rear engaging element 5b in the forward rotation direction is positioned between the rear cam surface 2d and the engaging surface 3b. The separation spring 10 presses each of the engaging elements 5a and 5b in a direction that widens the distance between them.

[0028] A wedge-shaped space is formed between the engaging surface 2b and the engaging surface 3b, which gradually narrows from the circumferential center toward both ends in the circumferential direction. That is, the front cam surface portion 2c is formed such that the radial distance between it and the engaging surface 3b gradually decreases from the position of the engaging element 5a toward the forward direction of rotation. The rear cam surface portion 2d is formed such that the radial distance between it and the engaging surface 3b gradually decreases from the position of the engaging element 5b toward the rear in the forward direction of rotation.

[0029] Figure 2 shows an example where the front cam surface 2c and the rear cam surface 2d are formed as separate planes inclined in opposite directions. However, it is also possible to form the front and rear cam surfaces on the same plane, with the front portion of a single plane in the forward rotation direction being the front cam surface and the rear portion being the rear cam surface. Furthermore, while the front and rear cam surfaces can be curved, forming them as flat surfaces as shown in the figure can reduce processing costs.

[0030] As shown in Figures 2 and 3, the retainer 6 consists of a first divided retainer 6a that supports one of a pair of engaging elements 5a and 5b, which face each other in the circumferential direction with the separation spring 10 in between, against the biasing force of the separation spring 10, and a second divided retainer 6b that supports the other engaging element 5b in the circumferential direction against the biasing force of the separation spring 10. The first divided retainer 6a and the second divided retainer 6b are supported so as to be rotatable relative to each other, and the pair of engaging elements 5a and 5b are individually supported such that the distance between them changes according to their relative rotation.

[0031] As shown in Figure 3, the first split retainer 6a has a plurality of first columnar portions 6c arranged at intervals in the circumferential direction, a first annular portion 6d connecting one end of these first columnar portions 6c in the axial direction, and a first annular portion 6e connecting the other end of the first columnar portions 6c in the axial direction. The second split retainer 6b has a plurality of second columnar portions 6f arranged at intervals in the circumferential direction, and a second annular portion 6g connecting one end of these second columnar portions 6f in the axial direction.

[0032] As shown in Figure 2, the first column portion 6c and the second column portion 6f are arranged alternately in the circumferential direction between the outer ring portion 3a and the inner ring portion 2a. Furthermore, the first column portion 6c and the second column portion 6f face each other in the circumferential direction with a pair of engaging elements 5a and 5b in between. That is, the first column portion 6c and the second column portion 6f are inserted between the inner circumference of the outer ring portion 3a and the outer circumference of the inner ring portion 2a, sandwiching the pair of engaging elements 5a and 5b, which face each other in the circumferential direction with the separation spring 10 in between, from both sides in the circumferential direction.

[0033] As shown in Figures 1 and 4, the first annular portion 6d is rotatably supported on the outer circumference of the inner ring portion 2a. The second annular portion 6g, as shown in Figures 1 and 5, has an inner diameter larger than the outer diameter of the first annular portion 6d and is fitted onto the outer circumference of the first annular portion 6d. The second annular portion 6g is rotatably supported on the outer circumference of the first annular portion 6d. Here, the first split retainer 6a and the second split retainer 6b shown in Figure 1 are each rotatable with respect to the inner ring portion 2a. As a result, the first split retainer 6a and the second split retainer 6b are circumferentially movable between an engagement position (see Figure 2) in which the pair of engaging elements 5a and 5b are engaged between the engagement surface 2b and the engagement surface 3b by widening the distance between the pair of engaging elements 5a and 5b, and an engagement release position (see Figure 6) in which the engagement elements 5a and 5b are released from between the engagement surface 2b and the engagement surface 3b by narrowing the distance between the pair of engaging elements 5a and 5b.

[0034] As shown in Figure 3, the first columnar portion 6c is continuous with the outer circumference of the first annular portion 6d. Multiple notches 6h are formed on the inner circumference of the second annular portion 6g at intervals in the circumferential direction to avoid interference with the first columnar portion 6c. The second columnar portion 6f protrudes axially from the side surface of the second annular portion 6g.

[0035] As shown in Figure 1, a stopper portion 11 is fixed to the outer circumference of the inner ring portion 2a, adjacent in the axial direction to the first annular portion 6d and the second annular portion 6g. The stopper portion 11 supports the sides of the first annular portion 6d and the second annular portion 6g so as to restrict axial movement of the first annular portion 6d and the second annular portion 6g away from the engaging elements 5a and 5b. The first annular portion 6d and the second annular portion 6g are in circumferential sliding contact with the stopper portion 11.

[0036] As shown in Figure 4, a spring retainer 12 is mounted on the outer circumference of the inner ring portion 2a to hold the separation spring 10 in place. The spring retainer 12 has an annular portion 12a that fits onto the outer circumference of the inner ring portion 2a, and a spring retaining piece 12b that extends axially from the annular portion 12a. The annular portion 12a is fixed to the inner ring portion 2a by fitting onto its outer circumference with an overlap. The spring retaining piece 12b is positioned so as to face the outer circumference of the inner ring portion 2a radially, with the separation spring 10 in between. The spring retaining piece 12b has a recess 12c formed therein for accommodating the separation spring 10. The separation spring 10 is a compression coil spring. The spring retaining piece 12b holds the separation spring 10 in the recess 12c, thereby positioning the separation spring 10 so that it presses against the center of the engaging elements 5a and 5b.

[0037] As shown in Figure 1, the case 4 incorporates an armature 13, a rotor 14 positioned axially opposite to the armature 13, an electromagnet 15 that attracts the armature 13 to the rotor 14 when energized, and a motion conversion mechanism 16 that converts the movement of the armature 13 axially toward the rotor 14 into a movement of the retainer 6 (first divided retainer 6a and second divided retainer 6b) circumferentially from an engaged position (see Figure 2) to an unengaged position (see Figure 6).

[0038] The armature 13 is slidably fitted onto the outer circumference of a ring 17, which is fitted and fixed to the outer circumference of the inner ring portion 2a. The armature 13 is supported on the outer circumference of this ring 17 so as to be rotatable and axially movable relative to the inner ring portion 2a.

[0039] The rotor 14 is fixed to the outer circumference of the inner member 2 so as not to move relative to the inner member 2 in either the axial or circumferential direction. The rotor 14 is formed in an L-shape in cross-section, having an annular plate portion 14a positioned between the axially opposing surfaces of the electromagnet 15 and the armature 13, and a cylindrical portion 14b facing the radially inward side of the electromagnet 15. Both the rotor 14 and the armature 13 are made of magnetic material (iron, silicon steel, etc.).

[0040] The electromagnet 15 has a field core 15a made of a magnetic material and a solenoid coil 15b wound around the field core 15a. The electromagnet 15 is assembled such that its outer circumference fits into the cylindrical portion 4e of the cover 4b, and its axial end face abuts against the annular plate portion 4d of the cover 4b. By energizing the solenoid coil 15b, the electromagnet 15 forms a magnetic path passing through the field core 15a, rotor 14, cylindrical portion 4e, and armature 13, causing the armature 13 to be attracted to the rotor 14.

[0041] The stopper section 11 is positioned axially opposite the armature 13 on the side opposite the rotor 14, so as to catch the armature 13 in the axial direction when the armature 13 moves axially away from the rotor 14 due to the de-energization of the electromagnet 15.

[0042] As shown in Figure 5, the armature 13 has an outer diameter larger than the outer diameter of the annular plate portion 14a of the rotor 14. The cylindrical portion 4e of the cover 4b (see Figure 1) is positioned axially opposite to the portion of the armature 13 that has a larger diameter than the annular plate portion 14a. An impact absorbing member 18 is attached to the cylindrical portion 4e at the position opposite the armature 13 to reduce the impact noise of the armature 13.

[0043] As shown in Figure 3, the motion conversion mechanism 16 consists of a wedge member 16a fixed to the armature 13 so as to move axially together with the armature 13, and inclined sliding contact surfaces 16b and 16c formed on the retainer 6 (first divided retainer 6a and second divided retainer 6b). The inclined sliding contact surfaces 16b and 16c are surfaces that slide against the wedge member 16a.

[0044] Specifically, as shown in Figure 2, the first column portion 6c has a first inclined sliding contact surface 16b on the side opposite in the circumferential direction to the surface supporting the engaging element 5a, and the second column portion 6f also has a second inclined sliding contact surface 16c on the side opposite in the circumferential direction to the surface supporting the engaging element 5b. The first inclined sliding contact surface 16b and the second inclined sliding contact surface 16c are opposite each other in the circumferential direction.

[0045] As shown in Figure 3, the first inclined sliding surface 16b and the second inclined sliding surface 16c are both inclined surfaces that recede circumferentially along the axial direction on the side approaching the armature 13. The wedge member 16a is provided projecting axially from the armature 13 so as to be inserted between the circumferentially adjacent first column portion 6c and second column portion 6f. The wedge member 16a has a head portion 16d whose circumferential width gradually widens as it moves away from the armature 13 in the axial direction. The head portion 16d is in sliding contact with both the first inclined sliding surface 16b and the second inclined sliding surface 16c (see Figure 2). The stopper portion 11 has a through hole 16e through which the wedge member 16a is inserted in order to avoid interference with the wedge member 16a.

[0046] In this motion conversion mechanism 16, when the armature 13 shown in Figure 1 moves axially toward the electromagnet 15, the wedge member 16a shown in Figure 3 moves axially together with the armature 13, and the head 16d of the wedge member 16a presses the first inclined sliding contact surface 16b and the second inclined sliding contact surface 16c in the circumferential direction. As a result, as shown in Figure 6, the first column portion 6c and the second column portion 6f operate in a direction that reduces the distance between the pair of engaging elements 5a and 5b, causing the first divided retainer 6a and the second divided retainer 6b to move circumferentially.

[0047] An example of the operation of the above-described rotation control device 1 will be explained.

[0048] As shown in Figure 1, when the electromagnet 15 is de-energized, the rotation control device 1 enters a fastened state in which rotation is transmitted between the inner member 2 and the outer member 3. That is, when the electromagnet 15 is de-energized, the armature 13 is maintained axially separated from the rotor 14 by the spring force transmitted from the separation spring 10 (see Figure 2) through the engaging elements 5a, 5b and the motion conversion mechanism 16. At this time, as shown in Figure 2, the force exerted by the separation spring 10 on the pair of engaging elements 5a, 5b causes the front engaging element 5a in the forward rotation direction to engage between the engaging surface 3b of the outer ring portion 3a and the front cam surface portion 2c of the engaging surface 2b of the inner ring portion 2a, and the rear engaging element 5b in the forward rotation direction engages between the engaging surface 3b of the outer ring portion 3a and the rear cam surface portion 2d of the engaging surface 2b of the inner ring portion 2a. In this state, when the inner ring portion 2a rotates in the forward direction, that rotation is transmitted from the inner ring portion 2a to the outer ring portion 3a via the rear engaging element 5b in the forward direction. Also, when the inner ring portion 2a rotates in the reverse direction, that rotation is transmitted from the inner ring portion 2a to the outer ring portion 3a via the front engaging element 5a in the forward direction.

[0049] On the other hand, when the electromagnet 15 in Figure 1 is energized, the rotation control device 1 enters an idle state in which the transmission of rotation between the inner member 2 and the outer member 3 is interrupted. That is, when the electromagnet 15 is energized, the armature 13 is attracted to the rotor 14, and the axial movement of the armature 13 at this time is transmitted to the first divided retainer 6a and the second divided retainer 6b via the motion conversion mechanism 16, causing the first divided retainer 6a and the second divided retainer 6b to move in the circumferential direction. As a result of the circumferential movement of the first and second split retainers 6a and 6b, as shown in Figure 6, the first column 6c and the second column 6f press each of the pair of engaging elements 5a and 5b in a direction that narrows the distance between them. Consequently, the engagement standby state of the front engaging element 5a in the forward rotation direction (a state in which there is a small gap between the front engaging element 5a and the engagement surface 3b in the forward rotation direction, but when the inner ring 2a rotates in the reverse direction, the engaging element 5a immediately engages between the engagement surface 3b and the front cam surface 2c) is released, and the engagement standby state of the rear engaging element 5b in the forward rotation direction (a state in which there is a small gap between the rear engaging element 5b and the engagement surface 3b in the forward rotation direction, but when the inner ring 2a rotates in the forward direction, the engaging element 5b immediately engages between the engagement surface 3b and the rear cam surface 2d) is also released. In this state, even if rotation is input to the inner ring portion 2a, that rotation is not transmitted from the inner ring portion 2a to the outer ring portion 3a, and the inner ring portion 2a rotates freely.

[0050] When the energized electromagnet 15 is switched to an unenergized state, the spring force of the separation spring 10 (see Figure 2) is pushed to the engagement position by the engaging elements 5a and 5b, and at the same time, the motion conversion mechanism 16 converts this force into a force that pushes the armature 13 away from the rotor 14, causing the armature 13 to move axially away from the rotor 14.

[0051] Here, when the armature 13 is attracted to the rotor 14 by the magnetic force of the electromagnet 15, it is undesirable for a collision noise to occur between the armature 13 and the rotor 14. Such collision noise is a particular problem in recent years in applications where high levels of quietness are required (for example, as a backup clutch used in vehicle steering systems).

[0052] This rotation control device 1 has an impact absorbing member 18 (see Figures 1 and 5) inside the case 4 that reduces the impact noise of the armature 13, thus enabling excellent quietness. In other words, the impact when the armature 13 is attracted to the rotor 14 is absorbed by the impact absorbing member 18 attached to the cylindrical portion 4e of the lid 4b, making it possible to reduce the impact noise of the armature 13 with the rotor 14.

[0053] The shock-absorbing member 18 consists of an annular rubber molded body made of ethylene propylene diene rubber (EPDM). The EPDM shock-absorbing member 18 exhibits higher sound-absorbing performance compared to metal springs, and because the dimensional change (compression set) of the shock-absorbing member 18 is small even after repeated compression and release, it is possible to maintain the initial sound-absorbing performance over a long period of time.

[0054] Around the shock-absorbing member 18, there is a lubricant (not shown) that lubricates the movable parts such as the engaging elements 5a and 5b housed in the case 4 and the rolling elements in the rolling bearing 8. Since this rotation control device 1 is not connected to an external oil supply system, grease is used as the lubricant. If the components of the grease exhibit chemical aggressiveness towards the rubber, it can cause deterioration such as swelling, shrinking, or changes in hardness of the shock-absorbing member 18. To suppress the chemical aggressiveness of the lubricant towards the shock-absorbing member 18, the lubricant present in the case 4 consists of a polyglycol-based oil.

[0055] The inventors of this application conducted swelling tests on EPDM using grease with a polyglycol-based base oil and grease with an ester-based base oil commonly used in the clutch field. They measured the rate of change in the rubber height of the EPDM during these swelling tests. In the EPDM swelling test conducted with grease using an ester-based base oil, the rate of change in the rubber height of the EPDM was approximately 111% to 116%, while in the EPDM swelling test conducted with grease using a polyglycol-based base oil, the rate of change in the rubber height of the EPDM was approximately 100% to 102%. Therefore, it can be seen that the chemical aggressiveness of grease using a polyglycol-based base oil that degrades EPDM is significantly lower than that of grease using an ester-based base oil.

[0056] As described above, this rotation control device 1 comprises an electromagnet 15, an armature 13 attracted to the electromagnet 15, a release spring 10 that returns the armature 13 attracted to the electromagnet 15, a stopper part 11 that receives the armature 13 as it is moved by the spring force of the release spring 10, a case 4 that houses the electromagnet 15 and the stopper part 11, and an impact absorbing member 18 provided inside the case 4 to reduce the collision noise of the armature 13, and the state of rotation control is switched according to the movement of the armature 13 by the electromagnet 15 or the release spring 10.

[0057] In particular, this rotation control device 1 has a shock-absorbing member 18 made of ethylene propylene diene rubber (EPDM), and the lubricant that lubricates the movable parts (engineers 5a, 5b, etc.) housed in the case 4 is a grease using a polyglycol-based oil, which allows the shock-absorbing member 18 to maintain a high noise-reducing effect stably over a long period of time.

[0058] Furthermore, the rotation control device 1 comprises an inner member 2, an outer member 3 surrounding the inner member 2, and a clutch mechanism that transmits and disconnects rotational torque between the inner member 2 and the outer member 3. The clutch mechanism has an engagement surface 3b formed on the inner circumference of the outer member 3, an engagement surface 2b formed on the inner member 2, engaging elements 5a and 5b positioned between the engagement surface 3b of the outer member 3 and the engagement surface 2b of the inner member 2, and a retainer 6 that is circumferentially movable between an engagement position that holds the engaging elements 5a and 5b and engages the outer member 3 and the inner member 2, and a release position that disengages the engagement. The clutch mechanism is configured to switch between transmitting and disconnecting the rotational torque in accordance with the axial movement of the armature 13 by an electromagnet 15 or a separation spring 10. Therefore, if one of the inner member 2 and the outer member 3 is connected to a drive shaft and the other to a driven shaft, the rotation control device 1 functions as a clutch. Furthermore, if one of the inner member 2 and the outer member 3 is connected to the rotating shaft and the other is fixed to the stationary system, this rotation control device 1 can function as a brake. Since the rotational torque of the inner member 2 and the outer member 3 is transmitted by the engagement of the engaging elements 5a and 5b with the inner member 2 and the outer member 3, a rotation control device 1 with excellent capacity (clutch capacity, brake capacity) can be made.

[0059] Furthermore, it is preferable to apply the lubricant only to necessary parts such as the engaging elements 5a and 5b and the engaging surfaces 2b and 3b, so as to minimize contact with the shock-absorbing member 18.

[0060] Here, grease using polyglycol-based oil has a higher viscosity than grease using ester-based oil, and therefore forms a relatively thick oil film at the sliding parts. For this reason, if grease using polyglycol-based oil is used as a lubricant between the engaging elements 5a and 5b and the engaging surfaces 2b and 3b of the clutch mechanism, the sliding parts between the engaging elements 5a and 5b and the engaging surfaces 2b and 3b will slide more easily compared to when grease using ester-based oil is used.

[0061] In this rotation control device 1, the surface roughness of the areas of the engaging surfaces 3b of the outer member 3 and 2b of the inner member 2 that can slide with the engaging surfaces 5a and 5b is set to an appropriate surface roughness, taking into consideration the oil film thickness formed between the engaging elements 5a and 5b and the engaging surfaces 2b and 3b using a polyglycol-based grease. This prevents the sliding parts of the engaging elements 5a and 5b and the engaging surfaces 2b and 3b from slipping in the circumferential direction when the clutch mechanism is engaged. As a guideline for this design, the equivalent mean square roughness of the inner and outer engaging surfaces 2b and 3b should be set to 1 to 1 / 3 times the oil film thickness. Here, "equivalent mean square roughness" is a value obtained from the mean square roughness (Rms) of the two contacting parts. In the case of the contact surfaces of the engaging elements 5a and 5b and the engaging surfaces 2b and 3b, if the mean square roughness of the engaging elements 5a and 5b is Rms(r) and the mean square roughness of the engaging surfaces 2b and 3b is Rms(c), the equivalent mean square roughness can be calculated using the following formula. Equivalent mean square roughness = √{Rms(r)^2 + Rms(c)^2}

[0062] Specifically, the surface roughness (Ra) of the engagement surface 3b of the outer member 3 and the surface roughness (Ra) of the engagement surface 2b of the inner member 2 are both between 0.1 and 3.2. This prevents the engaging elements 5a and 5b from becoming slippery due to an oil film on their respective engagement surfaces 2b and 3b when the clutch mechanism is engaged, thereby stably maintaining the engaged state of the clutch mechanism.

[0063] Here, surface roughness (Ra) refers to the arithmetic mean roughness value (μm) measured in accordance with the Japanese Industrial Standard (JIS B 0601-2001). This surface roughness (Ra) value is sufficient if it satisfies the region of each engaging surface 2b, 3b in which the engaging elements 5a, 5b can slide in the circumferential direction. In the clutch mechanism shown in the illustration, the cylindrical engaging surface 3b formed on the outer member 3 is fully satisfied, and the engaging surface 2b formed on the inner member 2 is fully satisfied on both the front cam surface portion 2c and the rear cam surface portion 2d.

[0064] In this rotation control device 1, the shock-absorbing member 18 is supported by the cover 4b, but the arrangement and number of shock-absorbing members can be changed as appropriate. As an example of such a change, a second embodiment of this invention is shown in Figure 7. The second embodiment differs from the first embodiment only in the arrangement of the shock-absorbing members; all other configurations are the same. Therefore, the same reference numerals are used for parts corresponding to the first embodiment, and their description is omitted.

[0065] The shock-absorbing member 20 shown in Figure 7 is attached to the portion of the armature 13 that faces the rotor 14 in the axial direction. A circumferentially continuous annular groove 13a is formed in the portion of the armature 13 that faces the rotor 14. The shock-absorbing member 20 is mounted in this annular groove 13a. The axial depth of the annular groove 13a is set to be shallower than the axial thickness of the shock-absorbing member 20 when no external force is acting on it, and to a depth that allows the shock-absorbing member 20 to be completely embedded when it is compressed and deformed within the elastic range. Alternatively, the shock-absorbing member may be attached to the portion of the rotor 14 that faces the armature 13 in the axial direction with a similar configuration.

[0066] In the first and second embodiments, examples were shown in which shock-absorbing members 18 and 20 were used to suppress the collision noise between the armature 13 (see Figures 1 and 7) and the rotor 14. However, it is undesirable that when the electromagnet 15 is de-energized, the elastic restoring force of the separation spring 10 (see Figure 2), transmitted from the separation spring 10 to the armature 13 via the motion conversion mechanism 16, causes the armature 13 to separate from the rotor 14 and be received by the stopper portion 11, resulting in a collision noise between the armature 13 and the stopper portion 11. It is also possible to configure a rotation control device that employs shock-absorbing members to suppress the collision noise between the armature 13 and the stopper portion 11 instead of the shock-absorbing members 18 and 20. As an example, a third embodiment of this invention is shown in Figure 8. The third embodiment differs from the first embodiment only in the arrangement of the shock-absorbing members; the other configurations are the same. Therefore, the same reference numerals are used for parts corresponding to the first embodiment, and their explanation is omitted.

[0067] The shock-absorbing member 20 shown in Figure 8 is attached to the portion of the armature 13 that faces the stopper portion 11 in the axial direction. A circumferentially continuous annular groove 13a is formed in the portion of the armature 13 that faces the stopper portion 11. The shock-absorbing member 20 is mounted in this annular groove 13a. Alternatively, the shock-absorbing member may be attached to the portion of the stopper portion 11 that faces the armature 13 in the axial direction, using a similar configuration.

[0068] By adopting the configuration shown in Figure 8, when the electromagnet 15 is de-energized, the impact when the armature 13 is caught by the stopper portion 11 is absorbed by the impact absorbing member 20 attached to the portion of the armature 13 facing the stopper portion 11 (or the portion of the stopper portion 11 facing the armature 13), thereby reducing the collision noise between the armature 13 and the stopper portion 11.

[0069] It is also possible to configure the rotation control device to include an impact absorbing member for suppressing collision noise between the armature and the stopper, and an impact absorbing member for suppressing collision noise between the armature and the rotor. As an example, a fourth embodiment of this invention is shown in Figure 9. The fourth embodiment corresponds to a device that includes both the impact absorbing member 18 shown in the first embodiment (see Figure 5) and the impact absorbing member 20 shown in the third embodiment (see Figure 8). Therefore, the same reference numerals are used for the parts corresponding to the first and third embodiments, and their descriptions are omitted.

[0070] The rotation control device shown in Figure 9 absorbs the impact of the armature 13 being attracted to the rotor 14 with the shock-absorbing member 18 when the electromagnet 15 is energized, and absorbs the impact of the armature 13 being caught by the stopper part 11 with the shock-absorbing member 20 when the electromagnet 15 is de-energized. Therefore, it is possible to reduce the impact noise of the armature 13 both when the electromagnet 15 is energized and when the electromagnet 15 is de-energized.

[0071] A fifth embodiment of this invention is shown in Figure 10. The fifth embodiment corresponds to a configuration in which both the shock-absorbing member 20 shown in the second embodiment (Figure 7) and the shock-absorbing member 20 shown in the third embodiment (Figure 8) are provided. Therefore, the same reference numerals are used for the parts corresponding to the second and third embodiments, and their descriptions are omitted.

[0072] The rotation control device shown in Figure 10 absorbs the impact when the armature 13 is attracted to the rotor 14 when the electromagnet 15 is energized by the impact absorbing member 20 facing the rotor 14, and absorbs the impact when the armature 13 is caught by the stopper part 11 when the electromagnet 15 is de-energized by the impact absorbing member 20 facing the stopper part 11. Therefore, it is possible to reduce the impact noise of the armature 13 both when the electromagnet 15 is energized and when the electromagnet 15 is de-energized.

[0073] In the embodiments described above, examples were shown in which the shock-absorbing member was directly attached to the armature, etc. However, it is also possible to fix the shock-absorbing member to a separate member and then attach that separate member to the armature, etc. A sixth embodiment is shown in Figure 11 as an example of this. The sixth embodiment differs from the second embodiment (see Figure 7) only in the configuration of the shock-absorbing member; all other configurations are the same. Therefore, the same reference numerals are used for parts corresponding to the second embodiment, and their description is omitted.

[0074] The rotation control device shown in Figure 11 includes a shock absorption unit 30 attached to the armature 13. The shock absorption unit 30 consists of an annular shock absorption member 31 and a metal ring 32 that covers the shock absorption member 31. The metal ring 32 consists of an annular plate portion 33 located between the axially opposing surfaces of the armature 13 and the rotor 14, and an outer cylindrical portion 34 including an inward-facing projection that is held axially movable in a circumferential groove 13b formed on the outer circumference of the armature 13. The shock absorption member 31 is fixed by adhesive bonding to the axially opposing surface of the annular plate portion 33 relative to the armature 13.

[0075] By adopting the shock-absorbing unit 30 shown in Figure 11, the shock-absorbing member 31 receives and absorbs the impact via the metal ring 32, making it easy to ensure the durability of the shock-absorbing member 31 while utilizing its excellent shock-absorbing performance. Note that the shock-absorbing members 18 and 20 in each of the above embodiments may be replaced with those configured as shown in Figure 11.

[0076] The rotation control devices according to each of the above embodiments can be used, for example, in a vehicle steering system. As an example, the vehicle steering system shown in Figure 12 includes a steering rack 40 supported so as to be movable in the left-right direction of the vehicle, a steering pinion 41 that meshes with the steering rack 40, a steering wheel 42 that is rotated by the driver, a rotation transmission path 43 that transmits rotation between the steering wheel 42 and the steering pinion 41, a steering motor 45 that inputs driving force to the rotation transmission path 43 to steer a pair of wheels 44, and a rotation control device 1.

[0077] The steering rack 40 is housed in a rack housing 46 in the center, with both left and right ends exposed. The rack housing 46 supports the steering rack 40 so that it can move in the left-right direction of the vehicle. Both left and right ends of the steering rack 40 are connected to a pair of left and right wheels 44 via tie rods 47 so that the orientation of the left and right wheels 44 changes in accordance with the movement of the steering rack 40. The steering pinion 41 is rotatably supported in the rack housing 46.

[0078] In the rotation transmission path 43, a reaction force motor 48, a rotation control device 1, and a steering motor 45 are provided in order from the steering wheel 42 side toward the steering pinion 41 side. The reaction force motor 48 is an electric motor that applies a steering reaction force to the steering wheel 42 in the opposite direction to the direction of rotation of the steering wheel 42 caused by the driver's steering. The steering motor 45 is an electric motor that inputs driving force to the rotation transmission path 43 in accordance with the steering torque of the steering wheel 42 caused by the driver.

[0079] The rotation control device 1, under normal conditions, disconnects the transmission of rotation between the steering wheel 42 and the steering pinion 41. However, in abnormal situations such as power loss, it transmits rotation between the steering wheel 42 and the steering pinion 41. In this way, the rotation control device 1 functions as a backup clutch for the vehicle's steering system.

[0080] In the embodiments described above, examples were given in which rollers were used as the engaging element. However, this invention can be applied to specifications in various cases, and can be similarly applied to rotational control devices equipped with appropriate clutch mechanisms, such as those using balls or sprags as the engaging element, or employing a ball cam mechanism as the motion conversion mechanism.

[0081] Furthermore, in the embodiments described above, a clutch mechanism was exemplified in which the spring force of the separation spring biases the engaging element to the engaged position and indirectly applies that spring force to the armature via the engaging element and motion conversion mechanism to separate the armature from the rotor. However, it is also possible to have a clutch mechanism that applies spring force directly to the armature to separate it from the rotor, for example, a clutch mechanism equipped with a separation elastic member sandwiched axially between the armature and the rotor.

[0082] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Accordingly, the scope of the invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0083] 1. Rotation control device 2 Inner member 2b Engagement surface 3 Outer member 3b Engagement surface 4 cases 5a, 5b engager 6 Cage 10 Detachment spring 11 Stopper section 13 Armature 14 rotors 15 Electromagnet 18, 20, 31 Shock-absorbing material

Claims

1. A rotation control device comprising an electromagnet, an armature attracted to the electromagnet, a release spring for returning the armature attracted to the electromagnet, a stopper portion for receiving the armature as it is moved by the spring force of the release spring, a case housing the electromagnet and the stopper portion, and an impact absorbing member provided inside the case for reducing the collision noise of the armature, wherein the state of rotation control switches in accordance with the movement of the armature by the electromagnet or the release spring, The aforementioned shock-absorbing member is formed of ethylene propylene diene rubber (EPDM), A rotary control device characterized in that the lubricant used to lubricate the movable parts housed in the aforementioned case is a grease using a polyglycol-based oil.

2. It comprises an inner member, an outer member surrounding the inner member, and a clutch mechanism for transmitting and interrupting rotational torque between the inner member and the outer member. The rotation control device according to claim 1, wherein the clutch mechanism comprises an engagement surface formed on the inner circumference of the outer member, an engagement surface formed on the inner member, an engaging element disposed between the engagement surface of the outer member and the engagement surface of the inner member, and a retainer arranged to be movable in the circumferential direction between an engagement position for holding the engaging element and engaging the outer member and the inner member, and a release position for disengaging the engagement, and is provided to switch between transmitting and interrupting the rotation torque in accordance with the axial movement of the armature by the electromagnet or the separation spring.

3. The rotation control device according to claim 2, wherein the surface roughness (Ra) of the engagement surface of the outer member and the surface roughness (Ra) of the engagement surface of the inner member are each 0.1 or more and 3.2 or less.

4. A steer-by-wire system comprising a rotation control device according to any one of claims 1 to 3.

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