JP2003156083A - Dynamo-electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem on an dynamo-electric brake device where the rotation of an electric motor is converted into linear motion by a screw-and-nut mechanism that the efficiency of conversion into the motion is poor, power demand for the motor is greater, and a device is larger and its weight is heavier when using a speed reducing mechanism for increasing driving force. SOLUTION: A driving side cam member 6 having a magnet 8 at a shaft portion 7 is rotated by energizing a coil 5 to cause the rotation of a driving side cam face 16. Rollers 25 are radially arranged in equally spaced relation between the driving side cam face 16 and a driven side cam face 22 of a driven side cam member 11 opposed thereto and the driven side cam member 11 is supported in a non-rotatable but axially movable manner by a slide supporting portion 18. During rotating the driven side cam face 11, the driven side cam member 11 moves a brake pad 20 via the roller 25 in the direction of sandwiching a brake rotor 24 to generate braking force.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric brake for operating a brake pad of a disc brake by converting a rotary motion of an electric motor into a linear motion by a cam.
The present invention also relates to an electric brake device that generates a braking force by an output of an electric motor. 2. Description of the Related Art Conventionally, various types of brake devices have been employed in various fields. BACKGROUND ART Hydraulically operated brakes have been widely used as vehicle brake devices. However, in recent years, an electric brake that generates a braking force by the rotational force of an electric motor has become more compact as a whole because complicated hydraulic circuit devices in a hydraulically actuated brake are not required. Attention has been paid to the fact that various complicated braking controls can be easily performed. [0003] Various types of electric brakes have been proposed.
There is an electric brake device as shown in US Pat. No. 967. In this electric brake device, as shown in FIG. 6, a caliper 31 has an electric motor 32 for operating a brake,
A force transmission conversion mechanism 33, a pressing member 34, and the like are provided. Each of the caliper 31 and the pressing member 34 is provided with a pair of brake pads 35 constituting a brake member, and the pair of brake pads 35 move in a direction to sandwich a brake rotor 36 as a member to be braked,
The brakes are working. The output shaft 46 of the electric motor 32 supported by the caliper 31 is provided with a first gear 37 constituting the force transmitting means 33, and the first gear 37 is further connected to a second gear 38 as a rotating member. Are engaged. Second gear 3
8 is provided with a nut 39 integrally, and this nut 39 is rotatably supported by the shaft support 40 of the caliper 31. The nut 39 is screwed with a screw shaft 41 which is prevented from rotating and is movable in the axial direction. A pressing member 34 is attached to the left end of the screw shaft 41 in the drawing. Thus, in this electric brake, the output shaft 46, the first gear 37, the second gear 38,
The nut 33 rotates in conjunction therewith, and the rotational movement is converted into a linear movement to the left in the figure by the screw shaft 41.
This movement of the screw shaft 41 causes the pressing member 34
, The caliper 31 moves rightward in the drawing by the reaction force, and the opposing brake pads 35 move in the same direction, sandwiching the brake rotor 36 between the two brake pads 35 and applying a braking action. It is carried out. When the brake force is released, the electric motor 32 is rotated in reverse by releasing the pedaling force of the pedal or by a brake release control signal.
6 is released by moving in the direction away from 6. In the above-mentioned conventional electric brake device, the rotational force of the electric motor 32 is reduced by a gear mechanism and then transmitted to a force transmission conversion mechanism 33 corresponding to a nut. Is converted into a linear motion of the screw shaft 41 corresponding to a bolt, but this method has the following problems. That is, in the case of using a screw mechanism, if the screw pitch is reduced, the thread becomes too thin to receive a large force here, and the pitch is limited due to the strength of the screw. For this reason, only a certain amount of screw leads can be taken, and therefore a large conversion coefficient for converting the rotational force into a linear motion cannot be obtained. As a result, in order to obtain a linear force necessary to generate a predetermined or more braking force, a correspondingly large rotational force is required, and a large motor is required. Such an increase in the size of the motor causes an increase in the weight of the entire brake operating mechanism and an increase in power consumption. In particular, in the case of an electric brake for an automobile, there is a problem that the suspension capacity is reduced due to an increase in unsprung weight. In the electric brake described in the above publication, a gear reduction mechanism is combined as one of means for alleviating this. However, it is not preferable to use a reduction mechanism having a complicated structure as a whole device. In addition, this causes an increase in the weight, and eventually the entire brake operation mechanism becomes large due to this portion, and as a result, the weight increases. As a result, the problem of a decrease in the suspension ability due to an increase in the unsprung weight occurs. [0011] In addition, a brake device for an automobile is required to have particularly high reliability. However, in such a device, since a force is transmitted from a motor through two mechanisms, ie, a speed reduction mechanism and a linear motion conversion mechanism, the probability of failure is high. And increase the reliability. Therefore, the present invention is capable of converting the rotary motion of an electric motor into a linear motion by a simple mechanism, has a good motion conversion efficiency at that time, and generates a large brake operating force even with a small electric motor. The main object of the present invention is to provide an electric brake device capable of reducing the size and weight of the entire device. According to the present invention, there is provided an electric brake device for converting the rotational motion of an electric motor into a linear motion and pressing a brake member against a member to be braked. This is an electric brake device characterized by using a cam mechanism for conversion into linear motion. Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall configuration of an embodiment of the electric brake device according to the present invention, and FIG. . In FIG. 1, a housing 2 of an electric brake device 1 is fixed to a caliper 3 of a disc brake device with bolts 4 and supported. A coil 5 forming a cylindrical space is fixed in the housing 2, and a shaft 7 of a driving cam member 6 penetrates the cylindrical space of the coil 5. A magnet 8 is fixed to the outer periphery of the magnet so as to face the coil 5. As a result, when the coil 5 is energized, the shaft portion 7 fixing the magnet 8 receives a rotational force, and the entire drive-side cam member 6 receives a rotational force in a predetermined direction. The driving side cam member 6 is rotatably supported on the housing 2 by a bearing 10 at a right end portion of the shaft portion 7 in the drawing, and a support opening of a driven side cam member 11 described later at a left end portion in the drawing. The bearing 12 is supported by a bearing 13 so as to be relatively movable and rotatable in the axial direction. The drive side cam member 6 has a flange portion 14 extending to the outer periphery.
A drive side cam surface 16 as shown in FIG. 2 is formed on the left end surface 15 of the flange portion 14 in the drawing. The outer peripheral portion of the flange portion 17 of the driven side cam member 11 is supported by a slide support portion 18 so as to be non-rotatable with respect to the inner surface of the housing 2 and movably in the axial direction. The pressing portion 19 penetrates through the opening of the caliper 3 from the end face opening at the end of the housing 2 and the back plate 21 for fixing the brake pad 20.
Is in contact with the back of On the right end face of the flange portion 17 of the driven cam member 11 in the drawing, that is, on the end face of the driving cam member 6 facing the driving cam face 16, a driven cam face 22 that performs an operation described later is provided. Has formed. A brake rotor 24 is disposed between the brake pads 20 opposed to each other in the caliper 3, and when the driven cam member 11 moves to the left in the drawing as described later, first, the brake pad on the right in the drawing. 20 abuts on one surface of the brake rotor 24, and the caliper 3 moves rightward in the figure by the reaction force, whereby the brake pad 20 on the left side in the figure abuts on the other surface of the brake rotor 24,
As a result, the brake rotor 24 is held between the brake pads 20 on both sides to apply a braking force. The driving side cam surface 16 and the driven side cam surface 2
In the illustrated embodiment, a plurality of rollers 25 as one mode of a rolling element are arranged at equal intervals between the two. In the illustrated embodiment, the roller 25 is divided into two in its length direction to prevent the occurrence of skew at the time of cam operation described later. However, for convenience of description, the rollers divided into a plurality are collectively referred to as one roller. The number of the rollers 25 is, for example, as shown in FIG.
As shown in (a), three may be arranged at equal intervals of 120 degrees, or as shown in FIG. (B), four may be arranged at equal intervals of 90 degrees. Further, an arbitrary number can be selected, such as arranging six at 60 degrees, but if the number is increased, the force applied to each roller is dispersed, but the interval between the rollers becomes narrower, so the lead angle of the cam is reduced. Is difficult to reduce, and the motion conversion efficiency decreases. Therefore, an appropriate number is selected in consideration of this point. The illustrated embodiment shows an example in which four rollers 25 are arranged at equal intervals of 90 degrees. In the above-described embodiment, an example in which the roller 25 is used as the rolling element has been described. However, the same operation can be performed by using a ball instead of the roller 25.
As shown in (c), they may be arranged at equal intervals of 120 degrees, or as shown in FIG. If necessary, a plurality of rollers can be arranged in the radial direction, similarly to the case where the rollers are divided into two. The cam surfaces of the driving side cam surface 16 and the driven side cam surface 22 which cooperate are formed and arranged symmetrically with respect to each other. When the brake is not operated, the valleys of the two cam surfaces are arranged as shown in FIG. In this case, the roller 25 is located at the position shown in FIG.
As shown in the development view of the cam surface, all the rollers 25 are located at the valleys of both cam surfaces in a state where they are held by the retainer 26. When the electric brake device 1 having the above configuration is operated, in the initial state of the electric brake, the driving side cam surface 16 and the driven side cam surface 22 are arranged as shown in FIG.
In the state of (a), all the rollers 25 are located at the valleys of the two cam surfaces while being held by the retainer 26, and the two cam surfaces and one part of the roller 25 disposed therebetween. Is shown in FIG. In this state, when the driver steps on the brake or when a brake operation signal is input from the brake control device, the coil 5 is energized, and the driving cam member 6 fixing the magnet 8 rotates. The relationship between the cam surface and the roller at this time is shown in FIG. 4C. As shown in FIG. 4C, the driven cam member 11 that does not rotate remains at the reference position A. Thus, the driving cam member 6 that rotates as described above moves L1 in the direction of the outlined arrow in the drawing. Note that this movement distance L1
Is actually the rotation length of an arbitrary portion of the driving side cam member 11. As a result of the rotational movement of the driving side cam member 6,
Each roller 25 sandwiched between the driving side cam surface 16 and the driven side cam surface 22 rotates in the direction of the arrow in FIG. 4C by its frictional force so as to ride on the convex portion of the driving side cam surface 16. , And similarly acts on the driven-side cam surface 22, so that this surface also moves so as to ride on the convex portion. As a result, the drive side cam surface 16 moves by L2, which is half the length of L1. As described above, the rotation of the driving cam member 6 causes the roller 25 to move between the driving cam surface 16 and the driven cam surface 2.
2, the driven cam 11 is moved by the slide support 18 in the axial direction with respect to the driving cam 6 which does not move in the axial direction of the electric motor 1 when the brake is actuated. Since it is movably supported, it moves in the axial direction by a distance indicated by d1 in FIG. When such operation of the drive side cam member 6 continues, in the final state of the brake operation in which the brake pad holds the brake disk, as shown in FIG. And the roller 25 stops at this time.
As a result, the driven side cam member 11 is in a state of being moved by a distance of d2 from the initial state. When the driver releases the brake pedal, or when a signal for releasing the braking force is input from the brake control device as in anti-skid control, the energization of the coil 5 is stopped, and the rotation of the drive side cam member 16 is stopped. Power is released. As a result, the reaction force that has pressed the disk plate 24 against the brake pad 20 causes a force that causes the brake pad 20 to separate from the disk plate to act directly, and the force attempts to push the driven cam member 11 back. The force exerts a force in the direction indicated by the arrow in FIG. 4E from the driven cam surface 22 to the roller 25 by the force, and the roller 25 rotates in the direction indicated by the arrow in FIG. And move while rotating in the direction of the concave portions of both cam surfaces. As a result, when the brake pad 20 applies a pressing force to the disk plate 24, a force for returning the roller 25 to the original position always acts, so that the electric motor does not reversely rotate and a return member such as a return spring is used. The brake operating member can be returned to the original brake release position. When the lead angle of the cam is set to be small, the return force to the drive cam member 6 is reduced accordingly, and in that case, a return spring is used as necessary to perform a more reliable return operation. It can also be configured. The cam surface as a mechanism for converting the rotational movement of the electric motor 1 into a linear movement pressing the brake pad is as follows:
For example, as shown in FIG. 5A, it can be set to increase in proportion to the rotation angle. However, the shape of the cam surface can be set arbitrarily. ), The operation is initially performed at a gentle lead angle with respect to the rotation of the drive cam, and the lead angle is gradually increased so as to perform a large movement, or as shown in FIG. In this way, it is possible to set such that the drive cam is operated with a larger stroke for the same rotation amount of the drive cam at first, and the stroke is gradually reduced. By changing the shape of the cam in this manner, any brake operation characteristics can be obtained without performing special operation control. If the cam drive member does not rotate in the opposite direction, it is only necessary to form a predetermined cam surface shape only in one direction of the rotational direction. Since the electric brake according to this embodiment uses the above-described cam mechanism, it is possible to reduce the lead as the amount of movement of the brake pad for a predetermined rotation of the electric motor. It can generate torque. This eliminates the need for a speed reduction mechanism from the electric motor, thereby eliminating the need for using a complicated mechanism. Further, the rotational force of the motor is converted into a linear motion through a cam mechanism and the member to be braked is pressed, so that the motion can be converted from the motor with only one cam mechanism.
The reliability of the mechanism is improved, the total number of parts is reduced, the device can be made compact, and the overall weight can be reduced. In a vehicle brake system, the clearance between the brake member and the braked member at the time of being braked may be small, and in many cases a clearance slightly rubbing may be sufficient. For this reason, the stroke of the member to be braked required for the braking may be small, and even if the stroke is small, there is no particular problem. Therefore, it is difficult to set a large movement amount by using a cam device as in the present invention. However, when the disc brake is operated, the stroke may be 1 mm or less. Can obtain a sufficient stroke. In the apparatus according to the present invention, since the rollers are arranged between the slopes of the cams, rolling motion occurs between the cams and no sliding motion occurs, so that no sliding friction occurs. Therefore, the motion conversion efficiency of the cam is high, and the power consumption of the motor can be reduced accordingly. Further, in the brake device, it is necessary to release the braking force surely during non-braking, but in the device according to the present invention, when there is a pressing force of the brake pad against the brake rotor, the cam mechanism is operated by the force. Can be returned to the original state, and the braking force can be reliably released. At that time, there is no need to perform operations such as reversing the motor, so that power consumption can be reduced. In addition, no loss due to friction occurs during the return operation, so that a reliable operation can be performed and a device with high operation efficiency can be provided. Further, in the above embodiment, since the cam roller is divided into two in the axial direction, the occurrence of skew due to the rotation of the roller can be reduced, and this also improves the efficiency of cam motion conversion. Can contribute. Further, in this embodiment, since the magnet 8 of the motor is directly disposed on the shaft portion 7 of the driving side cam member 6, the apparatus can be made compact. Since the electric brake device according to the present invention is constructed as described above, the rotational motion of the electric motor can be converted into a linear motion by a simple mechanism, and the friction is small. Efficient, even a small electric motor can generate a large brake operation force, consume less power, and can reduce the size and weight of the entire device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an embodiment of the present invention. FIG. 2 is a sectional view of a main part showing a side view of a cam mechanism portion in the embodiment. FIGS. 3A and 3B are diagrams showing an arrangement of rolling elements on a cam surface in the embodiment, wherein FIG. 3A shows an arrangement in which three rollers are arranged at equal intervals using rollers as rolling elements, and FIG. At 4
(C) shows an embodiment in which three balls are arranged at equal intervals using balls as rolling elements, and (d) shows an embodiment in which four are arranged at equal intervals. FIG. 4 is a view showing a state of operation of a driving side cam surface, a driven side cam surface, and rolling elements disposed between the driving side cam surface and the rolling element in the embodiment, and FIG. FIG. 2 is an expanded view of these parts.
Is a partially enlarged view, (c) is a state at the start of the brake operation, (d) is a final state of the brake operation, and (e) is a state at the time of the return operation when the brake operation is released. FIG. FIG. 5 is a view showing various shapes and operating characteristics of a cam surface of the embodiment. FIG. 6 is a sectional view showing an example of a conventional electric brake device. [Description of Signs] 1 Electric brake device 2 Housing 3 Caliper 5 Coil 6 Drive cam member 7 Shaft 8 Magnet 11 Driven cam member 13 Bearing 14 Flange 16 Drive cam surface 17 Flange 18 Slide support 19 Press Part 20 brake pad 21 back plate 22 driven cam surface 24 brake rotor 25 roller 26 cage

Claims (1)

Claims: 1. An electric brake device for converting a rotary motion of an electric motor into a linear motion and pressing a brake member against a member to be braked, wherein a cam mechanism is used for the conversion into the linear motion. An electric brake device characterized by the above-mentioned.