JP3795420B2 - Electric disc brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a rotation angle sensor which detects a rotation angle of the rotary parts of the advancing and retreating mechanism with high precision without increasing the number of parts and at a low cost, and to raise flexibility of the layout at the time of installing an electric disk brake by minimizing the installation space for the rotation angle sensor and compactly forming a caliper body. <P>SOLUTION: A reduction gear mechanism 17 reducing a driving force of the electric motor and transmitting it to the advancing and retreating mechanism consists of a rotatable planetary arm 18 by the electric motor 15, a planetary gear 23 rotatably supported on the outside periphery of the planetary arm 18 and a sun gear 26 which is unrotatably fixed to the caliper body 8 and rotating the planetary gear 23. The rotation angle sensor is formed with a projection part 52 provided on the outer periphery of the planetary arm 18 and a coil 19 circumferentially arranged facing the outer periphery of the projection part 52. A waveform output voltage is generated in the coil 19 along with passing of the projection part 52, the rotation angle of the planetary arm 18 is detected with the waveform output voltage and an amount of the advancing and retreating of the advancing and retreating mechanism is calculated. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial application fields]
The present invention relates to an electric disc brake that is mounted on various vehicles such as an automobile and a motorcycle, and that moves forward and backward by a driving force of an electric motor, and presses and slides a friction pad on a disc rotor to perform braking. Therefore, the advance / retreat amount detection means of the advance / retreat mechanism is inexpensively provided without increasing the number of parts.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in various vehicles such as automobiles and motorcycles, an electric disc brake that performs braking by pressing and sliding a friction pad against a disc rotor via a pressing member by an advancing / retreating mechanism that is operated by a driving force of an electric motor. Exists. In order to detect the advance / retreat amount of the advance / retreat mechanism and obtain the displacement amount of the friction pad with respect to the disk rotor, the invention described in Japanese Patent Application Laid-Open No. 2000-104763 and the invention described in Japanese Patent Application Laid-Open No. 2000-62591 are described as an advance / retreat mechanism. Using a ball screw mechanism, the rotation angle of the ball screw nut is detected by a rotary encoder consisting of a rotor provided on the outer periphery of a ball screw nut that is rotated by an electric motor and a stator provided on the caliper body facing this rotor. Then, the advance / retreat amount of the ball screw shaft was calculated.
[0003]
[Problems to be solved by the invention]
However, in the conventional rotary encoder, it is necessary to provide a rotor and a stator separately from the advance / retreat mechanism and the reduction gear mechanism as described above, which increases the number of parts and labor of assembly, and limits the installation position of the rotary encoder. It will be. In addition, the caliper body becomes larger due to the increase in the number of parts, and the degree of freedom in layout during installation on the vehicle body decreases.
[0004]
The present invention is intended to solve the above-described problems, and a rotation angle sensor capable of detecting the rotation angle of a rotating component of an advance / retreat mechanism with high accuracy is simple and inexpensive without increasing the number of components. To try to form. In addition, the installation space for the rotation angle sensor is minimized, the caliper body is compactly formed, and the degree of freedom in layout when installing the electric disc brake is increased.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention advances and retracts by the driving force of the electric motor and generates a pressing force on the pressing member of the friction pad, and reduces the driving force of the electric motor to the advancing and retracting mechanism. In the electric disc brake, which is provided with a reduction gear mechanism for transmitting in the caliper, and brakes by pressing and sliding the friction pad against the disc rotor by the advance / retreat mechanism, the reduction gear mechanism is rotated by an electric motor. A magnet that can act as a rotor of the electric motor is disposed on the outer periphery of the cylindrical portion, and a large diameter portion larger than the cylindrical portion is provided on the rear side of the cylindrical portion opposite to the friction pad. A planetary arm provided with a projection on the large diameter portion, a planetary gear pivotally supported on the outer periphery of the planetary arm, and a sun gear fixed to the caliper body so as not to rotate and rotating the planetary gear And A rotation angle sensor is formed by a protrusion provided on the outer periphery of the planetary arm and a coil arranged circumferentially so as to face the outer periphery of the protrusion. An output voltage is generated, and the rotation angle of the planetary arm is detected from the output voltage of this waveform, so that the advance / retreat amount of the advance / retreat mechanism can be calculated.
[0006]
Further, the planetary gear of the reduction gear mechanism may be pivotally supported on a protrusion provided on the outer periphery of the planetary arm.
[0007]
Further, the advance / retreat mechanism has a ball screw nut having a diameter larger than that of the planetary gear of the reduction gear mechanism and rotated by the rotation of the planetary gear, and a ball that moves forward and backward in the direction of the disk shaft by the rotation of the ball screw nut. The ball screw nut consists of a screw shaft, and the planetary gear rotates a large ball screw nut to further reduce the rotational force transmitted from the reduction gear mechanism, thereby applying a pressing force to the pressing member via the ball screw shaft. It may be generated.
[0008]
[Action]
The present invention is configured as described above, and a rotation angle sensor is constituted by a projecting portion of a planetary arm and a coil disposed so as to face the projecting portion. As described above, the coils are arranged to form the stator, but the planetary arm provided with the protrusions can be used as the rotor. For this reason, there is no need to provide a separate rotor for the rotation angle sensor, the number of components and assembly work are not increased, installation space can be minimized, and the rotation angle sensor can be formed simply and inexpensively. It becomes possible to do. In addition, the caliper body can be compactly formed, and the degree of freedom in layout when the electric disc brake is installed on the vehicle body is increased.
[0009]
When the driver depresses the brake pedal to perform a braking operation, the electric motor is driven and the planetary arm of the reduction gear mechanism rotates. Due to the rotation of the planetary arm, the planetary gear pivotally supported on the planetary arm rotates on the outer periphery of the sun gear. Due to the rotation of the planetary gear, the driving force of the electric motor is decelerated and transmitted to the advance / retreat mechanism, and the advance / retreat mechanism is activated to generate a pressing force on the pressing member of the friction pad. It is pressed against the disk rotor and braking is performed.
[0010]
Due to the rotation of the planetary arm, the projection provided on the outer periphery of the planetary arm generates a waveform output voltage by rotating in the circumferential coil, so the rotation angle of the planetary arm can be adjusted with high accuracy. It can be detected. Based on the detected rotation angle, the advance / retreat amount of the advance / retreat mechanism can be calculated, the position of the friction pad relative to the disc rotor is recognized, the drive of the electric motor is controlled, and the amount of movement of the friction pad during braking is determined. By adjusting, accurate braking is possible.
[0011]
Further, the advance / retreat mechanism may be any conventionally known mechanism, for example, a ball screw nut having a diameter larger than that of the planetary gear of the speed reduction mechanism and rotating by the rotation of the planetary gear, and the ball screw nut. Thus, it is possible to use a ball screw mechanism including a ball screw shaft that moves back and forth in the direction of the disk shaft. By rotating the ball screw nut having a large diameter with the planetary gear, the driving force of the electric motor decelerated by the reduction gear mechanism is further decelerated. It is possible to efficiently convert to a force and generate a strong pressing force on the pressing member. The advance / retreat amount of the ball screw shaft can be detected based on the rotation angle detected by the rotation angle sensor.
[0012]
【Example】
DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (1) is a disk rotor that is connected to a wheel of an automobile and rotates integrally with it, facing both friction surfaces (2). As shown, a pair of friction pads (3) and (4) are arranged inside the tire wheel (5). Further, a bracket (6) is fixed to the vehicle body so as to face the disk rotor (1), and a caliper support arm (projecting from the fixed side across the outer periphery of the disk rotor (1) to the opposite side is provided. 7), the friction pads (3) and (4) are slidably disposed.
[0013]
Further, a caliper body (8) for pressing the friction pads (3), (4) against the disc rotor (1) on the caliper support arm (7) of the bracket (6), as shown in FIG. It is connected via 9) so that it can move forward and backward. As shown in FIG. 1, the caliper body (8) includes an action portion (10) disposed on the back surface of one friction pad (3) and a friction pad (4) between the disk rotor (1). A reaction portion (12) provided with a reaction force claw (11) disposed on the back surface and a bridge portion (13) for connecting the action portion (10) and the reaction portion (12) across the outer periphery of the disk rotor (1). It consists of and.
[0014]
As shown in FIG. 1, the action portion (10) has a ball screw mechanism for generating a pressing force of the brushless electric motor (15) and the friction pads (3) and (4) in the cylinder (14). (16) and a reduction gear mechanism (17) for reducing and transmitting the driving force of the electric motor (15) to the ball screw mechanism (16) are housed. The reduction gear mechanism (17) includes a planetary arm (18) that can be rotated by the driving force of the electric motor (15), a planetary gear (23) that is pivotally supported by the planetary arm (18), and The planetary gear (23) is configured to rotate with a sun gear (26).
[0015]
In the planetary arm (18), a magnet (39) acting as a rotor of the electric motor (15) is arranged on the outer periphery of the cylindrical portion (20), and the bearing portion (57) is driven by the driving force of the electric motor (15). ) Through the cylinder (14). In the present invention, the planetary arm (18) can also be used as a rotor of a rotation angle sensor, which will be described later, so that a cylindrical portion (20) is provided at the rear of the cylindrical portion (20) opposite to the friction pad (3). A large diameter portion (21) having a larger diameter than that of 20) and having a triangular side surface is provided. Then, the planetary gear (23) is pivotally supported on the three protrusions (52) of the large-diameter portion (21) formed by the triangular shape, and as shown in FIGS. 1 and 2, Each planetary gear (23) is projected to the outside from a notch window (22) opened on the outer periphery of the protrusion (52). Further, by forming the large-diameter portion (21) in a triangular shape, the planetary arm (18) can be reduced in weight and the material cost can be reduced, and can be used as a rotor of a rotation angle sensor described later. Is.
[0016]
The planetary gear (23) separates the first gear portion (24) and the second gear portion (25) having a smaller number of teeth than the first gear portion (24) in the axial direction. The first gear portion (24) is integrally formed and meshed with a sun gear (26) fixed to the caliper body (8) so as not to rotate, and the planetary gear (23) of the planetary gear (23) is engaged with the sun gear (26). It can be turned.
[0017]
As shown in FIGS. 1 and 3, the sun gear (26) is fixed by opening a plurality of insertion holes (29) at equal intervals in the back plate (27) disposed at the rear of the caliper body (8). The fixing pin (28) inserted through the insertion hole (29) is inserted into the fixing hole (30) recessed in the back surface of the sun gear (26). The head of the fixing pin (28) is pressed by the cap (33) mounted in the mounting hole (32) of the back plate (27), and the state of insertion into the fixing hole (30) is maintained. When the cap (33) is removed, the fixing pin (28) is removed from the fixing hole (30) by the urging force of the pressing ridge (31) mounted between the head of the fixing pin (28) and the back plate (27). The sun gear (26) can be released by releasing.
[0018]
In the planetary arm (18), the ball screw nut (34) of the ball screw mechanism (16) is accommodated through the bearing portion (58) so as to be rotatable but not to be able to advance and retract. The ball screw nut (34) has a reduction gear (35) having fewer teeth than the sun gear (26) fixed to the outer periphery of the rear end disposed on the large diameter portion (21) side of the planetary arm (18). Yes. The reduction gear (35) is engaged with the second gear portion (25) of the planetary gear (23), and the ball screw nut (34) can be rotated by the rotation of the planetary gear (23). A ball screw shaft (38) is screwed into a ball groove (36) provided on the inner diameter side of the ball screw nut (34) via a plurality of balls (37) so as to be able to advance and retract.
[0019]
The ball screw shaft (38) has a flat pad pressing plate (40) as a pressing member for the friction pad (3) connected to the tip of the ball screw shaft (38) so as not to be separated from each other. With this pad pressing plate (40), the friction pad (3) can be pressed in a large area without concentrating the pressing force on a part thereof, and can be pressed in parallel with the disk rotor (1).
[0020]
Further, in this embodiment, an extendable dust seal (47) is connected between the outer periphery of the pad pressing plate (40) and the inner periphery of the cylinder (14), and the opening (45) of the cylinder (14) is connected. ) To prevent entry of dust, water droplets, pebbles, etc. into the cylinder (14). In order to further improve the sealing performance inside the cylinder (14), in the present invention, the ball screw shaft (38) and the pad pressing plate (40) are connected as follows.
[0021]
First, as shown in FIG. 1, the ball screw shaft (38) is formed in a hollow shape, provided with a hollow portion (41), and a fixed wall for fixing a mounting screw (42) on the friction pad (3) side. (49) is formed. Further, a bag-hole-like mounting hole (43) is recessed in the back surface of the pad pressing plate (40). Then, from the hollow portion (41) side of the ball screw shaft (38) to the mounting hole (43) of the pad pressing plate (40) through the fixing wall (49) of the ball screw shaft (38), 42) are screwed together to connect the ball screw shaft (38) and the pad pressing plate (40).
[0022]
With this configuration, the pad pressing plate (40) is not formed with any hole or the like for communicating the inside of the cylinder (14) and the outside on the friction pad (3) side. The connection between the plate (40) and the ball screw shaft (38) is made in the space covered with the pad pressing plate (40) and the dust seal (47). Therefore, the sealing performance of the opening (45) of the cylinder (14) is improved, and the entry of fine dust and a small amount of water droplets into the cylinder (14) from the friction pad (3) side can be surely prevented. . Further, since the pad pressing plate (40) and the ball screw shaft (38) can be connected from the rear side of the caliper body (8), the assembling property and the maintenance property are improved.
[0023]
Further, in this embodiment, in order to reduce the heat conduction of the outer surface of the caliper body (8), the caliper body (8) is connected to the friction pad (3) side and the reduction gear mechanism (17) side of the electric motor (15). As shown in FIG. 1, a heat insulating ring member (46) made of a heat insulating material having a lower thermal conductivity than that of the caliper body (8) is inserted and disposed between the parts. By this heat insulating ring member (46), the braking heat of the friction pads (3) and (4) is transmitted to the electric motor (15) and the reduction gear mechanism (17) through the outer surface of the caliper body (8). In addition, it is possible to prevent the drive heat of the electric motor (15) from being transmitted to the reduction gear mechanism (17).
[0024]
The heat insulating ring member (46) is formed by dividing the main body of the caliper body (8) and inserted between the parts, so that the heat insulating member is provided in the caliper body (8). Assembling is easy and does not affect productivity. Moreover, the assembling property and the maintenance property of various components inside the caliper body (8) can be improved by the division formation.
[0025]
Further, in this embodiment, as shown in FIG. 1, a load sensor (48) is provided at the tip of the ball screw shaft (38) so that the load applied to the friction pad (3) can be detected. A harness (50) for connecting the load sensor (48) and the detector main body (not shown) is inserted through the hollow portion (41) of the ball screw shaft (38) as shown in FIG. Further, the harness (50) is disposed in the hollow portion (41) with a sufficient length according to the moving distance of the ball screw shaft (38) moving forward and backward. However, there is a risk that the slack of the margin part may enter the gap between the parts and cause catching or cutting.
[0026]
In order to solve this problem, as shown in FIG. 1, the harness (50) is tensioned and biased by the pulling ridge (51), and the slack portion is always arranged in the hollow portion (41), so that the hollow portion (41) Outside, the harness (50) is always in a tensioned state. Even if the ball screw shaft (38) moves forward in the direction of the friction pad (3) and a tensile force is applied to the harness (50), the tension ridge (51) extends, so that the harness (50) is cut. The advance of the ball screw shaft (38) is not hindered. Further, when the ball screw shaft (38) is retracted, the tension ridge (51) is restored and contracted, so that the harness (50) is not loosened at a position other than the hollow portion (41).
[0027]
Further, in this embodiment, as shown in FIGS. 1 and 3, the back plate (27) faces the rear end face of the large diameter portion (21) of the planetary arm (18) and the parking mechanism solenoid (54). ). Then, when the vehicle is parked, braking is performed by the friction pads (3) and (4) and the solenoid (54) is operated, so that the locking pin (55) is the end surface of the large diameter portion (21) of the planetary arm (18). It engages with a locking hole (56) provided in. By this engagement, the planetary arm (18) is fixed so as not to rotate, and braking by the friction pads (3) and (4) can be maintained. A covering cover (44) is attached to the outer periphery of the back plate (27) to protect the solenoid (54), the back plate (27), and others from external impacts.
[0028]
In the present invention, the rotation angle of the planetary arm (18) is detected in order to adjust the pressing of the disk rotor (1) by the friction pads (3) and (4) during braking to enable appropriate braking. The rotation angle sensor is provided, and the drive of the brushless electric motor (15) can be controlled and the advance / retreat amount of the ball screw shaft (38) can be calculated by the rotation angle detected by the rotation angle sensor. In the present invention, as described above, the protrusion (52) provided on the large diameter portion (21) of the planetary arm (18) is used as the rotor of the rotation angle sensor. As shown in FIGS. 2 and 3, a stator is provided by arranging coils (19) circumferentially on the inner peripheral surface of the cylinder (14) so as to face the outer periphery of the protrusion (52). Yes.
[0029]
Since the triangular large diameter portion (21) rotates around the inner periphery of the coil (19), a waveform output voltage is generated due to the presence of the protrusion (52). Therefore, the protrusion (52) and the coil The rotation angle of the planetary arm (18) can be detected by the rotation angle sensor constituted by (19). Thus, since the large diameter portion (21) of the planetary arm (18) can be used as a rotor, it is not necessary to provide a rotation angle sensor rotor separately from the planetary arm (18). An increase in man-hours can be prevented.
[0030]
In addition, the installation space for the rotation angle sensor can be minimized, and in this embodiment, the electric motor (15) is further built in the caliper body (8), and the planetary gear (23) and the like are further incorporated. The reduction gear mechanism (17) is arranged not on the inner side of the electric motor (15) but on the rear side of the electric motor (15). Therefore, the caliper body (8) is neither long nor large in diameter, and can be formed compactly, increasing the degree of freedom of layout when installing the electric disc brake inside the tire wheel (5). It becomes.
[0031]
In the electric disc brake configured as described above, when the driver of the automobile depresses the brake pedal and performs a braking operation, the electric motor (15) is driven according to the amount of depression, and the planetary arm (18) is (14) Turn inside. Due to the rotation of the planetary arm (18), the planetary gear (23) that is pivotally supported by the large-diameter portion (21) and meshes with the first gear portion (24) in the sun gear (26) is the sun gear (26). Rotate the outer periphery of the. The rotation of the planetary gear (23) rotates the ball screw nut (34) that meshes with the reduction gear (35) in the second gear portion (25).
[0032]
Then, due to the action of the ball screw mechanism (16), the turning force is converted into a forward force in the direction of the friction pad (3) of the ball screw shaft (38), and the action portion (10) is provided via the pad pressing plate (40). The friction pad (3) on the side is pressed and slid and pressed against the disc rotor (1). Further, the caliper body (8) is retracted by the sliding reaction force of the ball screw shaft (38), and the reaction force claw (11) of the reaction portion (12) is moved to the friction pad (4) on the reaction portion (12) side. ) Is pressed and slid and pressed against the disc rotor (1) to perform braking.
[0033]
In the above braking, the driving force of the electric motor (15) is efficiently decelerated by the action of the reduction gear mechanism (17) and can be converted into a strong pressing force of the friction pads (3) and (4). Effective braking is possible. Then, by detecting the rotation angle of the planetary arm (18) at the time of braking with the rotation angle sensor, the advance / retreat amount of the ball screw shaft (38) can be calculated, and this advance / retreat amount and the load sensor (48) detect it. The electric motor (15) is controlled based on the data such as the pressing force of the friction pads (3) and (4) to adjust the pressing and sliding of the friction pads (3) and (4). Appropriate operation of the brake is possible.
[0034]
The means for calculating the amount of movement of the ball screw shaft (38) when the planetary arm (18) moves forward will be described based on the speed reduction effect of the speed reduction gear mechanism (17). For example, the sun gear (26 ) Of 72, the number of teeth of the first gear portion (24) of the planetary gear (23) meshing with the sun gear (26) is 15, the number of teeth of the second gear portion (25) is 12, The number of teeth of the reduction gear (35) of the ball screw nut (34) meshing with the two gear portion (25) is set to 60.
[0035]
First, when the planetary arm (18) makes one rotation in one direction by the electric motor (15), the planetary gear (23) pivotally supported on the planetary arm (18) makes one rotation around the outer periphery of the sun gear (26). . In this case, since the number of teeth of the sun gear (26) is 72 and the number of teeth of the first gear part (24) is 15, when the planetary gear (23) goes around the outer periphery of the sun gear (26). , 72 teeth / 15 teeth = 4.8 rotations in one direction. That is, the second gear portion (25) coaxial with the first gear portion (24) also rotates 4.8 in one direction. (Since the number of teeth of the second gear portion (25) is 12, it is a displacement of 4.8 rotations × 12 teeth = 57.6 teeth in one rotation.)
[0036]
On the other hand, a rotational force (for 60 teeth) in one direction acts on the ball screw nut (34) by the rotation of the planetary arm (18). Further, the second gear portion (25) meshing with the reduction gear (35) of the ball screw nut (34) causes the reduction gear (35) to be 4.8 × (12 teeth / (60 teeth) = 0.96 rotation force is applied (the number of teeth is equivalent to 57.6 teeth). When the rotational force in the one direction and the opposite direction is combined, 1 + (− 0.96) = 0.04 rotation (in the calculation with the number of teeth, the reduction gear (35) has 60 teeth + (− 57. 6) = 2.4 teeth are displaced in one direction, and the reduction gear (35) is 60 teeth, so 2.4 teeth / 60 teeth = 0.04 rotations). Accordingly, the ball screw nut (34) rotates 0.04 in the same direction with respect to one rotation in one direction of the planetary arm (18), and deceleration is performed at a ratio of 25: 1.
[0037]
Based on the above formula and the rotation angle of the planetary arm (18) detected by the rotation angle sensor and the dimensions of the ball screw shaft (38) and the ball screw nut (34), the ball screw shaft (38) The amount of movement at the time of advance can be calculated.
[0038]
When the depression of the brake pedal is released, the planetary arm (18) rotates reversely under the control of the electric motor (15), and the ball screw nut (34) is reversely rotated through the planetary gear (23). Since it rotates in the direction, the ball screw shaft (38) retreats and the friction pad (3) is released. Further, the caliper body (8) slides in the restoring direction by the reaction force of the retraction of the ball screw shaft (38), and the pressing of the friction pad (4) on the reaction portion (12) side is released, so that braking is performed. It is to be canceled. Further, by detecting the rotation angle of the planetary arm (18) at the time of releasing the brake with a rotation angle sensor, the amount of movement of the ball screw shaft (38) when retreating can be calculated and used as data for braking control. Will be.
[0039]
In the first embodiment, the protrusion (52) and the planetary gear (23) are provided at three locations on the outer periphery of the large-diameter portion (21), thereby forming a triangular large-diameter portion (21). In another different second embodiment, as shown in FIG. 5, the protrusion (52) and the planetary gear (23) are provided on the outer periphery of the large-diameter portion (21) at two equal intervals so as to have an elliptical large diameter. Part (21). In such a configuration, the number of planetary gears (23) to be used and the time and effort of assembly are reduced and the formation of the planetary arm (18) is easier than in the first embodiment in which the planetary gears (23) are provided at three locations. In fact, a lighter planetary arm (18) can be obtained.
[0040]
Further, in another different third embodiment, as shown in FIG. 6, the protrusions (52) and the planetary gear (23) are provided at four locations at equal intervals on the large diameter portion (21), and the cross-shaped large diameter portion is formed. (21). In this configuration, compared to the first and second embodiments, the number of parts and assembling work are increased, but the rotational stability when the planetary gear (23) rotates on the outer periphery of the sun gear (26) is more improved. As it increases, the waveform of the output voltage becomes a denser sine wave, and the detection accuracy of the rotation angle of the planetary arm (18) increases.
[0041]
【The invention's effect】
The present invention is configured as described above, and the rotation angle sensor for detecting the amount of advance / retreat of the advance / retreat mechanism is used as the planetary arm of the reduction gear mechanism for reducing the driving force of the electric motor and transmitting it to the advance / retreat mechanism. And a coil arranged facing a protrusion provided on the outer periphery of the planetary arm is configured as a stator. In this way, the planetary arm can be used as a rotor, and it is not necessary to provide a separate rotor for the rotation angle sensor on the caliper body, so the number of parts and the labor for assembly are not increased, and the rotation angle sensor can be simplified. It can be formed at a low price. Furthermore, since the installation space for the rotation angle sensor can be minimized, the caliper body can be made compact, and the degree of freedom in layout when installing the electric disc brake is increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an electric disc brake installed to face a disc rotor in an embodiment of the present invention.
2 is a cross-sectional view taken along line AA of FIG. 3, in which the sun gear fixing pin and the harness are omitted.
FIG. 3 is a partially enlarged cross-sectional view of the back plate side of FIG.
FIG. 4 is a perspective view of a reduction gear mechanism.
FIG. 5 is a cross-sectional view of a rotation angle sensor having two protrusions according to a second embodiment of the present invention, in which a sun gear fixing pin and a harness are omitted.
FIG. 6 is a cross-sectional view of a rotation angle sensor according to a third embodiment of the present invention, in which protrusions are provided at four locations, in which a sun gear fixing pin and a harness are omitted.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Disc rotor 3 Friction pad 4 Friction pad 8 Caliper body 15 Electric motor 17 Reduction gear mechanism 18 Planetary arm 19 Coil 23 Planetary gear 26 Sun gear 34 Ball screw nut 38 Ball screw shaft 52 Protrusion part

Claims (3)

The caliper body is provided with an advance / retreat mechanism that moves forward and backward with the driving force of the electric motor to generate a pressing force on the pressing member of the friction pad, and a reduction gear mechanism that decelerates and transmits the drive force of the electric motor to the advance / retreat mechanism. In an electric disc brake that performs braking by pressing and sliding a friction pad against a disc rotor by the advance / retreat mechanism, the magnet that can be rotated by an electric motor and that acts as a rotor of the electric motor. Is arranged on the outer periphery of the cylindrical portion, and a planetary arm having a large diameter portion larger than the cylindrical portion on the rear side opposite to the friction pad of the cylindrical portion and a projection portion on the large diameter portion is provided. A planetary gear rotatably supported on the outer periphery of the planetary arm, and a sun gear fixed to the caliper body so as not to rotate and rotating the planetary gear, and provided on the outer periphery of the planetary arm. With protrusions A rotation angle sensor is formed with a coil arranged circumferentially facing the outer periphery of the projection, and a waveform output voltage is generated in the coil as the projection passes, and the planetary arm is generated with the output voltage of the waveform. An electric disc brake characterized by being able to detect the rotation angle of the motor and calculating the advance / retreat amount of the advance / retreat mechanism. 2. The electric disc brake according to claim 1, wherein the planetary gear of the reduction gear mechanism is pivotally supported on a protrusion provided on the outer periphery of the planetary arm. The advancing / retracting mechanism includes a ball screw nut having a diameter larger than that of the planetary gear of the reduction gear mechanism and rotating by the rotation of the planetary gear, and a ball screw shaft that moves forward / backward by the rotation of the ball screw nut. By rotating a large ball screw nut with a planetary gear, the rotational force transmitted from the reduction gear mechanism is further decelerated, and a pressing force is generated on the pressing member via the ball screw shaft. The electric disc brake according to claim 1 or 2, characterized in that:

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