Electric braking device

Abstract

To provide an electric brake device capable of suppressing deterioration in durability of a component part of a device.SOLUTION: An electric brake device 40 comprises an actuator 80 which, in the case that a piston 72 moves in a second direction D2 being a direction of decreasing a brake force due to an external force so that an electric motor 50 rotates in a second rotational direction R2, uses electric power generated by the electric motor 50 according to rotation of the electric motor 50 in the second rotational direction R2 in order to drive the piston 72 so as to suppress its movement in the second direction D2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electric braking device. [Background technology]

[0002] Patent Document 1 discloses an electric braking device that generates braking force through the linear motion of a piston in a cylinder powered by an electric motor. Such electric braking devices include wet-type electric braking devices that generate braking force by transmitting the pressure of the piston to a friction member via brake fluid, and dry-type electric braking devices that generate braking force by directly transmitting the pressure of the piston to a friction member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Patent Application Publication No. 102009019209 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric braking device described above, if the electric motor loses power due to a power failure or other reason while generating braking force, the piston is pushed back. The impact caused when the piston hits the end of its linear motion range within the cylinder can reduce the durability of the components of the electric braking device. [Means for solving the problem]

[0005] The means for solving the above problems and their effects will be described below. The electric braking device that solves the above problems transmits the rotational motion generated by the electric motor rotating in the braking force increasing direction to the linear motion conversion mechanism by the transmission mechanism, and the linear motion conversion mechanism converts the rotational motion into a linear motion that drives a piston provided in the cylinder, and generates a braking force on the vehicle by pressing against a friction portion that rotates with the wheels of the vehicle. When the piston moves in the decreasing direction, which is the direction in which the braking force decreases due to an external force, and the electric motor rotates in the braking force decreasing direction, which is the opposite direction to the braking force increasing direction, the electric motor rotates in the braking force decreasing direction, and an actuator is provided to drive the piston to suppress its movement in the decreasing direction by using the electric power generated by the electric motor.

[0006] When the power supply to the electric motor is cut off while the electric braking device is generating a braking force, the piston may be vigorously pushed back in the decreasing direction by an external force. At this time, since the electric motor rotates in the braking force decreasing direction, the electric motor generates electricity. Then, the actuator is driven by the electric power generated by the electric motor, so that the moving speed of the piston in the decreasing direction is decelerated. In this way, the electric control device can mitigate the impact when the piston hits the end in the decreasing direction within the moving range of the piston. As a result, the electric braking device can suppress a decrease in the durability of the components of the device.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0008] (First Embodiment) Hereinafter, a vehicle including the electric braking device according to the first embodiment will be described. <Vehicle> As shown in FIG. 1, the vehicle 10 includes wheels 20, a braking mechanism 30, and an electric braking device 40. FIG. 1 shows a part of the components of the vehicle 10.

[0009] <Braking Mechanism> The braking mechanism 30 includes a brake rotor 31 that rotates together with the wheel 20, a friction member 32 that does not rotate integrally with the wheel 20, and a wheel cylinder 33 that displaces the friction member 32 toward the brake rotor 31 according to hydraulic pressure. The wheel cylinder 33 is connected to the electric braking device 40 via a liquid passage 34. The braking mechanism 30 applies a greater braking force to the wheel 20 by pressing the friction member 32 more strongly against the brake rotor 31 as the hydraulic pressure in the wheel cylinder 33 increases. The brake rotor 31 corresponds to an example of a "friction target part", and the friction member 32 corresponds to an example of a "friction part".

[0010] <Mechanical Configuration of Electric Braking Device> The electric braking device 40 includes an electric motor 50, a transmission device 60, an electric cylinder mechanism 70, and an actuator 80.

[0011] The electric motor 50 is a brushless DC motor and includes a stator 51, a rotor 52, and an output shaft 53. The stator 51 includes a u-phase coil, a v-phase coil, and a w-phase coil. By controlling the energization of each coil, the rotor 52 and the output shaft 53 rotate in a first rotation direction R1 or a second rotation direction R2 that is the reverse of the first rotation direction R1. A ratchet gear 531 is fixed to the output shaft 53. The ratchet gear 531 rotates together with the output shaft 53.

[0012] The transmission device 60 transmits power between the electric motor 50 and the electric cylinder mechanism 70. The transmission device 60 includes a speed reduction mechanism 61 that reduces the rotational speed of the output shaft 53 of the electric motor 50, and a linear motion conversion mechanism 65 that converts rotational motion into linear motion. When the electric motor 50 is driven in the transmission device 60, the power of the electric motor 50 is transmitted from the speed reduction mechanism 61 to the linear motion conversion mechanism 65 and output to the electric cylinder mechanism 70.

[0013] The speed reduction mechanism 61 includes a first gear 62 fixed to the output shaft 53 of the electric motor 50, and a second gear 63 that meshes with the first gear 62. Since the number of teeth of the second gear 63 is larger than the number of teeth of the first gear 62, the rotational speed of the second gear 63 is slower than the rotational speed of the first gear 62. In this example, there are two gears, but the speed reduction mechanism 61 may be configured by meshing three or more gears. In this regard, the speed reduction mechanism 61 corresponds to a "transmission mechanism", and the second gear 63 corresponds to a "speed reduction part". In FIG. 1, the rotational axis of the first gear 62 and the rotational axis of the second gear 63 are in a parallel positional relationship, but the rotational axis of the first gear 62 and the rotational axis of the second gear 63 may be in a twisted positional relationship.

[0014] The linear motion conversion mechanism 65 is, for example, a ball screw mechanism or a feed screw mechanism. The linear motion conversion mechanism 65 includes a rotating member 66 that rotates based on the power transmitted from the speed reduction mechanism 61, and a linear motion member 67 that moves in the axial direction of the rotating member 66 as the rotating member 66 rotates.

[0015] The rotating member 66 includes a third gear 661 that meshes with the second gear 63 of the speed reduction mechanism 61, and a screw shaft 662 that extends in the axial direction of the third gear 661 from the third gear 661. The linear motion member 67 is non-rotatable around the axis of the rotating member 66 and is movable in the axial direction of the rotating member 66. In the linear motion conversion mechanism 65, when the rotating member 66 rotates, the linear motion member 67 moves in the axial direction of the rotating member 66.

[0016] The electric cylinder mechanism 70 includes an electric cylinder 71, a piston 72 housed in the electric cylinder 71, and a stopper 73 that defines the moving range of the piston 72. Further, the electric cylinder mechanism 70 has a liquid chamber 74 partitioned by the electric cylinder 71 and the piston 72.

[0017] The electric cylinder 71 houses the screw shaft 662 and the linear movement member 67 together with the piston 72. Inside the electric cylinder 71, the piston 72 and the linear movement member 67 are connected. Therefore, when the linear movement member 67 moves in the axial direction of the electric cylinder 71, the piston 72 moves in the first direction D1 or the second direction D2, which is the reverse direction of the first direction D1, together with the linear movement member 67. In this regard, the linear movement of the linear movement member 67 is a linear movement that drives the piston 72.

[0018] The stopper 73 defines the end in the second direction D2 of the moving range of the piston 72. In the present embodiment, when the linear movement member 67 that moves in the second direction D2 together with the stopper 73 contacts the stopper 73, the movement of the piston 72 in the second direction D2 is restricted. The stopper 73 can be constituted by the wall portion of the electric cylinder 71 or can be constituted by a separate member from the electric cylinder 71.

[0019] The liquid chamber 74 is filled with brake fluid. The liquid chamber 74 is connected to the wheel cylinder 33 of the braking mechanism 30 via a liquid passage 34. When the piston 72 moves in the first direction D1 that reduces the volume of the liquid chamber 74, the brake fluid flows out from the liquid chamber 74 toward the wheel cylinder 33. On the other hand, when the piston 72 moves in the second direction D2 that increases the volume of the liquid chamber 74, the brake fluid flows into the liquid chamber 74 from the wheel cylinder 33.

[0020] In the electric braking device 40 described above, when the output shaft 53 of the electric motor 50 rotates, the power of the electric motor 50 is transmitted to the piston 72 via the transmission device 60. When the output shaft 53 of the electric motor 50 rotates in the first rotation direction R1, that is, when the piston 72 moves in the first direction D1, the brake fluid flows into the wheel cylinder 33, so the hydraulic pressure of the wheel cylinder 33 increases. That is, the force with which the friction member 32 presses the brake rotor 31 increases, and the braking force applied to the wheel 20 increases. On the other hand, when the output shaft 53 of the electric motor 50 rotates in the second rotation direction R2, that is, when the piston 72 moves in the second direction D2, the brake fluid flows out of the wheel cylinder 33, so the hydraulic pressure of the wheel cylinder 33 decreases. That is, the force with which the friction member 32 presses the brake rotor 31 decreases, and the braking force applied to the wheel 20 decreases. In this regard, the first rotation direction R1 corresponds to the "braking force increasing direction", and the first direction D1 corresponds to the "increasing direction". On the other hand, the second rotation direction R2 corresponds to the "braking force decreasing direction", and the second direction D2 corresponds to the "decreasing direction".

[0021] The actuator 80 is a so-called solenoid actuator. The actuator 80 includes a columnar plunger 81, a coil 82 that generates a magnetic field for driving the plunger 81, and a housing 83 that houses the plunger 81 and the coil 82. The tip of the plunger 81 has a claw shape that can be locked to the ratchet gear 531. When the coil 82 is energized, it generates a magnetic field for driving the plunger 81. In the present embodiment, when the coil 82 is not energized, the plunger 81 is located at the housing position housed in the housing 83. On the other hand, when the coil 82 is energized, the plunger 81 is located at the protruding position protruding from the housing 83. When the state of energizing the coil 82 is maintained, the plunger 81 continues to be located at the protruding position.

[0022] The actuator 80 is arranged such that the protruding direction of the plunger 81 faces the ratchet gear 531 fixed to the output shaft 53 of the electric motor 50. As shown by the solid line in FIG. 1, when the plunger 81 is arranged at the housing position, the plunger 81 does not lock to the ratchet gear 531. On the other hand, as shown by the two-dot chain line in FIG. 1, when the plunger 81 is arranged at the protruding position, the plunger 81 locks to the ratchet gear 531. When the plunger 81 is arranged at the protruding position under the situation where the output shaft 53 of the electric motor 50 is rotating, the rotation speed of the output shaft 53 greatly decreases. In this way, the actuator 80 strongly obstructs the rotation of the output shaft 53 by locking the plunger 81 to the ratchet gear 531. Note that the ratchet gear 531 may have a configuration that obstructs the rotation of the output shaft 53 by locking to the plunger 81 under the situation where the output shaft 53 is rotating at least in the second rotation direction R2.

[0023] <Electrical Configuration of Electric Braking Device> As shown in FIG. 2, the electric braking device 40 includes a DC power supply 90, a positive electrode line 91 and a negative electrode line 92, a first drive circuit 110, a second drive circuit 120, a control device 130, and a switching element 140.

[0024] The positive electrode line 91 is connected to the positive electrode of the DC power supply 90. The negative electrode line 92 is connected to the negative electrode of the DC power supply 90. The first drive circuit 110 is an inverter circuit that drives the electric motor 50. The first drive circuit 110 has a plurality of switching elements 111u, 112u, 111v, 112v, 111w, 112w.

[0025] Among the plurality of switching elements, switching elements 111u, 111v, and 111w are connected to the positive electrode line 91, and switching elements 112u, 112v, and 112w are connected to the negative electrode line 92. Two switching elements 111u and 112u correspond to the u-phase coil of the electric motor 50. Two switching elements 111v and 112v correspond to the v-phase coil of the electric motor 50. Two switching elements 111w and 112w correspond to the w-phase coil of the electric motor 50.

[0026] The first drive circuit 110 converts the DC power input from the DC power supply 90 into AC power by periodically turning on and off a plurality of switching elements 111u, 112u, 111v, 112v, 111w, and 112w. In this way, the first drive circuit 110 supplies AC power to the u-phase coil, v-phase coil, and w-phase coil of the electric motor 50.

[0027] The second drive circuit 120 is a circuit that drives the actuator 80. The second drive circuit 120 includes a first connection line 121, a second connection line 122, a switching element 123, a switching circuit 124, a diode 125, and a capacitor 126. Further, a coil 82 of the actuator 80 is provided in the second drive circuit 120.

[0028] The first connection line 121 connects the positive electrode line 91 and the negative electrode line 92. The second connection line 122 connects the first connection line 121 and the negative electrode line 92. The coil 82 and the switching element 123 are provided in series on the second connection line 122. The switching element 123 switches the energization state of the coil 82. Specifically, when the switching element 123 is on, the coil 82 is energized, and when the switching element 123 is off, the coil 82 is not energized. The switching element 123 is, for example, a MOSFET.

[0029] The switching circuit 124 is a circuit that controls the on / off of the switching element 123. The switching circuit 124 controls the switching element 123 based on the identification signal output from the control device 130. The identification signal output from the control device 130 to the switching circuit 124 is a signal indicating whether the power supply to the electric motor 50 is normal or not. The identification signal when the power supply to the electric motor 50 is normal is defined as a normal signal, and the identification signal when the power supply to the electric motor 50 is abnormal is defined as an abnormal signal. At this time, when the identification signal is a normal signal, the switching circuit 124 turns off the switching element 123. In other words, the switching circuit 124 prohibits the switching element 123 from turning on from off. On the other hand, when the identification signal is an abnormal signal, the switching circuit 124 allows the switching element 123 to turn on from off. In this case, when a current flows from the first connection line 121 to the switching circuit 124, the switching circuit 124 turns on the switching element 123. The switching circuit 124 corresponds to an example of a "switching unit". Note that the case where the identification signal is an abnormal signal is, for example, the case where a power failure occurs in the DC power supply 90.

[0030] The diode 125 is provided on the first connection line 121. Specifically, when the connection point between the first connection line 121 and the positive electrode line 91 is defined as connection point P1, and the connection point between the first connection line 121 and the second connection line 122 is defined as connection point P2, the diode 125 is provided in the portion of the first connection line 121 between connection point P1 and connection point P2. The diode 125 allows the current to flow from connection point P1 to connection point P2, and restricts the current from flowing from connection point P2 to connection point P1.

[0031] The capacitor 126 is provided on the first connection line 121. Specifically, when the connection point between the first connection line 121 and the switching circuit 124 is defined as connection point P3 and the connection point between the first connection line 121 and the negative electrode line 92 is defined as connection point P4, the capacitor 126 is provided on the portion of the first connection line 121 between connection point P3 and connection point P4. The capacitor 126 charges when current flows from connection point P1 to connection point P3 in the first connection line 121. When the current stops flowing in the first connection line 121 while the capacitor 126 stores charge, the capacitor 126 discharges toward the switching circuit 124. The capacitor 126 corresponds to the "power supply unit".

[0032] The switching element 140 is provided in the path between the DC power supply 90 and the connection point P1. The switching element 140 is turned off when the electric braking device 40 is abnormal. Thereby, for example, when the voltage of the DC power supply 90 drops, it is possible to suppress the power generated by the electric motor 50 from being supplied to the DC power supply 90.

[0033] The control device 130 controls the first drive circuit 110 based on a control signal output from a braking control device that calculates a required braking force required for the vehicle 10. The control device 130 adjusts the rotational speed and rotational direction of the output shaft 53 of the electric motor 50 by periodically turning on / off a plurality of switching elements 111u, 112u, 111v, 112v, 111w, 112w. In this way, the control device 130 adjusts the braking force applied to the wheels 20. Further, the control device 130 outputs the above-described identification signal toward the switching circuit 124.

[0034] <Operations and Effects of the First Embodiment> When a control signal corresponding to a required braking force is input from the braking control device to the electric braking device 40, the first drive circuit 110 is driven. When the required braking force is increased, the output shaft 53 of the electric motor 50 is rotated in the first rotation direction R1. Then, as the piston 72 moves in the first direction D1, the brake fluid flows out from the liquid chamber 74 of the electric cylinder 71 to the wheel cylinder 33. As a result, the hydraulic pressure of the wheel cylinder 33 increases, and the braking force applied to the wheel 20 increases.

[0035] Also, when power is normally supplied to the first drive circuit 110 and the second drive circuit 120, the switching element 123 of the second drive circuit 120 is turned off. For this reason, no current flows through the second connection line 122, and the coil 82 is not energized. That is, when the power supply to the electric motor 50 is normal, the switching circuit 124 prohibits the operation of the actuator 80. As a result, the plunger 81 of the actuator 80 is arranged at the storage position. On the other hand, since current flows through the first connection line 121, the capacitor 126 is charged.

[0036] By the way, when an abnormality occurs in the DC power supply 90 in a situation where the electric braking device 40 applies a braking force to the wheel 20, power may not be normally supplied to the first drive circuit 110, the second drive circuit 120, and the control device 130.

[0037] When power supply to the first drive circuit 110 stops, the electric motor 50 cannot be driven, so the force pushing the piston 72 in the first direction D1 disappears. Then, as the brake fluid flows from the wheel cylinder 33 into the liquid chamber 74 of the electric cylinder 71, the piston 72 moves in the second direction D2. That is, the piston 72 moves in the second direction D2 by an external force.

[0038] When the piston 72 moves in the second direction D2, based on the power transmitted from the piston 72, the output shaft 53 of the electric motor 50 rotates in the second rotation direction R2. As a result, the electric motor 50 generates electricity. Then, a current flows from the electric motor 50 to the positive electrode line 91 through the freewheeling diodes of the switching elements 111u, 111v, 111w. As a result, the electric power generated by the electric motor 50 is supplied to the second drive circuit 120. When the output shaft 53 of the electric motor 50 rotates in the second rotation direction R2, since the rotor 52 of the electric motor 50 also rotates in the second rotation direction R2, an inertia moment occurs. For this reason, even if the flow rate of the brake fluid flowing from the wheel cylinder 33 into the liquid chamber 74 of the electric cylinder 71 decreases, due to the inertia moment of the rotor 52, the piston 72 continues to move in the second direction D2.

[0039] When power supply from the DC power source 90 to the second drive circuit 120 and the control device 130 stops, the switching circuit 124 permits the switching element 123 to turn on based on the identification signal output from the control device 130. When power is supplied from the first drive circuit 110 to the second drive circuit 120 due to the power generation of the electric motor 50 under such circumstances, a current starts to flow from the first connection line 121 to the switching circuit 124. As a result, the switching circuit 124 turns on the switching element 123. Then, a current flows through the second connection line 122 and energizes the coil 82. In this way, when the power supply to the electric motor 50 is abnormal, the switching circuit 124 permits the operation of the actuator 80.

[0040] As shown by the solid line and the two-dot chain line in FIG. 1, when the coil 82 is energized, the plunger 81 of the actuator 80 is displaced from the retracted position to the protruding position. Then, when the plunger 81 engages with the ratchet gear 531, the rotational speed of the output shaft 53 of the electric motor 50 decreases. In this way, the actuator 80 uses the electric power generated by the electric motor 50 to suppress the movement of the piston 72 in the second direction D2. Therefore, the piston 72 is prevented from being vigorously pushed back in the second direction D2, and the impact when the piston 72 hits at the end of the second direction D2 in the movement range of the piston 72 can be mitigated. Specifically, the impact when the linear member 67 moving in the second direction D2 together with the piston 72 hits the stopper 73 can be mitigated. As a result, the electric braking device 40 can prevent the durability of the components of the device from decreasing.

[0041] The first embodiment can further obtain the following effects. (1) The second drive circuit 120 has a capacitor 126. When power is being supplied from the DC power source 90 to the second drive circuit 120, the capacitor 126 is fully charged. For this reason, when power is no longer supplied from the DC power source 90 to the second drive circuit 120 and no current flows through the first connection line 121, the capacitor 126 promptly starts discharging to the switching circuit 124. In other words, the capacitor 126 supplies power to the switching circuit 124 when the power supply to the electric motor 50 is abnormal. In this way, when power is no longer supplied from the DC power source 90 to the first drive circuit 110 and the second drive circuit 120, the electric braking device 40 can promptly turn on the switching element 123. Therefore, the electric braking device 40 can promptly start the operation of the actuator 80.

[0042] (2) The actuator 80 obstructs the rotation of the output shaft 53 of the electric motor 50 before being decelerated by the speed reduction mechanism 61. In other words, the actuator 80 obstructs the operation on the side of the electric motor 50 rather than the second gear 63 of the speed reduction mechanism 61 in the transmission path of the output torque of the electric motor 50. For this reason, for example, when the actuator 80 is configured to obstruct the rotation of the rotating body after being decelerated by the speed reduction mechanism 61, the movement of the piston 72 in the second direction D2 can be suppressed more efficiently.

[0043] (Second Embodiment) Hereinafter, the electric braking device 40A according to the second embodiment will be described. In the description of the second embodiment, components common to the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0044] <Electric Braking Device> As shown in FIG. 3, the electric braking device 40A includes an electric motor 50, a transmission device 60, an electric cylinder mechanism 70, and a plurality of actuators 80A1 to 80A3. The electrical configuration of the electric braking device 40A is substantially the same as that of the first embodiment except that three coils 82 are arranged in series on the second connection line 122 of the second drive circuit 120.

[0045] The plurality of actuators 80A1 to 80A3 are configured substantially the same as the actuator 80 in the first embodiment. In the second embodiment, the tip of the plunger 81 does not have to be claw-shaped in that the engagement target of the plunger 81 is not the ratchet gear 531. The first actuator 80A1 is arranged such that the rotor 52 of the electric motor 50 is positioned in the protruding direction of the plunger 81. The second actuator 80A2 is arranged such that the first gear 62 of the speed reduction mechanism 61 is positioned in the protruding direction of the plunger 81. The third actuator 80A3 is arranged such that the linear motion member 67 of the linear motion conversion mechanism 65 is positioned in the protruding direction of the plunger 81.

[0046] <Operations and Effects of the Second Embodiment> When power supply from the DC power source 90 to the first drive circuit 110 and the second drive circuit 120 stops, the power generated by the electric motor 50 is supplied to the second drive circuit 120, causing the plurality of actuators 80A1 to 80A3 to be driven.

[0047] Specifically, the first actuator 80A1 obstructs the rotation of the rotor 52 of the electric motor 50 by bringing the plunger 81 into contact with the rotor 52 of the electric motor 50. That is, due to the friction between the plunger 81 of the first actuator 80A1 and the rotor 52, the rotational speed of the output shaft 53 decreases. The second actuator 80A2 obstructs the rotation of the first gear 62 by bringing the plunger 81 into contact with the first gear 62 of the speed reduction mechanism 61. That is, due to the friction between the plunger 81 of the second actuator 80A2 and the first gear 62, the rotational speed of the output shaft 53 decreases. The third actuator 80A3 obstructs the movement of the plunger 81 by bringing the plunger 81 into contact with the linear member 67 of the linear conversion mechanism 65. That is, due to the friction between the plunger 81 of the third actuator 80A3 and the linear member 67, the moving speed of the linear member 67 decreases. In this way, the electric braking device 40A can suppress the movement of the piston 72 in the second direction D2. That is, the electric braking device 40A can suppress the reduction in the durability of the components of the device.

[0048] In the second embodiment, the electric braking device 40A only needs to include at least one actuator among the plurality of actuators 80A1 to 80A3. Also, in the second embodiment, the electric braking device 40A only needs to include an actuator that obstructs the operation of a power transmission element that constitutes a part of the power transmission path from the electric motor 50 to the piston 72. For example, the electric braking device 40A may include an actuator that obstructs the rotation of the second gear 63 of the speed reduction mechanism 61, or may include an actuator that obstructs the rotation of the rotating member 66 of the linear conversion mechanism 65. Further, the electric braking device 40A may include an actuator that obstructs the operation of the piston 72.

[0049] (Third Embodiment) Hereinafter, the electric braking device 40B according to the third embodiment will be described. In the description of the third embodiment, components common to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0050] <Electric braking device> As shown in FIG. 4, the electric braking device 40B includes an electric motor 50, a transmission device 60, an electric cylinder mechanism 70, and an actuator 80B. The electrical configuration of the electric braking device 40B is substantially the same as that of the first embodiment.

[0051] The actuator 80B is a normally open solenoid valve provided in a liquid passage 34 that connects the liquid chamber 74 and the wheel cylinder 33. The actuator 80B has a coil 82B that generates a magnetic field for driving the actuator 80B. When the actuator 80B is open, the movement of the brake fluid is possible between the liquid chamber 74 and the wheel cylinder 33. When the actuator 80B is closed, the movement of the brake fluid between the liquid chamber 74 and the wheel cylinder 33 becomes impossible. When the actuator 80B is closed, since the brake fluid is sealed in the wheel cylinder 33, a liquid passage for discharging the sealed brake fluid may be provided between the wheel cylinder 33 and the actuator 80B.

[0052] <Operation and effects of the third embodiment> When power supply from the DC power source 90 to the first drive circuit 110 and the second drive circuit 120 stops, the power generated by the electric motor 50 is supplied to the second drive circuit 120, thereby driving the actuator 80B. Specifically, since the actuator 80B closes, the brake fluid does not flow from the wheel cylinder 33 into the liquid chamber 74 of the electric cylinder 71. In other words, the actuator 80B weakens the flow of the brake fluid from the wheel cylinder 33 to the piston 72 of the electric cylinder 71. Thus, the electric braking device 40B can suppress the movement of the piston 72 in the second direction D2. That is, the electric braking device 40B can suppress a decrease in the durability of the components of the device.

[0053] (Fourth Embodiment) Hereinafter, the electric braking device 40C according to the fourth embodiment will be described. In the description of the fourth embodiment, components common to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0054] <Electric Braking Device> As shown in FIG. 5, the vehicle 10 includes an atmospheric pressure reservoir 35 that stores brake fluid, and a liquid passage 36 that connects the liquid passage 34 and the atmospheric pressure reservoir 35. The internal pressure of the atmospheric pressure reservoir 35 is equivalent to the atmospheric pressure. The electric braking device 40C includes an electric motor 50, a transmission device 60, an electric cylinder mechanism 70, and an actuator 80C. Note that the electrical configuration of the electric braking device 40C is substantially the same as that of the first embodiment.

[0055] The actuator 80C is a normally-closed solenoid valve provided in the liquid passage 36. The actuator 80C has a coil 82C that generates a magnetic field for driving the actuator 80C. When the actuator 80C is closed, the movement of the brake fluid between the wheel cylinder 33 and the liquid chamber 74 and the atmospheric pressure reservoir 35 becomes impossible. When the actuator 80C is open, the movement of the brake fluid between the wheel cylinder 33 and the liquid chamber 74 and the atmospheric pressure reservoir 35 becomes possible.

[0056] <Operation and Effects of the Fourth Embodiment> When power supply from the DC power source 90 to the first drive circuit 110 and the second drive circuit 120 stops, the power generated by the electric motor 50 is supplied to the second drive circuit 120, thereby driving the actuator 80C. Specifically, since the actuator 80C is opened, a part of the brake fluid flowing from the wheel cylinder 33 toward the liquid chamber 74 of the electric cylinder 71 flows out to the atmospheric pressure reservoir 35. In other words, the actuator 80C weakens the flow of the brake fluid from the wheel cylinder 33 to the piston 72 of the electric cylinder 71. Thus, the electric braking device 40C can suppress the movement of the piston 72 in the second direction D2. That is, the electric braking device 40C can suppress a decrease in the durability of the components of the device.

[0057] (Fifth Embodiment) Hereinafter, the electric braking device 40D according to the fifth embodiment will be described. In the description of the fifth embodiment, components common to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0058] <Electric Braking Device> As shown in FIG. 6, the electric braking device 40D includes an electric motor 50, a transmission device 60, an electric cylinder mechanism 70, and an actuator 80D. The electrical configuration of the electric braking device 40D is substantially the same as that of the first embodiment.

[0059] The electric cylinder mechanism 70 includes a first liquid chamber 74 partitioned into an electric cylinder 71 and a piston 72, a second liquid chamber 75 partitioned into a linear member 67, the electric cylinder 71, and a stopper 73, and a liquid passage 76 connecting the first liquid chamber 74 and the second liquid chamber 75. In the fifth embodiment, the stopper 73 also functions as a seal that closes the gap between the electric cylinder 71 and the screw shaft 662 of the rotating member 66. When the braking force is applied to the wheel 20 by the operation of the electric cylinder mechanism 70, the internal pressure of the second liquid chamber 75 is lower than the internal pressure of the first liquid chamber 74.

[0060] The actuator 80D is provided in the liquid passage 76. The actuator 80D is a normally closed solenoid valve. The actuator 80D has a coil 82D that generates a magnetic field for driving the actuator 80D. When the actuator 80D is closed, the movement of the brake fluid between the first liquid chamber 74 and the second liquid chamber 75 becomes impossible. When the actuator 80D is open, the movement of the brake fluid between the first liquid chamber 74 and the second liquid chamber 75 becomes possible.

[0061] <Operations and Effects of the Fifth Embodiment> When power supply from the DC power supply 90 to the first drive circuit 110 and the second drive circuit 120 stops, the power generated by the electric motor 50 is supplied to the second drive circuit 120, thereby driving the actuator 80D. Specifically, since the actuator 80D is opened, a part of the brake fluid flowing from the wheel cylinder 33 into the first fluid chamber 74 flows out into the second fluid chamber 75. Thus, the electric braking device 40D can suppress the movement of the piston 72 in the second direction D2. That is, the electric braking device 40D can suppress a decrease in the durability of the components of the device.

[0062] (Modified example) The above-described plurality of embodiments can be implemented with the following modifications. The above-described plurality of embodiments and the following modified examples can be implemented in combination with each other within a technically non-conflicting range.

[0063] · The electric braking devices 40, 40A to 40D may be dry-type devices that displace the friction member 32 relative to the brake rotor 31 without using brake fluid. Specifically, the electric braking devices 40, 40A to 40D may be configured to press the friction member 32 against the brake rotor 31 by directly pushing the friction member 32 with the piston 72.

[0064] · The electric braking device 40 may not include the ratchet gear 531. And the actuator 80 may reduce the rotational speed of the output shaft 53 by bringing the plunger 81 into contact with the output shaft 53 of the electric motor 50. In this case, a process for increasing the friction between the plunger 81 and the output shaft 53 may be performed on the tip of the plunger 81 and the outer peripheral surface of the output shaft 53, or an uneven shape may be provided on the outer peripheral surface of the output shaft 53.

[0065] · The speed reduction mechanism 61 may transmit the output of the electric motor 50 to the linear motion conversion mechanism 65 without reducing the rotational speed of the output shaft 53 of the electric motor 50. · The electric cylinder 71 may include an elastic body such as a coil spring that biases the piston 72 in the second direction D2.

[0066] · The actuator 80 does not have to be a solenoid actuator as long as it is an actuator driven by the electric power generated by the electric motor 50. For example, the actuator 80 may be constituted by an electric motor.

[0067] · The actuator 80 may be a rotary actuator instead of a linear actuator. · The electric motor 50 may be a brushed motor or an AC motor. In these cases, it is preferable to appropriately change the configuration of the drive circuit.

[0068] · The circuit configuration of the second drive circuit 120 can be appropriately changed. The second drive circuit 120 only needs to be configured to be able to supply the electric power generated by the electric motor 50 to the actuator 80 when the electric motor 50 generates electric power.

[0069] · If an electric current can flow through the switching circuit 124 when the electric motor 50 generates electric power, the second drive circuit 120 does not have to include the capacitor 126. · When the power supply source for the control device 130 is the DC power supply 90, the identification signal only needs to be a signal that is always on when power is supplied to the control device 130. According to this, when the DC power supply 90 cannot supply power normally, in other words, when the identification signal cannot be transmitted to the switching circuit 124 because power is not supplied to the control device 130, the above signal automatically turns off. Therefore, the switching circuit 124 can select the on / off state of the switching element 123 according to whether the identification signal is transmitted from the control device 130.

Explanation of Reference Numerals

[0070] 10…Vehicle 20…Wheel 30…Brake mechanism 31…Brake rotor 32…Friction member 33…Wheel cylinder 34…Hydraulic passage 40, 40A~40D…Electric braking device 50… Electric motor 53… Output shaft 60… Transmission device 61… Reduction mechanism (transmission mechanism) 62… First gear 63… Second gear (reduction part) 65… Linear conversion mechanism 70… Electric cylinder mechanism 71… Electric cylinder 72… Piston 80, 80A1~80A3, 80B~80D… Actuator 82, 82B~82D… Coil 90… DC power supply (an example of power supply) 110… First drive circuit 120… Second drive circuit 123… Switching element 124… Switching circuit (switching part) 126… Capacitor (power supply part) R1… First rotation direction (braking force increasing direction) R2… Second rotation direction (braking force decreasing direction) D1… First direction (increasing direction) D2… Second direction (decreasing direction)

Claims

1. A rotational motion generated by rotating an electric motor in a braking force increasing direction is transmitted by a transmission mechanism to a linear motion conversion mechanism, and the linear motion conversion mechanism converts the rotational motion into a linear motion for driving a piston provided in a cylinder, and a braking force is generated for the vehicle by pressing a friction portion against a friction-applied portion that rotates together with a wheel of the vehicle. The electric braking device is configured such that: when the piston moves in a decreasing direction, which is a direction in which the braking force decreases due to an external force, and the electric motor rotates in a braking force decreasing direction, which is opposite to the braking force increasing direction, an actuator is provided that drives the electric motor to rotate in the braking force decreasing direction and uses electric power generated by the electric motor to suppress the movement of the piston in the decreasing direction. An electric braking device.

2. The actuator suppresses the movement of the piston in the decreasing direction by preventing the operation of at least one of the electric motor, the transmission mechanism, the linear motion conversion mechanism, and the piston. The electric braking device according to claim 1.

3. The transmission mechanism includes a speed reduction unit that reduces the rotation of the electric motor and transmits it to the linear motion conversion mechanism. The actuator suppresses the movement of the piston in the decreasing direction by preventing the operation of the electric motor side of the transmission mechanism from the speed reduction unit in the transmission path of the output torque of the electric motor. The electric braking device according to claim 1 or claim 2.

4. The electric braking device supplies brake fluid to a wheel cylinder to press the friction portion against the friction-applied portion. The actuator suppresses the movement of the piston in the decreasing direction by weakening the flow of brake fluid from the wheel cylinder to the piston in the cylinder. The electric braking device according to claim 1.

5. The electric braking device has a switching unit that prohibits the operation of the actuator when the power supply to the electric motor is normal and permits the operation of the actuator when the power supply to the electric motor is abnormal. The electric braking device according to any one of claims 1 to 4.

6. The electric braking device has a power supply unit that supplies power to the switching unit when the power supply to the electric motor is abnormal. The electric braking device according to claim 5.

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