JP4495621B2 - Electric brake device for vehicle - Google Patents

Description

The present invention relates to an electric brake device for a vehicle that generates a braking force by pressing a friction member that moves forward and backward by an electric actuator against a rotating member that rotates together with a wheel.

The electric drive brake device that presses the pad with the electric actuator and makes sliding contact with the disc rotor increases the clearance generated between the pad and the disc rotor more than when it is off when the accelerator pedal is on. Japanese Patent Application Laid-Open No. 2004-151867 discloses a technique for improving braking response while reducing drag resistance caused by contact with a rotor.
JP 2000-18293 A

  However, since the clearance between the pad and the disc rotor is controlled according to whether the accelerator pedal is on or off, the one described in the above-mentioned Patent Document 1 ensures sufficient clearance at high vehicle speeds when drag resistance increases. As a result, there has been a problem that the fuel saving effect cannot be obtained sufficiently.

The present invention has been made in view of the above circumstances, and an object thereof is to reduce drag resistance due to contact between a rotating member and a friction member to the maximum while minimizing a decrease in responsiveness of an electric brake device for a vehicle. And

In order to achieve the above object, according to the first aspect of the present invention, in the vehicle electric brake device for generating a braking force by pressing the friction member that moves forward and backward by the electric actuator against the rotating member that rotates together with the wheel, An accelerator opening sensor for detecting the accelerator opening; and a vehicle speed sensor for detecting the vehicle speed, and based on signals from the accelerator opening sensor and the vehicle speed sensor, the rotation member and the friction member when the brake is not operated. An electric brake device is proposed in which the position of the friction member is controlled by an electric actuator so that the clearance becomes wider as the accelerator opening becomes larger and becomes wider at higher vehicle speeds.

  According to the second aspect of the invention, in addition to the configuration of the first aspect, only the rear wheel of the front and rear wheels has a clearance between the rotating member and the friction member when the brake is not operated, as the vehicle speed is higher. An electric brake device is proposed in which the position of the friction member is controlled by an electric actuator so as to be wide.

  The electric motor M of the embodiment corresponds to the electric actuator of the present invention, the brake pads 14a and 14b of the embodiment correspond to the friction member of the present invention, and the brake disc 13 of the embodiment corresponds to the rotating member of the present invention. To do.

According to the configuration of the first aspect, when the brake is not operated, the clearance between the rotating member that rotates together with the wheel and the friction member that moves forward and backward by the electric actuator is controlled so as to increase as the vehicle speed increases. By making the contact less likely to occur at high vehicle speeds when large drag resistance is generated by the contact of the vehicle, the fuel saving effect can be enhanced , while the clearance is controlled to be narrow at low vehicle speeds. A decrease in responsiveness can be minimized. In addition, since the clearance is controlled to increase as the accelerator opening increases, the braking responsiveness does not become a problem when the accelerator opening is large and the driver is less willing to perform the braking operation. By setting it large and making it difficult for the friction member to come into contact with the rotating member, drag resistance between them can be reduced, contributing to improvement in fuel consumption. Conversely, the accelerator opening is small and the driver performs braking operation accordingly. When the intention is large, it is necessary to prioritize the braking response, so that the clearance can be set small and the increase in the drag resistance can be allowed while increasing the braking response.

  According to the configuration of the second aspect, only the rear wheel of the front and rear wheels is set so that the clearance between the rotating member and the friction member when the brake is not operated becomes wider as the vehicle speed increases. On the other hand, by delaying the braking start timing of the rear wheels, it is possible to suppress the locking of the rear wheels and to stabilize the vehicle behavior.

  Hereinafter, embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.

  1 to 6 show an embodiment of the present invention. FIG. 1 is a cross-sectional view of an electric brake having a function of an electric stop brake, FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 is a sectional view taken along the line 3-3 in FIG. 1, FIG. 4 is a diagram for explaining the operation when the electric stop brake is operated, FIG. 5 is a diagram for explaining the operation when the electric stop brake is forcibly released, and FIG. is there.

  As shown in FIGS. 1 to 3, the electric brake that can also be used as an electric stop brake includes a brake caliper 11 that is supported by a knuckle or the like so as to be movable in the left-right direction in FIG. 1. Brake pads 14a and 14b are provided on opposite surfaces of a pair of back plates 12a and 12b that are supported by guide means (not shown) so as to be able to approach and separate from each other. It is done. A brake piston 15 is supported on the main body 11a of the brake caliper 11 so as to be able to advance and retreat. The brake caliper 11 is pressed against the back surface of one back plate 12a by the brake piston 15 so that the brake caliper 11 is moved to the right in FIG. The arm portion 11c connected to the main body portion 11a of the brake caliper 11 via the bridging portion 11b presses the back surface of the other back plate 12b, so that both brake pads 14a and 14b A braking force is generated in contact with both side surfaces. A dustproof boot 16 is mounted between the brake piston 15 and the brake caliper 11.

  The electric motor M housed in the main body 11a of the brake caliper 11 includes a plurality of stator coils 17 fixed to the inner surface of the main body 11a, and a ball bearing 18 that is rotatable around the axis L inside the stator coils 17. And a plurality of permanent magnets 20 fixed to the outer peripheral surface of the motor output shaft 19 so as to face the inner peripheral surface of the stator coils 17. A cylindrical female screw member 21 is supported inside the motor output shaft 19 by a pair of ball bearings 22 and 23 so as to be relatively rotatable. Between the male screw member 24 extending integrally on the axis L from the back surface of the brake piston 15. Are arranged with a plurality of balls 25. These female screw member 21, male screw member 24 and balls 25 ... constitute a ball screw mechanism S.

  A planetary gear mechanism P is arranged inside the main body 11 a of the brake caliper 11 so as to connect the electric motor M and the ball screw mechanism S. The planetary gear mechanism P disposed on the axis L includes a sun gear 31 fixed to the motor output shaft 19, a planetary carrier 32 serving also as a ratchet wheel fixed to the female screw member 21 of the ball screw mechanism S, and an outer periphery of the planetary carrier 32. And a plurality of pinions 35 that are supported on the planetary carrier 32 via pinion shafts 34 and mesh with the sun gear 31 and the ring gear 33 at the same time. Between the planetary carrier 32 and the inner surface of the main body 11a, a thrust bearing 36 for supporting a braking reaction force that the brake piston 15 receives from the brake disk 13 is disposed.

  The planetary gear mechanism P includes three elements: a sun gear 31, a planetary carrier 32 (ratchet wheel), and a ring gear 33. The sun gear 31 constituting the input element is fixed to the motor output shaft 19 and the planetary constituting the output element. The carrier 32 is fixed to the female screw member 21 of the ball screw mechanism S via the connecting shaft 37, and the ring gear 33 constituting the fixing element is fixed to the main body portion 11 a of the brake caliper 11. At this time, the sun gear 31 is supported on the outer periphery of the connecting shaft 37 disposed on the axis L so as to be relatively rotatable.

  The electric brake includes a ratchet mechanism R for causing it to function as an electric stop brake. The ratchet mechanism R has a ratchet pawl 42a at one end thereof, which is pivotally supported by the planetary carrier 32 (ratchet wheel) and a central portion by a fulcrum pin 41 so that the ratchet mechanism R can engage with the ratchet teeth 32a of the planetary carrier 32. The ratchet pawl 42, the torsion coil spring 43 that urges the ratchet pole 42 in the direction in which the ratchet pawl 42a is detached from the ratchet teeth 32a, and the one end side of the ratchet pawl 42 are pressed so that the ratchet pawl 42a is moved to the ratchet teeth 32a. .. Are provided, and a bolt 45 capable of pressing the other end of the ratchet pole 42 is provided.

  Returning to FIG. 1, the electronic control unit U controls the operation of the electric motor M based on signals from the brake pedal depression force sensor Sa, the vehicle speed sensor Sb, and the accelerator opening degree sensor Sc.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  When the electric brake is used as a service brake, the rotation of the rotor output shaft 19 is input to the sun gear 31 of the planetary gear mechanism P and the ring gear 33 rotates when the electric motor M is driven to rotate forward according to the output of the brake pedal depression force sensor Sa. The rotation of the sun gear 31 is transmitted to the female screw member 21 of the ball screw mechanism S via the pinion 35..., The planetary carrier 32 and the connecting shaft 37. When the female screw member 21 rotates, the male screw member 21 engaged therewith via the balls 25... Moves forward together with the brake piston 15, and the brake piston 15 causes the brake pads 14 a and 14 b to contact the brake disc 13 to generate a braking force. To do. When the electric motor M is driven in reverse, the brake piston 15 moves backward, the brake pads 14a and 14b are separated from the brake disc 13, and the braking force is released.

  When the electric brake is used as an electric stop brake, when the driver turns on the parking switch, the electric motor M rotates forward and the brake piston 15 moves forward, so that the braking force is applied in the same manner as in the case of the service brake described above. appear. When a predetermined braking force is generated, the solenoid 44 is energized, and the ratchet pole 42 pressed by the solenoid 44 is counteracted around the fulcrum pin 41 against the elastic force of the torsion coil spring 43 as shown in FIG. By swinging clockwise, the ratchet pawl 42a of the ratchet pole 42 is engaged with the ratchet teeth 32a of the planetary carrier 32.

  When energization of the electric motor M is stopped in this state, the brake pads 14a and 14b are retracted by the reaction force received from the brake disc 13, and the planetary carrier 32 is about to rotate in the braking release direction. The pawl 42a meshes strongly with the ratchet teeth 32a of the planetary carrier 32, and the electric stopping brake is kept in the operating state even when the energization of the solenoid 44 is released.

  When the driver turns off the parking switch, the electric motor M is driven in the forward rotation direction for a moment, and the planetary carrier 32 rotates slightly in the braking direction. As a result, the ratchet pawl 42a of the ratchet pole 42 is disengaged from the ratchet teeth 32a of the planetary carrier 32, and the ratchet pole 42 rotates clockwise to the position of FIG. Thus, the restraint of the planetary carrier 32 is released. Then, the brake pads 14a and 14b are automatically retracted by the reaction force received from the brake disc 13, and the operation of the electric stop brake is released. At this time, the electric motor M may be reversed to assist the reaction force received by the brake pads 14a, 14b from the brake disc 13.

  Now, if the electric motor M fails during the operation of the electric stop brake, the ratchet mechanism R cannot be disengaged, the electric stop brake remains operated, and the vehicle cannot run. In such a case, as shown in FIG. 5, by manually rotating the bolt 45, the ratchet pole 42 is pressed and swung clockwise around the fulcrum pin 41, and the ratchet pawl 42a of the ratchet pole 42 is moved to the planetary position. It can be forcibly separated from the ratchet teeth 32a of the carrier 32. As a result, it is possible to avoid a situation in which the operation of the electric stop brake cannot be released when the electric motor M including the failure of the power source cannot be operated.

  Next, clearance control when the electric brake is not braked will be described with reference to FIG. The clearance here refers to clearances Lf and Lr (see FIG. 1) between the brake pads 14a and 14b and the brake disk 13.

When the electric brake is not activated in step S1 of the flowchart of FIG. 6, the accelerator opening Ap is read from the accelerator opening sensor Sb in step S2, and the vehicle speed Vv is read from the vehicle speed sensor Sc in step S3. If the vehicle speed Vv exceeds the threshold value Vth in step S4, the clearance Lf of the front wheel electric brake and the clearance Lr of the rear wheel electric brake are set in step S5, α is the accelerator opening coefficient, and β is the vehicle speed coefficient. Respectively,
Lf = α × Ap
Lr = α × Ap + β × Vv
Calculated by

If the vehicle speed Vv is equal to or lower than the threshold value Vth in step S4, the front wheel electric brake clearance Lf and the rear wheel electric brake clearance Lr are set in step S6, respectively.
Lf = α × Ap
Lr = α × Ap
Calculated by

  In step S7, the electronic control unit U controls the operation of the electric motor M so that the clearances Lf and Lr are generated.

  As a result, the clearances Lf and Lr increase as the accelerator opening Ap increases regardless of the vehicle speed. A large accelerator opening Ap means that the driver is less willing to perform a braking operation. At that time, the response of braking does not matter, so the clearances Lf and Lr are set large and the brake pads 14a and 14b are braked. By making it difficult to contact the disk 13, it is possible to reduce the drag resistance of the brake and contribute to the improvement of fuel consumption. Conversely, if the accelerator opening Ap is small or zero, it means that the driver is more willing to perform the braking operation. At that time, it is necessary to give priority to the responsiveness of braking, so the clearances Lf and Lr are set small. Thus, the braking response can be enhanced while allowing a slight increase in drag resistance.

  At high vehicle speeds, the clearance Lr is calculated by adding a term (β × Vv) that depends on the vehicle speed Vv to a term (α × Ap) that depends on the accelerator pedal opening Ap only for the rear wheel electric brake ( (See step S5). As a result, when the driver depresses the brake pedal, first, the front wheel electric brake with a small clearance Lf is activated, and the rear wheel electric brake with a larger clearance Lr depending on the vehicle speed Vv (β × Vv). Operates late. Thus, by delaying the braking start timing of the rear wheels with respect to the front wheels at a high vehicle speed, it is possible to suppress the locking of the rear wheels during emergency braking and stabilize the vehicle behavior.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, although the electric brake of the embodiment also uses the service brake as a parking brake, the present invention can also be applied to a dedicated service brake.

Cross section of electric brake with electric stop brake function 2-2 sectional view of FIG. 3-3 sectional view of FIG. Action explanatory diagram at the time of operation of electric stop brake Action explanatory diagram at the time of forced release of electric stop brake Flow chart of clearance adjustment routine

Lf Clearance Lr Clearance M Electric motor (electric actuator) 13 Brake disc (rotating member)
14a Brake pad (friction member)
14b Brake pad (friction member)

Claims (2)

In the electric brake device for a vehicle that generates a braking force by pressing a friction member (14a, 14b) that moves forward and backward by an electric actuator (M) against a rotating member (13) that rotates together with a wheel,
An accelerator opening sensor (Sb) for detecting the accelerator opening (Ap);
A vehicle speed sensor (Sc) for detecting the vehicle speed (Vv),
On the basis of the signal from an accelerator opening sensor (Sb) and said vehicle speed sensor (Sc), the rotating member (13) and the friction member (14a, 14b) during braking inoperative and clearance (Lf, Lr) is, The electric brake for vehicles, wherein the position of the friction member (14a, 14b) is controlled by the electric actuator (M) so that the accelerator opening (Ap) becomes wider as the accelerator opening (Ap) becomes larger and becomes wider as the vehicle speed increases. apparatus. For only the rear wheels of the front and rear wheels, the electric actuator (M) is such that the clearance (Lf, Lr) between the rotating member (13) and the friction members (14a, 14b) when the brake is not operated becomes wider as the vehicle speed increases. 2), the position of the friction member (14a, 14b) is controlled by the vehicle electric brake device according to claim 1.

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