JP7622485B2 - Vehicle Brake Device - Google Patents

Description

The present invention relates to a vehicle braking system.

A known vehicle braking device uses drum brakes, as described in JP 2010-274689 A, for example. In this vehicle braking device, a load sensor is provided on the anchor to calculate the braking force.

JP 2010-274689 A

In the above vehicle braking system, the load sensor is mounted on an anchor located at the bottom inside the wheel. In this arrangement, the wiring for the load sensor must be routed vertically across the wheel from bottom to top, which can easily lead to cumbersome routing of the wiring passing between moving parts such as the hub, brake shoe, and arm. If the load sensor is only located at the anchor, it becomes difficult to eliminate the complication of the wiring. In other words, the conventional configuration leaves room for improvement in terms of the freedom of placement of the load sensor.

The object of the present invention is to provide a vehicle braking system that allows for greater freedom in the placement of load sensors.

The vehicle braking device of the present invention comprises a brake rotor that rotates together with a wheel, a friction member that is pressed against the brake rotor during braking, a torque receiving portion that applies a braking force to the wheel by preventing rotation of the friction member, a drive device that drives the friction member to press it against the brake rotor, a load sensor that is provided on at least one of the drive device and the torque receiving portion and detects a force in a different direction relative to a direction in which the drive device drives the friction member, and a calculation portion that calculates the braking force based on a detection value of the load sensor , and the load sensor comprises a strain sensor fixed to at least one of the torque receiving portion and the drive device so as to surround a part of the friction member, a strain gauge fixed to at least one of an upper surface and a lower surface of the strain sensor, and an auxiliary member located inside the strain sensor and fixed to the friction member so as to transmit the force in the different direction received by the friction member to the strain sensor .

For example, if a vehicle braking device has two friction members (brake shoes), when a braking torque is generated while the vehicle is moving forward, a downward force is applied to the leading shoe due to the reaction of the torque, and an upward force is applied to the trailing shoe. In other words, forces are applied to the brake shoes in different directions relative to the direction in which the drive device drives (moves) the friction member. The magnitude of these vertical forces corresponds to the magnitude of the braking torque (braking force). Therefore, the braking torque can be calculated by detecting forces in different directions relative to the direction in which the drive device drives the friction member during braking.

In conventional configurations, the load sensor is provided at a location (torque-receiving portion such as an anchor) where a force in the vehicle's fore-and-aft direction is directly applied in order to detect the force in the direction in which the drive unit presses the friction member (the vehicle's fore-and-aft direction). However, according to the present invention, the load sensor only needs to be positioned so that it receives a force in a direction different from the direction in which the drive unit drives the friction member. For this reason, the object on which the load sensor is to be installed is not limited to the portion that directly receives the load of the friction member, and may be, for example, the drive unit. In this way, according to the present invention, the load sensor detects a force in a direction different from the direction in which the drive unit drives the friction member, thereby improving the freedom of placement of the load sensor.

1 is a configuration diagram of a vehicle braking device according to a first embodiment (a cross-sectional view seen from the left side of a vehicle). 1 is a configuration diagram of a vehicle braking device according to a first embodiment (a cross-sectional view seen from above a vehicle); FIG. 11 is a configuration diagram of a load sensor according to a second embodiment (a cross-sectional view seen from the left side of the vehicle). FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 13 is a configuration diagram of a load sensor according to a third embodiment (a cross-sectional view seen from the left side of the vehicle). FIG. 13 is a configuration diagram of a load sensor according to a fourth embodiment (a cross-sectional view seen from the left side of the vehicle). FIG. 13 is a configuration diagram (sectional view seen from the left side of the vehicle) of a modified embodiment of the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Note that in the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings. Also, each drawing used in the description is a conceptual diagram. In the following description, the front of the vehicle will be referred to as the front, and the rear of the vehicle will be referred to as the rear. Also, in the description, the wheel will be the wheel on the left side of the vehicle as an example. In Figure 2, the back plate 4 and other elements are omitted.

First Embodiment
As shown in Figures 1 and 2, the vehicle braking device 1 of the first embodiment is a so-called leading-trailing type drum brake, and includes a rotating drum (corresponding to the "brake rotor") 2, a first brake shoe (corresponding to the "friction member") 31, a second brake shoe (corresponding to the "friction member") 32, a back plate (corresponding to the "torque receiving portion") 4, an anchor (corresponding to the "torque receiving portion") 41, a drive device 5, a first load sensor 61, a second load sensor 62, and a brake ECU 7.

The rotating drum 2 is a member that rotates together with the wheel. The first brake shoe 31 and the second brake shoe 32 are friction members that are pressed against the rotating drum 2 during braking. The first brake shoe 31 and the second brake shoe 32 are each a convex arc-shaped member with a lining 30 on the outer periphery. The first brake shoe 31 is disposed relatively forward and is the leading shoe when the vehicle moves forward. The second brake shoe 32 is disposed relatively rearward and is the trailing shoe when the vehicle moves forward. The first brake shoe 31 and the second brake shoe 32 are disposed in an arc shape.

The back plate 4 is fixed to a vehicle body member (not shown) that rotatably supports the wheels. An anchor 41 is fixed to the bottom of the back plate 4, and a drive unit 5 is fixed to the top of the back plate 4. The bottom end of the first brake shoe 31 is supported on the front end of the anchor 41 so that it can rotate and move up and down. The bottom end of the second brake shoe 32 is supported on the rear end of the anchor 41 so that it can rotate and move up and down.

The support of the anchor 41 allows the upper end of the first brake shoe 31 and the upper end of the second brake shoe 32 to open (move apart) in the front-rear direction. The anchor 41 and the back plate 4 function as a torque receiving part that applies a braking force to the wheel by preventing the rotation of the first brake shoe 31 and the second brake shoe 32. The first brake shoe 31 and the second brake shoe 32 are connected by a return spring 90, and are configured to return to their initial positions when no force is applied from the drive unit 5.

The drive device 5 is a device (actuator) that drives the first brake shoe 31 and the second brake shoe 32 to press them against the rotating drum 2. The drive device 5 in the first embodiment constitutes an electric mechanical brake (EMB) that drives the first piston 52 and the second piston 53 with an electric motor 55. The drive device 5 is disposed between the upper end of the first brake shoe 31 and the upper end of the second brake shoe 32.

The drive unit 5 includes a fixed portion 51, a first piston 52, a second piston 53, a linear motion conversion portion 54, and an electric motor 55. The fixed portion 51 is a portion of the drive unit 5 that is fixed to the back plate 4. The fixed portion 51 can also be considered a housing for the drive unit 5. In more detail, the fixed portion 51 includes a first cylinder portion 511, a second cylinder portion 512, and a housing portion 513.

The first cylinder portion 511 constitutes the vehicle front portion of the fixed portion 51 and is arranged to face the first brake shoe 31. The first cylinder portion 511 is formed in a cylindrical shape that opens to the front of the vehicle. The front end portion of the screw shaft 541 of the linear motion conversion portion 54 is arranged inside the first cylinder portion 511.

The second cylinder portion 512 constitutes the vehicle rear portion of the fixed portion 51 and is arranged to face the second brake shoe 32. The second cylinder portion 512 is formed in a cylindrical shape that opens to the rear of the vehicle. The second cylinder portion 512 is arranged coaxially with the first cylinder portion 511. In other words, the central axis of the first cylinder portion 511 and the central axis of the second cylinder portion 512 are located on the same straight line. The rear end of the screw shaft 541 of the linear motion conversion portion 54 is arranged inside the second cylinder portion 512.

The accommodation section 513 is a portion that accommodates the linear motion conversion section 54, and is located between the first cylinder section 511 and the second cylinder section 512. The accommodation section 513 extends in the left-right direction of the vehicle so as to connect the first cylinder section 511 and the second cylinder section 512 to the electric motor 55 located on the vehicle body side (partially not shown). The accommodation section 513 is inserted into a through hole in the back plate 4 and fixed to the back plate 4.

The first piston 52 constitutes a movable part that drives the first brake shoe 31 to press it against the rotating drum 2. The first piston 52 is disposed opposite the upper end of the first brake shoe 31. The first piston 52 is disposed so as to be movable back and forth within the first cylinder portion 511. The first piston 52 includes a nut portion 521 and an abutment portion 522 provided at the front end of the nut portion 521.

The nut portion 521 is arranged so as to be movable in the front-rear direction but unable to rotate relative to the first cylinder portion 511. In other words, the first piston 52 and the first cylinder portion 511 are formed with a rotation stop mechanism (not shown) (e.g., engagement between a rail groove and a rail) so that the first piston 52 does not rotate around its axis relative to the first cylinder portion 511.

The nut portion 521 is screwed onto the screw shaft 541 of the linear motion conversion portion 54, and moves back and forth in response to the rotation of the screw shaft 541. In other words, when the screw shaft 541 rotates forward, the first piston 52 moves forward (towards the first brake shoe 31), and when the screw shaft 541 rotates reversely, the first piston 52 moves backward.

The abutment portion 522 is provided at the front end of the nut portion 521 and abuts against the first brake shoe 31. The abutment portion 522 is formed in a shape in which a slit 522a extending rearward is formed on the front end surface of a cylindrical member, that is, the abutment portion 522 is formed in an overall concave shape. The slit 522a opens forward and upward and downward. In other words, the abutment portion 522 is composed of left and right side walls 522b and a rear bottom wall 522c. The abutment portion 522 can be said to protrude forward in a U-shape from the nut portion 521. The upper rear end of the first brake shoe 31 is disposed within the slit 522a of the abutment portion 522. The bottom wall 522c of the abutment portion 522 abuts against the upper rear end of the first brake shoe 31.

The second piston 53 is a piston member disposed within the second cylinder portion 512 so as to be movable in the front-rear direction. The second piston 53 is formed in the same shape (front-reversed) as the abutment portion 522 of the first piston 52. In other words, the second piston 53 is formed in a shape in which a slit 53a extending forward is formed in the rear end surface of a cylindrical member, that is, the second piston 53 is formed in an overall concave shape. The slit 53a is open to the rear and above and below. In other words, the second piston 53 is composed of left and right side walls 53b and a front bottom wall 53c.

The upper front end of the second brake shoe 32 is disposed in the slit 53a of the second piston 53. The bottom wall 53c of the second piston 53 and the upper front end of the second brake shoe 32 are in contact with each other. The second piston 53 is disposed so as to receive a force from the screw shaft 541. Therefore, when the first piston 52 advances and presses the first brake shoe 31, the reaction force of the first brake shoe 31 pressing the first piston 52 backward is transmitted to the second piston 53 via the screw shaft 541. In other words, the second piston 53 presses the second brake shoe 32 backward with the same force as the force of the first piston 52 pressing the first brake shoe 31. According to the law of action and reaction, the second piston 53 also moves backward as the first piston 52 advances.

The linear motion conversion unit 54 is a mechanism that converts the rotational motion of the output shaft 551 of the electric motor 55 into the linear motion of the first piston 52. The linear motion conversion unit 54 is configured to transmit power from the output shaft 551 to the screw shaft 541 via a reducer. The first piston 52 can be said to constitute a part of the linear motion conversion unit 54.

The electric motor 55 is the driving source of the drive unit 5 and is controlled by the brake ECU 7. The driving force of the electric motor 55 is transmitted to the first piston 52 via the output shaft 551 and the linear motion converter 54.

The first load sensor 61 and the second load sensor 62 are provided on at least one of the drive device 5 and the torque receiving portion (here, the back plate 4 and the anchor 41), and are configured to detect the vertical force applied to the first brake shoe 31 and the second brake shoe 32 due to the rotation of the rotating drum 2 during braking. Here, the vertical force is an example of a force in a different direction from the front-rear direction in which the drive device drives the friction member. The first load sensor 61 is configured to detect a downward force applied to the first brake shoe 31. The second load sensor 62 is configured to detect an upward force applied to the second brake shoe 32. The first load sensor 61 and the second load sensor 62 are provided on the drive device 5.

More specifically, the first load sensor 61 is fixed to the first piston 52 and the first brake shoe 31. The first load sensor 61 is of the strain gauge type and includes a strain body 611 to which a strain gauge (not shown) is attached, and a transmitter 612 that amplifies the signal of the strain gauge and transmits it to the brake ECU 7.

The strain body 611 is a cylindrical metal member that is expected to elastically deform under load. The strain body 611 is arranged penetrating the contact portion 522 and the upper rear end of the first brake shoe 31 in the left-right direction. The strain body 611 is inserted into through holes 91 that penetrate in the left-right direction formed in each side wall 522b of the contact portion 522, and through holes 92 that penetrate in the left-right direction formed in the upper rear end of the first brake shoe 31. The transmitter 612 is fixed to the vehicle body side end of the strain body 611.

When a braking torque is generated while the vehicle is moving forward, a downward force is applied to the first brake shoe 31 as a reaction to the torque, as shown by the arrow in Figure 1. When the first brake shoe 31 receives the downward force and attempts to move downward, the strain body 611 fixed to the first piston 52 prevents the downward movement. In other words, the downward force applied to the first brake shoe 31 is applied to the strain body 611, and the central portion of the strain body 611 elastically deforms downward. The downward force (load) applied to the first brake shoe 31 is detected from this deformation.

The second load sensor 62 is fixed to the second piston 53 and the second brake shoe 32. Like the first load sensor 61, the second load sensor 62 is of the strain gauge type and includes a strain body 621 to which a strain gauge (not shown) is attached, and a transmitter 622 that amplifies the signal of the strain gauge and transmits it to the brake ECU 7.

The flexure body 621 is a cylindrical member and is disposed so as to penetrate the upper front end of the second piston 53 and the second brake shoe 32 in the left-right direction. The flexure body 621 is inserted through a through hole 93 formed in each side wall 53b of the second piston 53 and penetrating in the left-right direction, and a through hole 94 formed in the upper front end of the second brake shoe 32 and penetrating in the left-right direction. The transmitter 622 is fixed to the vehicle body side end of the flexure body 621.

When a braking torque is generated while the vehicle is moving forward, an upward force is applied to the second brake shoe 32 due to a reaction to the torque, as shown by the arrow in Figure 1. When the second brake shoe 32 receives the upward force and attempts to move upward, the strain body 621 fixed to the second piston 53 prevents the upward movement. In other words, the upward force applied to the second brake shoe 32 is applied to the strain body 621, and the central portion of the strain body 621 deforms upward. The upward force (load) applied to the second brake shoe 32 is detected from this deformation.

The brake ECU 7 is an electronic control unit equipped with a processor, memory, etc. The brake ECU 7 controls the drive unit 5 in response to a braking request. When the brake ECU 7 rotates the output shaft 551 of the electric motor 55 in the forward direction in response to a braking request, the first piston 52 moves forward and presses the first brake shoe 31 against the rotating drum 2, and the second piston 53 moves backward and presses the second brake shoe 32 against the rotating drum 2. This generates a frictional force (resistance force) against the rotation of the wheel and the rotating drum 2, providing a braking force.

The brake ECU 7 is equipped with a calculation unit 71 that calculates the braking force (braking torque) based on the detection values of the load sensors 61, 62. When the vehicle is moving forward, the greater the force with which the first piston 52 presses the first brake shoe 31 and the force with which the second piston 53 presses the second brake shoe 32, the greater the frictional force that is generated, and the greater the downward force applied to the first brake shoe 31 and the upward force applied to the second brake shoe 32. In other words, the greater the braking force applied while the vehicle is moving, the greater the vertical force applied to each brake shoe 31, 32. The braking force corresponds to the vertical force applied to each brake shoe 31, 32. Therefore, the calculation unit 71 can calculate the braking force based on the vertical force applied to each brake shoe 31, 32.

When a braking force is generated while the vehicle is moving backwards, an upward force is applied to the first brake shoe 31, and a downward force is applied to the second brake shoe 32. If the load sensors 61, 62 are configured to be able to detect loads in both the upward and downward directions, or if an initial load is set, it will be possible to detect the upward and downward forces applied by braking when the vehicle is moving backwards. In this case, the brake ECU 7 can determine that the vehicle is moving backwards from information from another ECU, so the calculation unit 71 can also calculate the braking force when the vehicle is moving backwards based on the detection values of the load sensors 61, 62.

(Effects of the First Embodiment)
According to the first embodiment, the load sensors 61, 62 only need to be arranged so as to receive the vertical force applied to the corresponding brake shoes 31, 32. Therefore, the object on which the load sensors 61, 62 are to be installed is not limited to the anchors 41 that directly receive the loads of the brake shoes 31, 32, but can be the drive device 5 as in the above embodiment. Thus, according to the first embodiment, the detection direction of the load sensors 61, 62 is set to the vertical direction, thereby improving the degree of freedom in the arrangement of the load sensors 61, 62.

In addition, according to the first embodiment, since the load sensors 61 and 62 are provided in the drive unit 5, the wiring for the load sensors 61 and 62 is arranged at the top inside the wheel. This prevents the wiring from becoming complicated.

Second Embodiment
The configuration of the second embodiment is different from that of the first embodiment mainly in terms of the configuration of the load sensor. The different parts will be described below with reference to Figures 3 and 4. In the description of the second embodiment, the description and drawings of the first embodiment can be referred to as appropriate.

The load sensor 63 in the second embodiment is a sensor that detects the vertical force applied to the first brake shoe 31. The load sensor 63 includes a strain body 631, strain gauges 632 and 633, and an auxiliary member 634.

The flexure body 631 is an annular metal member that is expected to be elastically deformed by a load. The flexure body 631 is fixed to the back plate 4, for example, via a plurality of fastening members (not shown). The movement of the flexure body 631 is restricted by the back plate 4. The flexure body 631 is arranged so as to surround a part of the first brake shoe 31 via the auxiliary member 634. In summary, the flexure body 631 is an annular member fixed to the back plate 4 so as to surround a part of the first brake shoe 31. The flexure body 631 may be fixed to the drive device 5. In this example, the flexure body 631 is formed in an annular shape, but it does not have to be annular as long as it is formed so as to surround a part of the first brake shoe 31. For example, the flexure body 631 may be formed in a square shape. The flexure body 631 is not limited to a circular annular shape, and may be an annular polygonal shape.

Similar to the first embodiment, the strain gauges 632 and 633 are sensors that measure the strain (deformation) of an object, and their electrical resistance changes depending on the applied force. The strain gauge 632 is plate-shaped and is fixed to the upper surface of the strain body 631. The strain gauge 633 is plate-shaped and is fixed to the lower surface of the strain body 631.

The auxiliary member 634 is disposed between the first brake shoe 31 and the flexure body 631, and is a member for transmitting the vertical force received by the first brake shoe 31 to the flexure body 631. The auxiliary member 634 is fixed to the upper rear end of the first brake shoe 31. In this example, the auxiliary member 634 is formed in an elliptical cylindrical shape having an elliptical cross section with a major axis extending in the vertical direction and a minor axis extending in the left-right direction. The length of this major axis is slightly smaller than the inner diameter of the flexure body 631. In summary, the auxiliary member 634 is located inside the flexure body 631, and is a member fixed to the first brake shoe 31 so as to transmit the vertical force received by the first brake shoe 31 to the flexure body 631. Because the auxiliary member 634 is elliptical cylindrical, stress concentration of the auxiliary member 634 on the flexure body 631 is suppressed.

The load sensor 63 may be provided with transmitters 635 and 636. The transmitter 635 amplifies the signal of the strain gauge 632 and transmits it to the brake ECU 7. Similarly, the transmitter 636 amplifies the signal of the strain gauge 633 and transmits it to the brake ECU 7. The strain gauges 632 and 633 and the corresponding transmitters 635 and 636 can be connected, for example, by wiring. The positions of the transmitters 635 and 636 can be set arbitrarily.

According to the configuration of the second embodiment, when a downward force is applied to the first brake shoe 31 during braking while the vehicle is moving forward, the force is transmitted to the strain body 631 via the auxiliary member 634. Since the movement of the strain body 631 is restricted, the lower inner circumferential surface of the strain body 631 is pressed against the auxiliary member 634, causing the strain body 631 to deform. This deformation is detected at least by the strain gauge 633.

When braking while the vehicle is moving backwards, an upward force is applied to the first brake shoe 31, and the upper inner circumferential surface of the flexure body 631 is pressed against the auxiliary member 634, causing the flexure body 631 to deform. This deformation is detected by at least the strain gauge 632. As a result, as in the first embodiment, the amount of deformation of the flexure body 631 is transmitted to the brake ECU 7, and the braking force is calculated by the calculation unit 71 based on that.

In this way, even with the configuration of the second embodiment, the load sensor 63 can be placed at the top inside the wheel by taking advantage of the freedom of placement, and the same effect as the first embodiment is achieved. Note that a configuration similar to the load sensor 63 may be provided for the second brake shoe 32. Also, only one of the strain gauges 632, 633 may be provided.

Third Embodiment
The configuration of the third embodiment is different from that of the first embodiment mainly in terms of the configuration of the load sensor. The different parts will be described below with reference to Fig. 5. In the description of the third embodiment, the descriptions and drawings of the first and second embodiments can be referred to as appropriate.

The load sensor 64 of the third embodiment is a sensor provided on the first piston 52 of the drive unit 5, and detects the vertical force applied to the first brake shoe 31. The load sensor 64 includes a strain body 641 and a strain gauge 642. The strain body 641 is disposed in the slit 522a of the abutment portion 522. The strain body 641 is disposed below the first brake shoe 31.

The flexure body 641 is a plate-like member extending in the front-rear direction, with one end (rear end) fixed to the bottom wall 522c of the abutment portion 522 and the top surface of the other end (front end) configured to abut against or face the first brake shoe 31 with a gap. The front end of the flexure body 641 protrudes upward. The flexure body 641 is formed so that its vertical width is smaller than its horizontal width so that it can easily elastically deform in the vertical direction.

The strain gauge 642 is fixed to the underside of the strain body 641. The signal of the strain gauge 642 is transmitted to the brake ECU 7, for example, via a transmitter (not shown) that amplifies the signal. When a downward force is applied to the first brake shoe 31 during braking while the vehicle is moving forward, the first brake shoe 31 presses the strain body 641 downward, causing one end (front end) of the strain body 641 to deform downward. This deformation is transmitted to the brake ECU 7, and the braking force is calculated by the calculation unit 71.

In addition, an initial load can be set in the load sensor 64 by pressing the strain body 641 against the first brake shoe 31 in advance and setting the state in which it is deformed as the initial state. As a result, when the first brake shoe 31 receives an upward force and moves upward, the amount of deformation of the strain body 641 becomes smaller than in the initial state, and this change can be detected. With this configuration, even when braking while the vehicle is moving backwards, the change in the load of the strain body 641 can be detected, and the calculation unit 71 can calculate the braking force. The configuration of applying an initial load to the load sensor can also be applied to, for example, the first embodiment.

Even with the configuration of the third embodiment, the load sensor 64 is provided in the drive device 5, and the same effect as in the first embodiment is achieved. The load sensor 64 may be provided in the second piston 53. In this case, the strain body 641 is, for example, disposed above the second brake shoe 32 in the slit 53a.

Fourth Embodiment
The configuration of the fourth embodiment differs from that of the first embodiment mainly in the configuration of the load sensor and the piston. The different parts will be described below with reference to Fig. 6. In the description of the fourth embodiment, the descriptions and drawings of the first to third embodiments can be referred to as appropriate.

The slit 522a of the first piston 52 in the fourth embodiment is open in the forward and left-right directions, unlike the first embodiment. In other words, the abutment portion 522 is composed of upper and lower side walls 522d and a bottom wall 522c. The upper rear end of the first brake shoe 31 is positioned within the slit 522a.

The load sensor 65 of the fourth embodiment is a sensor provided on the first piston 52 of the drive unit 5, and detects the vertical force applied to the first brake shoe 31. The load sensor 65 includes a sensor unit 651 equipped with a piezoelectric element (not shown), and a preload unit 652 that applies an initial load to the sensor unit 651.

The sensor unit 651 is disposed below the first brake shoe 31 and detects the downward force applied to its upper surface. The sensor unit 651 is fixed on the lower wall 522d of the abutment portion 522. The upper surface of the sensor unit 651 abuts against the first brake shoe 31.

The preload portion 652 is provided on the upper wall 522d of the abutment portion 522. The sensor portion 651 and the preload portion 652 are arranged to sandwich the first brake shoe 31 from above and below. The preload portion 652 includes a pressing portion 652a, a spring 652b, and a base portion 652c. The pressing portion 652a is a member that abuts against the first brake shoe 31 and presses it downward. The pressing portion 652a is formed in a spherical shape. The pressing portion 652a is arranged opposite the sensor portion 651 across the first brake shoe 31.

The spring 652b is a biasing member whose lower end is fixed to the pressing portion 652a and whose upper end is fixed to the base portion 652c, and which biases the pressing portion 652a downward. The base portion 652c functions as a base for the spring 652b, and is a member fixed to the abutting portion 522. The base portion 652c is fixed, for example, by press-fitting into a through-hole 522e that penetrates vertically and is formed in the upper wall 522d. The base portion 652c may be formed from a part of the upper wall 522d.

In the initial state, i.e., when the electric motor 55 is not driven, the preload section 652 presses the first brake shoe 31 toward the sensor section 651 with a predetermined force. As a result, in the initial state, the sensor section 651 detects a downward force. In other words, the initial value of the load sensor 65 is a value greater than 0.

When a downward force is applied to the first brake shoe 31 during braking while the vehicle is moving forward, the sensor portion 651 is pressed downward, and the detection value of the load sensor 65 increases from its initial value (initial value > 0). When an upward force is applied to the first brake shoe 31 during braking while the vehicle is moving backward, the first brake shoe 31 pushes the pressing portion 652a upward, and the downward pressing force on the sensor portion 651 becomes smaller than in the initial state. As a result, the detection value of the load sensor 65 becomes smaller than its initial value. In other words, a load sensor 65 with this configuration can detect braking forces not only when the vehicle is moving forward, but also when the vehicle is moving backward.

Even in the configuration of the fourth embodiment, the load sensor 65 can be provided in the drive unit 5, and the same effect as in the first embodiment can be achieved. The load sensor 65 may also be provided in the second piston 53. In this case, the sensor unit 651 and the preload unit 652 are arranged to sandwich the second brake shoe 32 from above and below. For example, the sensor unit 651 is fixed to the lower surface of the upper wall of the second piston 53, and the preload unit 652 is provided on the lower wall of the second piston 53.

＜Other＞
The present invention is not limited to the above embodiment. For example, the present invention only requires that the braking force be calculated based on a force in a different direction relative to the direction in which the driving device drives the friction member, and the braking force may be calculated based on a force in a direction inclined relative to the vertical direction, not limited to the vertical force applied to the brake shoe (friction member). For example, the auxiliary member, the strain body, and the strain gauge may be attached to the brake shoe so as to be intentionally inclined. If the auxiliary member is inclined relative to the brake shoe due to product variations, it is considered that the auxiliary member and the strain body come into contact when the brake shoe moves forward, thereby hindering the movement of the brake shoe to move forward. In order to suppress this phenomenon, as shown in FIG. 7, the auxiliary member 634, the strain body 631, and the strain gauges 632 and 633 are intentionally inclined to increase the gap on the side where the auxiliary member 634 and the strain body 631 come into contact when the first brake shoe 31 moves forward. As a result, even if there is variation in the assembly of the auxiliary member 634 relative to the first brake shoe 31, it is possible to suppress a decrease in braking force caused by contact between the auxiliary member 634 and the strain body 631. It can also be said that the load sensor 6 detects a force including a vertical force component. Furthermore, it is applicable regardless of the type of drum brake, for example, to a duo-servo type drum brake. Furthermore, the drive unit 5 may be a hydraulic drive unit that drives a piston by hydraulic pressure. Furthermore, if the load of the leading shoe can be detected, the load of the trailing shoe can be estimated. Therefore, a load sensor may be provided only for one of the first brake shoe 31 and the second brake shoe 32.

A load sensor that detects the vertical force of the brake shoe may be provided on the anchor 41. For example, a load sensor may be provided at the connection between the anchor 41 and the first brake shoe 31 to detect the downward movement of the first brake shoe 31 relative to the anchor 41. For example, the load sensor 64 may be provided on the anchor 41.

1...vehicle braking device, 2...rotating drum (brake rotor), 31...first brake shoe (friction member), 32...second brake shoe (friction member), 4...back plate (torque receiving portion), 41...anchor (torque receiving portion), 5...driving device, 61-65...load sensors, 71...calculation unit.

Claims (2)

A brake rotor that rotates together with the wheel;
a friction member that is pressed against the brake rotor during braking;
a torque receiving portion that applies a braking force to the wheel by preventing rotation of the friction member;
a drive device that drives the friction member to press it against the brake rotor;
a load sensor provided in at least one of the driving device and the torque receiving portion, the load sensor detecting a force in a direction different from a direction in which the driving device drives the friction member;
a calculation unit that calculates the braking force based on a detection value of the load sensor;
Equipped with
The load sensor includes:
a strain generating body fixed to at least one of the torque receiving portion and the drive device so as to surround a portion of the friction member;
a strain gauge fixed to at least one of an upper surface and a lower surface of the strain generating body;
an auxiliary member located inside the strain body and fixed to the friction member so as to transmit the forces received by the friction member in different directions to the strain body;
A vehicle braking device comprising : The vehicle braking device according to claim 1, wherein the load sensor is provided in the drive device.

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