Electromechanical brake with force sensor

Abstract

The invention relates to an electromechanical brake with a force sensor. An assembly for an electromechanical brake of a vehicle having a caliper assembly driven by an electric motor includes a cup gear or drive disc for receiving torque from the electric motor and transmitting the torque to a main shaft. A piston is coupled to the spindle or the ball ramp and axially moves relative to the spindle in response to rotation of the spindle to brake the vehicle during a braking operation. A force sensor is aligned with the spindle and the cup gear for sensing a reaction force applied to the piston during a braking operation. A thrust bearing is provided for transmitting a reaction force from the cup gear to the force sensor.

Description

Technical Field

[0001] The present invention relates to a brake system, and in particular to an electromechanical brake having a force sensor integrated therein. Background Art

[0002] Current vehicles are equipped with electric motor service brakes to help control vehicle braking based on predetermined conditions. The service brakes rely on one or more movable pistons that selectively apply force to brake pads to slow or stop the rotating wheel rotors on the vehicle. The direction of rotation of the electric motor can be reversed to release or reduce braking in emergency situations or in drive-away conditions from a standstill on a hill. Summary of the invention

[0003] In one example, an assembly for an electromechanical brake for a vehicle having a caliper assembly driven by an electric motor includes a cup gear for receiving torque from the electric motor and transmitting the torque to a spindle. A piston is coupled to the spindle and moves axially relative to the spindle in response to rotation of the spindle to brake the vehicle during a braking operation. A force sensor is aligned with the spindle and the cup gear for sensing a reaction force applied to the piston during a braking operation. A thrust bearing is provided for transmitting the reaction force from the cup gear to the force sensor.

[0004] In another example, an assembly of an electromechanical brake for a vehicle having a caliper assembly driven by an electric motor includes a spindle and a piston coupled to the spindle and axially moving relative to the spindle in response to rotation of the spindle to brake the vehicle during a braking operation. A cup gear is provided for receiving torque from the motor and transmitting the torque to the spindle. A housing receives the cup gear and receives at least a portion of the spindle and the piston. A button force sensor is aligned with the spindle and the cup gear for sensing a reaction force applied to the piston during a braking operation. A thrust bearing is provided for transmitting the reaction force from the cup gear to the force sensor. A load flange received by the cup gear is axially positioned between the spindle and the force sensor for transmitting the reaction force from the cup gear to the force sensor. A controller is connected to the button force sensor and is configured to adjust the torque applied to the spindle in response to receiving a signal from the force sensor indicating the reaction force.

[0005] In another example, a method of controlling a caliper assembly of a vehicle includes applying current to a motor for actuating the caliper assembly to initiate a braking operation. Monitoring rotation of the motor during brake actuation. Sensing a reaction force through the caliper assembly during the braking operation. Adjusting the current applied to the motor until the sensed reaction force reaches a predetermined amount.

[0006] Other objects and advantages and a more complete understanding of the present invention will be obtained from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic diagram of a vehicle having a braking system.

[0008] Figure 2 is used for Figure 1 A perspective view of a portion of an exemplary caliper assembly of a brake system.

[0009] Figure 3A is along Figure 2 A cross-sectional view of the caliper assembly taken along line 3A-3A in FIG.

[0010] Figure 3B yes Figure 3A A magnified view of the caliper assembly's force sensor.

[0011] Figure 4 is a schematic diagram of an electric motor coupled to a portion of a caliper assembly.

[0012] Figure 5 is the front view of the force sensor.

[0013] Figure 6 is a schematic diagram of the force sensor during braking operation. DETAILED DESCRIPTION

[0014] The present invention relates to a brake system and in particular to an electromechanical brake or EMB having a force sensor integrated therein. Figure 1 An exemplary electric brake / brake system 10 according to the present invention is shown for a motor vehicle 20. The vehicle 20 may be an electric, hybrid, or internal combustion engine powered vehicle.

[0015] The vehicle 20 extends from a first end or front end 24 to a second end or rear end 26. A pair of steerable wheels 30 are disposed at the front end 24. Each wheel 30 includes a wheel rotor 36 that is driven and steered by a steering linkage (not shown). A pair of steerable or non-steerable wheels 32 are disposed at the rear end 26. Each wheel 32 includes a wheel rotor 38 that is driven by a steering linkage (not shown). Friction brake pads 37 are associated with each wheel rotor 36, 38 and are positioned on opposite sides thereof.

[0016] In the case of an electric vehicle, the battery 40 provides power to the vehicle 20 and cooperates with the front driveline and / or the rear driveline 42 to provide torque to the wheels 30. In other words, the battery 40 forms part of the vehicle's propulsion system.

[0017] A caliper or caliper assembly 60 is disposed on at least one of the wheel rotors 36, 38 and controls the service and parking brakes associated with that wheel rotor. As shown, each of the wheel rotors 36, 38 on the front end 24 and the rear end 26 includes a caliper assembly 60. The caliper assembly 60 is an electromechanical brake and therefore does not rely on or require hydraulic fluid for operation. It should be understood that for the sake of simplicity, certain conventional features of the caliper assembly 60, such as the drive motor, are not described herein. Figure 2 Shown in.

[0018] See also Figure 2 and Figure 3A The caliper assembly 60 includes a housing 70 extending from a first end 74 to a second end 76 along a centerline 72. A first passage 78 extends through the housing 70 perpendicular to the centerline 72 and receives the brake pad 37 (shown in phantom) in a known manner. A second passage 80 extends through the first end 74 of the housing 70 generally along the centerline 72 to the first passage 78.

[0019] The caliper assembly 60 also includes a spindle 90 and a ball nut 100 operatively coupled thereto for selectively applying a braking force F to the rotor 36 or 38 via the brake pad 37 in a known and controllable manner. The caliper assembly 60 may be configured as a ball nut assembly (recirculating or non-recirculating), a roller screw, a ball ramp assembly, or any efficient mechanical assembly capable of converting the rotary motion of the spindle into the linear motion of the piston. Examples of ball nut assemblies and ball ramp assemblies may be found in U.S. Patent No. 9,976,614 and U.S. Patent Application Publication No. 2019 / 0331180, the entire contents of which are incorporated herein by reference.

[0020] In this example, the ball nut 100 is coupled to the spindle 90 such that rotation of the spindle results in axial movement of the ball nut. In this way, the ball nut 100 acts as a piston to apply a braking force F during a braking operation.

[0021] Back to Figure 1 A control system 44 is provided to help control the operation of the vehicle 20, such as the operation of the propulsion system and the vehicle brakes, including the operation of the caliper assembly 60. To this end, the control system 44 may include one or more controllers, such as a propulsion system controller, a motor controller, and / or a brake controller. That is, the control system 44 is connected to and receives signals from various sensors that monitor vehicle functions and environmental conditions.

[0022] For example, the vehicle speed / acceleration sensor 50 monitors vehicle speed and acceleration and generates a signal indicative thereof. The road grade sensor 52 can detect or calculate the grade of the road on which the vehicle 20 is traveling and generate a signal indicative thereof. The ignition sensor 54 generates a signal indicative of the ignition state. The wheel speed sensor 58 is disposed on / near each wheel 32 and generates a signal indicative of the speed at each wheel. The control system 44 also receives a signal indicative of the degree to which the brake pedal 59 is depressed (including speed and acceleration).

[0023] The control system 44 can receive and interpret these signals and perform vehicle functions in response thereto, such as braking. In one example, the control system 44 can detect wheel slip between one or more wheels 30, 32 and the driving surface based on sensors 50, 58, and use one or more caliper assemblies 60 to perform anti-lock braking (ABS) and / or electronic stability control (ESC). The control system 44 can also be connected to an alarm 56 for notifying the driver / operator of the vehicle 20 of vehicle conditions, vehicle status, braking operations, and / or environmental conditions.

[0024] Reference FIG. 3A to FIG. 3B , a force sensing device or assembly 110 extends into the second passage 80 of the housing 70 and is connected to the spindle 90 and the ball nut 100 for sensing the reaction force applied to the spindle and the ball nut during the braking operation. The force sensing device 110 includes a housing 112 defining an interior space 114. The housing 112 extends into the second passage 80 of the housing 70 and is fixed to the housing so as to extend along or parallel to the centerline 72. A lateral opening 116 extends through the housing 112 and into the interior space 114 transversely (e.g., perpendicularly) to the centerline 72.

[0025] The openings 120, 122 are disposed at opposite longitudinal ends of the housing 112 on either side of the interior space 114. The openings 120, 122 are aligned with each other along the centerline 72. The spindle 90 and the ball nut 100 extend through the opening 122 and into the interior space 114. The sleeve 130 is also positioned within the interior space 114 and extends through the opening 122 out of the housing 112. The sleeve 130 includes an interior space 132 for receiving the ball nut 100 and the spindle 90. The spindle 90 extends through the opening 134 in the sleeve 130 toward the opening 120 in the housing 112. A bushing or bearing 136 is disposed on or integrally formed with the sleeve 130, aligned with the opening 134, for receiving the end of the spindle 90.

[0026] The cup gear 140 is axially disposed between the sleeve 130 and the housing 112 within the interior space 114. The cup gear 140 includes a first portion 142 having a torsion-resistant or rotation-resistant connection with the main shaft 90, such as a spline connection, a feather key connection, an interference fit, an adhesive connection, a fastener connection, a pin connection, a welded connection, an integrally formed connection, etc., for transmitting torque between the cup gear 140 and the main shaft 90. The cup gear 140 includes a second portion 144 that is aligned with the lateral opening 116 in the housing 112 and is configured to receive torque from a structure external to the housing 112.

[0027] To this end, Figure 4 In one example schematically shown in FIG. 1 , a motor 150 is provided for transmitting torque to the cup gear 140. To this end, the motor 150 includes an output pinion or motor gear 152. The motor 150 is activated to rotate the motor gear 152 about an axis 154 in a manner of R1 or R2 (counterclockwise or clockwise, respectively, as shown). A sensor 156, such as a magnetic or inductive position sensor, tracks the rotational position of the motor gear 152 relative to its axis 154.

[0028] The gear or gear train 158 meshes with the motor gear 152 and the cup gear 140 for transmitting torque therebetween. It should be understood that the gear train 158 may include one or more gears in any arrangement (e.g., series connection, planetary, etc.). Alternatively, the gear train 158 may be omitted and replaced with a belt drive, etc., as long as torque can be transmitted between the motor gear 152 and the cup gear 140. In addition, it is understood that the cup gear 140 may be omitted and replaced with a drive gear and drive plate (not shown).

[0029] Back to Figure 3B , the cup gear 140 also includes a recess or pocket 146 for receiving the load flange 160. The load flange 160 may have a generally T-shaped cross-sectional configuration and include a base 162 and a projection 164 extending from the base and aligned with but spaced from the terminal end of the main shaft 90. In other words, there is an axial space or gap between the end of the main shaft 90 and the projection 164. The thrust bearing 172 and the washer 174 are disposed in the pocket 146 between the load flange 160 and the first portion 142 of the cup gear 140. Thus, the load flange 160, the cup gear 140, the thrust bearing 172, and the washer 174 are concentric / aligned with each other along the centerline 72.

[0030] Force sensor 180( Figure 5) extends through the opening 120 of the housing 112 into the interior space 114 and extends along the centerline 72. In one example, the force sensor 180 is a button force sensor, but other configurations are also contemplated. Regardless, the force sensor 180 is connected to the control system 44 and is configured to send a signal thereto indicating the force experienced by the force sensor, such as a compressive force. To this end, the force sensor 180 may include a contact spring or contact pad for connecting the force sensor to the control system 44.

[0031] The force sensor 180 includes a radially extending flange 182 (see Figure 3B ), which is secured between the inner surface of the housing 112 and the load flange 160. This, in turn, secures the base 162 of the load flange 160 between the flange 182 of the force sensor 180 and the thrust bearing 172. Thus, the load flange 160 is prevented from rotating relative to the cup gear 140. The base 162 of the load flange 160 may include a guide feature (not shown) to help ensure that the force sensor 180 is properly positioned on the load flange, for example, centered on the load flange.

[0032] With this in mind, and returning to Figure 4 , the torque received by the cup gear 140 is transmitted to the main shaft 90, which rotates about the centerline 72 to generate axial movement of the ball nut 100. More specifically, providing torque to the gear train 158 to rotate the main shaft 90 in the R3 manner causes the ball nut 100 to advance toward the rotor 36 or 38 to brake the vehicle 20. On the other hand, providing torque to the gear train 158 to rotate the main shaft 90 in the R4 manner causes the ball nut 100 to retreat away from the rotor 36 or 38 to reduce or release the braking of the vehicle 20.

[0033] During operation of the vehicle 20, a service brake application request is initiated by the system and / or the vehicle operator. In this example, the wheel rotor 38 (see FIG. 1 ) of the single rear end 26 Figure 1 ) provides service braking. The braking demand is based on a signal received by the control system 44 due to the driver depressing the brake pedal 59 or due to an automatic vehicle safety system (such as a collision avoidance system).

[0034] With this in mind, the control system 44 activates the motor 150 to provide torque to the gear train 158, thereby rotating in the brake application direction R3 to provide torque to the spindle 90 along the aforementioned flow path. This in turn causes the ball nut 100 to apply a braking force F to the brake pad 37, thereby braking the rotor 38. The rotation of the motor 150 continues until the vehicle 20 responds to the commanded braking event, at which time the motor has a specific current consumption. That is, the control system 44 controls the caliper assembly 60 according to its model-based design, which establishes a correlation between the specific current consumption of the motor 150 and the resultant braking force F applied to the rotor 38.

[0035] It should be understood that the speed and torque of the motor 150 can be precisely controlled by the control system 44 using, for example, pulse width modulation (PWM) control. For example, the degree and / or rate of braking force F on the brake pad 37 during braking and the degree and / or rate of braking force reduction during an ABS event can be finely adjusted. In controlling PWM, the control system 44 can rely on signals from any sensor indicating, for example, road surface conditions.

[0036] In any case, go to Figure 6 When the motor 150 rotates in the brake application direction R1, the cup gear 140 rotates to transfer torque from the gear train 158 to the main shaft 90. However, due to the compressive force between the force sensor 180, the load flange and the thrust bearing 172, the load flange 160 does not rotate during this torque transfer. At the same time, the bushing / bearing 136 on the sleeve 130 helps to reduce the side load force acting on the thrust bearing 172 and the force sensor 180.

[0037] When the braking force F is applied to the pad 37, a reaction force RF is generated that travels back through the system. Specifically, the reaction force RF flows through the ball nut 100, the spindle 90, the first portion 142 of the cup gear 140, the washer 174, the thrust bearing 172, the base 162 of the load flange 160, through the force sensor 180, and into the housing 112 where the reaction force RF is ultimately transmitted to the caliper housing 70. These reaction forces RF are measured by the force sensor 180 (more specifically, the compressive forces acting on the flange 182), and signals representing the reaction forces are sent to the control system 44.

[0038] The reaction force RF is directly related to, e.g., proportional to, the braking force F applied by the ball nut 100 to the rotor 38. Therefore, the control system 44 can correlate the sensed reaction force RF with the applied braking force F. At the same time, the control system 44 relies on the magnetic position sensor 156 to track the rotation of the motor 150. The control system 44 is programmed to have an expected or theoretical correlation between the rotational position of the motor 150 and the reaction force RF, thereby inferring the braking force F.

[0039] However, certain factors may cause the rotational position of the motor 150 to deviate from the desired braking force F at the rotor 38. This may include, for example, tolerances in the gear train 158, the force sensing assembly 110, etc., and / or deviations in motor 150 performance / tolerances from the expected configuration. With this in mind, the control system 44 may adjust (e.g., increase) the current delivered to the motor 150 until the sensed reaction force RF reaches an amount equal to the desired braking force F at the rotor 38. Since each wheel rotor 36, 38 has an associated caliper assembly 60 and force sensing assembly 110, the control system 44 can accurately and independently control the braking force F at each rotor 38 by monitoring the rotational position of the corresponding motor 150 and the reaction force RF at the corresponding force sensing device 110. This precise control enables the control system 44 to account for variations in and between the caliper assembly 60, the force sensing assembly 110, the brake pads, etc.

[0040] When braking is reduced or terminated, the control system 44 causes the motor 150 to move in direction R2 ( Figure 3A ) is rotated to retract the ball nut 100 from the rotor. The force sensing assembly 110 is configured so that the reaction force RF during the braking operation is less than or equal to the capacity of the force sensor 180 under all reasonably expected operating conditions.

[0041] An advantage of the force sensing assembly of the present invention is that it enables the control system to correct the motor current applied to any / all caliper assemblies to help ensure that the braking force is correct in terms of the desired degree and distribution between the wheels. The force sensing assembly also allows the control system to adapt over time to changes in component interrelationships, wear, motor degradation or performance reduction, etc. When a button-type force sensor is employed, the assembly can provide higher measurement accuracy while reducing cost and packaging compared to other force sensor configurations.

[0042] What has been described above are examples of the present invention. Of course, it is not possible to describe every conceivable combination of components or methods for the purpose of describing the present invention, but those skilled in the art will recognize that many other combinations and arrangements of the present invention are possible. Therefore, the present invention is intended to include all such changes, modifications and variations that fall within the spirit and scope of the appended claims.

Claims

1. An electromechanical brake assembly for a vehicle having a caliper assembly driven by an electric motor, the electromechanical brake assembly for the vehicle comprising: a cup gear for receiving torque from the motor and transmitting the torque to the main shaft; a piston coupled to the spindle and axially movable relative to the spindle in response to rotation of the spindle to brake the vehicle during a braking operation; a force sensor aligned with the main shaft and the cup gear for sensing a reaction force applied to the piston during the braking operation; as well as A thrust bearing is provided for transmitting the reaction force from the cup gear to the force sensor.

2. The assembly of an electromechanical brake for a vehicle according to claim 1, further comprising a controller connected to the force sensor and configured to adjust the torque applied to the main shaft in response to receiving a signal from the force sensor indicating the reaction force.

3. The electromechanical brake assembly for a vehicle according to claim 2, wherein: The force sensor includes one of a contact spring and a contact pad for connecting the force sensor to the controller.

4. The electromechanical brake assembly for a vehicle according to claim 1, further comprising: a housing for receiving the cup gear and receiving at least a portion of the main shaft and the piston; as well as A load flange is received by the cup gear and is positioned axially between the main shaft and the force sensor for transmitting a reaction force from the cup gear to the force sensor.

5. The electromechanical brake assembly for a vehicle according to claim 4, wherein: The load flange abuts the force sensor but is axially spaced from the spindle.

6. The electromechanical brake assembly for a vehicle according to claim 4, wherein: The force sensor includes a base secured between the housing and the load flange and a protrusion extending from the base through an opening in the housing.

7. The electromechanical brake assembly for a vehicle according to claim 4, wherein: The housing includes a laterally extending opening for receiving structure for transmitting torque between the motor and the cup gear.

8. The electromechanical brake assembly for a vehicle according to claim 1, wherein: The cup gear has a non-rotational connection to the main shaft.

9. The electromechanical brake assembly for a vehicle according to claim 1, wherein: The piston includes one of a ball nut and a ball ramp.

10. The electromechanical brake assembly for a vehicle according to claim 1, wherein: The force sensor includes a button force sensor.

11. An electromechanical brake assembly for a vehicle having a caliper assembly driven by an electric motor, the electromechanical brake assembly for the vehicle comprising: Spindle; a piston coupled to the spindle and axially movable relative to the spindle in response to rotation of the spindle to brake the vehicle during a braking operation; a cup gear for receiving torque from the motor and transmitting the torque to the main shaft; a housing for receiving the cup gear and receiving at least a portion of the main shaft and the piston; a button force sensor aligned with the spindle and the cup gear for sensing a reaction force applied to the piston during the braking operation; a thrust bearing for transmitting the reaction force from the cup gear to the force sensor; a load flange received by the cup gear and positioned axially between the spindle and the force sensor for transmitting a reaction force from the cup gear to the force sensor; as well as A controller is connected to the button force sensor and is configured to adjust a torque applied to the spindle in response to receiving a signal from the force sensor indicative of the reaction force.

12. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The load flange abuts the force sensor but is axially spaced from the spindle.

13. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The force sensor includes a base secured between the housing and the load flange and a protrusion extending from the base through an opening in the housing.

14. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The housing includes a laterally extending opening for receiving structure for transmitting torque between the motor and the cup gear.

15. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The cup gear has a non-rotational connection to the main shaft.

16. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The piston includes one of a ball nut and a ball ramp.

17. The electromechanical brake assembly for a vehicle according to claim 11, wherein: The force sensor includes one of a contact spring and a contact pad for connecting the force sensor to the controller.

18. A method for controlling a caliper assembly of a vehicle, the method comprising the steps of: applying current to a motor for actuating the caliper assembly to initiate a braking operation; monitoring rotation of the electric motor during the braking operation; sensing a reaction force through the caliper assembly during the braking operation; and The current applied to the motor is adjusted until the sensed reaction force reaches a predetermined amount.

19. The method according to claim 18, wherein: The reaction force is applied to the button force sensor.

20. The method according to claim 18, wherein: Adjusting the current applied to the motor includes increasing the current applied to the motor until the sensed reaction force reaches the predetermined amount.

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