Clamping force sensor and electromechanical brake

Abstract

The utility model relates to a clamping force sensor for an electronic mechanical brake and the electronic mechanical brake. The clamping force sensor comprises an outer housing (15); a strain body (16) configured to generate a strain when subjected to a force; the micro electro mechanical unit (17) is mounted on the end surface of the strain body (16) and is used for converting the strain of the strain body (16) into an electric signal.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of clamping force sensors for electronic mechanical brake and electronic mechanical brake with such clamping force sensor. BACKGROUND

[0002] With the development of automobile electrification, electronic mechanical brake is increasingly applied in motor vehicles.And in electronic mechanical brake, clamping force sensor is needed to detect actual braking force.

[0003] The clamping force sensor of prior art is generally arranged in the braking force transmission path of brake, for example, arranged in the ball screw mechanism of actuator.For example, it is known that annular sensor and solid sensor receive the axial force of screw via thrust bearing scheme.While these traditional sensors may face the following challenges:

[0004] Axial space occupation

[0005] Electronic mechanical brake is arranged at wheel edge, and is influenced by hub, suspension, steering mechanism.Therefore, arrangement space is extremely limited, annular and solid sensor are coaxially arranged with ball screw, and both increase the axial dimension of electronic mechanical brake, generally increase 12-18mm, for example.

[0006] Sensor accuracy and durability

[0007] The sensing unit of annular sensor is uniformly arranged on circumference, due to installation error and long-term movement of ball screw, there is the possibility of axial force deviation.This can bring the risk of uneven distribution of sensor radial sensing force, thus causing sensor to have problems such as accuracy reduction, zero drift, etc.

[0008] Arrangement of sensor affects the design of electronic mechanical brake

[0009] Solid sensor can only be installed at the shaft end of ball screw mechanism, and the internal structure of brake must adapt to solid sensor.Therefore, the internal structure of brake itself is greatly limited.

[0010] Sensor cost

[0011] The cost of existing force sensor is high, and the mechanical part accounts for 70%.Because the machining precision of mechanical part is high, the total cost of force sensor assembly accounts for about 10%-15% of the total cost of electronic mechanical brake assembly.This is a major obstacle to mass production of force sensor.

[0012] Universality or compatibility

[0013] Annular sensor and solid sensor both need to be designed according to the internal structure of electronic mechanical brake, screw diameter, bearing, etc., and cannot realize platform application. Utility model content

[0014] The utility model aims at solving at least one of above problems.

[0015] According to one aspect of the utility model, a clamping force sensor for an electromechanical brake is provided, comprising:

[0016] An outer shell;

[0017] A strain body configured to generate strain under the action of force;

[0018] A micro-electro-mechanical unit mounted on an end face of the strain body and configured to convert the strain of the strain body into an electrical signal.

[0019] According to a preferred embodiment, the clamping force sensor is configured to be directly arranged in a caliper body of a brake caliper of an electromechanical brake, and the brake force of the electromechanical brake is obtained by detecting the deformation of the caliper body.

[0020] According to a preferred embodiment, the clamping force sensor further comprises a probe groove connected with or integrally formed with the outer shell, and the strain body is embedded in the probe groove in a press-fit manner.

[0021] According to a preferred embodiment, the micro-electro-mechanical unit is configured as a piezoresistive pressure sensing unit having a full-bridge structure.

[0022] According to a preferred embodiment, the piezoresistive pressure sensing unit comprises a layered arrangement of a metal substrate, a glass base and a silicon piezoresistive film.

[0023] According to a preferred embodiment, the clamping force sensor further comprises a signal conditioning and amplification circuit arranged in the outer shell and electrically connected with the micro-electro-mechanical unit.

[0024] According to a preferred embodiment, the clamping force sensor further comprises an electrical plug arranged at an end of the outer shell opposite to the micro-electro-mechanical unit.

[0025] According to a preferred embodiment, the electrical plug comprises at least a power supply end, a ground end and an output end.

[0026] According to a preferred embodiment, a corresponding relationship between the clamping force of the brake caliper and the strain at the clamping force installation position is stored in the micro-electro-mechanical unit, and the corresponding relationship is stored in the form of a lookup table or a characteristic curve.

[0027] According to another aspect of the utility model, an electromechanical brake is provided, which has the clamping force sensor according to the utility model.

[0028] According to a preferred embodiment, the electromechanical brake comprises a brake caliper, the clamping force sensor being arranged in a caliper body of the brake caliper. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A schematic block diagram of an electromechanical brake for a motor vehicle is shown.

[0030] Figure 2 A schematic block diagram of the application of the force sensor signal in an ESP controller is shown.

[0031] Figure 3 A schematic perspective view of a clamping force sensor is shown.

[0032] Figure 4 A schematic side view of a clamping force sensor is shown.

[0033] Figure 5 A schematic sectional view of a clamping force sensor along the line A-A is shown. Figure 4

[0034] Figure 6 A schematic top view of a microelectromechanical unit is shown.

[0035] Figure 7 A schematic partial sectional view of a microelectromechanical unit is shown.

[0036] Figure 8 A schematic sectional view of an electromechanical brake with a clamping force sensor mounted is shown.

[0037] LIST OF REFERENCE SIGNS

[0038] 1 brake caliper

[0039] 2 brake disc

[0040] 3 brake pad

[0041] 4 power supply port

[0042] 5 communication port

[0043] 6 electric motor

[0044] 7 control unit

[0045] 8 power electronics of the electric motor

[0046] 9 rotary-translation conversion mechanism

[0047] 10 park drive

[0048] 11 park brake actuator

[0049] 12 park brake mechanism ​

[0050] 13 decelerator

[0051] 14 clamping force sensor

[0052] 15 outer housing

[0053] 16 strain body

[0054] 17 microelectromechanical unit

[0055] 18 probe slot

[0056] 19 lead wire

[0057] 20 signal conditioning amplifier circuit

[0058] 21 metal substrate

[0059] 22 glass base

[0060] 23 silicon piezoresistive thin film

[0061] 24 electrical plug

[0062] 25 caliper body of a brake caliper

[0063] V voltage

[0064] I current

[0065] P1 position of the electric motor

[0066] P2 position of the parking brake mechanism

[0067] T temperature

[0068] F force

[0069] W brake pad wear

[0070] TQ torque

[0071] S wheel speed DETAILED DESCRIPTION

[0072] A clamping force sensor for an electromechanical brake and an electromechanical brake according to the present application will be described below with reference to the accompanying drawings and by way of specific embodiments. The exemplary embodiments, however, can be implemented in various forms and should not be construed as being limited to the implementations set forth herein; rather, the implementations are provided so that the present application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0073] Figure 1 A schematic block diagram of an electromechanical brake for a motor vehicle is shown. In this example, the electromechanical brake is schematically shown as a caliper disc brake, of course, the present application can also be applied to drum brakes.

[0074] As Figure 1 shown, an electromechanical brake generally comprises a brake mechanism and an actuator 100. In this example, the brake mechanism comprises a brake caliper 1 mounted in a non-rotating manner relative to the vehicle body, which during braking acts on, in particular clamps, a brake disc 2 fixed relative to the wheel, in order to slow the wheel down. On the brake caliper 1 are generally mounted brake pads 3 (or also called linings or pads), by means of which the brake caliper 1 contacts the brake disc 2.

[0075] The brake caliper 1 is manipulated by the actuator 100 of the brake. As Figure 1 shown, the actuator 100 comprises a power supply port 4 and a communication port 5. The power supply port 4 is used to supply power to the actuator 100, in particular to the power electronics 8 and the control unit 7 of the electric motor 6. The actuator 100 communicates with other devices via the communication port 5, for example to obtain brake demand signals and to deliver brake feedback. The control unit 7 communicates with the power electronics 8 of the electric motor 6, in order to on the one hand transmit control signals to the electric motor 6 and on the other hand to receive feedback signals from the electric motor 6. The electric motor 6 is connected to the brake caliper 1 via a speed reducer 13 and a rotary-translation conversion mechanism 9 (for example a ball screw mechanism), and is thus able to transmit a brake force to the brake caliper 1, causing the brake caliper 1 to clamp the brake disc 2. The speed reducer 13 and the rotary-translation conversion mechanism 9 can also be integrated as an integral motor drive.

[0076] Optionally, a parking brake can also be integrated in the brake, which comprises a parking brake actuator 10, a parking brake mechanism 12 and a parking brake actuator 11.

[0077] As Figure 1 shown, the control unit 7 receives feedback signals for controlling or regulating the brake force, etc. The feedback signals can include at least one of the following signals: voltage V and current I of the power electronics 8 of the electric motor 6, temperature T of the brake, position P1 of the electric motor 6 and position P2 of the parking brake mechanism 12, clamping force F of the brake caliper 1, wheel speed S, brake pad wear W and torque TQ of the brake caliper 1.

[0078] The above-mentioned feedback signals can come from corresponding sensors or from calculation results. These feedback signals and other signals are transmitted to the control unit 7, providing the control unit 7 with accurate information about the current state of the vehicle. The control unit 7 receives these data and, based on these data and other factors (such as vehicle weight, road conditions and driving mode, etc.), calculates the required brake force. The control unit 7 is also responsible for adjusting the brake force distribution, ensuring that the vehicle remains stable when braking, especially when emergency braking or cornering. Once the control unit 7 calculates the required brake force, it instructs the actuator to provide the corresponding brake force.

[0079] Among the above-mentioned feedback signals, the feedback of the brake force is essential. In order to accurately perform the basic braking, dynamic control, etc. (such as ABS, ESP), it is necessary to accurately acquire the clamping force applied to the brake caliper 1. Figure 2 The application of the brake force sensor signal is illustrated by way of example with the ESP (electronic stability program) control. One of the cores of the ESP is the slip ratio control of the individual wheels, and the accuracy of the slip ratio control depends on the accuracy of the implementation of the brake caliper clamping force. By measuring the clamping force of the brake caliper in real time with the sensor, a three-closed-loop control of the electromechanical brake, i.e. the current loop, the motor speed loop, and the brake caliper clamping force loop, can be simultaneously achieved.

[0080] The existing clamping force sensors are generally arranged in the ball screw mechanism of the actuator. In this case, both the ring sensor and the solid sensor have the disadvantages of poor accuracy, poor durability, high cost, high space occupation, and poor universality.

[0081] In the utility model, a clamping force sensor for an electromechanical brake is proposed. The clamping force sensor aims to acquire the clamping force of the brake caliper by detecting the deformation of the caliper body of the brake caliper. Thus, the clamping force sensor can be configured to be directly arranged in the caliper body of the brake caliper, and the clamping force of the brake caliper is acquired by sensing the deformation of the caliper body. A preferred embodiment of such a clamping force sensor is schematically shown in Figures 3-5 .

[0082] As shown in Figure 3 , the clamping force sensor 14 of the utility model mainly comprises an outer housing 15, a strain body 16, and a micro-electromechanical unit (MEMS) 17. The strain body 16 is configured to generate strain under the action of force. The micro-electromechanical unit 17 can be installed on the end face of the strain body 16 and is used to convert the strain of the strain body 16 into an electrical signal. The outer housing 15 can be used to receive at least a part of the strain body 16, and can thereby electrically connect the strain body 16 and the micro-electromechanical unit 17 thereon to a signal processing part, such as a signal conditioning and amplification circuit to be described below, for generating a sensor signal.

[0083] Advantageously, the strain body 16 can be installed in a probe groove 18. The probe groove 18 can be formed by a part of the outer housing 15 or by a separate component connected to the outer housing 15. As shown in Figure 3 , the probe groove 18 can be formed at a position protruding relative to the main body part of the outer housing 15, so as to facilitate the contact of the strain body 16 with the component to be detected, such as the housing of the brake caliper.

[0084] The material of the outer housing 15 and the probe slot 18 is stainless steel, which is a known material. The base material of the strain body 16 is cast iron, in particular nodular cast iron. The nodular cast iron is a known material. The strain body 16 can be inserted into the probe slot 18 by a press fit. As can be seen from Figure 8 the clamping force sensor 14 can be mounted in the caliper body of the brake caliper by the outer housing 15 in an interference fit. For this purpose, a receptacle can be provided in the caliper body of the brake caliper 1 which matches the shape of the outer housing 15 of the clamping force sensor 14, in order to insert the outer housing 15 and in particular the portion of the outer housing 15 having the probe slot 18 into the receptacle. As a result, a strain of the caliper body causes the probe slot 18 to press against the strain body 16, which leads to a deformation of the strain body 16, which can be detected by the microelectromechanical unit 17.

[0085] As shown in Figure 5 , the clamping force sensor 14 further comprises an electrical plug 24 arranged at the end of the outer housing 15 opposite the microelectromechanical unit 17. The electrical plug 24 is for example provided as a 4 PIN, with a 5V supply, a ground, a SENT (single edge nibble transmission) output and a reserved port. The SENT signal used in this design is a digital signal, which has a higher transmission accuracy and speed compared to an analog signal. Of course, other arrangements of the electrical plug 24 are also conceivable. The electrical plug 24 can be electrically connected to the microelectromechanical unit 17 via the signal conditioning amplifier circuit 20.

[0086] The signals from the microelectromechanical unit 17 are transmitted via the lead 19 to the signal conditioning amplifier circuit 20, which processes the signals and outputs them via the electrical plug 24, for example as a 0-5V voltage signal. The signal conditioning amplifier circuit 20 can perform at least one of the following functions: sensor sensitivity compensation, sensor zero offset compensation, sensor non-linearity compensation, sensor temperature drift compensation, power management, signal amplification and signal output.

[0087] An example of the microelectromechanical unit 17 is shown in Figure 6 and Figure 7 , which is for example configured as a piezoresistive pressure sensing unit. The piezoresistive pressure sensing unit has a full bridge structure. As shown in Figure 7 , the piezoresistive pressure sensing unit comprises a layered arrangement of a metal substrate 21, a glass base 22 and a silicon piezoresistive membrane 23.

[0088] During braking, the strain at each position on the brake caliper body changes with the brake clamping force. By means of pre-tests or tests, a correspondence between brake clamping force and strain at the respective position can be obtained. This correspondence can be stored in the micro- electromechanical unit 17 or in the control unit 7 of the brake, for example in the form of a look-up table or a characteristic curve.

[0089] In use, the clamping force sensor 14 can be mounted at a specific position on the brake caliper body, which position can be chosen by a skilled person depending on the specific brake arrangement, as will be discussed further below. During operation of the brake, when the brake caliper is clamped, the caliper body will be mechanically strained by the clamping force, which in turn will cause a compression of the clamping force sensor 14 mounted in the caliper body, in particular of the housing 15 or more specifically of the probe slot 18, which in turn will cause a strain of the strain body 16. The micro-electromechanical unit 17 detects the strain of the strain body 16. In combination with the pre-stored look-up table or characteristic curve, the micro-electromechanical unit 17 can calculate the clamping force corresponding to the detected strain and transmit this clamping force in the form of a signal to the control unit 7 of the brake. Alternatively, it is also conceivable that the micro-electromechanical unit 17 directly transmits the strain or stress in the form of a signal to the control unit 7 and calculates the clamping force corresponding to the detected strain in combination with the pre-stored look-up table or characteristic curve in the control unit 7.

[0090] In the following, examples of mounting positions of the clamping force sensor 14 on the brake caliper body will be discussed in detail. A simulation stress calculation can be performed for the brake caliper body. Based on the results of the static structure and the minimum principal stress simulation, a number of, for example 7, possible mounting positions can be selected for simulation analysis. In one exemplary analysis, a brake clamping force of 45 KN is applied to the brake caliper and the relationship between the clamping force and the stress perceived at the 7 positions is analyzed. Here, two parameters are mainly analyzed, namely the sensitivity coefficient and the hysteresis percentage. The sensitivity coefficient is defined as the amount of change in the sensor output signal caused by a unit change in stress, the higher the sensitivity, the higher the sensor accuracy. The hysteresis percentage is defined as the difference between the sensor signals corresponding to the same clamping force during the application and release of the brake calamping force. The reason for the different stresses at the same clamping force is that the structural stresses during brake clamping and release are completely different. The smaller the hysteresis percentage, the higher the sensor accuracy. In the example here, the mounting position is determined by taking into account both the sensitivity coefficient and the hysteresis percentage. Of course, other factors can also be taken into account when determining the mounting position, for example the operating temperature.

[0091] Of course, instead of the simulation process described above, the mounting position of the clamping force sensor 14 can also be determined by real tests.

[0092] The sensor can realize platform design, and the installation position of the clamping force sensor can be selected according to needs for different specifications of the brake. Since the clamping force sensor of the utility model does not have to be installed coaxially with the ball screw, neither the axial size of the original actuator is increased, nor the problem of axial force bias exists, so that the problem of long-term use of precision and durability reduction will not occur. In addition, the structure of the clamping force sensor of the utility model is regular, and the cost of the mechanical part is low.

[0093] Obviously, various modifications and variations of the embodiments disclosed herein can be made by those skilled in the art without departing from the scope or spirit of the present application. Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the present application disclosed herein. This specification and the examples provided should be considered exemplary only.

Claims

1. A clamp force sensor for an electromechanical brake, characterized by The clamping force sensor comprises: an outer housing (15); a strain body (16) configured to generate strain under the action of force; a micro-electro-mechanical unit (17) mounted on an end face of the strain body (16) and configured to convert the strain of the strain body (16) into an electrical signal.

2. The clamp force sensor of claim 1, wherein, The clamping force sensor is configured to be directly arranged in a caliper body of a brake caliper of an electromechanical brake, and to obtain the braking force of the electromechanical brake by detecting the deformation of the caliper body.

3. The clamp force sensor of claim 1, wherein, The clamping force sensor further comprises a probe groove (18) connected with or formed integrally with the outer housing (15), and the strain body (16) is embedded in the probe groove (18) in a press-fit manner.

4. The clamp force sensor of claim 1, wherein, The micro-electro-mechanical unit (17) is configured as a piezoresistive pressure sensing unit having a full-bridge structure.

5. The clamp force sensor of claim 4, wherein, The piezoresistive pressure sensing unit comprises a layered arrangement of a metal substrate (21), a glass base (22), and a silicon piezoresistive film (23).

6. The clamp force sensor of claim 1, wherein, The clamping force sensor further comprises a signal conditioning and amplification circuit (20) arranged in the outer housing (15) and electrically connected with the micro-electro-mechanical unit (17).

7. The clamp force sensor of claim 1, wherein, The clamping force sensor further comprises an electrical plug (24) arranged at an end of the outer housing (15) opposite to the micro-electro-mechanical unit (17).

8. The clamp force sensor of claim 7, wherein, The electrical plug (24) comprises at least a power supply terminal, a ground terminal, and an output terminal.

9. The clamp force sensor of claim 1, wherein, A corresponding relationship between the clamping force of the brake caliper and the strain at the clamping force installation position is stored in the micro-electro-mechanical unit (17), and the corresponding relationship is stored in the form of a lookup table or a characteristic curve.

10. An electromechanical brake characterized by The electromechanical brake has an actuator and the clamping force sensor according to any one of claims 1-9.

11. The electromechanical brake according to claim 10, characterized in that The electromechanical brake comprises a brake caliper, and the clamping force sensor is arranged in a caliper body of the brake caliper.

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