Electromechanical brake booster

Abstract

To suppress heat generation of a motor of an electromechanical brake booster mainly in a vehicle stop state.SOLUTION: An electromechanical brake booster 1 mounted on a vehicle includes: an input rod 20 coupled to a brake pedal BP; a control rod 30; a rod position sensor 40; a motor part 50; a rotation position sensor 60; a current sensor 70; and a control board 80 driving the motor part 50 by using information obtained from the respective sensors 40, 60, 70. Basic control controlling a rotary position of the motor part 50 as the control rod 30 is displaced, and current control controlling supply current for the motor part 50 on the basis of information of the current sensor 70 are performed simultaneously.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electromechanical brake booster for amplifying the force applied when the brake pedal is depressed in an automobile. [Background technology]

[0002] Conventionally, brake boosters have been known to amplify the force applied when the brake pedal is pressed to assist in braking in automobiles. Vacuum brake boosters that utilize the engine's negative pressure have been commonly used, but in recent years, cars without engines, such as electric cars and fuel cell cars, have been released, which has created a need for a different type of brake booster.

[0003] Therefore, electromechanical brake boosters equipped with a motor as a power source are known, such as the inventions described in Patent Publication No. 2018-199448 (Patent Document 1) and Patent Publication No. 2018 / 097278 (Patent Document 2). In addition, the applicant of the present application has also proposed electromechanical brake boosters and control methods thereof, as disclosed in Patent Publication No. 2023-021860 (Patent Document 3), Patent Publication No. 2023-030664 (Patent Document 4), and Patent Publication No. 2023-037382 (Patent Document 5).

[0004] These electromechanical brake boosters make it possible to amplify the force applied when stepping on the brake pedal by using an electrically powered motor, even in vehicles without engines.

[0005] The electromechanical brake booster devices described in Patent Documents 3-5 control a shaft member (feed screw) integrated with a position sensor by rotating a motor unit integrated with a nut-shaped rotating member, so that the positional relationship between the control rod linked to the brake pedal and the position sensor that monitors the control rod is always constant.

[0006] The shaft member (feed screw) has an end face that contacts the master cylinder, which is the output of the booster, and is a component that transmits the rotational torque of the motor as an axial load. As a result, the control allows the force generated by the motor torque to function as a booster, following the movement of the brake pedal.

[0007] In this mechanism, the control continues even after the vehicle has stopped, so the load on the motor is large when the vehicle is stopped, and heat generation in the motor due to the continued vehicle stop state is an issue.

[0008] Common countermeasures against heat generation include designing the exterior to dissipate heat and improving motor performance, but these are undesirable as they lead to increased product size and costs.

[0009] Furthermore, since the holding force required to stop the vehicle is smaller than the braking force required during deceleration, there is a risk that the booster will generate excessive motor torque when the vehicle is stopped. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-199448 [Patent Document 2] Re-tabled publication 2018 / 097278 [Patent Document 3] Japanese Patent Publication No. 2023-021860 [Patent Document 4] Japanese Patent Publication No. 2023-030664 [Patent Document 5] Japanese Patent Publication No. 2023-037382 Summary of the Invention [Problem to be solved by the invention]

[0011] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problem of heat generation in the motor of an electromechanical brake booster mainly when the vehicle is stopped. [Means for solving the problem]

[0012] The present invention, which has been made to solve the above problems, is an electromechanical brake booster mounted on a vehicle, comprising: an input rod connected to a brake pedal; a control rod having a cylindrical detectable body attached to its outer periphery and moving linearly in the axial direction in conjunction with operation of the brake pedal in conjunction with the input rod; a rod position sensor that detects displacement of the control rod by detecting displacement of the detectable body; a motor unit that operates in response to displacement of the control rod; a rotational position sensor that detects the rotational position and rotational speed of the motor unit; a current sensor that detects UVW phase currents of the motor unit; and a control board that drives the motor unit using information obtained from the rod position sensor, the rotational position sensor, and the current sensor; The present invention is characterized by simultaneously executing basic control, which controls the rotational position of the motor unit in accordance with the displacement of the control rod, and current control, which controls the current supplied to the motor unit based on information from the current sensor.

[0013] According to the above invention, in addition to the basic control of amplifying the brake pedal force by the motor unit, current control of controlling the current supplied to the motor unit is simultaneously performed, thereby making it possible to avoid the generation of excessive motor torque and suppress heat generation in the motor unit.

[0014] In the present invention, an external sensor for detecting the driving state of the vehicle is further provided, and when the external sensor detects that the driving state of the vehicle is stopped and the rod position sensor detects that the brake pedal is depressed, if the current supplied to the motor is limited, it is recognized that the brake has been activated and the vehicle has stopped, and the problem of heat generation in the motor of the electromechanical brake booster when the vehicle is stopped can be solved.

[0015] In the present invention, the upper limit value of the current supplied to the motor unit is constant for a predetermined time from the time the external sensor detects that the vehicle is stopped, and if the upper limit value is gradually reduced after the predetermined time has elapsed, it is possible to minimize the discomfort felt by the driver due to the reaction force from the brake pedal. [Effects of the Invention]

[0016] According to the present invention, by controlling the current supplied to the motor, it is possible to solve the problem of heat generation in the motor of the electromechanical brake booster mainly when the vehicle is stopped. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a preferred embodiment of an electromechanical brake booster according to the present invention; [Figure 2] FIG. 2 is an enlarged partial cross-sectional view of the embodiment shown in FIG. [Figure 3] 4 is a graph showing the correlation between the driving conditions of a vehicle equipped with an electromechanical brake booster according to the present invention and the state of the booster. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] 1 and 2 are diagrams showing a preferred embodiment of the electromechanical brake booster of the present invention, and this electromechanical brake booster 1 has a casing 10, an input rod 20, a control rod 30, a rod position sensor 40, a motor unit 50, a rotational position sensor 60, a current sensor 70, a control board 80, a rotary-to-linear motion conversion unit 90, a bracket 100, a support 110, a return spring 120, and a master cylinder 130.

[0020] The casing 10 is composed of a cylindrical cover 11 and a doughnut-shaped bottom plate 12 .

[0021] The input rod 20 is rod-shaped overall, can move axially, and can swing within a certain angular range. One end of the input rod 20 is connected to a control rod 30 inserted into a connecting hole 21 formed therein, and the other end of the input rod 20 is connected to the brake pedal BP.

[0022] The control rod 30 is rod-shaped overall and can move axially. One end (the input rod 20 side) has a ball stud 32 fixed thereto with a cylindrical object to be detected 31, which is a magnet for position detection, mounted thereon so that it cannot fall off. The other end has a step 34 for engaging with a plate 33 and a small-diameter tip 36 for mounting a coil spring 35 thereon.

[0023] The input rod 20 and the control rod 30 are connected by crimping via the ball stud 32 attached to the control rod 30, thereby forming a ball joint mechanism.

[0024] The rod position sensor 40 has a function of detecting the amount of displacement of the detection object 31 and outputting it as a signal.

[0025] The motor section 50 includes a stator 51, a rotor 52, a rotating member 53 that rotates in synchronization with the rotor 52, and two bearings 54 and 55 that support the rotating member 53 rotatably in the circumferential direction.

[0026] Reference numeral 56 denotes a detection magnet for detecting the rotational position, and reference numeral 57 denotes a motor cover that is attached to stand on the bottom plate 12 and covers the motor section 50.

[0027] The rotational position sensor 60 is a Hall sensor that has the function of detecting the rotational position and rotational speed of the detection magnet 56 and outputting the results as a signal.

[0028] The current sensor 70 has a function of detecting the current of the UVW phases of the motor unit 50 and outputting it as a signal.

[0029] The control board 80 has a motor driver function for controlling the power supplied from the outside to drive the motor unit 50, and is connected to the rod position sensor 40 via a cable. The control board 80 drives the motor unit 50 using information obtained from signals output from each sensor, including the rotational position sensor 60 and the current sensor 70, which are mounted on the control board 80.

[0030] In this embodiment, two sets of rotational position sensors 60 and corresponding detection magnets 56 are provided, and by using two rotational position sensors, it is possible to achieve both high precision and high speed in motor control, but it is also possible to provide only one set of rotational position sensors and corresponding detection magnets.

[0031] The rotary-to-linear motion conversion unit 90 is a mechanism for converting the rotary motion of the motor unit 50 into linear motion, and is composed of a feed screw mechanism consisting of a cylindrical shaft member 91 having a thread formed on its outer peripheral surface, and the nut-shaped rotating member 53 having a thread groove formed on its inner peripheral surface and threadedly fitted onto the shaft member 91.

[0032] The bracket 100 is attached to three support columns 110, and is configured to be non-rotatable but movable in the axial direction.

[0033] One end of the shaft member 91 is fixed to the bracket 100, and the bracket 100 restricts the axial rotation of the shaft member 91 and moves in conjunction with the shaft member 91 in the axial direction.

[0034] The support columns 110 are three in number and are installed between the cover 11 and the bottom plate 12 .

[0035] The return springs 120 are used to urge the bracket 100 back to its original position after movement, and are attached to the support posts 110, with one end contacting the bottom plate 12 and the other end contacting the bracket 100.

[0036] The master cylinder 130 consists of a cylinder bore 131, a first piston 132 arranged in the cylinder bore 131, and a second piston 133 arranged in the cylinder bore 131 closer to the bottom than the first piston 132, and is attached so as to close the opening below the casing 10.

[0037] The master cylinder 130 is connected to the tip end side of the control rod 30 and the shaft member 91 , and is operated by the linear motion of the control rod 30 or the shaft member 91 .

[0038] An elastic body 134 which is a reaction disk is fitted into the first piston 132, and the tip portion 36 of the control rod 30 comes into contact with the elastic body 134.

[0039] In this embodiment, the input rod 20, the control rod 30, the motor section 50, the rotary-to-linear motion conversion section 90, the bracket 100 and the master cylinder 130, which are directly related to the operation of the brake booster, are all arranged coaxially, making it possible to configure the brake booster in a space-saving manner overall.

[0040] The operation of the electromechanical brake booster 1 according to this embodiment will now be described.

[0041] When the electromechanical brake booster 1 is installed in an automobile and the driver operates (depresses) the brake pedal BP, the input rod 20 connected to the brake pedal BP moves in the axial direction as the brake pedal BP moves, and the control rod 30 moves linearly in synchronization with the input rod 20.

[0042] At this time, the control rod 30 and the shaft member 91 are not synchronized and can move independently in the axial direction, so the position of the shaft member 91 does not change and only the control rod 30 moves.

[0043] Then, the control rod 30 moves the first piston 132 and the second piston 133 forward against the biasing force of the coil spring 35 and the coil springs in the master cylinder 130 .

[0044] Furthermore, when the control rod 30 moves, the rod position sensor 40 detects the displacement and sends a signal to the control board 80, which then controls the supply of power and an actuation signal to the motor unit 50, causing the motor unit 50 to operate and rotate.

[0045] In addition, the rotational position sensor 60 is provided, and the signal sent from the rotational position sensor 60 to the control board 80 can be used when the control board 80 controls the supply of power and operating signals to the motor unit 50.

[0046] When the motor unit 50 rotates, the rotating member 53 rotates in synchronization with the rotor 52, but since the axial rotation of the threadedly engaged shaft member 91 is restricted by the bracket 100, the rotational movement of the rotating member 53 is converted into linear movement, and the first piston 132 and the second piston 133 on the axis move forward.

[0047] At this time, the bracket 100 also moves in synchronization with the shaft member 91 in a direction that compresses the return spring 120 and moves the first piston 132 and the second piston 133 on the axis forward.

[0048] Then, the shaft member 91 moves the first piston 132 and the second piston 133 forward against the biasing force of each coil spring in the master cylinder 130 via the plate 33 .

[0049] In this way, the force exerted when the driver depresses the brake pedal BP is applied directly to the first piston 132 and the second piston 133 of the master cylinder 130 via the input rod 20 and the control rod 30, and in addition, the pressing force obtained by converting the rotational movement of the motor unit 50 into linear movement of the shaft member 91 is applied to the first piston 132 and the second piston 133 of the master cylinder 130 via the shaft member 91.Therefore, by using an electrically powered motor, the force exerted when the brake pedal BP is depressed can be amplified.

[0050] Then, as the driver releases the brake pedal BP and the brake pedal BP returns to its original position, the input rod 20 and the control rod 30 connected to the brake pedal BP also return to their original positions, and as the control rod 30 moves, the control board 80 controls the supply of power and an actuation signal to the motor unit 50 in response to a signal from the rod position sensor 40 which detects the displacement, and the motor unit 50 operates to rotate in the reverse direction.

[0051] When the motor unit 50 rotates in the reverse direction, the rotating member 53 rotates in the reverse direction in synchronization with the rotor 52, but since the axial rotation of the shaft member 91 is restricted by the bracket 100, the rotational movement of the rotating member 53, which is threadedly engaged, is converted into linear movement, and the first piston 132 and the second piston 133 on the axis move backward.

[0052] Furthermore, even if the motor unit 50 is unable to reverse normally due to a defect in the motor unit 50 or the control board 80, the spring forces of the coil springs in the master cylinder 130 and the return spring 120 cause the shaft member 91 and the first piston 132 and second piston 133 of the master cylinder 130 to retract and return to their original positions before activation. Further, an external sensor is provided to detect the driving state of the vehicle;

[0053] The main points of the present invention will be described below with reference to Fig. 3. Note that the same reference numerals as those shown in Figs. 1 and 2 are used to denote the various elements.

[0054] The graph in Figure 3 shows the correlation between the driving conditions of a vehicle equipped with the electromechanical brake booster of the present invention and the state of the booster, with the vertical axis representing magnitude of the values ​​and the horizontal axis representing time series for the relationship between vehicle speed, brake pedal force, booster assist force (= current supplied to the motor), and fluid pressure.

[0055] The time series consisted of the following five time points: Point a: During driving Point b: When braking begins (when the brake pedal is pressed) Point c: When the vehicle is stopped (vehicle speed is zero) Point d: A predetermined time has passed since the vehicle stopped Time e: A predetermined time has elapsed since time d

[0056] At time a, the vehicle is running and the brake pedal BP is not depressed. In this driving state, the brake booster is not operating.

[0057] At time b, the driver begins to depress the brake pedal BP, the brakes are applied, and the vehicle speed begins to decrease. As the force applied to the brake pedal BP increases, the booster assist force, i.e., the power supplied to the motor unit, increases to amplify the force applied to the brake pedal BP, and the shaft member 91 is moved in a direction that advances the first piston 132 and the second piston 133 of the master cylinder 130 by the drive of the motor unit 50, thereby increasing the fluid pressure and applying the brakes.

[0058] In this specification, controlling the rotational position of the motor unit 50 in accordance with the displacement of the control rod 30 synchronized with depression of the brake pedal BP is referred to as "basic control."

[0059] At time c, the vehicle speed drops to zero due to the brakes being applied. At this time, the booster assist power, i.e., the power supplied to the motor, is detected by the current sensor 70, and reaches a peak value equal to a preset upper limit. The fluid pressure also reaches a peak value.

[0060] In this specification, controlling the current supplied to the motor unit 50 based on the information from the current sensor 70 is referred to as "current control."

[0061] At time d, a predetermined time T1 has elapsed since the engine stopped. At this time, the booster auxiliary power, i.e., the power supplied to the motor and the fluid pressure, are still at their peaks. After time d (until the predetermined time T1 has elapsed since the engine stopped), the upper limit of the power supplied to the motor is gradually reduced, thereby reducing the booster auxiliary power and the fluid pressure.

[0062] At time e, a predetermined time T2 has elapsed since time d. At this time, the upper limit of the motor power supply has been reduced to a predetermined value, preventing excessive motor torque and allowing the vehicle to remain stationary with appropriate motor torque and fluid pressure.

[0063] In addition to the control (basic control) linked to the brake pedal similar to that of conventional electromechanical brake boosters, the present invention suppresses heat generation in the motor unit by simultaneously executing control (current control) that sets an upper limit on the supply current to the motor unit when certain conditions are met and suppresses the workload of the motor unit.

[0064] In the present invention, the upper limit value of the current supplied to the motor section is varied over time, and the upper limit value is gradually lowered, thereby minimizing the discomfort felt by the driver due to the reaction force from the brake pedal.

[0065] To detect that the vehicle is in a stopped state (a state in which the vehicle speed is zero), an external sensor that detects the vehicle's driving state can be used. The external sensor can be, for example, a vehicle speed sensor connected to the vehicle's ECU.

[0066] When the external sensor detects that the vehicle is in a stopped state and when the rod position sensor 40 detects that the brake pedal BP is in a depressed state, the current supplied to the motor unit 50 can be limited.

[0067] In this embodiment, the upper limit of the power supplied to the motor section is reduced in stages, but it may be reduced gradually, or the upper limit may be reduced to a predetermined value all at once. [Explanation of symbols]

[0068] 1 Electromechanical brake booster 10 Casing 11 Cover 12 Bottom plate 20 Input rod 21 Connection hole 30 Control Rod 31 Object to be detected 32 ball studs 33 Plate 34 Step part 35 Coil spring 36 Tip 40 Rod Position Sensor 50 Motor section 51 Stator 52 rotor 53 Rotating member 54 Bearings 55 bearings 56 Detection magnet 57 Motor cover 60 Rotational Position Sensor 70 Current Sensor 80 Control board 90 Rotation-to-linear motion converter 91 Shaft member 100 Bracket 110 Post 120 return spring 130 Master cylinder 131 Cylinder bore 132 First Piston 133 Second Piston 134 Elastic Body BP brake pedal

Claims

1. An electromechanical brake booster mounted on a vehicle, an input rod connected to the brake pedal; a control rod having a cylindrical detection object attached to its outer circumferential surface, which moves linearly in the axial direction in conjunction with operation of the brake pedal in conjunction with the input rod; a rod position sensor that detects the displacement of the control rod by detecting the displacement of the detection object; a motor section that operates in response to the displacement of the control rod; a rotational position sensor for detecting the rotational position and rotational speed of the motor unit; a current sensor for detecting currents of the UVW phases of the motor unit; a control board that drives the motor unit using information obtained from the rod position sensor, the rotation position sensor, and the current sensor, An electromechanical brake booster characterized by simultaneously executing a basic control for controlling the rotational position of the motor unit in accordance with the displacement of the control rod, and a current control for controlling the current supplied to the motor unit based on information from the current sensor.

2. Further, an external sensor is provided to detect the driving state of the vehicle; 2. The electromechanical brake booster according to claim 1, wherein the current supplied to the motor is limited when the external sensor detects that the vehicle is stopped and when the rod position sensor detects that the brake pedal is depressed.

3. 3. The electromechanical brake booster according to claim 2, wherein the upper limit of the current supplied to the motor unit is constant for a predetermined time from the time when the external sensor detects that the vehicle is stopped, and is gradually reduced after the predetermined time has elapsed.

4. The electromechanical brake booster is a rotary-to-linear motion conversion unit disposed on an outer periphery of the control rod, the rotary-to-linear motion conversion unit including a shaft member and a rotating member, and interlocking with the motor unit to convert the rotational motion of the rotating member into linear motion of the shaft member; a bracket that restricts the axial rotation of the shaft member and moves in conjunction with the shaft member in the axial direction; a return spring for biasing the bracket to return to its original position after movement; a master cylinder connected to a tip end of the control rod and the shaft member and operated by linear motion of the control rod or the shaft member, 4. An electromechanical brake booster according to claim 1, 2 or 3.

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