JP4316213B2 - Brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake device capable of accurately determining a contact start position where the contact of a disc rotor and a brake pad is started. <P>SOLUTION: This brake device comprises an actuator for linearly moving a piston 40 along the axial direction of the disc rotor 11, the brake pads 14, 15 pressed by the linear motion of the piston 40 to be brought into contact with the disc rotor 11, a thrust detecting means 46 for detecting the piston thrust received by the piston 40, and a position detecting means 20 for detecting a position of the piston as the displacement of the piston 40. A position obtained by returning the piston 40 to a brake releasing side by a predetermined amount from the position of the piston at the time when the piston thrust becomes less than a predetermined threshold value which is more than 0, is determined as the contact start position of the disc rotor 11 and the brake pads 14, 15. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake device used for braking a vehicle.
[0002]
[Prior art]
As a brake device used for braking a vehicle, there is one that generates a braking force by converting a rotational motion of an electric motor into a linear motion of a piston. In such an electric brake device, for example, a disk rotor, an electric actuator that linearly moves the piston along the axial direction of the disk rotor, a brake pad that is pressed by the linear movement of the piston and contacts the disk rotor, Some have a thrust sensor that detects a piston thrust received by the piston and a position detector that detects a piston position, which is a displacement of the piston.
[0003]
By the way, in the brake device using the electric actuator as described above, in order to prevent the brake pad from being dragged at the time of non-braking or to improve the responsiveness at the time of next braking, etc., the disc rotor and the brake pad It is important to detect the contact start position where the contact starts substantially, and also in the brake device using the hydraulic actuator, when controlling the vehicle posture by controlling the braking force, etc. The detection of the contact start position is important.
And what was disclosed by patent document 1, patent document 2, and patent document 3 is related to the detection of such a contact start position, for example.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-137841
[Patent Document 2]
JP 2000-18294 A
[Patent Document 3]
JP 2001-225741 A
[0005]
[Problems to be solved by the invention]
Patent Document 1 described above describes that the piston position at which the piston thrust detected by the thrust sensor when the brake is released becomes 0 is set as the contact start position. However, especially in the vicinity where the piston thrust becomes zero, the output of the thrust sensor includes a lot of noise, and there is a problem that it is impossible to accurately detect that the piston thrust is zero.
[0006]
Further, Patent Document 2 described above describes that when the brake is released, the piston position when the ratio of the minute change of the piston thrust to the minute change amount of the piston position becomes smaller than a predetermined threshold is set as the contact start position. ing. However, also in this case, if the piston thrust at the time when the ratio of the minute change of the piston thrust to the minute change amount of the piston position becomes smaller than the predetermined threshold is close to 0, the signal contains a lot of noise, and the ratio is rapidly increased. There is a problem that the contact start position cannot be detected accurately.
[0007]
Furthermore, in the above-mentioned Patent Document 3, when the decrease gradient of the piston thrust becomes gentler than the set gradient when the brake is released, the piston position at that time is set to a temporary 0 point, and the non-restoring amount of the brake pad is set. It is described that the position on the reverse side is set to the zero point position by a corresponding amount. However, also in this case, if the piston thrust at the time when the gradient of decrease of the piston thrust becomes gentler than the set gradient, the signal contains a lot of noise, and the contact start position cannot be accurately detected. there were.
[0008]
Therefore, an object of the present invention is to provide a brake device that can accurately determine a contact start position at which a disk rotor and a brake pad start contact.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, a brake device according to claim 1 of the present invention includes a disk rotor, an actuator that linearly moves a piston along an axial direction of the disk rotor, and the disk pressed by the linear motion of the piston. A brake pad in contact with the rotor; thrust detection means for detecting piston thrust received by the piston; and position detection means for detecting a piston position, which is displacement of the piston, based on an operation amount of the brake pedal In a brake device that drives an actuator to generate thrust in the piston,DeContact start position setting means for setting a contact start position at which the disk rotor and the brake pad start contactThe contact start position setting means has a change in the piston position.A predetermined amount is set as a variable value based on a change in the amount of change in the piston thrust with respect to the amount, and when the brake is released based on the operation amount of the brake pedal, the piston thrust is a predetermined value greater than zero.The position where the piston is returned to the brake release side by the predetermined amount from the piston position at the time when the pressure becomes equal to or lower than the threshold is set as the contact start position.It is characterized by that.
[0010]
  Thus, the contact start position setting meansA predetermined amount is set as a variable value based on a change in the amount of change in the piston thrust with respect to the amount of change in the piston position,When releasing the brake based on the operation amount of the brake pedal, avoiding the point where the piston thrust, which is greatly influenced by noise in the thrust detection means, becomes zero, and the predetermined amount from the piston position at the time when the threshold value falls below a predetermined threshold value greater than zero. The position where the piston is returned to the brake release side is set as a contact start position where the disc rotor and the brake pad start contact.
[0011]
  The brake device according to claim 2 of the present invention relates to the brake device according to claim 1,The contact start position setting means includesA calculation unit that calculates a change rate of the change amount of the piston thrust with respect to the change amount of the piston position;TheCalculation unitByCalculated rate of changeFrom the above, the wear state of the brake pad is detected and variable according to the wear state.Predetermined amountChangeIt is characterized by setting.
[0012]
Thus, when the brake is released, the point where the piston thrust, which is greatly influenced by noise in the thrust detection means, becomes 0 is avoided, and the brake pad wear state is changed from the piston position when it becomes less than a predetermined threshold value greater than 0. The corresponding position where the piston is returned to the brake release side by a predetermined amount corresponding to the change rate of the change amount of the piston thrust with respect to the change amount of the piston position is set as the contact start position.
[0013]
  The brake device according to claim 3 of the present invention relates to the brake device according to claim 1,The contact start position setting means, based on the change rate calculated by the calculation unit, if the change rate is larger than an intermediate value when the brake pad is new, a small predetermined amount, and the change rate is the brake If it is smaller than the intermediate value when the pad is new, a large predetermined amount is set as the predetermined amount.It is characterized by that.
[0015]
  The brake device according to claim 4 of the present invention is a disk rotor, an actuator that linearly moves the piston along the axial direction of the disk rotor, and a brake pad that is pressed by the linear movement of the piston and contacts the disk rotor. And a thrust detection means for detecting a piston thrust received by the piston, and a position detection means for detecting a piston position which is a displacement of the piston.And driving the actuator based on the amount of operation of the brake pedal to generate thrust on the piston.AndWhen releasing the brake based on the operation amount of the brake pedal, a position where the piston is returned to the brake release side by a predetermined amount from the piston position when the piston thrust is below a predetermined threshold value greater than 0.Temporary contact position between the disc rotor and the brake padAsBased on the detected temporary contact position detection means and the piston position detected by the position detection means, the piston speed until the provisional contact position is set is calculated, and the reliability of the temporary contact position is calculated based on the piston speed. Provisional contact position reliability calculation means, and contact position detection means for correcting the provisional contact position based on the reliability and storing it as a contact position.
[0016]
  In this way, the provisional contact position detection means avoids a point where the piston thrust, which is greatly influenced by noise in the thrust detection means, is zero when the brake is released based on the amount of operation of the brake pedal, and falls below a predetermined threshold value greater than zero. The position at which the piston is returned to the brake release side by a predetermined amount from the piston position at that time is set as a temporary contact start position where the disk rotor and the brake pad start to contact each other.
  Also,The provisional contact position detecting means detects the provisional contact position between the disc rotor and the brake pad based on the piston thrust, while the provisional contact position reliability calculation means is provisionally based on the piston position detected by the position detection means. When the piston speed until the contact position is set is calculated and the reliability of the temporary contact position is calculated based on the piston speed, the contact position detecting means corrects the temporary contact position based on the reliability and stores it as the contact position. To do. Thereby, for example, when the piston speed is steep, the number of sampling data is small, and the reliability is low, the contact position detection means can determine the contact position by reducing the weight of the temporary contact position detected by the temporary contact position detection means. .
[0017]
The brake device according to claim 5 of the present invention relates to the brake device according to claim 4, from the point in time when the contact position is stored by the contact position detection means before the provisional contact position detection means is detected by the provisional contact position detection means. It has a previous contact position reliability calculation means for calculating the reliability of the previous contact position based on the elapsed time, and the contact position detection means has the reliability of the previous contact position and the reliability of the temporary contact position reliability calculation means. The temporary contact position is corrected based on the degree and stored as a contact position.
[0018]
As a result, the reliability of the previous contact position is calculated based on the elapsed time from when the previous contact position reliability calculation means stores the contact position by the contact position detection means before the temporary contact position detection means detects the temporary contact position. When the degree is calculated, the contact position detection unit corrects the temporary contact position based on the reliability of the previous contact position and the reliability of the temporary contact position reliability calculation unit, and stores the corrected position as the contact position. As a result, for example, the elapsed time from the time when the contact position is memorized by the contact position detecting means before the provisional contact position is detected by the provisional contact position detecting means is long, and wear, thermal expansion, heat shrinkage, etc. occur in the brake pad. When the reliability of the previous contact position is low, the contact position detection unit can determine the contact position by increasing the weight of the current temporary contact position detected by the temporary contact position detection unit.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A brake device according to a first embodiment of the present invention will be described below with reference to FIGS.
[0020]
As shown in FIG. 1, the brake device of the first embodiment is an electric disc brake device having an electric caliper 10.
[0021]
The electric caliper 10 has a caliper body 12 disposed on one side in the axial direction of a disk rotor 11 that rotates with a wheel (not shown). The caliper body 12 is formed in a substantially C shape and straddles the disk rotor 11. The claw portion 13 extending to the opposite side is integrally coupled. Brake pads 14 and 15 are provided on both sides of the disk rotor 11 in the axial direction. The brake pads 14 and 15 are supported by a carrier 16 fixed on the vehicle body side so as to be movable along the axial direction of the disc rotor 11, and transmit braking torque to the carrier 16. 12 is guided so as to be slidable along the axial direction of the disk rotor 11 by a slide pin (not shown) attached to the carrier 16.
[0022]
A caliper case 18 is coupled to the caliper body 12, and an electric motor (actuator) 19 and a position detector (position detection means) 20 are provided in the case 18. On the other hand, a ball ramp mechanism 21 and a speed reduction mechanism 22 are provided inside the caliper body 12. A cover 23 is attached to the rear end of the case 18.
[0023]
The electric motor 19 includes a stator 25 fixed to the inner periphery of the case 18, and a rotor 28 inserted into the stator 25 and rotatably supported by the case 18 by bearings 26 and 27. The position detector 20 includes a resolver stator 29 fixed to the case 18 side and a resolver rotor 30 attached to the rotor 28. Based on these relative rotations, the rotational position of the rotor 28, that is, the motor rotational position of the electric motor 19 is determined. It is to detect.
[0024]
The ball ramp mechanism 21 includes an annular first disk 32 and second disk 33, and a plurality of balls (steel balls) 34 interposed therebetween. The first disk 32 is rotatably supported by the caliper body 12 by a bearing 35, and a cylindrical portion 36 that is inserted into the rotor 28 is integrally formed. A cylindrical sleeve 37 having a smaller diameter than the cylindrical portion 36 is integrally formed on the second disk 33, and the sleeve 37 is inserted into the cylindrical portion 36.
[0025]
For example, three ball grooves 38 and 39 each having an arc shape extending along the circumferential direction are formed on the opposing surfaces of the first disk 32 and the second disk 33 of the ball ramp mechanism 21. These ball grooves 38 and 39 are extended in the range of an equal central angle (for example, 90 °) and inclined in the same direction. Then, a ball 34 is inserted between the ball grooves 38 and 39 formed in the first disk 32 and the second disk 33, and the ball grooves 38 and 39 are moved by the relative rotation of the first disk 32 and the second disk 33. As the ball 34 rolls, the first disk 32 and the second disk 33 are relatively displaced in the axial direction. At this time, when the first disk 32 rotates counterclockwise with respect to the second disk 33, they are displaced in the direction of separating.
[0026]
A piston 40 is provided between the second disk 33 and the brake pad 14. The piston 40 has a cylindrical member 42a in which a screw portion 41 is formed on the outer periphery. The cylindrical member 42a is inserted into the sleeve 37 of the second disk 33 and is screwed into a screw portion 43 formed on the inner periphery thereof. The cylindrical member 42a is fitted with a two-side chamfered portion (not shown) of a shaft 45 attached to the case 18 via a bracket 44, and its rotation is restricted. Further, the piston 40 has a substantially disk-shaped pressing member 42b that is connected to the shaft 45 of the cylindrical member 42a in a state in which the rotation is restricted on the opposite side. And between the cylindrical member 42a and the press member 42b, the thrust sensor (thrust detection means) 46 which detects the piston thrust which the piston 40 receives is provided.
[0027]
The screw portion 41 of the cylindrical member 42 of the piston 40 and the screw portion 43 of the sleeve 37 of the second disk 33 form an irreversible screw, and the piston 40 moves even if a force acts in the axial direction. However, the second disk 33 is moved counterclockwise to move toward the disk rotor 11 side.
[0028]
An elastic member 49 is interposed between spring receivers 47 and 48 formed on the outer peripheral portion of the shaft 45 and the inner peripheral portion of the sleeve 37 of the second disc 33, respectively, and the second disc 33 causes the ball 34 to be It is urged to be sandwiched between one disk 32. The shaft 45 is attached to the bracket 44 by an adjustment screw 50 and a lock nut 51.
[0029]
A controller (control means) 100 is connected to the electric motor 19, the position detector 20, and the thrust sensor 46, and a pedal sensor 102 that detects an operation amount of the brake pedal 101 is connected to the controller 100. The controller 100 detects the detection result of the pedal sensor 102, that is, the operation amount of the brake pedal 101, the detection result of the position detector 20, that is, the actual piston position corresponding to the rotational position of the electric motor 19, the current value of the electric motor 19, By controlling the electric motor 19 based on the detection result of the thrust sensor 46, that is, the actual piston thrust, control is performed so that the piston thrust becomes the target thrust.
[0030]
A cylindrical spring holder 67 is attached to the outer periphery of the tip of the sleeve 37 of the second disk 33. One end portion of the spring holder 67 engages with the tip end portion of the cylindrical portion 36 of the first disk 32 to limit the relative rotation thereof to a certain range. A coil spring 69 is wound around the spring holder 67, and the coil spring 69 is twisted with a predetermined set load, one end of which is coupled to the spring holder 67, and the other end of the first disk 32. It is coupled to the cylindrical portion 36 (the coupling portion is not shown).
[0031]
Next, the basic operation of the electric caliper 10 of the electric disc brake according to the first embodiment configured as described above will be described.
[0032]
In the non-braking state, the ball 34 of the ball ramp mechanism 21 is at the deepest end of the ball grooves 38 and 39, and the first disk 32 and the second disk 33 are closest. When generating the braking force, the controller 100 rotates the rotor 28 of the electric motor 19 clockwise. Then, the rotational torque of the roller 28 is amplified by the speed reduction mechanism 22 and transmitted to the first disk 32.
[0033]
The rotational force of the first disk 32 is transmitted to the second disk 33 via the coil spring 69. Before the piston 40 presses the brake pads 14 and 15, almost no axial load acts on the piston 40, and the resistance generated in the screw portions 41 and 43 between the piston 40 and the second disk 33 is small. The set load of the coil spring 69 causes the second disk 33 to rotate integrally with the first disk 32, causing relative rotation between the second disk 33 and the piston 40, and the piston 40 is moved by the action of the screw portions 41 and 43. It advances to the disk rotor 11 side. Thereby, the screw portions 41 and 43 constitute a conversion mechanism portion that converts the rotational motion of the electric motor 19 into the linear motion of the piston 40.
[0034]
Then, the piston 40 comes into contact with one brake pad 14 and presses it against the disk rotor 11, and the caliper body 12 moves along the slide pin of the carrier 16 by the reaction force, so that the claw portion 13 moves to the other brake. The pad 15 is pressed against the disk rotor 11.
[0035]
After the brake pads 14 and 15 are pressed against the disk rotor 11, a large axial load acts on the piston 40 due to the reaction force, so that the resistance of the screw portions 41 and 43 increases and the coil spring 69 is set. When the load exceeds the load, the rotation of the second disk 33 is stopped. As a result, the coil spring 69 is bent and relative rotation occurs between the first disk 32 and the second disk 33 of the ball ramp mechanism 21. As a result, the ball 34 rolls in the ball grooves 38 and 39 to advance the second disk 33 and the piston 40 together (that is, linear movement), and the piston 40 further pushes the brake pads 14 and 15 against the disk rotor 11. wear. As a result, the ball ramp mechanism 21 also constitutes a conversion mechanism that converts the rotational motion of the electric motor 19 into the linear motion of the piston 40.
[0036]
Next, the control contents of the controller 100 will be described with reference to the flowchart of FIG. The control shown in this flowchart is a process executed at regular control cycles.
[0037]
First, the controller 100 reads a pedal sensor signal output from the pedal sensor 102 (STEP 00). Then, based on the pedal operation amount that is the operation amount of the brake pedal 101 indicated by the read pedal sensor signal, the braking force of the electric caliper 10, that is, the target thrust generated in the piston 40 is obtained (STEP01).
[0038]
It is determined whether or not the target thrust calculated in STEP01 is greater than zero (STEP02). If the target thrust is greater than zero, a thrust sensor signal indicating the thrust of the piston 40 is read from the thrust sensor 46 (STEP03). Piston thrust control is performed on the electric motor 19 so that the piston thrust detected by the thrust sensor 46 is fed back so as to be generated in the piston (STEP 04).
[0039]
In STEP 05, it is determined whether or not the piston thrust falls below a preset reference threshold value. When the piston thrust falls below the reference threshold value, the piston position is read (STEP 06), and the position returned by a predetermined amount α from the piston position is determined by the disk rotor. 11 and the brake pads 14 and 15 are set and stored as contact start positions at which contact is substantially started (STEP 07). In STEP 05, if the piston thrust is not below the reference threshold value, the process is terminated.
[0041]
In STEP02, when the target thrust is zero, the piston position is read (STEP08), and the piston 40 is controlled to the contact start position where the disk rotor 11 and the brake pads 14, 15 substantially start to contact (STEP09). .
[0042]
  here, FIG.As shown in FIG. 4, the piston thrust is the reference threshold value Fth described above when the brake pads 14 and 15 are in a high rigidity state with a large amount of wear due to normal wear, a new nominal state, and a low rigidity state with partial wear. After that, the retracting amount for the piston 40 to retract to the contact start position is different from A1, A2 and A3 (A1 <A2 <A3). Therefore, the predetermined value α is set to a variable value according to the wear state of the brake pads 14 and 15.Do.
[0043]
Here, the wear state of the brake pads 14 and 15 is the rate of change of the change amount of the piston thrust detected by the thrust sensor 46 with respect to the change amount of the piston position detected by the position detector 20 in the calculation unit of the controller 100. Detect from. That is, as shown in FIG. 4, the piston position signal output from the position detector 20 when the piston thrust indicated by the piston thrust sensor signal output from the thrust sensor 46 becomes a preset piston thrust Fa is indicated. The piston position Pa and the piston position Pb indicated by the piston position signal output from the position detector 20 when the piston thrust indicated by the piston thrust sensor signal output from the thrust sensor 46 becomes a preset piston thrust Fb. Is detected. Then, the change rate dF / dP of the piston thrust change amount dF (= Fa-Fb) detected by the thrust sensor 46 with respect to the piston position change amount dP (= Pa−Pb) detected by the position detector 20, Calculation is performed according to dF / dP = (Fa−Fb) / (Pa−Pb).
[0044]
If the rate of change dF / dP is large, it is in a highly rigid state, if the rate of change dF / dP is an intermediate value, it is in a nominal state, and if the rate of change dF / dP is small, it is in a low rigid state. A control table as shown in FIG. 5 is experimentally obtained in advance, and α corresponding to the change rate dF / dP is set. If the rate of change dF / dP is large, it is in the high rigidity state, so a small A1 is set as a predetermined value α, and if the rate of change dF / dP is an intermediate value, it is in a nominal state, so an intermediate A2 is set as the predetermined value α. If the change rate dF / dP is small, the rigidity is low, so a large A3 is set as the predetermined value α.
[0045]
When the brake pedal 101 is lightly depressed and does not reach the predetermined piston thrusts Fa and Fb, the rate of change dF / dP calculated last time is used. Further, if the timing for calculating the rate of change dF / dP is when the brake is released, the processing can be performed based on the latest pad state. Furthermore, if the piston thrusts Fa and Fb are set to the low thrust side, even when the brake pedal 101 is lightly depressed, the probability that the piston thrust reaches the detected thrusts Fa and Fb increases, and the update rate dF / dP is updated. Can be high.
The predetermined value α may be fixed and the reference threshold value may be variable according to the change rate dF / dP.
[0046]
Then, until the contact start position set and stored in STEP06, the piston position detected by the position detector 20 is used as feedback, and the piston 40 is retracted and stopped by position control with little influence of noise (STEP07).
[0047]
According to the brake device of the first embodiment described above, when the brake is released, the point at which the piston thrust, which is greatly influenced by noise in the thrust sensor 46, becomes 0 is avoided, and the time when the threshold becomes below a predetermined reference threshold value greater than 0. The predetermined amount corresponding to the change rate dF / dP of the change amount dF of the piston thrust relative to the change amount dP of the piston position corresponding to the wear state of the brake pads 14 and 15 from the piston position detected by the position detector 20 in FIG. The position where the piston is returned to the brake release side by α is set as a contact start position where the disk rotor 11 and the brake pads 14 and 15 start to contact each other. Therefore, the influence of noise can be avoided and the contact start position is set in consideration of the wear state of the brake pads 14 and 15, so that the contact start position can be accurately obtained. As a result, it is possible to reliably prevent dragging of the brake pads 14 and 15 at the time of non-braking, and to improve the responsiveness at the time of next braking.
[0048]
In the above description, the case where an electric motor is used as the actuator has been described as an example. For example, the wear state of the brake pad can be detected from the change rate dF / dP of the change amount of the piston thrust with respect to the change amount of the piston position, and this can be used for posture control of a vehicle having a brake device using a hydraulic actuator. is there.
[0049]
A brake device according to a second embodiment of the present invention will be described below with reference to FIGS. 6 to 13 focusing on differences from the first embodiment.
[0050]
As shown in FIG. 6, the brake device of the second embodiment is also an electric disk brake device having an electric caliper 10 as in the first embodiment, and a vehicle body behavior sensor 103 for detecting the behavior of the vehicle body is provided in the controller 100. The controller 100 controls the electric caliper 10 based on signals from the pedal sensor 102 and the vehicle body behavior sensor 103. Note that an acceleration sensor, a yaw rate sensor, a wheel speed sensor, a steering sensor, or the like is used as the vehicle body behavior sensor 103.
[0051]
Next, the control contents of the controller 100 of the second embodiment will be described with reference to the flowchart of FIG. The control shown in this flowchart is a process executed at regular control cycles.
[0052]
First, the controller 100 reads the pedal sensor signal output from the pedal sensor 102 (STEPa0) and also reads the vehicle body behavior sensor signal output from the vehicle body behavior sensor 103 (STEPa1). Then, the braking force of the electric caliper 10, that is, the piston 40 is generated based on the pedal operation amount that is the operation amount of the brake pedal 101 indicated by the read pedal sensor signal and the behavior amount that is the behavior amount of the vehicle body indicated by the vehicle body behavior sensor signal. The target thrust to be obtained is determined (STEPa2).
[0053]
It is determined whether or not the target thrust calculated in STEPa2 is larger than zero (STEPa3). If the target thrust is larger than zero, a thrust sensor signal indicating the thrust of the piston 40 is read from the thrust sensor 46 (STEPa4), and the target thrust is calculated. Piston thrust control is performed on the electric motor 19 so as to be generated in the piston 40, using the piston thrust detected by the thrust sensor 46 as feedback (STEP 5).
[0054]
Then, the controller 100 performs provisional contact position detection processing (details will be described later) for detecting the provisional contact position between the disc rotor 11 and the brake pads 14 and 15 based on the piston thrust in the provisional contact position detection means (STEPa6). ).
[0055]
Subsequently, the controller 100 uses the provisional contact position reliability calculation means to determine the piston until the provisional contact position is set based on the piston position signal output from the position detector 20, that is, the piston position which is the position of the piston 40. The piston speed, which is 40, is calculated, and the reliability of the temporary contact position is calculated based on the piston speed, and the contact position detecting means corrects the temporary contact position detected in STEPa6 based on the reliability and makes contact. A contact position determination process (details will be described later) stored as a position is performed (STEPa7).
[0056]
Here, in the contact position determination process of STEPa7, the controller 100 stores the contact position by the contact position detection unit before the temporary contact position detection unit detects the temporary contact position by the temporary contact position detection unit. The reliability of the previous contact position is calculated based on the elapsed time from the time point, and the contact position detecting means is based on the reliability of the previous contact position and the reliability of the temporary contact position reliability calculating means. The temporary contact position is corrected and stored as the contact position (details will be described later).
[0057]
In STEPa3, if the target thrust is not greater than zero, in other words, zero, the controller 100 reads the piston position signal output from the position detector 20, that is, the piston position (STEPa8), and is stored at that time. Position control using the piston position as feedback is performed on the electric motor 19 so that the piston position coincides with the contact position (STEPa9). Thereby, piston 40 is located in a contact position.
[0058]
Next, the temporary contact position detection process of STEPa6 described above will be described with reference to the flowchart shown in FIG.
[0059]
First, the temporary contact position correction flag is reset (STEPb0). Next, it is determined whether or not the piston thrust F detected by the thrust sensor 46 is greater than zero (STEPb1). If the piston thrust F is greater than zero, the previous piston thrust F ′ is a preset reference threshold value. It is determined whether it is smaller than Fth and whether the current piston thrust F is equal to or greater than the reference threshold Fth (STEPb2).
[0060]
When it is determined in STEPb2 that the previous piston thrust F ′ is smaller than a preset reference threshold Fth and the current piston thrust F is greater than or equal to the reference threshold Fth, the position detector 20 The output piston position signal, that is, the current piston position is read (STEPb4), the position returned from the current piston position by a predetermined value α is set as the temporary contact position Q (STEPb5), and the correction flag is set (STEPb6). . Finally, the current piston thrust F is stored as F '(STEPb7), and the process is terminated.
[0061]
On the other hand, if it is not determined in STEPb2 that the previous piston thrust F ′ is smaller than a preset reference threshold Fth and the current piston thrust F is greater than or equal to the reference threshold Fth, in STEPb3 Then, it is determined whether or not the previous piston thrust F ′ is larger than a preset reference threshold Fth and the current piston thrust F is equal to or less than the reference threshold Fth. When the previous piston thrust F ′ is larger than the preset reference threshold Fth and the current piston thrust F is equal to or less than the reference threshold Fth, the position is determined by STEP b4, b5, b6, b7. The piston position signal output from the detector 20, that is, the current piston position is read, the position returned from the current piston position by a predetermined value α is set as the temporary contact position Q, the correction flag is set, and finally this time The piston thrust F is stored as F ′, and the process is terminated.
[0062]
Since the relationship between the piston position and the piston thrust is obtained experimentally in advance as shown in FIG. 9, the piston thrust is returned to the contact position from the time when the piston thrust reaches the preset reference threshold Fth. The predetermined value α required for the above is obtained from this relationship. That is, the relationship between the reference threshold value Fth and the predetermined value α is experimentally obtained in advance. By using this relationship, as in the first embodiment, the thrust sensor 46 avoids a point where the piston thrust, which is greatly influenced by noise, becomes zero.
[0063]
Further, in STEPb1, when the piston thrust F detected by the thrust sensor 46 is not larger than zero, that is, when the piston thrust F is zero, and in STEPb3, the previous piston thrust F ′ is larger than a preset reference threshold Fth. In the case where it is not determined that the piston thrust F is large and the current piston thrust F is equal to or less than the reference threshold Fth, the current piston thrust F is finally set in step Sb7 without setting the temporary contact position. Is stored as F ′ and the process is terminated.
[0064]
Next, the contact position determination process of STEPa7 described above will be described with reference to the flowchart shown in FIG.
[0065]
First, it is determined whether or not a correction flag for setting and resetting is set in the provisional contact position detection process executed in advance (STEPc0). If the correction flag is not set in STEPc0, the elapsed time T is accumulated in a timer (not shown) (STEPc1), and the contact position determination process is terminated. The elapsed time is the elapsed time from the time when the previous correction flag was set to the present.
[0066]
On the other hand, if the correction flag is set in STEPc0, the previous value reliability Y for the elapsed time is calculated according to the calculation table (STEPc2). The previous value (previous contact position) is likely to change in the state of the brake pads 14 and 15 over time, such as expansion or contraction, and as a result, varies with respect to the recognized contact position. Since there is a high probability, the previous value reliability Y is low. Therefore, for example, as shown in FIG. 11, the calculation table is set so that the previous value reliability Y decreases as the elapsed time T increases.
[0067]
Subsequently, the elapsed time T is reset (STEPc3), and the product of the previous value reliability Y for the time elapsed calculated in STEPc2 and the correction reliability X ′ of the previous value is calculated to obtain the previous value (previous contact position). The overall reliability Z is obtained. Note that the amount of work during braking may be added to the calculation of the overall reliability Z of the previous value. For example, if the brake is being operated, the work amount is estimated from the time integral value Sf of the piston thrust and the output of the wheel speed sensor, the acceleration sensor, etc. For example, the time integral value Sf of the piston thrust is large and the vehicle is decelerated. If it is determined (determined from a wheel speed sensor or an acceleration sensor), the state of the brake pads 14 and 15 may be changed, so that the previous value reliability Y is lowered.
[0068]
Next, time differentiation of the piston displacement is performed based on the piston position signal output from the position detector 20, that is, the piston position, and the moving speed Vp of the piston 40 is calculated (STEPc5). Then, the current value reliability X is calculated from the moving speed Vp of the piston (STEPc6). For example, as shown in FIG. 12, the calculation method is set such that the current value reliability X decreases as the return speed Vp of the piston 40 increases by a predetermined value or more. This is because if the return speed Vp of the piston 40 is large, the number of sample points of the signal of the thrust sensor 46 in the controller 100 decreases, and the probability that an error occurs in the corrected contact position increases.
[0069]
The provisional contact position Q and the previous value P (n−1) detected this time are weighted by the following equation from the previous value reliability X and the previous total reliability Z based on the previous value reliability Y. The contact position P (n) is calculated (STEPc7).
P (n) = Q · X / (X + Z) + P (n−1) · Z / (X + Z)
[0070]
In STEPc7, the current temporary contact position Q is prioritized and, for example, the following position is calculated so that the contact position P is corrected only when the current value reliability X is smaller than the correction reliability X ′ of the previous value. You may do it.
When the current value reliability X is equal to or higher than the correction reliability X ′ of the previous value (X ≧ X ′).
P = P (n)
When the correction reliability X ′ of the previous value is higher than the current value reliability X (X <X ′)
P = P (n) + (P (n) -P (n-1)). (X-X ')
[0071]
Then, the current value reliability X is stored as the correction reliability X '(STEP c8), and the current contact position P (n) is set and stored as the contact position P (n-1) (STEP c9). The correction reliability X ′ and the contact position P (n−1) are used until the next change.
[0072]
Here, FIG. 13 illustrates a case where the provisional contact position is calculated at the braking end time t2 and the contact position is corrected in consideration of the previous value (previous contact position) corrected at the braking start time t1. The timing chart figure of an example is shown.
It is assumed that the piston thrust falls below the threshold value (Fth) at time t2 (STEPb3) and the temporary contact position Q is obtained (STEPb5). Further, it is assumed that the reliability at this time is X. Furthermore, it is assumed that the previous value P (n−1) has been corrected with the reliability X ′ at time t1. At this time, the reliability Y over time of the previous value P (n−1) is obtained by t2−t1, and the total reliability is Z = X ′ · Y. Therefore, the contact position P (n) can be obtained by using the following equation. FIG. 13 shows an outline of correction when the current value reliability X is low.
P (n) = Q · X / (X + Z) + P (n−1) · Z / (X + Z)
[0073]
According to the brake device of the second embodiment described above, in the controller 100, the temporary contact position detection means detects the temporary contact position Q between the disc rotor 11 and the brake pads 14, 15 based on the piston thrust. Thus, the temporary contact position reliability calculation means calculates the piston speed Vp until the temporary contact position Q is set based on the piston position detected by the position detector 20, and the temporary contact position reliability is calculated based on the piston speed Vp. When X is calculated, the contact position detecting means corrects the temporary contact position Q based on the reliability X and stores it as the contact position P (n). Thereby, for example, when the piston speed Vp is steep, the number of sampling data is small, and the reliability is low, the contact position detection means determines the contact position by reducing the weight of the temporary contact position Q detected by the temporary contact position detection means. Can do. Therefore, the contact position where the disk rotor 11 and the brake pads 14 and 15 start to contact each other can be accurately obtained. Therefore, drag of the brake pads 14 and 15 during non-braking can be prevented, and responsiveness during the next braking can be improved.
[0074]
Further, the controller 100 is based on the elapsed time T from the time when the previous contact position reliability calculation means stores the contact position by the contact position detection means before the temporary contact position Q is detected by the temporary contact position detection means. When the reliability Y of the previous contact position is calculated, the contact position detecting means determines the temporary contact position Q based on the total reliability Z based on the reliability Y of the previous contact position and the reliability X based on the temporary contact position reliability calculation means. Is corrected and stored as a contact position. Thus, for example, the elapsed time T from when the contact position is stored by the contact position detection means before the temporary contact position is detected by the temporary contact position detection means is long, and wear, thermal expansion, heat When there is a high possibility that contraction or the like has occurred and the reliability Y of the previous contact position is low, the contact position detection means increases the weight of the current temporary contact position Q detected by the temporary contact position detection means to increase the contact position. Can be decided. Therefore, the contact position where the disk rotor 11 and the brake pads 14 and 15 start to contact each other can be accurately obtained. Therefore, drag of the brake pads 14 and 15 at the time of non-braking can be surely prevented, and responsiveness at the time of next braking can be reliably improved.
[0075]
【The invention's effect】
  As described above in detail, according to the brake device of claim 1 of the present invention, the contact start position setting means isWhile setting a predetermined amount as a variable value based on the change of the change amount of the piston thrust with respect to the change amount of the piston position,When releasing the brake based on the operation amount of the brake pedal, avoiding the point where the piston thrust, which is greatly influenced by noise in the thrust detection means, becomes zero, and the predetermined amount from the piston position at the time when the threshold value falls below a predetermined threshold value greater than zero. The position where the piston is returned to the brake release side is set as a contact start position where the disc rotor and the brake pad start contact. Therefore, the influence of noise can be avoided,In addition, the change of the piston thrust change with respect to the piston position change is taken into account.Therefore, the contact start position can be accurately obtained. Therefore, it is possible to prevent the brake pad from being dragged during non-braking, and to improve the responsiveness during the next braking.
[0076]
According to the brake device of claim 2 of the present invention, at the time of releasing the brake, a point where the piston thrust, which has a large influence of noise in the thrust detecting means, becomes 0 is avoided, and when the threshold becomes less than a predetermined threshold value greater than 0. A position where the piston is returned to the brake release side by a predetermined amount corresponding to the change rate of the change amount of the piston thrust with respect to the change amount of the piston position, corresponding to the wear state of the brake pad, is set as the contact start position. Therefore, since the contact start position is set in consideration of the wear state of the brake pad, the contact start position can be obtained more accurately. Therefore, it is possible to reliably prevent the brake pad from being dragged at the time of non-braking and to improve the responsiveness at the time of the next braking.
[0078]
  According to the brake device of claim 4 of the present invention,When releasing the brake based on the operation amount of the brake pedal, avoid the point where the piston thrust, which has a large noise effect in the thrust detecting means, becomes zero, and start from the piston position when the threshold value is below a predetermined threshold value greater than zero, Is set to a temporary contact start position at which the disk rotor and the brake pad start to contact each other. Therefore, since the influence of noise can be avoided, the provisional contact start position can be accurately obtained.
  Also,The provisional contact position detecting means detects the provisional contact position between the disc rotor and the brake pad based on the piston thrust, while the provisional contact position reliability calculation means is provisionally based on the piston position detected by the position detection means. When the piston speed until the contact position is set is calculated and the reliability of the temporary contact position is calculated based on the piston speed, the contact position detecting means corrects the temporary contact position based on the reliability and stores it as the contact position. To do. Thereby, for example, when the piston speed is steep, the number of sampling data is small, and the reliability is low, the contact position detection means can determine the contact position by reducing the weight of the temporary contact position detected by the temporary contact position detection means. . Therefore, the contact start position where the disk rotor and the brake pad start contact can be accurately obtained. Therefore, it is possible to prevent the brake pad from being dragged during non-braking, and to improve the responsiveness during the next braking.
[0079]
According to the brake device of claim 5 of the present invention, from the time when the previous contact position reliability calculation means stores the contact position by the contact position detection means before the provisional contact position detection means detects the provisional contact position. When the reliability of the previous contact position is calculated based on the elapsed time, the contact position detection unit corrects the temporary contact position based on the reliability of the previous contact position and the reliability of the temporary contact position reliability calculation unit. And memorize it as the contact position. As a result, for example, the elapsed time from the time when the contact position is memorized by the contact position detecting means before the provisional contact position is detected by the provisional contact position detecting means is long, and wear, thermal expansion, heat shrinkage, etc. occur in the brake pad. When the reliability of the previous contact position is low, the contact position detection unit can determine the contact position by increasing the weight of the current temporary contact position detected by the temporary contact position detection unit. Therefore, the contact start position where the disk rotor and the brake pad start contact can be accurately obtained. Therefore, it is possible to reliably prevent the brake pad from being dragged at the time of non-braking and to improve the responsiveness at the time of the next braking.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an electric caliper showing a brake device according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the control contents of the controller of the brake device according to the first embodiment of the present invention.
FIG. 3 is a characteristic diagram showing a state of piston thrust with respect to a piston position in each of a high rigidity state, a nominal state, and a low rigidity state of a brake pad.
FIG. 4 is a characteristic diagram showing a state of piston thrust with respect to a piston position.
FIG. 5 is a diagram showing a control table for calculating a predetermined value α from a change rate dF / dP in the controller of the brake device according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view of an electric caliper showing a brake device according to a second embodiment of the present invention.
FIG. 7 is a main flowchart showing the control contents of a controller of a brake device according to a second embodiment of the present invention.
FIG. 8 is a flowchart showing the control content of provisional contact position detection processing of the controller of the brake device according to the second embodiment of the present invention.
FIG. 9 is a characteristic diagram showing the relationship of piston thrust to piston position.
FIG. 10 is a flowchart showing the control content of a contact position determination process of a controller of a brake device according to a second embodiment of the present invention.
FIG. 11 is a diagram showing a calculation table of previous value reliability Y with respect to time lapse T;
FIG. 12 is a diagram showing a calculation table of current value reliability X with respect to piston return speed Vp.
FIG. 13 is an example timing chart for explaining a case where the contact position is corrected under the control of the controller of the brake device according to the second embodiment of the present invention.
[Explanation of symbols]
10 Electric caliper
11 Disc rotor
14,15 Brake pads
19 Electric motor (actuator)
20 position detector (position detecting means)
40 piston
46 Thrust sensor (thrust detection means)
100 controller (provisional contact position detection means, provisional contact position reliability calculation means, contact position detection means, previous contact position reliability calculation means)

Claims (5)

A disk rotor,
An actuator for linearly moving the piston along the axial direction of the disk rotor;
A brake pad that is pressed by a linear motion of the piston and contacts the disk rotor;
Thrust detecting means for detecting piston thrust received by the piston;
Position detecting means for detecting a piston position which is a displacement of the piston,
In a brake device that drives the actuator based on an operation amount of a brake pedal to generate a thrust in the piston,
Have a contact start position setting means for pre Kide Isukurota and said brake pad to set the contact start position to start the contact,
The contact start position setting means sets a predetermined amount as a variable value based on a change in the change amount of the piston thrust with respect to a change amount in the piston position, and when the brake is released based on the operation amount of the brake pedal, the piston thrust is A brake device , wherein a position where the predetermined amount of the piston is returned to the brake release side from the piston position when the threshold value becomes equal to or less than a predetermined threshold value greater than 0 is set as a contact start position .   The contact start position setting means has a calculation unit that calculates a change rate of the change amount of the piston thrust with respect to the change amount of the piston position, and the wear state of the brake pad from the change rate calculated by the calculation unit The brake device according to claim 1, wherein the predetermined amount is variably set in accordance with the wear state. The contact start position setting means, based on the change rate calculated by the calculation unit, sets a small predetermined amount if the change rate is larger than an intermediate value when the brake pad is new, and the change rate is the brake rate. The brake device according to claim 2 , wherein a predetermined amount larger than the intermediate value when the pad is new is set as the predetermined amount. A disk rotor,
An actuator for linearly moving the piston along the axial direction of the disk rotor;
A brake pad that is pressed by a linear motion of the piston and contacts the disk rotor;
Thrust detecting means for detecting piston thrust received by the piston;
Position detecting means for detecting a piston position which is a displacement of the piston,
In a brake device that drives the actuator based on an operation amount of a brake pedal to generate a thrust in the piston,
When the brake is released based on the operation amount of the brake pedal, a position where the piston is returned to the brake release side by a predetermined amount from the piston position when the piston thrust becomes a predetermined threshold value greater than 0 is defined as the disc rotor. Provisional contact position detection means for detecting the provisional contact position with the brake pad;
A provisional contact position reliability calculation means for calculating a piston speed until the provisional contact position is set based on a piston position detected by the position detection means, and calculating a reliability of the provisional contact position based on the piston speed; ,
And a contact position detecting means for correcting the temporary contact position based on the reliability and storing the corrected position as a contact position. Previous contact position reliability calculation that calculates the reliability of the previous contact position based on the elapsed time from the time when the contact position was stored by the contact position detection unit before the temporary contact position was detected by the temporary contact position detection unit Having means,
The contact position detection means corrects the temporary contact position based on the reliability of the previous contact position and the reliability of the temporary contact position reliability calculation means, and stores it as a contact position. 4. The brake device according to 4.

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