JP3695171B2 - Electric brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform accurate control in various current control of an electric motor in a motor-driven braking device for a vehicle. SOLUTION: This braking device is provided with a pad disposed opposedly to a disc rotated integrally with a wheel, and an electric motor for pressing the pad to the disc through a driving member to apply braking force to the wheel. In the stop state of the electric motor, the driving current of the electric motor is gradually increased (step 222). In the gradually increased state of the driving current, the driving current at the time of the electric motor starting its rotating action is determined as the minimum driving current of the electric motor (step 214-220, 224). Even with the change of environment in which the braking device is placed, the minimum driving current corresponding to the environment is detected, and the electric motor is current-controlled using the minimum driving current, so that the current control can be performed always accurately.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric brake device for a vehicle that brakes wheels using an electric motor.
[0002]
[Prior art]
Conventionally, for example, as shown in International Publication No. WO 97/12794, a friction member provided facing a rotating body that rotates integrally with a wheel, and for driving the friction member toward the rotating body And an electric motor that displaces the drive member in conjunction with the rotational operation, and the electric motor for the vehicle brakes the rotation of the wheel by pressing the friction member against the rotating body by rotating the electric motor. Are known. Further, the publication discloses that a constant target driving current is passed through the electric motor to rotate the electric motor with a constant driving torque, and the friction member is driven through the driving member by the same rotation. It is introduced to detect the reference rotation angle (corresponding to the origin position in the displacement of the drive member) of the electric motor that starts to apply a frictional force in contact with the motor.
[0003]
[Problems to be solved by the invention]
In this type of electric brake device, in order to rotate the electric motor in a stopped state together with the drive member, it is necessary to pass a minimum drive current of at least a certain magnitude to the electric motor, and this minimum drive current is It changes depending on the environment such as the temperature of the device. However, the prior art described in the above publication does not consider the change in the minimum drive current, and cannot generate a desired drive torque with high accuracy in the electric motor.
[0004]
SUMMARY OF THE INVENTION
The present invention has been made to address the above problems, and its purpose includes current control of an electric motor for detecting a reference rotation angle of the above-described conventional device, and application of braking force by current control of the electric motor. Another object of the present invention is to provide a vehicular electric brake device capable of performing highly accurate control in various current control of an electric motor in the vehicular electric brake device.
[0007]
  In order to achieve the above object, the present invention provides a friction member that abuts against a rotating body that rotates integrally with a wheel to generate a braking force, and the friction member in conjunction with a rotational operation of an electric motor that is started during braking. A drive member that is displaced relative to the rotating body, and a drive according to the target drive current by applying to the electric motor a target drive current determined according to the amount of depression of the brake pedal of the vehicle. An electric brake device for a vehicle including a drive current control unit that rotationally drives the electric motor with a torque, a displacement detection unit that detects a displacement amount of the drive member according to a rotation operation of the electric motor, and the electric motor Is the minimum drive current required to displace the drive member ( I *) Is applied to the electric motor, and the displacement amount of the drive member detected by the displacement detection means ( S ) Based on a temporary origin position where the driving member is located in a state where the friction member is separated from the rotating body ( So ' ) To obtain the temporary origin position ( So ' ) Is obtained, the drive current when the drive member starts to be displaced from the temporary origin position by reapplying the drive current to the stopped electric motor and gradually increasing the drive current is obtained. Based on the detection signal of the displacement detecting means, the minimum driving current at the temporary origin position ( Io ) And the minimum driving current at the temporary origin position detected by the driving current detecting means is applied to the electric motor, and the friction member starts to come into contact with the rotating body. The present invention provides an electric brake device for a vehicle characterized by comprising an origin position determining means for determining an origin position based on a displacement amount of the driving member detected by the displacement detecting means.
[0008]
  In the electric brake device for a vehicle configured as described above, the usage environment of the vehicleHas changedIt is given when the electric motor startsEven if the minimum drive current changes,ThatChanged environmentTo accurately determine the origin position of the drive member (pad push shaft) when starting the electric motor.Rotate the electric motorThoughDetects the minimum required drive currentcan do. As a result, the drive current applied to the electric motor at the time of braking can always be controlled accurately according to the target drive current.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the entirety of the vehicle electric brake device according to the embodiment. This vehicle is provided with a disc-type brake unit 10 at each of the front, rear, left and right wheel positions (only one is shown).
[0010]
  As shown in detail in FIG. 2, each brake unit 10 is opposed to the disk 11 on each side of the disk 11 as a rotating body that rotates around the axis in the horizontal direction of the figure integrally with the wheel. Pads 12a and 12b as a pair of friction members disposedThese pads 12 a , 12 b AssembledAnd caliper 13. The caliper 13 is assembled to a vehicle body (not shown) so as to be displaceable in the axial direction of the disk 11, and a pad 12a on the outside (right side in the figure) of the disk 11 is fixed by a back metal 12a1 of the pad 12a. The pads 12a and 12b and the back metal 12a1 and 12b1 fixed to the back surfaces thereof are separated from the disk 11 by springs (not shown).WeakIt is energized with strong force. In the caliper 13, an electric motor 20 constituted by a DC motor is accommodated.
[0011]
  The electric motor 20 includes a stator 21. The stator 21 is formed in a ring shape by arranging a plurality of coils to which current is supplied in the circumferential direction, and is arranged around an axis line in the horizontal direction in the drawing, on the inner circumferential surface of the caliper 13. It is fixed so that it cannot rotate. Of the stator 21On the inner peripheryA cylindrically formed rotor 22 is arranged coaxially with the stator 21. A plurality of permanent magnets 22a are fixed along the circumferential direction on the outer peripheral surface of the rotor 22, and the rotor 22 rotates about its axis with respect to the stator 21 in response to supply of current to each coil of the stator 21. It is designed to rotate. A cylindrical nut 23 is coaxially fixed on the outer peripheral surface of the rotor 22.
[0012]
  The nut 23 is supported on the inner peripheral surface of the caliper 13 so as not to move in the axial direction but to be rotatable around the axial line., BWhen the rotor 22 rotates,Turn togetherRoll. A cylindrical shaft 24 is assembled on the inner peripheral surface of the nut 23 so as to be coaxial with the nut 23 and cannot rotate around the axis and can be displaced in the axial direction. This shaft24Constitutes a drive member for pressing and driving the pads 12a and 12b. Inner circumference of nut 23A plurality of screw rollers 25 are parallel to each other at equal intervals in the circumferential direction on the threaded portion formed on the outer surface of the shaft and the shaft 24.It is screwed. Each screw roller 25 displaces the shaft 24 in the axial direction while rotating around each axis in accordance with the rotation of the nut 23.
[0013]
    In the electric motor 20 configured as described above, even if a driving current is supplied to the motor 20 (specifically, a coil that constitutes the stator 21), the driving current is reduced due to frictional forces of the nut 23, the screw roller 25, and the like. If it is small, the shaft 24 cannot be displaced in the axial direction, and the shaft 24 is not displaced in the axial direction unless the current exceeds a certain level. In the present specification, the minimum driving current required to rotate the electric motor 20 to displace the shaft 24 is referred to as a minimum driving current Io. The minimum drive current Io varies depending on the temperature of grease packed between the nut 23 and the screw roller 25, for example, the environment where the brake unit 10 is placed, and includes the electric motor 20. partsTo the differenceIt is also different.
[0014]
  When the shaft 24 is displaced in a direction protruding from the nut 23 (right direction in the drawing), first, the shaft 24 abuts on the back metal 12b1 of the pad 12b on the inner side of the disk 11 at the tip. After the contact, the pad 12b is displaced integrally with the shaft 24 so that the inside of the disk 11On the facePress against it. At this time, the caliper 13 is displaced in the direction opposite to the displacement direction of the shaft 24 with respect to the disk 11 by the reaction force, and the pad 12a outside the disk 11 is moved outside the disk 11.On the facePress. Thus, the electric motor 20 displaces the pads 12a and 12b and presses them on both sides of the disk 11 according to the supply of the drive current.Act on. At this time, due to the friction between the disk 11 and the pads 12a and 12b, the rotation of the disk 11 is braked and the rotation of the wheels is braked.
[0015]
  The electric motor 20 includes a rotary encoder 26.ButIt is assembled. The rotary encoder 26 includes a plurality of magnets 26a that are arranged on the rotor 22 in the circumferential direction, and the caliper 13 that faces the magnets 26a.On the inner wallA plurality of Hall elements 26b arranged in parallel are provided, and as the rotor 22 rotates with respect to the caliper 13, the approach of the magnet 26a is detected for each Hall element 26b, and a signal representing each detection is output.
[0016]
  Further, this vehicle includes a microcomputer 30. The microcomputer 30 instructs each drive circuit 31 of the current flowing through the electric motor 20 of each brake unit 10 by executing a program corresponding to the flowcharts of FIGS. The motors 20 are rotated. Each drive circuit 31 receives a control signal representing the indicated current from the microcomputer 30 and also receives a signal representing the drive current flowing through each electric motor 20 detected by each ammeter 32. The drive current of the motor 20 is feedback-controlled to the indicated current. Ammeter32Is provided in a current path from each drive circuit 31 to each electric motor 20, detects a current actually flowing through each electric motor 20, and sends a signal indicating the detected current value to each drive circuit 31. Each is input and also supplied to the microcomputer 30.
[0017]
The microcomputer 30 is connected to each rotary encoder 26 via each converter 33 and also to a pedal stroke sensor 34. The converter 33 detects the displacement amount of the shaft 24 together with the rotary encoder 26, and converts the detection signal for each Hall element 26a of the rotary encoder 26 into a signal representing the displacement amount S from the reference position of the shaft 24. And output to a microcomputer. The displacement amount S also corresponds to the rotation amount of the electric motor 20. The converter 32 is also connected to the drive circuit 31, and the detection signal from the rotary encoder 26 is converted into a signal representing the relative position of the rotor 22 with respect to the stator 21 by the converter 32 and then the drive circuit 31. And is also used for operation control of the electric motor 20 by the drive circuit 31. The pedal stroke sensor 34 is assembled to a brake pedal BP that is depressed by the driver, detects the depression amount of the brake pedal BP as a pedal stroke amount Sp, and generates a detection signal representing the detected pedal stroke amount Sp. Output to the microcomputer 30.
[0018]
Next, the operation of the first embodiment configured as described above will be described with reference to the flowcharts of FIGS. When an ignition switch (not shown) is turned on, the microcomputer 30 is controlled by a built-in timer and repeatedly executes the main program in FIG. 3 every predetermined short time. Execution of this program is started at step 100, and an origin detection routine is executed at step 102.
[0019]
  The origin detection routine24The origin position So in this displacement is detected. The origin position So is a position where the pads 12a and 12b start to contact the disk 11.
[0020]
The details of this origin detection routine are shown in FIG. 4. The microcomputer 30 starts executing the routine at step 200, and determines at step 202 whether or not the origin position So has not been detected. If the detection of the origin position So has already been completed, “NO” is determined in Step 202, and the execution of this origin detection routine is terminated in Step 204. On the other hand, immediately after the ignition switch is turned on, if the detection of the origin position So has not ended yet, “YES” is determined in the same step 202, and the program executes the origin position detection process after the step 206. To do. In this determination, the origin position So is detected only once every time the ignition switch is turned on, that is, every time the vehicle starts, and a flag (not shown) that is reset when the ignition switch is turned on is set to “ It is determined by setting it to “1” when determining “YES”.
[0021]
  If “YES” is determined in step 202 as described above, the microcomputer 30 first determines a temporary origin position So ′ by the processing in steps 206 to 212. As shown in FIG. 5, the temporary origin position So ′ is surely smaller than the true origin position So (corresponding to the leftward displacement of the shaft 24 in FIG. 2), that is, the pads 12a and 12b are It is a position that is surely separated from the disk 11 and fits at least in the use area of the brake unit 10. The use area of the brake unit 10 is the shaft24Is within a range that can normally be displaced. In contrast, the shaft24If the disc is displaced too much in the opposite direction to the disc 11, the shaft24This displacement enters the destruction region where the operation of the brake unit 10 is not ensured.
[0022]
The operation for determining the provisional origin position So ′ will be described in detail. The microcomputer 30 adds a predetermined value α1 determined in advance to the minimum drive current Io in step 206, and the added current value I *. A control signal representing = Io + α1 is output to the drive circuit 31 for a predetermined short time. This minimum drive current Io is the minimum drive current of the electric motor 20 necessary for displacing the shaft 24 in the right direction of FIG. 2 as described above and shown in FIG. 6, and is larger than this value. By causing the drive current to flow through the electric motor 20, the braking force F applied to the wheels increases as the drive current increases. The minimum drive current Io is a value that is updated by the previous processing in step 224 described later, and is stored in the nonvolatile memory or the like even after the ignition switch is turned off. The reason why the small predetermined value α1 is added is that the electric motor 20 is reliably rotated to displace the shaft 24 in the right direction in FIG. 2 and the pads 12a and 12b are reliably attached to the disk 11 by pressing the shaft 24. This is for pressing. In this case, since the minimum driving current Io is provisionally determined, a predetermined value that is considered to be the minimum driving current of the electric motor 20 may be used as the minimum driving current Io.
[0023]
  In response to the input of the short-time control signal, the drive circuit 31 causes the drive current I * = Io + α1 represented by the control signal to flow through the electric motor 20 in cooperation with the ammeter 32 for the short time. The motor 20 is rotated forward. The short-time forward rotation of the electric motor 20 is converted into a linear motion by the screw roller 25, and the shaft 24 is displaced rightward in FIG. 2 to press the back metal 12b1 of the pad 12b in the same direction. The pads 12a and 12b are pressed against the disk 11 with a force corresponding to the drive current I *. At the end of the short-time drive control for the electric motor 20, the microcomputer 30 detects the shaft detected by the rotary encoder 26 and the converter 33 in step 208.24The displacement amount S is input from the converter 33, and the input displacement amount S is temporarily stored as the first position S1 (see FIG. 5).
[0024]
  Next, in step 210, the microcomputer 30 reverses the electric motor 30 and rotates the shaft.24So that the displacement amount S of the shaft becomes the temporary origin position So ′ = S1-β1.24Is displaced (see FIG. 5). In this case, β1 is a predetermined value related to the first position S1 (the driving current I * = Io + α1), and the pads 12a and 12b are set at positions surely separated from the disk 11 and the shaft.24This displacement is determined so as not to enter the destruction area of the brake unit 10. In this embodiment, the shaft24Is controlled to be slightly separated from the back metal 12a1 of the pad 12a (for example, about 0.5 mm away), but if the pads 12a and 12b are separated from the disk 11, the shaft 24 The tip does not have to be separated from the back metal 12b1 of the pad 12b.
[0025]
  The processing of this step 210 is the shaft input from the converter 33.24The position feedback control using the displacement amount S of the drive circuit 31, until the displacement amount S becomes equal to the temporary origin position So ′ = S1-β1, the drive circuit 31 has a constant drive current for reversing the electric motor 30. Is sent to the motor 30. And, by reversing the electric motor 20, the shaft24When the displacement amount S becomes equal to the temporary origin position So ′ = S1-β1, the microcomputer 30 ends the process of step 210, and sets the drive current of the electric motor 20 to “0” in the drive circuit 31 in step 212. ".
[0026]
  Next, the microcomputer 30 gradually increases the drive current I * of the electric motor 20 by the processes in steps 214 to 224, while the electric motor 20 starts rotating and the shaft 24 starts to be displaced. The drive current I * is detected as the minimum drive current Io. Specifically, in step 214, the shaft from the converter 33 is changed.24Is input as the current displacement amount Sx, the previous displacement amount Sy is updated to the current displacement amount Sx in step 216, and the current displacement amount Sx is input from the converter 33 in step 218. The displacement amount S is updated, and it is determined in step 220 whether or not the current displacement amount Sx and the previous displacement amount Sy are equal. As long as both displacement amounts Sx and Sy are equal, “YES” is determined in step 220 and the drive circuit 31 is controlled in step 222 to gradually increase the drive current I * of the electric motor 20 from “0”. The processes in steps 216 to 220 are repeatedly executed.
[0027]
  When the displacement amounts Sx and Sy are not equal, it is determined as “NO” in step 220, and the drive current I of the electric motor 20 is input from the ammeter 32 in step 224 to minimize the drive current I. Set as drive current Io. As a result, the shaft from the converter 33 in a state where the drive current of the electric motor 20 is gradually increased.24When a change occurs in the displacement amount S, that is, the electric motor 20 starts to rotate and the shaft24Is set as the minimum driving current Io (see FIG. 6). If “NO” is determined in step 220, the drive current I * for instructing the drive circuit 31, which is the calculated value gradually increased by the calculation in step 222, is set as the minimum drive current Io. However, the minimum drive current Io is set to substantially the same value as in the above case.
[0028]
Next, the pads 12a and 12b are displaced toward the disk 11 by the processing of steps 226 to 234, and the displacement amount S of the shaft 24 when the pads 12a and 12b start to contact the disk 11 is set as the origin position So. Determine (see FIG. 5). Specifically, in step 226, a predetermined small predetermined value α2 is added to the set minimum drive current Io, and a control signal representing the drive current I * which is the same added value Io + α2 is output to the drive circuit 31. . The drive circuit 31 causes the drive current I * to flow to the electric motor 20, and the drive current I * has a value slightly larger than the minimum drive current Io, so that the electric motor 20 is connected to the shaft via the nut 23 and the screw roller 25. 24 and the pads 12a and 12b are gradually moved toward the disk 11 at a low speed.
[0029]
  After the processing in step 226, the previous displacement amount Sy is updated to the current displacement amount Sx in step 228, and the current displacement amount Sx is updated to the displacement amount S input from the converter 33 in step 230. Thus, it is determined whether or not the current displacement amount Sx and the previous displacement amount Sy are equal. If the electric motor 20 continues to rotate and the displacement amounts Sx and Sy are different, it is determined as “NO” in Step 232 and the circulation process consisting of Steps 228 to 232 is repeated. When the pads 12a and 12b come into contact with the disk 11 during this circulation process, the drive current to the electric motor 20 is substantially equal to the minimum drive current Io required to rotate the motor 20, and therefore the pads 12a and 12b. Thus, the electric motor 20 stops rotating. And since both said displacement amount Sx, Sy becomes equal, step232In step 234, the displacement amount S of the shaft 24 is input from the converter 33, and the displacement amount S is set as the origin position So. In step 236, the origin detection routine is terminated.
[0030]
  The driving force for displacing the pads 12a and 12b is the shaft.24It is extremely small compared to the driving force for displacing the shaft.24Will begin to displace, the pads 12a and 12b are almost displaced. Therefore, the minimum drive current Io is a minimum drive current necessary for rotating the electric motor 20, and at the same time, a minimum drive current required for displacing the pads 12a and 12b in a stationary state. Is almost equal to Accordingly, the predetermined value α2 for ensuring that the electric motor 20 is rotated at a low speed and the shaft 24 is displaced at a low speed may be a value close to “0”. In some cases, the predetermined value α2 may be “0”.
[0031]
After the end of the origin detection routine, the microcomputer 30 executes the processing after step 104 of the main program in FIG. In step 106, after inputting the stroke amount Sp of the brake pedal BP from the pedal stroke sensor 34, it is determined in step 106 whether or not the input stroke amount Sp is larger than “0”. If the brake pedal BP is not depressed and the pedal stroke amount Sp is not greater than “0”, “NO” is determined in step 106 and the program proceeds to step 108.
[0032]
In step 108, the shaft input from the converter 33.24The electric motor 20 is reversely controlled via the drive circuit 31 so that the displacement amount S becomes a value So−ΔS that is smaller than the origin position So by a predetermined small value ΔS. Thereby, the pads 12a and 12b can be reliably separated from the disk 11, and no drag resistance is applied to the disk 11. In addition, a brake switch (not shown) that is normally turned off and is turned on only when the brake pedal BP is depressed is provided, and instead of the processing of the step 106, the brake pedal BP is depressed and activated depending on the on / off state of the switch. The cancellation of the operation may be detected. After the processing of step 108, the execution of the main program is once terminated at step 118.
[0033]
On the other hand, when the brake pedal BP is depressed and it is determined “YES” in step 106, the microcomputer 30 refers to the stroke amount-displacement amount table provided in the computer 30 in step 110. A target displacement amount S * corresponding to the input stroke amount Sp is determined. As shown in FIG. 7, the target displacement amount S * is a value that increases substantially in proportion to the stroke amount Sp from “0” as the pedal stroke amount Sp increases from “0”.
[0034]
After the processing of step 110, the detected displacement amount S is input from the converter 33 in step 112, and the detected displacement amount S is obtained by subtracting the detected origin position So from the detected displacement amount S in step 114. to correct. Then, the rotation of the electric motor 20 is controlled through the drive circuit 31 so that the corrected displacement amount Sa = S−So matches the target displacement amount S * by the processing of step 116.
[0035]
Specifically, the corrected displacement amount S-So and the target displacement amount S * are compared. If the corrected displacement amount S-So is smaller than the target displacement amount S *, the drive circuit 31 is controlled to drive the electric motor 20. Increase current. If the corrected displacement amount S-So is equal to the target displacement amount S *, the drive circuit 31 is controlled to maintain the drive current for the electric motor 20 at the previous value. If the corrected displacement amount S-So is larger than the target displacement amount S *, the drive circuit 31 is controlled to reduce the drive current for the electric motor 20. By such control, the braking force F according to the depression operation of the brake pedal BP is applied to the wheels. In step 118, the execution of the main program is temporarily terminated.
[0036]
In the first embodiment configured as described above, every time the ignition switch is turned on, the temporary origin position So ′ is detected by the processing of steps 206 to 212, and the target drive current is processed by the processing of steps 214 to 224. The minimum drive current Io of the electric motor 20 is detected by gradually increasing I *, and the electric motor 20 is drive-controlled using the minimum drive current Io by the processing of steps 226 to 234 to set the true origin position So. It was made to detect. Therefore, even if there is a change in the environment in which the brake unit 10 is placed, such as temperature, or even if there are variations in the components including the electric motor 20, the minimum drive current Io is always determined with high accuracy. The detection of the origin position So using Io is always performed with high accuracy. And the application control of the braking force F which consists of steps 110-116 using this origin position So is always performed accurately.
[0037]
Next, a second embodiment obtained by modifying the first embodiment will be described. In the second embodiment, the electric motor 20 is driven and controlled by constant current control to apply braking force to the wheels, and the main program shown in FIG. 3 is changed to the main program shown in FIG. Other configurations are the same as those in the first embodiment except that the table provided in the microcomputer 30 is different.
[0038]
Also in the second embodiment, the origin detection routine (FIG. 4) is executed immediately after the ignition switch is turned on in step 102, as in the first embodiment. If the brake pedal BP is not depressed, control is performed so that the braking force is not applied to the wheels by the processing in steps 104 to 108. On the other hand, if the brake pedal BP is depressed, the program proceeds to step 120 and subsequent steps by the processing of steps 104 and 106.
[0039]
In step 120, the previous target braking force Fy * is updated to the current target braking force Fx *. Next, in step 122, the pedal stroke amount-braking force table is referred to, a braking force F corresponding to the pedal stroke amount Sp input in step 104 is determined, and the braking force F is determined as the current target braking force Fx. Set as *. As shown in FIG. 9, the target braking force F * gradually increases as the pedal stroke amount Sp increases.
[0040]
In step 124, the current target braking force Fx * and the previous target braking force Fy * are compared. If the current target braking force Fx * is equal to or greater than the previous target braking force Fy *, “YES” in step 124. And the program proceeds to step 126. In step 126, the target drive current I * is calculated by executing the following equation 1 using a predetermined constant a and the minimum drive current Io detected in the origin detection routine of step 102.
[0041]
[Expression 1]
I * = (Fx * / a) + Io
As shown in the graph of FIG. 6, the above formula 1 approximates that the driving current I of the electric motor 20 increases beyond the minimum driving current Io and therefore the braking force F applied to the wheels increases proportionally. Is. When the method of changing the braking force F according to the drive current I differs depending on the characteristics of the brake unit 10, the target drive current I * is determined using a table, a function equation, or the like corresponding to the method of change. You can do it.
[0042]
After the process of step 126, a control signal representing the target drive current I * is output to the drive circuit 31 in step 132. The drive circuit 31 causes the target drive current I * to flow through the electric motor 20 by current feedback control in cooperation with the ammeter 32. As a result, the electric motor 20 drives the shaft 24 via the nut 23 and the screw roller 25 with a driving force corresponding to the target driving current I *, and the shaft 24 presses the pad 12a with a pressing force corresponding to the driving force. , 12b are pressed against the disk 11, and the target braking force Fx * determined in step 122 is applied to the wheels. After the process of step 132, the execution of the main program is temporarily terminated at step 118.
[0043]
Further, when the driver weakens the depressing operation force of the brake pedal BP (however, the depressing operation of the brake pedal BP is not released), “NO”, that is, the current target braking force Fx * is the previous target in step 124. It is determined that the braking force is less than Fy *, and the program is advanced to steps 128 and 130. In step 128, the reactive current component ΔIh corresponding to the braking force F is determined with reference to a hysteresis table provided in the microcomputer 30. As shown in the driving current-braking force characteristic of FIG. 6, the reactive current component ΔIh is a current that does not change the braking force even when the driving current I to the electric motor 20 is decreased in a state where the braking force is applied to the wheels. The amount increases as the braking force F increases as shown in FIG. In step 130, the target drive current I * is calculated according to the following equation 2 using the reactive current component ΔIh, the constant a and the minimum drive current Io.
[0044]
[Expression 2]
I * = (Fx * / a) + Io−ΔIh
The above formula 2 determines the target drive current I * in consideration of the hysteresis characteristic described above, and the reduction ratio of the reactive current ΔIh and the braking force F accompanying the decrease in the drive current I is the braking force F described above. This is based on the fact that the ratio is almost the same as the increase ratio (see the broken line in FIG. 6). For example, as shown in FIG. 6, when the braking force F1 is reduced to the braking force F2 from the state in which the driving current I1 is passed through the electric motor 20 to obtain the braking force F1, the driving current-braking force characteristic is The solid line to be represented is translated leftward by the reactive current ΔIh, and the drive current I2 corresponding to the braking force F2 on the translated line becomes the target drive current I * to be supplied to the electric motor 20. Since the above formula 2 is an approximate expression and the characteristics of FIGS. 6 and 10 are also approximate, in order to further improve the control accuracy of the hysteresis characteristics, the previous drive current I and braking force F and a new one are used. It is also possible to use a map or the like that represents the relationship with the driving current I for obtaining a correct braking force F.
[0045]
Since the process of step 132 described above is executed after the process of step 130, the braking force applied to the wheel is controlled in accordance with the depression operation amount of the brake pedal BP in consideration of the hysteresis characteristic. Become.
[0046]
In the second embodiment that operates in this way, the target drive current I * is determined according to the stroke amount Sp of the brake pedal BP, and the braking force of the wheel is controlled by the determined target drive current I *. Therefore, a braking force according to the depression operation of the brake pedal BP is applied with a simple configuration. In this case, since the minimum drive current Io detected in the origin detection routine in step 102 is used to determine the target drive current I *, even if there is a change in the environment where the brake unit 10 is placed, the electric drive Even if each part including the motor 20 varies, the braking force applied to the wheel is controlled with high accuracy.
[0047]
In the origin detection routine, the minimum drive current Io and the origin position So are detected only once immediately after the ignition switch is turned on. However, the driver may not be able to detect the brake pedal BP. When there is no problem even if some frictional force is applied to the disk 11, the minimum drive current Io and the origin position So are more frequently used than in the above case, such as every predetermined time. May be detected. Further, the detection may be performed when the driver makes a request by operating the specific operation element for the detection. In the detection, the minimum drive current Io and the origin position So are determined by one detection operation. However, the minimum drive current Io and the origin position So are determined by averaging a plurality of detection results. You may make it do.
[0048]
In the origin detection routine, the origin position So is detected together with the detection of the minimum drive current Io. In the case of the second embodiment, the process of separating the pads 12a and 12b from the disk 11 in step 108 is performed. If the origin position So is not used by reversing the electric motor 20 for a short time and performing the separation process, it is not necessary to perform the origin detection process consisting of steps 226 to 234 in FIG. .
[0049]
In the first and second embodiments, the rotation amount of the electric motor 20 and the displacement amount S of the shaft 24 are detected by the rotary recorder 26 and the converter 33. However, the linear movement amount of the shaft 24 is determined. A linear sensor to be detected may be provided in the brake unit 10, and the detected value of the linear sensor may be used in place of the displacement amount S.
[0050]
In the first and second embodiments, a DC motor is used as the electric motor 20. However, as long as the electric motor 20 rotates with a driving torque corresponding to the driving current, an AC motor, a step motor, Various motors such as an ultrasonic motor can be used.
[0051]
In the first and second embodiments, the minimum drive current value Io according to the present invention is used for detecting the origin position So and applying a braking force by current control. When the electric motor 20 is subjected to constant current control, it can be used for other constant current control.
[0052]
Furthermore, although the first and second embodiments employ a disc-type brake as the brake unit 10, the effects of the present invention can be achieved even when a drum-type brake is employed as the brake unit 10. Can be fully expected.
[Brief description of the drawings]
FIG. 1 is an overall block diagram of an electric brake device for a vehicle according to first and second embodiments of the present invention.
FIG. 2 is a longitudinal sectional view of the brake unit of FIG.
FIG. 3 is a flowchart showing a main program executed by the microcomputer of FIG. 1 according to the first embodiment of the present invention.
4 is a flowchart showing details of an origin detection routine in FIG. 3;
FIG. 5 is a graph showing a relationship between a shaft displacement amount S (rotation amount of an electric motor) and a braking force F;
FIG. 6 is a graph showing the relationship between the drive current I and the braking force F of the electric motor.
FIG. 7 is a graph showing a relationship between a brake pedal stroke amount Sp and a shaft target displacement amount S *.
FIG. 8 is a flowchart showing a main program executed by the microcomputer of FIG. 1 according to the second embodiment of the present invention.
9 is a graph showing a relationship between a brake pedal stroke amount Sp and a braking force F. FIG.
FIG. 10 is a graph showing a relationship between a braking force F and a reactive current amount ΔIh accompanying hysteresis.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Brake unit, 11 ... Disc, 12a, 12b ... Pad, 20 ... Electric motor, 26 ... Rotary encoder, 30 ... Microcomputer, 31 ... Drive circuit, 32 ... Ammeter, 33 ... Converter, 34 ... Pedal stroke sensor , BP ... Brake pedal.

Claims (5)

A friction member that abuts on a rotating body that rotates integrally with a wheel to generate a braking force, and displaces the friction member relative to the rotating body in conjunction with a rotating operation of an electric motor that is activated during braking. A drive member and a drive current control for applying a target drive current determined according to a brake pedal depression amount of the vehicle to the drive member and rotating the electric motor with a drive torque according to the target drive current A vehicle electric brake device comprising:
A displacement detecting means for detecting a displacement amount of the drive member in accordance with a rotation operation of the electric motor;
The friction member is rotated based on a displacement amount of the driving member detected by the displacement detecting means by applying a minimum driving current necessary for starting the electric motor and displacing the driving member to the electric motor. Position detecting means for obtaining a temporary origin position ( So ' ) where the drive member is located in a state of being separated from the body ;
After the provisional origin position ( So ' ) is obtained by the position detection means, the drive member is applied to the electric motor in a stopped state by applying a drive current again and gradually increasing the drive current. Drive current detection means for detecting the drive current when starting to be displaced from the temporary origin position as the minimum drive current at the temporary origin position based on the detection signal of the displacement detection means;
The displacement detection unit detects the displacement detection unit when the minimum drive current at the temporary origin position detected by the drive current detection unit is applied to the electric motor and the friction member starts to contact the rotating body. An electric brake device for a vehicle, comprising: an origin position determining means for determining an origin position based on a displacement amount of a driving member. The target drive current applied to the electric motor under the control of the drive current control unit is corrected based on the origin position determined by the origin position determination unit. Electric brake device for vehicles. When the current target drive current determined in accordance with the amount of depression of the brake pedal of the vehicle is smaller than the previously determined target drive current, the current target drive current is reduced in the hysteresis in the interlocking mechanism between the electric motor and the drive member. 2. The vehicle electric brake device according to claim 1, wherein the electric brake device is reduced in consideration. When the brake pedal of the vehicle is released, the electric motor generates a drive current corresponding to a displacement amount by which the drive member moves backward to a position obtained by subtracting a predetermined value from the origin position determined by the origin position determination means. The electric brake device for a vehicle according to claim 1, wherein the electric motor is reversely applied to the vehicle. A friction member that abuts on a rotating body that rotates integrally with the wheel to generate a braking force, and displaces the friction member relative to the rotating body in conjunction with a rotating operation of an electric motor that is activated during braking. A drive member and a drive current control for applying a target drive current determined in accordance with a brake pedal depression amount of the vehicle to the drive member and rotating the electric motor with a drive torque in accordance with the target drive current A vehicle electric brake device comprising:
2. The target drive current is decreased in consideration of hysteresis in an interlocking mechanism between the electric motor and the drive member in accordance with a decrease in an operation amount of a brake pedal of the vehicle. Electric brake device for vehicles.

Images