JP2015116921A - Electric parking brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect malfunction by detecting a position or displacement of a plunger without providing a sensor, and at that time, to reduce loss and a mounting space, in a parking brake mechanism for an automobile using a solenoid.SOLUTION: After applying a direct current to a solenoid 9 and locking it, an AC component is applied. Thereby, when a position of a lock pin 8 is changed, inductance of a coil 37 changes and a resonance frequency changes. Therefore, malfunction can be detected by detecting the position or displacement of the lock pin 8 from the change. Thus, as it is not necessary to provide a sensor, cost can be lowered. Also, an installation space for a sensor is not required. Furthermore, large power is not required and loss is small, as all that is required is to overlap the AC component.

Description

The present invention relates to an electric parking brake device using an electric brake.

As an electric parking apparatus using an electric brake, there is an electric disc brake apparatus of Patent Document 1.
This brake device has proposed a parking brake mechanism for automobiles using a solenoid.
Here, since the mechanical part of this brake device has substantially the same configuration as the electric parking brake device of the present application, it will be described with reference to FIG. 1 showing an embodiment of the present application.

As shown in FIG. 1, the brake device includes an electric brake 1 and parking means 2.
The electric brake 1 has a configuration in which an electric motor 3 and a linear motion mechanism 4 are connected via a speed reduction mechanism 5, and a brake pad 6 a attached to the linear motion mechanism 4 by rotation of the electric motor 3 is connected to a brake rotor 7. Press to brake.
On the other hand, the parking means 2 includes an engaging member 8 and a solenoid 9, and operates the plunger 10 of the solenoid 9 to engage the engaging member 8 provided at the tip of the plunger 10 with the speed reduction mechanism 5. To lock.

By the way, in the case where the service brake (foot brake) for automobile and the parking brake are integrated as described above, there are the following problems.
For example, when the electric motor 3 is activated before the engaging member 8 is separated from the speed reduction mechanism 5 when the parking unit 2 is released, the engaging member 8 or the engaging member 8 is applied with the brake torque generated by the operated electric motor 3. The solenoid 9 is broken together with the engaged plunger 10. On the contrary, when the parking brake is operated, if the plunger 10 does not reach the predetermined position, the engaging force of the engaging member 8 is insufficient and the parking brake does not work. Therefore, detection of the position or displacement of the plunger 10 is essential.

  As one method for solving such a problem of malfunction, a method of detecting the position of the plunger 10 by arranging a secondary coil coaxially with the coil 37 (see FIG. 4) of the solenoid 9 is conceivable.

JP 2012-087889 A

However, in the method of separately providing a sensor as described above, it is necessary to arrange the secondary coil at a limited location on the same axis as the solenoid coil. For this reason, there may be a problem that it is necessary to secure an installation space and a problem that the wiring system is complicated.
Moreover, since the number of parts increases by adding a sensor, the risk of failure also increases.

As a method for solving this problem, for example, it is conceivable to apply an AC voltage to the solenoid and detect a change in inductance caused by the displacement of the plunger.
That is, when the solenoid is connected to the AC power source e,
e = (r + jωL) × i
It is. Here, if the AC power supply is output resistance r << | jωL |
e = ωLi (i: constant current of AC power supply)
Therefore,
L = e / ωi = e / 2πfi
Thus, the inductance L can be detected.
At this time, the inductance L of the solenoid is proportional to the number of interlinkage magnetic fluxes. Therefore, the inductance L changes according to the displacement of the plunger, which is a magnetic body that moves in the solenoid. Therefore, the displacement of the plunger can be detected by detecting the inductance L. Thus, the displacement of the plunger can be detected without providing a sensor, and the position can be calculated from the detected displacement.

In the above method, an AC voltage is applied to the solenoid for detection. However, when the solenoid is a DC solenoid, it does not function as a solenoid even when an AC voltage is applied.
Therefore, in the DC solenoid, for example, if the control is performed such that the displacement is detected by time division by switching between a direct current and an alternating voltage, the displacement can be detected while the solenoid is functioning.

However, in the above method, since direct current and alternating voltage are switched and supplied to the solenoid by time division, switching in a short time is difficult. In addition, noise may be generated due to switching.
Furthermore, since a voltage source that supplies an AC voltage must output an AC voltage having an amplitude and frequency suitable for detection, there is a problem in that loss due to conversion occurs. In particular, in the case of a vehicle, since it is driven by a battery, there is a problem of reducing these losses.
In addition, when a loss occurs in this way, a space for providing a heat sink for dissipating the loss and a space for mounting an AC voltage source circuit are also required.

  Accordingly, an object of the present invention is to detect a malfunction by detecting the position or displacement of a plunger without providing a sensor. At that time, the loss is reduced and the mounting space is also reduced.

  In order to solve the above problems, in the present invention, an electric motor, a linear motion mechanism, a speed reduction mechanism that connects the electric motor and the linear motion mechanism, and a linear motor driven by the rotation of the electric motor via the speed reduction mechanism. An electric brake composed of a friction member that is mounted on the moving mechanism and pressed against the brake rotor, and a parking means that engages and engages the engaging member with the deceleration mechanism by the operation of a plunger of a DC solenoid. In the electric parking brake apparatus, a power supply means for supplying a direct current to the solenoid, an oscillating means for outputting an alternating current component superimposed on a direct current supplied by the power supply means, and a direct current supplied from the power supply means to the solenoid are provided. The first switching means for turning on and off, and the direct current supplied to the solenoid by the first switching means, the oscillation means A second switch means for applying an AC component to be output at a timing when the engaging member is locked to the speed reduction mechanism, and a position of a plunger of the solenoid from a change in detection values at both ends of the solenoid coil to which the AC component is applied; A configuration provided with processing means for estimating the displacement was adopted.

By adopting such a configuration, in the electric parking brake device, when the parking means is activated, the first switch means is turned on to apply a direct current to the solenoid to lock the engaging member to the speed reduction mechanism. Next, the second switch means is actuated to superimpose an AC component on the supply current of the solenoid after locking. Then, the position or displacement of the solenoid plunger is detected, and it is estimated whether a predetermined position has been reached.
That is, in the solenoid, when the positional relationship between the coil and the plunger inside the coil changes, the impedance of the coil changes. At this time, the impedance of the coil is expressed by XL = r + jωL (L: inductance of the coil). Therefore, if the AC component of the required frequency is superimposed on the solenoid input and a change in the detection value at both ends of the solenoid coil (for example, a change in the self-resonance point) is detected, the position or displacement of the plunger can be changed without providing a sensor. Can be estimated.
At this time, if the AC component is superimposed, for example, a constant voltage power supply such as an in-vehicle battery cannot apply a voltage exceeding the power supply voltage to the solenoid coil, so that a decrease in displacement detection accuracy due to waveform distortion of the AC component is avoided. In addition, it is necessary to superimpose the AC component after reducing the DC component to at least the amplitude of the AC component, and the output current decreases. For this reason, it is conceivable that a predetermined adsorption force cannot be obtained, and the safety factor against the plunger protrusion failure is affected. Therefore, first, the first switch means is turned on so that the current does not decrease, and the solenoid is operated without superimposing the AC component. Then, after an increase in attraction force due to the increase in inductance due to the stroke of the plunger exceeds the reduction in attraction force due to the decrease in the output current, a predetermined adsorption is performed by superimposing an AC component. To gain power. As a result, it is not necessary to increase the number of windings of the solenoid coil or increase the power source in order to compensate for the current value that decreases due to the superposition of the AC component, and thus the coil and the power source can be reduced in size.
In addition, since the oscillation output is superimposed on the direct current and the change in the detection value at both ends of the solenoid coil (for example, the change in the self-resonance point) is detected, the oscillation output does not require a large amount of power, has little loss, and is installed Space is not required.

At this time, the solenoid is provided with an elastic mechanism for restoring the plunger to the starting position, the driving current of the solenoid is I1, and the holding current for holding the plunger after the activation against the elastic mechanism Where I2 (I1> I2) and ΔI <I1-I2 can be employed, where ΔI is the amount of decrease in effective current after the oscillation means output is applied.

  By adopting such a configuration, when the solenoid plunger is attracted (lock pin is locked) and returned (lock pin is separated), the drive current I1 is increased due to an increase in solenoid coil inductance accompanying the plunger attract. And a holding current I2 form a hysteresis satisfying I1> I2. By placing the effective current reduction amount ΔI due to the superimposition of the alternating current component within the hysteresis of I 1 -I 2, it is possible to detect the displacement and the position while guaranteeing the influence of the decrease in the attractive force due to the superposition of the alternating current component.

  Further, at this time, it is possible to employ a configuration provided with timer means for operating the second switch means by time-up at the timing when the engaging member is locked to the speed reduction mechanism.

  By adopting such a configuration, it is possible to determine that the stroke of the plunger has reached the length for locking the engaging member by determining the passage of time from the activation of the solenoid (application of current). And the output of the oscillation means is superimposed on the direct current. Thus, the application of the oscillation means output can be controlled by a convenient method using a timer.

  Further, at this time, it is possible to employ a configuration in which the frequency of the AC component applied to the solenoid is at least equal to or higher than the operating frequency of the solenoid.

By adopting such a configuration, setting the AC component frequency higher than the frequency at which the solenoid can respond makes it easy to determine the AC component, so displacement and position can be detected in a short time. Become. In addition, since the wavelength of the AC component becomes shorter, the detection resolution can be increased and the detection system can be improved. Furthermore, since the solenoid cannot respond to the frequency of the AC component, the component can be prevented from affecting the operation of the solenoid.

  Moreover, the structure which estimates the protrusion amount of an engaging member from the movement difference of the plunger before operation | movement of the said solenoid and after operation | movement can be employ | adopted.

  By adopting such a configuration, the amount of protrusion of the engaging member can be estimated. For example, the operating state of the parking brake can be determined by calculating the degree of engagement of the engaging member from the estimated value.

  At this time, before the operation of the parking means, a measurement current that does not move the plunger is input to the solenoid, the coil temperature is calculated based on the measured value at that time, and the calculated coil temperature is calculated. Thus, it is possible to employ a configuration in which the estimated position of the engaging member is calibrated.

  By adopting such a configuration, by inputting a minute measurement current that does not cause displacement of the plunger, for example, the resistance value of the coil is calculated from the measurement voltage at that time. Then, from the resistance value, the internal temperature of the coil after energization is estimated using a resistance method using the temperature coefficient of copper, etc., and the plunger is reduced by taking into account the decrease in the attraction force / holding force of the coil due to this estimated temperature. Can be calibrated.

  At this time, when the electric brake is operating and the parking means is not operated, the position of the solenoid plunger is calculated at regular intervals, and the engagement member is separated from the speed reduction mechanism. A configuration for confirming the maintenance of the state can be adopted.

  By adopting such a configuration, the position of the plunger is detected at regular intervals even when the parking unit is not in operation, and the separation state of the engaging member from the speed reduction mechanism is sequentially detected. Thus, safety can be ensured by always confirming the engaged state due to the malfunction of the parking means from the separated state.

  Further, the position of the solenoid plunger is calculated at regular intervals while the electric brake is inactive and the parking means is in operation, and the engagement state of the engagement member with the speed reduction mechanism is calculated from the calculated position. A configuration of confirming maintenance can be adopted.

  By adopting such a configuration, the position of the plunger is detected at intervals of a constant time shorter than the operation cycle of the solenoid, and the engagement state between the engagement member and the speed reduction mechanism is sequentially detected. By carrying out like this, since the engagement state of an engagement member and a speed-reduction mechanism can always be confirmed, safety | security can be ensured.

At this time, if the first switch means also serves as the second switch means, only one switch means is required, so that the size, the loss and the cost can be reduced.

  Since the present invention is configured as described above, the displacement and position of the lock pin can be detected from the detection of the plunger, so that the protruding state of the lock pin and the lock state of the pin can be detected. Therefore, it is possible to prevent an accident due to a malfunction of the solenoid. At that time, since the position or displacement can be detected without providing a separate sensor, size and cost can be reduced.

Cross-sectional view of the embodiment 1 is a longitudinal sectional view of the linear motion mechanism of FIG. 2 is a longitudinal sectional view Sectional view of the solenoid of FIG. (A) Action explanatory view of FIG. 1, (b) Action explanatory view of main part of (a) Circuit block diagram of the embodiment Action explanatory diagram of the embodiment Block diagram of displacement detector of embodiment Action explanatory diagram of the embodiment Action explanatory diagram of the embodiment Action explanatory diagram of the embodiment Circuit diagram of another form of switch means

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, the electric parking brake device of this embodiment includes an electric disc brake 1 for an automobile and a parking means 2 using a solenoid 9.

  The electric disc brake 1 has a structure in which an electric motor 3 and a linear motion mechanism 4 are connected via a speed reduction mechanism 5, and a brake pad 6 a mounted on the linear motion mechanism 4 is pressed against the brake rotor 7.

  Here, the electric motor 3 employs a DC motor, so that the reversible operation of the electric motor 3 can be easily performed only by reversing the polarity of the power source.

As shown in FIG. 2, the linear motion mechanism 4 includes an outer ring member 11, a bearing member 12, and a carrier 13, and is accommodated in a cylindrical housing 14. Further, as shown in FIG. 1, a base plate 15 is provided at one end of the cylindrical housing 14 so as to extend radially outward, and the cover 16 covers an outer surface of the base plate 15 and an opening at one end of the housing 14. It has a structure that is called. Further, the electric motor 3 is attached to the base plate 15, and the rotation of the electric motor 3 is transmitted to the rotary shaft 17 by the speed reduction mechanism 5 incorporated in the cover 16.
On the other hand, a caliber body 18 is integrally attached to the other end of the housing 14 as shown in FIG. The caliber body 18 is provided with a fixed brake pad 6b and a movable brake pad 6a on both sides of the brake rotor 7 in which a part of the outer peripheral portion is disposed, and the movable brake pad 6a is connected to the other end of the outer ring member 11. And integrated structure.

  The outer ring member 11 is incorporated as a slide member, is prevented from rotating, and is movable in the axial direction along the inner diameter surface of the housing 14. Further, as shown in FIG. 2, a spiral protrusion 19 having a V-shaped section and a spiral shape is provided on the inner diameter surface thereof.

  As shown in FIG. 2, the bearing member 12 is a disk-shaped member having a boss portion at the center, and is incorporated on one end side of the outer ring member 11 in the axial direction. In addition, a pair of rolling bearings 20 are incorporated in the boss portion at the center of the bearing member 12 with a space therebetween, and the rotating shaft 17 disposed on the axis of the outer ring member 11 by the rolling bearing 20 is provided. It is supported rotatably. The built-in bearing member 12 is prevented from moving toward the cover 16 that covers the open end of the housing 14 by a stopper ring 21 attached to the inner peripheral surface of the housing 14.

As shown in FIGS. 2 and 3, the carrier 13 includes a pair of disks 13 a and 13 b facing each other in the axial direction, a plurality of interval adjusting members 13 c and a plurality of roller shafts 13 d. A planetary roller 13e is rotatably supported on the plurality of roller shafts 13d, and is incorporated inside the outer ring member 11 so as to be rotatable about the rotation shaft.
That is, the carrier 13 is provided with a plurality of interval adjusting members 13c spaced from each other on the outer peripheral portion of one disk 13a toward the other disc 13b in the circumferential direction, and on the end surface of the interval adjusting member 13c. A pair of opposing disks 13a and 13b are connected by tightening a screw to be screwed.
Of the pair of disks 13a and 13b, the inner disk 13b positioned on the bearing member 12 side is rotatable by a slide bearing 22 built in between the rotating shaft 17 and is movable in the axial direction. It is supported.
On the other hand, the outer side disk 13a is formed with a shaft insertion hole 23 formed of a stepped hole in the center, and is supported rotatably with respect to the rotary shaft 17 by a slide bearing 24 fitted in the shaft insertion hole 23. Has been. The rotating shaft 17 is fitted with a metal washer 25 that receives a thrust load adjacent to the outer end face of the slide bearing 24, and the washer 25 is a retaining ring 26 attached to the shaft end of the rotating shaft 17. It has been retained by.

  Each of the plurality of roller shafts 13d is supported by a shaft end portion inserted into a shaft insertion hole 27 formed of a long hole formed in a pair of discs so as to be movable in the radial direction. It is urged | biased to radial direction by the elastic ring 28 spanned so that 13d might be wound. A planetary roller 13e is rotatably supported on each of the plurality of roller shafts 13d.

As shown in FIG. 3, each of the planetary rollers 13e is arranged between the outer diameter surface of the rotating shaft 17 and the inner diameter surface of the outer ring member 11, and as described above, the inner diameter surface of the outer ring member 11 is incorporated. The roller shaft 13d incorporated therebetween is pressed against the outer diameter surface of the rotating shaft 17 by an elastic ring 28 spanned between both shaft ends so as to be in elastic contact. Therefore, when the rotating shaft 17 rotates, the rotating shaft 17 rotates by contact friction with the outer diameter surface of the rotating shaft 17.
Further, as shown in FIG. 2, a plurality of spiral grooves 29 having a V-shaped cross section are formed on the outer diameter surface of the planetary roller 13e at equal intervals in the axial direction. The pitch of the spiral grooves 29 is the same as the pitch of the spiral ridges 19 provided on the outer ring member 11 described above, and is screwed into the spiral ridges 19. Instead of the spiral groove 29, a plurality of circumferential grooves may be formed at equal intervals in the axial direction at the same pitch as the spiral protrusions 19.

  As shown in FIG. 2, a washer 30 and a thrust bearing 31 are incorporated between the planetary rollers 13e and the axially opposed portions of the inner disk 13b of the carrier 13. Further, an annular thrust plate 32 is incorporated between the carrier 13 and the bearing member 12 in the axial direction, and a thrust bearing 33 is incorporated between the thrust plate 32 and the bearing member 12.

  The opening at the other end located outside from the opening at the other end of the housing 14 of the outer ring member 11 is blocked by the attachment of the seal cover 34 to prevent foreign matter from entering the inside.

As shown in FIG. 1, the speed reduction mechanism 5 sequentially reduces the rotation of the input gear attached to the rotor shaft of the electric motor 3 in the order of a primary reduction gear train G1, a secondary reduction gear train G2, and a tertiary reduction gear train G3. Then, it is transmitted to the output gear 35 attached to the wheel end of the rotating shaft 17 to rotate the rotating shaft 17.
The deceleration mechanism 5 is provided with parking means 2 that can lock and unlock the rotor shaft of the electric motor 3.

The parking means 2 includes a lock pin 8 that is an engaging member 8 and a pin driving solenoid 9. As shown in FIG. 4, the pin driving solenoid 9 is a push type actuator in which a return spring 36 is incorporated in a linear solenoid (DC: DC), and is locked as an engaging member 8 at the tip of the plunger 10. The pin 8 is attached.
As a result, when the solenoid 9 is energized, a turn-on current flows through the coil 37 and the plunger 10 is attracted. Then, the lock pin 8 at the tip projects from the solenoid 9 (bobbin) against the return spring 36.
When the energization is stopped, the plunger 10 is pulled by the spring 36, so that the lock pin 8 at the tip of the plunger 10 is accommodated in the solenoid 9 (bobbin).

  The solenoid 9 is accommodated in a protective cover 40 in which a pin hole 39 for slidably supporting the lock pin 8 is formed in the front plate 38, and is supported by the base plate 15 and electrically connected to the housing 14 as shown in FIG. It is arranged between the motors 3.

As described above, the solenoid 9 is disposed between the housing 14 and the electric motor 3 so that the lock pin 8 at the tip of the plunger 10 can advance and retreat with respect to the intermediate gear 41 on the output side of the secondary reduction gear train G2. It has become.
As shown in FIG. 5A, the intermediate gear 41 has a plurality of locking holes 42 provided on the side surface in the same circle shape at equal intervals, and a lock pin with respect to the locking holes 42. 8 is advanced and retracted by the solenoid 9. As shown in FIG. 5B, the intermediate gear 41 is locked by the engagement of the lock pin 8 with the locking hole 42. FIG.5 (b) is bb sectional drawing of Fig.5 (a).
In this embodiment, the plunger 10 is provided with the lock pin as the engagement member 8 at the tip of the plunger 10. However, the plunger 10 and the lock pin 8 may be integrated into the engagement member 8. Further, it is obvious that the plunger 10 itself may be used as the engaging member 8.

As shown in FIG. 6, this electric parking brake device is provided with solenoid displacement detecting means 50.
As shown in the schematic diagram of FIG. 6, the solenoid displacement detecting means 50 is a drive circuit for the solenoid 9 of the parking brake device in which the solenoid 9 and the switch means (here, NPN transistor) 51 are connected in series and connected to the power source 52. 53, a resonance circuit capacitor 54, a displacement detection device 55, a current detection means 56, and a control device 57 are provided.

  Here, the solenoid 9 is composed of the coil 37 and the plunger 10 inserted through the coil 37 as described above. Further, the power source 52 is a DC power source 58 as shown in FIG.

The switch means 51 is a solenoid-driving transistor switch composed of a grounded emitter circuit having an NPN transistor provided between the solenoid 9 and the ground, and is a first switch means 51a for turning on / off the direct current supplied from the power source 52 to the solenoid 9. And the second switch means 51b for applying the alternating current component output from the oscillation means described later to the direct current supplied to the solenoid by the first switch means 51a.
Here, an example in which an NPN transistor is used as the switch means 51 is shown, but a PNP transistor can also be used. In that case, the PNP transistor is disposed between the power supply 52 and the solenoid 9. Further, FET (including MOS type) can be used instead of the transistor.

  The current detection means 56 is composed of, for example, a current detection resistor inserted between the emitter of the transistor of the switch means 51 and the ground, and detects the current flowing through the coil 37 of the solenoid 9 from the potential difference generated by the resistor. Here, a current detection resistor is used for the current detection means 56, but the present invention is not limited to this. In addition to this, a non-contact type DC current sensor (for example, a Hall element type, a mag amplifier type, a magnetic multivibrator type, a flux gate type, an optical element type, etc.) can be used.

As shown in FIG. 6, the resonance circuit capacitor 54 is connected in parallel with the coil 37 of the solenoid 9 to form a resonance circuit (parallel resonance circuit). By adopting such a parallel resonance circuit, the current is canceled out by the phase difference between the coil 37 and the resonance circuit capacitor 54 so that the resonance current does not flow outside the resonance circuit.
It is also possible to omit the capacitor 54 by designing the stray capacitance of the coil 37 of the solenoid 9 to function as the resonance capacitor 54.

The control device 57 is a microcontroller such as an ECU (Engine Control Unit) and includes peripheral circuits such as an oscillation circuit, an A / D converter, an input / output circuit, and a timer circuit.
The detection output of the current detection means 56 is connected to the input of the control device 57. Further, the output of the control device 57 is connected to the transistor of the switch means 51 so as to form a current control loop.
For this reason, the solenoid 9 can be directly driven even by a constant voltage source such as a vehicle battery.
On the other hand, the control device 57 performs on / off control (saturation region) of the solenoid 9 as the first switch means 51a based on the output of the current detection means for opening and closing the switch means 51. At the same time, the control means 57 detects the displacement and position of the plunger 10 and controls the opening degree of the switch means 51 to perform switching in the non-saturated region, thereby causing the drive current as shown in FIG. Apply. Therefore, in this embodiment, the control device 57 generates a switching signal from the output of the internal oscillation circuit using, for example, a prescaler, and inputs it to the switch means 51 as the output of the oscillation means 59.

As shown in FIG. 7, the drive current to the solenoid 9 by the switch means 51 is composed of a direct current portion 60 having only a direct current component and an alternating current portion 61a in which an alternating current component 61 is superimposed on the direct current.
The alternating current component 61 is superimposed at a timing when a direct current is applied to the solenoid 9, the plunger 10 of the solenoid 9 starts to move, and the lock pin 8 at the tip thereof is locked to the speed reduction mechanism 5. The reason why the AC component 61 is applied at such timing to perform superposition is as follows.

  That is, when an AC component 61 is applied (superimposed) to the solenoid 9 where the DC current is applied and the iron core is saturated to detect the position, an electromotive force (self-induction) is generated in the coil 37. This electromotive force lowers the current that can be applied by a constant voltage power source such as an in-vehicle battery. Therefore, when trying to exert a predetermined attractive force, it is necessary to consider an increase in the number of strokes of the solenoid coil 37, use of a permanent magnet, and the like, resulting in a problem that leads to an increase in shape and cost.

  Here, when a constant current is applied to the coil 37 of the solenoid 9, the amount of protrusion of the lock pin 8 (from the protective cover 40), the amount of protrusion (attraction force) of the lock pin 8, the amount of protrusion and the return spring 36. When focusing on the reaction force (tensile tension), there is a correlation shown in FIG. From this, for example, in the case of FIG. 6, the gap g is reduced in proportion to the amount of protrusion of the lock pin 8 and the magnetic resistance of the magnetic path of the coil 37 is monotonously reduced. Increase with quantity.

On the other hand, FIG. 10 shows the correlation between the drive current of the coil 37 of the solenoid 9 and the protruding amount of the lock pin 8 when the above configuration is applied. From this figure, after the projecting output exceeding the tensile tension of the return spring 36 is generated, the projecting output shows an increase amount exceeding the tension as the lock pin 8 projects. Therefore, the lock pin 8 operates as shown by the arrow Y until the protrusion is completed. Next, when the drive current is reduced, the lock pin 8 maintains the protruding state against the tensile tension of the return spring 36 even if the drive current is reduced. When the current I2 decreases to a value that is clearly smaller than that before the current protrudes, the lock pin 8 is pulled by the tension of the return spring 36 and starts to descend as indicated by an arrow Z. And the lock pin 8 will return to the state accommodated in the protective cover 40 before an electric current application.
As can be seen from FIG. 6, in the solenoid 9 that slides to close the gap g in the magnetic circuit, the gap g between the plunger 10 and the fixed iron core 66 increases as the lock pin 8 protrudes. Since it closes, the attractive force per unit current becomes strong.
Therefore, even if the drive current I1 after the protrusion is less than the drive current I1 in FIG. 10, the lock pin 8 is not pulled back by the return spring 36 (residual adsorption force) as long as it is a current value up to the holding current I2.
Therefore, there is a relationship of I1> I2 between the drive current I1 required for the lock pin 9 to start protruding and the holding current I2 holding the protruding lock pin 9, and the AC component If there is a relationship ΔI <I1-I2 between the effective current reduction amount ΔI due to the superposition of 61 and the above I1 and I2, the lock pin 8 is locked regardless of the current reduction due to the superposition of the AC component 61. Can continue.

Therefore, the above problem can be solved by providing a hysteresis in consideration of the current drop due to the operation, for example, by setting the amplitude of the AC component 61 within the current range indicated by Y → Z in the figure. it can.
Incidentally, the adjustment of the amplitude of the AC component 61 is controlled using a constant current loop. Therefore, for example, the control device 57 may be provided with a program for constant current control so that the current can be changed only by setting the current value.
And the timing operation | movement based on such a hysteresis loop is implement | achieved by using the timer means 62 with this form.

Here, the timer means 62 is realized by using the timer circuit of the control device 57. For example, the timer means 62 operates by a program for a time sufficient for the solenoid 9 to operate and the lock pin 8 to be locked to the speed reduction mechanism 5. It can be set according to the environment. By doing so, the timer means 62 starts timing simultaneously with the controller 57 operating the switch means 51 to apply the direct current portion 60 of the drive current to the solenoid 9, and the stroke of the plunger 10 is changed to the lock pin 8. The time is up when the time to reach the length of locking the motor to the speed reduction mechanism 5 elapses. Then, simultaneously with the time-up, the control device 57 operates the switch means 51 to superimpose the AC component 61.
In this embodiment, the timer means 62 used in the control device 57 is used, but is not limited to this. Obviously, the timer means 62 may be provided separately from the control device 57.

In addition to these, a parking switch (not shown) and an ECU (other ECU not shown) are connected to the control device 57, and parking is performed based on an input from the parking switch and the ECU. Controls brake operation.
Further, a displacement detection device 55 is connected to the control device 57, and the operation state of the plunger 10 of the solenoid 9 is estimated as will be described later.

As shown in FIG. 8, the displacement detector 55 includes a filter circuit 63, a rectifier circuit (detection) 64, and an amplifier circuit 65, and is connected to both ends of the solenoid 9. The filter circuit 63 is a band-pass filter whose center frequency is the resonance frequency of the resonance circuit composed of the coil 37 and the resonance capacitor 54, and is also used as a noise countermeasure.
The rectifier circuit 64 includes a smoothing circuit, and outputs a DC voltage level by rectifying and smoothing the filter output. The amplifier circuit 65 is provided to improve detection sensitivity.
Therefore, the displacement detection device functions only when a current including a frequency component is applied.
By the way, a peak hold circuit may be provided instead of the smoothing circuit, and the resonance output may be output as a DC voltage level by resetting at a constant cycle.

Next, the frequency of the AC component 61 superimposed on the AC part 61a will be described. The frequency is for supplying a resonance frequency formed by the coil 37 of the solenoid 9 and the resonance circuit capacitor 54 as a frequency component for position detection.
Therefore, this frequency is set to be equal to or higher than the operating frequency of the solenoid 9, and preferably set sufficiently higher than the operating frequency to facilitate discrimination from the drive current. As a result, the detection time can be shortened. Further, if the frequency is high and the wavelength is short, the resolution of position detection can be improved and the stroke of the plunger 10 of the solenoid 9 can be made smaller.

  Furthermore, at this time, for example, if the resonance frequency is set based on the inductance when the plunger 10 of the solenoid 9 is pulled by the return spring 36 and is outside the coil (bobbin) 37 (outermost point), The position from the outermost point can be estimated using the frequency deviation from the resonance frequency. Therefore, the value of the resonance capacitor 54 is determined according to the optimum frequency.

This configuration is configured as described above, and the frequency and amplitude values of the AC component 61 are set in the control device 57 within the above range.
Thus, the control device 57 applies the drive current I1 shown in FIG. 7 to the solenoid 9 via the switch means 51. Then, simultaneously with the application of the drive current I1, the timer means 62 starts measuring time.
Therefore, the solenoid 9 starts to operate by the direct current portion 60 of the drive current I1, and the lock pin 8 protrudes by attracting the plunger 10 into the coil 37 against the return spring 36. Then, when the timer means 62 expires, the control device 27 determines that the stroke of the plunger 10 has reached the length for locking the lock pin (engagement member) 8 to the speed reduction mechanism 5 and sets the opening of the switch means 53. The AC part 61a shown in FIG. 7 is applied by controlled switching (non-saturation).
When the AC component 61 is applied to the solenoid 9 in this state, the positional relationship of the plunger 10 with respect to the coil 37 (compared to when it is outside (outermost point) of the coil (bobbin) 37) is changed. For this reason, the inductance of the coil 37 also changes.
For this reason, the resonance frequency of the resonance circuit composed of the coil 37 and the resonance capacitor 54 also changes depending on the changed inductance. For example, when the plunger 10 is accommodated in the coil 37 (bobbin), the inductance increases, so that the resonance point ω0 decreases as ω0 → ω0 ′ as shown in FIG. Then, the resonance frequency characteristic moves from (α) to (β).
As a result, the gain at the resonance point ω 0 detected by the displacement detection device 55 decreases, for example, from A to B in FIG. 11, so that the displacement of the plunger 10 can be calculated from the change in gain.

In this way, the maximum current that can be input to the solenoid 9 is applied and the lock pin 8 is protruded, and then the AC component 61 is applied to such an extent that the lock pin 8 does not return. You can check without giving. At that time, since the position of the plunger 10 can be estimated with a minimum decrease in suction force, the position of the plunger 10 estimated when the solenoid 9 is on (switch means 51 is on) and the solenoid 9 are off ( If the position of the plunger 10 estimated when the switch means 51 is off) is stored and the difference is calculated, the displacement of the plunger 10 (the amount of protrusion of the lock pin 8) can be estimated. Furthermore, if the displacement of the plunger 10 can be estimated, it is possible to determine from the estimated value, for example, an engagement state such as whether the lock pin 8 at the tip of the plunger 10 has been locked and whether the lock state has been maintained. .
Thus, the engagement state of the lock pin 8 can be estimated from the position or displacement of the plunger 10 without providing a sensor.
For this reason, it is possible to prevent an accident due to a malfunction of the solenoid. Further, since the detection can be performed without providing a separate sensor, the installation space for the sensor is not required, so that the coil 37 of the solenoid 9 can be reduced in size and the cost can be reduced.
In addition, when the engagement state is poor, for example, by giving an alarm or the like, an accident due to a malfunction of the solenoid 9 can be prevented.
In addition, since the oscillation output is superimposed in this way, the problem of noise as in the case of switching between the direct current and the alternating voltage does not occur. Furthermore, since the oscillation output is superimposed on the direct current and the change in the detection value at both ends of the solenoid coil 37 (change in the resonance point) is detected, the oscillation output does not require a large amount of power and the loss is small.

The first embodiment relates to the temperature rise of the solenoid 9 in addition to the above-described effects, and describes that the accuracy in estimating the position and displacement of the plunger 10 can be improved by compensating for the decrease in the magnetic field due to the temperature rise. .
That is, the solenoid 9 uses a copper wire for the coil 37. This copper wire has a DC resistance, and the DC resistance has a positive temperature coefficient. Therefore, when the DC resistance of the coil 37 increases due to the temperature rise (including the ambient temperature), the excitation current decreases and the magnetomotive force decreases.
Here, in the thing of FIG. 6, since the current control loop is used for the drive of the solenoid 9, it is thought that it controls to supply a fixed electric current, even if temperature changes.
However, in general, when the relationship between the DC resistance of the coil 37 and the temperature coefficient is normalized with 20 ° C. being 1, the resistance ratio and current ratio at each temperature of the copper wire is, for example, the attraction force of the coil at 100 ° C. It is said that it changes greatly to about 56% of the 20 ° C coil. For this reason, since an error may occur in the control, the estimation accuracy is improved by calibrating based on the temperature of the coil 37 when the position of the plunger 10 is calculated and estimated.

Therefore, in the first embodiment, before the parking brake operation, the control device 57 measures the voltage by supplying a current for measurement that does not cause the displacement of the lock pin 8 to the solenoid 9, and determines the coil from the measurement result of the current and the voltage. The resistance value of 37 is calculated, and the temperature is calculated from the resistance value. Then, the position of the plunger 10 is estimated by taking into account the decrease in the magnetic field based on the temperature.
For example, as shown by a broken line 67 in FIG. 6, the A / D conversion input of the control device 57 is connected to the terminal of the solenoid 9 to measure the voltage. The control device 57 drives the transistor of the switch means 51 in a non-saturated manner and inputs a measurement current (a current value at which the plunger 10 of the solenoid 9 does not cause a displacement) to the coil 37.

In the parking brake device of the first embodiment configured as described above, the temperature of the coil 37 is detected by, for example, a well-known resistance method using a resistance temperature coefficient of copper.
That is, the resistance method calculation formula is
R2 / R1 = (234.5 + t1) / (234.5 + t2)
From the above equation, the temperature t2 after energization is
t2 = R2 / R1 (234.5 + t1) −234.5
It becomes.
Here, t1: temperature before energization (ambient temperature) (° C.), t2: temperature after energization (° C.),
R1: Resistance before energization (normal temperature value) (Ω), R2: Resistance after energization (Ω)
It is.
In this way, since the temperature of the coil 37 can be estimated, a reduction amount of the current flowing through the coil 37 can be calculated based on the estimated temperature.
Therefore, the estimated position of the plunger 10 during the parking brake operation is calibrated by predicting a decrease in magnetomotive force from the amount of decrease in the current. By doing so, the accuracy in estimating the position of the plunger 10 can be improved.
Therefore, since the operation failure of the plunger 10 can be detected more precisely by improving the accuracy, an accident due to the operation failure can be prevented in advance.

In the second embodiment, in addition to the above-described effects, the state of the parking brake device is periodically checked (checked) to improve safety.
That is, the position of the plunger 10 of the solenoid 9 is estimated and confirmed when the parking brake device is off and when the parking brake device is operating.

The case where the parking brake device is off is when the service brake (foot brake) is being operated by operating the brake pedal, and the lock pin 8 engages the intermediate gear 41 so that the operation of the service brake is not hindered. It is confirmed whether or not it is separated from the hole 42. Therefore, this confirmation is always performed by estimating the position of the plunger 10 of the solenoid 9 sequentially at regular intervals shorter than the operation period of the solenoid 9 using the method of the embodiment and the first example. By doing so, a malfunction is detected.
In this embodiment, as shown in FIG. 6, it is estimated and confirmed that the plunger 10 is in a position pulled out from the coil 37 (bobbin) by the return spring 36. As a result, when the lock pin 8 is not separated, the safety is ensured by notifying the failure by, for example, issuing an alarm.

On the other hand, when the parking brake device is in operation, the service brake is released during parking or stopping, and it is confirmed whether or not the lock pin 8 is fitted in the locking hole 43 of the intermediate gear 41. This confirmation is also always performed by estimating the position of the plunger 10 of the solenoid 9 sequentially at regular intervals shorter than the operation cycle of the solenoid 9 by using the method of the embodiment and Example 1. And it confirms by estimating the position of the plunger 10 of the solenoid 9. FIG. In this way, malfunction can be detected.
In this form, it is estimated and confirmed that the plunger 10 is in a position attracted into the coil 37 (bobbin) against the return spring 36. And when it is detected that the lock pin 8 is not fitted in the locking hole 43 of the intermediate gear 41, for example, an alarm is issued to ensure safety.
By confirming in this way, it is possible to prevent the vehicle from becoming unbraking due to malfunction.
Incidentally, this confirmation is performed intermittently at regular intervals because the power consumption for the estimation process can be reduced by performing the estimation process intermittently.

  In the embodiment, the switch means 51 has been described as the first switch means 51a and the second switch means 51b. For example, as shown in FIG. 12, the first switch means 51a and the second switch means 51b are It may be provided in series. In this case, the second switch means 51a is normally turned on to perform switching (non-saturation) when an AC component is applied.

  In the embodiment and Examples 1 and 2, the pin driving solenoid 9 uses a push-type actuator, but is not limited thereto. It is also possible to use a pull type actuator by devising a circuit.

In the embodiment and Examples 1 and 2, the oscillation unit 59 and the timer unit 62 are configured using the function of the control device 57, but the present invention is not limited to this. Obviously, the oscillating means 59 and the timer means 62 can be provided as separate circuits from the control device 57.

DESCRIPTION OF SYMBOLS 1 Electric brake 2 Parking means 3 Electric motor 4 Linear motion mechanism 5 Deceleration mechanism 6 Brake pad 7 Rotor 8 Lock pin 9 Solenoid 10 Plunger 37 Coil 50 Solenoid displacement detection means 51 Switch means 51a First switch means 51b Second switch Means 52 Power supply 54 Resonance capacitor 55 Displacement detection device 56 Current detection means 58 DC power supply 59 Oscillation means 62 Timer means 63 Filter circuit 64 Rectifier circuit 65 Amplifier circuit 66 Fixed iron core g Gap

Claims (9)

Friction that is attached to an electric motor, a linear motion mechanism, a speed reduction mechanism that connects the electric motor and the linear motion mechanism, and a linear motion mechanism that is driven via the speed reduction mechanism by the rotation of the electric motor and is pressed against the brake rotor In an electric parking brake device constituted by an electric brake constituted by a member, and a parking means for engaging and locking the engaging member to the deceleration mechanism by the operation of a plunger of a DC solenoid,
A power supply means for supplying a direct current to the solenoid, an oscillating means for outputting an alternating current component superimposed on the direct current supplied by the power supply means, and a first for turning on / off the direct current supplied from the power supply means to the solenoid Switch means; and second switch means for applying an alternating current component output from the oscillating means to the direct current supplied to the solenoid by the first switch means at a timing when the engaging member is locked to the speed reduction mechanism; An electric parking brake device comprising processing means for estimating a position or displacement of a solenoid plunger from a change in detection values at both ends of a solenoid coil to which an AC component is applied.   The solenoid is provided with an elastic mechanism for restoring the plunger to the starting position, the driving current of the solenoid is I1, and the holding current for holding the plunger after the activation against the elastic mechanism is I2 ( 2. The electric parking brake device according to claim 1, wherein I1> I2), and ΔI <I1-I2 where ΔI is the amount of decrease in effective current after application of the oscillation means output.   The electric parking brake device according to claim 1 or 2, further comprising timer means for operating the second switch means after time-up at a timing when the engaging member is locked to the speed reduction mechanism.   The electric parking brake device according to any one of claims 1 to 3, wherein the frequency of the AC component applied to the solenoid is at least equal to or higher than the operating frequency of the solenoid.   5. The electric parking brake device according to claim 1, wherein the amount of protrusion of the engaging member is estimated from a difference in movement of the plunger before and after the operation of the solenoid.   Prior to the operation of the parking means, a current for measurement in which the plunger does not move is input to the solenoid, the temperature of the coil is calculated based on the measured value at that time, and the engagement member is calculated based on the calculated temperature of the coil. The electric parking brake device according to any one of claims 1 to 5, wherein the estimated position is calibrated.   When the electric brake is in operation and the parking means is not in operation, the position of the solenoid plunger is calculated at regular intervals, and it is confirmed from the calculated position that the engagement member is kept away from the speed reduction mechanism. The electric parking brake device according to any one of claims 1 to 6, wherein:   While the electric brake is not operating and the parking means is operating, the position of the plunger of the solenoid is calculated at regular intervals, and the engaged state of the engaging member with the speed reduction mechanism is maintained from the calculated position. The electric parking brake device according to any one of claims 1 to 7, wherein the electric parking brake device is confirmed.   9. The electric parking brake device according to claim 1, wherein the first switch means also serves as the second switch means.

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