WO2011030839A1 - Electric disc brake - Google Patents

Abstract

Disclosed is an electric disc brake that is low-cost and furthermore capable of maintaining superior resistance to weather. All of a shaft force sensor (8b) for measuring braking force is formed in the shape of a ring. The shaft force sensor (8b) is disposed around a rotating shaft that is rotationally driven by an electric motor and acts as the input unit of a force-increasing mechanism. The aforementioned shaft force sensor (8b) is equipped with one pair of pressing plates (47a, 47b) that are each formed in a ring shape and are disposed mutually parallel, a plurality of piezoelectric crystal elements (48, 48) that are sandwiched between both pressing plates (47a, 47b), and a lead wire (50) for extracting an electric charge generated with the pressing of each piezoelectric crystal element (48, 48) between both pressing plates (47a, 47b). Additionally, the lead wire (50) is pulled out to the outer diameter side of both aforementioned pressing plates (47a, 47b).

Description

Electric disc brake

The present invention relates to an improvement of an electric disc brake that brakes an automobile by an electric actuator using an electric motor as a drive source. Specifically, in order to stably obtain a desired braking force, a low-cost structure can be used as an axial force sensor for measuring the thrust applied to a pair of pads by the electric actuator with high accuracy. It is intended to realize.

Electric disc brakes that use an electric motor as a drive source eliminate the need for piping compared to the hydraulic disc brakes that have been widely used in the past, making manufacturing easier and lowering costs. There are many advantages such as reduced brake load and less environmental load, and improved response due to the absence of brake fluid movement. As such an electric disc brake, the output of the electric motor is input to a force-increasing mechanism, and this force-increasing mechanism converts the rotary motion of this electric motor into a linear motion while increasing the force, and a pair of pads is placed on both sides of the rotor. Various types of structures that are strongly pressed have been proposed, for example, as described in Patent Documents 1 to 6.

As the force increasing mechanism, various mechanisms such as a feed screw mechanism, a cam mechanism, a link mechanism, and a combination thereof are known. In any mechanism, even if there is a difference in degree, loss due to friction is unavoidable, and all the output of the electric motor is directly applied to the force (pressing force) that presses the pad against the rotor. Must not. Further, even if the energization amount to the electric motor is the same and the drive torque of the output shaft of the electric motor is the same, the energization amount is increased and decreased based on the hysteresis in the booster mechanism. In some cases, a difference occurs in the pressing force. Moreover, the degree of this difference and the degree of the loss change due to friction of each part and are not constant. Therefore, in order to obtain a desired braking force accurately and stably, it is not sufficient to control the amount of power supplied to the electric motor. The pressing force is measured, and the electric power is measured based on the measured value. It is necessary to perform feedback control to control the amount of current supplied to the motor.

For this reason, conventionally, as described in Patent Documents 1 to 5, etc., an axial force sensor is provided at a portion to which the pressing force is applied, and the pressing force is measured by the axial force sensor. FIG. 27 shows the structure described in Patent Document 5 among them. In the case of this conventional structure, the rotary motion of the electric motor 1 is converted into a linear motion by the booster mechanism 2 and transmitted to the piston 3, and the outer and inner pads 5, 6 are connected to the wheel by the piston 3 and the caliper claw 4. At the same time, it is pressed against both side surfaces of the rotor 7 rotating together. Further, an axial force sensor 8 is provided between the piston 3 and the inner pad 6, and the axial force sensor 8 can measure the force pressing the inner pad 6 against the rotor 7.

In order to control the braking force with high accuracy, it is necessary to use an axial force sensor 8 with high accuracy and small hysteresis as described above. If an axial force sensor 8 having a large hysteresis is used, even if the pressing force value is the same, the difference between the increase process and the decrease process is not negligible. Accuracy deteriorates. In view of such circumstances, it is preferable to use a sensor incorporating a quartz crystal piezoelectric element as an axial force sensor incorporated in an electric disc brake. Since the quartz piezoelectric element has higher accuracy and lower hysteresis than the ceramic piezoelectric element, it is possible to control the pressing force of the electric disc brake while ensuring practical accuracy. As an axial force sensor using such a crystal piezoelectric element, for example, the one described in Non-Patent Document 1 can be used.

However, if a structure having a structure as shown in FIG. 27 and incorporating a crystal piezoelectric element as the axial force sensor 8 is used, the following problems (1) to (3) occur.
(1) It is necessary to use a crystal piezoelectric element having a large shape and an expensive element, which increases the manufacturing cost of the axial force sensor 8, and further increases the cost of an electric disc brake incorporating the axial force sensor 8. .
(2) Since the axial force sensor 8 is disposed in series between the piston 3 and the inner pad 6 in the axial direction, the inner pad 6 and the outer pad 5 are exchanged due to lining wear or the like. At this time, the axial force sensor 8 may be detached from the piston 3, and care must be taken in replacing the pads 5 and 6.
(3) Since the axial force sensor 8 is exposed to the external space, it is necessary to devise the case constituting the axial force sensor 8 and its seal structure in order to provide sufficient weather resistance. Cost increases.

Among the problems (1) to (3) above, the problem (1) is to use a plurality of small piezoelectric elements instead of one large one as the quartz crystal element constituting the axial force sensor. It can be solved by doing. For example, the price of an annular crystal piezoelectric element having an outer diameter of about 2 to 4 cm and a radial width of about 4 to 6 mm, which is incorporated in an electric disc brake subject to the present invention, is very expensive. It is. On the other hand, the price of a small piece of a quartz crystal piezoelectric element having a diameter of about 4 to 6 mm is extremely low. Therefore, if an axial force sensor having a structure in which small pieces of crystal piezoelectric elements are arranged in an annular shape and the small pieces are pressed between a pair of pressing surfaces, an axial force sensor with high accuracy and low hysteresis can be obtained. Obtained at low cost.

As such an axial force sensor, the one shown in FIGS. 28 to 29 described in Patent Document 7 is known. The axial force sensor 8a holds the crystal piezoelectric elements 11 in holding recesses 10 and 10 formed at a plurality of locations in the circumferential direction on one axial surface of a holding body 9 configured in an annular shape (annular shape). The openings of the holding recesses 10 and 10 are closed by the cover plates 12 and 12. A charge amplifier 13 is disposed on the inner diameter side of the holding body 9, and an input portion of the charge amplifier 13 and an output portion of each crystal piezoelectric element 11 are connected. Since the axial force sensor 8a described in Patent Document 7 uses a small piece that can be procured at a low cost as the crystal piezoelectric element 11, the cost of the axial force sensor 8a as a whole can be suppressed.

However, the axial force sensor 8a having the conventional structure described in Patent Document 7 as described above is designed to be held between the butting surfaces of the boring machine between the drive shaft and the tool carrying shaft. . When such an axial force sensor 8a described in Patent Document 7 is used for measuring the braking force of an electric disc brake, the problem (1) can be solved among the problems (1) to (3) described above. However, the remaining problems (2) and (3) cannot be solved. That is, since the axial force sensor 8a having the conventional structure has the charge amplifier 13 disposed at the center portion, an electric disk brake such as a screw rod is formed at the center portion of the axial force sensor 8a to perform rotational motion. A member that increases force while converting to linear motion cannot be inserted. For this reason, the installation position in application to an electric disc brake is limited, and the problems (2) and (3) cannot be solved.
Note that there is Patent Document 8 as a publication describing the technology related to the present invention. This Patent Document 8 describes a structure that prevents damage such as cracking or chipping on the pressure receiving plate by chamfering the corners of the ceramic pressure receiving plate constituting the load sensor. . However, Patent Document 8 does not include a description suggesting that the problems (2) and (3) are solved.

Japanese Laid-Open Patent Publication No. 8-244580 Japanese Patent Laid-Open No. 11-147458 Japanese Unexamined Patent Publication No. 2000-213575 Japanese Unexamined Patent Publication No. 2004-60867 Japanese Unexamined Patent Publication No. 2006-232259 Japanese Unexamined Patent Publication No. 2004-169729 Japanese Laid-Open Patent Publication No. 4-231829 Japanese Unexamined Patent Publication No. 2003-139629

The present invention was invented to realize an electric disc brake capable of ensuring low cost and excellent pad replacement workability and weather resistance in view of the circumstances as described above.

The electric disc brake of the present invention includes a rotor, a torque receiving member, a pair of pads on the outer side and the inner side, and an actuator, as in the case of conventionally known electric disc brakes.
Of these, the rotor rotates with the wheels.
The torque receiving member is supported by the vehicle body in a state adjacent to the rotor. As the torque receiving member, the support of the floating caliper type disc brake corresponds to the caliper of the opposed piston type disc brake.
In addition, the two pads have the rotor sandwiched from both sides in the axial direction (the axial direction is the axial direction of the rotor unless otherwise specified. The same applies throughout the present specification and claims) The torque receiving member is supported so as to be capable of axial displacement.
Furthermore, the actuator is for pressing both pads against both side surfaces of the rotor, and converts the electric motor and the rotational driving force of the electric motor into axial thrust and transmits it to the inner pad. A force-increasing mechanism and an axial force sensor that measures the pressing force applied from the force-increasing mechanism to the inner pad are provided.
In the case of a floating caliper disc brake, a caliper is provided in addition to the support that is the torque receiving member. This caliper has a caliper claw facing the outer side surface of the outer side pad at the outer side end, and presses the inner side pad toward the inner side surface of the rotor in a storage space provided inside the inner side portion. The actuators are respectively provided and supported so as to be capable of axial displacement with respect to the support. The outer side pad of the two pads is pressed against the outer side surface of the rotor via the caliper by the actuator.

In particular, in the electric disc brake of the present invention, the axial force sensor is formed in an annular shape as a whole, and is rotationally driven by the electric motor and serves as an input portion of the force increasing mechanism. It is arranged around.
The axial force sensor includes a pair of pressing plates each configured in an annular shape and arranged in parallel to each other, a plurality of quartz piezoelectric elements sandwiched between the pressing plates, and both the pressing plates. And a lead wire for taking out electric charges generated when the quartz piezoelectric elements are pressed between the plates.
And this lead wire is taken out to the outer diameter side of the said both press plates.

When implementing the electric disc brake of the present invention as described above, an outward flange-like flange is preferably fixed to the outer peripheral surface of the intermediate portion of the rotating shaft. Then, the thrust rolling bearing and the axial force sensor are sandwiched in this order from the side of the flange between the inner side surface of the flange and the inner side rear end surface of the storage space in which the actuator is stored.

Further, when carrying out such an invention, it is preferable that the thrust rolling bearing and the flange portion are provided with an inner side case provided in a portion including the inner side of the thrust rolling bearing, and an outer side than the flange portion. It is accommodated in a case unit including an outer side case that is provided in a portion including the side and is non-separated with the inner side case. Then, the thrust rolling bearing is elastically pressed against the inner side case where the axial force sensor is installed by an elastic member provided between the inner side surface of the outer side case and the outer side surface of the flange portion. .

Further, when the present invention is carried out, both the pressing plates are made of metal. Then, one end face of both end faces in the axial direction of each crystal piezoelectric element is electrically connected to one pressing plate serving as a ground electrode, and the other end face is connected to the other through an insulating plate capable of supporting the pressing force. Butt against the pressing plate. Further, the other end faces of the crystal piezoelectric elements are made conductive by a conductor disposed between the insulating plate and the other end face of the crystal piezoelectric elements, and one end of the lead wire is connected to the conductor.

Alternatively, both the pressing plates are made of metal. Each of the quartz piezoelectric elements is configured by sandwiching an electrode between a pair of quartz piezoelectric element pieces, and a plurality of these quartz piezoelectric elements are sandwiched between the pressing plates. Further, of the both end surfaces in the axial direction of each of the crystal piezoelectric element pieces, the surface opposite to the electrode is electrically connected to the pressing plates, each serving as a ground electrode, and the other end surface is connected via the electrode. Connect to one end of the lead wire.

Alternatively, both the pressing plates are made of metal. In addition, an energization plate is provided between the side surfaces of the two pressing plates facing each other. Further, a plurality of each of the piezoelectric piezoelectric elements is provided between the both side surfaces in the axial direction of the energizing plate and the side surfaces of the both pressing plates. Then, one end face of both end faces in the axial direction of each crystal piezoelectric element is made conductive with the energizing plate, and the other end face is made electrically connected with any one of the pressing plates. Furthermore, the end portions of the lead wires are connected to both of the pressing plates and the energizing plate, respectively.

In carrying out the present invention, a plurality of holding recesses are provided on a surface of at least one of the pressing plates facing the counterpart pressing plate, and each of the quartz piezoelectric elements is provided in each holding recess. The axial end of the element is fitted inside.
Alternatively, the opposing surfaces of the two pressing plates are flat surfaces. Further, an annular holding ring having holding holes formed at a plurality of locations in the circumferential direction is disposed between the two pressing plates. And the axial direction intermediate part of each said quartz crystal piezoelectric element is internally fitted in each of these holding holes.

Further, when carrying out the present invention, one of the two pressing plates is a nut plate having a screw hole formed at the center, and the other pressing plate is formed with a circular through hole at the center. It shall be formed. Then, an outward flange-shaped flange portion is inserted into one axial end portion of the outer peripheral surface, a male screw portion is also inserted into the portion closer to the other end, and a cylindrical coupling screw provided is inserted into the through hole from the other axial end side. Further, the male screw portion and the screw hole are screwed together, and the flange portion is engaged with the inner peripheral edge portion of the side surface on the opposite side to the one pressing plate among the two axial side surfaces of the other pressing plate. Combine.
Further, when the present invention is carried out, it is preferable to chamfer the corners of the crystal piezoelectric elements.
In this case, more preferably, of the axially opposite end faces of each of the crystal piezoelectric elements, the entire portion present inside the chamfer is such that the both pressing plates sandwiching the crystal piezoelectric elements are thrust loads. The dimension of each part is regulated so that it exists inside in the radial direction of the axial force sensor with respect to the outer peripheral edge of the receiving range.

According to the present invention configured as described above, it is possible to realize an electric disc brake capable of ensuring excellent pad replacement workability and weather resistance at low cost.
First, cost reduction can be achieved by configuring the axial force sensor by sandwiching a plurality of crystal piezoelectric elements between a pair of pressing plates. As described above, when an axial force sensor is made of a relatively large single crystal piezoelectric element, the procurement cost of the crystal piezoelectric element increases. However, a single axial force sensor is configured by gathering a plurality of axial force sensors. A relatively small crystal piezoelectric element can be obtained at a much lower cost. For this reason, the cost of the electric disc brake incorporating this axial force sensor can be reduced.

In addition, the excellent pad replacement workability and weather resistance are such that the entire axial force sensor is formed in an annular shape, and a lead wire for taking out electric charges is taken out to the outer diameter side. This can be achieved by arranging it around the rotation shaft that serves as the input unit. In other words, this axial force sensor is arranged around this rotating shaft, and further, if necessary, supported inside a component component of a disc brake such as a caliper while being held in the case unit. This axial force sensor can be prevented from falling, and the pad replacement workability can be improved. The rotating shaft is present in a space inside a component member of a disc brake such as a caliper, which is separated from an external space in which foreign matter exists. For this reason, by devising the structure of the axial force sensor, if this axial force sensor is arranged around the rotating shaft, foreign matter such as muddy water can be prevented from adhering to the axial force sensor. The weather resistance of the electric disc brake incorporating the axial force sensor can be improved.

The electric disc brake showing the first example of the embodiment of the present invention, the lower part corresponding to the a-a cross section of FIG. FIG. FIG. 2 is a cross-sectional view taken along the line cc of FIG. 3 (A) and 3 (B) are cross-sectional views showing a unit in which the force-increasing mechanism and the axial force sensor are combined. FIG. It is sectional drawing shown in the state assembled | attached to FIG. 3, FIG. 3 (B) is sectional drawing shown in the state before assembling. Sectional drawing which takes out and shows an axial force sensor. The exploded perspective view of an axial force sensor. The perspective view which takes out and shows one crystal piezoelectric element. 7A and 7B are perspective views showing an insulating plate with a conductor coated on one side, and FIG. 7A shows a surface without a conductor coated with an insulating plate coated with a conductor on one side. FIG. 7B shows a state where an insulating plate having a conductor coated on one side is viewed from the surface coated with the conductor. The principal part disassembled perspective view of the axial force sensor which shows the 2nd example of embodiment of this invention. The principal part perspective view of the axial force sensor which shows the 3rd example. The perspective view which takes out and shows one crystal | crystallization piezoelectric element of an axial force sensor. Sectional drawing of the axial force sensor which shows the 4th example of embodiment of this invention. The exploded perspective view of an axial force sensor. The perspective view which takes out and shows one crystal | crystallization piezoelectric element of an axial force sensor. Sectional drawing of the axial force sensor which shows the 5th example of embodiment of this invention. The perspective view which takes out and shows one crystal | crystallization piezoelectric element of an axial force sensor. The perspective view of the axial force sensor which shows the 6th example of embodiment of this invention. The end view of an axial force sensor. Dd sectional drawing of FIG. The exploded perspective view of an axial force sensor. The perspective view of the axial force sensor which shows the 7th example of embodiment of this invention. The end view of an axial force sensor. Ee sectional drawing of FIG. The exploded perspective view of an axial force sensor. FIGS. 24A, 24B, 24C, and 24D are diagrams showing four examples of crystal piezoelectric elements each having a chamfered corner, and FIG. 24A shows an example thereof. FIG. 24B is a perspective view and a side view showing another example, and FIG. 24C is a perspective view and a side view showing another example, and FIG. (D) is the perspective view and side view which show another example. 25 (A), (B) and (C) are diagrams showing three examples of the state in which the conductor is attached to the disc-shaped crystal piezoelectric element, and FIGS. 25 (A) and (C) are perspective views. FIG. 25B is a side view. 26 (A), (B) and (C) are diagrams showing three examples of the state of attachment of a conductor to a quadrangular plate-like crystal piezoelectric element, and FIGS. 26 (A) and (C) are perspective views. FIG. 26B is a side view. Sectional drawing which shows an example of a conventional structure. The end view which shows an example of the axial force sensor conventionally known. FIG. 29 is an enlarged ff sectional view of FIG. 28.

[First example of embodiment]
1 to 7A and 7B show a first example of the embodiment of the present invention. First, the structure of the entire electric disc brake will be described with reference to FIGS. In the case of the structure of this example, a floating caliper type disc brake is a target. A measuring unit including a force-increasing mechanism 2a driven by an electric motor 1a and an axial force sensor 8b to which preload is applied is provided as a caliper 14. Can be easily assembled. A structure that supports the caliper 14 so as to be capable of axial displacement with respect to a support (not shown) corresponding to the torque receiving member described in the claims includes a floating caliper type widely known in the art including a hydraulic type. It is the same as a disc brake. Further, during braking, the function and the like for extending the force-increasing mechanism 2a and pressing the outer and inner pads 5a, 6a against both side surfaces of the rotor 7a, including the structure shown in FIG. It is the same as a known electric disc brake. The structure of the force-increasing mechanism 2a shown in FIG. 1 is basically the same as the conventional structure described in Patent Document 6. However, when the present invention is implemented, the force-increasing mechanism 2a is not limited to the structure in which the feed screw mechanism 15 and the ball / ramp mechanism 16 are combined as shown in the figure, but includes a cam / roller mechanism, a feed screw mechanism, etc. Various mechanical force-increasing mechanisms that convert force into force while increasing force can be used.

In the case of this example, the base end of the drive spindle 19 is configured by constituting the force-increasing mechanism 2a and having the front half (outer side half) screwed into the screw hole 18 provided in the center of the drive side rotor 17. The portion is spline-engaged with the central portion of the reduction large gear 21 constituting the reduction gear 20. Further, an outward flange-like flange portion 22 is formed at an axially intermediate portion of the drive spindle 19, and an inner side surface of the flange portion 22 is supported by a thrust rolling bearing 23. With this configuration, the drive spindle 19 can be rotationally driven while supporting a thrust load directed toward the inner side.

The flange portion 22 and the thrust rolling bearing 23 are housed in a case unit 25 together with the axial force sensor 8b and an elastic member 24 that is elastically deformable in the axial direction, such as a wave plate spring, a compression coil spring, and rubber. is doing. The case unit 25 is formed by combining an inner side case 26 and an outer side case 27. The case unit 25 is formed by combining the inner and outer cases 26 and 27 in a non-separable manner so as to allow a slight relative displacement in the axial direction.

Among these, the inner side case 26 is provided with a cylindrical fixed side peripheral wall portion 30 from the outer peripheral edge of the annular bottom plate portion 29 having a circular through hole 28 in the center portion toward the outer side. An extraction hole 32 for exposing an end portion of the connector 31 for extracting the measurement signal of the axial force sensor 8b is formed at one position in the circumferential direction of the proximal half wall portion (inner wall portion) of the fixed side peripheral wall portion 30. is doing. In addition, the engagement holes 33 that are long in the axial direction are arranged at a plurality of circumferential positions (for example, two to three positions at equal intervals in the circumferential direction) of the first half portion (outer portion) of the fixed-side peripheral wall portion 30. , 33 are formed. The structure for exposing the end portion of the connector 31 may be a notch that opens at the front end edge (outer side end edge) of the fixed peripheral wall portion 30 instead of the extraction hole 32. However, in this case, the phase in the circumferential direction between the notch and each of the engagement holes 33 and 33 is shifted (a notch is provided between the engagement holes 33 and 33 adjacent to each other in the circumferential direction). ).

On the other hand, the outer side case 27 is provided with a cylindrical displacement side peripheral wall portion 36 from the outer peripheral edge of the annular bottom plate portion 35 having a circular through hole 34 in the center portion toward the inner side. A tongue piece projecting toward the inner side is formed at a portion aligned with the engagement holes 33 and 33 at a plurality of positions in the circumferential direction of the distal end edge (inner side end edge) of the displacement side peripheral wall portion 36. Yes. In a state in which the case unit 25 is configured by combining the inner side and outer side cases 26, 27, the tongue pieces are bent radially inward of the case unit 25 to form engagement pieces 37, 37. The engagement pieces 37 and 37 are engaged with the engagement holes 33 and 33 so as to be axially displaceable. In this state, the axial dimension of the case unit 25 can be expanded and contracted within a range in which the engagement pieces 37 and 37 can be displaced in the engagement holes 33 and 33.

Further, at a plurality of locations in the circumferential direction of the displacement side peripheral wall portion 36 (for example, at two or three positions at equal intervals in the circumferential direction), the outer circumferential surface of the displacement side peripheral wall portion 36 is radially outward. The locking pieces 38 and 38 are formed so as to protrude in a protruding state. Each of the locking pieces 38, 38 is formed by bending a part of a metal plate constituting the displacement side peripheral wall portion 36 of the outer side case 27 outward in the radial direction of the outer side case 27. A direction in which the outer diameter side portion is a locking edge for engaging an outer side edge of the outer diameter side portion with a locking recess 39 described later, that is, the outer periphery of the displacement side peripheral wall portion 36 toward the outer side. It is inclined in the direction in which the amount of protrusion from the surface increases.

In such a case unit 25, the flange portion 22 provided at the intermediate portion of the drive spindle 19, the axial force sensor 8b, the thrust rolling bearing 23, and the elastic member 24 are incorporated. In this assembling operation, first, the axial force sensor 8b is inserted into the inner case 26, and then the drive spindle 19, the thrust rolling bearing 23, and the elastic member 24 are connected to the inner case 26. Insert into. Furthermore, the distal end portion (inner side end portion) of the displacement side peripheral wall portion 36 of the outer side case 27 is externally fitted to the front end portion (outer side end portion) of the fixed side peripheral wall portion 30 of the inner side case 26, and The engagement pieces 37, 37 and the engagement holes 33, 33 are engaged with each other. In this state, as shown in FIG. 3B, the member or each part 19, 22, 8b, 23, 24 is incorporated (subassembled) into the case unit 25, and the axial force measuring unit 40 is assembled. Can be obtained. In this state, the axial force sensor 8b is not necessarily given a sufficient preload to ensure measurement accuracy.

As shown in FIG. 1, the axial force measuring unit 40 as described above is assembled to the inner end of the cylinder space 41 provided in the inner side portion of the caliper 14. The inner diameter of the rear end portion of the cylinder space 41 is substantially the same as the outer diameter of the fixed peripheral wall portion 30 of the inner case 26, and the inner case 26 is rattled to the rear end portion of the cylinder space 41. It can be held without any loss. However, a concave groove 42 that opens to the inner diameter side and the outer side of the cylinder space 41 is formed in a portion of the rear end portion that is aligned with the end portion of the connector 31. To prevent interference. Further, the locking recess 39 is formed in a portion of the cylinder space 41 near the back end of the intermediate portion, except for the recessed groove 42 portion, over substantially the entire circumference. The outer side end of the locking recess 39 is a stepped surface 43 that exists in a direction perpendicular to the central axis of the cylinder space 41.

In order to assemble the axial force measurement unit 40 to the inner end of the cylinder space 41, the case unit 25 is pushed into the cylinder space 41 while the elastic member 24 is compressed in the axial direction. With the pushing operation, the locking pieces 38 and 38 are elastically deformed radially inward of the case unit 25 and pass through the outer side or the intermediate portion of the cylinder space 41. The inner side case 26 is fitted into the inner end of the cylinder space 41, and the outer side case 27 is moved until the locking pieces 38 and 38 are positioned on the inner diameter side of the locking recess 39. Push into the cylinder space 41. Then, each of the locking pieces 38, 38 elastically protrudes from the outer peripheral surface of the displacement side peripheral wall portion 36 and enters the locking recess 39. In this state, when the force that pushes the case unit 25 into the cylinder space 41 is released, the leading edges of the locking pieces 38 and 38 abut against the step surface 43 by the elastic force of the elastic member 24, and the outer The side case 27 will not be displaced in the direction (outer side) of exiting from the cylinder space 41. In this state, a sufficient preload is applied to the axial force sensor 8b in order to ensure measurement accuracy. Therefore, a plug 46 provided at the end of the harness 45 is inserted into the cylinder space 41 through the connection hole 44 formed in the caliper 14, and the plug 46 and the connector 31 are connected to each other, and the axial force sensor 8b. The measurement signal can be extracted.

The operation of assembling the axial force measurement unit 40 can be performed in a large space outside the cylinder space 41. The operation of assembling the axial force measurement unit 40 in the cylinder space 41 is simply performed by the connector 31 and the concave groove 42. Can be easily performed by simply pushing the axial force measuring unit 40 into the cylinder space 41. Further, the operation of assembling the drive-side rotor 17 constituting the ball / ramp mechanism 16 on the outer side of the axial force measuring unit 40 is performed by a portion protruding from the inner-side end surface of the caliper 14 at the inner-side end portion of the drive spindle 19. By rotating the drive side rotor 17 to the outer side portion of the drive spindle 19, the drive side rotor 17 can be easily engaged. The operation of assembling other members can be easily performed by inserting the cylinder space 41 into the cylinder space 41 from the outer side opening. When the axial force measuring unit 40 is assembled in the cylinder space 41, an appropriate preload is applied to the axial force sensor 8b, and the axial force applied to the axial force sensor 8b along with braking is reduced. The relationship with the measurement signal of the axial force sensor 8b can be made almost linear. For this reason, even if the configuration of the arithmetic unit for processing the measurement signal is simplified, the axial force can be obtained with sufficient accuracy.

The overall structure of the electric disc brake of this example is as described above. The axial force sensor 8b constituting the axial force measuring unit 40 is configured as shown in FIGS. 4 to 7 (A) and (B). It is composed. That is, the axial force sensor 8b is arranged around an inner portion of the drive spindle 19 that is a rotating shaft that serves as an input portion of the force-increasing mechanism 2a by forming an annular shape as a whole. . For this purpose, the axial force sensor 8b includes a pair of pressing plates 47a and 47b, a plurality of crystal piezoelectric elements 48 and 48, an insulating plate 49, and a lead wire 50. Of these, the pressing plates 47a and 47b are each formed in an annular shape, arranged in parallel with each other and concentrically with each other. Each of the quartz crystal piezoelectric elements 48 and 48 is formed in a columnar shape, covers both ends in the axial direction, and is sandwiched between the pressing plates 47a and 47b. The insulating plate 49 has one end surface in the axial direction of each of the quartz crystal piezoelectric elements 48 and 48 (the upper surface in FIGS. 4 to 6) and one of the pressing plates 47a and 47b (above FIGS. 4 to 5). It is made of a synthetic resin or ceramic thin plate having excellent compression resistance. Of the both side surfaces in the axial direction of the insulating plate 49, the radial intermediate portion of the surface facing the one end surface in the axial direction of each of the quartz crystal piezoelectric elements 48, 48 has an annular shape as shown in FIG. The conductor 51 is attached over the entire circumference. One end of the lead wire 50 is electrically connected to the conductor 51. With this configuration, it is possible to take out the electric charges generated when the quartz crystal piezoelectric elements 48 and 48 are pressed between the pressing plates 47a and 47b through the lead wire 50. In particular, in the case of the axial force sensor 8b of this example, the lead wire 50 is taken out to the outer diameter side of the pressing plates 47a and 47b.

In the case of this example, both the pressing plates 47a and 47b are made of metal such as a steel plate and a stainless steel plate that can ensure sufficient rigidity. Among these pressing plates 47a and 47b, one (upper side in FIGS. 4 to 5) has a flat surface on both upper and lower surfaces except for a portion where through holes 55 and 55 described later are formed. On the other hand, among the both end surfaces of the other pressing plate 47b (the lower side in FIGS. 4 to 5), a plurality of recesses 53, 53 are formed on the surface facing the one pressing plate 47a in the circumferential direction, etc. Formed at intervals. Then, one end face of both end faces in the axial direction of each of the quartz crystal piezoelectric elements 48, 48 is abutted against the back end face (bottom face) of each of the recesses 53, 53, and this one end face serves as a ground electrode. The other pressing plate 47b is electrically connected. Further, a cylindrical portion 57 is formed on the inner peripheral edge of the other pressing plate 47b so as to protrude toward the one pressing plate 47a. The outer diameter of the cylindrical portion 57 is slightly smaller than the inner diameter of the one pressing plate 47a.

In the case of this example, each of the recesses 53 and 53 is a circular shape having an inner diameter slightly larger than the outer diameter of each of the crystal piezoelectric elements 48 and 48. The half (the lower half of FIGS. 4 to 6) is held in the recesses 53, 53 by being loosely fitted inside. In this manner, a plurality of the pressing plates 47b and the one pressing plate 47a (shown in the figure) in a state where the crystal piezoelectric elements 48, 48 are held in the recesses 53, 53 of the other pressing plate 47b. In this example, they are connected by three screws 54). For this purpose, through holes 55, 55 are formed in the one pressing plate 47a, and screw holes 56, 56 are formed in the other pressing plate 47b, respectively.

Each of the through holes 55, 55 has a rear half (a half near the other pressing plate 47b) as a small-diameter part having an inner diameter sufficient to insert the flange part of each screw 54, and the opening-side half (the other half) The half portion opposite to the pressing plate 47b) is a large-diameter portion having an inner diameter and a depth sufficient to loosely accommodate the head of each screw 54. The flanges of the screws 54 are inserted into the through holes 55 and 55 and screwed into the screw holes 56 and 56 so that the pressing plates 47a and 47b are slightly displaced in the axial direction. The heads of the screws 54 are connected in a state where the screw plates 54a, 47b are sandwiched between the quartz piezoelectric elements 48, 48 and the insulating plate 49. It sinks into the large diameter part of each through- hole 55 and 55, and does not protrude from the axial direction side surface of said one press board 47a. Therefore, the screws 54 are not stretched in a state where the assembled axial force sensor 8b is sandwiched between the bottom plate portion 29 of the inner case 26 and the thrust rolling bearing 23 (see FIG. 1). As a result, the axial force applied between the bottom plate portion 29 and the thrust rolling bearing 23 is effectively applied to the crystal piezoelectric elements 48 and 48 existing between the pressing plates 47a and 47b (the axial force). Is added to each of these quartz piezoelectric elements 48, 48).

In addition, one end surface of each of the quartz piezoelectric elements 48 and 48 constituting the axial force sensor 8b in the axial direction is connected to the lead wire 50 through the conductor 51, and the other end surface is the other end surface. Is grounded through the pressing plate 47b. Accordingly, by inputting the other end of the lead wire 50 to an amplifier (not shown), the total charge generated in each of the crystal piezoelectric elements 48, 48 is converted into a voltage value by this amplifier, and based on this voltage value The axial force is obtained. In the state where the constituent members of the axial force sensor 8b are assembled as described above, the cylindrical portion 57 provided on the side of the other pressing plate 47b is fitted with a gap on the inner diameter side of the one pressing plate 47a. Engage (fit) with. And by this engagement, these press plates 47a and 47b are held concentrically with each other. Accordingly, the crystal piezoelectric elements 48 and 48 are pressed evenly between the pressing plates 47a and 47b, and the axial force can be obtained with high accuracy.

According to the structure of this example in which the axial force sensor 8b having the above-described configuration is assembled between the bottom plate portion 29 and the thrust rolling bearing 23 as described above, the pad replacement operation is excellent at low cost. Motorized disc brakes that can ensure high performance and weather resistance.
First, cost reduction can be achieved by configuring the axial force sensor 8b by sandwiching the crystal piezoelectric elements 48, 48 between the pressing plates 47a, 47b. As shown in FIG. 6, the crystal piezoelectric elements 48, 48 each having a cylindrical shape (small outer diameter and axial dimensions) are extremely inexpensive and can be procured at a low cost. For this reason, the cost of the axial force sensor 8b as a whole can be sufficiently reduced as compared with the case of using a very expensive single annular crystal piezoelectric element. For this reason, cost reduction of the electric disc brake incorporating this axial force sensor 8b can be achieved.

Further, the excellent pad replacement workability and weather resistance are such that the axial force sensor 8b is formed in an annular shape as a whole, and the lead wire 50 for taking out electric charges is disposed on the outer diameter side of the axial force sensor 8b. The axial force sensor 8b can be taken out and disposed around the drive spindle 19, which serves as an input portion of the force-increasing mechanism 2a. That is, in the case of this example, the axial force sensor 8b is disposed around the drive spindle 19, so that the axial force sensor 8b is dropped when the outer and inner pads 5a and 6a are replaced. This can be prevented and the pad workability can be improved. Further, the drive spindle 19 is present in a cylinder space 41 inside the caliper 14 that is separated from an external space in which foreign matter exists. Accordingly, the axial force sensor 8b disposed around the drive spindle 19 is also present in the cylinder space 41, so that foreign matter such as muddy water can be prevented from adhering to the axial force sensor 8b. The failure of the axial force sensor 8b can be suppressed. That is, the weather resistance of the electric disc brake incorporating this axial force sensor 8b can be improved.

[Second Example of Embodiment]
FIG. 8 shows a second example of the embodiment of the present invention. Also in this example, the structure of the entire electric disc brake is as shown in FIGS. 1 to 3 as in the case of the first example of the embodiment described above. In particular, in the case of this example, the opposing surfaces of the pair of pressing plates 47a and 47c are flat surfaces (except for the cylindrical portion 57 portion provided on the pressing plate 47c side). A plurality of quartz piezoelectric elements 48 are sandwiched between the pressing plates 47a and 47c while being positioned by the holding ring 58. The holding ring 58 is an annular shape having an inner diameter slightly larger than the outer diameter of the cylindrical portion 57, and holding holes 59, 59 are formed at a plurality of locations in the circumferential direction. The inner diameters of the holding holes 59, 59 are slightly larger than the outer diameters of the quartz crystal elements 48, and the quartz piezoelectric elements 48 are loosened inside the holding holes 59, 59, and It can be held in a state of positioning. Since the configuration and operation of the other parts are the same as those in the first example of the above embodiment, overlapping illustrations and descriptions are omitted.

[Third example of embodiment]
9 to 10 show a third example of the embodiment of the present invention. In the case of this example, each crystal piezoelectric element 48a, 48a has a prismatic shape (cubic shape). In order to form such prismatic crystal piezoelectric elements 48a, 48a, flat crystal plates obtained by slicing large artificial crystals are cut into a grid pattern. These series of operations (slicing → cutting) are easy, and the waste (crystal shavings) generated by these series of operations is extremely small. For this reason, the cost of each crystal piezoelectric element 48a, 48a can be reduced by facilitating the processing operation of each crystal piezoelectric element 48a, 48a and improving the yield. In the case of this example, a cylindrical portion 57 (see FIGS. 4, 5 and 8) is provided on the pressing plate 47d provided with the concave portions 53 and 53 for holding one end portions in the axial direction of the crystal piezoelectric elements 48a and 48a. Is not provided. Since the configuration and operation of other parts are the same as in the case of the first example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Fourth Example of Embodiment]
11 to 13 show a fourth example of the embodiment of the present invention. In the case of this example, electrodes are covered on two adjacent surfaces among the six surfaces respectively provided on the plurality of quartz crystal piezoelectric elements 48a and 48a each having a prismatic shape (cubic shape). is doing. However, these electrodes coated on both sides are separated from each other. The electrode on one surface is abutted against the bottom surface of the recesses 53 formed in the pressing plate 47d, and the electrode is grounded through the pressing plate 47d. On the other hand, the electrode on the other side is connected to an amplifier (not shown) via the lead wire 50. For this purpose, the electrode on the other surface is positioned on the radially outer side of both pressing plates 47a and 47d, and a conductor 51a is wound around each of the quartz piezoelectric elements 48a and 48a. While making the other electrode conductive, the end of the lead wire 50 is connected to the conductor 51a. The conductor 51a and the pressing plate 47d are insulated from each other. Since the configuration and operation of the other parts are the same as in the case of the first example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Fifth Example of Embodiment]
14 to 15 show a fifth example of the embodiment of the present invention. In the case of this example, each crystal piezoelectric element 48b, 48b is constituted by sandwiching an electrode 61 between a pair of crystal piezoelectric element pieces 60, 60, respectively. A plurality of such crystal piezoelectric elements 48b and 48b are sandwiched between a pair of pressing plates 47b and 47d. Of the both end faces in the axial direction of the crystal piezoelectric element pieces 60, 60, the face opposite to the electrode 61 is electrically connected to the pressing plates 47b, 47d, each serving as a ground electrode, and the other end face. Is connected to one end of the lead wire 50 through the electrode 61. Since the configuration and operation of the other parts are the same as in the case of the first example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Sixth Example of Embodiment]
16 to 19 show a sixth example of the embodiment of the present invention. In the case of this example, one of the pair of pressing plates 47e and 47f is a nut plate having a screw hole 62 formed at the center. Similarly, the other pressing plate 47f is formed with a circular through hole 63 in the center. The pressing plates 47e and 47f are coupled to each other by a cylindrical coupling screw 64. The coupling screw 64 is provided with an outward flange-like flange 65 at one end in the axial direction of the outer peripheral surface and a male thread 66 at the other end. Further, a conductor 51 (see FIGS. 7A and 7B) is attached between the one pressing plate 47e and each of the crystal piezoelectric elements 48 and 48 on the side where the crystal piezoelectric elements 48 and 48 are installed. An insulating plate 49 is arranged. Further, a cylindrical engaging ridge 67 that engages with the inner peripheral edge of the insulating plate 49 is formed on the inner peripheral edge of the holding ring 58a for holding the crystal piezoelectric elements 48, 48.

When assembling the structure of this example, the holding ring 58a holding the quartz crystal elements 48 and 48 and the insulating plate 49 are sandwiched between the pressing plates 47e and 47f. The coupling screw 64 is inserted into the through hole 63 of the other pressing plate 47f from the other end side in the axial direction. Further, the male screw portion 66 of the coupling screw 64 and the screw hole 62 of the one pressing plate 47e are screwed together, and the flange portion 65 is connected to the one of the two axial side surfaces of the other pressing plate 47f. Is engaged with the inner peripheral edge of the side surface opposite to the pressing plate 47e. Then, the connecting screw 64 is tightened with a predetermined torque to connect the pressing plates 47e and 47f without separation, and an appropriate preload is applied to the crystal piezoelectric elements 48 and 48, respectively. In the case of this example, the flange portion 65 is provided in an annular recess 68 formed in a portion closer to the inner diameter of the side surface on the opposite side of the one pressing plate 47e among both axial side surfaces of the other pressing plate 47f. It is stored so that the flange 65 does not protrude from the axial side surface of the other pressing plate 47f.

In the case of this example, the quartz crystal piezoelectric elements 48 can be evenly pressed as the coupling screw 64 is tightened. As a result, not only can the performance of the obtained axial force sensor 8c be improved, but also it is possible to prevent damage to the quartz crystal element 48 due to excessive compressive stress being applied to some of the quartz crystal elements 48 during assembly work. . In addition, the basic structure and operation of the axial force sensor 8c are the same as those of the second example of the embodiment shown in FIG.

[Seventh example of embodiment]
20 to 23 show a seventh example of the embodiment of the invention. In the case of this example, the insulating plate 49 is provided between the mutually opposing side surfaces of the pair of pressing plates 47e and 47f. The insulating plate 49 has a conductor 51 (see FIGS. 7A and 7B) attached to both sides in the axial direction over the entire circumference, thereby forming a current-carrying plate described in the claims. In addition, a plurality of the quartz crystal piezoelectric elements 48 and 48 are provided between the both side surfaces in the axial direction of the insulating plate 49 and the side surfaces of the pressing plates 47e and 47f, respectively. . Then, one end face of both end faces in the axial direction of each of the quartz crystal piezoelectric elements 48, 48 is conducted to the conductor 51 on the side face in the axial direction of the insulating plate 49, and the other end face is also connected to the both pressing plates 47e, It is made to conduct | electrically_connect to one of the press plates of 47f. Further, the end portions of the lead wires 50 and 50 are connected to the both pressing plates 47e and 47f and the both conductors 51, respectively.
According to such a structure of this example, the output of the axial force sensor 8d can be increased by an amount corresponding to the increase in the number of the quartz piezoelectric elements 48, 48. The structure and operation of the other parts are the same as in the sixth example of the embodiment described above.

When carrying out the electric disk brake of the present invention, it is preferable to chamfer the corners of each crystal piezoelectric element. The reason for this is to prevent the occurrence of damage such as cracks or chips at the corners of the piezoelectric elements. That is, the sharp corners are not only easily chipped by colliding with other articles before assembly, but also may cause excessive stress during use. The mechanism for generating this stress is as follows.

Due to misalignment or the like that occurs when the axial force sensor is assembled or when the assembled axial force sensor is assembled in the case unit, the mutually opposing surfaces of the pair of pressing plates constituting the axial force sensor are somewhat non-parallel. There is a possibility. And when these both surfaces press the said each crystal piezoelectric element strongly based on the thrust load added at the time of braking in the state where these both surfaces became mutually non-parallel, an eccentric load will be added to these each crystal piezoelectric element. Based on this uneven load, excessive stress is generated at the corners of each of the quartz crystal piezoelectric elements, and the stress tends to cause damage such as cracks and chips to the corners. Quartz piezoelectric elements with damaged corners have a slightly different relationship between the applied thrust load and the amount of charge generated, but they are not the desired relationship (design value). Can get worse. Further, in a remarkable case, there is a possibility that the whole quartz piezoelectric element is cracked and the measurement of the thrust load itself becomes impossible.

Therefore, in order to prevent a situation in which the measurement accuracy of the thrust load is deteriorated or cannot be measured due to the above-described causes, damage such as a crack or a chip is caused in a corner portion of each crystal piezoelectric element. In order to prevent the occurrence of chamfering, it is preferable to chamfer 69a to 69d at the corners of the quartz crystal piezoelectric elements 48c to 48f as shown in FIGS. Of the four types of crystal piezoelectric elements 48c to 48f shown in FIGS. 24A to 24D, the crystal piezoelectric element 48c shown in FIG. 24A has a disc shape as a whole, and has an outer peripheral surface and both end surfaces in the axial direction. And chamfers 69a and 69a having a quarter arc shape in cross section. Further, the crystal piezoelectric element 48d shown in (B) has a disc shape as a whole, and is formed by chamfering 69b, 69b having a partially conical surface shape (taper surface shape) on a continuous portion between the outer peripheral surface and both end surfaces in the axial direction. Is. Further, the crystal piezoelectric element 48e shown in (C) has a square plate shape as a whole, and chamfers 69c and 69c each having a quarter-arc-shaped cross section are formed on a continuous portion between the outer peripheral surface and both end surfaces in the axial direction. It is a thing. Furthermore, the quartz crystal piezoelectric element 48f shown in FIG. 4D has a rectangular plate shape as a whole, and is formed by chamfering 69d and 69d having a partially conical surface at the continuous portion between the outer peripheral surface and both end surfaces in the axial direction.

The four types of quartz crystal piezoelectric elements 48c to 48f shown in (A) to (D) of FIG. 24 can hardly cause damage such as cracks and chips at the corners, regardless of the shape. That is, since the corner portion is not sharp, even if this corner portion collides with another article before assembly, the corner portion is not easily chipped. In addition, even when an eccentric load is applied to the crystal piezoelectric elements 48c to 48f due to the misalignment as described above, it is difficult for excessive stress to be generated at the corners of the crystal piezoelectric elements 48c to 48f. It is also possible to prevent the occurrence of damage based on it. As a result, it is possible to prevent a situation in which the measurement accuracy of the thrust load applied to the piston during braking is deteriorated or the measurement becomes impossible.

It should be noted that the four types of quartz piezoelectric elements 48c to 48f are also attached to desired portions in accordance with their usage conditions. For example, as shown in the upper part of FIGS. 24A to 24D and FIGS. 25A to 26A, electrodes can be attached to the central portion of one surface in the axial direction. Alternatively, as shown in (B) of FIGS. 25 to 26, an electrode can be attached to the entire middle of the outer peripheral surface in the axial direction. Furthermore, as shown in (C) of FIGS. 25 to 26, an electrode can be attached to a portion extending from one axial surface to the outer peripheral surface.

Further, in order to more effectively prevent damage to the corners of the crystal piezoelectric elements 48c to 48f due to the eccentric load, a range in which the pressing plate sandwiching the crystal piezoelectric elements 48c to 48f receives a thrust load is It is preferable to regulate in relation to the positions where the chamfers 69a to 69d are provided. That is, of the two axial end surfaces of the crystal piezoelectric elements 48c to 48f, the entire portion (the central flat surface portion) existing inside the chamfer sandwiches the crystal piezoelectric elements 48c to 48f. The dimensions of each part so that the pressing plates 47e and 47f (see FIGS. 16, 18 to 20, 22, and 23) are present inside the radial direction of the axial force sensors 8c and 8d from the outer peripheral edge in the range where the thrust load is received. To regulate.

Specifically, each of the piezoelectric piezoelectric elements 48c to 48f is sandwiched between a pair of pressing plates 47e and 47f with the same structure as that shown in FIGS. Of the both side surfaces in the axial direction of both the pressing plates 47e and 47f, the height is δ (see FIG. 18) on the outer surface opposite to the surface sandwiching the quartz crystal elements 48c to 48f. The annular convex portions 70 and 70 are formed. Then, the outer diameter d of both the annular convex portions 70, 70 is made sufficiently smaller than the outer diameter D of the quartz crystal piezoelectric elements 48c to 48f (see FIG. 18) (the circumscribed circle of each of the quartz piezoelectric elements 48c to 48f). The value obtained by subtracting at least twice the width dimension of each chamfer 69a to 69d in the rear direction). In short, the central flat surface portion of both end surfaces in the axial direction of each of the quartz crystal piezoelectric elements 48c to 48f is present inside the circle having a diameter d. With this configuration, the chamfers 69a, 69b, 69c, and the chamfers 69a, 69b, 69c, and the chamfers 69a, 69b, 69c, and 69d have a range where the pressing plates sandwiching the crystal piezoelectric elements 48c to 48f receive a thrust load. The stress generated in the 69d portion can be further reduced.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

This application is based on a Japanese patent application filed on September 10, 2009 (Japanese Patent Application No. 2009-208818) and a Japanese patent application filed on July 26, 2010 (Japanese Patent Application No. 2010-166716). Incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1, 1a Electric motor 2, 2a Booster mechanism 3 Piston 4 Caliper claw 5, 5a Outer pad 6, 6a Inner pad 7, 7a Rotor 8, 8a, 8b, 8c, 8d Axial force sensor 9 Holding body 10 Holding recessed part 11 Quartz piezoelectric element DESCRIPTION OF SYMBOLS 12 Cover plate 13 Charge amplifier 14 Caliper 15 Feed screw mechanism 16 Ball | bump / ramp mechanism 17 Drive side rotor 18 Screw hole 19 Drive spindle 20 Reducer 21 Deceleration large gear 22 Claw 23 Thrust rolling bearing 24 Elastic member 25 Case unit 26 Inner side Case 27 Outer side case 28 Through hole 29 Bottom plate part 30 Fixed side peripheral wall part 31 Connector 32 Extraction hole 33 Engagement hole 34 Through hole 35 Bottom plate part 36 Displacement side peripheral wall part 37 Engagement piece 38 Locking piece 39 Locking recess 40 Axis Force measuring unit 41 Dummy space 42 Concave groove 43 Stepped surface 44 Connection hole 45 Harness 46 Plug 47a, 47b, 47c, 47d, 47e, 47f Pressure plate 48, 48a, 48b, 48c, 48d, 48e, 48f Quartz piezoelectric element 49 Insulating plate 50 Lead wire 51, 51a Conductor 53 Concave part 54 Screw 55 Through hole 56 Screw hole 57 Cylindrical part 58, 58a Holding ring 59 Holding hole 60 Crystal piezoelectric element piece 61 Electrode 62 Screw hole 63 Through hole 64 Coupling screw 65 Hook part 66 Male screw part 67 Engagement Ridge 68 annular recess 69a, 69b, 69c, 69d chamfer 70 annular projection

Claims (11)

1. A rotor that rotates together with the wheels, a torque receiving member that is supported by the vehicle body in a state adjacent to the rotor, and a torque receiving member that is capable of axial displacement while sandwiching the rotor from both sides in the axial direction. And a pair of pads on the outer side and the inner side, and an actuator for pressing both the pads toward both side surfaces of the rotor. The actuator includes an electric motor and a rotational driving force of the electric motor. In an electric disc brake comprising a force-increasing mechanism that converts the thrust into a direction and transmits it to the inner pad, and an axial force sensor that measures the pressing force applied from the force-increasing mechanism to the inner pad. The axial force sensor is generally configured in an annular shape, and is rotationally driven by the electric motor and around the rotating shaft that serves as an input portion of the force-increasing mechanism. The axial force sensor includes a pair of pressing plates each formed in an annular shape and arranged in parallel to each other, and a plurality of quartz piezoelectric elements sandwiched between the pressing plates. And a lead wire for taking out electric charges generated when these quartz piezoelectric elements are pressed between the two pressing plates, and the lead wires are connected to the pressing plates. Electric disc brake characterized by being taken out to the outer diameter side of the motor.
2. An outward flange-like flange is fixed on the outer peripheral surface of the intermediate portion of the rotating shaft, and between the inner side surface of the flange and the inner side rear end surface of the storage space storing the actuator, The electric disc brake according to claim 1, wherein a thrust rolling bearing and the axial force sensor are sandwiched in order from the side.
3. The thrust rolling bearing and the flange portion are provided in an inner side case provided in a portion including the inner side of the thrust rolling bearing, and in a portion including the outer side from the flange portion, with respect to the inner side case. The thrust rolling bearing is housed in a case unit including an outer side case combined in a non-separable manner, and the thrust rolling bearing is provided by an elastic member provided between the inner side surface of the outer side case and the outer side surface of the flange. The electric disc brake according to claim 2, wherein the electric disc brake is elastically pressed toward the inner case side on which the axial force sensor is installed.
4. Both the pressing plates are made of metal, and one end surface of both end surfaces in the axial direction of each crystal piezoelectric element is electrically connected to one pressing plate serving as a ground electrode, and the other end surface is also pressed against It is abutted against the other pressing plate via an insulating plate capable of supporting force, and the other end surfaces of the quartz piezoelectric elements are arranged between the insulating plate and the other end surface of the quartz piezoelectric elements. The electric disc brake according to any one of claims 1 to 3, wherein the electric disc brake is electrically connected by a conductor and one end of the lead wire is connected to the conductor.
5. The both pressing plates are made of metal, and each of the quartz piezoelectric elements is configured by sandwiching an electrode between a pair of quartz piezoelectric element pieces. It is sandwiched between the two pressing plates, and the surface on the opposite side of the electrodes in the axial direction of each of the quartz piezoelectric element pieces is electrically connected to the pressing plates, each serving as a ground electrode. The electric disc brake according to any one of claims 1 to 3, wherein the other end face is connected to one end of the lead wire via the electrode.
6. The both pressing plates are made of metal, and energization plates are provided between the mutually opposing side surfaces of the both pressing plates, and between the axial side surfaces of the energizing plates and the side surfaces of the both pressing plates. A plurality of each of the crystal piezoelectric elements is provided in each of the portions between the two parts, and one end face of both end faces in the axial direction of each crystal piezoelectric element is electrically connected to the energizing plate. The other end face is electrically connected to any one of the pressing plates, and the end portions of the lead wires are connected to the pressing plates and the energizing plate, respectively. Item 4. The electric disc brake according to any one of Items 1 to 3.
7. A plurality of holding recesses are provided on a surface of at least one of the pressing plates facing the other pressing plate, and axial end portions of the crystal piezoelectric elements are fitted in the holding recesses. The electric disc brake according to any one of claims 1 to 6.
8. The opposing surfaces of the two pressing plates are flat surfaces, and an annular holding ring in which holding holes are formed at a plurality of locations in the circumferential direction is disposed between the two pressing plates. The electric disc brake according to any one of claims 1 to 6, wherein an intermediate portion in the axial direction of each of the quartz crystal piezoelectric elements is fitted inside.
9. One of the two pressing plates is a nut plate having a screw hole formed in the center, and the other pressing plate is a circular plate having a circular hole formed in the center. Insert an outward flange-shaped flange at one end in the axial direction, a male screw portion at the other end portion, and a cylindrical coupling screw provided respectively from the other end side in the axial direction. And the screw hole are engaged with each other, and the flange portion is engaged with an inner peripheral edge portion of a side surface on the opposite side to the one pressing plate among both axial side surfaces of the other pressing plate. Item 9. The electric disc brake according to any one of Items 1 to 8.
10. The electric disc brake according to any one of claims 1 to 9, wherein a corner portion of each crystal piezoelectric element is chamfered.
11. Of the both axial end surfaces of each quartz piezoelectric element, the entire portion existing inside the chamfer with respect to the radial direction of each quartz piezoelectric element is such that the both pressing plates sandwiching each quartz piezoelectric element exert a thrust load. The electric disc brake according to claim 10, wherein the electric disc brake is located on an inner side in a radial direction of the axial force sensor than an outer peripheral edge of a receiving range.

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