JP2002195321A - Actuator assembly for brake system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator assembly for brake system excluding electromagnetic interference. SOLUTION: This actuator assembly for brake system of an automobile comprises a brake member allowed to come into contact with the rotating member of a brake system. The actuator assembly further comprises a piezoelectric actuator connected to the brake member so as to move the brake member allowed to come into contact with the rotating member according a received signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates generally to vehicular braking systems and to actuator assemblies for automotive braking systems.

[0002]

2. Description of the Related Art It is known to provide brakes in vehicles such as automobiles, work machines and various other applications. Typical braking systems for motor vehicles are of the hydraulic type, such as fixed caliper brakes, floating caliper brakes, drum brakes and the like.

[0003] It is also known that wire brake (BBW) technology is currently being developed by automobile manufacturers. One such BBW technology is electro-hydraulic braking, which also requires a group of valves to achieve the required braking action. The valve is driven by an electromagnetic solenoid or a pilot system. However, electronically controlled valves are all driven by electromagnetic solenoids.

While the above electromagnetic solenoids have operated, they suffer from electromagnetic interference (EMI). Another disadvantage is that the electromagnetic solenoid can only move in one direction, ie in one direction. Therefore, most dual-acting hydraulic valves require the use of two solenoids located at opposite ends of the hydraulic valve spool.

Accordingly, it is desirable to provide an actuator assembly for a brake system that eliminates electromagnetic interference. It would also be desirable to provide an actuator assembly for either a disk-type or drum-type braking system that generates braking force in a motor vehicle braking system. It is further desirable to provide a lightweight, actuator assembly for a brake system that operates over a wider temperature range without hysteresis. Accordingly, there is a need in the art to provide an actuator assembly for a brake system that meets these needs.

[0006]

SUMMARY OF THE INVENTION Accordingly, in one embodiment of the present invention,
An actuator assembly for a brake system is provided having a brake member for contacting a rotating member of the brake system. The actuator assembly further includes a piezoelectric actuator connected to the brake member for moving the brake member to contact the rotating member in response to an incoming signal.

One advantage of the present invention is that the actuator assembly is provided for a piezoelectric (PZT) type braking system. Another advantage of the present invention is that the actuator assembly uses a PZT actuator to generate braking force / torque for the braking system, whether of the disk or drum type, and is applied to a parking brake system. It is possible. Yet another advantage of the present invention is that the actuator assembly produces braking force directly at the wheel brake actuator and requires little maintenance (only maintenance is required for pads and disks). Yet another advantage of the present invention is that the actuator assembly does not need to detect and adjust air gaps and does not require force sensors or motor signal evaluation. Yet another advantage of the present invention is that the actuator assembly eliminates electromagnetic interference, reduces the number of components, and reduces the overall system weight. Yet another advantage of the present invention is that the actuator assembly provides a lower hysteresis magnetization curve, operates over a wider temperature range, and has a higher torque density (Nm / m3) than an electric motor. It is to have. Yet another advantage of the present invention is that the actuator assembly is environmentally friendly because no brake fluid is used.
In addition, a friction material (brake pad) is used.

[0008] Other features and advantages of the present invention will become better understood and apparent from a reading of the detailed description of the invention with reference to the accompanying drawings.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, and in particular to FIGS.
The actuator assembly 10 according to the present invention is
(Partially shown) brake system
(Indicated by). In this embodiment, the brake system is of the disc type. The brake system 12 has a rotatable disc brake 16, which is connected to an axle (not shown) of the vehicle 14 and is connected to wheels (not shown) of the vehicle 14. I have. The brake system 12 further includes a brake housing 18 connected to the vehicle structure 20 of the vehicle 14 by any suitable means, such as fasteners 22. The brake housing 18 is substantially cylindrical and has a cavity 24 for receiving a portion of the actuator assembly 10. The brake system 12 further has a brake caliper 26 connected to the brake housing 18 and extending to the disc brake 16. The brake system 12 includes a first back plate 28 connected to a caliper 26 on one side of the disc brake 16 and an actuator assembly 1.
And a second back plate 30 coupled to the second back plate 30.
The brake system 12 further includes a first back plate 2
8 and a second brake pad 3 connected to a second back plate 30.
And 4. It should be appreciated that the brake system 12 may be a disc type or a drum type. Further, it should be recognized that, other than the actuator assembly 10, the brake system 12 is conventional and known.

Referring to FIGS. 1-3, an actuator assembly 10 according to the present invention includes a piezoelectric actuator 38. A piezoelectric actuator 38 is operatively connected to the first back plate via the caliper 26 to move the first brake pad 32 such that the first brake pad 32 contacts the disc brake 16; Second
Operatively connected to the second back plate 30 via pins 54 to move the second brake pad 34 so that the second brake pad 34 contacts the disc brake 16. The piezoelectric actuator 38 has a housing 40 having a chamber 42. As shown, the housing 40 is substantially cylindrical, but may have any other suitable shape. The housing 40 has one opening 44 extending in the longitudinal direction through both ends. Housing 4
0 is made of a metal material such as aluminum. The housing 40 is structurally composed of two parts, a first part 40a arranged in the cavity 24 of the brake housing 22 and a longitudinally spaced part from the first part 40a, and the brake caliper 26 Has a second portion 40b disposed in the recess 40c. First part 40a
And the second part 40b are connected to the brake housing 22 and the brake caliper 26 by the seal 41 disposed in the groove 41a of the first part 40a and the second part 40b.
Is sealed.

The piezoelectric actuator 38 includes a housing 4
0 has a rotatable bearing member 46 disposed between the first portion 40a and the second portion 40b. The bearing member 46 extends in the longitudinal direction and is substantially cylindrical. The bearing member 46 has annular recesses 47 at both ends in the longitudinal direction. The piezoelectric actuator 38 further has a bearing member 46 and an annular bearing 48 located in each recess 47 between the brake housing 24 and the brake caliper 26. The bearing 48 is of a roller ball type, which is the same as a conventional one and is well known. The bearing member 46 is, via a bearing 48,
It should be appreciated that the brake housing 24 and the brake caliper 26 can rotate relative to each other.

The piezoelectric actuator 38 further includes a core spool 50, which is located within the chamber 42 of the housing 40 and is movable therein. The core spool 50 has a shaft portion 51,
The shaft portion 51 extends in the axial direction through the opening 44 of the housing 40. The shaft portion 51 is substantially columnar and has a substantially circular cross section. The core spool 50 has, at both ends of a shaft portion 51, end portions 52 having an enlarged diameter. The core spool 50 is made of a metal material such as steel.

The actuator assembly 10 has a plate member 53 connected to one of the ends 52. The plate member 53 is connected or coupled to the second back plate 30 of the brake system 12 by any suitable means such as a pin 54.

The piezoelectric actuator 38 further has at least one, preferably a plurality, and preferably eight piezoelectric motors 56. The piezoelectric motor 56 includes a core spool 50
And extends axially along the core spool 50 at circumferential intervals around the core spool 50. The function of the piezoelectric motor 56 will be described later. The piezoelectric motor 56 is substantially rectangular. Piezoelectric motor 5
6 is a linear motor type, Zumeris
U.S. Pat. No. 5,453,653. The disclosure of which is incorporated herein by this reference. The piezoelectric motor 56 is arranged on the piezoelectric ceramic plate, and can excite the transverse bending mode at a frequency close to the longitudinal expansion mode under the excitation drive of the piezoelectric ceramic plate and the ceramic shape.

The actuator assembly 10 further includes a controller 58 for supplying power to the piezoelectric motor 56.
The piezoelectric motor 56 is connected to the controller 58 by a suitable means (not shown) such as an electric wire. It should be appreciated that controller 58 is conventional and well known.

The piezoelectric actuator 38 further has at least one, and preferably a plurality of, support springs 60. The support springs 60 are arranged between the piezoelectric motor 56 and the bearing member 46 and between the piezoelectric motor 56 and the housing 40. Support spring 60 is connected to piezoelectric motor 56, bearing member 46 and housing 40 by any suitable means. It should be recognized that the piezoelectric motor 56 has a wide range of travel and is less susceptible to electromagnetic interference. Further, the piezoelectric motor 56 inherently stops when there is no electric field.
It should also be recognized that they exhibit stalling power. Furthermore,
It should also be appreciated that in the presence of an electric field, the crystal structure of the piezoelectric motor 56 changes its shape and changes its material size.

In operation of the actuator assembly 10, the brake pedal (not shown) of the brake system 12 sends a signal to the controller 58. Then the controller 58
Sends a corresponding command or signal to the piezoelectric actuator 38 to move the second brake pad 34 or the first brake pad 32 toward each other, brake the disc brake 16 and reduce the rotation of the disc brake 16 Or stop. Power from controller 58 is received by piezoelectric motor 56, which provides a drive frequency to core spool 50. Since the piezoelectric motor 56 is connected to the core spool 50,
An asymmetric driving force is applied to the zero, thereby causing movement. The periodicity of the driving force at a frequency much higher than the mechanical resonance frequency of the core spool 50 allows for continuous and smooth movement of unlimited movement, while providing high resolution and positioning accuracy. The linear movement of the core spool 50 then moves the second back plate 30 and the second brake pad 34 linearly to engage the disc brake 16, or the first back plate 28 and the first The brake pad 32 is moved linearly and engaged with the disc brake 16 to reduce or stop the rotation of the disc brake 16. Second brake pad 34, second back plate 30, plate member 5
3. It should be recognized that the core spool 50, the motor 56 and the bearing member 46 can rotate together. Further, it should be appreciated that the piezoelectric motor 56 can move in either direction depending on the transmitted electrical signal. Further, it should be recognized that the braking force / torque produced by the actuator assembly 10 can be calculated from the number of piezoelectric motors 56, the maximum force of each piezoelectric motor 56, and the brake factor.

Referring to FIG. 4, the actuator assembly 10
6 shows another embodiment 110 according to the present invention. The reference numerals of similar parts of the actuator assembly 10 are increased by 100. In this embodiment, the actuator assembly 110 has a rotatable piezo actuator 138, which can be moved in both directions of rotation, and the gear train 18 to operate the brake system 12.
Used in combination with 2. Piezoelectric actuator 13
8 has a housing 140 with a chamber 142. As shown, the housing 140 is substantially cylindrical, but may have any other suitable shape. The housing 140 has one hole 143 extending in the longitudinal direction, and has one opening 144 at one end of the hole 143. The housing 140 is made of a metal material such as aluminum.
The housing 140 is structurally two-part, having a first part 140a located within the cavity 24 of the brake housing 22 and a second part 140b at the longitudinal end opposite the opening 144. .

The piezoelectric actuator 138 has a rotatable power screw 162 disposed in the hole 143. The power screw 162 extends in the longitudinal direction and is substantially columnar. The power screw 162 has a plurality of screws at one end in the longitudinal direction. The function will be described later. Piezoelectric actuator 138 further includes an annular bearing 148 disposed in bore 143 between power screw 162 and housing 140.
Having. The bearing 148 is a roller ball type, which is conventional and well known. Power screw 1
62 is connected to the housing 140 via the bearing 148.
It should be recognized that it is possible to rotate relative to.

The piezoelectric actuator 138 further includes a nut 1
66, and nut 166 is
43, and can move linearly therein. The nut 166 is substantially cylindrical and has a substantially circular cross section. The nut 166 has one passage 168 extending axially therethrough and a plurality of screws 17 along the passage 168 to cooperate with the threads of the power screw 162.
Has zero.

The piezoelectric actuator 138 includes the piston 17
2 and the piston 172 is connected to one end of the nut 166. The piston 172 is substantially columnar and has a substantially circular cross section. The piston 172 has a shaft portion 173
And the shaft portion 173 extends in the axial direction and has a reduced diameter portion. The shaft portion 173 is substantially columnar and has a substantially circular cross section. The shaft portion 173 is connected to the power screw 162
Has a cavity 173a for receiving one end of the same.
Piston 172 is sealed to housing 140 by seal 174 located within annular groove 176 of piston 172.
Sealed against.

The piezoelectric actuator 138 further has at least one piezoelectric motor 156 that extends in the axial direction and is radially spaced from the power screw 182. The function will be described later. The piezoelectric motor 156 is substantially circular. The piezoelectric motor 156 is a rotary motor type. The piezo motor 156 is placed on the piezo plate, which can excite to a transverse bending vibration mode at a frequency close to the longitudinal extension mode, under the drive of the excitation state and the shape of the ceramic. it can. Piezoelectric motor 156 is electrically connected to controller 158 by suitable means (not shown) such as electric wires.

The piezoelectric actuator 138 has a rotatable shaft 178, one end of which is connected to the piezoelectric motor 156. The shaft 178 is substantially columnar and has a substantially circular cross section. Shaft 17
8 extends through one opening 180 of housing 140 and is substantially parallel to power screw 162.

The piezoelectric actuator 138 has a gear train (generally designated by reference numeral 182), one end of which is connected to a power screw 162 and a shaft 178. The gear train 182 has a first gear 184 connected to one end of the power screw 162 and a second gear 186 connected to one end of the shaft 178. Gears 184, 186 and 188 are of the spur gear type. It should be recognized that gear train 182 is primarily for reducing speed and increasing transmitted torque. It should be recognized that worm gears can be used instead of spur gears.

The actuator assembly 110 has a plate member 153 connected to the end of the piston 172. The plate member 153 is connected or coupled to the second back plate 30 of the brake system 12 by any suitable means such as a pin 154.

In operation of the actuator assembly 110, the brake pedal (not shown) of the brake system 12 sends a signal to the controller 158, which sends a corresponding command or signal to the piezo actuator 138, By moving the brake pad 34 or the first brake pad 32 in the direction of each other, the brake is applied to the disc brake 16 and the rotation of the disc brake 16 is decelerated or stopped. Power from controller 158 is received by piezoelectric motor 156, which provides a drive frequency to shaft 178. Since the piezoelectric motor 156 is coupled to the shaft 178, an asymmetric driving force is applied to the shaft 178 to cause movement. Shaft 17
The periodicity of the driving force at a much higher frequency compared to the mechanical resonance frequency of 8 allows continuous smooth movement for unlimited movement. On the other hand, high resolution and positioning accuracy are maintained. The rotation of shaft 178 then rotates gear train 182, which causes power screw 162 and nut 166 to convert the rotation into a linear movement. This linear movement is used to drive the brake pads 32 and 34 toward the brake disc 16. Power screw 162, nut 166 and hole 143
It should be recognized that is provided to change the rotational motion into a linear motion.

FIG. 5 shows another embodiment 210 of the actuator assembly 10 according to the present invention. The same reference numerals as those of the actuator assembly 10 are used. In this embodiment, the actuator assembly 210 has a piezoelectric actuator 238. Piezoelectric actuator 238 can generate linear motion in both directions and is used in combination with the drum brake of brake system 12. In this embodiment, the brake system 12
Is a drum type. The brake system 12 has a rotatable brake drum 216 and the brake drum 21
6 is connected to the shaft (not shown) of the automobile 14 and
4 (not shown).
The brake drum 216 is substantially cylindrical and has a cavity 217 for receiving a portion of the actuator assembly 210. The brake system 12 further has a leading brake shoe 219a and a trailing brake shoe 219b. These are connected to the vehicle structure 20 of the vehicle 14 by suitable means such as fasteners 221. Brake system 12 further includes brake shoes 219a and 219b for engaging brake drum 216 to reduce or stop rotation of the brake drum.
Has a friction pad 223 disposed on both. The brake system 12 includes brake shoes 219a and 2
It has at least one, preferably a plurality of springs 225 connected to each other to draw the 19b toward each other. The brake system 12 further includes a brake shoe 219 a for adjusting the brake shoes 219 a and 219 b relative to the actuator assembly 210.
a and caliper 22 connecting the lower ends of 219b to each other
Seven. Actuator assembly 210 is disposed between the ends of brake shoes 219a and 219b to push brake shoes 219a and 219b toward the braking surface of brake drum 216. It should be appreciated that the brake system 12 is conventional and known, except for the actuator assembly 210.

According to the present invention, the actuator assembly 2
10 has a piezoelectric actuator 238, which has a housing 240 with a chamber 242 inside. As shown, housing 240 is substantially cylindrical, but any other suitable structure can be used. The housing 240 has an opening 244 extending through one end in the longitudinal direction. The housing 240 is made of a metal material such as aluminum. Housing 240
Is a two-part structure, the first part 240
a and a second portion 240b connected to the first portion 240a.

The piezo actuator 238 further includes a core spool 250 disposed within and movable within the chamber 242 of the housing 240. The core spool 250 is substantially columnar and has a substantially circular cross section. The core spool 250 extends in the axial direction and penetrates the opening 244 of the housing 240. The core spool 250 has at one end a guide cavity 290 extending axially therein, and
It has a guide 292. Guides 292 extend axially into housing 240 and into passageway 290 to linearly guide core spool 250. The core spool 250 is made of a metal material such as steel.

The piezoelectric actuator 238 further has at least one, preferably a plurality, preferably six, piezoelectric motors 256. The piezoelectric motor 256 extends radially from the core spool 250 and is spaced circumferentially around the core spool 250 and axially spaced from the core spool 250.
It extends along 50. The function of the piezoelectric motor 256 will be described later. The piezoelectric motor 256 is substantially circular.
Piezoelectric motor 256 is of the linear motor type and is similar to that disclosed in Zumeris US Pat. No. 5,453,653. The disclosure of which is incorporated herein by this reference. The piezoelectric motor 256 is disposed on a piezoelectric ceramic plate,
Under the excitation driving of the piezoelectric ceramic plate and the ceramic shape, the transverse bending mode can be excited at a frequency close to the longitudinal expansion mode. Piezoelectric motor 25
6 is connected to the controller 258 by suitable means (not shown) such as electric wires.

The piezoelectric actuator 238 further has at least one, preferably a plurality of support springs 260. The support spring 260 is connected to the piezoelectric motor 256 and the housing 2.
40. The support spring 260 is connected to the piezoelectric motor 256 and the housing 240 by any suitable means. It should be recognized that the piezoelectric motor 256 has a wide range of travel and is less susceptible to electromagnetic interference. Further, it should be appreciated that the piezoelectric motor 256 inherently exhibits a stopping force in the absence of an electric field. Further, it should be recognized that the crystal structure of piezoelectric motor 256 changes its shape and the size of its material in the presence of an electric field.

In operation of actuator assembly 210, a brake pedal (not shown) of brake system 12 sends a signal to controller 258. Then the controller 25
8 transmits the corresponding command or signal to the piezoelectric actuator 23
8, and the brake shoes 219a and 219b are
Move away from each other and into engagement with the brake drum 216 to slow down or stop the rotation of the brake drum 216. Power from controller 258 is received by piezoelectric motor 256, which provides a drive frequency to core spool 250. Piezoelectric motor 2
Because 56 is coupled to core spool 250, an asymmetric driving force is applied to core spool 250, thereby causing movement. The periodicity of the driving force at a frequency much higher than the mechanical resonance frequency of the core spool 250 allows for continuous and smooth movement of unlimited movement, while providing high resolution and positioning accuracy. The linear movement of the core spool 250 then causes the brake housing 240 to move linearly, causing the brake shoes 219 a and 219 b to rotate or expand toward the braking surface of the brake drum 216, causing the rotation of the brake drum 216. Slow down or stop. The piezoelectric drive drum brake system 12 is a piezoelectric drive disk brake system 1 described with reference to FIGS.
It should be recognized that it operates similarly to 2. Further, it should be appreciated that the linear piezoelectric motor 256 is constructed to push the brake shoes 219a and 219b outward to engage the brake drum 216 of the brake system 12. It should also be appreciated that the linear piezoelectric actuator 238 can be replaced by a rotatable piezoelectric motor 156 with the gear train 182 and screw nuts 162-166 described with reference to FIG.

The invention has been described. It is to be understood that the words used herein are intended to be illustrative and not limiting.

Various modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the claims, the present invention can be carried out in a mode different from that specifically described.

[Brief description of the drawings]

FIG. 1 is a perspective view of an actuator assembly according to the present invention in cooperation with a vehicle brake system.

FIG. 2 is a sectional elevation view of the actuator assembly of FIG. 1 and a disk-type brake system of an automobile.

FIG. 3 is a vertical sectional view of the actuator assembly and the disc type brake system of FIG. 2;

FIG. 4 is an elevational sectional view of another embodiment of the actuator assembly and disc type brake system of FIG. 1 according to the present invention;

FIG. 5 is a sectional elevation view of yet another embodiment of the actuator assembly and drum type brake system of FIG. 1 according to the present invention;

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Pangrock Ow, Michigan, USA 48105 Ann Arbor Green Briar Boulevard 3665- # 142 Be (Reference) 3J058 AA43 AA53 AA58 CC16 FA01 FA11 FA31

Claims (1)

[Claims] 1. An actuator assembly for a brake system of a vehicle, comprising: a brake member for contacting a rotating member of the brake system; A movable member operably connected to the movable member and at least one piezoelectric motor operably connected to the movable member to move the movable member and the brake member to contact the rotating member in response to a received signal. An actuator assembly comprising: a piezoelectric actuator having: and a piezoelectric actuator having: