Motor actuator for electromechanical disc brakes

Abstract

The present invention relates to a motor actuator for an electromechanical disc brake that directly measures a load generated in the motor actuator and utilizes the measured load for brake control. The motor actuator of the present invention includes an electric motor that generates a rotational force, a lead nut connected to the electric motor and rotating therewith, a ball nut disposed adjacent to the inner surface of the lead nut and fixed to the lead nut, a ball screw that is engaged with the ball nut and converts the rotational force generated in the electric motor into a linear braking force, and a load sensor that measures the load applied from the lead nut.

Description

Technical Field

[0001] The present invention relates to a motor actuator, and more particularly to a motor actuator for an electromechanical disk brake that directly measures the load generated in the motor actuator and utilizes it for brake control.

Background Art

[0002] In the field of commercial vehicles, various types of electromechanical disk brakes have been developed. Since an electric motor is used as an actuator in an electromechanical disk brake, a transmission mechanism that converts the rotational force generated in the electric motor into a linear braking force, decelerates it, and amplifies (multiplies) the braking force is required. A planetary gear is frequently used as such a transmission mechanism, but because high-precision parts are required, the cost is high, and moreover, there is a problem that the structure is complex. Therefore, an electromechanical disk brake that uses a ball screw, is excellent in cost efficiency, has a simple structure, and has a compact structure has been proposed.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to provide a motor actuator for an electromechanical disk brake that directly measures the load generated in the motor actuator for use in brake control.

Means for Solving the Problems

[0004] To achieve the aforementioned objective, the present invention provides a motor actuator used in an electromechanical disc brake, comprising: an electric motor that generates rotational force; a screw nut connected to and rotating together with the electric motor; a ball nut adjacent to the inner surface of the screw nut and fixed to the screw nut; and a ball screw fastened to the ball nut and converting the rotational force generated in the electric motor into a linear braking force.

[0005] Preferably, the motor actuator further comprises a load sensor for measuring the load applied from the screw nut. The motor actuator further comprises a bearing that supports the screw nut and allows the screw nut to rotate, and the load sensor is disposed between the bearing and the housing of the motor actuator.

[0006] Preferably, the motor actuator further comprises a parking brake device for applying a parking braking force to the screw nut. The parking brake device comprises a worm wheel fixed to the outer circumferential surface of the screw nut and a worm adjuster fastened to the worm wheel. The worm adjuster comprises a worm gear fastened to the worm wheel and a handle portion, one end of which is attached to the central axis of the worm gear and the other end of which is exposed to the outside of the housing of the motor actuator.

[0007] Preferably, the parking brake device includes a clutch disc brake. The clutch disc brake comprises a stator on which a coil and a torque spring are disposed and attached to the housing of the motor actuator; a rotor that rotates integrally with the screw nut; an armature disposed between the stator and the rotor and pressing against the rotor by the elastic force of the torque spring; and a plate attached to the stator. When power is supplied to the coil, the armature is not attached to the stator and does not press against the rotor. [Effects of the Invention]

[0008] According to the electromechanical disc brake motor actuator of the present invention with the configuration described above, the brake can be controlled by directly measuring the load generated in the motor actuator. According to the present invention, since the range of load to be measured is narrow, the load sensor can be made smaller and easier to install. In addition, the accuracy of the load sensor is increased, making it easier to perform feedback control using the load value. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating the configuration of an electromechanical disc brake according to one embodiment of the present invention. [Figure 2] Figure 1 is a cross-sectional view of a ball screw integrated motor actuator. [Figure 3] This is a diagram of the adapter configuration according to one embodiment of the present invention. [Figure 4] Figure 3 is an exploded view of the adapter shown. [Figure 5] This is a diagram of a ball screw according to one embodiment of the present invention. [Figure 6] This is a diagram of the ball screw obtained by cutting along the line A-A' in Figure 5. [Figure 7] This figure illustrates a ball screw guide according to one embodiment of the present invention, fitted into the ball screw shown in Figure 6. [Figure 8] This is a diagram showing the configuration of a band-shaped lining for a parking brake device according to one embodiment of the present invention. [Figure 9] Figure 8 shows a partial configuration diagram of a ball screw integrated motor actuator equipped with a band-shaped lining. [Figure 10] This is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention. [Figure 11] Figure 10 shows the configuration diagram of the clutch disc brake. [Figure 12] This is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention. [Modes for carrying out the invention]

[0010] To further the understanding of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention are modifiable into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. These embodiments are provided to provide a more complete explanation of the present invention to a person of average knowledge in the art. Therefore, the shapes of elements in the drawings may be exaggerated to emphasize a clearer explanation. Note that identical components in each drawing are sometimes indicated by the same reference numerals. Detailed descriptions of known functions and configurations that may obscure the gist of the present invention are omitted.

[0011] Figure 1 is a configuration diagram of an electromechanical disc brake 100 according to one embodiment of the present invention, and Figure 2 is a cross-sectional view of the ball screw integrated motor actuator 101 shown in Figure 1. As shown in the same figure, the electromechanical disc brake 100 comprises a ball screw integrated motor actuator 101, a rotating lever 106, and a braking force applying piston 108. The actuator 101 comprises an electric motor 102 and a ball screw 104.

[0012] The electric motor 102 comprises a stator 110 and a rotor 112, and generates rotational force when power is supplied from a power source (not shown).

[0013] The ball screw 104 is fastened to a ball nut 116 at the front (in the direction of braking force application or brake disc direction) and to a screw nut 118 at the rear. The ball screw 104 is equipped with a sphere 120 between it and the ball nut 116. The sphere 120 is inserted between the ball screw 104 and the ball nut 116 and rotates to transmit power between the ball screw 104 and the ball nut 116. Seal components (not shown) are provided at the front and rear ends of the ball nut 116. The seal components prevent foreign matter from entering between the ball screw 104 and the ball nut 116 and trap lubricant to prevent leakage. Compared to a sliding screw that does not use a sphere, the ball screw 104 is easier to maintain with a smaller axial clearance, preventing the driving torque from becoming excessively large. In addition, wear is reduced, extending its lifespan. For the circulation of the 120 spheres, various structures such as a return pipe type, a deflector type, and an end cap type can be employed.

[0014] The screw nut 118 is adjacent to the ball nut 116 on the inner surface of the front half facing the caliper 129, and adjacent to the rotor 112 on the outer surface of the front half. Since the rotor 112 is adjacent to the outer surface of the front half of the screw nut 118 and connected to it, the motor 102 is positioned near the part where the actuator 101 is attached to the caliper 129 overall. Because the motor 102 has a relatively large load, it becomes very vulnerable to vibration as it moves away from the part where the actuator 101 is attached to the caliper 129. In this embodiment, the motor 102 is positioned near the mounting part of the actuator 101 and the caliper 129, making it resistant to vibration.

[0015] The ball nut 116 and the screw nut 118 are connected by a pin 122 inserted in a direction perpendicular to the rotating surface of the rotor 112 and operate integrally. A guide hole 123 having a shape that is not circular is formed inside the rear half portion of the ball screw 104. One end of a ball screw guide 124 is fitted into the guide hole 123, and the other end of the ball screw guide 124 is fixed relative to the housing 126. The rotor 112 is fixed to the screw nut 118. The rotational force of the rotor 112 is transmitted to the ball nut 116 via the screw nut 118. Since the rotation of the ball screw 104 is prevented by the ball screw guide 124, the ball screw 104 generates a braking force that moves in a linear direction along the ball screw guide 124 due to the rotational force transmitted to the ball nut 116. In other embodiments, the ball nut 116 and the screw nut 118 may be integrally formed.

[0016] In the present embodiment, the motor 102 is arranged so as to be adjacent to the portion where the ball nut 116 is coupled to the ball screw 104 via the sphere 120. Therefore, there is relatively little torsional twist generated in the process of switching the rotational motion of the motor 102 to a linear motion via the screw nut 118, the ball nut 116, and the ball screw 104. For this reason, the present embodiment has an advantage in that a small load is applied to the bearings 146 and 148 that support the screw nut 118.

[0017] An adapter 128 is disposed at the front end portion of the ball screw 104. The linear braking force generated in the ball screw 104 is transmitted to the rotary lever 106 via the adapter 128. The rotary lever 106 is placed on the caliper 129 via a bearing 131. The rotary lever 106 rotates due to the linear braking force generated in the ball screw 104. While rotating, the rotary lever 106 presses the pressing member 130 non-linearly to amplify the braking force, and transmits the amplified braking force to the braking force application piston 108.

[0018] The braking force application piston 108 presses against the back plate 132, pressing the friction pad 134 fixed to the back plate 132 against the brake disk 136.

[0019] A parking brake 138 is disposed at the rear half of the outer peripheral surface of the screw nut 118. The parking brake 138 includes a band-shaped lining 140 and a parking mechanism 142. The band-shaped lining 140 has lining joints 144 at both ends. One of the lining joints 144 is connected to the housing 126, and the remaining one is connected to the parking mechanism 142. The parking mechanism 142 pulls the connected lining joint 144 during the operation of the parking brake to bring the band-shaped lining 140 into close contact with the screw nut 118, generating a braking force for parking.

[0020] The bearing 146 supports the front side of the screw nut 118, and the bearing 148 supports the rear side of the screw nut 118 to enable the screw nut 118 to rotate smoothly with respect to the housing 126.

[0021] The position sensor 150 is disposed around the portion of the ball screw guide 124 exposed in the screw nut 118. The position sensor 150 is fixed to the screw nut 118 by bolts 153. The position sensor 150 detects the rotation angle of the screw nut 118 with respect to the ball screw 104 or the ball screw guide 124.

[0022] In this embodiment, the motor 102 is located in the front half of the actuator 101, and the position sensor 150 is located in the rear half. The distance between the motor 102 and the position sensor 150 is sufficiently large to minimize the impact of noise generated in the motor 102 on the position sensor 150. Furthermore, since a printed circuit board (PCB) (not shown) for the control circuit and other components is located at the rear end of the actuator 101 for maintenance purposes, the impact of noise generated in the motor 102 on the control circuit can be minimized.

[0023] The load sensor 152 measures the load (braking force) applied to the brake disc 136 by receiving the reaction force generated when the friction pad 134 presses against the brake disc 136, which is transmitted from the screw nut 118.

[0024] The housing cover 154 seals the housing 126, protecting the internal components of the housing 126 from contamination from the outside.

[0025] Figure 3 is a configuration diagram of an adapter 128 according to one embodiment of the present invention, and Figure 4 is an exploded view of the adapter 128 shown in Figure 3. As shown in the same figure, the adapter 128 comprises a connecting pin 302, an adapter bracket 304, and a pressing portion 306.

[0026] The connecting pin 302 is inserted into the front end of the ball screw 104 in a direction perpendicular to the direction in which the braking force is applied (or the direction in which the ball screw 104 moves) and the direction in which the rotary lever 106 moves. The adapter bracket 304 is provided with a connecting hole 402, which is rotatably disposed on the connecting pin 302. Therefore, the adapter bracket 304 is rotatable around the connecting pin 302 within a predetermined angular range relative to the ball screw 104. The pressing portion 306 is attached to the adapter bracket 304 on the side in which the braking force is applied and applies braking force to the mounting portion 156 of the rotary lever 106. The pressing portion 306 has a shape corresponding to the mounting portion 156 so as not to come off the mounting portion 156 when braking force is applied or released. For example, if the mounting portion 156 is a recess with a hemispherical shape, the pressing portion 306 is a convex portion with a hemispherical shape that has a diameter slightly smaller than the hemispherical shape of the mounting portion 156.

[0027] In other embodiments, the cross-sections of the pressing portion and the mounting portion may be non-circular (for example, polygonal) in order to prevent the pressing portion from rotating on the mounting portion with the direction of application of the braking force as the axis of rotation. In this case, it is not necessary to separately provide a ball screw guide 124 to prevent the rotation of the ball screw 104.

[0028] As shown in Figure 4, the load sensor 404 may be positioned on the adapter bracket 304 parallel to the direction in which the braking force is applied. The load sensor 404 is subjected to a reaction force of the braking force via the pressing portion 306. Through this configuration, the adapter 128 can measure the braking force (or load) applied to the brake disc 136. The load value measured using the adapter 128, along with the rotation angle value measured by the position sensor 150, is used to control the electric motor 102.

[0029] The rotating lever 106 plays a role in amplifying (multiplying) the braking force transmitted from the ball screw 104. Therefore, if a load sensor is installed at a downstream position of the rotating lever 106 during the braking force transmission process (for example, the braking force application piston 108 inside the caliper 129), the range of loads to be measured becomes wider. This makes the appropriate load sensor larger, making it difficult to install, and reduces measurement accuracy, making it difficult to control the electric motor 102. If the load sensor 404 is installed at an adapter 128 located at an upstream position of the rotating lever 106 during the braking force transmission process, the size of the load sensor can be reduced, making it easier to install, and sufficient measurement accuracy can be ensured, allowing for proper control of the electric motor 102.

[0030] The adapter bracket 304 has a U-shape so that it can rotate at the front end of the ball screw 104. The adapter bracket 304 has one front wall 406 and two side walls 408. The connection hole 402 is formed at opposing positions in the two side walls 408. The connection hole 402 is formed in the side wall 408 such that the front end 410 of the ball screw 104 is located at a predetermined distance from the front wall 406. This distance determines the maximum rotation angle at which the adapter bracket 304 can rotate around the connection pin 302 relative to the ball screw 104. The maximum rotation angle is set using the separation distance between the front wall 406 and the front end 410 of the ball screw 104 so that the pressing part 306 does not come off the mounting part 156 while a braking force is applied. Furthermore, the maximum rotation angle of the adapter bracket 304 relative to the ball screw 104 can be adjusted by having the connection pin 302 and / or the adapter bracket 304 have a special shape (e.g., a protrusion that causes interference). Another advantage is that by adjusting the maximum rotation angle, the ease of assembling the brake system can be improved.

[0031] The pressing portion 306 can be easily assembled and replaced by connecting it to the adapter bracket 304 using a screw tightening method.

[0032] Figure 5 is a diagram of the configuration of a ball screw 104 according to one embodiment of the present invention, and Figure 6 is a diagram of the configuration of the ball screw 104 obtained by cutting along the line A-A' in Figure 5. As shown in the figure, the ball screw 104 comprises a front end portion 502, a screw portion 504, and a rear end portion 506. The front end portion 502 is the portion that presses against the rotating lever 106. The screw portion 504 is the portion that is fastened with the ball nut 116 and the screw nut 118. A guide hole 508 with a non-circular cross-section is formed inside the rear half of the ball screw 104 (from the rear end portion 506 to approximately the center). As shown in Figure 5, for ease of processing or smooth movement, it is preferable that the guide hole 508 has an oval cross-section. Alternatively, the guide hole 508 may have a polygonal cross-section such as a triangular or rectangular shape.

[0033] Figure 7 illustrates a ball screw guide 124 according to one embodiment of the present invention, fitted onto a ball screw 104 shown in Figure 6. The ball screw guide 124 is fitted into a guide hole 508 to prevent rotation of the ball screw 104. The ball screw guide 124 comprises a fitting portion 702 and a head portion 704. The fitting portion 702 preferably has a cross-section corresponding to the guide hole 508 to prevent precise rotation. The head portion 704 is formed integrally with the fitting portion 702 and is fixed to a housing 126 or housing cover 154.

[0034] Figure 8 is a diagram showing the configuration of a band-shaped lining 140 of a parking brake device 138 according to one embodiment of the present invention. As shown in Figure 8, the band-shaped lining 140 includes a back plate 802. The back plate 802 may be made of an elastic material, such as metal. In the absence of external force, the back plate 802 is configured to have a circular shape with a cross-section having a diameter even larger than that of the screw nut 118, so that no friction occurs between the screw nut 118 and the band-shaped lining 140.

[0035] Lining joints 144 are provided at both ends of the backplate 802. One of the lining joints 144 is connected to the housing 126, and the other is connected to the parking mechanism 142. When the parking brake is applied, the parking mechanism 142 pulls the connected lining joint 144, causing the backplate 802 to be tightly pressed against the screw nut 118, so that the friction pad 804 presses against the screw nut 118. When the parking mechanism 142 releases the force pulling on the lining joint and there is no external force, the backplate 802 returns to its original position due to its elasticity, so that no friction occurs between the screw nut 118 and the band-shaped lining 140.

[0036] The band-shaped lining 140 may include a friction pad 804 fixed to the inner surface of the back plate 802. The friction pad 804 increases the frictional force of the band-shaped lining 140. To prevent contamination of the ball screw integrated motor actuator 101, the friction pad 804 is preferably made from a material that generates little dust due to friction. In addition, to prevent contamination by dust generated on the friction pad 804, sealing materials 158 and 160 may be provided in front of and behind the band-shaped lining 140, respectively, between the housing 126 and the screw nut 118. Furthermore, a discharge hole (not shown) for dust discharge may be formed in the housing 126 between the sealing material 158 and the sealing material 160.

[0037] Figure 9 is a partial configuration diagram of the ball screw integrated motor actuator 101, which is equipped with the band-shaped lining 140 shown in Figure 8. In Figure 9, the screw nut 118 is shown with its upper half cut out for better understanding.

[0038] Figure 10 is a cross-sectional view of a ball screw integrated motor actuator 1000 according to another embodiment of the present invention. As shown in the figure, the actuator 1000 comprises an electric motor 1002 and a ball screw 1004.

[0039] The electric motor 1002 comprises a stator 1010 and a rotor 1012, and generates rotational force when power is supplied from a power source (not shown).

[0040] The ball screw 1004 is fastened to a ball nut 1016 at the front (in the direction of braking force application or brake disc direction) and to a screw nut 1018 at the rear. The ball screw 1004 is equipped with a sphere 1020 between it and the ball nut 1016. The sphere 1020 is inserted between the ball screw 1004 and the ball nut 1016 and transmits power between them by rolling motion. Seal components (not shown) are provided at the front and rear ends of the ball nut 1016. The seal components prevent foreign matter from entering between the ball screw 1004 and the ball nut 1016 and trap lubricant to prevent leakage. Compared to a sliding screw that does not use a sphere, the ball screw 1004 is easier to maintain with a smaller axial clearance, preventing the driving torque from becoming excessively large. In addition, wear is reduced, extending its lifespan. For the circulation of the 120 spheres, various structures such as a return pipe type, a deflector type, and an end cap type can be employed.

[0041] The screw nut 1018 comprises a front portion 1018a having a first diameter and a rear portion 1018b having a second diameter smaller than the first diameter. The screw nut 1018 is adjacent to the ball nut 1016 on the inner surface of the front portion 1018a and adjacent to the rotor 1012 on the outer surface. A ball screw 1004 is fitted into the rear portion 1018b of the screw nut 1018 so as to be movable horizontally in the longitudinal direction. The ball nut 1016 and the screw nut 1018 are connected and act as a single unit by a pin 1022 inserted perpendicular to the rotation plane of the rotor 1012. The rotor 1012 is fixed to the screw nut 1018. The rotational force of the rotor 1012 is transmitted to the ball nut 1016 via the screw nut 1018. Since the rotation of the ball screw 1004 is prevented by the mounting portion 156 of the rotating lever (106 in Figure 1), the rotational force transmitted to the ball nut 1016 generates a braking force that causes the ball screw 1004 to move longitudinally along the screw nut 1018.

[0042] An adapter 128 may be provided at the front end of the ball screw 1004. The linear braking force generated in the ball screw 1004 is transmitted to the rotating lever 106 via the adapter 128. The rotating lever 106 is mounted on the caliper 129 via the bearing 131. The rotating lever 106 rotates due to the linear braking force generated in the ball screw 1004. As the rotating lever 106 rotates, it non-linearly presses against the pressing member 130, amplifying the braking force, and transmits the amplified braking force to the braking force application piston 108.

[0043] Bearings 1046, 1048, and 1050 allow the screw nut 1018 to rotate smoothly relative to housings 1025 and 1026. Bearing 1046 supports the screw nut 1018 in the front portion perpendicular to the axial direction Z, and bearing 1048 supports the screw nut 1018 in the rear portion. Bearing 1050 is a thrust bearing that supports the reaction force of the screw nut 1018 in the middle portion in the longitudinal direction Z, allowing the screw nut 1018 to rotate.

[0044] In Figure 1, section A is after the power is amplified by the rotary lever 106, so the range of measurable load is wide, but section A of the motor actuator 101 is before the power is amplified by the rotary lever 106, so the range of measurable load is narrow. If the range of load to be measured is wide, the load sensor becomes large and difficult to attach, and the accuracy of the load sensor decreases, making it difficult to perform feedback control using the load value.

[0045] In the motor actuator 1000, a load sensor 1052, which consists of a load cell, is disposed between the bearing 1050 and the housing 1026. The load sensor 1052 measures the load (braking force) applied to the brake disc 136 by receiving the reaction force generated when the friction pad 134 presses against the brake disc 136 via the screw nut 1018.

[0046] The operating distance of the rotary lever 106 varies depending on the gap between the brake disc 136 and the friction pad 134 and the output load of the motor actuator 1000. In particular, the gap between the brake disc 136 and the friction pad 134 varies depending on the wear of the friction pad 134. If the motor actuator 1000 is controlled by a method that controls the operating distance (displacement) of the rotary lever 106, the driver will not be able to generate a desired constant braking force. In order for the motor actuator 1000 to always produce a constant output, load feedback control is performed by directly measuring the output load of the ball screw 1004 with a load sensor 1052, regardless of the operating distance of the rotary lever 106. A thrust bearing 1050 is assembled to the lower end of the screw nut 1018, and a load sensor 1052 is assembled to the lower end of the thrust bearing 1050, so the reaction force of the piston 108 received by the ball screw 1004 is transmitted to the load sensor 1052 without loss via the screw nut 1018 and the thrust bearing 1050.

[0047] According to this embodiment, since the range of load to be measured is narrow, the load sensor can be made smaller and easier to attach. In addition, the accuracy of the load sensor is increased, making it easier to perform feedback control using the load value.

[0048] Housing 1025 supports the components of the front half of the actuator 1000, and housing 1026 supports the components of the rear half of the actuator 1000. Housing cover 1054 seals housing 1026 to protect the internal components of housings 1025 and 1026 from contamination from the outside.

[0049] The position sensor 1056 is positioned at the rear end of the screw nut 1018 and measures the degree to which the screw nut 1018 rotates relative to the housing cover 1054 to determine the position of the ball screw 1004. Since the position sensor 1056 is positioned at a sufficient distance from the motor 1002, the influence of noise generated in the motor 1002 can be minimized. In addition, since a printed circuit board (PCB) (not shown) containing the control circuit is located at the rear end of the actuator 1000 for maintenance purposes, the impact of noise generated in the motor 1002 on the control circuit can be minimized. Furthermore, since the position sensor 1056 is positioned near the printed circuit board (PCB), wiring can be easily routed.

[0050] This embodiment includes a clutch disc brake 1070 as a parking device. The clutch disc brake 1070 is disposed on the outer surface of the rear half of the screw nut 1018. Figure 11 is a configuration diagram of the clutch disc brake 1070. As shown in the figure, the clutch disc brake 1070 includes a stator 1102, an armature 1104, a rotor 1106, and a plate 1108. The stator 1102 has a coil 1110 disposed inside, and a torque spring 1112 is disposed to bias the armature 1104. Power may be supplied to the coil 1110 via a lead wire 1114. A rotor hub 1116 is disposed at the center of the rotor 1106 so as to rotate integrally with the rotor 1106. The rotor hub 1116 is fixed to the outer surface of the screw nut 1018. Thus, the rotor 1106 rotates together with the screw nut 1018. The stator 1102 is fixed to the housings 1025 and 1026. Socket head cap screws 1118 are fastened to the stator 1102, armature 1104, and plate 1108.

[0051] During braking, power (electricity) is supplied to the stator 1010, causing the rotor 1012 to rotate and rotate the screw nut 1018. Since the screw nut 1018 is connected to the ball nut 1016, it pushes the brake rotation lever 106, which is connected to the ball screw 1004. The rotation lever 106 pushes the brake piston 108, causing the friction pad 134 and brake disc 136 to come into close contact and apply braking. If the power (electricity) supply is cut off while the rotation lever 106 is applying force to the piston 108, the ball screw 1004 will move slightly backward due to the reaction force of the rotation lever 106. At this time, the ball screw 1004 loses some of the force it was applying to the piston 108. For the actuator 1000 to perform the parking brake function, it must maintain the force applied to the piston 108 even when the power (electricity) supply is cut off. Therefore, in this embodiment, a clutch disc brake 1070 is used to maintain the force applied to the piston 108. If power is not supplied to the clutch disc brake 1070, the torque spring 1112 biases and fixes the armature 1104 and rotor 1106, and fixes the ball screw 1018 connected to the rotor hub 1106. When power is supplied to the clutch disc brake 1070, the stator 1102 and coil 1110 of the clutch disc brake 1070 retract the armature 1104, releasing the ball screw 1018 from its restraint.

[0052] Figure 12 is a cross-sectional view of a ball screw integrated motor actuator 1200 according to another embodiment of the present invention. As shown in the figure, the actuator 1200 comprises an electric motor 1202 and a ball screw 1204.

[0053] The electric motor 1202 comprises a stator 1210 and a rotor 1212, and generates rotational force when power is supplied from a power source (not shown).

[0054] The ball screw 1204 is fastened to a ball nut 1216 at the front (in the direction of braking force application or brake disc direction) and to a screw nut 1218 at the rear. The ball screw 1204 is equipped with a sphere 1220 between it and the ball nut 1216. The sphere 1220 is inserted between the ball screw 1204 and the ball nut 1216 and transmits power between them by rolling motion. Seal components (not shown) are provided at the front and rear ends of the ball nut 1216. The seal components prevent foreign matter from entering between the ball screw 1204 and the ball nut 1216 and trap lubricant to prevent leakage. Compared to a sliding screw that does not use a sphere, the ball screw 1204 is easier to maintain with a smaller axial clearance, preventing the driving torque from becoming excessively large. In addition, wear is reduced, extending its lifespan. For the circulation of the 120 spheres, various structures such as a return pipe type, a deflector type, and an end cap type can be employed.

[0055] The screw nut 1218 comprises a front portion 1218a having a first diameter and a rear portion 1218b having a second diameter smaller than the first diameter. The screw nut 1218 is adjacent to the ball nut 1216 on the inner surface of the front portion 1218a and adjacent to the rotor 1212 on the outer surface. A ball screw 1204 is fitted into the rear portion 1218b of the screw nut 1218 so as to be movable horizontally in the longitudinal direction. The ball nut 1216 and the screw nut 1218 are connected and act as a single unit by a pin 1222 inserted perpendicular to the rotation plane of the rotor 1212. The rotor 1212 is fixed to the screw nut 1218. The rotational force of the rotor 1212 is transmitted to the ball nut 1216 via the screw nut 1218. Since the rotation of the ball screw 1204 is prevented by the mounting portion 156 of the rotating lever (106 in Figure 1), the rotational force transmitted to the ball nut 1216 generates a braking force that causes the ball screw 1204 to move longitudinally along the screw nut 1218.

[0056] An adapter 128 may be provided at the front end of the ball screw 1204. The linear braking force generated in the ball screw 1204 is transmitted to the rotating lever 106 via the adapter 128. The rotating lever 106 is mounted on the caliper 129 via the bearing 131. The rotating lever 106 rotates due to the linear braking force generated in the ball screw 1204. As the rotating lever 106 rotates, it non-linearly presses against the pressing member 130, amplifying the braking force, and transmits the amplified braking force to the braking force application piston 108.

[0057] Bearing 1246 supports the front side of screw nut 1218, and bearing 1248 supports the rear side of screw nut 1218, so that screw nut 1218 can rotate smoothly relative to housings 1225 and 1226.

[0058] Housing 1225 supports the components of the front half of actuator 1200, and housing 1226 supports the components of the rear half of actuator 1200. Housing cover 1254 seals housing 1226 to prevent the internal components of housings 1225 and 1226 from being contaminated from the outside.

[0059] The thrust bearing 1250 rotates while supporting the reaction force of the screw nut 1218. A load sensor 1252, composed of load cells, measures the load (braking force) applied to the brake disc 136 by transmitting the reaction force generated when the friction pad 134 presses against the brake disc 136 via the screw nut 1218 and thrust bearing 1250. A position sensor 1256 is located at the rear end of the screw nut 1218 and measures the degree to which the screw nut 1218 has rotated relative to the housing cover 1254 to determine the position of the ball screw 1204. Since the position sensor 1256 is located at a sufficient distance from the motor 1202, the influence of noise generated in the motor 1202 can be minimized. In addition, since a printed circuit board (PCB) (not shown) for the control circuit and other components is located at the rear end of the actuator 1200 for maintenance purposes, the impact of noise generated in the motor 1202 on the control circuit can be minimized. Furthermore, since the position sensor 1256 is located near the printed circuit board (PCB), it is easy to route the wiring.

[0060] In this embodiment, the motor actuator 1200 further comprises a parking brake device. The parking brake device consists of a worm wheel 1270 and a worm adjuster 1272. The worm adjuster 1272 comprises a worm gear 1272a that is fastened to the worm wheel 1270, and a handle portion 1272b, one end of which is attached to the central axis of the worm gear 1272a and the other end of which is exposed to the outside of the motor actuator 1200. The worm wheel 1270 is fixed to the outer circumferential surface of the rear half of the screw nut 1218. The worm wheel 1270 meshes with the worm gear 1272a. Since one end of the handle portion 1272b is attached to the central axis of the worm gear 1272a, it rotates together with the worm gear 1272a. The handle portion 1272b is exposed through a hole formed in the housing cover 1254.

[0061] During braking, power (electricity) is supplied to the stator 1210, causing the rotor 1212 to rotate and rotate the screw nut 1218. Since the screw nut 1218 is connected to the ball nut 1216, it pushes the brake rotation lever 106, which is connected to the ball screw 1204. The rotation lever 106 pushes the brake piston 108, causing the friction pads 134 and the brake disc 136 to come into close contact and apply braking. If the power (electricity) supply is cut off while the rotation lever 106 is applying force to the piston 108, the ball screw 1204 will move slightly backward due to the reaction force of the rotation lever 106. At this time, the ball screw 1204 loses some of the force it was applying to the piston 108. For the actuator 1200 to perform the parking brake function, it must maintain the force it was applying to the piston 108 even when the power (electricity) supply is cut off. Therefore, the worm wheel 1270 and worm adjuster 1272 prevent the screw nut 1218 from reversing, thereby preventing the ball screw 1204 from moving backward. In addition, if the power (electricity) supply is interrupted, the worm adjuster 1272b can be manually rotated to adjust the position of the ball screw 1204, allowing the friction pad 134 to be replaced (maintained), and the drag state of the brake disc 136 and friction pad 134 to be released.

[0062] The embodiments of the electromechanical disc brake of the present invention described above are merely illustrative, and any person with ordinary skill in the art to which the present invention pertains will understand that a variety of modifications and equivalent other embodiments are possible. Therefore, it should be clear that the present invention is not limited to the forms mentioned in the detailed description above. Thus, the true technical scope of protection of the present invention should be determined by the technical idea of ​​the appended claims. Furthermore, the present invention should be understood to include all variations, equivalents, and substitutes that fall within the spirit and scope of the invention as defined by the appended claims.

Claims

1. In a motor actuator used in an electromechanical disc brake, An electric motor that generates rotational force, A screw nut connected to the aforementioned electric motor and rotating together with it, A ball nut is provided adjacent to the inner surface of the screw nut and fixed to the screw nut, A ball screw fastened to the ball nut converts the rotational force generated in the electric motor into a linear braking force, A load sensor is used to measure the load applied from the screw nut. A motor actuator characterized by being equipped with [a specific feature].

2. The motor actuator according to claim 1, further comprising a parking brake device for applying parking braking force to the screw nut.

3. The motor actuator according to claim 2, characterized in that the parking brake device comprises a clutch disc brake.

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