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 disc brake that directly measures the load generated in the motor actuator and utilizes the measured load for brake control. [Background technology]

[0002] Various types of electromechanical disc brakes have been developed for commercial vehicles. Because electromechanical disc brakes use electric motors as actuators, they require a transmission mechanism that converts the rotational force generated by the electric motor into linear braking force, decelerates the vehicle, and amplifies the braking force. Planetary gears are often used as such transmission mechanisms, but they require highly precise components, which increases costs and creates complex structures. Therefore, electromechanical disc brakes using ball screws have been proposed, which are cost-effective, simple, and compact. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION The present invention provides a motor actuator for an electromechanical disc brake that directly measures the load exerted on the motor actuator for use in brake control. [Means for solving the problem]

[0004] In order to achieve the above-mentioned object, the present invention provides a motor actuator for use in an electromechanical disc brake, comprising: 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 an inner surface of the lead nut and fixed to the lead nut; and a ball screw that is fastened to the ball nut and converts the rotational force generated in the electric motor into a braking force in a linear direction.

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

[0006] Preferably, the motor actuator further includes a parking brake device that applies a parking braking force to the lead screw nut. The parking brake device includes a worm wheel fixed to an outer circumferential surface of the lead screw nut and a worm adjuster fastened to the worm wheel. The worm adjuster also includes a worm gear fastened to the worm wheel and a handle portion having one end attached to a central axis of the worm gear and the other end exposed to the outside of a housing of the motor actuator.

[0007] Preferably, the parking brake device includes a clutch disc brake, the clutch disc brake including a stator having a coil and a torque spring disposed therein and attached to a 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 the rotor with the elastic force of the torque spring, and a plate attached to the stator. When power is supplied to the coil, the armature is attached to the stator and does not press the rotor. [Effects of the Invention]

[0008] The motor actuator for an electromechanical disc brake of the present invention, configured as described above, can directly measure the load generated in the motor actuator to control the brake. According to the present invention, the range of loads to be measured is narrow, so the load sensor is small and easy to install. Furthermore, the accuracy of the load sensor is high, making it easy to perform feedback control using the load value. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an electromechanical disc brake according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the ball screw integrated motor actuator shown in FIG. 1. [Figure 3] FIG. 1 is a structural diagram of an adapter according to an embodiment of the present invention. [Figure 4] FIG. 4 is an exploded view of the adapter shown in FIG. 3. [Figure 5] 1 is a configuration diagram of a ball screw according to an embodiment of the present invention; [Figure 6] FIG. 6 is a configuration diagram of a ball screw taken along line AA' in FIG. 5. [Figure 7] 7 is a diagram illustrating a state in which a ball screw guide according to an embodiment of the present invention is fitted into the ball screw shown in FIG. 6. FIG. [Figure 8] FIG. 2 is a structural diagram of a band-shaped lining of a parking brake device according to an embodiment of the present invention. [Figure 9] FIG. 9 is a diagram illustrating a portion of the ball screw integrated motor actuator in which the band-shaped lining shown in FIG. 8 is disposed. [Figure 10] FIG. 10 is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention. [Figure 11] FIG. 11 is a diagram illustrating the configuration of the clutch disc brake shown in FIG. [Figure 12] FIG. 10 is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] To facilitate a better 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 can be modified 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 more completely explain the present invention to those skilled in the art. Therefore, the shapes of elements in the drawings may be exaggerated to emphasize a clearer description. It should be noted that the same components in the drawings are sometimes designated by the same reference numerals. Detailed descriptions of known functions and configurations that may obscure the gist of the present invention will be omitted.

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

[0012] The electric motor 102 includes 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 its front (the direction in which the braking force is applied or the brake disc direction) and to a lead screw nut 118 at its rear. The ball screw 104 is provided with a ball 120 between it and the ball nut 116. The ball 120 is inserted between the ball screw 104 and the ball nut 116 and performs a rolling motion, thereby transmitting power between the ball screw 104 and the ball nut 116. Seals (not shown) are provided at the front and rear ends of the ball nut 116. The seals prevent foreign matter from entering between the ball screw 104 and the ball nut 116 and confine the lubricant to prevent it from leaking out. Compared to a sliding screw that does not use balls, the ball screw 104 is easier to maintain a small axial clearance, preventing excessively large drive torque. Furthermore, the ball screw 104 has a longer lifespan due to reduced wear. For the circulation of the spheres 120, any of structures such as a return pipe type, a deflector type, an end cap type, etc. may be adopted.

[0014] The lead screw nut 118 is adjacent to the ball nut 116 on the inner surface of its front half that faces the caliper 129, and is adjacent to the rotor 112 on the outer surface of its front half. Because the rotor 112 is connected adjacent to the outer surface of the front half of the lead screw nut 118, the motor 102 is located generally close to the portion where the actuator 101 is attached to the caliper 129. Because the motor 102 has a relatively large load, it becomes increasingly vulnerable to vibration as it moves away from the portion where the actuator 101 is attached to the caliper 129. In this embodiment, the motor 102 is located close to the portion where the actuator 101 and caliper 129 are attached, making it resistant to vibration.

[0015] The ball nut 116 and the lead screw nut 118 are connected and operate as a unit by a pin 122 inserted perpendicular to the rotational plane of the rotor 112. A non-circular guide hole 123 is formed in the rear half of the ball screw 104. One end of a ball screw guide 124 is fitted into this guide hole 123, and the other end of the ball screw guide 124 is fixed relative to a housing 126. The rotor 112 is fixed to the lead screw nut 118. The rotational force of the rotor 112 is transmitted to the ball nut 116 via the lead screw nut 118. Because the ball screw 104 is prevented from rotating by the ball screw guide 124, the rotational force transmitted to the ball nut 116 generates a braking force that moves the ball screw 104 in a linear direction along the ball screw guide 124. In another embodiment, the ball nut 116 and the lead screw nut 118 may be configured as a single unit.

[0016] In this embodiment, the motor 102 is disposed 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 twisting that occurs when the rotational motion of the motor 102 is converted into linear motion via the lead nut 118, the ball nut 116, and the ball screw 104. For this reason, this embodiment has the advantage that a small load is applied to the bearings 146 and 148 that support the lead nut 118.

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

[0018] The braking force applying piston 108 presses against the back plate 132 to press the friction pads 134 fixed to the back plate 132 against the brake disc 136 .

[0019] A parking brake 138 is disposed on 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 other is connected to the parking mechanism 142. When the parking brake is operated, the parking mechanism 142 pulls the connected lining joint 144, bringing the band-shaped lining 140 into close contact with the screw nut 118 and generating 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 , allowing the screw nut 118 to rotate smoothly relative to the housing 126 .

[0021] The position sensor 150 is disposed around a portion of the screw nut 118 where the ball screw guide 124 is exposed. The position sensor 150 is fixed to the screw nut 118 with a bolt 153. The position sensor 150 detects the rotation angle of the screw nut 118 relative to the ball screw 104 or the ball screw guide 124.

[0022] In this embodiment, the motor 102 is located at the front half of the actuator 101, and the position sensor 150 is located at the rear half. The motor 102 and the position sensor 150 are located far enough apart to minimize the influence of noise generated in the motor 102 on the position sensor 150. In addition, a printed circuit board (PCB) (not shown) including a control circuit is located at the rear end of the actuator 101 for maintenance purposes, minimizing the influence of noise generated in the motor 102 on the control circuit.

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

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

[0025] Fig. 3 is a structural diagram of an adapter 128 according to an embodiment of the present invention, and Fig. 4 is an exploded view of the adapter 128 shown in Fig. 3. As shown in Fig. 3, the adapter 128 includes a connection pin 302, an adapter bracket 304, and a pressing portion 306.

[0026] The connection 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 rotation lever 106 moves. The adapter bracket 304 has a connection hole 402, which is rotatably disposed around the connection pin 302. Therefore, the adapter bracket 304 can rotate around the connection pin 302 within a predetermined angle range relative to the ball screw 104. The pressing portion 306 is attached to the adapter bracket 304 on the side in the direction in which the braking force is applied, and applies the braking force to the mounting portion 156 of the rotation lever 106. The pressing portion 306 has a shape corresponding to the mounting portion 156 so that it does not come off from the mounting portion 156 when the braking force is applied or released. For example, if the mounting portion 156 is a recess having a hemispherical shape, the pressing portion 306 is a protrusion having a hemispherical shape with a diameter slightly smaller than that of the hemispherical shape of the mounting portion 156.

[0027] In another embodiment, the cross sections of the pressing portion and the mounting portion may be non-circular (e.g., polygonal) to prevent the pressing portion from rotating around the axis of rotation in the direction in which the braking force is applied on the mounting portion. In this case, it is not necessary to separately provide the ball screw guide 124 to prevent the ball screw 104 from rotating.

[0028] 4, the load sensor 404 may be disposed on the adapter bracket 304 so as to be parallel to the direction in which the braking force is applied. The load sensor 404 receives the 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, together with the rotation angle value measured by the position sensor 150, is used to control the electric motor 102.

[0029] The rotating lever 106 serves to amplify the braking force transmitted from the ball screw 104. Therefore, if a load sensor is provided downstream of the rotating lever 106 during the braking force transmission process (e.g., at the braking force application piston 108 inside the caliper 129), the range of loads to be measured will be wider. This makes the appropriate load sensor larger and more difficult to install, reducing measurement accuracy and making it difficult to control the electric motor 102. If the load sensor 404 is provided in the adapter 128 located upstream of the rotating lever 106 during the braking force transmission process, the load sensor can be reduced in size, making it easier to install, and ensuring sufficient measurement accuracy, allowing for appropriate control of the electric motor 102.

[0030] The adapter bracket 304 has a U-shape so that it can rotate around the front end of the ball screw 104. The adapter bracket 304 has a front wall 406 and two side walls 408. Connection holes 402 are formed in opposing positions on the two side walls 408. The connection holes 402 are formed in the side walls 408 so that the front end 410 of the ball screw 104 is located a predetermined distance away from the front wall 406. This distance determines the maximum rotation angle that 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 distance between the front wall 406 and the front end 410 of the ball screw 104 so that the pressing portion 306 does not come off the mounting portion 156 while applying a braking force. In addition, the maximum rotation angle of the adapter bracket 304 relative to the ball screw 104 can be adjusted by providing the connection pin 302 and / or the adapter bracket 304 with a special shape (e.g., a protrusion that causes interference). There is also an advantage that the assembly of the brake system can be improved by adjusting the maximum rotation angle.

[0031] The pressing part 306 is connected to the adapter bracket 304 by fastening screws, which makes assembly and replacement easy.

[0032] FIG. 5 is a structural diagram of a ball screw 104 according to an embodiment of the present invention, and FIG. 6 is a structural diagram of the ball screw 104 taken along line A-A' in FIG. 5. As shown in the figure, the ball screw 104 includes a front end 502, a screw portion 504, and a rear end 506. The front end 502 is a portion that presses the rotation lever 106. The screw portion 504 is a portion that is fastened to the ball nut 116 and the screw nut 118. A guide hole 508 having a non-circular cross section is formed inside the rear half of the ball screw 104 (from the rear end 506 to approximately the center). As shown in FIG. 5, for ease of processing and smooth movement, the guide hole 508 preferably has an elliptical cross section. Alternatively, the guide hole 508 may have a polygonal cross section, such as a triangular or rectangular shape.

[0033] 7 is a diagram illustrating a state in which a ball screw guide 124 according to an embodiment of the present invention is fitted into the ball screw 104 shown in FIG. 6. The ball screw guide 124 is fitted into the guide hole 508 to prevent rotation of the ball screw 104. The ball screw guide 124 includes 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 accurately prevent rotation. The head portion 704 is formed integrally with the fitting portion 702 and is fixed to the housing 126 or the housing cover 154.

[0034] 8 is a structural diagram of the band-shaped lining 140 of the parking brake device 138 according to one embodiment of the present invention. As shown in FIG. 8, the band-shaped lining 140 includes a back plate 802. The back plate 802 may be made of an elastic material, for example, a metal. In the absence of external force, the back plate 802 is configured in a circular shape with a cross section having a larger diameter than 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 back plate 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 activated, the parking mechanism 142 pulls the connected lining joint 144, bringing the back plate 802 into close contact with 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 the lining joint and there is no external force, the back plate 802 returns to its original state due to its elasticity, and no friction occurs between the screw nut 118 and the band-shaped lining 140.

[0036] The band-shaped lining 140 may include friction pads 804 fixed to the inner surface of the back plate 802. The friction pads 804 increase the frictional force of the band-shaped lining 140. To prevent contamination of the ball screw integrated motor actuator 101, the friction pads 804 are preferably made of a material that generates little dust due to friction. Furthermore, to prevent contamination due to dust generated by the friction pads 804, seals 158 and 160 may be provided in front of and behind the band-shaped lining 140 between the housing 126 and the lead screw nut 118. Furthermore, exhaust holes (not shown) for exhausting dust may be formed in the housing 126 between the seals 158 and 160.

[0037] Fig. 9 is a structural diagram of a portion of the ball screw integrated motor actuator 101 provided with the band-shaped lining 140 shown in Fig. 8. In Fig. 9, the screw nut 118 is shown with the upper half cut away for better understanding.

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

[0039] The electric motor 1002 includes 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 its front (the direction in which the braking force is applied or the brake disc direction) and to a lead screw nut 1018 at its rear. The ball screw 1004 is provided with a ball 1020 between it and the ball nut 1016. The ball 1020 is inserted between the ball screw 1004 and the ball nut 1016 and performs a rolling motion to transmit power between the ball screw 1004 and the ball nut 1016. Seals (not shown) are provided at the front and rear ends of the ball nut 1016. The seals prevent foreign matter from entering between the ball screw 1004 and the ball nut 1016 and confine the lubricant to prevent it from leaking out. The ball screw 1004 is easier to maintain a small axial clearance compared to a sliding screw that does not use balls, preventing excessively large drive torque. Furthermore, the ball screw 1004 has a longer lifespan due to reduced wear. For the circulation of the spheres 120, any of structures such as a return pipe type, a deflector type, an end cap type, etc. may be adopted.

[0041] The screw nut 1018 has a front half 1018a having a first diameter and a rear half 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 half 1018a and adjacent to the rotor 1012 on the outer surface. The ball screw 1004 is fitted into the rear half 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 operate as a unit by a pin 1022 inserted in a direction perpendicular to the rotational 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. The ball screw 1004 is prevented from rotating by the mounting portion 156 of the rotation lever (106 in FIG. 1), so that the rotational force transmitted to the ball nut 1016 causes the ball screw 1004 to generate a braking force that moves longitudinally along the screw nut 1018.

[0042] An adapter 128 may be disposed 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 a caliper 129 via a bearing 131. The rotating lever 106 rotates due to the linear braking force generated in the ball screw 1004. While rotating, the rotating lever 106 presses the pressing member 130 nonlinearly to amplify the braking force, and transmits the amplified braking force to the braking force application piston 108.

[0043] The bearings 1046, 1048, and 1050 allow the screw nut 1018 to rotate smoothly relative to the housings 1025 and 1026. The bearing 1046 supports the screw nut 1018 at a front portion thereof in a direction perpendicular to the axial direction Z, and the bearing 1048 supports the screw nut 1018 at a rear portion thereof. The bearing 1050 is configured as a thrust bearing and supports the reaction force of the screw nut 1018 at an intermediate portion thereof in the longitudinal direction Z, allowing the screw nut 1018 to rotate.

[0044] 1 is after the force is boosted by the rotary lever 106, so the range of the measured load is wide, but the part at motor actuator 101 is before the force is boosted by the rotary lever 106, so the range of the measured load is narrow. If the range of the 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 consisting of a load cell is disposed between the bearing 1050 and the housing 1026. The load sensor 1052 measures the reaction force generated when the friction pad 134 presses against the brake disc 136, which is transmitted via the screw nut 1018, in order to measure the load (braking force) applied to the brake disc 136.

[0046] The operating distance of the rotating 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 were controlled by controlling the operating distance (displacement) of the rotating lever 106, the driver would not be able to generate a consistent braking force as desired. To ensure that the motor actuator 1000 always produces a consistent output, the output load of the ball screw 1004 is directly measured by the load sensor 1052, regardless of the operating distance of the rotating lever 106, for load feedback control. A thrust bearing 1050 is assembled to the lower end of the lead nut 1018, and a load sensor 1052 is assembled to the lower end of the thrust bearing 1050. Therefore, the reaction force of the piston 108 received by the ball screw 1004 is transmitted to the load sensor 1052 via the lead nut 1018 and the thrust bearing 1050 without loss.

[0047] According to this embodiment, the range of loads to be measured is narrow, so the load sensor is small and easy to attach. Also, the accuracy of the load sensor is high, making it easy to perform feedback control using the load value.

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

[0049] The position sensor 1056 is disposed at the rear end of the screw nut 1018, and measures the position of the ball screw 1004 by measuring the degree to which the screw nut 1018 has rotated relative to the housing cover 1054. The position sensor 1056 is disposed at a sufficient distance from the motor 1002, thereby minimizing the effect of noise generated in the motor 1002. Furthermore, since a printed circuit board (PCB) (not shown) for control circuits and the like is located at the rear end of the actuator 1000 for maintenance purposes, it is possible to minimize the effect of noise generated in the motor 1002 on the control circuit. Furthermore, since the position sensor 1056 is disposed near the printed circuit board (PCB), it is easy to route wiring.

[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. FIG. 11 is a structural 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. A coil 1110 is disposed inside the stator 1102, and a torque spring 1112 is disposed to bias the armature 1104. Electric 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. Therefore, the rotor 1106 rotates together with the screw nut 1018. The stator 1102 is fixed to the housings 1025 and 1026. Hexagon socket head bolts 1118 are fastened to the stator 1102, the armature 1104, and the plate 1108.

[0051] During braking, power (electricity) is supplied to the stator 1010, causing the rotor 1012 to rotate and rotate the lead screw nut 1018. The lead screw nut 1018, connected to the ball nut 1016, pushes the brake rotation lever 106, which is connected to the ball screw 1004. The rotation lever 106 then pushes the brake piston 108, bringing the friction pad 134 into close contact with the brake disc 136 to apply braking. If the supply of power (electricity) is interrupted while the rotation lever 106 is applying force to the piston 108, the ball screw 1004 moves 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 it was applying to the piston 108 even when the supply of power (electricity) is interrupted. Therefore, in this embodiment, a clutch disc brake 1070 is used to maintain the force applied to the piston 108. When power is not supplied to the clutch disc brake 1070, the torque spring 1112 biases the armature 1104 and rotor 1106 to fix them, thereby fixing 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 move the armature 1104 backward, releasing the restriction on the ball screw 1018.

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

[0053] The electric motor 1202 includes 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 its front (the direction in which the braking force is applied or the brake disc direction) and to a lead screw nut 1218 at its rear. The ball screw 1204 is provided with a ball 1220 between it and the ball nut 1216. The ball 1220 is inserted between the ball screw 1204 and the ball nut 1216 and performs a rolling motion, thereby transmitting power between the ball screw 1204 and the ball nut 1216. Seals (not shown) are provided at the front and rear ends of the ball nut 1216. The seals prevent foreign matter from entering between the ball screw 1204 and the ball nut 1216 and trap lubricant to prevent it from leaking out. The ball screw 1204 is easier to maintain a small axial clearance compared to a sliding screw that does not use balls, preventing excessively large drive torque. Furthermore, the ball screw 1204 has a longer lifespan due to reduced wear. For the circulation of the spheres 120, any of structures such as a return pipe type, a deflector type, an end cap type, etc. may be adopted.

[0055] The screw nut 1218 has a front half 1218a having a first diameter and a rear half 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 half 1218a and adjacent to the rotor 1212 on the outer surface. A ball screw 1204 is fitted into the rear half 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 operate as a unit by a pin 1222 inserted in a direction perpendicular to the rotational 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. The ball screw 1204 is prevented from rotating by the mounting portion 156 of the rotation lever (106 in FIG. 1), so that the rotational force transmitted to the ball nut 1216 causes the ball screw 1204 to generate a braking force that moves longitudinally along the screw nut 1218.

[0056] An adapter 128 may be disposed 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 a caliper 129 via a bearing 131. The rotating lever 106 rotates due to the linear braking force generated in the ball screw 1204. While rotating, the rotating lever 106 presses the pressing member 130 nonlinearly to amplify 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 to allow screw nut 1218 to rotate smoothly relative to housings 1225,1226.

[0058] Housing 1225 supports components in the front half of actuator 1200, and housing 1226 supports components in the rear half of actuator 1200. Housing cover 1254 seals housing 1226 to prevent the components inside housings 1225 and 1226 from getting dirty from the outside.

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

[0060] In this embodiment, the motor actuator 1200 further includes a parking brake device. The parking brake device is composed of a worm wheel 1270 and a worm adjuster 1272. The worm adjuster 1272 includes a worm gear 1272a that is fastened to the worm wheel 1270, and a handle portion 1272b that has one end attached to the central axis of the worm gear 1272a and the other end 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 lead nut 1218. The worm wheel 1270 meshes with the worm gear 1272a. One end of the handle portion 1272b is attached to the central axis of the worm gear 1272a, so that 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 lead screw nut 1218. The lead screw nut 1218 is connected to the ball nut 1216 and therefore pushes the brake rotation lever 106, which is connected to the ball screw 1204. The rotation lever 106 then pushes the brake piston 108, bringing the friction pad 134 and the brake disc 136 into close contact, thereby braking. If the supply of power (electricity) is interrupted while the rotation lever 106 is applying force to the piston 108, the ball screw 1204 moves 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. In order 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 supply of power (electricity) is interrupted. Therefore, reverse rotation of the screw nut 1218 is prevented via the worm wheel 1270 and the worm adjuster 1272, thereby preventing backward movement of the ball screw 1204. Furthermore, when the power (electricity) supply is cut off, the worm adjuster 1272 allows the handle portion 1272b to be manually rotated to adjust the position of the ball screw 1204, thereby enabling replacement (maintenance) of the friction pad 134 and releasing the drag state of the brake disc 136 and the friction pad 134.

[0062] The above-described embodiments of the electromechanical disc brake of the present invention are merely illustrative, and those skilled in the art will appreciate that various modifications and equivalent embodiments may be adopted. Therefore, it should be clearly understood that the present invention is not limited to the embodiments described in the above detailed description. Therefore, the true technical scope of protection of the present invention should be determined by the technical ideas of the appended claims. Furthermore, the present invention should be understood to include all modifications, equivalents, and alternatives within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. In a motor actuator used in an electromechanical disc brake, an electric motor for generating rotational force; a screw nut connected to the electric motor and rotating therewith; a ball nut disposed adjacent to the inner surface of the screw nut and fixed to the screw nut; a ball screw that is fastened to the ball nut to convert a rotational force generated in the electric motor into a braking force in a linear direction; A motor actuator comprising:

2. The motor actuator according to claim 1 , further comprising a load sensor for measuring a load applied from the screw nut.

3. The motor actuator according to claim 1 , further comprising a parking brake device that applies a parking braking force to the screw nut.

4. 4. The motor actuator of claim 3, wherein the parking brake device comprises a clutch disc brake.

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