Motor actuator for electromechanical disc brake

Abstract

The present invention relates to a motor actuator for an electromechanical disc brake, the actuator directly measuring a load generated in the motor actuator, and utilizing the load for brake control. The motor actuator of the present invention comprises: an electric motor for generating rotational force; a screw nut connected to the electric motor so as to rotate together therewith; a ball nut provided adjacent to the inner surface of the screw nut and fixed to the screw nut; a ball screw fastened to the ball nut so as to convert the rotational force generated by the electric motor into braking force in the linear direction; and a load sensor for measuring a load applied from the screw nut.

Description

Motor actuator for electromechanical disc brake

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

[0002] Various types of electromechanical disc brakes are being developed for commercial vehicles. Electromechanical disc brakes utilize electric motors as actuators, requiring a transmission mechanism that converts the rotational force generated by the electric motor into linear braking force and then amplifies (powers up) the force by decelerating the brakes. Planetary gears are widely used for this transmission mechanism, but their high cost and complex structure are problematic due to the need for precision components. Therefore, electromechanical disc brakes utilizing ball screws are being proposed as cost-effective, simple, and compact.

[0003] The present invention aims to provide a motor actuator for an electromechanical disc brake that directly measures a load generated by the motor actuator for use in brake control.

[0004] The present invention for achieving the above-described object is characterized by a motor actuator used in an electromechanical disc brake, comprising: an electric motor for generating rotational force; a screw nut connected to the electric motor and rotating together; a ball nut installed adjacent to the inner surface of the screw nut and fixed to the screw nut; and a ball screw connected to the ball nut for converting rotational force generated by the electric motor into a braking force in a linear direction.

[0005] Preferably, the motor actuator further comprises a load sensor that measures a load applied from the screw nut. The motor actuator further comprises a bearing that supports the screw nut while allowing rotation of the screw nut, and the load sensor is installed between the bearing and the housing of the motor actuator.

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

[0007] Preferably, the parking brake device comprises a clutch disc brake. The clutch disc brake comprises a stator having a coil and a torque spring installed thereon and attached to a housing of the motor actuator, a rotor that rotates integrally with the screw nut, an armature installed between the stator and the rotor and compressing 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 attached to the stator and does not compress the rotor.

[0008] According to the electromechanical disc brake motor actuator of the present invention having the aforementioned configuration, the brake can be controlled by directly measuring the load generated by the motor actuator. Since the range of load to be measured is small, the size of the load sensor can be reduced, making it easy to install. Furthermore, the precision of the load sensor is increased, facilitating feedback control using the load value.

[0009] Figure 1 is a configuration diagram of an electromechanical disc brake according to one embodiment of the present invention.

[0010] Fig. 2 is a cross-sectional view of the ball screw integrated motor actuator illustrated in Fig. 1.

[0011] Figure 3 is a configuration diagram of an adapter according to one embodiment of the present invention.

[0012] Figure 4 is an exploded view of the adapter shown in Figure 3.

[0013] Figure 5 is a configuration diagram of a ball screw according to one embodiment of the present invention.

[0014] Fig. 6 is a configuration diagram of a ball screw obtained by cutting along line A-A' in Fig. 5.

[0015] FIG. 7 is a drawing illustrating a state in which a ball screw guide according to one embodiment of the present invention is inserted into the ball screw illustrated in FIG. 6.

[0016] Fig. 8 is a configuration diagram of a band-shaped lining of a parking brake device according to one embodiment of the present invention.

[0017] Fig. 9 is a schematic diagram of a part of a ball screw integrated motor actuator having the band-shaped lining shown in Fig. 8 installed.

[0018] Fig. 10 is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention.

[0019] Fig. 11 is a configuration diagram of the clutch disc brake shown in Fig. 10.

[0020] Fig. 12 is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention.

[0021] To fully understand the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention may be modified in various 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 with average knowledge in the art. Therefore, the shapes of elements in the drawings may be exaggerated to emphasize a clearer description. It should be noted that in each drawing, the same parts are sometimes depicted with the same reference numerals. Detailed descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted.

[0022] FIG. 1 is a configuration diagram of an electromechanical disc brake (100) according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view of a ball screw-integrated motor actuator (101) illustrated in FIG. 1. As illustrated, the electromechanical disc brake (100) includes a ball screw-integrated motor actuator (101), a rotary lever (106), and a braking force applying piston (108). The actuator (101) includes an electric motor (102) and a ball screw (104).

[0023] The electric motor (102) has a stator (110) and a rotor (112), and generates rotational force when power is supplied from a power source (not shown).

[0024] 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) has 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 transmits power between the ball screw (104) and the ball nut (116) by rolling motion. Sealing parts (not shown) are installed at the front and rear ends of the ball nut (116). The sealing parts prevent foreign substances from entering between the ball screw (104) and the ball nut (116) and serve to trap lubricant and prevent it from leaking out. Compared to a sliding screw that does not use a sphere, the ball screw (104) is easy to maintain a small axial clearance and prevents the driving torque from becoming extremely large. In addition, since wear is reduced, the lifespan is also extended. For the circulation of the sphere (120), structures such as the return pipe type, the deflector type, and the end cap type are all possible.

[0025] The screw nut (118) is adjacent to the ball nut (116) on the inner side of the front end facing the caliper (129), and is adjacent to the rotor (112) on the outer side of the front end. Since the rotor (112) is adjacent and connected on the outer side of the front end of the screw nut (118), the motor (102) is positioned closer to the part where the actuator (101) is attached to the caliper (129). Since the motor (102) has a relatively large load, the farther away the motor (102) is from the part where the actuator (101) is attached to the caliper (129), the more vulnerable it becomes to vibration. The present embodiment is resistant to vibration because the motor (102) is positioned closer to the part where the actuator (101) and the caliper (129) are attached.

[0026] The ball nut (116) and the screw nut (118) are connected and operate as one unit by a pin (122) inserted in a direction perpendicular to the rotational surface of the rotor (112). A guide hole (123) having a non-circular shape is formed inside the latter half of the ball screw (104). One end of the ball screw guide (124) is inserted into the guide hole (123), and the other end of the ball screw guide (124) is relatively fixed with respect 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) through the screw nut (118). Since the ball screw (104) is prevented from rotating by the ball screw guide (124), the ball screw (104) generates a braking force to move in a straight direction along the ball screw guide (124) by the rotational force transmitted to the ball nut (116). In another embodiment, the ball nut (116) and the screw nut (118) may be formed as one piece.

[0027] In the present embodiment, the motor (102) is positioned adjacent to the portion where the ball nut (116) is coupled to the ball screw (104) via the sphere (120). Therefore, the rotational motion of the motor (102) is converted into linear motion via the screw nut (118), the ball nut (116), and the ball screw (104), with relatively little twisting. For this reason, the present embodiment has the advantage of a small load being applied to the bearings (146, 148) supporting the screw nut (118).

[0028] An adapter (128) is installed at the front end of the ball screw (104). The linear braking force generated by the ball screw (104) is transmitted to the rotary lever (106) via the adapter (128). The rotary lever (106) is mounted on the caliper (129) via a bearing (131). The rotary lever (106) rotates due to the linear braking force generated by the ball screw (104). The rotary lever (106) nonlinearly presses the pressure member (130) while rotating to amplify the braking force and transmits the amplified braking force to the braking force application piston (108).

[0029] The braking force application piston (108) presses the back plate (132) to press the friction pad (134) fixed to the back plate (132) against the brake disc (136).

[0030] A parking brake (138) is installed on the latter part of the outer surface of the screw nut (118). The parking brake (138) has 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 joints (144) to bring the band-shaped lining (140) into close contact with the screw nut (118), thereby generating a braking force for parking.

[0031] The bearing (146) supports the front of the screw nut (118) and the bearing (148) supports the rear of the screw nut (118) to allow the screw nut (118) to rotate smoothly with respect to the housing (126).

[0032] The position sensor (150) is installed around the exposed portion of the ball screw guide (124) in the screw nut (118). The position sensor (150) is fixed to the screw nut (118) by a bolt (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).

[0033] In this embodiment, the motor (102) is positioned at the front end of the actuator (101) and the position sensor (150) is positioned at the rear end. The distance between the motor (102) and the position sensor (150) is sufficiently spaced so that noise generated from the motor (102) can be minimized from affecting the position sensor (150). In addition, since a PCB board (not shown) for a control circuit or the like is positioned at the rear end of the actuator (101) for maintenance purposes, noise generated from the motor (102) can be minimized from affecting the control circuit.

[0034] The load sensor (152) measures the reaction force generated when the friction pad (134) presses the brake disc (136) by receiving it from the screw nut (118) in order to measure the load (braking force) applied to the brake disc (136).

[0035] The housing cover (154) seals the housing (126) to protect the components inside the housing (126) from contamination from the outside.

[0036] Fig. 3 is a configuration diagram of an adapter (128) according to one embodiment of the present invention, and Fig. 4 is an exploded view of the adapter (128) illustrated in Fig. 3. As illustrated, the adapter (128) has a connecting pin (302), an adapter bracket (304), and a pressing portion (306).

[0037] The connecting pin (302) is inserted into the front end of the ball screw (104) in a direction perpendicular to the direction of braking force application (or the direction of movement of the ball screw (104)) and the direction of movement of the rotary lever (106). The adapter bracket (304) has a connecting hole (402), and the connecting hole (402) is rotatably installed in the connecting pin (302). Therefore, the adapter bracket (304) can rotate within a predetermined angular range with respect to the ball screw (104) about the connecting pin (302). The pressing portion (306) is attached to the adapter bracket (304) on the side in the direction of braking force application and applies braking force to the seating portion (156) of the rotary lever (106). The pressing portion (306) has a shape corresponding to the seating portion (156) so as not to be detached from the seating portion (156) when the braking force is applied or released. For example, if the mounting portion (156) is a concave portion having a hemispherical shape, the pressing portion (306) is a convex portion having a hemispherical shape with a diameter slightly smaller than the hemispherical shape of the mounting portion (156).

[0038] In another embodiment, the cross-sections of the compression member and the mounting member may be non-circular (e.g., polygonal) to prevent the compression member from rotating about the direction of application of the braking force to the mounting member. In this case, a separate ball screw guide (124) for preventing rotation of the ball screw (104) may not be provided.

[0039] As illustrated in FIG. 4, a load sensor (404) may be installed on the adapter bracket (304) parallel to the direction in which the braking force is applied. The load sensor (404) receives a reaction force of the braking force via the compression member (306). Through this configuration, the adapter (128) can measure the braking force (or load) applied to the brake disc (136). The load value measured through the adapter (128) is utilized to control the electric motor (102) together with the rotation angle value measured by the position sensor (150).

[0040] The rotary lever (106) amplifies the braking force transmitted from the ball screw (104). Therefore, if a load sensor is installed at a location downstream of the rotary lever (106) during the braking force transmission process (e.g., the braking force application piston (108) inside the caliper (129)), the range of loads to be measured expands. This increases the size of an appropriate load sensor, making it difficult to install, and reduces measurement precision, making it difficult to control the electric motor (102). If the load sensor (404) is installed at an adapter (128) located upstream of the rotary lever (106) during the braking force transmission process, the size of the load sensor can be reduced, making installation easy, and ensuring sufficient measurement precision enables appropriate control of the electric motor (102).

[0041] The adapter bracket (304) has a “ㄷ” shape so as to be rotatable at the front end of the ball screw (104). The adapter bracket (304) has one front wall (406) and two side walls (408). A connecting hole (402) is formed at an opposing position in the two side walls (408). The connecting hole (402) is formed in the side wall (408) so that the front end (410) of the ball screw (104) is positioned at a predetermined distance from the front wall (406). This distance determines the maximum rotation angle at which the adapter bracket (304) can rotate about the connecting pin (302) with respect to the ball screw (104). The maximum rotation angle is set through the distance between the front wall (406) and the front end (410) of the ball screw (104) so ​​that the compression member (306) does not come off from the mounting member (156) while applying the braking force. In addition, the maximum rotation angle of the adapter bracket (304) with respect to the ball screw (104) can be adjusted by having the connecting pin (302) and / or the adapter bracket (304) have a special shape (e.g., a convex portion causing interference). There is also an advantage in that the assembling of the brake system can be improved by adjusting the maximum rotation angle.

[0042] The pressure part (306) can be easily assembled and replaced by being connected to the adapter bracket (304) using a screw fastening method.

[0043] FIG. 5 is a configuration diagram of a ball screw (104) according to one embodiment of the present invention, and FIG. 6 is a configuration diagram of a ball screw (104) obtained by cutting along line A-A' in FIG. 5. As illustrated, the ball screw (104) has a front end (502), a screw end (504), and a rear end (506). The front end (502) is a portion that presses the rotary lever (106). The screw end (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 end (from the rear end (506) to approximately the center) of the ball screw (104). As illustrated in FIG. 5, for ease of processing or smooth movement, it is preferable that the guide hole (508) have an oval cross-section. Additionally, the guide hole (508) may have a polygonal cross-section such as a triangle or square.

[0044] FIG. 7 is a drawing illustrating a state in which a ball screw guide (124) according to one embodiment of the present invention is inserted into the ball screw (104) illustrated in FIG. 6. The ball screw guide (124) is inserted into a guide hole (508) to prevent rotation of the ball screw (104). The ball screw guide (124) has an insertion portion (702) and a head portion (704). It is preferable that the insertion portion (702) have a cross-section corresponding to the guide hole (508) to prevent accurate rotation. The head portion (704) is formed integrally with the insertion portion (702) and is fixed to the housing (126) or the housing cover (154).

[0045] Fig. 8 is a configuration diagram of a band-shaped lining (140) of a parking brake device (138) according to one embodiment of the present invention. As illustrated 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, metal. In the absence of an external force, the back plate (802) is configured in a circular shape with a cross-section larger in diameter than the screw nut (118), so that no friction occurs between the screw nut (118) and the band-shaped lining (140).

[0046] The back plate (802) is provided with 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 joints (144) to press the back plate (802) toward the screw nut (118), so that the friction pad (804) presses the screw nut (118). When the parking mechanism (142) releases the force pulling the lining joints and there is no external force, the back plate (802) returns to its original state due to elasticity, so that no friction occurs between the screw nut (118) and the band-shaped lining (140).

[0047] The band-shaped lining (140) may be provided with a friction pad (804) fixed to the inner surface of the back plate (802). The friction pad (804) increases the frictional force by the band-shaped lining (140). In order to prevent contamination of the ball screw integrated motor actuator (101), the friction pad (804) is preferably made of a material that generates little dust due to friction. In addition, in order to prevent contamination by dust generated from the friction pad (804), a sealant (158) and a sealant (160) may be installed between the housing (126) and the screw nut (118), at the front and back of the band-shaped lining (140), respectively. In addition, an exhaust hole (not shown) for exhausting dust may be formed in the housing (126) between the sealant (158) and the sealant (160).

[0048] Fig. 9 is a schematic diagram of a portion of a ball screw integrated motor actuator (101) having the band-shaped lining (140) illustrated in Fig. 8 installed. In Fig. 9, the screw nut (118) is illustrated with its upper half cut off and removed for clarity.

[0049] Fig. 10 is a cross-sectional view of a ball screw integrated motor actuator (1000) according to another embodiment of the present invention. As illustrated, the actuator (1000) includes an electric motor (1002) and a ball screw (1004).

[0050] The electric motor (1002) has a stator (1010) and a rotor (1012), and generates rotational force when power is supplied from a power source (not shown).

[0051] 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) has 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 performs rolling motion to transmit power between the ball screw (1004) and the ball nut (1016). Sealing parts (not shown) are installed at the front and rear ends of the ball nut (1016). The sealing parts prevent foreign substances from entering between the ball screw (1004) and the ball nut (1016) and serve to trap lubricant and prevent it from leaking out. Compared to sliding screws that do not use a ball, the ball screw (1004) facilitates maintaining a small axial clearance and prevents excessively high driving torque. Furthermore, it has a longer lifespan due to less wear. For the circulation of the ball (120), various structures are possible, including a return pipe type, a deflector type, and an end cap type.

[0052] The screw nut (1018) has 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 inserted into the rear portion (1018b) of the screw nut (1018) so as to enable horizontal movement in the longitudinal direction. The ball nut (1016) and the screw nut (1018) are connected to each other by a pin (1022) inserted in a direction perpendicular to the rotational surface of the rotor (1012) and operate as one unit. The rotor (1012) is fixed to the screw nut (1018). The rotational force of the rotor (1012) is transmitted to the ball nut (1016) through the screw nut (1018). Since the ball screw (1004) is prevented from rotating by the mounting portion (156) of the rotary lever (106 in FIG. 1), the ball screw (1004) generates a braking force that moves longitudinally along the screw nut (1018) by the rotational force transmitted to the ball nut (1016).

[0053] An adapter (128) may be installed at the front end of the ball screw (1004). The linear braking force generated by the ball screw (1004) is transmitted to the rotary lever (106) via the adapter (128). The rotary lever (106) is mounted on the caliper (129) via a bearing (131). The rotary lever (106) rotates by the linear braking force generated by the ball screw (1004). The rotary lever (106) nonlinearly presses the pressure member (130) while rotating to amplify the braking force and transmits the amplified braking force to the braking force application piston (108).

[0054] The bearings (1046, 1048, 1050) allow the screw nut (1018) to rotate smoothly with respect to the housing (1025, 1026). The bearing (1046) supports the screw nut (1018) at the front portion of the screw nut (1018) in a direction perpendicular to the axial direction (Z), and the bearing (1048) supports the screw nut (1018) at the rear portion of the screw nut (1018). The bearing (1050) is configured as a thrust bearing, and supports the reaction force of the screw nut (1018) at the middle portion of the screw nut (1018) in the longitudinal direction (Z) and allows the screw nut (1018) to rotate.

[0055] In Fig. 1, part A is after the power supply by the rotary lever (106), so the measured load range is large, but the motor actuator (101) part is before the power supply by the rotary lever (106), so the measured load range is small. If the range of load to be measured is large, the size of the load sensor becomes large, making it difficult to install, and the precision of the load sensor decreases, making it difficult to perform feedback control using the load value.

[0056] In the motor actuator (1000), a load sensor (1052) composed of a load cell is installed between the bearing (1050) and the housing (1026). The load sensor (1052) receives and measures the reaction force generated when the friction pad (134) presses the brake disc (136) via the screw nut (1018) in order to measure the load (braking force) applied to the brake disc (136).

[0057] 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 controlling the operating distance (displacement) of the rotary lever (106), it is impossible to generate a constant braking force desired by the driver. In order to always produce a constant output from the motor actuator (1000), the output load of the ball screw (1004) is directly measured by the load sensor (1052) regardless of the operating distance of the rotary lever (106), thereby performing load feedback control. A thrust bearing (1050) is assembled at the bottom of the screw nut (1018), and a load sensor (1052) is assembled at the bottom of the thrust bearing (1050), so that the reaction force of the piston (108) received from the ball screw (1004) is transmitted to the load sensor (1052) without loss via the screw nut (1018) and the thrust bearing (1050).

[0058] In this embodiment, since the load range to be measured is small, the size of the load sensor is reduced, making it easy to install. In addition, the precision of the load sensor is increased, making it easy to perform feedback control using load values.

[0059] The housing (1025) supports the components of the front part of the actuator (1000), and the housing (1026) supports the components of the back part of the actuator (1000). The housing cover (1054) seals the housing (1026) to protect the components inside the housing (1025, 1026) from contamination from the outside.

[0060] The position sensor (1056) is installed 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 measure the position of the ball screw (1004). Since the position sensor (1056) is installed at a sufficient distance from the motor (1002), the influence of noise generated from the motor (1002) can be minimized. In addition, since a PCB board (not shown) for a control circuit or the like is located at the rear end of the actuator (1000) for maintenance purposes, the influence of noise generated from the motor (1002) on the control circuit can be minimized. In addition, since the position sensor (1056) is placed close to the PCB board, wiring, etc. becomes easy.

[0061] The present embodiment has a clutch disc brake (1070) as a parking device. The clutch disc brake (1070) is installed on the outer surface of the latter part of the screw nut (1018). Fig. 11 is a configuration diagram of the clutch disc brake (1070). As shown, the clutch disc brake (1070) has a stator (1102), an armature (1104), a rotor (1106), and a plate (1108). The stator (1102) has a coil (1110) installed therein, and a torque spring (1112) installed to compress the armature (1104). Power can be supplied to the coil (1110) through a lead wire (1114). A rotor hub (1116) is installed 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). Accordingly, the rotor (1106) rotates together with the screw nut (1018). The stator (1102) is fixed to the housing (1025, 1026). Hexagonal socket head bolts (1118) are fastened to the stator (1102), the armature (1104), and the plate (1108).

[0062] When braking, power (electricity) is supplied to the stator (1010), and the rotor (1012) rotates to rotate the screw nut (1018). Since the screw nut (1018) is connected to the ball nut (1016), it pushes the rotary lever (106) of the brake connected to the ball screw (1004), and the rotary lever (106) pushes the piston (108) of the brake to bring the friction pad (134) and the brake disc (136) into close contact, thereby performing braking. When the supply of power (electricity) is cut off while the rotary lever (106) is applying force to the piston (108), the ball screw (1004) moves slightly backward due to the reaction force of the rotary lever (106). At this time, the ball screw (1004) loses some of the force that it was applying to the piston (108). In order for the actuator (1000) to perform the parking brake function, the force applied to the piston (108) must be maintained even when the power (electricity) supply is cut off. Therefore, in order to maintain the force applied to the piston (108), the present embodiment uses a clutch disc brake (1070). When power is not supplied to the clutch disc brake (1070), the torque spring (1112) pressurizes and fixes the armature (1104) and the 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 armature (1104) is retracted by the stator (1102) and coil (1110) of the clutch disc brake (1070), thereby releasing the restraint of the ball screw (1018).

[0063] Fig. 12 is a cross-sectional view of a ball screw integrated motor actuator (1200) according to another embodiment of the present invention. As illustrated, the actuator (1200) includes an electric motor (1202) and a ball screw (1204).

[0064] The electric motor (1202) has a stator (1210) and a rotor (1212), and generates rotational force when power is supplied from a power source (not shown).

[0065] 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) has 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 performs rolling motion to transmit power between the ball screw (1204) and the ball nut (1216). Sealing parts (not shown) are installed at the front and rear ends of the ball nut (1216). The sealing parts prevent foreign substances from entering between the ball screw (1204) and the ball nut (1216) and serve to trap lubricant and prevent it from leaking out. Compared to sliding screws that do not use a ball, the ball screw (1204) facilitates maintaining a small axial clearance and prevents excessively high driving torque. Furthermore, it has a longer lifespan due to less wear. For the circulation of the ball (120), various structures are possible, including a return pipe type, a deflector type, and an end cap type.

[0066] The screw nut (1218) has 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 inserted into the rear portion (1218b) of the screw nut (1218) so as to enable horizontal movement in the longitudinal direction. The ball nut (1216) and the screw nut (1218) are connected to each other by a pin (1222) inserted in a direction perpendicular to the rotational surface of the rotor (1212) and operate as one unit. The rotor (1212) is fixed to the screw nut (1218). The rotational force of the rotor (1212) is transmitted to the ball nut (1216) through the screw nut (1218). Since the ball screw (1204) is prevented from rotating by the mounting portion (156) of the rotary lever (106 in FIG. 1), the ball screw (1204) generates a braking force that moves longitudinally along the screw nut (1218) by the rotational force transmitted to the ball nut (1216).

[0067] An adapter (128) may be installed at the front end of the ball screw (1204). The linear braking force generated by the ball screw (1204) is transmitted to the rotary lever (106) via the adapter (128). The rotary lever (106) is mounted on the caliper (129) via a bearing (131). The rotary lever (106) rotates due to the linear braking force generated by the ball screw (1204). The rotary lever (106) nonlinearly presses the pressure member (130) while rotating to amplify the braking force and transmits the amplified braking force to the braking force application piston (108).

[0068] The bearing (1246) supports the front of the screw nut (1218) and the bearing (1248) supports the rear of the screw nut (1218) to allow the screw nut (1218) to rotate smoothly relative to the housing (1225, 1226).

[0069] The housing (1225) supports the components of the front part of the actuator (1200), and the housing (1226) supports the components of the back part of the actuator (1200). The housing cover (1254) seals the housing (1226) to prevent the components inside the housings (1225, 1226) from being contaminated from the outside.

[0070] The thrust bearing (1250) rotates while supporting the reaction force of the screw nut (1218). The load sensor (1252) composed of a load cell receives and measures the reaction force generated when the friction pad (134) presses the brake disc (136) through the screw nut (1218) and the thrust bearing (1250) in order to measure the load (braking force) applied to the brake disc (136). The position sensor (1256) is installed at the rear end of the screw nut (1218) and measures the degree to which the screw nut (1218) rotates relative to the housing cover (1254) to measure the position of the ball screw (1204). Since the position sensor (1256) is installed at a sufficient distance from the motor (1202), the influence of noise generated from the motor (1202) can be minimized. In addition, since a PCB board (not shown) for control circuits and the like is located at the rear end of the actuator (1200) for maintenance purposes, noise generated from the motor (1202) can be minimized from affecting the control circuit. In addition, since the position sensor (1256) is located close to the PCB board, wiring, etc. becomes easy.

[0071] 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 connected 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 latter half of the screw nut (1218). The worm wheel (1270) is gear-connected to the worm gear (1272a). Since one end of the handle portion (1272b) is connected 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).

[0072] When braking, power (electricity) is supplied to the stator (1210), and the rotor (1212) rotates to rotate the screw nut (1218). Since the screw nut (1218) is connected to the ball nut (1216), it pushes the rotary lever (106) of the brake connected to the ball screw (1204), and the rotary lever (106) pushes the piston (108) of the brake to bring the friction pad (134) and the brake disc (136) into close contact, thereby performing braking. When the supply of power (electricity) is cut off while the rotary lever (106) is applying force to the piston (108), the ball screw (1204) moves slightly backward due to the reaction force of the rotary lever (106). At this time, the ball screw (1204) loses some of the force that it was applying to the piston (108). In order for the actuator (1200) to perform the parking brake function, the force applied to the piston (108) must be maintained even when the power (electricity) supply is cut off. Therefore, the reverse rotation of the screw nut (1218) is prevented through the worm wheel (1270) and the worm adjuster (1272), thereby preventing the backward movement of the ball screw (1204). In addition, the worm adjuster (1272) can manually rotate the handle portion (1272b) to adjust the position of the ball screw (1204) when the power (electricity) supply is cut off, thereby replacing (maintaining) the friction pad (134) and releasing the drag state of the brake disc (136) and the friction pad (134).

[0073] The embodiments of the electromechanical disc brake of the present invention described above are merely exemplary, and those skilled in the art will readily appreciate that various modifications and equivalent other embodiments are possible. Therefore, it will be readily understood that the present invention is not limited to the forms mentioned in the detailed description above. Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit 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 that generates rotational force, A screw nut that is connected to the above electric motor and rotates together with it, A ball nut installed adjacent to the inner surface of the screw nut and fixed to the screw nut; A ball screw that is connected to the above ball nut and converts the rotational force generated by the above electric motor into a linear braking force. A motor actuator characterized by having:

2. In paragraph 1, A motor actuator further characterized by comprising a load sensor that measures a load applied from the screw nut.

3. In paragraph 1, A motor actuator further characterized by comprising a parking brake device that applies parking braking force to the screw nut.

4. In paragraph 3, A motor actuator characterized in that the above parking brake device comprises a clutch disc brake.

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