Motor Actuator for Electromechanical Disc Brakes with Clutch Disc Brake as Parking Device

Abstract

The present invention relates to a ball screw integrated motor actuator having a parking brake device and an electromechanical disc brake equipped with the same. The motor actuator of the present invention comprises an electric motor that generates rotational force, a screw nut connected to the electric motor and rotating 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 coupled to the ball nut and converts the rotational force generated by the electric motor into a straight-direction braking force, and a parking brake device that has a clutch disc brake and applies a parking braking force to the screw nut.

Description

Technology Field

[0001] The present invention relates to a motor actuator, and more particularly to a motor actuator for an electromechanical disc brake equipped with a clutch disc brake as a parking device. Background Technology

[0002] Various types of electromechanical disc brakes are being developed in the commercial vehicle sector. Since electromechanical disc brakes use electric motors in the actuators, they require a transmission mechanism that converts the rotational force generated by the electric motor into linear braking force and amplifies (amplifies) the braking force by decelerating it. Planetary gears are widely used for this transmission mechanism, but they have the problem of being expensive and having a complex structure due to the need for precision components. Therefore, electromechanical disc brakes that use ball screws to be cost-effective, simple in structure, and compact are being proposed. Prior art literature

[0003] Registered Patent No. 2363665 (Vehicle Disc Brake Actuator) Published Patent No. 2020-0142011 (Electromechanical Brake and its Electric Actuator) The problem to be solved

[0004] The present invention aims to provide a motor actuator for an electromechanical disc brake capable of parking (parking braking) by mechanical operation even when power is cut off. means of solving the problem

[0005] The present invention for achieving the aforementioned purpose is characterized in that the motor actuator used in an electromechanical disc brake comprises: an electric motor that generates rotational force; a screw nut connected to the electric motor and rotating 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 coupled to the ball nut and converting the rotational force generated by the electric motor into a straight-direction braking force; and a parking brake device having a clutch disc brake and applying a parking braking force to the screw nut.

[0006] Preferably, the clutch disc brake comprises a stator attached to the housing of the motor actuator, on which a coil and a torque spring are installed; a rotor that rotates integrally with the screw nut; an armature installed between the stator and the rotor and which presses 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 press the rotor. Effects of the invention

[0007] According to the present invention with the above-described configuration, when the supply of power (electricity) is cut off while the ball screw is in the forward (forced) state, it is possible to prevent the ball screw from rotating in reverse and losing the force to apply force to the mating object (caliper lever or piston). Brief explanation of the drawing

[0008] FIG. 1 is a diagram showing the configuration of an electromechanical disc brake according to one embodiment of the present invention. Figure 2 is a cross-sectional view of the ball screw integrated motor actuator shown in Figure 1. FIG. 3 is a configuration diagram of an adapter according to one embodiment of the present invention. Figure 4 is an exploded view of the adapter shown in Figure 3. FIG. 5 is a diagram showing the configuration of a ball screw according to one embodiment of the present invention. Figure 6 is a diagram of a ball screw obtained by cutting line A-A' in Figure 5. FIG. 7 is a drawing illustrating the state in which a ball screw guide according to one embodiment of the present invention is inserted into the ball screw shown in FIG. 6. FIG. 8 is a configuration diagram of a band-type lining of a parking brake device according to one embodiment of the present invention. Figure 9 is a diagram showing the configuration of a part of a ball screw integrated motor actuator with a band-type lining installed as shown in Figure 8. FIG. 10 is a cross-sectional view of a ball screw integrated motor actuator according to another embodiment of the present invention. Figure 11 is a configuration diagram of the clutch disc brake illustrated in Figure 10. Specific details for implementing the invention

[0009] To fully understand the present invention, preferred embodiments of the invention are described with reference to the accompanying drawings. Embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be interpreted 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. Accordingly, the shapes of elements in the drawings may be exaggerated to emphasize clearer explanations. It should be noted that in each drawing, identical components may be depicted with the same reference numeral. Detailed descriptions of known functions and configurations that are deemed to unnecessarily obscure the essence of the present invention are omitted.

[0010] 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) shown in FIG. 1. As shown, the electromechanical disc brake (100) comprises a ball screw integrated motor actuator (101), a rotary lever (106), and a braking force applying piston (108). The actuator (101) comprises an electric motor (102) and a ball screw (104).

[0011] The electric motor (102) is equipped with a stator (110) and a rotor (112) and generates rotational force when power is supplied from a power source (not shown).

[0012] The ball screw (104) is fastened to the ball nut (116) at the front (direction of braking force application or brake disc direction) and to the screw nut (118) at the 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 rolling motion to transmit power between the ball screw (104) and the ball nut (116). A sealing part (not shown) is installed at the front and rear ends of the ball nut (116). The sealing part prevents foreign matter from entering between the ball screw (104) and the ball nut (116) and serves to trap lubricant to prevent leakage. Compared to a sliding screw that does not use a ball, the ball screw (104) makes it easier to maintain a small axial clearance and prevents the driving torque from becoming extremely large. In addition, wear is reduced, which extends the lifespan. For the circulation of the sphere (120), structures such as a return pipe type, a deflector type, and an end cap type are all possible.

[0013] The screw nut (118) is adjacent to the ball nut (116) on the inner surface of the front portion and adjacent to the rotor (112) on the outer surface. The ball nut (116) and the screw nut (118) are connected by a pin (122) inserted in a direction perpendicular to the rotational plane of the rotor (112) and operate as a single unit. A guide hole (123) in a non-circular shape is formed inside the rear portion of the ball screw (104). One end of the ball screw guide (124) is inserted into this guide hole (123), and the other end of the ball screw guide (124) is fixed relative to the housing (126).

[0014] The rotor (112) is secured 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 rotational force transmitted to the ball nut (116) generates a braking force that causes the ball screw (104) to move in a straight direction along the ball screw guide (124).

[0015] 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 seated on the caliper (129) through the bearing (131). The rotary lever (106) rotates by the linear braking force generated by the ball screw (104). While rotating, the rotary lever (106) non-linearly presses the compression member (130) to amplify the braking force and transmits the amplified braking force to the braking force application piston (108).

[0016] 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).

[0017] A parking brake (138) is installed on the outer surface of the screw nut (118). The parking brake (138) is equipped with a band-type lining (140) and a parking mechanism (142). The band-type 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) to press the band-type lining (140) against the screw nut (118), thereby generating a braking force for parking.

[0018] The bearing (146) supports the front of the screw nut (118) and the bearing (148) supports the rear of the screw nut (118) so that the screw nut (118) rotates smoothly relative to the housing (126).

[0019] A position sensor (150) is installed around the portion of the ball screw guide (124) exposed from the screw nut (118). The position sensor (150) is secured to the screw nut (118) by 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).

[0020] The load sensor (152) measures the reaction force generated when the friction pad (134) presses the brake disc (136) in order to measure the load (braking force) applied to the brake disc (136) by receiving it from the screw nut (118).

[0021] The housing cover (154) seals the housing (126) to protect the components inside the housing (126) from contamination from the outside.

[0022] 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) shown in FIG. 3. As shown, the adapter (128) is equipped with a connecting pin (302), an adapter bracket (304), and a compression part (306).

[0023] The connecting pin (302) is inserted into the front end of the ball screw (104) in a direction perpendicular to the direction of movement of the ball screw (104) and the direction of movement of the rotation lever (106). The adapter bracket (304) is provided with a connecting hole (402), and the connecting hole (402) is rotatably installed on the connecting pin (302). Thus, the adapter bracket (304) can rotate within a predetermined angle range relative to the ball screw (104) around the connecting pin (302). The compression part (306) is attached to the adapter bracket (304) on the side facing the direction of application of braking force and applies braking force to the seating part (156) of the rotation lever (106). The compression part (306) has a shape corresponding to the seating part (156) so as not to detach from the seating part (156) when braking force is applied or released. For example, if the seating portion (156) is a concave portion having a hemispherical shape, the compression portion (306) is a convex portion having a hemispherical shape with a diameter slightly smaller than that of the hemispherical shape of the seating portion (156).

[0024] As illustrated in FIG. 4, a load sensor (404) may be installed on the adapter bracket (304) parallel to the direction of application of braking force. The load sensor (404) receives the reaction force of the braking force via the compression 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 through the adapter (128) is used to control the electric motor (102) together with the rotation angle value measured by the position sensor (150).

[0025] The rotary lever (106) serves to amplify (amplify) the braking force transmitted from the ball screw (104). Therefore, if a load sensor is installed at a downstream position 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 is widened. As a result, the size of the appropriate load sensor increases, making mounting difficult, and the measurement precision decreases, making it difficult to control the electric motor (102). If a load sensor (404) is installed at an adapter (128) located at an upstream position of the rotary lever (106) during the braking force transmission process, the size of the load sensor can be reduced, making mounting easier, and sufficient measurement precision can be secured, allowing for proper control of the electric motor (102).

[0026] The adapter bracket (304) has a “C” 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). A connection hole (402) is formed in a position facing the two side walls (408). The connection 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 around the connection pin (302) relative 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 part (306) does not detach from the seating part (156) while applying braking force. Additionally, the maximum rotation angle of the adapter bracket (304) relative 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 that causes interference). There is also an advantage in that the assembly of the brake system can be improved by adjusting the maximum rotation angle.

[0027] The compression part (306) can be easily assembled and replaced by being connected to the adapter bracket (304) by a screw fastening method.

[0028] FIG. 5 is a configuration diagram of a ball screw (104) according to an embodiment of the present invention, and FIG. 6 is a configuration diagram of a ball screw (104) obtained by cutting line A-A' in FIG. 5. As illustrated, the ball screw (104) comprises a front section (502), a screw section (504), and a rear section (506). The front section (502) is the part that presses the rotation lever (106). The screw section (504) is the part that is connected to the ball nut (116) and the screw nut (118). In the rear section of the ball screw (104) (from the rear section (506) to approximately the center), a guide hole (508) with a cross-section that is not circular is formed inside. As illustrated in FIG. 5, for ease of processing or smooth movement, it is preferable that the guide hole (508) has an elliptical cross-section. Additionally, the guide hole (508) may have a polygonal cross-section, such as a triangle or a square.

[0029] FIG. 7 is a drawing illustrating the state in which a ball screw guide (124) according to one embodiment of the present invention is inserted into a ball screw (104) shown 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 part (702) and a head part (704). It is preferable that the insertion part (702) have a cross-section corresponding to the guide hole (508) to ensure accurate prevention of rotation. The head part (704) is formed integrally with the insertion part (702) and is fixed to a housing (126) or a housing cover (154).

[0030] FIG. 8 is a configuration diagram of a band-type lining (140) of a parking brake device (138) according to one embodiment of the present invention.

[0031] As illustrated in FIG. 8, the band-type lining (140) is provided with a back plate (802). The back plate (802) may be made of an elastic material, for example, metal. In the absence of external force, the back plate (802) is formed as a circle with a cross-section having a diameter larger than that of the screw nut (118), so no friction occurs between the screw nut (118) and the band-type lining (140).

[0032] Lining joints (144) are provided at both ends of the back plate (802). One lining joint (144) is connected to the housing (126), and the other is connected to the parking mechanism (142). When the parking brake is engaged, the parking mechanism (142) pulls the connected lining joint (144) to press the back plate (802) against the screw nut (118), causing the friction pad (804) to press the screw nut (118). When the force of the parking mechanism (142) pulling the lining joint is released and there is no external force, the back plate (802) returns to its original state due to elasticity, so no friction occurs between the screw nut (118) and the band-type lining (140).

[0033] The band-type lining (140) may be equipped with 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-type lining (140). 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, to prevent contamination by dust generated from the friction pad (804), a sealing material (158) and a sealing material (160) may be installed at the front and back of the band-type lining (140), respectively, between the housing (126) and the screw nut (118). Additionally, 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).

[0034] FIG. 9 is a diagram showing a part of a ball screw integrated motor actuator (101) with the band-type lining (140) shown in FIG. 8 installed. In FIG. 9, the screw nut (118) is shown with its upper half cut off and removed for understanding.

[0035] FIG. 10 is a cross-sectional view of a ball screw integrated motor actuator (1000) according to another embodiment of the present invention. As shown, the actuator (1000) comprises an electric motor (1002) and a ball screw (1004).

[0036] The electric motor (1002) is equipped with a stator (1010) and a rotor (1012) and generates rotational force when power is supplied from a power source (not shown).

[0037] The ball screw (1004) is fastened to the ball nut (1016) at the front (direction of braking force application or direction of the brake disc) and to the screw nut (1018) at the rear. The ball screw (1004) is provided 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 the ball screw (1004) and the ball nut (1016) by performing a rolling motion. A sealing part (not shown) is installed at the front and rear ends of the ball nut (1016). The sealing part prevents foreign matter from entering between the ball screw (1004) and the ball nut (1016) and serves to trap lubricant to prevent leakage. Compared to a sliding screw that does not use a ball, the ball screw (1004) makes it easier to maintain a small axial clearance and prevents the driving torque from becoming extremely large. In addition, wear is reduced, which extends the lifespan. For the circulation of the ball (120), structures such as a return pipe type, a deflector type, and an end cap type are all possible.

[0038] 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) to enable horizontal movement in the longitudinal direction. The ball nut (1016) and the screw nut (1018) are connected by a pin (1022) inserted in a direction perpendicular to the rotational plane of the rotor (1012) and operate as a single 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 seating portion (156) of the rotating 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).

[0039] An adapter (128) is 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 seated on the caliper (129) through the bearing (131). The rotary lever (106) rotates by the linear braking force generated by the ball screw (1004). While rotating, the rotary lever (106) non-linearly presses the compression member (130) to amplify the braking force and transmits the amplified braking force to the braking force application piston (108).

[0040] Bearings (1046, 1048, 1060) allow the screw nut (1018) to rotate smoothly relative to the housing (1025, 1026). 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 bearing (1048) supports the screw nut (1018) at the rear portion of the screw nut (1018). Bearing (1060) is composed of 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), allowing the screw nut (1018) to rotate.

[0041] A load sensor (1052) composed of a load cell is installed between the bearing (1060) and the housing (1026). In order to measure the load (braking force) applied to the brake disc (136), the load sensor (1052) receives and measures the reaction force generated when the friction pad (134) compresses the brake disc (136) via the screw nut (1018).

[0042] 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), a constant braking force desired by the driver cannot be generated. In order to always produce a constant output from the motor actuator (1000), load feedback control is performed by directly measuring the output load of the ball screw (1004) at the load sensor (1052) regardless of the operating distance of the rotary lever (106). Since a thrust bearing (1060) is assembled at the bottom of the screw nut (1018) and a load sensor (1052) is assembled at the bottom of the thrust bearing (1060), 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 (1060).

[0043] The housing (1025) supports the components of the front part of the actuator (1000), and the housing (1026) supports the components of the rear 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.

[0044] This embodiment is equipped with a clutch disc brake (1070) as a parking device. The clutch disc brake (1070) is installed on the outer surface of the rear portion of the screw nut (1018). FIG. 11 is a configuration diagram of the clutch disc brake (1070). As illustrated, the clutch disc brake (1070) comprises a stator (1102), an armature (1104), a rotor (1106), and a plate (1108). A coil (1110) is installed inside the stator (1102), and a torque spring (1112) is installed to press 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) 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 housing (1025, 1026). A hexagonal bolt (1118) is fastened to the stator (1102), the armature (1104), and the plate (1108).

[0045] 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 brake rotation lever (106) connected to the ball screw (1004), and the rotation lever (106) pushes the brake piston (108) to bring the friction pad (134) and the brake disc (136) into contact to brake. When the power (electricity) supply is cut off while the rotation lever (106) is applying force to the piston (108), the ball screw (1004) moves backward slightly 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). In order 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, to maintain the force applied to the piston (108), this embodiment uses a clutch disc brake (1070). When power is not supplied to the clutch disc brake (1070), the torque spring (1112) presses 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).

[0046] The embodiments of the electromechanical disc brake of the present invention described above are merely illustrative, and those skilled in the art will readily understand that various modifications and equivalent alternative embodiments are possible therefrom. Therefore, it will be readily understood that the present invention is not limited only to the forms mentioned in the detailed description above. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Furthermore, the present invention should be understood to include all modifications, equivalents, and substitutions within the spirit and scope of the present invention as defined by the appended claims. Explanation of the symbols

[0047] 100 : Electromechanical disc brake 101, 1000: Ball screw integrated motor actuator 102, 1002: Electric motor 104, 1004: Ball screw 106: Rotating lever 108: Braking force application piston 110, 1010: Stator 112, 1012: Rotor 116, 1016: Ball nut 118, 1018: Screw nut 120, 1020 : Sphere 122 : Insertion pin 123: Guide hole 124: Ball screw guide 126, 1025, 1026 : Housing 128 : Adapter 129 : Caliper 130 : Pressure member 131 : Bearing 132 : Back plate 134: Friction pad 136: Brake disc 138 : Parking brake 140 : Band-type lining 142: Parking mechanism 144: Lining joint 146, 148, 1046, 1048 : Bearing 150 : Position sensor 152, 1052: Load sensor 154, 1054: Housing cover 156 : Seating part 302 : Connecting pin 304: Adapter bracket 306: Compression part 402: Connection hole 404: Load sensor 406 : Front wall 408 : Side wall 502: Shear section 504: Screw section 506: Rear section 508: Guide hole 702 : Insertion part 704 : Head part 802: Backplate 804: Friction pad 1070: Clutch disc brake 1102: Stator 1104 : Amateur 1106 : Rotor 1108 : Plate 1110 : Coil 1112 : Torque spring 1114 : Lead wire 1116: Rotor hub 1118: Hex bolt with hex hole

Claims

Claim 1 A motor actuator used in an electromechanical disc brake comprises: an electric motor that generates rotational force; a screw nut connected to the electric motor and rotating 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 engaged with the ball nut and converting the rotational force generated by the electric motor into a linear braking force; and a parking brake device equipped with a clutch disc brake and applying a parking braking force to the screw nut. The clutch disc brake comprises a stator attached to the housing of the motor actuator, having a coil and a torque spring installed therein; a rotor that rotates integrally with the screw nut; an armature installed between the stator and the rotor and pressing 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 press the rotor. It also comprises a thrust bearing assembled at the lower end of the screw nut to support the reaction force of the screw nut, and installed between the thrust bearing and the housing, and from the ball screw A motor actuator characterized by further comprising a load sensor that measures the reaction force of the braking force transmitted via the screw nut and the thrust bearing, wherein the reaction force of the receiving piston is a reaction force.

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