JP7194574B2 - Electric driving device and electric power steering device - Google Patents

Description

The present invention relates to an electric drive device and an electric power steering device, and more particularly to an electric drive device and an electric power steering device incorporating an electronic control device.

In the field of general industrial machinery, electric motors are used to drive mechanical control elements. A so-called electromechanical integrated type electric drive device, which is integrally incorporated into a motor, is beginning to be adopted.

As an example of an electromechanically integrated type electric drive device, for example, in an electric power steering device for an automobile, the rotational direction and rotational torque of a steering shaft that is rotated by the driver's operation of the steering wheel are detected. Based on the detected value, the electric motor is driven so as to rotate in the same direction as the steering shaft, thereby generating steering assist torque. In order to control the electric motor, an electronic control unit (ECU) is provided in the power steering device.

As a conventional electric power steering device, for example, one described in Japanese Patent Application Laid-Open No. 2015-134598 (Patent Document 1) is known. Japanese Patent Application Laid-Open No. 2002-200001 describes an electric power steering device that is composed of an electric motor section and an electronic control section. The electric motor of the electric motor section is housed in a motor housing having a tubular section made of aluminum alloy or the like, and the board on which the electronic components of the electronic control section are mounted is located at the axial direction of the output shaft of the motor housing. It is attached to a heatsink that acts as the ECU housing located on the opposite side.

The substrate attached to the heat sink includes a power supply circuit, a power conversion circuit having power switching elements such as MOSFETs or IGBTs for driving and controlling the electric motor, and a control circuit for controlling the power switching elements. An output terminal of the element and an input terminal of the electric motor are electrically connected through a bus bar.

The electronic control unit attached to the heat sink is supplied with electric power from a power source through a connector case made of synthetic resin, and is also supplied with detection signals such as operating conditions from detection sensors. The connector case functions as a lid body, is fixed to hermetically close the heat sink, and is fixed to the outer peripheral surface of the heat sink by fixing screws.

In addition, as an electric drive device integrated with an electronic control device, an electric brake, an electrohydraulic controller for controlling various hydraulic pressures, and the like are known. explain.

JP 2015-134598 A

Here, in the electric power steering apparatus having the configuration disclosed in Patent Document 1, the motor housing, the heat sink, and the connector case are configured to be fastened together by a fixing screw inserted through a fixing portion formed so as to protrude toward the outer periphery. .

A sealing member such as an O-ring is used between the motor housing and the heat sink or between the heat sink and the connector case for liquid tightness. Furthermore, fixing screws are used to fix between the motor housing and the heat sink or between the heat sink and the connector case. When the heat sink is not used, an O-ring is interposed between the motor housing and the connector case and fixed with fixing screws.

By the way, automobiles often travel on roads sprayed with snow-melting agents or the like, or on roads near coastlines. For this reason, when driving on a snow-melted road or on a road near a coastline after rain, it is common to experience salt water entering under the floor of the automobile. Therefore, in the case of a liquid-tight seal structure with only an O-ring, a substantial fitting gap is formed up to the area where the O-ring is arranged. For this reason, salt water enters the fitting gap, corrodes the O-ring accommodating portion, and in the worst case causes a liquid-tightness failure, which may cause salt water to enter the interior and impair electrical reliability.

Therefore, in order to solve such problems, for example, as shown in FIG. It is possible to conceive of a configuration in which the connection is made through

In FIG. 18, an annular sealing agent storage groove 61 is formed on the outer peripheral surface of a motor housing 60 to recede inward. The motor housing 60 and the metal cover 63 can be joined in a liquid-tight manner by arranging the metal cover-side annular distal end portion 64 to cover the sealant containing groove 61 .

By the way, the liquid sealant 62 has adhesiveness and viscosity in order to maintain its shape when applied. can be spliced. However, due to this adhesiveness and viscosity, when the metal cover side annular tip portion 64 is pushed toward the end face side of the motor housing 60 in the direction of the arrow, the metal cover side annular tip portion 64 is A tensile force acts on the liquid sealing agent 62 in contact with the inner peripheral surface in one direction (downward arrow direction in the drawing).

Therefore, when the metal cover side annular tip portion 64 is pushed toward the end face side of the motor housing 60 , the liquid sealant 62 filled in the sealant storage groove 61 is pushed into the inner peripheral surface of the metal cover side annular tip portion 64 . A phenomenon of being pulled and moving along the movement of As a result, a space P in which the liquid sealing agent 62 does not exist is generated in the sealing agent storage groove 61 on the inner peripheral surface of the liquid sealing agent 62 and the metal cover-side annular distal end portion 64 .

As a result, the length of the seal is shortened, which increases the possibility that salt water or the like may enter the metal cover 63, resulting in a new problem of impairing mechanical and electrical reliability.

Therefore, an electric driving device and an electric power steering device are demanded to cope with such problems. A primary object of the present invention is to provide a novel electric drive device and electric power steering device with improved mechanical and electrical reliability.

A feature of the present invention is that the motor consists of an annular groove that is formed on the outer peripheral surface of the end surface of the motor housing opposite to the output portion of the rotary shaft of the electric motor and that recedes inward in a radial direction perpendicular to the axis of the motor housing. a housing-side annular groove; and a cover-side annular tip formed at an open end of a cover that covers an electronic control unit that controls the electric motor and facing the annular groove of the motor-housing-side annular groove from the outside. A liquid sealant is filled between the motor housing side annular groove portion and the cover side annular tip portion in a state where the cover side annular tip portion is arranged to face the groove portion, and the inner periphery of the cover side annular tip portion The surface is formed with an annular inclined surface that inclines and expands outward in the radial direction of the cover, and the inner peripheral side of the distal end of the annular inclined surface has an arc shape or an inclined shape that is inclined outward from the annular inclined surface. formed in, in place.

According to the present invention, the inner peripheral surface of the cover-side annular distal end portion is formed with an annular inclined surface that is inclined and expands outward in the radial direction of the cover. Alternatively, since it is formed in an inclined shape, when the cover-side annular tip portion is pushed toward the end face side of the motor housing, the liquid sealant is pulled and moved along with the movement of the inner peripheral surface of the cover-side annular tip portion. It is possible to suppress the generation of a space where the liquid sealing agent does not exist.

1 is an overall perspective view of a steering system as an example to which the present invention is applied; FIG. 1 is a perspective view showing the overall shape of an electric power steering device according to an embodiment of the present invention; FIG. FIG. 3 is an exploded perspective view of the electric power steering device shown in FIG. 2; 4 is an external perspective view of the motor housing shown in FIG. 3; FIG. 5 is a cross-sectional view of the motor housing shown in FIG. 4 taken in the axial direction; FIG. 5 is an external perspective view showing a state in which a power conversion circuit unit is mounted and fixed on the motor housing shown in FIG. 4; FIG. 7 is an external perspective view showing a state in which a power supply circuit unit is placed and fixed on the motor housing shown in FIG. 6; FIG. FIG. 8 is an external perspective view showing a state in which a control circuit unit is mounted and fixed on the motor housing shown in FIG. 7; FIG. 9 is an external perspective view showing a state in which the connector terminal assembly is mounted and fixed on the motor housing shown in FIG. 8; 1 is an external view of an electric power steering apparatus according to an embodiment of the present invention after caulking and fixing a metal cover to a motor housing; FIG. FIG. 11 is a cross-sectional view of the main parts of the electric power steering device before the metal cover shown in FIG. 10 is caulked and fixed to the motor housing; FIG. 12 is a cross-sectional view showing a state in which the metal cover and the motor housing shown in FIG. 11 are assembled; FIG. 12 is a cross-sectional view showing the shape of the inclined surface of the tip portion of the metal cover shown in FIG. 11; 14 is a cross-sectional view for explaining a further problem of the tip portion of the metal cover shown in FIG. 13; FIG. 15 is a cross-sectional view showing the shape of the inclined surface of the tip portion of the metal cover for solving the problem shown in FIG. 14. FIG. 16 is a cross-sectional view showing another shape of the inclined surface of the tip portion of the metal cover shown in FIG. 15; FIG. FIG. 16 is a cross-sectional view showing still another shape of the inclined surface of the tip portion of the metal cover shown in FIG. 15; FIG. 3 is a cross-sectional view showing an enlarged cross-section of a joint portion between a motor housing and a metal cover with a liquid sealant, for explaining the problem of the present invention;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and applications can be made within the technical concept of the present invention. is also included in the scope.

Before describing the embodiments of the present invention, the configuration of a steering system as an example to which the present invention is applied will be briefly described with reference to FIG.

First, a steering device for steering the front wheels of an automobile will be described. The steering system 1 is constructed as shown in FIG. A pinion (not shown) is provided at the lower end of a steering shaft 2 connected to a steering wheel (not shown), and this pinion meshes with a rack (not shown) elongated in the lateral direction of the vehicle body. Tie rods 3 for steering the front wheels in the left-right direction are connected to both ends of the rack, and the rack is covered with a rack housing 4 . A rubber boot 5 is provided between the rack housing 4 and the tie rod 3 .

An electric power steering device 6 is provided to assist the torque when turning the steering wheel. That is, a torque sensor 7 is provided for detecting the rotation direction and rotation torque of the steering shaft 2, and an electric motor unit 8 for applying a steering assist force to the rack via a gear 10 based on the detected value of the torque sensor 7. and an electronic control unit (ECU) section 9 that controls the electric motor arranged in the electric motor section 8 . The electric motor unit 8 of the electric power steering device 6 is connected to the gear 10 via screws (not shown) at three points on the outer periphery on the output shaft side, and the electronic control unit 9 is provided on the side opposite to the output shaft of the electric motor 8 unit. is provided.

In the electric power steering device 6, when the steering shaft 2 is rotated in one direction by operating the steering wheel, the torque sensor 7 detects the rotation direction and the rotation torque of the steering shaft 2. Based on this detected value, the control circuit section calculates the drive operation amount of the electric motor. The electric motor is driven by the power switching element of the power conversion circuit based on the calculated drive operation amount, and the output shaft of the electric motor is rotated so as to drive the steering shaft 1 in the same direction as the operation direction. Rotation of the output shaft is transmitted from a pinion (not shown) to a rack (not shown) via a gear 10 to steer the automobile. Since these configurations and actions are already well known, further explanation will be omitted.

Again, in FIG. 18, the adhesiveness and viscosity of the liquid sealing agent 62 are factors, and the metal cover side annular tip portion 64 is pushed into the end face side of the motor housing 60 in the direction of the arrow. At some point, a tensile force acts on the liquid sealing agent 62 that is in contact with the inner peripheral surface of the metal cover side annular tip portion 64 .

Therefore, when the metal cover side annular tip portion 64 is pushed toward the end face side of the motor housing 60 , the liquid sealant 62 filled in the sealant storage groove portion 61 is pushed into the inner peripheral surface of the metal cover side annular tip portion 64 . A phenomenon of being pulled and moving along the movement of As a result, a space P in which the liquid sealant 62 does not exist is generated in the sealant storage groove portion 61, and as a result, the seal length is shortened, and the possibility that salt water or the like enters the metal cover 63 increases. A new problem arises that the electrical reliability is impaired.

Against this background, the present invention proposes an electric power steering apparatus having the following configuration.

In the present invention, from an annular groove that is formed on the outer peripheral surface of the end face portion of a metal motor housing opposite to the output portion of the rotary shaft of the electric motor and retreats inward in a radial direction perpendicular to the axis of the motor housing. and a cover-side annular tip portion formed at the open end of a cover that covers an electronic control unit that controls the electric motor and facing the annular groove of the motor housing-side annular groove from the outside, and the motor housing A liquid sealant is filled between the motor housing side annular groove and the cover side annular tip with the metal cover side annular tip facing the side annular groove. The inner peripheral surface of the cover is formed with an annular inclined surface that inclines and expands outward in the radial direction of the cover. It was configured.

According to this, on the inner peripheral surface of the cover-side annular front end portion, an annular inclined surface is formed which is inclined and spreads outward in the radial direction of the cover. Since it is formed in an inclined shape, when the cover-side annular tip portion is pushed toward the end face side of the motor housing, the liquid sealant is pulled along with the movement of the inner peripheral surface of the cover-side annular tip portion and moves. is suppressed, and it is possible to suppress the generation of a space where the liquid sealing agent does not exist.

A specific configuration of an electric power steering apparatus according to an embodiment of the present invention will be described in detail below with reference to FIGS. 2 to 15. FIG.

FIG. 2 is a drawing showing the overall configuration of the electric power steering system according to the present embodiment, and FIG. 3 is a drawing showing the components of the electric power steering system shown in FIG. 4 to 9 are drawings showing the state in which each component is assembled according to the order of assembly of each component. Therefore, in the following description, each drawing will be referred to as appropriate.

4 to 9, the electronic parts and electrical parts of the control circuit section and the power supply circuit section are slightly different in configuration from those shown in FIG. 3, but have the same functions.

As shown in FIG. 2, the electric motor unit 8 that constitutes the electric power steering device includes a motor housing 11 having a cylindrical portion made of an aluminum-based metal such as aluminum or an aluminum alloy, and an electric motor housing 11 (not shown) housed therein. The electronic control unit 9 is arranged on the opposite side of the motor housing 11 from the output shaft in the axial direction and is made of aluminum, aluminum alloy or other aluminum-based metal, or iron-based metal. It consists of a metal cover 12 and an electronic control assembly (not shown) housed therein.

The motor housing 11 and the metal cover 12 are integrally fixed by caulking in fixing regions formed on the opposing end surfaces thereof and extending in the outer peripheral direction. The electronic control assembly housed inside the metal cover 12 includes a power supply circuit section for generating necessary power, and a power converter having power switching elements such as MOSFETs or IGBTs for driving and controlling the electric motor of the electric motor section 8. and a control circuit section for controlling the power switching element, and the output terminal of the power switching element and the coil input terminal of the electric motor are electrically connected via a bus bar.

A connector terminal assembly 13 is exposed through a hole formed in the metal cover 12 on the end face of the metal cover 12 opposite to the motor housing 11 . Also, the connector terminal assembly 13 is fixed to a fixing portion formed in the motor housing 11 by a fixing screw. The connector terminal assembly 13 includes a connector terminal forming portion 13A for power supply, a connector terminal forming portion 13B for a detection sensor, and a connector terminal forming portion 13C for sending a control state to an external device.

The electronic control assembly housed in the metal cover 12 is supplied with power from a power source through a power supply connector terminal forming portion 13A made of synthetic resin, and the operating state is detected by detection sensors. A signal is supplied through a connector forming terminal portion 13B for a detection sensor, and a current control state signal of the electric power steering apparatus is sent out through a connector terminal forming portion 13C for sending control state.

FIG. 3 shows an exploded perspective view of the electric power steering device 6. As shown in FIG. An annular iron side yoke (not shown) is fitted inside the motor housing 11, and an electric motor (not shown) is accommodated in this side yoke. An output portion 14 of the electric motor applies a steering assist force to the rack through a gear. Since the specific structure of the electric motor is well known, the explanation is omitted here.

The motor housing 11 is made of an aluminum alloy, and functions as a heat sink member that releases heat generated by the electric motor and heat generated by a power supply circuit section and a power conversion circuit section described later to the outside atmosphere. An electric motor section 8 is composed of the electric motor and the motor housing 11 .

An electronic control unit EC is attached to an end face portion 15 of the motor housing 11 opposite to the output portion 14 of the electric motor portion 8 . The electronic control unit EC is composed of a power conversion circuit unit 16 , a power supply circuit unit 17 , a control circuit unit 18 and a connector terminal assembly 13 . The end surface portion 15 of the motor housing 11 is formed integrally with the motor housing 11, but the end surface portion 15 may be separately formed and integrated with the motor housing 11 by screws or welding.

Here, the power conversion circuit section 16, the power conversion circuit section 17, and the control circuit section 18 constitute a redundant system, and constitute a dual system of the main electronic control section and the sub electronic control section. The electric motor is normally controlled and driven by the main electronic control unit, but if an abnormality or failure occurs in the main electronic control unit, it is switched to the sub electronic control unit to control and drive the electric motor. Become.

Therefore, as will be described later, heat from the main electronic control section is normally transferred to the motor housing 11, and if an abnormality or failure occurs in the main electronic control section, the main electronic control section stops and the sub electronic control section operates. , heat is transmitted to the motor housing 11 from the sub electronic control unit.

However, although not adopted in this embodiment, the main electronic control unit and the sub electronic control unit are combined to function as a regular electronic control unit, and if an abnormality or failure occurs in one electronic control unit, the other electronic control unit It is also possible to control and drive the electric motor with half the capacity at the part. In this case, the capacity of the electric motor is halved, but the so-called "power steering function" is ensured. Therefore, in a normal case, heat from the main electronic control section and the sub electronic control section is transferred to the motor housing 11 .

The electronic control unit EC includes a control circuit unit 18, a power supply circuit unit 17, a power conversion circuit unit 16, and a connector terminal assembly 13. The power conversion circuit unit 16, power supply The circuit section 17, the control circuit section 18, and the connector terminal assembly 13 are arranged in this order. The control circuit section 18 generates control signals for driving the switching elements of the power conversion circuit section 16, and is composed of a microcomputer, peripheral circuits, and the like. The power supply circuit unit 17 generates a power source for driving the control circuit unit 18 and a power source for the power conversion circuit unit 16, and is composed of a capacitor, a coil, a switching element, and the like. The power conversion circuit unit 16 adjusts the power flowing through the coils of the electric motor, and is composed of switching elements and the like that form three-phase upper and lower arms.

In the electronic control unit EC, the power conversion circuit unit 16 and the power supply circuit unit 17 mainly generate a large amount of heat. be done. The detailed configuration will be described later with reference to FIGS. 4 to 9. FIG.

A connector terminal assembly 13 made of synthetic resin is provided between the control circuit portion 18 and the metal cover 12, and is connected to a vehicle battery (power supply) and other external control devices (not shown). Needless to say, the connector terminal assembly 13 is connected to the power conversion circuit section 16, the power supply circuit section 17, and the control circuit section .

The metal cover 12 has the function of housing the power conversion circuit section 16, the power supply circuit section 17, and the control circuit section 18 and sealing them in a liquid-tight manner. It is fixed to the motor housing 11 .

Next, the configuration and assembly method of each component will be described with reference to FIGS. 4 to 9. FIG. First, FIG. 4 shows the appearance of the motor housing 11, and FIG. 5 shows its axial section.

In FIGS. 4 and 5, the motor housing 11 is formed in a cylindrical shape, a side peripheral surface portion 11A, an end surface portion 15 that closes one end of the side peripheral surface portion 11A, and the other end of the side peripheral surface portion 11A. and an end face portion 19 . In this embodiment, the motor housing 11 is cylindrical with a bottom, and the side peripheral surface portion 11A and the end surface portion 15 are integrally formed. Further, the end face portion 19 has a lid function, and closes the other end of the side peripheral face portion 11A after the electric motor is accommodated in the side peripheral face portion 11A.

A motor housing side annular groove portion 35 having an annular groove opening radially outward is provided on the entire peripheral surface of the end face portion 15 . An open end (hereinafter referred to as a metal cover side annular tip portion) 37 of the metal cover 12 shown in FIG. A portion between the motor housing side annular groove portion 35 and the metal cover side annular tip portion 37 of the metal cover 12 is liquid-tightly joined by a so-called liquid sealant.

As shown in FIG. 5, a stator 21 having a coil 20 wound around an iron core is fitted inside the side peripheral surface portion 11A of the motor housing 11, and a permanent magnet is embedded inside the stator 21. A rotor 22 is rotatably housed. A rotary shaft 23 is fixed to the rotor 22 , one end of which serves as an output portion 14 and the other end serves as a rotation detection portion 24 for detecting the rotational phase and number of rotations of the rotary shaft 23 . A permanent magnet is provided in the rotation detecting portion 24 and protrudes outside through a through hole 25 provided in the end face portion 15 . Then, the rotation phase and rotation speed of the rotating shaft 23 are detected by a magneto-sensitive portion such as a GMR element (not shown).

Returning to FIG. 4, on the surface of the end face portion 15 located on the side opposite to the output portion 14 of the rotary shaft 23, there are mounted the power conversion circuit portion 16 (see FIG. 3) and the heat dissipation portion of the power supply circuit portion 17 (see FIG. 3). 15A and 15B are formed. Board/connector fixing protrusions 26 are integrally erected at the four corners of the end face portion 15, and screw holes are formed therein.

The board/connector fixing protrusion 26 is provided for fixing the board of the control circuit section 18 and the connector terminal assembly 13, which will be described later. A substrate/connector fixing projection 26 erected from a power conversion heat dissipation region 15A, which will be described later, is formed with a board receiving portion 27 having the same height in the axial direction as a power heat dissipation region 15B, which will also be described later. A screw hole is formed in the receiving portion 27 . This substrate receiving portion 27 is for placing and fixing a glass epoxy substrate 31 of the power supply circuit portion 17, which will be described later.

A plane area in the radial direction orthogonal to the rotating shaft 23 that forms the end face portion 15 is divided into two. One forms a power conversion heat dissipation area 15A to which a power conversion circuit section 16 made of a power switching element such as a MOSFET is attached, and the other forms a power supply heat dissipation area 15B to which a power supply circuit section 17 is attached. . In this embodiment, the area of the power conversion heat dissipation region 15A is formed to be larger than that of the power supply heat dissipation region 15B. This is to secure the installation area of the power conversion circuit unit 16 since the duplex system is adopted as described above.

The power conversion heat radiation area 15A and the power heat radiation area 15B have steps with different heights in the axial direction (the direction in which the rotating shaft 23 extends). That is, the power-supply heat-radiating region 15B is formed to have steps in the direction away from the power-converting heat-radiating region 15A when viewed in the direction of the rotating shaft 23 of the electric motor. This step is set to a length such that the power inverter circuit unit 16 and the power supply circuit unit 17 do not interfere with each other when the power supply circuit unit 17 is installed after the power inverter circuit unit 16 is installed.

Three elongated rectangular projecting heat radiation portions 28 are formed in the power conversion heat radiation region 15A. The projecting heat radiation portion 28 is provided with a dual-system power conversion circuit portion 16, which will be described later. The projecting heat radiation portion 28 protrudes and extends in a direction away from the electric motor when viewed in the direction of the rotating shaft 23 of the electric motor.

Further, the power heat dissipation area 15B is planar, and a power supply circuit section 17, which will be described later, is installed thereon. Therefore, the projecting heat radiation portion 28 functions as a heat radiation portion that transfers the heat generated in the power conversion circuit portion 16 to the end surface portion 15 , and the heat radiation region 15 B for power supply transmits the heat generated in the power supply circuit portion 17 to the end surface portion 15 . It functions as a heat-dissipating part that transfers heat.

Note that the projecting heat radiation portion 28 can be omitted, and in this case, the power conversion heat radiation region 15A functions as a heat radiation portion that transfers heat generated in the power conversion circuit portion 16 to the end face portion 15 . However, in the present embodiment, the metal substrate of the power conversion circuit unit 16 is welded to the protruding heat radiating portion 28 by friction stir welding to ensure reliable fixation.

As described above, in the end surface portion 15 of the motor housing 11 according to the present embodiment, the heat sink member is omitted and the length in the axial direction can be shortened. Also, since the motor housing 11 has a sufficient heat capacity, the heat of the power supply circuit section 17 and the power conversion circuit section 16 can be efficiently radiated to the outside.

Next, FIG. 6 shows a state in which the power conversion circuit section 16 is installed on the ridge heat dissipation section 28 (see FIG. 4). As shown in FIG. 6, the power conversion circuit section 16 having a dual system is installed above the projecting heat dissipation portion 28 (see FIG. 4) formed in the power conversion heat dissipation region 15A. A switching element that constitutes the power conversion circuit unit 16 is placed on a metal substrate (here, an aluminum-based metal is used), and is configured to easily dissipate heat. The metal substrate is welded to the projecting heat radiation portion 28 by friction stir welding.

Therefore, the metal substrate is firmly fixed to the projecting heat radiation portion 28 (see FIG. 4), and the heat generated by the switching element can be efficiently transferred to the projecting heat radiation portion 28 (see FIG. 4). The heat transmitted to the protruding heat radiation portion 28 (see FIG. 4) is diffused to the power conversion heat radiation area 15A, further transferred to the side peripheral surface portion 11A of the motor housing 11, and radiated to the outside. Here, as described above, since the axial height of the power conversion circuit section 16 is lower than the height of the power supply heat radiation area 15B, it does not interfere with the power supply circuit section 17, which will be described later.

In this manner, the power conversion circuit section 16 is installed above the protruding heat dissipation portion 28 formed in the power conversion heat dissipation region 15A. Therefore, the heat generated by the switching elements of the power conversion circuit section 16 can be efficiently transferred to the projecting heat radiation section 28 . Further, the heat transferred to the projecting heat dissipation portion 28 is diffused to the power conversion heat dissipation region 15A, transferred to the side peripheral surface portion 11A of the motor housing 11, and radiated to the outside.

Next, FIG. 7 shows a state in which the power supply circuit section 17 is installed from above the power conversion circuit section 16 . As shown in FIG. 7, the power supply circuit section 17 is installed above the heat radiation area 15B for power supply. A capacitor 29, a coil 30, and the like, which constitute the power supply circuit section 17, are mounted on a glass epoxy substrate 31. As shown in FIG. The power supply circuit section 17 also employs a duplex system, and as can be seen from the drawing, power supply circuits each comprising a capacitor 29, a coil 30, and the like are formed symmetrically. Electric elements such as capacitors other than the switching elements of the power conversion circuit 16 are mounted on the glass epoxy substrate 31 .

The surface of the glass epoxy substrate 31 on the side of the power heat dissipation region 15B (see FIG. 6) is fixed to the end face portion 15 so as to be in contact with the power heat dissipation region 15B. As for the fixing method, as shown in FIG. 7, the board/connector fixing projection 26 is fixed to a screw hole provided in the board receiving portion 27 by a fixing screw (not shown). It is also fixed by a fixing screw (not shown) to a screw hole provided in the power heat radiation area 15B (see FIG. 6).

Since the power supply circuit section 17 is formed of the glass epoxy substrate 31, double-sided mounting is possible. On the surface of the glass epoxy substrate 31 facing the heat dissipation area 15B for power supply (see FIG. 6), a rotation phase and rotation speed detection unit including a GMR element (not shown) and a detection circuit for the same is mounted. In cooperation with a rotation detection unit 24 (see FIG. 5) provided in the rotor (see FIG. 5), the rotation phase and the number of rotations are detected.

In this manner, since the glass epoxy substrate 31 is fixed in contact with the power heat dissipation area 15B (see FIG. 6), the heat generated in the power supply circuit section 17 is efficiently dissipated into the power heat dissipation area 15B (see FIG. 6). ) can be transferred. The heat transmitted to the power heat radiation area 15B (see FIG. 6) is diffused and transferred to the side peripheral surface portion 11A of the motor housing 11, and is radiated to the outside. Here, between the glass epoxy substrate 31 and the heat radiation area 15B for power supply (see FIG. 6), by interposing any one of an adhesive agent, heat radiation grease, and a heat radiation sheet with good heat transfer, the heat transfer performance can be further enhanced. can be improved.

In this manner, the power supply circuit section 17 is installed above the heat radiation area 15B for power supply. The surface of the glass epoxy substrate 31 on which the circuit elements of the power supply circuit portion 17 are placed, which faces the power heat dissipation region 15B, is fixed to the end face portion 15 so as to be in contact with the power heat dissipation region 15B. Therefore, the heat generated in the power supply circuit section 17 can be efficiently transferred to the power supply heat dissipation area 15B. The heat transmitted to the power heat radiation area 15B diffuses to the side peripheral surface portion 11A of the motor housing 11, is transmitted, and is radiated to the outside.

Next, FIG. 8 shows a state in which the control circuit section 18 is installed from above the power supply circuit section 17. As shown in FIG. As shown in FIG. 8, the control circuit section 18 is installed above the power supply circuit section 17 . A microcomputer 32 and peripheral circuits 33 constituting the control circuit section 18 are placed on a glass epoxy substrate 34 . The control circuit section 18 also employs a dual system, and as can be seen from the drawing, a control circuit comprising a microcomputer 32 and a peripheral circuit 33 is formed for each. Incidentally, the microcomputer 32 and the peripheral circuit 33 may be provided on the surface of the glass epoxy substrate 34 on the power supply circuit 17 side.

As shown in FIG. 8, the glass epoxy board 34 is held by the connector terminal assembly 13 in a screw hole provided at the top of the board/connector fixing protrusion 26 (see FIG. 7) by a fixing screw (not shown). Between the glass epoxy board 31 of the power supply circuit section 17 (see FIG. 7) and the glass epoxy board 34 of the control circuit section 18, the capacitor 29, coil 30, etc. of the power supply circuit section 17 shown in FIG. It is a space where

Next, FIG. 9 shows a state in which the connector terminal assembly 13 is installed from above the control circuit section 18. As shown in FIG. As shown in FIG. 9, the connector terminal assembly 13 is installed above the control source circuit section 18 . The connector terminal assembly 13 is fixed by a fixing screw 36 such that the control circuit portion 18 is inserted into a screw hole provided at the top of the substrate/connector fixing protrusion 26 . In this state, the connector terminal assembly 13 is connected to the power conversion circuit section 16, the power supply circuit section 17, and the control circuit section 18 as shown in FIG.

Furthermore, after this, the metal cover side annular tip portion 37 of the metal cover 12 is arranged so as to cover the motor housing side annular groove portion 35 of the motor housing 11 from the outside, and the caulking provided along the outer peripheral direction of the metal cover 12 It is fixed by the fixing part.

As shown in FIG. 10 , the caulking fixing portions 38 are formed at approximately 120° intervals around the axis of the rotating shaft 23 on the outer periphery of the metal cover 12 . FIG. 10 shows the appearance of the electric power steering device 6 with the motor housing 11 and the metal cover 12 fixed by caulking. 11 shows a cross section before the metal cover 12 is fixed to the end face portion 15 of the motor housing 11. As shown in FIG.

10 and 11, a plurality (three) of caulking fixing portions 38 are formed on the outer peripheral surface of the metal cover 12. As shown in FIG. The caulking fixing portion 38 extends axially toward the connector terminal assembly 13 side from the motor housing side annular groove portion 35 formed in the entire peripheral surface of the end surface portion 15 of the motor housing 11, and the power conversion heat dissipation area 15A. The wall surface of the metal cover 12 is pushed by a pressing tool into a caulking recess 40 such as a caulking groove or a caulking hole provided in the fixed wall 39 forming the power heat radiation area 15B to be plastically deformed and applied. It is formed by being tightened. The axial positioning of the metal cover 12 is performed using the connector assembly 13, and in a state in which the axial position of the metal cover 12 is determined, the wall surface of the metal cover 12 is pressed into the caulking recess 40 by a pressing tool. It is designed to be pushed in and crimped.

In addition, the space formed by the motor housing side annular groove portion 35 in which the metal cover side annular tip portion 37 of the metal cover 12 is arranged is filled with a liquid sealing agent 41 without gaps. Therefore, since a liquid-tight seal area is formed between the crimping fixing portion 38 and the metal cover side annular tip portion 37 of the metal cover 12, the infiltration of salt water or the like is prevented in the seal area. Therefore, since salt water or the like does not enter the crimped fixing portion 38, corrosion of the crimped fixing portion 38 is suppressed, and mechanical reliability can be improved. Furthermore, since intrusion of salt water or the like into the electronic control unit 9 is suppressed, electrical reliability can be improved as well.

12 and 13, a more detailed configuration of the vicinity of the joint region between the metal cover side annular tip portion 37 and the motor housing side annular groove portion 35 will be described.

In FIG. 12, the outer diameter Dc of the metal cover-side annular distal end portion 37 of the metal cover 12 and the outer diameter Dh of the end surface portion 15 of the motor housing 11 are substantially the same radius, and the respective outer peripheral surfaces appear to be They are formed on the same plane (flush) on the top. The motor housing side annular groove 35 formed in the outer peripheral surface of the end face portion 15 of the motor housing 11 is radially inwardly perpendicular to the axis of the motor housing 11 which is the same as the axis of the rotating shaft 23 (see FIG. 11). In addition, it is formed in a shape recessed inwardly by a predetermined distance L from the fixed wall 39 .

On the other hand, the opening surface of the metal cover-side annular tip portion 37 of the metal cover 12 is widened outward by bending. An annular slanted surface 37IN is formed that is slanted outward in the direction of the slanted surface. A bending start point 37S of the annular inclined surface 37IN is bent from the vicinity of the upper wall surface 35U of the motor housing side annular groove portion 35 in the drawing and expanded.

11, the liquid sealant 41 is applied so as to fill the motor housing side annular groove 35 before the metal cover 12 is attached. Here, as described above, the liquid sealing agent 41 is adhesive and viscous. A tensile force acts on the liquid sealant 41 in contact with the annular inclined surface 37IN, which is the inner peripheral surface of 37 . Therefore, a phenomenon occurs in which the liquid sealant 41 filled in the motor housing side annular groove portion 35 is pulled and moved along with the movement of the annular inclined surface 37IN of the metal cover side annular tip portion 37 .

However, in the present embodiment, the annular inclined surface 37IN that is inclined and expands outward in the radial direction of the metal cover 12 is formed on the inner peripheral surface of the metal cover-side annular distal end portion 37. The tensile force generated by contact with the liquid sealing agent 41 is dispersed, as indicated by arrows, at least in the direction along the annular inclined surface 37IN, the pushing direction of the metal cover 12, and the radial direction. . Therefore, even if the liquid sealing agent 41 is pulled along with the movement of the annular inclined surface 37IN of the metal cover-side annular distal end portion 37, the load is dispersed, so that a space is formed by the movement of the liquid sealing agent 41. will be suppressed.

As described above, when the metal cover side annular tip portion 37 is pushed toward the end face portion 15 side of the motor housing 11, the liquid sealant 41 filled in the motor housing side annular groove portion 35 is applied to the metal cover side annular tip portion. The phenomenon of pulling and moving along the movement of the annular inclined surface 37IN of 37 is suppressed. As a result, a space in which the liquid sealant 41 does not exist is less likely to occur in the motor-housing-side annular groove 35, and the increased seal length suppresses the risk of salt water or the like entering the metal cover 12. As a result, Mechanical and electrical reliability can be improved.

Here, as shown in FIG. 13, the inclination angle θ of the annular inclined surface 37IN of the metal cover side annular tip portion 37 of the metal cover 12 according to the present embodiment is preferably set within a range of 5° to 9°. The liquid sealing agent 41 can be sufficiently left.

Then, the ratio of the liquid sealant 41 in contact with the annular inclined surface 37IN of the metal cover-side annular tip portion 37 was actually measured in the axial length of the motor-housing-side annular groove portion 35 . In this case, the metal cover 12 is divided into 8 parts at equal intervals in the circumferential direction, and the ratio of the adhesion length in each part (adhesion length / axial length of the motor housing side annular groove 35) is calculated and averaged. turned into

In the conventional structure shown in FIG. 18, the ratio of the bonding length was about 43%. It was about 89%, and about 92% in the case of 9°. Therefore, it can be considered sufficient if the inclination angle .theta.

However, in such an embodiment, the following problems are assumed, and it is important to take countermeasures against them.

As shown in FIG. 14 , the entire front end face 37T of the metal cover-side annular front end portion 37 is formed on a plane perpendicular to the axis 23C of the rotating shaft 23 . For this reason, the surface of the tip surface 37T pushes the liquid sealant 41 against the liquid sealant 41, and as a result, the annular inclined surface 37IN of the metal cover side annular tip portion 37 and the liquid sealant 41 This results in a phenomenon that the distance between the bonding surfaces is shortened.

In order to prevent the distance between the annular inclined surface 37IN and the bonding surface of the liquid sealant 41 from being shortened due to such a phenomenon, as shown in FIG. An annular slanted surface 37IN is formed on the inner surface of the metal cover 12 so as to slanted outward in the radial direction of the metal cover 12, and the inner peripheral side of the distal end of the annular slanted surface 37IN is formed in an arc shape.

In FIG. 15, the metal cover-side annular distal end portion 37 of the metal cover 12 is bent so as to curve outward, and the annular inclined surface 37IN is formed of a linear portion 37L and an arc-shaped portion 37C. 37 C of arcuate parts are formed in the front end side from 37 L of linear parts, and this arcuate part 37C is made into the shape which protrudes toward the liquid sealing agent 41 side.

With such a shape, the liquid sealant 41 comes into contact with the arcuate portion 37C during the process of inserting the metal cover side annular tip portion 37 of the metal cover 12 into the motor housing side annular groove portion 35 of the motor housing 11. will come to At this time, the friction between the arcuate portion 37C and the liquid sealant 41 is reduced, the amount of extrusion of the liquid sealant can be reduced, and the phenomenon that the distance between the adhesive surfaces of the liquid sealant 41 is shortened can be suppressed. .

Further, the bent portion of the metal cover-side annular distal end portion 37 protrudes outward from the outer circumference of the end face portion 15 of the motor housing 11 , so that it is flush with the outer circumference of the end face portion 15 of the motor housing 11 . , the overhanging portion is cut to form a flat surface 37E. This makes it possible to avoid increasing the diameter of this type of electric drive device.

As described above, when the metal cover side annular tip portion 37 is pushed toward the end face portion 15 side of the motor housing 11, the liquid sealant 41 filled in the motor housing side annular groove portion 35 is applied to the metal cover side annular tip portion. The phenomenon of pulling and moving along the movement of 37 is suppressed.

As a result, a space in which the liquid sealant 41 does not exist is less likely to occur in the motor-housing-side annular groove 35, and the increased seal length suppresses the risk of salt water or the like entering the metal cover 12. As a result, Mechanical and electrical reliability can be improved.

In the embodiment shown in FIG. 15, the metal cover-side annular distal end portion 37 of the metal cover 12 is opened by bending the opening surface so as to curve outward, so that the linear portion 37L and the arcuate portion 37C An annular inclined surface 37IN is formed.

On the other hand, in the embodiment shown in FIG. 16, the arc-shaped portion 37C is not formed by bending, and the arc-shaped portion 42C is formed only on the inner peripheral surface of the annular inclined surface 42IN on the tip side by pressing, polishing, or cutting. is.

15, the friction between the arcuate portion 42C and the liquid sealant 41 is reduced in this embodiment, and the amount of extrusion of the liquid sealant 41 can be reduced. can be suppressed.

With this structure as well, when the metal cover side annular tip portion 37 is pushed toward the end face portion 15 side of the motor housing 11, the liquid sealant 41 filled in the motor housing side annular groove portion 35 is pushed into the metal cover side annular tip portion. The phenomenon of being pulled and moved along the movement of the portion 37 is suppressed.

As a result, a space in which the liquid sealant 41 does not exist is less likely to occur in the motor-housing-side annular groove 35, and the increased seal length suppresses the risk of salt water or the like entering the metal cover 12. As a result, Mechanical and electrical reliability can be improved.

In the embodiment shown in FIG. 15, the metal cover-side annular distal end portion 37 of the metal cover 12 is opened by bending the opening surface so as to curve outward, so that the linear portion 37L and the arcuate portion 37C An annular inclined surface 37IN is formed. Similarly, in the embodiment shown in FIG. 16, an arc-shaped portion 42C is formed by pressing, grinding, or cutting on the inner peripheral surface of the annular inclined surface 42IN of the metal cover-side annular tip portion 42 of the metal cover 12. there is

On the other hand, in this embodiment, as shown in FIG. 17, an inclined surface portion is formed on the inner peripheral surface of the annular inclined surface 43IN of the metallic cover side annular distal end portion 43 of the metal cover 12 by pressing, polishing, or cutting. 43C was formed. The inclination angle θ2 of the inclined surface portion 43C is formed in an inclined shape further inclined toward the outside with respect to the inclination angle θ1 of the straight portion 43L. Here, the inclination angles .theta.1 and .theta.2 indicate angles with respect to the upper inner peripheral wall of the metal cover 12 parallel to the axis 23C of the rotating shaft 23. As shown in FIG.

In this embodiment, as in the case shown in FIG. 15, the friction between the inclined surface portion 43C and the liquid sealant 41 is reduced, the amount of extrusion of the liquid sealant 41 can be reduced, and the distance between the adhesive surfaces of the liquid sealant 41 can be reduced. The phenomenon of shortening can be suppressed.

With this structure as well, when the metal cover side annular tip portion 43 is pushed toward the end face portion 15 side of the motor housing 11, the liquid sealing agent 41 filled in the motor housing side annular groove portion 35 is pushed into the metal cover side annular tip portion. The phenomenon of being pulled and moved along the movement of the portion 43 is suppressed.

As a result, a space in which the liquid sealant 41 does not exist is less likely to occur in the motor-housing-side annular groove 35, and the increased seal length suppresses the risk of salt water or the like entering the metal cover 12. As a result, Mechanical and electrical reliability can be improved.

In each of the above-described embodiments, the liquid-tight liquid sealing agent 41 uses a synthetic resin having adhesiveness, and in this embodiment, a silicone rubber-based elastic adhesive is used.

Silicone rubber-based elastic adhesives have the property of absorbing stress such as external vibrations and impacts, and preventing stress from concentrating on the adhesive interface. For this reason, there is a risk that the adhesive interface will peel off and the liquid-tight function will be lost in devices such as electric power steering devices that are subject to vibrations and impacts. It is possible to reduce the risk of loss of dense functions.

In addition, in this embodiment, sealing is performed with the adhesive liquid sealant 41, so that the liquid-tight O-ring that has been conventionally used can be omitted. For this reason, it is not necessary to form a storage groove for storing the O-ring in the fixed wall 39, and it is possible to suppress an increase in manufacturing cost.

This silicon-based elastic adhesive (liquid sealing agent 41) may be a liquid gasket (FIPG: FORMED IN PLACE GASKET) having an adhesive function, and is made of a material that cures at room temperature or heat. can use things.

In addition, since the metal cover 12 and the motor housing 11 are fixed by the crimp fixing portion 38 without using fixing screws, the external shape can be made small and the weight can be reduced.

Furthermore, when an O-ring is used, it is necessary to form an accommodation groove for accommodating the O-ring, but in the case of this embodiment, no O-ring is used, so there is no need to process the accommodation groove, etc., which reduces the manufacturing cost. can be suppressed.

By using a highly heat-dissipative liquid sealant 41 obtained by kneading a material with good thermal conductivity such as alumina as the liquid sealant 41, the adhesion area is large, and the power conversion heat dissipation region 15A and the power supply heat dissipation region 15A are used. It becomes possible to efficiently dissipate the heat of the region 15B to the metal cover 12 . As a result, the heat from the electrical components that constitute the power supply circuit section and the power conversion circuit section can be efficiently radiated to the outside, and miniaturization is possible.

In the above-described embodiment, as fixing means for fixing the metal cover 11 and the motor housing 11 without using fixing screws, the crimping fixing portions 38 are formed at three locations, but the crimping fixing portions are formed over the entire circumference. It is also possible to

As described above, according to the present invention, it is formed on the outer peripheral surface of the end surface portion of the motor housing opposite to the output portion of the rotating shaft of the electric motor, and retreats inward in the radial direction perpendicular to the axis of the motor housing. A motor-housing-side annular groove formed of an annular groove, and a cover-side annular tip formed at an open end of a cover that covers an electronic control unit for controlling the electric motor and facing the annular groove of the motor-housing-side annular groove from the outside. a liquid sealant is filled between the motor housing side annular groove portion and the cover side annular tip portion in a state where the cover side annular tip portion is arranged to face the motor housing side annular groove portion; The inner peripheral surface of the tip portion is formed with an annular slanted surface that inclines and expands outward in the radial direction of the cover. It is configured such that it is formed in a slanted shape.

According to this, the inner peripheral surface of the cover-side annular distal end portion is formed with an annular inclined surface that is inclined and expands outward in the radial direction of the cover. When the cover-side annular tip is pushed toward the end face of the motor housing, the liquid sealant is prevented from being pulled and moved along the movement of the inner peripheral surface of the cover-side annular tip. Therefore, it is possible to suppress the generation of a space where the liquid sealing agent does not exist.

It should be noted that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

DESCRIPTION OF SYMBOLS 6... Electric power steering apparatus, 8... Electric motor part, 9... Electronic control part, 11... Motor housing, 12... Metal cover, 13... Connector terminal assembly, 14... Output part, 15... End face part, 15A... Power conversion 15B... Heat dissipation area for power supply 16... Power conversion circuit part 17... Power supply circuit part 18... Control circuit part 19... End face part 20... Coil 21... Stator 22... Rotor 23... Rotation Axle 24 Rotation detecting portion 25 Through hole 26 Substrate/connector fixing projection 27 Substrate receiving portion 28 Protruding heat radiation portion 29 Capacitor 30 Coil 31 Glass epoxy substrate 32 Microphone computer 33 Peripheral circuit 34 Glass epoxy board 35 Annular groove on motor housing side 36 Fixing screw 37, 42, 43 Annular tip on metal cover side 37IN, 42IN, 43IN Annular inclined surface , 37L, 42L, 43L... straight portion, 37C, 42C... arc-shaped portion, 43C... inclined surface portion, 41... liquid sealant.

Claims (10)

A motor housing containing an electric motor for driving a mechanical system control element, and an end surface of the motor housing opposite to the output section of the rotating shaft of the electric motor for driving the electric motor. and a cover covering the electronic control unit, wherein
A motor comprising an annular groove that is formed on the outer peripheral surface of the end face portion of the motor housing on the side opposite to the output portion of the rotating shaft of the electric motor and retreats inward in a radial direction perpendicular to the axis of the motor housing. a housing-side annular groove; and a cover-side annular distal end portion formed at an open end of the cover covering the electronic control unit for controlling the electric motor and facing the annular groove of the motor housing-side annular groove from the outside. ,
A liquid sealant is filled between the motor housing side annular groove portion and the cover side annular tip portion in a state in which the cover side annular tip portion is arranged to face the motor housing side annular groove portion, and
An annular slanted surface that is slanted outward in the radial direction of the cover and expands is formed on the inner peripheral surface of the cover-side annular front end portion, and the inner peripheral side of the front end of the annular slanted surface is arc-shaped, Alternatively, the electric drive device is formed in an inclined shape inclined outward from the annular inclined surface. In the electric drive device according to claim 1,
An electric drive device, wherein the cover is made of metal. In the electric drive device according to claim 2,
The electric drive device according to claim 1, wherein the cover-side annular front end portion of the cover is bent so that the front end inner peripheral side of the annular inclined surface is formed into an arc shape. In the electric drive device according to claim 2,
The cover-side annular distal end portion of the cover is bent to form a linear portion of the annular inclined surface, and the inner peripheral side of the distal end of the annular inclined surface is formed into an arc shape by grinding or cutting. An electric drive device characterized by: In the electric drive device according to claim 2,
The cover-side annular distal end portion of the cover has a linear portion of the annular inclined surface formed by bending, and the tip inner peripheral side of the annular inclined surface is ground or cut to be inclined outward from the annular inclined surface. Slanted surface
An electric drive device characterized by: An electric motor that applies a steering assist force to the steering shaft based on an output from a torque sensor that detects a rotational direction and a rotational torque of the steering shaft; a motor housing that accommodates the electric motor; and rotation of the electric motor. An electric power steering comprising: an electronic control section for driving the electric motor arranged on the side of the end surface of the motor housing opposite to the output section of the shaft; and a cover covering the electronic control section. a device,
A motor comprising an annular groove that is formed on the outer peripheral surface of the end face portion of the motor housing on the side opposite to the output portion of the rotating shaft of the electric motor and retreats inward in a radial direction perpendicular to the axis of the motor housing. a housing-side annular groove; and a cover-side annular distal end portion formed at an open end of the cover covering the electronic control unit for controlling the electric motor and facing the annular groove of the motor housing-side annular groove from the outside. ,
A liquid sealant is filled between the motor housing side annular groove portion and the cover side annular tip portion in a state in which the cover side annular tip portion is arranged to face the motor housing side annular groove portion, and
An annular slanted surface that is slanted outward in the radial direction of the cover and expands is formed on the inner peripheral surface of the cover-side annular front end portion, and the inner peripheral side of the front end of the annular slanted surface is arc-shaped, Alternatively, the electric power steering device is formed in an inclined shape inclined outward from the annular inclined surface. In the electric power steering device according to claim 6,
An electric power steering apparatus, wherein the cover is made of metal. In the electric power steering device according to claim 7,
An electric power steering apparatus according to claim 1, wherein the cover-side annular distal end portion of the cover is formed in an arc shape on the inner peripheral side of the distal end of the annular inclined surface by bending. In the electric power steering device according to claim 7,
The cover-side annular distal end portion of the cover is bent to form a linear portion of the annular inclined surface, and the inner peripheral side of the distal end of the annular inclined surface is formed into an arc shape by grinding or cutting. An electric power steering device characterized by: In the electric power steering device according to claim 7,
The cover-side annular distal end portion of the cover has a linear portion of the annular inclined surface formed by bending, and the tip inner peripheral side of the annular inclined surface is ground or cut to be inclined outward from the annular inclined surface. Slanted surface
An electric power steering device characterized by:

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