Drive device and electric power steering device including the drive device

A drive device that includes a motor having a rotor disposed relative to a stator, a cover having a one-end-closed cylinder shape and positioned on one axial end side of the motor, and a substrate on the inside of the cover perpendicular to a motor shaft having electronic components implemented on the substrate. The drive device also includes a connector positioned on a motor side of the substrate with an opening that is connectable to an external terminal. The opening of the connector faces outward relative to the motor shaft. The drive device further includes a heat sink having a frame end part and a heat receiving part formed in one body. The drive device increases heat capacity of the heat sink without increasing its height.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2014-156480, filed on Jul. 31, 2014, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a drive device and an electric power steering device including the drive device.

BACKGROUND INFORMATION

Conventionally, a drive device used for the electric power steering device with which the steering operation by a driver is assisted has a one-body structure, in which the motor and the motor controller are combined in one body.

The controller for the drive device disclosed in a patent document, JP 2011-176998 A (Patent document 1) has two substrates that are disposed perpendicularly to the rotation axis of the rotor of the motor (a motor shaft) and a heat sink disposed in between the two substrates. The outer wall of the heat sink has a power module attached thereto at a part of the outer wall that is in parallel with the motor shaft, and the power module molds multiple switching elements to be serving as an inverter circuit. Therefore, the drive device has a heat dissipation capability, dissipating heat of the power module to the heat sink at the power module operation time.

However, the controller making up the drive device of the patent document 1 has two substrates, thereby having an increased dimension along the motor shaft due to the thickness of the electronic components and the substrate supporting those components. Further, the power module is attached on the outer wall of the heat sink that is disposed in parallel with the motor shaft, which creates an excess unoccupied space inside the cup-shape motor cover due to the square shape of the power module.

SUMMARY

It is an object of the present disclosure to provide a drive device that has a smaller volume along the motor shaft, and an electric power steering device using such a drive device.

In one aspect of the present disclosure, a drive device includes a motor having a rotor that is located relative to a stator, a cover having a one-end-closed cylinder shape and positioned on one axial end side of the motor, and a substrate on the Inside of the cover perpendicular to a motor shaft having electronic components implemented on the substrate to control an electric current supplied to the motor.

The drive device also includes a connector positioned on a motor side of the substrate with an opening that is connected to an external terminal. The opening of the connector faces outward relative to the motor shaft.

The drive device further includes a heat sink having a frame end part and a heat receiving part formed in one body to absorb heat from the electronic components implemented on the substrate. The frame end part covers a substrate side of the stator and the rotor, and the heat receiving part Is positioned radial inside of the connector, relative to the motor shaft, when viewed at a direction through the motor shaft, and rising from the frame end part toward the substrate, when viewed at a direction perpendicular to the motor shaft.

In such manner, the connector, which is a relatively large component among many components making up the controller for controlling the motor, is positioned on the motor side of the substrate. Further, the heat sink is capable of providing a large heat capacity by having a one body structure in which the frame end part and the heat receiving part are combined in one body and the heat receiving part is positioned at a radial inside of the connector. Therefore, no excess unoccupied space is created inside the cup-shape cover that covers the substrate and the smaller volume drive device is constructed by reducing the along-motor-shaft dimension thereof.

In another aspect of the present disclosure, an electric power steering device having the drive device is devised. When the drive device is reduced in volume, the electric power steering device has an improved installability in a vehicle.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described based on the drawings.

First Embodiment

The first embodiment of the present disclosure is shown inFIG. 1toFIG. 6. A drive device1of the present embodiment is used in an electric power steering device2of a vehicle.

As shown inFIG. 1, in the electric power steering device2, the drive device outputs an assist torque for steering wheel operation based on various signals, such as a signal obtained from a torque sensor5that detects a torque produced in a column shaft4by an operation of a driver for rotating a steering wheel3, and a signal regarding travel speed information obtained from a Controller Area Network (CAN) of the vehicle, for example. The assist torque from the drive device1is transmitted to a column shaft4through a speed reduction gear6. A rotational movement of the column shaft4is converted to a straight movement of a rack shaft8by a pinion gear7. A steering wheel9is steered according to the amount of displacement of the rack shaft8.

The column shaft4, the pinion gear7, the rack shaft8and the like correspond to “a power transmission mechanism transmitting power between a steering wheel and a steered wheel.”

As shown inFIG. 2toFIG. 5, the drive device1has a one-body structure in which a motor10and a controller20for controlling the motor10are combined to have one body. The controller20is disposed on an opposite side relative to an output end16of the motor10. When the drive device1is installed in the vehicle, the motor10comes to a lower side in the vertical direction, and the controller20comes to an upper side in the vertical direction, i.e., relative to Earth.

As shown inFIG. 5, the motor10is a brushless motor, for example, and is provided with a stator11and a rotor12. The stator11is formed in a cylindrical shape with a magnetic body, and is supported by a front frame end13on one axial end, and is supported by a frame end part31on the other axial end. The frame end part31is a part of a heat sink30provided for the controller20, which is described later.

The stator11has a coil14wound on a slot. The rotor12is formed in a cylindrical shape with a magnetic body, and is positioned at a radial inside of the stator11. By “radial inside,” it is meant that the rotor12is formed inside of the stator11, where a radius of the rotor12from the rotor12to a motor shaft O less than a radius of the stator11from the stator11to the motor shaft O, when viewing through the motor shaft O. The rotor12is rotatable relative to the stator11. A shaft15of the rotor12is rotatably supported by a bearing17of a front frame end13on one end, and is rotatably supported by a bearing18of a frame end part31on the other end.

The stator11in the motor10generates a rotating magnetic field when an electric power is supplied to the coil14from the controller20, and the rotor12and the shaft15rotate about the shaft according to such magnetic field.

As shown inFIG. 3toFIG. 5, the controller20has the heat sink30that is Integrally formed with the frame end part31, a substrate40disposed on an away side of the heat sink30relative to the motor10, and other parts. The motor side of the substrate40has a connector50attached to the substrate40. Further, the heat sink30and the substrate40are protected by a cover60having a cup-shape, i.e., a cylindrical and bottom-closed shape.

The heat sink30has a one body structure, combining the frame end part31that covers a substrate side of the stator11and the rotor12and the heat receiving part32that extends from the frame end part31toward the substrate40. The heat sink30is formed by casting or cutting, for example, with a material such as aluminum etc. The heat sink30serves as an outer shell of the motor by providing the frame end part31, and absorbs heat generated by the electronic components41or the like by the heat receiving part32when those components41receive an electric power.

The heat sink30has a concave portion33indenting from a substrate side to a motor side. The connector50is positioned in the concave portion33. The heat receiving part32is positioned at a radius inside relative to the concave portion33. An end face321of the heat receiving part32, which faces the substrate40, is in parallel with the substrate40, and is also in parallel with the electronic components41Implemented on a heat sink side surface of the substrate40, and adjoins or contacts the electronic components41. Thereby, the heat sink30can reserve a large heat capacity without creating an excess unoccupied space in the cover60. As shown inFIGS. 3 and 6, the heat sink30has a hole-like space61for a connection of a motor line19through the heat sink30, i.e., for the motor line19to pass the heat sink30for connecting the coil14of the motor10and the substrate40. The motor line19passes through the space61from the motor side, and pierces a through hole of the substrate40, and protrudes from an outer face of the substrate40. In this case, the outer face of the substrate40is a surface of the substrate looking away from the motor10.

The drive device1of the present embodiment is provided with only one substrate40. As shown inFIG. 3toFIG. 6, the substrate40is, for example, a multilayer printed board40, and is fixed to the heat sink30with four screws35respectively screwed in a tapped hole that is bored in a supporter34of the heat sink30. The substrate40is perpendicularly disposed relative to the motor shaft O (refer toFIG. 5).

The heat sink side surface of the substrate40bears the following components. That is, the electronic components41that have switching elements, e.g. Metal Oxide Semiconductor Field Effect Transistor (MOSFET), for example, a rotational angle sensor42that detects the position of the rotor12, and an integrated circuit43for a control of an electric power supply to the coil according to the position of the rotor12are mounted on the heat sink side of the substrate40. Further, inFIG. 6, a dashed line shows an example of the electronic components41, the rotational angle sensor42and the integrated circuit43mounted on the heat sink side of the substrate40, as well as the substrate40itself.

The electronic components41, the rotational angle sensor42, and the integrated circuit43mounted on the heat sink side of the substrate40respectively have a flat shape, i.e., the width and the length of them longer than their heights that is measured along a motor shaft direction. Further, the integrated circuit43and the electronic components41respectively generate relatively large amount of heat when an electric power is supplied thereto.

The electronic components41mounted on the heat sink side of the substrate40and the heat sink30are separated by an insulated heat dissipation material which is not illustrated in the drawing. The Insulated heat dissipation material is a heat dissipation gel (i.e., may also be designated as a “heat dissipation grease”) or a heat dissipation sheet, for example, and prevents air to interpose between the electronic components41and the heat sink30, thereby improving thermal conductivity between them.

The electronic components41mounted on the substrate40function either as a three-phase inverter circuit for supplying an electric power to the motor10or a power switch for intercepting an electric power supplied from the connector50to the three-phase inverter circuit. The three-phase inverter circuit supplies an electric power to the coil14of the motor10according to the instruction from a microcomputer46.

The surface of the substrate40looking away from the heat sink30bears other components, such as a capacitor44, a choke coil45, and the microcomputer46, for example. The capacitor44and the choke coil45make up a filter circuit. Further, the capacitor44assists the electric power supply to the inverter circuit. Each of the capacitor44and the choke coil45has a greater height along the motor shaft direction in comparison to the electronic components41having a switching element. Further, the capacitor44and the choke coil45generate relatively small amount of heat when receiving the electric power supply as compared with the electronic components41having a switching element. Thus, almost all electronic components for controlling the electric current supply to the motor10are mounted on one substrate40, either on the heat sink side or on the other side of the substrate40.

The cover60is formed in a bottom-closed cylinder shape, and covers the substrate40and the heat sink30. The cover60, i.e., at its edge62, overlaps with an outside of the frame end part31of the heat sink30.

As shown inFIG. 3toFIG. 6, the connector50is attached to the motor side of the substrate40, and is positioned in the concave portion33of the heat sink30. The connector50is an electronic component having a large volume among the electronic components41that make up the controller20compared with the capacitor44, the choke coil45and the like. By positioning the connector50on the motor side of the substrate40and in the concave portion33of the heat sink30, the dimension of the controller20along the motor shaft direction is reduced without creating excess unoccupied space in the cover60.

The connector50has a connector body51, multiple terminals52, an upper flange53, a lower flange54, a right flange55, and a left flange56.

The connector body51extends from an inside of the cover60toward an outside thereof. Further, the connector body51has an opening57to which an external terminal is connectable. The opening57is positioned on a radial outside of the connector body51, i.e., on an outer part of the connector body51, relative to the motor shaft O. Also, the opening57faces outward relative to, or outward from the motor shaft O. An end face of the connector body51facing the motor10is separated from the bottom of the concave portion33of the heat sink30by a small gap space. The gap space between the end face of the connector body51and the bottom of the concave portion33of the heat sink30is designated as an air flow space58.

The multiple terminals52are molded by the connector body51, and both ends of respective terminals52are exposed from the connector body51. That is, one end of a terminal52is exposed in the opening57of the connector body51, and the other end of the same terminal52protrudes from the connector body51on an opposite side of the opening57, toward the heat receiving part32, and then toward an upper direction in terms of gravity wise, to be connected to the substrate40. Further, each of those terminals52pierces a through hole of the substrate40to protrude from the away side of the motor10. Therefore, each of those terminals52are soldered at the same time with the motor lines19protruding from the terminals52.

From the external terminal that is connected to the opening57of the connector body51, the terminals52receive an electric current to be supplied from a battery to the motor10, a signal from the torque sensor5, a signal of travel speed information, and the like. The terminals52transmit those electric current and signals to an electronic circuit provided on the substrate40.

The periphery of the connector body51has flanges, i.e., the upper flange53prolonged away from the motor10as a part of the connector body51, the lower flange54prolonged toward the motor10as a part of the connector body51, and the right flange55and the left flange56which connect the upper flange53and the lower flange54.

InFIG. 4, for the ease of understanding, the cover60is shown in a partially-cut manner on the left side, with hidden components under the cover60on the right side drawn with a broken line.

As shown inFIG. 4, the upper flange53, the right flange55, and the left flange56are formed inside the cover60. On the other hand, the lower flange54is exposed to the open air from the cover60.

The upper flange53, the right flange55and the left flange56are either positioned very close to an inner surface of the cover60, i.e., with only a small gap interposed between the flanges and the cover60, or are abutted to the inner surface of the cover60. In such manner, the water from outside of the cover60is prevented from intruding into an inside of the cover60via a labyrinth path that is formed between those flanges and the inner surface of the cover60. Further, even when water has intruded into an Inside of the cover60, the water is discharged from a portion541of the lower flange54which is exposed from the cover60, or from an opening542that is positioned on a lower side of the labyrinth path with a help of the gravity.

The first embodiment of the present disclosure provides the following effects.

(1) According to the first embodiment, the drive device1has a large size electronic component41, i.e., the connector50, of the controller20positioned on the motor side of the substrate40. The heat sink30in the controller20has a one-body structure, combining the frame end part31that covers the substrate facing side of the motor10and the heat receiving part32that extends from the frame end part31at a radial inside position of the connector50into one body. Here, “radial inside” means that the heat receiving part32extends within an area defined by a radius from the motor shaft O to the connector50, when viewed at a direction through of the motor shaft O, or in an axial direction of the motor10. Therefore, no excess unoccupied space is created inside the cover60that covers the substrate40in a bottom-closed cylinder shape, while achieving a smaller along-the-motor-shaft dimension of the drive device1.

Further, by closely positioning the away-from-motor end face321of the heat receiving part32to the substrate40, the drive device1acquires a large heat capacity for the heat sink30, and heat from the heat generating components41on the substrate40is easily dissipated. Therefore, the drive device1is enabled to supply a large electric current to the electronic components41mounted on the substrate40.

(2) According to the first embodiment, the heat sink30has the concave portion33indented from the substrate side to the motor side. The connector50is positioned in the concave portion33of the heat sink30. Thereby, the drive device1is enabled to have a smaller along-the-motor-shaft dimension.

(3) According to the first embodiment, the end face of the heat receiving part32of the heat sink30facing the electronic components41is in parallel with the substrate40. The electronic components41mounted on the substrate40and facing on the heat receiving part32are interposed with the insulated heat dissipation material from the heat receiving part32of the heat sink30.

Therefore, the gap between the electronic components41and the heat receiving part32is reduced to a small dimension, for enabling the drive device1to have a smaller volume. Further, heat conductivity between the electronic components41and the heat sink30is improved by providing the insulated heat dissipation material in such gap space.

(4) According to the first embodiment, the terminals52of the connector50respectively have one end exposed from the opening57of the connector body51, and have the other end protruding from the other side of the connector body51relative to the opening57to extend upward and to be connected to the substrate40.

In such manner, even when water intrudes into the inside of the cover60from outside, the gravity pull toward the vertical downward prevents the water from being carried toward the above-positioned substrate40along the terminals52.

(5) According to the first embodiment, the upper flange53, the right flange55, and the left flange56of the connector50are positioned in an inside of the cover60. The lower flange54of the connector50is exposed to the open air from the cover60.

Therefore, the gap between the upper flange53, the right flange55, the left flange56and the cover60is formed as the labyrinth path. The labyrinth path of the drive device1prevents the water from intruding into an inside of the cover from outside.

Further, even when the water has intruded into the labyrinth path, the water is discharged from the part541of the lower flange54exposed from the cover60or from the opening542of the labyrinth path positioned at the lower part that utilize gravity pull.

(6) According to the first embodiment, the air flow space58is formed between the end face of the connector body51facing the motor10and the bottom of the concave portion33of the heat sink30.

In such manner, even when water intrudes into the inside of the cover60from outside, the water is prevented from being kept between the connector body51and the heat sink30, and is discharge to the outside of the cover60.

(7) According to the first embodiment, the electronic components41having a switching element are mounted on the heat sink side of the substrate40, and other electronic components44and45, which has a larger along-the-motor-shaft dimension than the components41, are mounted on the other side of the substrate40, i.e., on a surface facing away from the heat sink30.

In such manner, the heat sink side of the substrate40does not have any tall electronic components, such as the components44and45, which allows the heat sink30to have a larger volume, i.e., a larger heat capacity, because the height of the heat sink30is increasable up to the height of the connector50. Therefore, by increasing the heat capacity of the heat sink30, the electronic components41is enabled to have a larger electric power supply, which leads to an increased output of the motor10.

(8) According to the first embodiment, the motor line19pierces through a through hole of the substrate40to protrude from the away side of the substrate40relative to the motor10. Further, the terminals52of the connector50extend from the connector body51on an opposite side of the opening57to be connected to the substrate40and to protrude from the away side of the substrate40through the through hole of the substrate40.

In such manner, the motor line19and the terminals52are soldered to an electronic circuit on the substrate40at the same time from the same side of the substrate40. Thus, the workability of the manufacturing process for manufacturing the controller20is improved.

(9) The electric power steering device2of the first embodiment has an improved installability in the vehicle based on the smaller volume and dimension of the drive device1along the motor shaft direction.

Second Embodiment

The second embodiment of the present disclosure is shown inFIGS. 7 and 8. The same numerals as the first embodiment are used to represent the same components as the first embodiment, for the brevity of the description.

According to the second embodiment, the heat sink30has a slit36allowing communication between the open air and the bottom of the concave portion33of the heat sink30, at a position on an outer wall of the frame end part31. The slit36may also be formed at other position in an inside of the cover60, as long as it allows communication between the open air and the bottom of the concave portion33of the heat sink30, and the shape and the number of the slit36may be arbitrarily defined.

According to the second embodiment, even when water intrudes into the inside of the cover60from the outside, the water can be discharged to the outside through the slit36from the air flow space58that is formed in the gap space between the end face of the connector body51facing the motor10and the bottom of the concave portion33of the heat sink30.

Other Embodiments

In the embodiment mentioned above, the drive device1is described as a “column assist” type drive device in the electric power steering device2, which assists a rotation of the column shat4. In other embodiments, the drive device1in the electric power steering device2may be a “rack assist” type drive device, which assists a translational movement of the rack shaft8.

In the embodiment mentioned above, the motor10of the drive device1is a brushless motor, and the electronic components41having a switching element that is used in the controller20is described as a component of the three-phase inverter circuit or the like that supplies an electric power to the brushless motor.

On the other hand, in other embodiments, the motor10of the drive device1may be a motor with a brush, for example, and the electronic components41in such case may be a component of an H bridge circuit that supplies an electric power to that motor10.

The embodiment mentioned above describes the drive device1used in the electric power steering device2.

On the other hand, in other embodiments, the drive device1may be applied to various devices other than the electric power steering device2.

The embodiment mentioned above describes the motor10of the drive device1functioning as an electric motor. However, the motor10of the drive device1in other embodiment may be functioning as a generator.

Although the present disclosure has been described in connection with preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art, and such changes, modifications, and summarized scheme are to be understood as being within the scope of the present disclosure as defined by appended claims.