Drive unit with motor and control unit

A drive unit used in an electric power steering device has a motor and a control unit. A motor wire of the motor has a terminal, which is engaged with a power board side terminal of the control unit to electrically couple the motor and the control unit. In such structure, the motor and the control unit may be electrically coupled and decoupled, without the use of a special tool. Further, a terminal holder is disposed on an opening of the motor by a first short protrusion and a second short protrusion, thereby coupling the terminal to the motor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority of Japanese Patent Applications No. 2011-106364 filed on May 11, 2011, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a drive unit which has a motor and a control unit for controlling the motor in one body.

BACKGROUND

Conventionally, an electric power steering device having a drive unit is widely used, in which the drive unit assists a steering operation of a driver, and the drive unit has a motor and its control unit disposed in a combined manner. The electric power steering device disclosed in Japanese Patent Laid-Open No. 2003-204654 (JP '654) has an electrical connection between the motor and the control unit that is enabled by coupling a bus bar extending from the control unit to a winding wire terminal in a motor case by using a screw, thereby allowing a user to replace a broken part.

However, the structure of the electric power steering device in JP '654 does not allow the separation of the control unit from the motor without removing the screw that is used for electrical connection therebetween. Further, for removing the screw, the drive unit has to be removed from a column shaft that is connected to a steering wheel. In other words, such structure does not allow an easy removal of the control unit without first removing the drive unit from the column shaft.

SUMMARY

In an aspect of the present disclosure, the drive unit includes a motor, a control unit, an engaging unit, and a hold unit. The motor is housed in a motor case, where the motor case may have a cylindrical shape with a bottom wall disposed at one end. Additionally, the bottom wall may define an opening. The motor further includes a stator having a plurality of winding wires corresponding to multiple phases wound thereon, a rotor disposed inside of the stator, and a shaft disposed inside of and coupled to the rotor, such that the rotor and the shaft rotate relative to the stator as one. In addition, the motor may include a plurality of motor wires that electrically couple to the winding wires of the stator, and extend into the opening of motor case.

The control unit is disposed on one axial side of the motor, and has a semiconductor module that includes a switching element for switching electricity to the winding wires and a connection terminal that electrically couples to the switching element. In addition, the control unit includes a controller case to house the semiconductor module

The engaging unit is disposed between the motor wire and the connection terminal, and is mechanically engagable with either the motor wire (23) or the connection terminal (371) to electrically couple the motor wire and the connection terminal. The hold unit holds or secures the engaging unit with either the motor wire or the connection terminal, thereby establishing an electrical connection between the motor and the control unit.

When the engaging unit engages with either the motor wire or the connection terminal, the motor wire is electrically coupled to the connection terminal. Without detaching the drive unit from the column shaft, when the engagement of the engaging unit with one of those parts is released, the motor wire and the connection terminal is electrically decoupled. In other words, without using a special tool, the motor and the control unit are electrically coupled and decoupled with ease.

When the motor and the control unit are attached to the column shaft by a screw that pierces the drive unit from the control unit side to the motor side, as provided in the prior art, it may not be possible to detach the motor and the control unit without removing the drive unit from the column shaft. According to the drive unit of the present disclosure, the control unit is attached to the motor on one side and the column shaft is attached to the motor on the other side. Therefore, with the help of the engaging unit, the motor and the control unit are coupled and decoupled with ease, and without causing any harm to other functions of the drive unit.

The drive unit described above is equipped with the engaging unit and the hold unit to hold/assist with the structural coupling between the engaging unit and one of the motor wire and the connection terminal. In addition the engaging unit holds/assists with the electrical coupling between the motor wire and the connection terminal. When the motor and the control unit are attached and detached, the engaging unit receives a force in an axial direction of the drive unit. The hold unit holds the engaging unit so that a relative position of the engaging unit against one of the motor and the control unit does not change. In such manner, the engaging unit securely releases mechanical engagement with the motor wire or the connection terminal, and securely disconnects electrical connection between the motor wire and the connection terminal. Further, when the motor and the control unit are reattached, the engaging unit securely enables mechanical engagement with one of the motor wire and the connection terminal, and securely enables electrical connection between the motor wire and the connection terminal.

In addition to the above configuration, the engaging unit is a terminal having an engagement portion to be engaged with the connection terminal, and the hold unit is a terminal holder being disposed fixedly on the opening of the motor case and houses the terminal.

In addition to the above configuration, the terminal holder has two parts, a first holder part and a second holder part. The first holder part has a first short protrusion at a base end to affix on the opening, which protrudes from a side that is opposite to a terminal holding side. The second holder part also has a second short protrusion at a base end to affix on the opening, which protrudes from a side that is opposite to a terminal holding side. Further, the second holder part has a pivot, which protrudes in a direction that is substantially perpendicular to the second short protrusion at a position closer to a center of the second holder part relative to the second short protrusion. The first holder part and the second holder part are coupled via the pivot in a rotatable manner, for opening and closing the terminal holder. When the terminal holder is in an open state, the first and second short protrusions are insertable into the opening of the motor case, and when the terminal holder is in a closed state, the first and second short protrusions couple with an inner edge of the opening.

When the terminal holder is disposed on the motor case, the terminal holder is inserted into the opening in the open state. A holder-fixed side of the terminal holder, which is on both sides of the “thin-plate-shape” holder, has the first short protrusion or the second short protrusion. In the open state, the terminal holder is insertable into the opening, since the distance between a tip face of the first short protrusion and a tip face of the second short protrusion are designed to be shorter than a width of the opening. When the terminal holder is closed after insertion into the opening, the distance between the tip face of the first short protrusion and the tip face of the second short protrusion becomes greater than the width of the opening, thereby fixing the terminal holder onto the opening. By devising such structure, the terminal holder and the terminal being held therein are prevented from being pulled out from the bottom wall of the motor case when the control unit is removed from the motor.

In addition to the above configuration, the first holder part has a first long protrusion, which protrudes from a side that is opposite to a terminal holding side, at a position that is closer to a center of the first holder part relative to the first short protrusion. The projecting length of the first long protrusion is longer than the projecting length of the first short protrusion. Further, the second holder part has a second long protrusion, which protrudes from a side that is opposite to a terminal holding side, at a position that is closer to a center of the second holder part relative to the second short protrusion. The projecting length of the second long protrusion is longer than the projecting length of the second short protrusion. When the terminal holder is in the closed state, the first and second long protrusions are positioned on an upper surface of the inner edge of the opening.

When the terminal holder is attached to the bottom wall of the motor case, to be put in the closed state, the first long protrusion and the second long protrusion are in abutment to the opening and an upper surface of the inner edge. In such case, the distance between a tip face of the first long protrusion and a tip face of the second long protrusion is designed to have a greater value than the width of the opening, thereby preventing the long protrusions from entering into an inside of the motor case through the opening. Therefore, by devising such structure, the terminal holder and the terminal being held therein are prevented from entering into the motor case.

In addition to the above configuration, when the terminal holder is in the open state, the tip face of the first/second short protrusions is substantially in parallel with an inner wall of the opening. By devising such structure, the tip face of the first/second short protrusions is not caught by the inner edge of the opening when the terminal is inserted into the opening, that is, when the tip face of the first/second short protrusions enters into the inside of the motor case through the opening. Further, by devising such structure, the terminal holder is inserted further/deeper into the inside of the motor case, relative to the other shape (e.g., a square shape) of a tip of the first/second short protrusions.

In addition to the above configuration, when the terminal holder is in the open state, an abutment face of the first/second long protrusions abutted to the upper surface of the inner edge of the opening is substantially in parallel with the inner edge of the opening. When the terminal holder is inserted into the opening in the open state, the first/second long protrusions abut to the upper surface of the inner edge of the opening. By devising such structure, i.e., the above-described parallel shape of the abutment face of the first/second long protrusions, it is advantageous in terms of a deeper insertion of the terminal holder into the inside of the motor case, relative to a tip of the longer protrusions having the square shape.

DETAILED DESCRIPTION

Details are discussed regarding the plural embodiments of the present disclosure based on the drawings as follows. Further, like parts have like numbers in the following embodiments, with the details of each of such parts provided only for the first appearance in the embodiment.

One Embodiment

Details are discussed regarding a drive unit1for the first embodiment of the present disclosure based onFIGS. 1 to 14B.

The drive unit1is applied to an electric power steering device (i.e., “EPS” hereinafter). The drive unit1includes a motor2and a control unit3. With reference toFIG. 1, details regarding the electrical configuration of EPS is described. The drive unit1generates a rotation torque and applies such torque on a column shaft6through a gear7, which serves as a rotation axis of a steering wheel5of the vehicle, for assisting the steering operation by using the steering wheel5. When the steering wheel5is operated by a driver, the generated steering operation torque of the column shaft6is detected by a torque sensor8. In addition, speed of the vehicle is acquired from control area network (CAN). The steering operation torque detected by the torque sensor8and the speed of the vehicle provided by the CAN are used to determine the necessary steering assist that needs to be provided by the drive unit1. The control provided by the drive unit1, is not limited to EPS, but may also be used in other applications, such as anti-drifting control to automate a position of a vehicle within a lane, automate parking, or an auto-pilot of the vehicle itself.

The motor2is a three-phase brushless motor that rotates the gear7in a forward direction and a reverse direction (i.e., clockwise or counterclockwise direction). The operation of the motor2is controlled by the control unit3, through supply of electricity and a feedback from the operation of the motor2. The control unit3has a power unit100to supply a drive electric current for driving the motor2and a controller90to control driving of the motor2.

The power unit100has a choke coil76on a power supply line from a power source75, a capacitor77, and two inverters80,89. Two inverters80,89have the same configuration. Thus, only the inverter80is described.

The inverter80has MOSFETs81,82,83,84,85,86(i.e., a metal-oxide-semiconductor field-effect transistor, or “MOS” hereinafter), which is a kind of field effect transistor. MOSs81,82,83,84,85,86control its conductivity between the source and the drain based on a gate voltage, which is turned ON (i.e., conducting) or OFF (i.e., intercepted). Further, MOSs81,82,83,84,85,86serve as “a switching element.”

MOS81has its drain coupled to the power supply line, and has its source coupled to the drain of MOS84. The source of MOS84is coupled to the ground. The connection point between MOS81and MOS84is coupled to a U phase coil of the motor2.

MOS82has its drain coupled to the power supply line, and has its source coupled to the drain of MOS85. The source of MOS85is coupled to the ground. The connection point between MOS82and MOS85is coupled to a V phase coil of the motor2.

MOS83has its drain coupled to the power supply line, and has its source coupled to the drain of MOS86. The source of MOS86is coupled to the ground. The connection point between MOS83and MOS86is coupled to a W phase coil of the motor2.

Further, the inverter80has power relays87,88. The power relays87,88are provided as a MOSFET that is similar to MOSs81,82,83,84,85,86. The power relays87,88are disposed between MOSs81,82,83and the power source75, and can intercept an electric current that may flow at a time of abnormality. More practically, the power relay87is disposed to intercept an electric current flowing toward the motor2side when a snapping trouble or a short-circuit trouble occurs. Further, the power relay88is disposed for protection of reverse connection, preventing an electric current flowing in a reverse direction.

A shunt resistor99is electrically coupled between MOSs84,85,86and the ground. The electric current/voltage flowing through or applied on each of the U phase coil, the V phase coil, and the W phase coil is determined by detecting the voltage applied on the shunt resistor99.

The choke coil76and the capacitor77are electrically coupled to a point between the power source75and the power relay87. The choke coil76and the capacitor77constitute a filter circuit, and reduces a noise from other devices that share the power source75with the drive unit1. Further, a noise from the drive unit1to the other devices sharing the power source75with the drive unit1is also reduced by such filter circuit.

A capacitor78is coupled to a point between the power supply side of MOSs81,82,83and the ground, which are on a power source line side. The capacitor78assists power supply for MOSs81,82,83,84,85,86by storing an electric charge, and/or suppresses noise components, such as a surge voltage.

The controller90includes a pre-driver91, a custom IC92, a rotation angle sensor93serving as a rotation detecting element, and a microcomputer94. The custom IC92includes a regulator unit95, a rotation angle sensor signal amplifier96and a detection voltage amplifier97as function blocks.

The regulator unit95is a stabilization circuit stabilizing a power supply. The regulator unit95stabilizes a power supply supplied to various parts. For example, an operation of the microcomputer94is stabilized by a stable voltage of 5 volts from the regulator unit95.

The rotation angle sensor93detects a rotation position signal of the motor2, and outputs such signal to the rotation angle sensor signal amplifier96. The rotation angle sensor signal amplifier96amplifies the rotation position signal, and outputs the amplified signal to the microcomputer94.

The detection voltage amplifier97detects a voltage between both ends of the shunt resistor99, and outputs the detected voltage to the microcomputer94after amplifying it.

The rotation position signal of the motor2and the voltage of shunt resistor99are transmitted to the microcomputer94. Further, the microcomputer94receives a steering operation torque signal from the torque sensor8and the vehicle speed information via CAN. To provide the necessary assist for the steering operation, the microcomputer94controls the inverter80through the pre-driver91according to the rotation position signal of the steering wheel and the vehicle speed, when the steering operation torque signal and the vehicle speed information are received. More practically, the microcomputer94controls the inverter80through the pre-driver91by turning respective MOSs81,82,83,84,85,86ON or OFF. In other words, because six MOSs81,82,83,84,85,86have their gates coupled to the six output terminals of the pre-driver91, MOSs81,82,83,84,85,86are turned ON or OFF by changing the gate voltage by using the pre-driver91.

Further, the microcomputer94controls the inverter80based on the voltage of the shunt resistor99provided by the detection voltage amplifier97in order to approximate, to a sine wave, a wave shape of an electric current supplied for the motor2. Further, the controller90controls the inverter89in the same manner as it controls the inverter80.

With reference toFIGS. 2toFIG. 14B, the structure of the drive unit1in the present disclosure is described.FIG. 2is a cross-section along line II-II of the drive unit1inFIG. 4, whereFIG. 4provides a top view of the drive unit1.FIG. 3is a cross-section along line III-III line of the drive unit1inFIG. 4.FIG. 5is a perspective view of the drive unit1, andFIG. 6andFIG. 7are exploded perspective views of the drive unit1. As shown inFIG. 2and inFIG. 3, the drive unit1of the present embodiment has the control unit3disposed on one end of the motor2, to form a stacking structure of the motor2and the control unit3.

The motor2includes a motor case10, a stator20having a winding wire22wound thereon, a rotor25, and a shaft27. An outline of the motor2is defined by the motor case10. The motor case10is formed by a circumference wall11and a control-unit-side wall15to have a closed-end cylindrical form. The motor case10may be formed of metal or the like. On the end opposite of the control-unit-side wall15, the circumference wall11protrudes outward to form a brim part12, and an end frame13is affixed thereon by way of a fastener, such as a screw14. The end frame13may be made of metal such as aluminum.

A column19is disposed on the control-unit-side wall15of the motor case10. The column19may be made of aluminum or the like, and has a female screw part that has a female screw groove on its inner-surface and has a closing part. The female screw part protrudes from the outer-surface of the control-unit-side wall15, such that when the drive unit is in an assembled condition, the female screw part extends into the control unit3and is aligned with a cylinder member52, which is adjacent to a heat sink50of the control unit3. The other end of the cylinder member52extends and abuts to the inside of a cover member110of the control unit3. The cylinder member52is aligned such that the inside of the cylinder member52is aligned with a screw hole54on the cover member110. In such manner, as shown inFIG. 6, a through bolt53engages with the female screw part of the column19through the screw hole54and the inside of the cylinder member52. In other words, the motor2and the control unit3are coupled via the through bolt53.

With continuing reference toFIGS. 2 and 3, the stator20is arranged inside of the motor case10. The stator20may have 60 pieces of a radially-inwardly projecting pole. The projecting pole has a layered core of thin plates that are made of magnetic material and an insulator that is engaged on an axial outside of the layered core. The insulator has the winding wire22wound thereon. The winding wire22corresponds to each of a U phase coil, a V phase coil and a W phase coil, to form three phase winding wires.

A motor wire23extends from the winding wire22. The motor wire23extends from an attachment hole18of the control-unit-side wall15into the control unit3. The control-unit-side wall15defines the attachment hole18, which serves as an “opening,” by an attachment hole portion17, where the attachment hole portion17is provided as an inner edge of the control unit-side wall15.

The motor wire23is fixed onto a base portion311of a terminal31, which serves as an “engaging unit.” The terminal31is held by a terminal holder33, which serves as a “hold unit” (FIG. 3). Additionally, an engaging portion312, which is on the other end of the terminal31relative to the base portion311, engages with a power board terminal371, which serves as a “connection terminal” and is electrically coupled to the power board70(FIG. 6). The power board terminal371has one end electrically coupled to the power board70, and has the other end projected into a connector accommodation space37that houses the terminal holder33. Further, one end of the terminal holder33on the motor2side is engaged with the attachment hole portion17. The structure of a connector30comprising of the terminal31and the terminal holder33is described later.

The rotor25is disposed inside of the stator20, and is rotatable relative to the stator20. The rotor25may have cylindrical shape and is made of a magnetic material, such as iron. The rotor25has a rotor core251and a permanent magnet253attached on a radial outside surface of the rotor core251. The permanent magnet253has an N pole and an S pole arranged in turns.

The rotor core251defines a shaft hole252on an inner radial center of the rotor core251. The shaft27is affixed to the shaft hole252, and the shaft27is rotatably supported by a bearing271on the motor case10and a bearing272on the end frame13. The shaft27can thus rotate with the rotor25relative to the stator20(i.e. the stator remains stationary while the shaft27and rotor25rotate within the stator20and about a center axis X). The control unit3side of the shaft27extends into a shaft hole151defined at the radial center of the control-unit-side wall15of the motor case10, such that the shaft hole151is aligned with the shaft hole252of the rotor core251. Accordingly, the end of the shaft27on the control unit3side is exposed from the motor case10. Additionally, the diameter of the shaft hole151is greater than the outer diameter of the shaft27, so that the motor case10does not interfere with the rotation of the shaft27.

The end of the shaft27, which is closest to the control unit3, has a magnet28that rotates with the shaft27. The magnet28is fixed on a magnet holder disposed on the shaft27and is coaxial with the shaft27. The magnet28is exposed from the motor case10(FIG. 7). The magnet28is positioned in proximity to the surface of the control board40that faces the motor2, such that the shaft27does not penetrate the control board40.

Further, the shaft27has an output end29that extends past the end frame13. (i.e opposite end of the control unit3). The output end29extends into a gear box (not shown) that houses the gear7(FIG. 1). The shaft27engages with the gear7by way of the output end29, accordingly, the gear7receives an output torque from the output end29of the shaft27.

With continuing reference toFIGS. 2 and 3, detail regarding the control unit3is described in the following. The control unit3includes the control board40, the heat sink50, a power module60serving as the semiconductor module, the power board70, the cover member110, and an ECU housing120. The cover member110and the ECU housing120are equivalent to a “controller case” in claims.

The control unit3has a control connector45that couples the control unit3with external components and a power connector79. Majority of the components of the control unit3are provided within a circular outer boundary of the drive unit10, except for certain parts that are primarily positioned external to and protrude from the ECU housing120, such as the power connector79. In addition, as shown inFIG. 3, the control unit3is arranged to have the heat sink50and the power module60substantially between the control board40and the power board70, where the control board40is provided on the motor2side of the control unit3.

The control board40may be provided as four levels of boards formed by a glass epoxy, and is formed in a board shape, such that the control board40may partially or substantially fit an area relative to motor case area. Various electronic parts constituting the controller90are disposed on the control board40. Specifically, the pre-driver91, the custom IC92, and the microcomputer94are disposed on the side of the control board40that faces the power board70. Further, the rotation angle sensor93is disposed on the side of the control board40that faces the motor2. The rotation angle sensor93is disposed at a position facing the magnet28. Further, the magnet28and the rotation angle sensor93are arranged coaxially on an axial rotation line of the shaft27and rotor25. The rotation angle sensor93detects an angle of rotation of the shaft27by detecting the change of the magnetic field caused by the rotation of the magnet28, which rotates with the shaft27and the rotor25as one body.

On the control board40, a through hole is formed along the periphery of the control board40to couple to a control terminal64of the power module60. Further, the control board40is coupled to the control connector45.

With reference toFIG. 2, the control connector45is positioned off of an outer surface of the ECU housing120, such that it extends in a direction parallel to the center axis X towards the motor2. The control connector45is positioned adjacent to the outer surface of the motor case10, and a wiring for receiving an input of signals, such as signals from the CAN, is connectable to the connector45from a direction along an axis of the motor2from the motor2side. In the present embodiment, the control connector45has an opening directed towards the motor2side of the drive unit1(FIG. 2).

The heat sink50may be made of a material having high heat conductivity, such as aluminum. A base-surface of the heat receiving portion55, which does not have the control connector45, faces the control board40, such that the heat receiving portion55is positioned in a direction that is substantially perpendicular to the control board40or the control-unit-side wall15. Additionally, a longitudinal-surface of the heat receiving portion55is perpendicular to the base-surface and substantially parallel to the center axis X. There are two heat receiving portions55disposed in parallel with each other, and along each of the two heat receiving portions55, the power module60is disposed.

The power module60is vertically positioned on an outer-surface of the heat sink50. Between the power module60and the heat sink50, a heat radiation sheet (not illustrated) is disposed. The power module60with the heat radiation sheet is attached to the heat sink50by way of a fastener, such as a screw69. In such manner, the power module60is held by the heat sink50with the heat radiation sheet interposed therebetween. The heat produced from the power module60is dissipated to the heat sink50through the heat radiation sheet.

Further, though not illustrated, one side of the power module60on the heat receiving portion55side has a part of the wiring pattern exposed from a mold part61of the power module60as a metal radiation part, for contacting and efficiently dissipating heat to the heat receiving portion55of the heat sink50. The heat radiation sheet conducts heat from the power module60to the heat receiving portion55, and maintains insulation of the heat receiving portion55from the power module60.

The power module60includes MOSs81,82,83,84,85,86, which are used as a switching element for switching supply of an electric current to the winding wire. The power module60also includes MOSs81,82,83,84,85,86,87,88and the shunt resistor99, which are electrically coupled by way of, for example, copper wires, and is molded by the mold part61.

A relation between the power modules60and the circuit inFIG. 1is now described. One of the power modules60corresponds to the inverter80(FIG. 1), and has MOSs81,82,83,84,85,86, the power relays87,88, and the shunt resistor99as shown inFIG. 1. In other words, the present embodiment has MOSs81,82,83,84,85,86, the power relays87,88and the shunt resistor99molded as one body by a resin mold. The other one of the power module60corresponds to the inverter89, and has MOS, a power relay and a shunt resistor for constituting the inverter89. Thus, in the present embodiment, one power module60corresponds to one system of an inverter circuit. Further, one heat receiving portion55is disposed corresponding to one power module60that constitutes one drive system.

The power module60has the control terminal64and a power terminal65projecting from the mold part61. The control terminal64is formed on a face on an end of the mold part61, which is perpendicular to the heat receiving portion55of the heat sink50. Further, the power terminal65is formed in parallel with the face having the control terminal64. In the present embodiment, the power module60has the control terminal64arranged on the control board40side, and has the power terminal65arranged on the power board70side, both residing on the heat receiving portion55of the heat sink50with its orientation vertically aligned to the heat receiving portion55. In other words, the control terminal64protrudes from the control board40side, and the power terminal65protrudes from the power board70side.

The control terminal64is inserted into a through hole of the control board40, and is electrically coupled to the control board40by way of, for example, soldering. Through the control terminal64, a control signal from the control board40is transmitted to the power module60. Further, the power terminal65is inserted into a through hole formed on the power board70, and is electrically coupled to the power board70by way of, for example, soldering. An electric current supplied for the winding wire22through the power terminal65is then supplied for the power module60.

The power board70may be formed by a glass epoxy, and has four layers of thick copper pattern, to have a board shape, such that the power board70may partially or substantially fit an area relative to motor case area. The power board70has a power wire formed thereon that allows a winding wire electric current to flow to the winding wire22through the power board terminal371and the terminal31.

The choke coil76and the capacitors77,78are disposed on the side of the power board70that faces the control board40(i.e. the motor2side). The choke coil76and the capacitors77,78are disposed in a space formed in an inside of the heat sink50. Further, in an axial direction of the motor2, the choke coil76and the capacitors77,78are disposed at a position between the power board70and the control board40.

The choke coil76is formed in the shape of a cylinder which has a longitudinal (i.e., axial) dimension being shorter than a radial dimension that is taken along the radius of the cylinder. The choke coil76is arranged so that the axis of the coil76is substantially perpendicular to an axis of the shaft27.

Both of the capacitors77,78are aluminum electrolytic capacitors. Further, the capacity of four capacitors78is larger than the capacity of the capacitor77. Further, the types of the capacitors77,78are not only the aluminum electrolytic type, but may also be other types of capacitors.

Further, the power connector79is coupled to the power board70. The power connector79is formed on an outer wall of the ECU housing120. In the present embodiment, the power connector79is disposed on the other side of the control connector45across the rotation axis of the motor2(FIGS. 2 and 5). The power connector79is coupled to the power source75, with its wiring connectable in a substantially perpendicular direction against a rotation axis of the drive unit1. Through such connection, the electricity is supplied from the power source75via the power connector79for the power board70. Further, the electricity from the power source75is supplied for the winding wire22wound on the stator20, through the power connector79, the power board70, the power module60, and the motor wire23.

With reference toFIGS. 6 and 7, the connector accommodation space37is defined inside of the ECU housing120. The connector accommodation space37is formed at two positions inside of the ECU housing120and next to the outer wall, such that the outer wall closest to the connector accommodation space37does not have the control connector45or the power connector79. The connector accommodation space cover372is formed substantially as a rectangular member with a bottom and an opening that opens towards the motor2side. The power board terminal371is disposed on the control unit3side of the connector accommodation space cover372.

The structure of the connector30, which connects the power board terminal371to the motor wire23is described with reference toFIGS. 8A-9D.FIGS. 8A and 8Billustrate a perspective view of the terminal31of the connector30, andFIGS. 8C and 8Dillustrate a perspective view of the terminal holder33.FIG. 9Aillustrates a top view of the connector30, where the terminal31is held in the terminal holder33,FIG. 9Billustrates a front view of the connector30,FIG. 9Cillustrates a bottom view of the connector30, andFIG. 9Dillustrates a side view of the connector30.

With reference toFIGS. 8A-8C, the terminal31, which may be made of metal, has the base portion311for receiving and fixedly coupling to the motor wire23. In addition, the engaging unit312engages with an end of the power board terminal371. One terminal31may couple with three motor wires23and with three power board terminals371. The cross-section of the base portion311is provided substantially in a “U” shape, and the engaging unit312, which is on the opposite side of the terminal31relative to the base portion311, has an insertion slit315into which an end of the power board terminal371is inserted. The insertion slit315is formed by two flat plates facing each other, and the two flat plates are biased against each other by an elastic force of the material that forms the terminal31. The end of the power board terminal371inserted into the insertion slit315is bound by the two facing plates, accordingly, the terminal31engages with the power board terminal371.

The terminal holder33, which holds and supports the terminal31, may substantially have a cuboid shape and may be made of resin. The terminal holder33includes a first holder part34and a second holder part36, where the first holder part34and the second holder part36are configured to open and close at a pivot335disposed on a side wall365of the second holder part36.

The first holder part34is formed substantially in the shape of a flat board. On each side end of the first holder part34, an engager341and a pivot arm342are provided on an upper and lower portion of the first holder part34, respectively. The engager41and pivot arm342extend from the side of the first holder part34, and project towards the second holder part36. The second holder part36has a nail337disposed on both sides of an upper side surface of the second holder part36. The engager341engages with the nail337of the second holder part36to couple the first and second holder parts34,36in the closed state. The pivot arm342couples with the pivot335of the second holder part36, and serves as a center of rotation along which the terminal holder33opens and closes. In other words, the pivot arm342and the pivot335provide the center of rotation along which the first holder part34and the second holder part36couple and decouple, by way of the engager341and the nail337, to open and close terminal holder33.

The first holder part34has a first short protrusion344and a first long protrusion343in proximity to the pivot arm342, where the first short protrusion344and the first long protrusion343project in a opposite direction relative to the pivot arm342(i.e., project from a surface that is opposite to the surface facing the second holder part36). The first short protrusion334is provided below the pivot arm342(i.e. disposed on an opposite end of the first holder part34relative to the engager341). The first short protrusion344has a tip face344athat extends from the first short protrusion344in an opposite direction relative to the pivot arm342. In other words the tip face344aof the first short protrusion344is formed substantially in parallel with the axial direction of the terminal holder33when the terminal holder33is put in the closed state (FIG. 10B).

The first long protrusion343is extends from the pivot arm342in an opposite direction relative to the pivot arm342(i.e., extending from a face that is opposite to a second holder part36engaging face). A corner portion343aof the first long protrusion343on the first short protrusion344side is provides as a face of the first long protrusion343that is substantially perpendicular to the axis of the terminal holder33in the open state of the terminal holder33.

The second holder part36substantially has a U shape cross-section. Such shape of the second holder part36enables the engagement of the second holder part36with the first holder part34. On one end of the side wall365of the second holder part36, the nail337to engage the engager341on the first holder part34is formed. Further, the pivot335is formed on the other end of the side wall365. As shown inFIG. 8D, the combination of the pivot335and the pivot arm342of the first holder part34allows the rotation (i.e., opening and closing) of first holder part34and the second holder part36around the pivot335.

The first holder part34has a first short protrusion344and a first long protrusion343in proximity to the pivot arm342, where the first short protrusion344and the first long protrusion343project in a opposite direction relative to the pivot arm342(i.e., project from a surface that is opposite to the surface facing the second holder part36).

The second holder part36has a second short protrusion362and a second long protrusion361that extend from a surface that is opposite to the surface that faces the first holder part34. A tip face362aof the second short protrusion32is formed substantially in parallel with the axial direction of the terminal holder33when the terminal holder33is put in the closed state (seeFIG. 10B). A corner portion361aof the second long protrusion361on the second short protrusion362side is formed as a face that is substantially perpendicular to the axis of the terminal holder33in the open state of the terminal holder33.

The first holder part34defines an opening345in proximity to the center of the first holder part34. The second holder part34defines an opening363in proximity to the center of the second holder part34. The opening345and the opening362are substantially aligned when the terminal holder33is in the closed state. The opening363has a depression364formed thereon, defining a hole333to provide a through hole between the opening345,363and a lower portion of the terminal holder33(FIG. 9C).

Assembly steps of disposing the connector30on the drive unit1in a production process of the drive unit1are described with reference toFIGS. 8D,10A-14B.

InFIG. 8D, the first holder part34and the second holder part36are coupled via the pivot335and the pivot arm342, and are therefore in an opening closing enabled state.

InFIGS. 10A-11B, the terminal holder33in the open state is inserted, from the first short protrusion344side and the second short protrusion362side, into the attachment hole18that is formed on the control-unit-side wall15of the motor case10. As shown inFIGS. 10B and 11B, a distance L1from the tip face344aof the first short protrusion344to the tip face362aof the second short protrusion362is smaller than an opening width L2of the attachment hole18in a diameter direction of the motor2. Therefore, the first short protrusion344and the second short protrusion362are inserted into the motor case10without touching an inner wall171of the attachment hole18. Additionally, when the terminal holder33is placed into the attachment hole18, the motor wire23, which extend out from the attachment hole18, enter the terminal holder33via the depression364formed on the second holder part36(FIGS. 10A-11B).

InFIGS. 12 and 13, the terminal31is inserted into the terminal holder33that is supported by the control-unit-side wall15. Further, as the terminal31is inserted into the terminal holder33, the motor wire23enters the base portion311of the terminal31(FIG. 13). The motor wire23, which extend into the base portion311, is affixed to the base portion311by, for example, heat-caulking. Further, in a state that the connector30is fixedly attached on the motor case10, the motor wire23extending into the base portion311of the terminal31is also affixed onto the base portion311by, for example, heat-caulking.

With reference toFIGS. 14A and 14B, the first holder part34and the second holder part36are rotated around the pivot335and are coupled via the engager341and the nail337, thus establishing the connector30. A distance L3from the corner portion343aof the first long protrusion343to the corner portion361aof the second long protrusion361is greater than the opening width L2of the attachment hole18. Therefore, the terminal holder33is fixedly engaged with the inner edge17of the attachment hole18by the first long protrusion343and the second long protrusion361.

The connector30is fixed on the motor case10by binding the inner edge17of the attachment hole18between (i) a side face343bof the first long protrusion343and a side face344bof the first short protrusion344and (ii) a side face361bof the second long protrusion361and a side face362bof the second short protrusion362. In other words, the connector30and the motor case10are coupled by binding the inner edge17of the attachment hole18between the first long protrusion343and the first short protrusion344, and between the second long protrusion361and second short protrusion362.

Once the connector30is secured to the motor case10(FIG. 14A-14B), the control unit3is assembled on the motor case10. When the control unit3is disposed onto the motor case10, the connector30is housed in the connector accommodation space37of the ECU housing120. The connector30in the housed state establishes the engagement between the engaging unit312of the terminal31and the power board terminal371. Thus, the winding wire22and the power board70are coupled through the terminal31.

(Operation of Drive Unit1)

Here, details are discussed regarding the operation of the drive unit1.

The microcomputer94on the control board40generates a pulse signal that is generated by pulse-width modulation (PWM) control through the pre-driver91, based on the signals from the rotation angle sensor93, the torque sensor8, the shunt resistor99, and the like, for assisting the steering operation of the steering wheel5according to a vehicle speed.

The pulse signal is output to the two systems of the inverters80,89that are made by the power module60via the control terminal64, and controls an ON-OFF switching operation of MOSs81to86. In such manner, each phase of the winding wire22receives a sine wave electric current having a respectively different wave phase, thereby generating a rotating magnetic field. By receiving such a rotating magnetic field, the rotor25and the shaft27rotate as one body. Then, by the rotation of the shaft27, a driving force is output from the output end29of the motor2to the gear7on the column shaft6, for assisting the steering operation of the steering wheel5by the vehicle driver.

In other words, by the supply of the electric current for the winding wire22, the motor2is driven. Thus, the electric current supplied for the winding wire22may be designated as a driving current to drive the motor2.

Heat from MOSs81to88of the power module60, which is generated during the switching operations of the MOSs, is dissipated to the heat sink50through the heat radiation sheet to prevent the drive unit1from overheating. Further, the size of the stator20and/or the rotor25may be changed depending on the required output.

(A) When one of the motor2and the control unit3in the drive unit1is broken, the motor2or the control unit3, whichever having the trouble, is replaced by removing the motor2from the control unit3. According to the present embodiment, the winding wire22of the motor2and the power board70of the control unit3are electrically coupled by the connector30. Specifically, the power board terminal371of the power board70engages with the engaging unit312of the connector30. Therefore, when the control unit3is detached from the motor2, the control unit3is released in an axial direction of the motor2toward an opposite side of the output end29of the motor2and a smooth separation of the control unit3from the motor2is enabled. Specifically, the decoupling of the electrical connection between the control unit3and the motor2may be performed by without the use of any special tool, since the control unit3is electrically coupled to the motor2though the engaging unit312of the terminal31. In other words, the motor2and the control unit3may be easily attached and detached without the use of a special tool.

(B) The control unit3is disposed in an axial direction of the motor2, on an opposite side of the output end29. The motor2and the control unit3are attached at the column19by the through bolt53that is inserted from the cover member110into the cylinder member52. Therefore, the control unit3may be detached from the motor2without detaching the motor2from the column shaft6. That is, the control unit3may be detached from the motor2with the motor2still attached to the column shaft6.

(C) The distance from the tip face344aof the first short protrusion344to the tip face362aof the second short protrusion362changes depending on whether the terminal holder33is in the opening state or the closed state. When the terminal holder33is inserted into the attachment hole18of the control-unit-side wall15, the terminal holder33is in the open state. The distance L1from the tip face344aof the first short protrusion344to the tip face362aof the second short protrusion362is smaller than the opening width L2of the attachment hole18in the diameter direction of the motor2. Therefore, the terminal holder33in the open state can be inserted into the motor case10from the first short protrusion344side end from the second short protrusion362side end.

After the terminal holder33is inserted into the attachment hole18, the terminal holder33is positioned into the closed state by engaging the first holder part34with the second holder part36. When the terminal holder22is in the closed state, a distance L4from the tip face344aof the first short protrusion344to the tip face362aof the second short protrusion362becomes greater than the opening width L2of the attachment hole18in the diameter direction of the motor2. Therefore, when the control unit3is being pulled to be detached from the motor2, the terminal holder33remains secured to the motor case10and is prevented from being pulled out from the control-unit-side wall15.

(D) When the terminal holder33is inserted into the attachment hole18, and the terminal holder33is put in the closed state, the distance L3from the corner portion343aof first long protrusion343to the corner portion361aof the second long protrusion361becomes greater than the opening width L2of the attachment hole18in the diameter direction of the motor2. Therefore, when the terminal holder33is on the surface of the control-unit-side wall15and in the closed state, the terminal holder33is prevented from entering the motor case10via the attachment hole18.

(E) The tip face344aof the first short protrusion344and the tip face362aof the second short protrusion362are formed substantially in parallel with an axial direction of the terminal holder33. Therefore, when the terminal holder33is inserted in the attachment hole18in the open state, the tip face344aof the first short protrusion344and the tip face362aof the second short protrusion362do not touch the inner wall171of the attachment hole18. Further, in comparison to having the square shape tip face, the terminal holder33can be inserted deeper into the motor case10when the tip faces of the first short protrusion344and the second short protrusion362are tilted.

(F) When the terminal holder33is in the open state, the corner portion343aof the first long protrusion343on the first short protrusion344side and the corner portion361aof the second long protrusion361on the second short protrusion362side are formed substantially perpendicular to an axial direction of the terminal holder33(i.e. the corner portions343a,361ahave a slight taper). Therefore, when the terminal holder33is inserted into the attachment hole18in the open state, the terminal holder33is inserted deeper into the motor case10, in comparison to having a substantially square shape corner portion on the longer protrusions.

Other Embodiments

(a) It is assumed in the above embodiments that the terminal and the motor wire are coupled by heat caulking, and the terminal and the power board terminal are coupled by insertion. However, the connection between the terminal and those parts may use a different connection method. That is, the power board terminal may be heat-caulked to the terminal, and the motor wire may be engaged with the terminal by insertion. In such case, the connector may be disposed in the ECU housing.

(b) In the above embodiment, the motor wire is disposed to the base portion of the terminal by heat-caulking. However, the motor wire may be disposed in a different manner. That is, the motor wire may be welded, soldered or the like.

(c) In the above embodiment, the terminal and the power board terminal are coupled by the engagement of the engaging unit of the terminal with the power board terminal. However, the terminal and the power board terminal may be coupled in a different manner. The power board terminal may have the engaging unit, and the terminal may be inserted into the engaging unit of the power board terminal.

(d) In the above embodiment, a corner portion of the long protrusion on the short protrusion side is formed as a face that is substantially perpendicular to the axis of the terminal holder in the open state of the terminal holder. However, the corner portion of the long protrusion may have a different form from the above. That is, the corner portion may have a face that is not perpendicular to the axis of the terminal holder.

(e) In the above embodiment, the tip face of the short protrusion is formed as a plane surface which is, in the open state of the terminal holder, in parallel with the axis of the terminal holder. However, the shape of the tip face may be formed in a different shape. That is, the tip face may be a plane surface which is, in the closed condition of the terminal holder, in parallel with the axis of the terminal holder.