Permanent-magnet synchronous motor and electric power steering device

A permanent-magnet synchronous motor and an electric power steering device are driven by a first system including a first armature winding and a first control apparatus and by a second system including a second armature winding and a second control apparatus and are configured in such a way that if one system fails, driving by the one system is stopped but the driving is continued by the other system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2017/032190 filed Sep. 7, 2017.

TECHNICAL FIELD

The present invention relates to a permanent-magnet synchronous motor having magnetic-field poles composed of a permanent magnet and to an electric power steering device in which the permanent-magnet synchronous motor is utilized as a driving source.

BACKGROUND ART

As is well known, an electric power steering device plays a role of assisting steering torque for a driver of a vehicle such as an automobile to operate the steering wheel, by means of auxiliary torque produced, for example, by a driving-apparatus-integrated permanent-magnet synchronous motor that is integrated with a driving apparatus. In recent years, in an automobile automatic driving system, an electric power steering device plays a role of an actuator for automatically avoiding an obstacle on a road, detected by a vehicle camera, a vehicle radar, or the like, without involving the driver in the operation of steering. Thus, in such an electric power steering device, it is important that neither auxiliary torque for assisting the operation of the steering wheel nor torque required for avoiding an obstacle at a time when automatic driving is implemented is suddenly lost.

For example, in the case where in a permanent-magnet synchronous motor provided as a driving source for an electric power steering device, an armature winding provided in a stator fails due to short-circuiting, magnetic flux from a permanent magnet provided in a rotor rotates due to rotation of the rotor and hence is interlinked with the armature winding provided in the stator, which may cause a large short circuit current to flow through a low-impedance short circuit in the armature winding. In this case, as so-called reaction magnetic flux, the magnetic flux generated by the short circuit current produces braking torque that impedes rotation of the permanent-magnet synchronous motor, which may cause a malfunction in the operation of the electric power steering device.

In the case where in order to avoid the foregoing malfunction, the armature winding of the permanent-magnet synchronous motor is composed of two sets of armature windings that are electrically independent from each other, it is made possible that if one of the two groups of armature windings fails, energization of the failed one thereof is stopped and the other one thereof, which is normal, produces required torque.

For example, a permanent-magnet synchronous motor disclosed in Patent Document 1 is configured in the following manner: a stator winding is wound on alternate teeth among a great number of teeth in a stator iron core and the stator winding includes two sets of independent three-phase armature windings that are star-connected or delta-connected; because even if a short-circuit failure or the like occurs in one of the three-phase armature windings, the other one thereof is normal, it is made possible that the foregoing braking torque is reduced so that the reliability of the synchronous motor is raised.

PRIOR ART REFERENCE

Patent Document

[Patent Document 1] National Publication of International Patent Application No. 2010-531130

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, reaction magnetic flux generated by a short circuit current that flows due to a short-circuit failure in the one of armature windings is interlinked also with the other armature winding, which is normal, other than the short circuit in the one of the armature windings, in which the short-circuit failure has occurred; therefore, the reaction magnetic flux provides an effect to the driving voltage of the motor driving device connected with the normal armature winding and hence intended motor control becomes difficult. The reason therefor is that because the two sets of armature windings are wound on one and the same stator iron core, the magnetic path is shared by the two armature windings and hence the two armature windings are magnetically and tightly coupled with each other through a mutual inductance.

Therefore, it is an important theme that a permanent-magnet synchronous motor having two sets of armature windings and being utilized in an electric power steering device is configured in such away that the two sets of armature windings are not only electrically independent from each other but also not magnetically coupled with each other so that if one of the armature windings fails, steering operation is continued by means of the other one thereof, which is normal.

The present invention has been implemented in order to solve the foregoing problems in a permanent-magnet synchronous motor provided with two sets of armature windings; one objective thereof is to provide a permanent-magnet synchronous motor in which even if a system including one of the two sets of armature windings fails, desired torque can be obtained through a system including the other one of the two sets of armature windings.

In addition, another objective of the present invention is to provide an electric power steering device in which even if a system including one of the two sets of armature windings of a permanent-magnet motor as a driving source fails, desired torque can be obtained through a system including the other one of the two sets of armature windings.

Means for Solving the Problems

A permanent-magnet synchronous motor according to the present invention includes

a stator iron core having a plurality of teeth in an inner circumferential portion thereof and a space surrounded by the inner circumferential portion,

an armature winding wound on every two teeth among the plurality of teeth, and

a rotor that is inserted into the space of the stator iron core and has magnetic-field poles that are each composed of a permanent magnet; the permanent-magnet synchronous motor is characterized

in that the armature winding is separated into a first armature winding and a second armature winding that are independent from each other,

in that the first armature winding is connected with a first control apparatus,

in that the second armature winding is connected with a second control apparatus,

in that driving can be performed by a first system including the first armature winding and the first control apparatus and a second system including the second armature winding and the second control apparatus, and

in that if a failure occurs in one of the first system and the second system, the driving by the one thereof is stopped and the driving is continued by the other one thereof.

An electric power steering device according to the present invention is provided with a permanent-magnet synchronous motor that includes

a stator iron core having a plurality of teeth in an inner circumferential portion thereof and a space surrounded by the inner circumferential portion,

an armature winding wound on every two teeth among the plurality of teeth, and

a rotor that is inserted into the space of the stator iron core and has magnetic-field poles that are each composed of a permanent magnet; the permanent-magnet synchronous motor is characterized

in that the armature winding is separated into a first armature winding and a second armature winding that are independent from each other,

in that the first armature winding is connected with a first control apparatus,

in that the second armature winding is connected with a second control apparatus,

in that driving can be performed by a first system including the first armature winding and the first control apparatus and a second system including the second armature winding and the second control apparatus, and

in that if a failure occurs in one of the first system and the second system, the driving by the one thereof is stopped and the driving is continued by the other one thereof; in the electric power steering device, torque produced by the permanent-magnet synchronous motor is involved in steering of a vehicle.

Advantage of the Invention

A permanent-magnet synchronous motor according to the present invention includes

a stator iron core having a plurality of teeth in an inner circumferential portion thereof and a space surrounded by the inner circumferential portion,

an armature winding wound on every two teeth among the plurality of teeth, and

a rotor that is inserted into the space of the stator iron core and has magnetic-field poles that are each composed of a permanent magnet; the permanent-magnet synchronous motor is characterized

in that the armature winding is separated into a first armature winding and a second armature winding that are independent from each other,

in that the first armature winding is connected with a first control apparatus,

in that the second armature winding is connected with a second control apparatus,

in that driving can be performed by a first system including the first armature winding and the first control apparatus and a second system including the second armature winding and the second control apparatus, and

in that if a failure occurs in one of the first system and the second system, the driving by the one thereof is stopped and the driving is continued by the other one thereof. As a result, there can be obtained a permanent-magnet synchronous motor in which even if a failure occurs in one of the two systems, desired torque can be obtained by the other one thereof.

An electric power steering device according to the present invention is provided with a permanent-magnet synchronous motor that includes

a stator iron core having a plurality of teeth in an inner circumferential portion thereof and a space surrounded by the inner circumferential portion,

an armature winding wound on every two teeth among the plurality of teeth, and

a rotor that is inserted into the space of the stator iron core and has magnetic-field poles that are each composed of a permanent magnet; the permanent-magnet synchronous motor is characterized

in that the armature winding is separated into a first armature winding and a second armature winding that are independent from each other,

in that the first armature winding is connected with a first control apparatus,

in that the second armature winding is connected with a second control apparatus,

in that driving can be performed by a first system including the first armature winding and the first control apparatus and a second system including the second armature winding and the second control apparatus, and

in that if a failure occurs in one of the first system and the second system, the driving by the one thereof is stopped and the driving is continued by the other one thereof. In the electric power steering device, torque produced by the permanent-magnet synchronous motor is involved in steering of a vehicle; therefore, there can be obtained an electric power steering device in which even if a failure occurs in one of the two systems, desired torque can be obtained by the other one thereof and hence steering of a vehicle can smoothly be continued.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is a configuration diagram of an electric power steering device according to Embodiment 1 of the present invention. InFIG. 1, when a driver operates a steering wheel (unillustrated), steering power produced through steering by the driver is transferred to a shaft105of an electric power steering device101through the intermediary of a steering shaft (unillustrated). The steering torque transferred to the shaft105is detected and transformed into an electric signal by a torque sensor106; then, through a cable107, the electric signal is inputted to a control apparatus3by way of a torque sensor signal connector13of a driving-apparatus-integrated permanent-magnet synchronous motor1. In the driving-apparatus-integrated permanent-magnet synchronous motor1, a motor unit2, the control apparatus3provided with a driving apparatus and the like in such a manner as described later, and a gearbox102with a built-in speed reducing mechanism are integrally fixed with one another. The details of the driving-apparatus-integrated permanent-magnet synchronous motor1will be explained later.

Information items such as a vehicle speed and the like in a vehicle network (unillustrated) are inputted to the control apparatus3by way of a vehicle signal connector12; furthermore, electric power from a vehicle power source (unillustrated) such as a battery is inputted to the control apparatus3by way of a power source connecter11. Based on the inputted driver's steering torque and information items such as a vehicle speed, the control apparatus3in the driving-apparatus-integrated permanent-magnet synchronous motor1calculates torque to be outputted by the motor unit2; then, by way of the driving apparatus, including an after-mentioned inverter, that is provided in the control apparatus3, the control apparatus3supplies an electric current to an armature winding of the motor unit2.

The rotation shaft, as the output axle, of the driving-apparatus-integrated permanent-magnet synchronous motor1is mounted in such a way that the axial direction thereof is in parallel with the axial direction of a housing103of the electric power steering device101. Output torque of the driving-apparatus-integrated permanent-magnet synchronous motor1is decelerated through the intermediary of the gearbox102incorporating a belt and a ball screw and is transformed into thrust for making a rack axel in the housing103perform a translational motion; then, the thrust assists the driver's steering power inputted to the electric power steering device101by way of the shaft105. The thrust produced by the translational motion of the rack axel makes a tie rod104travel in the axial direction thereof, so that the front wheels (unillustrated), which are the steering wheels of the vehicle, are steered.

The electric power steering device101makes it possible that with small steering power, the driver obtains large steering power for steering the front wheels on which the weight of the vehicle itself is imposed; thus, the vehicle can smoothly be turned from side to side.

In the case where an obstacle detected by a vehicle camera, a vehicle radar, or the like is avoided and in the case where a traveling lane is maintained or changed, the electric power steering device101in an automatic driving vehicle operates as an actuator; regardless of the driver's steering of the steering wheel, the driving-apparatus-integrated permanent-magnet synchronous motor1outputs torque required for steering the vehicle.

As described above, in an electric power steering device configured in such away as to produce auxiliary torque for assisting steering operation by a driver and steering torque at a time when automatic driving is implemented, it is important that neither the auxiliary torque for assisting steering operation by the driver while the vehicle is driven nor the steering torque at a time when automatic driving is implemented is lost.

Therefore, in the driving-apparatus-integrated permanent-magnet synchronous motor1that outputs torque and transfers the torque to the electric power steering device101, it is required, in order to prevent the torque from being suddenly lost upon a failure, that two independent systems give redundancy to a driving apparatus including an inverter, a control circuit for controlling the driving apparatus, and a permanent-magnet synchronous motor, that a failed system is excluded from control and drive of the permanent-magnet synchronous motor, and that a normal system performs driving in such a way that the permanent-magnet synchronous motor is made to continuously output desired torque. When electrically independent from each other, the respective control apparatuses in the two systems are prevented from being affected by a failure in one of the two systems and the respective driving apparatuses in the two systems are prevented from being affected by a failure in one of the two systems; however, it is required that the respective permanent-magnet synchronous motors in the two systems are magnetically as well as electrically separated from each other.

The following is the reason why it is required that in order to make the permanent-magnet synchronous motor in the normal system continuously output torque, the two systems are magnetically as well as electrically separated from each other: in the case where when the two systems are not magnetically separated from each other, the mutual inductance, which is magnetic coupling between the two systems in the permanent-magnet synchronous motor, is large, interlinked magnetic flux generated through rotation of the permanent magnet makes a large current flow through a low-impedance short circuit in the armature winding of one of the two systems even if supply of an electric current to the failed one of the two systems is stopped; the foregoing large current functions as a primary current and the mutual inductance makes a secondary current flow in the armature winding of the other (normal) system; thus, the current in the other (normal) system, which is required for making the permanent-magnet synchronous motor continuously produce torque, is disturbed.

Therefore, in order to securely output torque to be continuously outputted upon a failure, it is required that two systems that are magnetically coupled with each other in a weak manner, i.e., two systems with a small mutual inductance, give redundancy to the permanent-magnet synchronous motor.

As a configuration for obtaining a permanent-magnet synchronous motor in which the magnetic coupling between the two systems is small, a structure is conceivable in which two iron cores corresponding to the respective systems, i.e., two stators, are provided in a single driving-apparatus-integrated permanent-magnet synchronous motor; however, in this case, the permanent-magnet synchronous motor is large-size and heavy and hence the mountability to an electric power steering device and the gasoline mileage of an automobile are deteriorated; thus, it goes without saying that the foregoing permanent-magnet synchronous motor is inappropriate for being mounted in a vehicle.

FIG. 2is a block diagram of a permanent-magnet synchronous motor according to Embodiment 1 of the present invention; the permanent-magnet synchronous motor corresponds to the driving-apparatus-integrated permanent-magnet synchronous motor1in the electric power steering device101illustrated inFIG. 1. InFIG. 2, a stator4in the motor unit2of the driving-apparatus-integrated permanent-magnet synchronous motor1is provided with a stator iron core5configured with magnetic thin plates that are stacked in the axial direction. Twelve teeth6, as a plurality of teeth, are formed in the inner circumferential portion of the stator iron core5in such a way as to be spaced 30° (as a predetermined angle) apart from one another.

An armature winding7is wound alternately on the twelve teeth in a concentrated winding manner. The armature winding7is configured with two sets of armature windings, i.e., a first armature winding71and a second armature winding72, that are independent from each other and are each in a three-phase delta connection or in a three-phase star connection.

The first armature winding71includes a first U-phase armature winding71U, a first V-phase armature winding71V, and a first W-phase armature winding71W; the first U-phase armature winding71U, the first V-phase armature winding71V, and the first W-phase armature winding71W are each wound on every four teeth6.

The second armature winding72includes a second U-phase armature winding72U, a second V-phase armature winding72V, and a second W-phase armature winding72W; the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W are each wound on every four teeth6.

The first U-phase armature winding71U and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of a tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of a tooth62, that flank the tooth62on which no winding is wound; the first W-phase armature winding71W and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of a tooth63, that flank the tooth63on which no winding is wound.

The first wiring lead71and the second wiring lead72are alternately wound on every two teeth. Because in such a manner as described above, the first wiring lead71and the second wiring lead72are alternately wound on every two teeth, the magnetic coupling between the first wiring lead71and the second wiring lead72is small and hence the mutual inductance is small; therefore, even if a short-circuit accident occurs in one of the two armature windings and hence a short circuit current flows therein, no adverse effect is provided to the armature current flowing in the other one of the two armature windings.

The control apparatus3in the driving-apparatus-integrated permanent-magnet synchronous motor1is provided with a first microcomputer14a, a first inverter15a, a first filter coil18a, a first power source relay19a, a first torque sensor signal interface20a, a first vehicle signal interface21a, and a first driving circuit22a. The first inverter15ais composed of, for example, a three-phase bridge circuit (unillustrated) provided with a U-phase upper arm and a U-phase lower arm that each have a semiconductor switching device, a V-phase upper arm and a V-phase lower arm that each have a semiconductor switching device, and a W-phase upper arm and a W-phase lower arm that each have a semiconductor switching device.

Through a first power source connecter11aconnected with an electric power source that outputs DC electric power based on the output of a vehicle battery or the like composed of, for example, a secondary battery, DC electric power is supplied to the first inverter15aby way of the first filter coil18aand the first power source relay19a. Through a first torque sensor signal connector13a, a first steering torque signal produced by a driver of the vehicle is inputted to the first microcomputer14aby way of the first torque sensor signal interface20a; in addition, through a first vehicle signal connector12a, a first vehicle signal such as a vehicle speed is inputted to the first microcomputer14aby way of the first vehicle signal interface21a. Furthermore, a first inverter output current signal corresponding to the output current of the first inverter15a, detected by a first current sensor23a, is inputted to the first microcomputer14a.

Based on the inputted foregoing first steering torque signal, first vehicle signal such as a vehicle speed, first inverter output current signal, and the like, the first microcomputer14acalculates a target output current value for the first inverter15aand then provides a first command signal based on the result of the calculation to the first driving circuit22a. Based on the first command signal provided by the first microcomputer14a, the first driving circuit22aperforms PWM (Pulse Width Modulation)-control of each of the semiconductor switching devices in the first inverter15aso that the first inverter15aoutputs a three-phase output current that is feedback-controlled so as to keep track of the output target current value.

The three-phase output current from the first inverter15ais supplied to the first U-phase armature winding71U, the first V-phase armature winding71V, and the first W-phase armature winding71W that are included in the first armature winding of the motor unit2, so that a first rotating magnetic field is generated in the stator4. Based on the rotation of the first rotating magnetic field, driving power is provided to the rotor provided with a permanent magnet, as magnetic-field poles, so that the rotor rotates.

The first inverter15aforms a first driving apparatus; the first microcomputer14a, the first filter coil18a, the first power source relay19a, the first torque sensor signal interface20a, the first vehicle signal interface21a, and the first driving circuit22aform a first control apparatus.

Furthermore, the foregoing first microcomputer14a, first inverter15a, filter coil18a, first power source relay19a, first torque sensor signal interface20a, first vehicle signal interface21a, and first driving circuit22aand the foregoing first armature winding including the first U-phase armature winding71U, the first V-phase armature winding71V, and the first W-phase armature winding71W form a first system of the permanent-magnet synchronous motor1.

The control apparatus3in the driving-apparatus-integrated permanent-magnet synchronous motor1is provided with a second microcomputer14b, a second inverter15b, a second filter coil18b, a second power source relay19b, a second torque sensor signal interface20b, a second vehicle signal interface21b, and a second driving circuit22b. The second inverter15bis composed of, for example, a second three-phase bridge circuit (unillustrated) provided with a U-phase upper arm and a U-phase lower arm that each have a semiconductor switching device, a V-phase upper arm and a V-phase lower arm that each have a semiconductor switching device, and a W-phase upper arm and a W-phase lower arm that each have a semiconductor switching device.

Through a second power source connecter lib connected with an electric power source that outputs DC electric power based on the output of a vehicle battery or the like composed of, for example, a secondary battery, DC electric power is supplied to the second inverter15bby way of the second filter coil18band the second power source relay19b. Through a second torque sensor signal connector13b, a second steering torque signal produced by a driver of the vehicle is inputted to the second microcomputer14bby way of the second torque sensor signal interface20b; in addition, through a second vehicle signal connector12b, a second vehicle signal such as a vehicle speed is inputted to the second microcomputer14bby way of the second vehicle signal interface21b. Furthermore, a second inverter output current signal corresponding to the output current of the second inverter15b, detected by a second current sensor23b, is inputted to the second microcomputer14b.

Based on the inputted foregoing second steering torque signal, second vehicle signal such as a vehicle speed, second inverter output current signal, and the like, the second microcomputer14bcalculates a target output current value for the second inverter15band then provides a second command signal based on the result of the calculation to the second driving circuit22b. Based on the second command signal provided by the second microcomputer14b, the second driving circuit22bperforms PWM-control of each of the semiconductor switching devices in the second inverter15bso that the second inverter15boutputs a three-phase output current that is feedback-controlled so as to keep track of the output target current value.

The three-phase output current from the second inverter15bis supplied to the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W that are included in the second armature winding of the motor unit2, so that a second rotating magnetic field is generated in the stator4. Based on the rotation of the second rotating magnetic field, driving power is provided to the rotor provided with a permanent magnet, as magnetic-field poles, so that the rotor rotates.

The second inverter15bforms a second driving apparatus; the second microcomputer14b, the second filter coil18b, the second power source relay19b, the second torque sensor signal interface20b, the second vehicle signal interface21b, and the second driving circuit22bform a second control apparatus.

The foregoing second microcomputer14b, second inverter15b, second filter coil18b, second power source relay19b, second torque sensor signal interface20b, second vehicle signal interface21b, and second driving circuit22band the foregoing second armature winding including the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W form a second system of the permanent-magnet synchronous motor1.

It may be allowed that the first control apparatus and the second control apparatus are configured in such a way that at a normal time when no failure has occurred, the distribution rates of respective amounts of electric currents to be supplied to the first armature winding71and the foregoing second armature winding72are not equal to each other.

The foregoing first system and second system are each configured in such a way as to collaborate with other vehicle systems for brake control, chassis control, and the like through a vehicle signal so as to control the motor unit2of the permanent-magnet synchronous motor1; in addition, by means of a communication apparatus17, the first system and the second system are synchronize with each other through a synchronization signal so as to control the motor unit2.

In this situation, the operation of the driving-apparatus-integrated permanent-magnet synchronous motor1at a time when a failure occurs will be explained. For example, as an example, there will be explained the case where a failure such as a short circuit occurs in any one of the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W that are included in the second armature winding of the second system of the driving-apparatus-integrated permanent-magnet synchronous motor1.

If a failure such as a short circuit occurs in the second armature winding72, the second microcomputer14bin the second system detects the failure in the second armature winding72and then provides a command to the second driving circuit22bso as to stop driving of the second inverter15b, thereby making the three-phase armature current, as a driving current for the second armature winding72, become “0”. This makes the torque that has been produced in the motor unit2by the second system become “0” and hence the output torque of the overall motor becomes the torque produced only the first system, i.e., becomes half of the torque at a normal time; however, the function of the electric power steering device is not lost completely and the steering can continuously be performed.

Furthermore, the first U-phase armature winding71U and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of the tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of the tooth62, that flank the tooth62on which no winding is wound; the first W-phase armature winding71W and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of the tooth63, that flank the tooth63on which no winding is wound; therefore, the magnetic coupling between the first armature winding71and the second armature winding72is small and hence the mutual inductance becomes small. As a result, even if a short-circuit accident occurs in one of the two armature windings and hence a short circuit current flows therein, no adverse effect is provided to the armature current flowing in the other one of the two armature windings.

When there is performed the control in which driving of the permanent-magnet synchronous motor by the second system is stopped and, at the same time, the driving current produced by the first system is increased so as to be twice as large as the driving current at a normal time, the torque produced by the first system is also doubled; thus, it is also made possible that the extinction of the torque that has been produced by the second system is compensated so that the output torque of the overall motor does not change from the torque at a normal time.

It may be allowed that if one of the two systems fails, the other one thereof performs the foregoing driving with the amount of an electric current that exceeds the maximum current at a normal time when no failure has occurred in the one of the two systems.

Furthermore, in the driving-apparatus-integrated permanent-magnet synchronous motor1according to Embodiment 1 of the present invention, as described above, the first U-phase armature winding71U and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of a tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of the tooth62, that flank the tooth62on which no winding is wound; the first W-phase armature winding71W and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of a tooth63, that flank the tooth63on which no winding is wound. In other words, the first armature winding71in the first system and the second armature winding72in the second system are alternately wound on the teeth6.

Accordingly, for example, when due to a failure in the second system, the driving current to be produced by the second system is made to be “0”, the heat generated in the stator4is decentralized on every four teeth of the first system; therefore, because the temperature of the motor unit2does not locally rise, there can be prolonged the time in which after the failure, the electric power steering device can continuously output auxiliary torque, so that the drivers' operation of the steering wheel can be lightened.

Because the electric power steering device, according to Embodiment 1, that is configured in such a manner as described above can maintain its function even if the driving-apparatus-integrated permanent-magnet synchronous motor fails, the safety of the vehicle can be raised.

FIG. 3is a block diagram of a permanent-magnet synchronous motor according to Embodiment 2 of the present invention; the permanent-magnet synchronous motor is utilized as the driving-apparatus-integrated permanent-magnet synchronous motor1in the electric power steering device101illustrated inFIG. 1. The different point between Embodiments 1 and 2 is that at a normal time, the first microcomputer14aand the second microcomputer14bof the control apparatus3are not synchronized with each other through a synchronization signal so as to control the motor unit2. The other configurations are the same as those in Embodiment 1.

As described above, the first U-phase armature winding71U and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of the tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of the tooth62, that flank the tooth62on which no winding is wound; the first W-phase armature winding71W and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of the tooth63, that flank the tooth63on which no winding is wound; therefore, the magnetic coupling between the first armature winding71and the second armature winding72is small and hence the mutual inductance becomes small.

Accordingly, while the respective driving currents do not affect each other, each of the first microcomputer14ain the first control apparatus and the second microcomputer14bin the second control apparatus obtains a signal from an angle detection apparatus (unillustrated) for detecting the rotation position of the motor unit2, so that a single common rotor (unillustrated) can independently be driven.

FIG. 4is an explanatory diagram of the permanent-magnet synchronous motor according to Embodiment 2 of the present invention;FIG. 4is an explanatory diagram for explaining the operation and the effect at a time when a failure occurs. InFIG. 4, for the convenience of explanation, the driving-apparatus-integrated permanent-magnet synchronous motor is illustrated in such a way as to be schematically separated into a driving-apparatus-integrated permanent-magnet synchronous motor1ato be controlled by the first system and a driving-apparatus-integrated permanent-magnet synchronous motor1bto be controlled by the second system; the driving-apparatus-integrated permanent-magnet synchronous motor1ahas a motor unit2aand a control apparatus3a; the driving-apparatus-integrated permanent-magnet synchronous motor1bhas a motor unit2band a control apparatus3b. For example, as represented inFIG. 4, if a short-circuit accident occurs between the second U-phase armature winding72U and the second V-phase armature winding72V that are included in the armature winding71of the second system, a short circuit current flows in the second U-phase armature winding72U and the second V-phase armature winding72V; then, magnetic flux Φ based on the short circuit current flows therein. However, the magnetic flux Φ does not substantially pass through the respective teeth on which the first U-phase armature winding71U, the first V-phase armature winding71V, and the second W-phase armature winding72W.

Therefore, even if an accident such as a short circuit occurs in the second armature winding72of the second system, no adverse effect is substantially provided to the control of the first armature winding71of the normal first system. Similarly, even if an accident such as a short circuit occurs in the first armature winding71of the first system, no adverse effect is substantially provided to the control of the second armature winding72of the normal second system.

Furthermore, in the driving-apparatus-integrated permanent-magnet synchronous motor according to Embodiment 2 of the present invention, the first microcomputer14aand the second microcomputer14bof the control apparatus3are not synchronized with each other through a synchronization signal so as to control the motor unit2; thus, although the stator iron core5is common to the first system and the second system, setting the driving current of the failed second system to “0” makes it possible that there is performed operation similar to the operation in which as if two driving-apparatus-integrated permanent-magnet synchronous motors existed, one of the two permanent-magnet synchronous motors fails and the remaining normal driving-apparatus-integrated permanent-magnet synchronous motor outputs torque to the electric power steering device.

As described above, the driving-apparatus-integrated permanent-magnet synchronous motor according to Embodiment 2 of the present invention makes it possible that a single driving-apparatus-integrated permanent-magnet synchronous motor gives redundancy to an electric power steering device, on the mountability and the weight of which restriction is placed; this is a large advantage that does not exist in a conventional driving-apparatus-integrated permanent-magnet synchronous motor.

In addition, for example, when a vehicle is started from a parking state, the vehicle speed is low and the driver largely operates the steering wheel; therefore, the electric power steering device also outputs large auxiliary torque. In this situation, when the steering wheel is turned to the left end or the right end, there occurs a locking state where the current value in the three-phase armature winding of the motor unit is fixed and the heat generation amount in the phase where the current flows most becomes large; thus, in order to suppress the heat generation, it is required to reduce the current amount in the armature winding.

However, in the driving-apparatus-integrated permanent-magnet synchronous motor according to Embodiment 2 of the present invention, when there exists a temperature-rise difference between the respective motor units or the respective control apparatuses of the first system and the second system, the current amount of the system having a higher temperature is decreased and, in contrast, the current amount of the other system is increased, so that it is made possible to perform steering without reducing the auxiliary torque. As described above, the reason why the respective current amounts of the first and second systems can separately be controlled is that the mutual inductance between the first and second systems is small and hence the respective systems can independently be controlled; the effect is large.

In the driving-apparatus-integrated permanent-magnet synchronous motor according to Embodiment 2 of the present invention, as is the case with Embodiment 1, the first U-phase armature winding71U and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of the tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of the tooth62, that flank the tooth62on which no winding is wound; the first W-phase armature winding71W and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of the tooth63, that flank the tooth63on which no winding is wound. In other words, the first armature winding in the first system and the second armature winding in the second system are alternately wound on the teeth6.

Accordingly, for example, when due to a failure in the second system, the driving current to be produced by the second system is made to be “0”, the heat generated in the stator4is decentralized on every four teeth of the first system; therefore, because the temperature of the motor unit2does not locally rise, there can be prolonged the time in which after the failure, the electric power steering device can continuously output auxiliary torque, so that the drivers' operation of the steering wheel can be lightened.

FIG. 5is a block diagram of a permanent-magnet synchronous motor according to Embodiment 3 of the present invention; the permanent-magnet synchronous motor is utilized as the driving-apparatus-integrated permanent-magnet synchronous motor1in the electric power steering device101illustrated inFIG. 1. InFIG. 5, the first U-phase armature winding71U and the first V-phase armature winding71V are wound on the respective teeth, at the both sides of the tooth61, that flank the tooth61on which no winding is wound; the first V-phase armature winding71V and the first W-phase armature winding71W are wound on the respective teeth, at the both sides of the tooth64, that flank the tooth64on which no winding is wound; the first W-phase armature winding71W and the second U-phase armature winding72U are wound on the respective teeth, at the both sides of the tooth62, that flank the tooth62on which no winding is wound.

Furthermore, the second U-phase armature winding72U and the second V-phase armature winding72V are wound on the respective teeth, at the both sides of the tooth65, that flank the tooth65on which no winding is wound; the second V-phase armature winding72V and the second W-phase armature winding72W are wound on the respective teeth, at the both sides of the tooth63, that flank the tooth63on which no winding is wound; the second W-phase armature winding72W and the first U-phase armature winding71U are wound on the respective teeth, at the both sides of a tooth66, that flank the tooth66on which no winding is wound.

In other words, in the permanent-magnet synchronous motor according to Embodiment 3 of the present invention, the first armature winding71of the first system and the second armature winding72of the second system are arranged in such a way as to be linear-symmetric with each other with respect to a radial-direction straight line Y that passes through the center axis X of the stator4. That is to say, the first U-phase armature winding71U, the first V-phase armature winding71V, and the first W-phase armature winding71W that are included in the first armature winding71are arranged in one of the semicircles that are separated by the straight line Y at the cross section, of the stator4, that is perpendicular to the axial line; the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W that are included in the second armature winding72are arranged in the other one of the semicircles that are separated by the straight line Y at the cross section, of the stator4, that is perpendicular to the axial line. The other configurations are the same as those in Embodiment 1.

In the permanent-magnet synchronous motor, according to Embodiment 3, that is configured in such a manner as described above, in the case where for example, a temperature rise in the first system is large, the driving current for the first system is decreased and the driving current for the second system is increased, so that the temperature distribution in the motor unit2is readily equalized; as a result, it is made possible to prolong the time during which at a normal time, the electric power steering device can continuously output auxiliary torque; thus, the drivers' operation of the steering wheel can be lightened.

Moreover, the first armature winding71and the second armature winding72are separated in half in such a way as to be linear-symmetric with each other with respect to the stator4; therefore, connection lines16aof the first system and connection lines16bof the second system are readily arranged without geometric interference. In particular, in the case of a concentrated winding motor, there is demonstrated a characteristic that because for each of the first inverter15aand the second inverter15b, wiring of each of the phases is performed on a single tooth of the corresponding phase, connection becomes simple.

FIG. 6is a schematic development view of a permanent-magnet synchronous motor according to Embodiment 4 of the present invention. InFIG. 6, the stator4is provided with the stator iron core5configured with magnetic thin plates that are stacked in the axial direction, a plurality of teeth6formed in the inner circumferential portion of the stator iron core5, and an armature winding7wound on every two teeth6in a concentrated manner. The arrangement of the armature winding7in Embodiment 4 is the same as that in foregoing Embodiment 3.

That is to say, the armature winding7includes the first armature winding71and the second armature winding72; the first armature winding71includes the first U-phase armature winding71U, the first V-phase armature winding71V, and the first W-phase armature winding71W that are wound in a concentrated manner on three respective teeth6that are arranged in an every-other-tooth manner. The second armature winding72includes the second U-phase armature winding72U, the second V-phase armature winding72V, and the second W-phase armature winding72W that are wound in a concentrated manner on three respective teeth6that are arranged in an every-other-tooth manner. As is the case with foregoing Embodiment 3 inFIG. 5, the first armature winding is disposed in one of the two semicircle portions of the stator4, and the second armature winding is disposed in the other one of the two semicircle portions of the stator4.

FIG. 7is a schematic development view of a permanent-magnet synchronous motor as a comparative example;FIG. 7illustrates the case where in the stator4, the armature winding7is wound on every teeth6of the stator iron core5. The reason why in the permanent-magnet synchronous motor, illustrated inFIG. 6, according to Embodiment 4 of the present invention, the axial-direction height of each of winding end portions7c, of the armature winding7, that protrude in the axial direction from both the respective axial-direction end portions of the stator iron core5is relatively larger than the axial-direction height of the winding end portion7cof the permanent-magnet synchronous motor, as the comparative example, illustrated inFIG. 7is that in order to make the magnetomotive force in the stator4equal to the magnetomotive force in a conventional stator, the number of turns is increased.

InFIG. 6, in the permanent-magnet synchronous motor according to Embodiment 4 of the present invention, the armature winding7is wound on every two teeth6; therefore, respective spaces A and B are formed at both axial-direction sides of the teeth6on which no armature winding7is wound. The control apparatus3is fixed to one of the axial-direction ends of the stator4, in which the space A is provided; a metal case8of the motor is fixed to the other one of the axial-direction ends of the stator4, in which the space B is provided.

The control apparatus3is provided with an aluminum-made heat sink9that releases heat generated at least in the inverter, an insulated case10, the first power source connecter11ahaving a resin-made case in the first system, the second power source connecter11bhaving a resin-made case in the second system, the first vehicle signal connector12ahaving a case in the first system, the second vehicle signal connector12bhaving a resin-made case in the second system, the first torque sensor signal connector13ahaving a resin-made case in the first system, and the second torque sensor signal connector13bhaving a resin-made case in the second system.

The foregoing first power source connecter11a, second power source connecter11b, first vehicle signal connector12a, second vehicle signal connector12b, first torque sensor signal connector13a, and second torque sensor signal connector13bare each fixed to the axial-direction end face of the insulated case10.

The heat sink9is fixed to the stator4in such a way as to substantially seal the one of the axial-direction ends of the stator4; the case8of the motor is fixed to the stator4in such a way as to substantially seal the other one of the axial-direction ends of the stator4. The gearbox102of the electric power steering device101illustrated inFIG. 1is mounted on the case8of the motor.

FIG. 8is a schematic development view of the permanent-magnet synchronous motor according to Embodiment 4 of the present invention;FIG. 8more specifically illustrates the permanent-magnet synchronous motor according to Embodiment 4 of the present invention. InFIG. 8, a protruding portion91that abuts on the axial-direction endface of a tooth on which no armature winding is wound is provided in the inner endface of the heat sink9. A tooth on which no armature winding is wound has an iron core51that is extended in the axial direction of the stator iron core and then abuts on the inner endface of the heat sink9. One of the winding end portions7cof the armature winding7is disposed in a space formed between one of the axial-direction ends of the stator iron core5and the inner endface of the heat sink9. The protruding portion91and the iron core51are parts of the constituent components of the permanent-magnet synchronous motor.

A first terminal30afor connecting the first armature winding in the armature winding7with the first inverter15ais disposed in the space A illustrated in foregoingFIG. 6. Although a second terminal for connecting the second armature winding in the armature winding7with the second inverter15bis also disposed in a similar manner, the illustration thereof is omitted. A semiconductor magnetic sensor40in the angle detection apparatus for detecting the rotation angle of the rotor of the permanent-magnet synchronous motor is disposed in the space between the inner endface of the heat sink9and one of the axial-direction ends of a tooth6on which no armature winding is wound. A temperature sensor50for detecting the temperature of the permanent-magnet synchronous motor is provided in such a way as to abut on an insulator surrounding the armature winding7. The first terminal30a, the second terminal, the semiconductor magnetic sensor40, and the temperature sensor50are parts of the constituent components of the permanent-magnet synchronous motor.

The foregoing first terminal30aand second terminal are connected with the first power source connecter11aand the second power source connecter11b, respectively, that are provided in the insulated case10of the control apparatus3, by means of conductors that penetrate respective through-holes provided in the heat sink9. The semiconductor magnetic sensor40and the temperature sensor50are connected with the first microcomputer14a(unillustrated) and the second microcomputer14b(unillustrated), respectively, of the control apparatus3, by means of conductors that penetrate respective through-holes provided in the heat sink9.

In the inner wall surface of the metal-made motor case8fixed to the other axial-direction end of the stator4, a plurality of ribs81for raising the rigidity of the motor case8and a plurality of screw holes82for the connection with the gearbox102of the electric power steering device101are provided in such a way as to correspond to the foregoing spaces B existing at the other axial-direction ends of the respective teeth6on each of which no armature winding is wound. The case8in which the screw holes82are provided is part of the constituent components of the permanent-magnet synchronous motor.

As described above, the permanent-magnet synchronous motor according to Embodiment 4 of the present invention is configured in the foregoing manner; thus, the constituent components that have been arranged above or below the stator in a conventional permanent-magnet motor can be arranged inside the contour that is in the axial direction of the stator and the same as that of the stator; as a result, the contour size and the axial-direction length of the driving-apparatus-integrated permanent-magnet synchronous motor can be reduced. Therefore, there can be realized a high-mountability driving-apparatus-integrated permanent-magnet synchronous motor that has no significant geometric interference with a vehicle and an electric power steering device.

Moreover, for example, not only the protruding portion91of the aluminum-made heat sink9that releases heat generated in the inverter of the control apparatus but also the iron core51included in the protruding portion of the stator iron core5are arranged in the space A illustrated in foregoingFIG. 6, so that heat generated in the armature winding7and the heat in the heat sink9are readily released to the stator iron core5and hence the time during which the steering operation can continuously be performed can be prolonged.

With regard to the permanent-magnet synchronous motor according to any one of foregoing Embodiments 1 through 4 of the present invention, the case where a three-phase armature winding is provided has been described; however, it may be allowed that a multi-phase armature winding other than a three-phase armature winding is provided. In addition, the case where the stator has twelve teeth has been described; however, the number of teeth is not limited to twelve.

The present invention is not limited to the permanent-magnet synchronous motor and the electric power steering device according to any one of Embodiments 1 through 4; in the scope within the spirits of the present invention, the configurations of Embodiments 1 through 4 can appropriately be combined with one another, can partially be modified, or can partially be omitted.

INDUSTRIAL APPLICABILITY

A permanent-magnet synchronous motor and an electric power steering device according to the present invention can be utilized at least in the field of a vehicle such as an automobile.

DESCRIPTION OF REFERENCE NUMERALS

1,1a,1b: driving-apparatus-integrated permanent-magnet synchronous motor2,2a,2b: motor unit3,3a,3b: control apparatus4: stator5: stator iron core51: iron core included in protruding portion6,61,62,63,64: tooth (teeth)7: armature winding71U: first U-phase armature winding71V: first V-phase armature winding71W: first W-phase armature winding72U: second U-phase armature winding72V: second V-phase armature winding72W: second W-phase armature winding8: case81: rib82: screw hole9: heat sink91: protruding portion10: insulated case11,11a,11b: power source connecter12: vehicle signal connector12a: first vehicle signal connector12b: second vehicle signal connector13: torque sensor signal connector13a: first torque sensor signal connector13b: second vehicle signal connector14a: first microcomputer14b: second microcomputer15a: first inverter15b: second inverter16a: connection of first system16b: connection of second system17: communication apparatus18a: first filter coil18b: second filter coil19a: first power source relay19b: second power source relay20a: first torque sensor signal interface20b: second torque sensor signal interface21a: first vehicle signal interface21b: second vehicle signal interface22a: first driving circuit22b: second driving circuit23a: first current sensor23b: second current sensor101: electric power steering device102: gearbox103: housing104: tie rod105: shaft106: torque sensor107: cable