JPH1159440A - Electrically driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically driven power steering device with which operability of a steering wheel is improved during returning operation. SOLUTION: This electrically driven power steering device has a torque control means 40 which enables torque transmission between a frictional plate 20 and a drive rotor 16 during operating a steering wheel, by controlling current supplied to a clutch coil 15. During return of the steering wheel, torque transmission is interrupted between the drive rotor 16 and the frictional plate 20 by the same torque control means 40. The steering wheel is smoothly returned to an original position without being influenced by load of a loss torque of an electric motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for generating a steering assist torque by an electric motor.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view of a main part of a conventional electric power steering apparatus. An electric motor 1 has an electromagnetic clutch 2 connected thereto. The electric motor 1 is rotatably supported by bearings 6 while passing through the yoke 3, a plurality of magnets 4 fixed in the yoke 3 at circumferential intervals in the circumferential direction, and bearings 6. An output shaft 5, a core 7 fixed to the output shaft 5, a conductor wound around the core 7, an armature coil 8 constituting an armature 21 with the core 7, and a rectifier fixed to the output shaft 5. Element 9 and a spring 1 on the surface of the commutator 9.
And a brush 10 contacted by a single elastic force.

An electromagnetic clutch 2 is connected to a yoke 3 by a screw 12.
, A clutch stator 14 fixed to the bracket 13, a clutch coil 15 provided inside the clutch stator 14, a drive rotor 16 fixed to an end of the output shaft 5, A boss 18 provided at an end of the output shaft 5 via a bearing 17;
A transmission plate 19 having an inner end fixed to the boss 18 and formed of a spring, and a drive rotor 1 attached to an outer end of the transmission plate 19.
6 and a friction plate 20 fixed to face the outer periphery.

Next, the operation will be described. When the engine is started, the clutch coil 15 is energized, and a magnetic circuit is constituted by the clutch stator 14, the drive rotor 16, the boss 18, the transmission plate 19 and the friction plate 20 which are magnetic materials. By the action of this magnetic circuit, the friction plate 20 is attracted to the drive rotor 16 against the elastic force of the transmission plate 19, and the boss 18 and the drive rotor 16 are integrated via the transmission plate 19 and the friction plate 20, The torque of the armature 21 is output shaft 5, drive rotor 16, friction plate 20, transmission plate 19
Through the boss 18.

[0005] In this state, when the driver tries to rotate the steering wheel to the right, for example, to rotate the car to the right, the driver moves between the steering wheel and the steering assist torque transmission mechanism (not shown). A provided torque sensor (not shown) detects the rotation direction and rotation angle of the handle and the torque value of the handle, and based on a signal from the torque sensor, the armature coil 8 is energized and the armature 21 rotates. .
The magnitude of the torque of the armature 21 is determined by the value of the current flowing through the armature coil 8, and the rotation direction of the armature 21 is determined by the direction of the current flowing through the armature coil 8. This torque is applied to the output shaft 5, drive rotor 16, friction plate 2
0, transmitted to the boss 18 via the transmission plate 19,
The driven shaft (not shown), which is a part of the steering assist torque transmitting mechanism directly connected to the motor, rotates.

[0006] In the return operation of the handle, the armature coil 8
Is turned off, and the steering wheel is returned to its original position by the driver operating the steering wheel.

In the electromagnetic clutch 2 having the above-described structure, the clutch coil 15 is energized when the engine is started, and the boss 18 and the drive rotor 16 are connected via the transmission plate 19 and the friction plate 20 at a value not less than the maximum torque value of the armature 21. Connected. If the motor 1 breaks down, the steering wheel connected via the steering assist torque transmitting mechanism may not be able to be operated. At that time, the current to the clutch coil 15 is cut off, and the friction is reduced. The force for sucking the plate 20 toward the drive rotor 16 disappears. As a result, the friction plate 20 is separated from the drive rotor 16 by the elastic force of the transmission plate 19, and the steering operation is performed without receiving the load of the armature 21.

[0008]

In the electric power steering apparatus having the above-mentioned structure, when the steering wheel is rotated and then it is attempted to return to the original position, the power supply to the armature coil 8 is cut off. Although the child 21 does not rotate, the friction plate 20 is always attracted and fixed to the drive rotor 16 as long as the engine is driven, except for the failure of the electric motor 1. Therefore, when the handle is to be returned to the original position, the attraction force acting between the magnet 4 and the armature 21, that is, the so-called loss torque of the electric motor 1 becomes a resistance of the handle operation, and the handle is not smoothly returned to the original position. There was a point. In particular, as the size of the vehicle increases, a larger steering assist torque is required. As a result, the motor 1 increases in size, the loss torque of the motor 1 also increases, and the steering wheel operability when trying to return the steering wheel to its original state is poor. There is a problem that it is difficult to mount the electric power steering device having the above configuration on a vehicle.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to provide an electric power steering device with improved handleability when trying to return the handle to its original position. It is the purpose.

[0010]

Means for Solving the Problems Claim 1 according to the present invention.
The described electric power steering device controls the current flowing through the clutch coil to enable the transmission of torque between the friction plate and the drive rotor during steering operation,
Further, a torque control means is provided for interrupting the transmission of torque between the drive rotor and the friction plate when the handle is returned.

Further, in the electric power steering apparatus according to the second aspect, the transmission plate is constituted by a spring, and when the handle is returned, the friction plate is brought into sliding contact with the drive rotor by the elastic force of the transmission plate. It is.

Further, in the electric power steering apparatus according to the third aspect, when the steering wheel is returned, the friction plate is brought into sliding contact with the drive rotor by an electromagnetic force generated by a current flowing through the clutch coil.

Further, in the electric power steering apparatus according to the present invention, a permanent magnet is provided on an outer peripheral portion of the clutch stator, and when the handle is returned, the friction plate slides on the drive rotor by the magnetic force of the permanent magnet. It is something that has become.

In the electric power steering apparatus according to the present invention, the permanent magnets are provided at equal intervals in the circumferential direction of the clutch stator.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an electric power steering apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a main part of an electric power steering apparatus according to Embodiment 1 of the present invention, and an electric motor 1 has an electromagnetic clutch 30 connected thereto. The electric motor 1 includes a yoke 3 and a plurality of magnets 4 fixed within the yoke 3 at equal intervals.
An output shaft 5 penetrating through the yoke 3 and rotatably supported by a bearing 6, a core 7 fixed to the output shaft 5, and a conductor wound around the core 7 and an armature together with the core 7. 21, a commutator 9 fixed to the output shaft 5, and a spring 1 on the surface of the commutator 9.
And a brush 10 contacted by a single elastic force.

The electromagnetic clutch 30 includes a bracket 13 fixed to the yoke 3 by screws 12,
And a clutch coil 15 provided inside the clutch stator 14,
A drive rotor 16 fixed to the end of the output shaft 5 and a boss 18 provided at the end of the output shaft 5 via a bearing 17
A transmission plate 31 formed of a spring whose inner end is fixed to the boss 18; and an outer end of the transmission plate 31 which is always in contact with the outer peripheral portion of the drive rotor 16 by the elastic force of the transmission plate 31. And a friction plate 20 provided.

The electromagnetic clutch 30 is electrically connected to a torque control means 40 which is operated by a signal from a torque sensor 41 provided between the steering wheel and a steering assist torque transmitting mechanism (not shown). I have. The torque control means 40 controls the current flowing through the torque clutch coil 15 based on a signal (rotation direction, rotation angle, torque value, etc., of the steering wheel) from the torque sensor 41. The transmission of the torque between the drive rotor 16 and the friction plate 20 is interrupted when the handle is returned, and the transmission of the torque between the drive rotor 16 and the friction plate 20 is interrupted.

Next, the operation of the electric power steering device will be described. When the engine is started, the clutch coil 15 is energized (the electromagnetic clutch is turned on), and the clutch stator 14, the drive rotor 16, the boss 1
8, a magnetic circuit is constituted by the transmission plate 31 and the friction plate 20. By the action of the magnetic circuit, the friction plate 20 which has been in contact with the drive rotor 16 in advance by the elastic force of the transmission plate 31 before the start of the engine is firmly connected to the drive rotor 16. The coupling force at that time is a value equal to or greater than the maximum torque of the armature 21, and the torque of the rotor 21 is reliably transmitted to the steering assist torque mechanism through the output shaft 5, the drive rotor 16, the friction plate 20, the transmission plate 31, and the boss 18. Is transmitted.

When the driver turns the steering wheel to the right, for example, to turn the car to the right,
The torque sensor 41 detects the rotation angle, rotation direction, torque and the like of the handle at that time. This detection signal is sent to the torque control means 40, and by the signal from the torque control means 40, the armature coil 8 is energized and the armature 21 rotates. The magnitude of the torque of the armature 21 is determined by the value of the current flowing through the armature coil 8, and the rotation direction of the armature 21 is determined by the direction of the current flowing through the armature coil 8. This torque is transmitted to the boss 18 via the output shaft 5, the drive rotor 16, the friction plate 20, and the transmission plate 31, and is a driven shaft (not shown) which is directly connected to the boss 18 and is a part of a steering assist torque transmission mechanism. Rotates.

Subsequently, when the handle is to be returned to its original state, a restoring force acts on the handle.
The torque of the armature 21 as the steering assist torque is unnecessary, and the energization to the armature coil 8 is cut off. At the same time, the power supply to the clutch coil 15 is also cut off (the electromagnetic clutch OF
F), the force for attracting the friction plate 20 toward the drive rotor 16 disappears. That is, the transmission of torque between the friction plate 20 and the drive rotor 16 is interrupted, and the handle can be returned smoothly without receiving the load of the loss torque of the electric motor 1 when the handle is returned. Also at this time, since the friction plate 20 comes into sliding contact with the drive rotor 16 by the elastic force of the transmission plate 31, the clutch coil 15 is energized again and the friction plate 20
When is firmly coupled to the drive rotor 16, the friction plate 20 does not collide with the drive rotor 16 to generate a collision sound.

Incidentally, should the motor 1 fail,
There is a possibility that the operation of the steering wheel connected via the steering assist torque transmission mechanism may become impossible. At this time, however, the power supply to the clutch coil 15 is interrupted, and the force for attracting the friction plate 20 to the drive rotor 16 side. Disappears. That is, transmission of torque between the friction plate 20 and the drive rotor 16 is interrupted, and the steering wheel is operated without being affected by the electric motor 1.

FIG. 2 is a diagram showing the relationship between the respective operations of the above-described handle, the electromagnetic clutch 30 and the electric motor 1 in comparison with a conventional example. As can be seen from this figure, the OFF operation of the electromagnetic clutch is continued from the completion of the steering wheel return operation until the start of the next steering wheel operation. Therefore, when the vehicle is traveling straight, the steering wheel does not need to be affected by the loss torque of the electric motor 1 in a so-called fine steering state in which the steering wheel is slightly moved.

In the description of the operation of the electric power steering apparatus, the electromagnetic clutch 30 is turned off and the electric motor 1 is turned off at the same time as the operation of returning the steering wheel. May be turned off, or the motor 1 may be turned off, and the torque of the armature 2 of the motor 1 may be used to assist in returning the steering wheel.

Embodiment 2 FIG. FIG. 3 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 2 of the present invention. In this embodiment, permanent magnets 32 are provided on the outer peripheral edge of the clutch stator 14 at equal intervals. The difference from the first embodiment is that the friction plate 20 is always in contact with the drive rotor 16 due to the magnetic force of the magnet 32. In this electric power steering device, when the steering wheel is returned to the original position, the power supply to the clutch coil 15 is cut off, the force for attracting the friction plate 20 to the drive rotor 16 side disappears, and the friction plate 20 Drive rotor 1
Transmission of torque between the steering wheel 6 and the steering wheel 6 is interrupted, and when the steering wheel is returned, the load of the loss torque of the electric motor 1 is not received, and the steering wheel can be smoothly returned to the original position. Also,
Even at this time, the magnetic force of the permanent magnet 21 causes the friction plate 20
Is in contact with the drive rotor 16, the clutch coil 15 is again energized thereafter, and when the friction plate 20 is firmly coupled to the drive rotor 16, the friction plate 20 collides with the drive rotor 16 and the collision noise Does not occur.

When the handle is to be returned to the original position, the current to the clutch coil 15 is not completely cut off, but a small current that the friction plate 20 slides on the drive rotor 16 is applied to the clutch. You may make it flow through the coil 15.

[0026]

As described above, according to the electric power steering apparatus of the first aspect of the present invention, the electric current flowing through the clutch coil is controlled so that the steering wheel operates between the friction plate and the drive rotor when the steering wheel is operated. Torque control means that enables transmission of torque and blocks transmission of torque between the drive rotor and the friction plate when returning the handle is provided, so that the handle is returned to its original position. When returning, the handle can be smoothly returned without receiving the load of the loss torque of the electric motor.

According to the second aspect of the present invention, the transmission plate is formed of a spring, and when the handle is returned, the friction plate slides on the drive rotor by the elastic force of the transmission plate. Therefore, when the clutch coil is energized and the friction plate is coupled to the drive rotor, the friction plate does not collide with the drive rotor and does not generate a collision sound.

According to the third aspect of the present invention, when the steering wheel is returned, the friction plate is brought into sliding contact with the drive rotor by the electromagnetic force generated by the current flowing through the clutch coil. There is an effect similar to that of the second aspect.

According to the electric power steering apparatus of the present invention, a permanent magnet is disposed on the outer periphery of the clutch stator, and when the handle is returned, the friction plate slides on the drive rotor by the magnetic force of the permanent magnet. Since they are in contact with each other, the same effect as that of the second aspect is obtained.

According to the electric power steering apparatus of the fifth aspect, the permanent magnets are provided at equal intervals in the circumferential direction of the clutch stator, so that when the handle is returned, the friction plate is shifted. Without contact with the drive rotor with even force.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a relationship between each operation of a steering wheel, an electromagnetic clutch, and an electric motor in the electric power steering device according to the first embodiment, in comparison with a conventional example.

FIG. 3 is a sectional view of a main part of an electric power steering apparatus according to Embodiment 2 of the present invention;

FIG. 4 is a sectional view of a main part of a conventional electric power steering device.

[Explanation of symbols]

Reference Signs List 1 motor, 4 magnets, 5 output shafts, 7 cores, 8 armature coils, 14 clutch stator, 15 clutch coils, 16 drive rotor, 18 boss, 20 friction plate, 21 armature, 30 electromagnetic clutch, 31 transmission plate, 32 Permanent magnet, 40 torque control means.

Continued on the front page (72) Inventor Toshinori Tanaka 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (5)

[Claims] An output shaft, a core fixed to the output shaft,
An electric motor having an armature coil having a core wound with a conductor and constituting an armature together with the core, wherein the armature rotates by an electromagnetic force generated by energizing the armature coil; and the output shaft A drive rotor fixed to the drive rotor, a clutch stator provided around the drive rotor, a clutch coil provided inside the clutch stator, a friction plate facing the outer peripheral portion of the drive rotor, and the friction plate provided on the outer peripheral portion. A fixed transmission plate, and a boss provided coaxially with the output shaft and connected to a steering assist torque transmission mechanism, wherein the torque of the armature is transmitted to the steering assist torque transmission mechanism by coupling a friction plate and a drive rotor. An electromagnetic clutch adapted to transmit the current to the clutch coil and controlling the current flowing through the clutch coil so as to be in front of the friction plate when operating the steering wheel. Torque control means for enabling transmission of torque between the drive rotor and the transmission of torque between the drive rotor and the friction plate when the handle is returned. Electric power steering device. 2. The electric power steering apparatus according to claim 1, wherein the transmission plate is constituted by a spring, and when the handle is returned, the friction plate slides on the drive rotor by the elastic force of the transmission plate. 3. The electric power steering apparatus according to claim 1, wherein when the steering wheel is returned, the friction plate comes into sliding contact with the drive rotor by an electromagnetic force generated by a current flowing through the clutch coil. 4. The electric motor according to claim 1, wherein a permanent magnet is provided on an outer peripheral portion of the clutch stator, and when the handle is returned, the friction plate slides on the drive rotor by the magnetic force of the permanent magnet. Power steering device. 5. The electric power steering apparatus according to claim 4, wherein the permanent magnets are provided at equal intervals in a circumferential direction of the clutch stator.