JP2585705Y2 - Electromagnetic clutch in electric power steering system - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an electromagnetic clutch applied to an electric power steering apparatus which generates a steering assist force corresponding to a steering torque to a steering system.

[0002]

2. Description of the Related Art A conventional electromagnetic clutch is, for example, a "new edition.
Automobile Engineering Handbook "(published by Tosho Publishing Co., Ltd. on September 11, 1884). In this conventional example, an armature urged outward by an elastic body is disposed on a flywheel containing an electromagnetic coil on a surface facing the electromagnetic coil, and a pressure plate is integrated with the armature at a predetermined interval. Arrange,
The clutch disk is rotatably arranged between the armature and the pressure plate.

When the electromagnetic coil is in the non-excited state, the armature is urged away from the flywheel by the elastic body, so that the pressure plate provided integrally with the armature is engaged with the clutch disk. More distant, the transmission torque between the flywheel and the clutch disc is zero. When the electromagnetic coil is energized from this state to be in an excited state, the armature is attracted to the flywheel side by the magnetic force of the electromagnetic coil,
In response, the pressure plate comes into frictional contact with the clutch disk, and the rotational torque of the flywheel is transmitted to the clutch disk.

The electromagnetic clutch applied to the electric power steering apparatus is in a connected state during normal running at a predetermined vehicle speed or less, and generates a steering assist force in accordance with a steering torque in a steering system. There are two types: one that keeps the connection state as it is, and one that controls it to the non-connection state in order to secure the straight running stability at the time of high-speed running exceeding the predetermined vehicle speed. Both the former and the latter detect abnormality of the electric power steering device. At times, the electromagnetic clutch is controlled to a non-connected state in order to give priority to steering by manual steering alone.

[0005]

However, in the above-mentioned conventional electromagnetic clutch, the transmission torque is controlled in the non-excited state and the excited state of the electromagnetic coil, so that the excitation supplied to the electromagnetic clutch is controlled. transmission torque characteristics for current, as shown by the characteristic curve L ₁ in FIG. 3, until the exciting current supplied to the electromagnetic coil reaches a predetermined value I _IH the transmission torque maintains the disconnected state of zero, When the predetermined value I _1H is reached, the electromagnetic clutch is engaged, the transmission torque sharply increases to the predetermined value T _1H, then increases as the exciting current increases, and then decreases the exciting current.
At a predetermined value I _1L smaller than the predetermined value I _1H , the electromagnetic clutch is set in a non-connected state, the transmission torque becomes zero, and a hysteresis characteristic is provided.

Since the electromagnetic clutch is switched to the disconnected state even in an abnormal prediction state due to overheating of the electric motor of the electric power steering apparatus, for example, the steering assist force generated by the electric motor is transmitted to the steering system. Since the transmission of the steering assist force is suddenly interrupted from the state in which the steering assist force is transmitted, the steering force is changed from the light steering state in which the steering assist force is transmitted to the heavy steering state in which only the manual steering force is applied, and then the electric motor is overheated Is resolved and the electromagnetic clutch is controlled to the connected state when the vehicle returns to the normal state, so that the steering state suddenly changes from the heavy steering state to the light steering state, and when the electromagnetic clutch is switched, a feeling of strangeness in steering occurs and the steering feeling decreases. There was an unsolved problem. Also, since the excitation current and transmission torque characteristics of the electromagnetic clutch have a hysteresis characteristic at the clutch operating point, when the clutch is used in a half-connected state, the half-connection point becomes unstable due to the variation in hysteresis, and The torque transmission limit point T _1L also becomes considerably large, and even if the exciting current is reduced to the torque transmission limit point T _1L at the time of abnormality prediction of the electric power steering device, these will be reduced during abnormal operation such as motor lock or motor rotation. There is an unsolved problem that a considerably large steering force is required to avoid and steer.

The purpose of the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and prevents a sudden change in the steering force at the time of an abnormality of the electric power steering apparatus, thereby improving the sense of steering. An object of the present invention is to provide an electromagnetic clutch in an electric power steering device capable of suppressing deterioration.

[0008]

In order to achieve the above object, an electromagnetic clutch in an electric power steering apparatus according to the present invention includes an electric motor for generating a steering assisting force for a steering system, the electric motor and the electric motor. comprising an electromagnetic clutch interposed between the steering system, and control means at least controlling the electric motor in accordance with the steering torque, and to control at the time of abnormality of the electric motor control system the electromagnetic clutch is deenergized In the electric power steering apparatus, the electromagnetic clutch includes a clutch rotor and the clutch low.
Armature that is arranged to be able to contact the
The energization is controlled by the control means.
Force the clutch armature into the clutch
Excitation coil to be brought into contact with the
Regardless of the state, the clutch armature
Against Tchirota, characterized by having a a semi-connected mechanism contacting with a contact pressure for generating a predetermined transmission torque.

[0009]

The electromagnetic clutch in the electric power steering apparatus according to the present invention is in a semi-connected state so as to generate a predetermined transmission torque in a non-energized state of the exciting current. When this occurs, the electromagnetic clutch acts as a torque limiter, and the abnormal state can be easily avoided by manual steering, and the steering assist generated by the electric motor when returning to the abnormal prediction state or the normal state thereafter. Since a part of the force is transmitted to the steering system, a sudden change in the steering force can be prevented, and deterioration of the steering feeling can be suppressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram when the electromagnetic clutch according to the present invention is applied to an electric power steering device,
1 is a sectional view of an electromagnetic clutch according to the present invention. First,
The outline of the electric power steering apparatus will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a steering wheel, the steering force of which is transmitted to a steering gear 3 via a steering shaft 2 to steer the steered wheels. An output shaft 7a of a DC electric motor 7 is connected to the steering shaft 2 via a reduction gear 5 and an electromagnetic clutch 6.
The electromagnetic clutch 6 and the electric motor 7 are controlled by the controller 8.

The controller 8 receives a vehicle speed sensor 9 and a detection value of a steering torque sensor 10 for detecting a steering torque applied to the steering wheel 1, and based on the vehicle speed detection value of the vehicle speed sensor 9, calculates a vehicle speed detection value. When the vehicle speed is lower than the predetermined vehicle speed, a relatively high current value of the exciting current for maintaining the electromagnetic clutch 6 in the connected state is supplied to the electromagnetic clutch 6, and when the vehicle speed exceeds the predetermined vehicle speed, the value of the exciting current gradually decreases. Conversely, when the vehicle speed is changed from a speed equal to or higher than the predetermined vehicle speed to a speed lower than the predetermined vehicle speed, control is performed to gradually increase the exciting current to the rated exciting current, and the drive current of the electric motor 7 is determined based on the detected steering torque. Control the
A steering assist torque proportional to the steering torque is generated. Further, the controller 8 has a built-in abnormality detection circuit for detecting an overload state, an overheat state of the electric motor and an abnormality of the control system,
When an abnormality is detected by the abnormality detection circuit, the exciting current value supplied to the electromagnetic clutch 6 is gradually reduced to zero, and when the abnormal state is eliminated, the exciting current value is gradually increased to the rated exciting current value.

The electromagnetic clutch 6 and the electric motor 7 are shown in FIG.
As shown in FIG. 2, the electric motor 7 is integrally formed. One end of a rotating shaft 7a of the electric motor 7 is pivotally mounted on a bottom of a case body 7b having a substantially U-shaped cross section via a rolling bearing 7c. The other end of the shaft 7a is pivotally mounted on a rolling bearing 7e formed at the center of a flanged end plate 7d that closes the open end of the case body 7b, and is wound around an armature 7f formed integrally with the rotating shaft 7a. An exciting current is supplied to the armature winding 7g thus completed via the brush 7h and the commutator 7i.

The electromagnetic clutch 6 has an exciting coil 6b disposed in an annular magnetic yoke 6a mounted on an end plate 7d of the electric motor 7, and a rolling bearing for a rotary shaft 7a of the electric motor 7. A clutch rotor 6c is spline-fitted to a protruding portion protruding from 7e, and a rotating plate 6d coupled to the input shaft 5a of the reduction gear 5 is rotatably arranged facing the clutch rotor 6c. A clutch armature 6g is attached via a leaf spring 6f to a surface of the rotating plate 6d facing the friction plate 6e formed on the outer peripheral surface side of the clutch rotor 6c, and the clutch armature 6g faces the clutch rotor 6c. The surface of the clutch rotor 6c always has an opposite polarity to the magnetic pole generated on the armature 6g side surface of the clutch rotor 6c by energizing the exciting coil 6b, that is, regardless of the energizing state of the exciting coil 6b.
-Magnet for bringing 6 g of armature into contact with clutch rotor 6c
A permanent magnet 6h is provided as a semi-connection mechanism for generating a force . Therefore, even when the exciting coil 6b is not energized, the clutch armature 6g comes into contact with the clutch rotor 6c by the magnetic force of the permanent magnet 6h, and the predetermined transmission torque T ₂ lower than the above-described torque transmission limit value T _1L in the conventional example. Are biased to be in a semi-connected state. Here, the transmission torque T ₂ is selected to such an extent that the electric motor 7 is stopped, that is, in a state where no steering assist force is generated in the steering system, and a slip is generated by the steering force when the steering wheel 1 is steered. ing.

Next, the operation of the above embodiment will be described. now,
Assuming that the vehicle is in a stopped state, in this state, the vehicle speed is zero and less than the predetermined vehicle speed, so that the exciting current of the rated current is supplied from the controller 8 to the exciting coil 6 b of the electromagnetic clutch 6. Thereby, the exciting coil 6b
The electromagnetic force generated in (1) acts on the clutch armature 6g held on the second rotary plate 6e via the clutch rotor 6c, and this armature 6g comes into contact with the clutch rotor 6c and is input from the output shaft 7a of the electric motor 7. 3 is controlled to a connection state in which the rotation torque can be transmitted to the input shaft 5a of the reduction gear 5 with the maximum transmission torque _TMAX shown in FIG.

In this state, when the steering force is not applied to the steering wheel 1, the drive current is not output from the controller 8 to the electric motor 7 because the detected torque value of the steering torque sensor 10 is zero. , The electric motor 7 maintains the rotation stopped state, and the input shaft 5 of the reduction gear 5
a also maintains the rotation stopped state, and no steering assist torque is generated.

When the steering wheel 1 is turned right (or left) from this state, a steering torque detection value is output from the steering torque sensor 10 in accordance with the steering torque, which is input to the controller 8. A drive current corresponding to the magnitude and direction of the steering torque is output to the electric motor 7, and the electric motor 7 is driven forward (or reverse). Thereby, the output shaft 7 of the electric motor 7
a rotational torque of the clutch rotor 6 of the electromagnetic clutch 6
c, transmitted to the input shaft 5a of the reduction gear 5 via the armature 6g and the rotating plate 6d, reduced by the reduction gear 5 and transmitted to the steering shaft 2 to generate a steering assist torque, thereby controlling the steering of the steering wheel 1. Can be done lightly.

When the vehicle starts running and reaches a predetermined vehicle speed, the exciting current output from the controller 8 to the electromagnetic clutch 6 is gradually reduced from the rated current value. As described above, when the exciting current supplied to the electromagnetic clutch 6 decreases, the attraction force of the armature 6g due to the electromagnetic force generated by the exciting coil 6b also gradually decreases,
The transmission torque of the electromagnetic clutch is reduced as indicated by the characteristic curve L ₂ in FIG.

When the exciting current becomes zero, the magnetic force generated by the exciting coil 6b becomes zero. However, since the permanent magnet 6h is attached to the armature 6g, the permanent magnet is provided between the clutch rotor 6c and the armature 6g. 6h
Residual transmission torque T ₂ by the magnetic force of the rest, the clutch rotor 6c and the armature 6g continues contact, maintains a semi-connected state. At this time, when the torque exceeds the transmission torque T ₂ is inputted from the output shaft 7a of the electric motor 7, slippage between the clutch rotor 6c and the armature 6 g, it operates as a torque limiter.

As described above, even if the exciting current to the exciting coil 6b is gradually reduced to zero, the transmission torque is continuously reduced without causing a discontinuity point, so that the steering feeling does not become uncomfortable. A good steering feeling can be secured. Conversely, also when the vehicle changes from a high-speed running state to a state below the predetermined vehicle speed, the exciting current output from the controller 8 to the electromagnetic clutch 6 is gradually increased,
Will be transmitting torque of the electromagnetic clutch 6 is continuously increased as indicated by the characteristic curve L ₂ in FIG. 3 in response to this, as shown by the characteristic curve L ₁ in FIG. 3 in the conventional example, the transmitted torque surge Since no discontinuous point is formed, it is possible to smoothly change the transmission torque without causing an uncomfortable feeling in the steering feeling. Further, since maintaining a semi-connected state to keep the remaining transmission torque T ₂ also exciting coil 6b as a non-energized state, the clutch rotor 6c and the armature 6g has always contact, since no two are separated, As in the conventional example, it is possible to avoid the generation of an impact sound between the clutch rotor 6c and the armature 6g when shifting from the disconnected state to the connected state, and
Since there is no need to provide hysteresis characteristics at the clutch operating point, the half-connected torque point can be set low.

Further, even when an abnormal state such as overload or overheating of the electric motor 7 is detected by the abnormality detecting circuit built in the controller 8, the current value is gradually increased from the energized state of the exciting coil 6b of the electromagnetic clutch 6. the process moves to decrease the allowed and non-energized state, even in this case, the transmission torque continuously decreases according to the decrease of the excitation current, in a non-energized state the residual transmission torque T _2. Such overload, even in the event an abnormal state of overheating, etc., the driving of the electric motor 7 is continued, because it is selected to a smaller value residual transmission torque T _2, the load of the electric motor 7 is In addition to the reduction, the steering assist force generated by the electric motor 6 is also transmitted to the reduction gear 5 by the residual transmission torque T _2, so that the steering can be performed lighter than in the manual steering state. Thereafter, when the abnormal state is resolved and the state returns to the normal state, the exciting current to the exciting coil 6b is gradually increased and is returned to the rated exciting current.

On the other hand, when a rotation abnormality such as motor lock or rotation of the electric motor 7 occurs, the excitation coil 6b is de-energized as described above. In this case, the motor operates as a torque limiter and an excessive torque Is transmitted, and the residual transmission torque T ₂ is applied as a load to the steering torque. However, by selecting the residual transmission torque T ₂ to a small value, a large steering resistance is not applied, and manual steering is performed. It can be done easily.

In the above embodiment, the case where the permanent magnet 6h is applied as the semi-connection mechanism has been described. However, the present invention is not limited to this, and an exciting coil may be provided to make an electromagnet. The preload may be mechanically applied by an elastic body such as a spring 6f or a disc spring.
In the above-described embodiment, the case where the clutch rotor 6c and the clutch armature 6g are always in contact with each other has been described. The direction of energization of the exciting coil 6b of the rotor 6c is reversed, and the polarity of the clutch rotor 6c is reversed, and the clutch rotor 6c is disengaged by utilizing the repulsive force with the permanent magnet 6h, or the clutch armature 6g side An excitation coil is also provided in the motor, and the excitation coil and the excitation coil of the clutch rotor 6c
By exciting the clutch rotor 6c and the clutch armature 6g to polarities that repel each other, the two can be brought into a disconnected state. When the engine is started in the vehicle, the electromagnetic clutch is brought into a non-contact state and the electric motor is rotated. The locked state can be detected.

Further, when the electromagnetic clutch 6 is turned off and the electric motor 7 is stopped when the abnormality of the electric power steering apparatus is predicted, the residual transmission torque T ₂ is determined by the clutch rotor 6c and the clutch armature 6g. may be a residual transmission torque T ₂ substantially zero on condition that the securing the contact state. The method of controlling the transmission torque of the electromagnetic clutch 6 is not limited to the above-described embodiment. The excitation current is controlled in proportion to the motor current, and the motor drive current and the clutch excitation current are both set to zero during straight running of the vehicle. In these cases, the exciting current of the electromagnetic clutch becomes zero during straight running, which is effective as an energy saving measure.

Further, in the above embodiment, the controller 8
Although the case where the exciting current supplied to the electromagnetic clutch 6 is gradually increased and decreased has been described above, the present invention is not limited to this, and the exciting current may be changed stepwise. Further, in the above-described embodiment, the case where the present invention is applied to the vehicle speed-sensitive electric power steering device has been described. However, the present invention is not limited to this and can be applied to other power transmission devices.

[0026]

As described above, according to the present invention, even when the excitation coil is not energized, the clutch rotor and the clutch armature are brought into contact with each other to provide a predetermined connection torque by the semi-connection mechanism. As a result, even if the abnormality of the electric power steering device is detected and the exciting current to the exciting coil is cut off, it does not become a disconnected state, so that a part of the steering assist force generated by the electric motor is used for the steering system. Can be maintained, light steering can be maintained, and when the exciting current is increased or decreased, the transmission torque is continuously changed, and there is no large change in the steering force, so that there is no discomfort , The steering feeling can be maintained well, and the clutch rotor and the clutch armature are always in contact with each other.
Even when the exciting current is turned on / off, no contact noise is generated by the operation of the clutch, and it is possible to surely prevent the occupant from feeling uncomfortable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example in which the present invention is applied to a vehicle speed-sensitive electric power steering device.

FIG. 2 is a sectional view showing an example of the electromagnetic clutch according to the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a transmission torque and an exciting current in the present invention and a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Steering gear 5 Reduction gear 6 Electromagnetic clutch 6b Exciting coil 6c Clutch rotor 6g Clutch armature 6h Permanent magnet 7 Electric motor 8 Controller 9 Vehicle speed sensor 10 Steering torque sensor

Claims (2)

(57) [Scope of request for utility model registration] An electric motor for generating a steering assist force for a steering system; an electromagnetic clutch interposed between the electric motor and the steering system; and controlling the electric motor at least according to a steering torque. and in the abnormal time of the electric motor control system electric power steering apparatus and control means for controlling the electromagnetic clutch de-energized, the electromagnetic clutch, and the clutch rotor, said clutch
Clutch armature arranged to be able to contact the rotor
Power is controlled by the control means, and occurs when power is supplied.
The clutch armature by the magnetic force
An exciting coil to be brought into contact with the
Regardless of the energized state, keep the clutch armature
Against serial clutch rotor, the electromagnetic clutch in the electric power steering apparatus characterized by having a semi-connected mechanism contacting with a contact pressure for generating a predetermined transmission torque. 2. The clutch armor according to claim 2, wherein the semi-connection mechanism includes the clutch armor.
The clutch is closed regardless of the energizing state of the exciting coil.
The electromagnetic clutch in the electric power steering apparatus according to claim 1, comprising a permanent magnet or an electromagnet that generates a magnetic force to be brought into contact with the motor side.