JPH0723624Y2 - Electromagnetic clutch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an electromagnetic clutch capable of changing a transmission torque between an input side rotating member and an output side rotating member.

[Prior Art] A conventional electromagnetic clutch is disclosed, for example, in Japanese Patent Application Laid-Open No. 61-37581.

In this conventional example, a clutch device is provided between a rotary shaft of an electric motor that generates a steering assist force in an electric power steering device and a reduction gear connected to a steering mechanism.
The clutch device is fixed to a first clutch piece that is spline-engaged with the rotary shaft of the electric motor so as to be slidable in the axial direction, and to a worm shaft that is opposed to the first clutch piece at a predetermined interval and has a worm as a reduction gear. The second clutch piece and an electromagnetic solenoid disposed on the opposite side of the second clutch piece from the first clutch.

Thus, when the electromagnetic solenoid is in the non-excited state,
Since the first clutch piece and the second clutch piece are separated from each other, the transmission torque between the electric motor and the worm shaft is zero.

When the electromagnetic solenoid is energized from this state to be excited, the magnetic force of the electromagnetic solenoid causes the first clutch piece to be attracted to the second clutch piece side, and the two are pressed against each other to transmit the rotational torque of the electric motor to the worm shaft. .

[Problems to be solved by the device]

However, in the above-mentioned conventional electromagnetic clutch, since the transmission torque is controlled in the non-excited state and the excited state of the electromagnetic solenoid, the transmission torque control of the electromagnetic clutch is limited to two modes of "disconnection / continuation". An electromagnetic clutch is provided between the electric motor that generates the steering assist torque of the electric power steering device and the steering system.When the vehicle speed is lower than a predetermined speed, the electromagnetic clutch is connected, and when the vehicle speed is higher than the predetermined speed, the electromagnetic clutch is engaged. When configuring a vehicle speed-sensitive power steering apparatus that disconnects the vehicle, the electromagnetic clutch is in the connected state until the vehicle speed reaches the predetermined vehicle speed, so the steering force on the steering wheel can be light, but when the vehicle speed reaches the predetermined vehicle speed. Since the electromagnetic clutch suddenly becomes disengaged, the steering force on the steering wheel becomes heavy, especially when the vehicle is traveling near the prescribed vehicle speed. The electromagnetic clutch is frequently disengaged, which gives the driver a feeling of strangeness, and when the electromagnetic clutch is engaged, when the electromagnetic solenoid is energized, the clutch pieces collide with each other, causing connection noise. There was an unsolved problem of doing.

Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the conventional example, and an object thereof is to provide an electromagnetic clutch capable of smoothly connecting the electromagnetic clutch.

[Means for Solving the Problems]

In order to achieve the above object, an electromagnetic clutch according to the present invention is provided with an armature that is attracted by a magnetic force of an exciting coil on one of an input side rotating member and an output side rotating member, and the other side of the armature. In an electromagnetic clutch provided with opposing friction plates, the armature and the friction plate are always in sliding contact regardless of the excitation state of the exciting coil, and the coupling force between the two is dependent on the exciting current supplied to the exciting coil. It is characterized by having changed.

[Action]

In the electromagnetic clutch according to the present invention, the armature and the friction plate are in sliding contact with the exciting coil in a non-excited state, but the input side rotating member and the output side rotating member are not connected due to the sliding between the armature and the friction plate. . When the drive current to the exciting coil is gradually increased from this state, the electromagnetic attraction force acts on the armature and the coupling force with the friction plate gradually increases according to the drive current, and the force between the armature and friction plate increases. The transmission torque can be changed gradually. Therefore, it is possible to prevent shock and impact noise when the clutch is engaged.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram when an electromagnetic clutch according to the present invention is applied to an electric power steering device, and FIG. 2 is a sectional view of the electromagnetic clutch according to the present invention.

First, an outline of the electric power steering device will be described with reference to FIG.

In the figure, reference numeral 1 denotes a steering wheel, the steering force of which is transmitted through a steering shaft 2 to a steering gear 3
Is transmitted to and the steered wheels are steered.

An output shaft 7a of an electric motor 7 is connected to the steering shaft 2 via a reduction gear 5 and an electromagnetic clutch 6, and the electromagnetic clutch 6 and the electric motor 7 are controlled by a controller 8.

The controller 8 receives the detection values of the vehicle speed sensor 9 and the steering torque sensor 10 that detects the steering torque applied to the steering wheel 1. Based on the vehicle speed detection value of the vehicle speed sensor 9, the vehicle speed detection value is set to a predetermined vehicle speed. When less than, the rated exciting current of a relatively high current value for maintaining the electromagnetic clutch 6 in the connected state is supplied to the electromagnetic clutch 6, and the value of the exciting current is gradually decreased when the vehicle speed exceeds a predetermined set value. When the vehicle speed is above the predetermined set vehicle speed and below the predetermined set 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 controlled based on the steering torque detection value. Then, a steering assist torque proportional to the steering torque is generated.

As shown in FIG. 2, the electromagnetic clutch 6 includes a cylindrical stator 12 fixed to a fixed portion by a bracket 11 and made of a magnetic material. The electromagnetic clutch 6 faces the right end surface of the stator 12 and rotates with respect to the stator 12. A rotor 13 made of a first magnetic body, which is freely held as an input side rotating member, and a rotor 14 made of a second magnetic body, which is rotatably fitted on the rotor 13 and serves as an output side rotating member. I have it.

The stator 12 includes an annular groove 12a formed inside, an exciting coil 12b provided in the annular groove 12a, and a disk body 12c closing the annular groove 12a.
The output shaft 7a is rotatably mounted via a ball bearing 12d.

The cylindrical base portion 13a on the inner peripheral side of the first rotor 13 is externally fitted to the output shaft 7a of the electric motor 7 so as to rotate integrally with the key 13b, and is relatively thick extending from the base portion 13a in the radial direction. An annular friction plate 13d is arranged on the right end surface of the meat disk-shaped portion 13c.

The second rotor 14 has a bolt 14a on the end plate 5b provided at the end of the input shaft 5a of the reduction gear 5 so that the inner peripheral surface faces the right end of the base 13a of the rotor 13 with a predetermined gap. The fixed cylindrical body 14b and the bolt on the inner peripheral surface side of the cylindrical body 14b.
Leaf spring as a disc-shaped elastic body fixed by 14c 1
4d and an armature 14 composed of an annular plate made of a magnetic material fixed to the friction plate 13d of the first rotor 13 of the leaf spring 14d with, for example, rivets 14f.
It has g and. Here, the armature 14g is always in light sliding contact with the friction plate 13d of the first rotor 13 to the extent that transmission torque is not generated by the biasing force of the leaf spring 14d.

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 set vehicle speed, so that the controller 8 supplies the exciting current of the rated current to the exciting coil 12b of the electromagnetic clutch 6. As a result, the electromagnetic force generated in the exciting coil 12b acts on the armature 14g arranged on the second rotor 14 via the disc-shaped portion 13c of the first rotor 13, and the armature 14g is attracted to the circle. The rotational torque that is pressed against the friction plate 13d arranged on the plate-like portion 13c and that is input from the output shaft 7a of the electric motor 7 is input to the reduction gear 5.
The connection state is controlled so that the maximum transmission torque T _MAX shown in FIG.

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

When the steering wheel 1 is turned to the right (or left) from this state, the steering torque sensor 10 outputs a steering torque detection value according to the steering torque, which is input to the controller 8. A drive current according to the magnitude and direction is output to the electric motor 7 to drive the electric motor 7 in the forward (or reverse) direction. As a result, the rotational torque of the output shaft 7a of the electric motor 7 is changed to the first rotor 13 and the second rotor 14 of the electromagnetic clutch 6.
Is transmitted to the input shaft 5a of the reduction gear 5 and is decelerated by the reduction gear 5 and transmitted to the steering shaft 2 to generate steering assist torque, so that the steering wheel 1 can be lightly steered.

Then, when the vehicle starts traveling 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. When the exciting current supplied to the electromagnetic clutch 6 is decreased in this way, the attraction force of the armature 14g due to the electromagnetic force generated in the exciting coil 12b is gradually decreased accordingly, and the armature 14g is reduced.
When the coupling force between the friction plate 13d and the friction plate 13d gradually decreases and the transmission torque decreases due to the slip between the two, and the exciting current becomes close to zero, 100% slip occurs between the armature 14g and the friction plate 13d. The transmission torque becomes zero, and the electromagnetic clutch 6 becomes disengaged.

In this way, when the electromagnetic clutch 6 is switched from the connected state to the disconnected state, the transmission torque in the electromagnetic clutch 6 is gradually reduced, so that the steering feeling of the driver who steers the steering wheel 1 is smooth and smooth. Can be switched.

On the contrary, even when the vehicle is in a state where the vehicle speed is lower than the predetermined set vehicle speed, the exciting current output from the controller 8 to the electromagnetic clutch 6 is gradually increased, and accordingly, between the armature 14g and the friction plate 13d. The coupling force due to friction gradually increases, the transmission torque between the armature 14g and the friction plate 13d also gradually increases,
When the exciting current exceeds the preset value, armature 14g
Also, slippage between the friction plates 13d is eliminated, and the maximum transmission torque T _MAX is brought into the connected state, so that the electromagnetic clutch 6 can be smoothly switched from the disconnected state to the connected state.

Further, as in the above embodiment, the exciting coil 12 is attached to the stator 12.
By winding b, it is possible to supply power to the exciting coil 12b without using a slip ring, a brush or the like.

In the above embodiment, the case where the leaf spring 14d is applied as the elastic body that supports the armature 14g has been described, but the present invention is not limited to this, and any elastic body such as a coil spring or rubber may be applied. It is a thing.

In the above embodiment, the friction plate 13d is provided on the rotor 13 and the armature 14g elastically supported on the rotor 14 is provided.However, these elements are arranged in reverse relation to each other so that the friction plate is provided on the rotor 14 and the armature is provided on the rotor 13g.
May be provided in each.

Furthermore, in the above embodiment, the case where the exciting current supplied to the electromagnetic clutch 6 is gradually increased or decreased by the controller 8 has been described, but the present invention is not limited to this, and the exciting current may be changed stepwise.

Further, in the above embodiment, the case where the present invention is applied to the vehicle speed sensitive electric power steering device has been described, but the present invention is not limited to this and can be applied to other power transmission devices.

[Effect of device]

As described above, according to the present invention, since the armature and the friction plate are in sliding contact with each other in the non-excited state of the exciting coil, the exciting current supplied to the exciting coil is changed to change the attraction force for the armature. By this, the coupling force between the friction plate and the armature can be changed, and the transmission torque between the input side and the output side can be continuously changed,
When switching the electromagnetic clutch from the disconnected state to the connected state,
It is possible to reliably prevent the generation of collision noise, and to smoothly switch whether to apply the steering assist torque when applied to a vehicle speed-sensitive electric power steering device, for example. Therefore, it is possible to reliably prevent the driver from feeling uncomfortable.

[Brief description of 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, and FIG. 2 is a sectional view showing an example of an electromagnetic clutch according to the present invention.
The figure is a characteristic diagram showing the relationship between the transmission torque and the exciting current. 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering gear, 5 ... Reduction gear, 6 ...
... electromagnetic clutch, 7 ... electric motor, 8 ... controller, 9 ... vehicle speed sensor, 10 ... steering torque sensor, 12 ...
... Stator, 12b ... Excitation coil, 13 ... Rotor (rotating member on the input side), 13d ... Friction plate, 14 ...
Rotor (rotating member on the output side), 14d ... leaf spring (elastic body), 14g ... armature.

Claims (1)

[Scope of utility model registration request] 1. An electromagnetic clutch in which an armature to be attracted by the magnetic force of an exciting coil is disposed on either one of the input side rotating member and the output side rotating member, and the other side is provided with a friction plate facing the armature. An electromagnetic clutch, wherein the armature and the friction plate are always in sliding contact with each other regardless of the excitation state of the excitation coil, and the coupling force between the two is changed according to the excitation current supplied to the excitation coil.