JPH0322580Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electromagnetic clutch, and more particularly to an electromagnetic clutch that prevents a reduction in frictional torque between a clutch rotor and an armature due to temperature changes.

[Prior Art] Conventionally, in this type of electromagnetic clutch, as shown in FIG. It is rotatably supported via a bearing 2. A main shaft 5, which rotates as the rotation of the clutch rotor 3 is transmitted through the armature 8, is inserted into the cylindrical projection 1a. The main shaft 5 is rotatably prevented by a bearing (not shown) provided on the fixed part 1.

The clutch rotor 3 consists of concentric double cylinders and a flange part 3a fixed at one end of these cylinder parts, the inner wall of the inner cylinder part 3b fits into the outer peripheral part of the radial bearing 2, and the flange part 3a faces the armature 8. are doing. An excitation coil 4 is disposed within a space defined by the concentric double cylinder portion and the flange portion 3a.

Furthermore, a friction surface 3c is formed on the armature 8 side of the flange portion 3a, and slits 3d, 3d' are formed at intervals in the radial direction.

The armature 8 has a hub 9 and a leaf spring 6 on the main shaft 5.
The clutch rotor 3 is connected to the clutch rotor 3 via a stopper plate 7, and is disposed opposite to the flange portion 3a of the clutch rotor 3 at a distance l. A friction surface 8a is formed on the flange portion 3a side of the armature 8.

According to the above electromagnetic clutch, when the excitation coil 4 is energized, the outer cylindrical portion of the clutch rotor 3, the outer peripheral portion of the armature 8, between the slits 3d and 3d' of the flange portion 3a of the clutch rotor 3, and the armature 8
Magnetic flux flows through the inner diameter side 8c and the inner cylinder portion 3b. As a result, the armature 8 is attracted to the friction surface 3c of the clutch rotor 3, and as a result, the main shaft 5
rotates together with the clutch rotor 3.

[Problem that the invention attempts to solve]

For example, when the external temperature drops during winter, chemical changes within the battery become inactive, resulting in a voltage drop in the battery. When the magnetic force generated in the excitation coil of the electromagnetic clutch decreases due to such battery voltage drop, the force that attracts the armature to the clutch rotor decreases. At this time, with the above-mentioned electromagnetic clutch, a sliding phenomenon occurs on the friction surface between the clutch rotor and the armature, resulting in problems such as an increase in the amount of friction on the friction surface and the armature seizing on the clutch rotor. Ta.

Therefore, the purpose of this invention is to reduce the frictional force between the clutch rotor and the armature even when the magnetic force generated in the excitation coil decreases due to battery voltage drop, etc., and the force that attracts the armature to the clutch rotor decreases. The object of the present invention is to provide an electromagnetic clutch that does not deteriorate.

[Means for solving problems]

In order to solve the above problems, the present invention combines a clutch rotor rotated by an external drive source and an armature disposed opposite the flange of the clutch rotor with the magnetism of the excitation coil disposed inside the clutch rotor. A friction surface formed on a flange portion of the clutch rotor in a magnetic clutch which is included in a circuit and attracts the armature to the clutch rotor by excitation of a magnetic circuit of an excitation coil of the magnetic circuit and transmits rotational force. A friction member having an expandable member that expands and contracts due to temperature changes is disposed on at least one side of the friction surface of the armature facing the surface, and the friction member is pressed against the other opposing friction surface due to temperature changes. It has a configuration like this. As the expandable member, bimetal or shape memory alloy is used.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings. Incidentally, the same or similar parts as in the conventional example shown in FIG. 5 are indicated by the same reference numerals, and the explanation thereof will be omitted.

FIG. 1 is a cross-sectional view of an electromagnetic clutch showing a first embodiment of the present invention, in which a recess 20 is formed in a flange 3a between slits 3d and 3d' for a magnetic gap. has been done. Inside this recess 20, as shown in FIG. facing the recess 2
It is arranged so that it is accommodated within 0.

When the excitation coil 4 of this electromagnetic clutch is energized, the armature 8 is attached to the flange portion 3a of the clutch rotor 3 in the same manner as explained with reference to FIG.
is magnetically attracted. Therefore, the rotational force of the external drive source is transferred from the clutch rotor 3 to the armature 8.
is transmitted to the main shaft 5 via the leaf spring 6, stopper plate 7, and hub 9.

Now, in winter, etc., when the chemical reaction of the battery (not shown) becomes inactive and the magnetic force generated by the excitation coil 4 decreases, resulting in a decrease in friction torque, a sliding phenomenon occurs between the two friction surfaces 3c and 8a, causing frictional heat. occurs. This frictional heat causes the expandable member 22 made of shape memory alloy to expand and move the friction member 21 into the recess 20.
It protrudes from the opening surface of the armature 8 and is brought into pressure contact with the friction surface 8a of the armature 8. As a result, the friction torque is restored and rotational force is reliably transmitted.

FIG. 3 shows a second embodiment of the present invention, in which a shape memory alloy elastic member 22 and a friction member 21 are placed in a recess 23 formed on the armature 8 side. The other configurations are the same as those of the first embodiment shown in FIG. In this case as well, when a slip occurs between the friction surfaces 3c and 8a, the friction member 21 is pressed against the opposing friction surface 3c,
The reduction in frictional torque is compensated.

Fig. 4 is a perspective view of the elastic member 22' formed into a wave-shaped ring, in which the elastic member 22 made of a shape memory alloy and the friction member 21 are made separately.
An example of this is shown. In this example,
As the peak portion 22'a of the wavy ring expands,
The friction material 21 is pressed against the friction surface 8a of the armature 8, and the same effects as in the other embodiments described above are obtained.

Although a shape memory alloy is used as the expandable member 22 in the embodiment, the same effect can be obtained by using a bimetal instead.

The friction member 21 may be formed by, for example, mixing asbestos as pulp fibers, injecting a phenol resin into the mixture, and compressing the mixture.

〔effect〕

As mentioned above, the present invention provides an electromagnetic clutch in which a concave portion is provided on either the friction surface of the flange portion of the clutch rotor or the friction surface of the armature, and a friction member having an expandable member that expands and contracts with temperature changes is provided. Therefore, even if the friction torque between the clutch rotor and armature decreases due to a decrease in the magnetic force generated by the excitation coil due to a decrease in battery performance in winter, for example, the friction torque between the clutch rotor and armature will decrease. Since the friction member can be brought into pressure contact with the other friction surface by utilizing the heat generated by the sliding phenomenon of the friction surface to extend the elastic member, it is possible to compensate for the decrease in friction torque due to the above-mentioned problem.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a first embodiment of the electromagnetic clutch according to the present invention, FIG. 2 is a perspective view showing the friction member used in the embodiment of FIG. 1, and FIG. FIG. 4 is a vertical sectional view showing the second embodiment of the invention, FIG. 4 is a perspective view showing the elastic member of the third embodiment in which the friction member and the elastic member are made separately, and FIG. FIG. 2 is a vertical sectional view showing a conventional electromagnetic clutch. 1... Fixed part, 2... Radial bearing, 3... Clutch rotor, 4... Excitation coil, 5... Main shaft,
6... Leaf spring, 7... Stopper plate, 8...
... Armature, 9 ... Hub, 20 ... Recess, 2
DESCRIPTION OF SYMBOLS 1... Friction member, 22... Expandable member made of shape memory alloy, 3a... Flange part, 3b... Inner cylinder part, 3
d, 3d'...Slit, 3c, 8a...Friction surface,
23...Concavity, l...Gap between clutch rotor and armature.

Claims (1)

[Claims for Utility Model Registration] 1. A clutch rotor rotated by an external drive source and an armature disposed opposite the flange of the clutch rotor in a magnetic circuit of an excitation coil disposed within the clutch rotor. includes,
In an electromagnetic clutch that attracts an armature to a clutch rotor and transmits rotational force by excitation of the magnetic circuit, a friction surface formed on a flange portion of the clutch rotor, a friction surface of the armature opposite to this friction surface; An electromagnetic clutch characterized in that a friction member having an expandable member that expands and contracts with temperature changes is disposed on at least one of the two, and the friction member is brought into pressure contact with the other opposing friction surface as the temperature changes. 2. The electromagnetic clutch according to claim 1, wherein a shape memory alloy is used as the expandable member. 3. The electromagnetic clutch according to claim 1, characterized in that the telescopic member is made of bimetal.