JP2914149B2 - Brush device for starter motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brush device for a starter motor, and more particularly to a brush device suitable for a starter motor for an automobile.

[0002]

2. Description of the Related Art For improving the durability of a metallic graphite brush used for a conventional starter motor for automobiles, for example, one described in Japanese Patent Publication No. 4-74939 is known. For starter motors for automobiles,
The copper content of the brush is 50-80% by weight (percent)
(Hereinafter, all copper contents are based on weight%). In the case of a starter motor for an automobile, the field is often a four-pole wound field or a six-pole permanent magnet field. In each case, the number of brushes is 4 for each of two positive electrodes and two negative electrodes. Individuals are common.

[0003] In a DC motor including a starter motor, if the type of winding of the rotating armature is a wave winding, the number of brushes is at least one for each of the positive electrode and the negative electrode regardless of the number of field poles. Although there is no problem, it is known that the decrease in the number of brushes causes an increase in the current density per brush at the same current, and affects the wear of the brush due to a thermal factor due to heat generation of the brush. I have. Further, as described in Japanese Patent Publication No. Hei 4-74939,
For those requiring high output such as starter motors, metallic graphite brushes with high copper content are preferred, but the higher the copper content, the greater the amount of wear of the brushes due to the increase in the number of uses of the starter motor. Is also known.

Further, in a starter motor using a brush having a large copper content, if the number of brushes is reduced, the power to the starter motor is cut off after the engine is started, and then the braking force against the inertial rotation of the rotating armature by the brush pressing spring is applied. Is reduced, the inertia rotation time of the rotating armature is extended, and brush wear due to mechanical factors due to friction between the commutator and the brush is increased. In combination, the phenomenon that the positive brush is worn more than the negative brush becomes conspicuous.

FIGS. 3 to 6 show a conventional brush device for a starter motor. FIG. 3 is a plan view of the brush device.
4 is a side view showing a state of being mounted on the starter motor, partially cut away, FIG. 5 is a characteristic diagram showing a current of the starter motor when the engine is started, and FIG. 6 is a characteristic diagram showing a wear amount of the brush. In these figures, 1 is a starter motor, and 2 is a yoke. Reference numeral 3 denotes a field pole made of a permanent magnet, which is attached inside the yoke 2, and has six poles. Reference numeral 4 denotes a bracket, which rotatably supports a rotating shaft 9 of a rotating armature 6 described below via a bearing metal 5.

Reference numeral 6 denotes a rotating armature, which is configured as follows. Reference numeral 7 denotes a cylindrical iron core having six field poles 3
Are provided facing the field magnetic poles in a cylindrical space formed inside. The core 7 is wound with an armature coil (not shown). Reference numeral 8 denotes a current element, which is connected to the armature coil. Reference numeral 9 denotes a rotating shaft, which constitutes a rotating armature 6 in which an iron core 7 and a commutator 8 are fitted to the rotating shaft 9 and rotate integrally.

Reference numeral 10 denotes a brush device, which is configured as follows. Reference numeral 11 denotes a disk-shaped substrate formed by stamping a steel plate. 12 is a burring portion of the substrate 11,
Reference numeral 13 denotes an insulating plate, and the insulating plate 13 is fixed to the substrate 11 by caulking at two burring portions 12.
Reference numeral 14 denotes a brush holding frame on the positive electrode side. The brush holding frame 14 is formed from a steel plate by press working, and holds a positive electrode side brush 16 described later at its U-shaped portion so as to be movable in the radial direction of the commutator 8. 1
Reference numeral 5 denotes a caulking portion of the brush holding frame 14, which is formed by burring. The brush holding frame 14 is fixed to the insulating plate 13 by the caulking portion 15 and is insulated from the substrate 11. 16 is a brush on the positive electrode side, 17 is a lead wire connected to the positive electrode brush 16, 18 is a connection terminal connected to the positive electrode of a power supply (not shown), 19 is an insulating bush, and the lead wire 17 is a bracket 4 (FIG. 4). The part penetrating through is insulated. 20 is a brush spring, and brush 1
6 is pressed against the commutator 8.

Reference numeral 21 denotes a brush holding frame on the negative electrode side, which is also made of a rope plate. Reference numeral 22 denotes a caulking portion of the brush holding frame 21, which is formed by burring.
The brush holding frame 21 is fixed to the substrate 11 by a caulking portion 22 without being insulated by caulking. Reference numeral 23 denotes a brush on the negative electrode side, which is held on the brush holding frame 21 so as to be movable in the radial direction of the commutator 8. Reference numeral 24 denotes a lead wire, one side of which is connected to the negative brush 23 and the other side of which is the substrate 11.
(Earth) is electrically connected by welding. 25
Denotes a brush spring, which presses the negative brush 23 against the commutator 8. 26 is a screw for fixing the substrate 11, ie, the brush device 10, to the bracket 4 (FIG. 4).

One brush is used for each of the positive electrode side and negative electrode side brushes configured as described above. This brush is a so-called metallic graphite brush formed by mixing and molding copper powder and graphite powder. The dimensions are width (circumferential dimension of commutator) × depth (coaxial dimension) × height is 4 × 20 × 12 [mm]. The same component is used for both the positive and negative brushes. The component is a mixture of 60% by weight of copper (copper powder), 32% by weight of graphite, and 8% by weight of other components.

A starter motor provided with the brush device 10 having the brushes 16 and 23 is mounted on an engine of a vehicle. And every time the engine starts,
A large current is supplied to the rotating armature 6 for several seconds through the brushes 16 and 23, and a pinion (not shown) connected to the rotating armature meshes with the ring gear to start the engine. The brush is gradually worn by this repeated start, and when a predetermined wear limit, in this example, 7.5 [mm] is reached, the pressing force is reduced by the brush springs 20 and 25 and the brush can move in the direction of the commutator. Since the dimensions are restricted by the structure of the brush holding frames 14 and 21, the brush holding frames 14 and 21 cannot be used.

By the way, in order to grasp the progress of wear due to repeated use of the brushes 16 and 23, 12 [V] and 1.2 [k]
w) was mounted on an engine with a displacement of 1600 [cc], and a repeated test of tens of thousands of cycles was performed with driving for 2 seconds and resting for 15 seconds as one cycle, and the amount of wear of the brush after each cycle was measured. .

At this time, the current flowing through the brushes 16 and 23 has a peak current of about 500 [A] and an average current of about 150 [A] in each cycle as shown in FIG. FIG. 6 shows the test results performed as described above. In FIG. 6, A shows the progress of wear of the positive brush 16 and B shows the progress of wear of the negative brush 23. The wear amount of the positive brush 16 is large, and the brush wear limit (7.5
[Mm]), while the wear amount of the negative electrode brush 23 is as small as about 4 [mm], and it can be seen that the brush 23 can withstand 10,000 or more cycles.

[0013]

Conventionally, there has been the above relationship between the copper content of the brush, the number of brushes, and the brush wear in the starter motor. However, the starter motor for mass production is required to be standardized. The same brush material is generally used for both the positive electrode side and the negative electrode side. However,
When brushes with a high copper content are used and the number of brushes is reduced from the viewpoint of high output and cost reduction, the brush on the positive side reaches the wear limit first and the brush on the negative side wears out from the above-mentioned relationship. In spite of the fact that a sufficient amount of wear is still left to the limit, there is a problem that the function of the starter motor is not fulfilled at the end of the service life. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain a brush device for a starter motor having high output and high durability.

[0014]

According to the present invention, there is provided a brush device for a starter motor having a brush in which the number of positive side brushes is twice the number of negative side brushes. And the copper content of the negative electrode side brush is 50 to 55% by weight, and the copper content of the positive electrode side brush is about 60% by weight.

[0015]

The brush of the brush device for the starter motor is used at a relatively high current density and is preferably a metallic graphite having a copper content of about 50 to 80% by weight from the viewpoint of abrasion resistance. The greater the amount, the faster the wear rate and the greater the difference depending on the polarity used. The brush device for a starter motor according to the present invention is a metallic graphite brush having a high copper content by eliminating the difference in polarity of brush wear by using brushes having different copper contents on the positive electrode side and the negative electrode side. However, the brush can be used on both the positive electrode side and the negative electrode side without waste up to the wear limit of the brush.

That is, when the number of the positive brushes is twice the number of the negative brushes, the copper content of the negative brush is 5 times.
By setting the copper content of the brush on the positive electrode side to about 60% by weight, the wear resistance of the brush on the negative electrode side is improved, and the wear of the brush proceeds on both sides to the same extent.

[0017]

【Example】

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 1 is a plan view of a brush device showing an embodiment of the present invention. In this embodiment, two positive brushes and one negative brush are used. In FIG. 1, reference numeral 30 denotes a brush device, which is configured as follows. The positive electrode side brush 16 has a copper content of 60% by weight, graphite 3
2% by weight and other 8% by weight.
As shown in the figure, two elements having the same configuration are provided up and down symmetrically with respect to the horizontal center line in the figure, and both are connected to the connection terminal 18 via the lead wire 17.
In this case, the current per brush on the positive electrode side 16 is as shown in FIG.
Is １ ／ of that shown in FIG.

Reference numeral 31 denotes a negative electrode side brush provided on the negative electrode side, which has a copper (copper powder) content of 52% by weight and natural graphite 4
0% by weight and other 8% by weight. Other configurations are the same as those of the conventional configuration shown in FIGS. 3 and 4, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.

The brush device 30 having such two brushes on the positive electrode side and one brush on the negative electrode side outputs an output of 1.2 [kw].
Was mounted on an engine of 1600 [cc], and a 2-second drive and a 15-second pause were defined as one cycle, and the brush wear after each cycle was compared. The results are shown in FIG. In FIG. 2, E is a line indicating the progress of wear of each positive brush 16, and F is a progress of wear of the negative brush 31. As is clear from FIG. 3, the reduction in the current per brush on the positive electrode side brush 16 and the improvement in the wear resistance due to the low copper content of the negative electrode side brush 31 are combined with each other. It can be seen that the abrasion speeds of the brushes are almost the same on both sides and that the brushes can be used more than 30,000 times.

Also in the first embodiment, if necessary, the copper content of the positive electrode brush 16 is slightly changed around 60% by weight, and the copper content of the negative electrode brush 31 is selected in the range of about 50 to 55% by weight. Even if it does, the same effect is exerted.

As described above, according to the first embodiment of the present invention, it is possible to cope with a starter motor having a large current by using a brush of the same size, and only one type of brush holding frame is required. The number of parts can be further reduced, and a brush having the most suitable component can be used in combination with a starter motor over a wide current range. In the metallic graphite brush, artificial graphite may be used as the graphite.

[0022]

As described above, according to the present invention, in a brush device for a starter motor provided with brushes in which the number of front brushes is twice the number of negative brushes, each brush contains copper. Since it was made of metallic graphite, the copper content of the negative electrode side brush was 50 to 55% by weight, and the copper content of the positive electrode side brush was about 60% by weight.
The speed of wear of the brushes on the positive electrode side and the negative electrode side can be made substantially the same, and the durability of the brush can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a brush device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a comparison result of a brush wear state in an engine start test of a starter motor equipped with the brush device shown in FIG. 1 of the present invention.

FIG. 3 is a plan view showing a conventional brush device.

FIG. 4 is a side view showing a part of a starter motor on which a conventional brush device is mounted.

FIG. 5 is a characteristic diagram showing a current flowing through a starter motor in one cycle of a test.

FIG. 6 is a characteristic diagram showing a comparison result of a brush wear state in an engine start test of a starter motor equipped with a conventional brush device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 starter motor 6 rotating armature 8 commutator 14 brush holding frame on positive electrode side 16 brush on positive electrode side (copper content 60% by weight) 21 brush holding frame on negative electrode side 30 brush device 31 negative electrode side brush (copper content 52% by weight) )

Claims (1)

(57) [Claims] 1. A brush device for a starter motor having a brush in which the number of positive brushes in sliding contact with a commutator of a starter motor is twice the number of negative brushes,
Each of the above brushes is made of metallic graphite containing copper,
50-55 weight percent copper content of the negative electrode side brush,
A brush device for a starter motor, wherein the copper content of the brush on the positive electrode side is about 60% by weight.