JP2770866B2 - Electromagnetic spring clutch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved technology of an electromagnetic spring clutch, in particular, an electromagnetic spring clutch for transmitting a torque by utilizing the tightening of a coil spring.

[0002]

2. Description of the Related Art An electromagnetic spring clutch of this kind is disclosed, for example, in Japanese Patent Publication No.
No. 7522, for example. A general configuration includes a first wheel on the input side arranged on the axis, a movable sleeve, a field core, a second wheel on the output side, and the like. Each body of the first wheel and the second wheel is coiled. The torque is transmitted from the input side to the output side by being tightened by a helical spring. The spring locks one end of each of the first wheel and the movable sleeve, and the movable sleeve is attracted to the field core, which is excited by energization, so that the body of the first wheel and the body of the second wheel are moved. At the same time, when the excitation of the field core is released, the winding is released and the clutch is disconnected.

[0003]

By the way, the movable sleeve is attracted and moved by exciting the field core. In this movement, since the transmission shaft and the second wheel are made of metal, the sleeve of the field core is made of metal. The sliding portions of the portion, the transmission shaft, and the end surface of the bearing cylinder portion of the field core and the end surface of the second wheel are also sucked. For this reason, a rotational torque loss occurred, and the sliding contact surfaces of the respective sliding portions were liable to be abnormally worn. Conventionally, as a measure against this, a fluororesin is applied to the sliding surface of the field core, or a bush with a flange portion made of a non-magnetic material such as bronze (a bush may be coated with a fluororesin film or the like). Is pressed into the bearing cylinder of the field core to alleviate the suction and make it hard to wear, so that the slidability is not impaired. However, in the case of using only the fluororesin film, the wear of the field core end face of the field core having a large attraction force is particularly fast, and the initial characteristics cannot be maintained for a long time. Further, in the case of the bush with the flange portion, there is an effect of obstructing the circuit of the magnetic force, and the attraction force to the movable sleeve is easily reduced. Therefore, the magnetic force of the field core must be increased in anticipation thereof.

Accordingly, the present invention has been made to solve the above-mentioned problems, and provides an electromagnetic spring clutch capable of minimizing the loss of rotational torque, reducing sliding wear and maintaining initial characteristics for a long period of time. The purpose is to do.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is to dispose a first wheel, a second wheel, and a field core on a transmission axis in order,
The field core has a movable sleeve that can be attracted and moved toward the field core by being energized and energized, and the movable sleeve moves to the body of the first wheel and the body of the second wheel when moving to the field core. In an electromagnetic spring clutch in which power is transmitted or interrupted by winding or separating a spring, a plurality of thrust washers are rotatably provided between an end surface of the second wheel and an end surface of a bearing cylinder of a field core. The gist is that In addition, in the above configuration, a bush with an iron flange portion is mounted on the bearing cylinder portion of the field core, and the plurality of thrust washers are rotatably provided between the end surface of the flange portion and the end surface of the second wheel. It may be provided.

Here, the thrust washer is made of ethylene tetrafluoride resin, polyamide resin, polyethylene resin,
Any one of the materials of polyacetal resin is a base, and various synthetic resin sheets and steels, including a resin composite material in which dispersion strengthening material such as glass fiber or solid lubricant particles such as graphite are dispersed in the base. A sheet made of a material can be used. In particular, when the graphite particles are dispersed and the sheet made of tetrafluoroethylene resin having improved solid lubricating action and elastic modulus is arranged at least in a portion in contact with the end face of the second wheel, the ethylene tetrafluoride resin is in an initial stage of operation. Transfer to the mating member improves both friction and wear. On the other hand, since the area of the end surface of the bearing cylinder portion of the field core is smaller than that of the end surface of the second wheel, the surface pressure applied to the thrust washer is high, and deformation and wear are likely to occur. Therefore, it is desirable that the thrust washer that is in sliding contact with the end surface of the bearing cylinder portion of the field core be made of a material having appropriate hardness and wear resistance, such as a polyamide resin containing glass fiber or graphite particles. Another means is to provide a tetrafluoroethylene resin coating on the end surface of the bearing cylinder part of the field core and use rigid steel for the thrust washer that slides on it. The durability can be improved. In this case, the steel washer is slightly thicker, and preferably has a thickness of 0.3 to 1 mm. If it is too thin, it will be easily deformed by being pushed by the end surface of the bearing cylinder of the field core, so a high surface pressure will be transmitted to the adjacent thrust washer to accelerate the wear, and if it is too thick, the device will become large. Similarly, instead of using a steel washer, a bush made of iron and having a flange on the second wheel side is mounted on the bearing cylinder of the field core.

Further, it has been found that a combination of adjacent sheet materials mainly having a low dynamic friction coefficient gives a good result. The specific combination is as follows. (1) Examples of the same material include ethylene tetrafluoride resin and polyamide resin. (2) Examples of the material that can be used between steels include ethylene tetrafluoride resin, polyamide resin, polyethylene resin, and polyacetal resin. (3) Examples of good materials between tetrafluoroethylene resins include ethylene tetrafluoride resin, polyamide resin, acrylonitrile butadiene / styrene resin, steel, polyacetal resin, polycarbonate resin, and urea resin. (4) Examples of good materials between polyamide resins include ethylene tetrafluoride resin, polyamide resin, and polyethylene resin. (5) Examples of good materials between polyethylene resins include ethylene tetrafluoride resin, polyamide resin, urea resin, polyacetal resin, and polycarbonate resin. (6) Examples of good materials between polyacetal resins include ethylene tetrafluoride resin, polyamide resin, and polyethylene resin. (7) Unsuitable materials among the same materials include acrylic resin, styrene resin, polycarbonate resin, phenol resin, polypropylene resin, polyvinyl chloride resin, steel and the like. (8) Steel, styrene resin, acrylonitrile butadiene styrene resin,
Urea resin and the like can be mentioned. The dynamic friction coefficient between the materials differs depending on the measurement conditions, but the tendency of the height is shown in Table 16.3, “Plastic Mechanical Properties”, published by Nikkan Kogyo Shimbun and written by Kosaburo Yamada. FIG.
3, the same as FIGS. 16 and 14, and FIGS.

[0008]

According to the electromagnetic spring clutch, when the field core is excited by energization, the movable sleeve is attracted to the field core and the field core is also attracted to the second wheel. At this time, since the thrust washer is rotatably provided between the end face of the bearing cylinder portion of the field core and the end face of the second wheel, the thrust washer slides between each end face and the thrust washer, and a small amount of wear occurs. Smooth rotation is ensured by the coefficient. The thrust washer may be mounted on the bearing barrel of the field core by mounting a bush with a flange facing the second wheel end face or by forming a steel thrust washer in sliding contact with the bearing face of the field core. Since such surface pressure is reduced, wear is reduced and a long life is ensured.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electromagnetic spring clutch to which the present invention is applied, and FIG. 2 is an enlarged view of a portion A in FIG. The electromagnetic spring clutch shown in FIG. 1 has a drive shaft 2 serving as a first wheel, a driven wheel 3 serving as a second wheel, and a field core 4 arranged in series on a transmission shaft 1, and the drive wheel 2 and the driven wheel 3 are connected to each other. The connection and disconnection are performed by a common coil spring 5. The drive wheel 2 is provided with a gear 6 meshing with a transmission gear (not shown) on the outer periphery, and a cylindrical body 7 is integrally formed on a right end face thereof. It is assembled. A support portion 8 having a larger diameter is provided at a protruding base portion of the body portion 7, and an engagement hole 7 a is provided at a portion adjacent to the support portion 8. The driven wheel 3 has a regulating portion 10 having a diameter larger by one step on the right side of the body portion 9 having the same diameter as the body portion 7.
And is fixed by a through pin 11. The end surface of the regulating portion 10 on the side of the trunk 9 forms a vertical surface, and a portion protruding from the support member 12 attached around the base of the trunk 9 functions as a stopper surface 10a for the movable sleep 13. The support member 12 is formed of a nonmagnetic material such as a hard resin into a ring shape having an outer diameter that fits with the movable sleeve 13, and supports the movable sleeve 13 together with the support 8. The movable sleeve 13 includes the stopper surface 10a and the drive wheel 2
The length is set to be slightly shorter than the dimension between the side stopper surface 2a and a flange portion 14 having a larger diameter at one end provided at the end located on the driven wheel 3 side. An engagement hole 14a is provided in the inner surface of the flange portion 14. Then, assembling, after the spring 5 is inserted into the outer periphery of the body portions 7 and 9, one end 5a of the spring 5 is locked in the engagement hole 7a, and the other end 5b is locked in the engagement hole 14a. And the supporting member 1
2 and the supporting portion 8 so as to be movable. In the supported state, the movable sleeve 13 hits the stopper surface 2a of the drive wheel 2 to restrict the movement in the coaxial direction. Conversely, when the field core 4 is excited by electric conduction, it is sucked and moved until it hits the stopper surface 10a. The field core 4 has an electromagnetic coil 16 provided in a yoke 15. The yoke 15 has a bearing cylinder 15 a and a storage section 15 b having a substantially U-shaped cross section located outside the bearing cylinder 15 a. , And is fixed by a locking member 17 or the like so as not to rotate normally. The storage portion 15b is defined by an upper horizontal portion 18a, a lower horizontal portion 18b shorter than the upper horizontal portion 18a, and an intermediate vertical portion 18c so that the coil 16 does not protrude from the lower horizontal portion 18b. It is stored. Bearing tube part 15a (lower horizontal part 18b)
Is lined with an ethylene tetrafluoride resin (hereinafter, referred to as PTFE), and the PTFE film 19 prevents wear on the sliding contact surface.

In the assembled state, the end surface of the upper horizontal portion 18a is located slightly to the right in the drawing with respect to the stopper surface 10a in this embodiment, and between the end surface of the bearing cylinder 15a and the end surface 10b of the regulating portion 10. A gap is formed in the gap, and two thrust washers 20 are rotatably arranged in the gap. The thrust washer 20 is formed of a relatively hard resin material, and has a sheet shape with a thickness of about 0.13 mm.

In the above-described electromagnetic spring clutch, when the clutch is disconnected, the driven wheel 3 and the transmission shaft 1 are stopped. When the coil 16 is energized, the field core 4
Is excited, and the movable sleeve 13 is attracted. At this time, since the support member 12 is made of a non-magnetic material, the movable sleeve 13 is smoothly sucked and moved without being hindered from moving toward the field core 4. This allows
The spring 5 in the expanded state reduces the diameter of each body 7,
The drive wheel 2 and the driven wheel 3 are brought into a connected state by this tightening, and a clutch contact state for transmitting torque to the transmission shaft 1 is established. When the energization of the coil 16 is stopped, the excitation of the field core 4 is released, the diameter of the spring 5 is expanded to the original state, and the clutch is released, in which torque transmission is released. In the above-mentioned clutch contact state, the end face of the lower horizontal portion 18b of the field core 4 is also attracted to the end face 10b of the driven wheel 3, but since the thrust washer 20 is provided between the two, the sliding of the driven wheel 3 Sex can be done smoothly.

By the way, in this case, the thrust washer 2
According to the operation test when the number of used 0 was changed, the following tendency was found. Although a single device has a certain effect, the larger the number of used devices is two, three, or four, the smaller the increase in the coefficient of friction due to long-term operation, and the better. When the number of the thrust washers is four or more, the thrust washer 20 has a thickness of about the above-mentioned thickness, although the effect is not reduced for the cost and the suction force to the movable sleeve 13 is reduced. In this case, it is preferable to configure two to four. Further, when the number is two or more, different materials such as a filled polyamide resin (hereinafter referred to as 6 nylon) and a filled PTFE material are combined with each other, and the same material is used for the field core 4 side. It is preferable to arrange a relatively hard material.

Further, as a result of friction and wear tests and mounting tests using a pin-on-disk using various materials, as shown in the above paragraph 008, there is a compatibility between the materials, and a combination having a low dynamic friction coefficient without much consideration of the static friction coefficient. When a hard and wear-resistant material is arranged on the field core 4 side, it has been found that the torque between the field core 4 and the driven wheel 3 as the second wheel lasts for a long time in a low state. As a specific material, for example, a thrust washer in which graphite particles are dispersed in a 6-nylon base material having appropriate hardness is arranged on the field core 4 side coated with PTFE, while the PTFE is coated on the second wheel side. A thrust washer having graphite particles dispersed therein is disposed in a substrate.

FIG. 3 shows an example in which a part of the configuration is modified. That is, the difference from the above-described embodiment is that the PTFE is provided on the inner surface of the bearing cylinder 15a of the field core 4.
That is, the bush 22 provided with the coating 21 was press-fitted.
The bush 22 is made of iron, and has a flange portion 23 protruding from an end surface of the bearing tube portion 15a. Further, two thrust washers 24 are enlarged in diameter in accordance with the size of the area of the flange portion 23. In this case, a PTFE coating may be provided on the end surface of the flange portion 23. With this configuration, the surface pressure applied to the thrust washer 24 is reduced by the increase in the area due to the flange portion 23, and the life can be further extended. As another means for obtaining the same operation and effect as in FIG. 3, a PTFE coating is provided on the end face of the bearing cylinder 15a in FIG. 2 without using the bush 22 described above, and the end face of the bearing cylinder 15a is provided on the end face. The contacting thrust washer is made of slightly thicker steel. According to this configuration, the bush 2
Not using 2 is advantageous in terms of cost and miniaturization.

FIG. 4 shows the results of a durability test using the electromagnetic spring clutch having the structure shown in FIG. 1 and changing the combination of thrust washers. This endurance test was conducted at an input rotation speed of 300 rpm and a load torque of 1.5 kgf-c.
The rotational torque between the clutch body and the field core when the field core was excited every predetermined number of times was measured by repeatedly connecting and releasing the clutch under the conditions of m and an inertial load of 0.2 kgf-cm. Here, Sample 1 and Sample 2 are comparative examples not using a conventional thrust washer. Sample 1 has an end surface of the bearing cylinder 15a also having a metal surface, and Sample 2 has PTFE on the end of the bearing cylinder 15a. It is provided with a coating. Samples 3 to 10 are examples of the present invention, in which a thrust washer was provided and a PTFE coating was provided on the end surface of the bearing cylinder 15a. Of these, samples 3 to 6 were made by changing the number of sheets used by using a thrust washer made of 6 nylon material containing graphite particles. One sample was used for sample 3, two samples for sample 4, and five samples for sample 5. Three samples and four samples 6 are used. Samples 7 and 8 use a thrust washer made of a PTFE material containing graphite particles, sample 7 uses one thrust washer, and sample 8 uses two thrust washers. Sample 9 has a steel core thrust washer on the field core 4 side and a graphite thrust washer dispersed on the second wheel side. The sample 10 has a thrust washer made of 6 nylon containing graphite particles on the field core 4 side and a thrust washer made of PTFE containing graphite particles on the second wheel side.

In FIG. 4, the vertical axis represents torque. If the torque is low, it indicates that the friction between the field core 4 and the second wheel is small, so that the power loss during use is small, and the damage due to friction is small. This indicates that the service life will be long. Further, when the torque exceeds 120 gf-cm, the increase in the torque becomes large, wear of the sliding portion is recognized, and it can be said that the life is over. The following can be understood from the above durability test. Sample 1 was in metal contact and exhibited a torque exceeding 200 gf-cm from the beginning of operation. On the other hand, Sample 2 was PTFE in the initial stage.
Although the effect of the coating appears and the torque is relatively low, the PTFE coating gradually wears out and the torque rapidly increases at about 100,000 times. On the other hand, in the present invention, it can be seen that the life of samples 3 to 6 is prolonged in proportion to the number of thrust washers used. In this case, the portion that slides the most was the portion that is in contact with the end surface of the driven wheel 3 that is the second wheel.
Samples 7 and 8 are slightly inferior to the same number of Samples 3 and 4. This indicates that PTFE is softer than nylon 6 and is liable to deform and wear, resulting in a slightly shorter life. However, in the case of both samples, PTFE of the thrust washer was partially transferred and adhered to the end surface of the second wheel, and the initial characteristics showed low torque.
In Sample 9, although the initial characteristics are relatively high, the surface pressure applied to the resin thrust washer is reduced by the rigidity of the steel, and the life is extended. Although illustration is omitted, when the thrust washer made of PTFE material containing graphite particles is used under the same conditions instead of the above-mentioned 6 nylon material containing graphite particles, the sliding on the second wheel side is performed. Is good,
The life was about the same as that of Sample 8. The life of sample 10 has not reached even 4 million times. This is Field Core 4
PTFE coating on the end surface of the bearing cylinder, and a thrust washer made of a material that is abrasion-resistant, stiff, and compatible with PTFE is placed on the field core 4 side, and transfers to metal on the second wheel side. This indicates that it is preferable to dispose a thrust washer made of a PTFE-based material that is easy to use. As described above, as apparent from the samples 3 to 10 used in the durability test, the initial characteristics of each of the samples 1 and 2 were 50.
The torque can be reduced to about fg-cm, and the life can be maintained long. Moreover, among the samples 3 to 10, the samples 4, 5,
In the case of 6, 8, 9, and 10, the life can be maintained about 1,000,000 times longer than that of the samples 3 and 7 using one thrust washer, and it is more preferable to use a plurality of thrust washers. In addition, it has been found that, in particular, the life of sample 10 does not reach its life even at 4 million times, and stable operation can be ensured over a long period of use.

In this embodiment, the electromagnetic spring clutch in which the coil spring comes into contact with the clutch by the suction movement of the movable sleeve has been described. However, in the present invention, the coil spring winds the drive wheel side and the driven wheel side. The present invention can be similarly applied to an electromagnetic spring clutch which is assembled in a state where the clutch is in contact with the clutch and the clutch is disconnected by the suction movement of the movable sleeve.

[0018]

As described above, in the electromagnetic spring clutch according to the present invention, a plurality of slide washers are provided between the end face of the second wheel (driven wheel) and the end face of the bearing cylinder of the field core. Since mutual attraction is prevented and wear caused by local strong frictional force is eliminated, rotational torque loss can be minimized, and initial characteristics can be maintained for a long time. As a result, in the present invention, more stable operation is ensured over a long period of use, and quality and reliability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electromagnetic spring clutch shown as an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of part A of FIG. 1;

FIG. 3 is an enlarged sectional view of a main part of an electromagnetic spring clutch showing another example of the present invention.

FIG. 4 is a graph showing changes in the number of times of disconnection and the friction torque of a field core in a repeated disconnection test of an electromagnetic spring clutch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmission shaft 2 Drive wheel (1st wheel) 3 Follower wheel (2nd wheel) 4 Field core 5 Spring 7,9 Body 20 and 24 Thrust washer 15a Bearing cylinder

Claims (7)

(57) [Claims] A first sleeve, a second wheel, and a field core are sequentially arranged adjacent to each other on a transmission axis, and a movable sleeve that can be attracted and moved toward the field core by energizing the field core is provided. An electromagnetic spring clutch, wherein the movable sleeve transmits or cuts off power by a spring being wound around or separated from the body of the first wheel and the body of the second wheel when the movable sleeve moves toward the field core. An electromagnetic spring clutch, wherein a plurality of thrust washers are rotatably provided between an end face of the second wheel and an end face of a bearing cylinder of a field core. 2. A bush with an iron flange portion is mounted on a bearing cylinder portion of the field core, and the plurality of thrust washers are rotatable between an end surface of the flange portion of the bush and an end surface of the second wheel. The electromagnetic spring clutch according to claim 1, wherein 3. The electromagnetic spring clutch according to claim 1, wherein a coating mainly composed of ethylene tetrafluoride resin is provided on one or both of the end face of the second wheel and the end face of the bearing cylinder of the field core. . 4. The electromagnetic spring clutch according to claim 2, wherein a coating mainly composed of ethylene tetrafluoride resin is provided on one or both of an end surface of the second wheel and an end surface of a flange portion of the bush. 5. The thrust washer is made of ethylene tetrafluoride resin, polyamide resin, polyethylene resin, polyacetal resin, polycarbonate resin, acrylonitrile butadiene / styrene resin, polypropylene resin, phenol resin, styrene resin, acrylic resin, polyvinyl chloride. The electromagnetic spring clutch according to any one of claims 1 to 4, wherein the electromagnetic spring clutch is made of any one of resin, urea resin, melamine resin, and steel. 6. The thrust washer contains a fibrous or granular filler, and the filler is at least one of glass, carbon or graphite, potassium titanate, molybdenum disulfide, boron nitride, talc, and cellulose. The electromagnetic spring clutch according to any one of claims 1 to 5, which is one type. 7. A coating mainly composed of ethylene tetrafluoride resin is provided on an end surface of a bearing cylinder portion of the field core or an end surface of a flange portion of the bush, and the thrust washer which is in sliding contact with the coating surface is steel. Item 7. An electromagnetic spring clutch according to any one of Items 1 to 6.