JPH05321943A - Overload protective device - Google Patents

Abstract

PURPOSE:To transmit low torque to high torque by applying a torque transmission coil spring tightly on the same circumferential surface of an inner circumference or an outer circumference of a drive shaft and a follower shaft, and idly rotating the drive shaft when overload of more than transmitted torque is generated at the follower shaft. CONSTITUTION:A drive shaft 2 is rotated in winding direction or rewinding direction of a torque transmission coil spring 4 by power, and rotation torque is transmitted through the coil spring 4 to a follower shaft 3. The coil spring 4 is tightly applied on the same circumferential surface of an inner circumference or an outer circumference of the drive shaft 2 and the follower shaft 3, and when the drive shaft 2 rotates in such a direction as to increase friction force of the coil spring, high torque can be transmitted. When overload exceeding the transmitted torque of the coil spring 4 is generated at a driven member, the coil spring 4 tightly in contact with one of the drive shaft 2 and the follower shaft 3 slides relative to the shaft, thereby transmission of the overload to the drive shaft 2 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload preventing device which prevents an overload of a driven member which is rotationally driven by power from being transmitted to a power source side.

[0002]

2. Description of the Related Art In a rotating mechanism of various machines, when an overload is generated on a rotating shaft, if this overload is transmitted to the power source side, the power source side is heated and damaged, causing a failure. Therefore, various overload prevention devices have been conventionally developed to prevent overload on the rotating shaft.

A first conventional overload preventing device is a disk-shaped first cam directly connected to a driven shaft, and a spring which is engaged with a stopper of a drive shaft to the first cam via a friction plate. It comprises a disk-shaped second cam that is pressed, and a switch that slides on the outer circumferences of the second cam and the first cam, and protrusions are formed on the outer circumferences of the first cam and the second cam, respectively. The concave portion and the convex portion are always provided so that the concave portion and the convex portion are aligned with each other so that the switch is actuated by an arbitrary fluctuation of the cam at the time of overload (Japanese Utility Model Laid-Open No. 57-183641).

The second conventional overload prevention device is provided between a pair of driving member and a driven member, which constitute a transmission system of a motor antenna and rotate concentrically to transmit power, This is an overload prevention clutch for a motor antenna that shuts off power transmission when under load (Japanese Utility Model Laid-Open No. 62-125007). This one is provided with an engaging member that rotates integrally with the drive member, and a leaf spring that surrounds the engaging member and is attached to the operating member, and the leaf spring has an intermediate portion within the rotational locus of the engaging member. Face and engage with the engaging member by elastic contact,
When it is overloaded, it elastically deforms while slidingly contacting the engaging member to release the engaged state.

Further, in a third conventional overload preventing device, a drive key which is rotatable on an axial rotary shaft around the peripheral edge of a hub is supported by abutting support by spring slides pressed by torque springs from both sides in the circumferential direction. Then, the drive key head is engaged with the key groove of the housing part to synchronize the rotation of the housing part and the hub part, and when the load is overloaded, the drive key is disengaged from the key groove and the transmission of the overload is blocked. (Jpn. Pat. Appln. KOKAI No. 58-108629).

Further, FIG. 8 shows a fourth conventional overload preventing device 100. This device 100 is arranged with a first rotating body 101 having an inner cylindrical portion 101a having an inner diameter D, and an outer peripheral surface having an outer diameter D3 which is rotatably and coaxially opposed to the first rotating body 101. The second rotating body 102 having 102a and one end having an outer diameter D1 (> D) in the free state are press-fitted into the inner cylindrical portion 101a of the first rotating body 101, and the other end having the inner diameter D2 (<D3) in the free state. The second rotating body 1
No. 02 and a coil spring 103 press-fitted to the outer peripheral surface 102a (Japanese Utility Model Publication No. 63-53062). The device 100 includes rotating bodies 101 and 10
Which of the two transmits the forward / reverse rotation of one rotating body 101 (or 102) to the other rotating body 102 (or 101), and when an overload is applied, the coil spring 103 and any rotating body 101 or The rotating body of one of the rotating bodies 101 (or 102) slides with respect to the other rotating body 10
2 (or 101) is not transmitted.

[0007]

However, the above-mentioned conventional overload preventing device has various problems to be solved as follows. That is, since the first conventional overload preventing device transmits torque through the friction plate, the friction plate needs to have a large diameter in order to transmit high torque. In that case, the size is increased and the weight is increased. It is difficult to make it compact. In addition, this one requires two cams, a friction plate, and a spring for urging the cams, has a large number of parts, and is troublesome to assemble.

In the second conventional overload preventing device, the torque is transmitted from the driving member to the driven member by the engagement of the engaging member and the leaf spring by elastic contact. Torque is low and is not suitable for high torque transmission.

Further, a third conventional overload preventing device is a drive key, a torque spring, a spring slide,
Also, it has a complicated structure in which the housing portion provided with the key groove is combined, and the number of parts is large and the assembly is troublesome.

Still further, a fourth conventional overload prevention device 1
00 has one end of the coil spring 103 that transmits torque inserted into one of the rotating bodies and the other end of the coil spring 103 that extends outside the other rotating body. When it becomes larger with respect to the rotating body, it becomes smaller with respect to the other rotating body, so that only low torque can be transmitted.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a compact overload prevention device which is capable of transmitting low torque to high torque, has a small number of parts, and has a simple structure. It is in.

[0012]

In order to achieve the above-mentioned object, the present invention has a torque transmission coil spring wound in close contact with each other on the same inner peripheral surface or outer peripheral surface of a drive shaft and a driven shaft. When the driven shaft is overloaded more than the transmission torque of the coil spring, the spring portion of the coil spring that is in close contact with at least one of the two shafts slides relative to the shaft and the drive shaft idles. It is characterized by doing so.

The drive shaft and the driven shaft may be provided with protrusions for restricting axial movement of the torque transmitting coil spring.

A torque transmitting coil spring may be closely attached to a cylindrical connecting portion formed on at least one shaft portion where the drive shaft and the driven shaft are connected.

[0015]

The driving shaft rotates in the winding direction or the unwinding direction of the torque transmitting coil spring due to the power. This rotational torque is normally transmitted to the driven shaft via the torque transmission coil spring, and the driven member that is linked to the driven shaft is driven by the rotation of the driven shaft. At this time, the torque transmission coil spring is tightly wound around the same inner peripheral surface or outer peripheral surface of the drive shaft and the driven shaft, so that the drive shaft tends to increase the frictional force of the torque transmission coil spring. When rotating, the rotation direction becomes the direction of increasing frictional force with respect to the driven shaft as well, and high torque can be transmitted.

When an overload that exceeds the transmission torque of the torque transmission coil spring is generated in the driven member (the overload is generated in the driven shaft), the coil spring is in close contact with at least one of the drive shaft and the driven shaft. The spring portion of the shaft slides relative to the shaft, the torque transmission between the shafts is cut off, and the drive shaft idles. It is possible to prevent the overload generated in the driven member from being transmitted to the drive shaft side due to the interruption of the torque transmission between the both shafts.

The torque transmitting coil spring is prevented from moving in the axial direction by the projection, and stable transmission torque can be obtained without fluctuations in the number of coil turns for both shafts.

The torque transmitting coil spring is mounted in the cylindrical connecting portion formed on the shaft portion to prevent dust and
It is effectively protected from external requirements such as water and its operation is stable.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the illustrated embodiments. FIG. 1 shows an overload prevention device 1 as a first embodiment of the present invention. The overload prevention device 1 includes a drive shaft 2
And a driven shaft 3 and a torque transmission coil spring 4.

The drive shaft 2 has a cylindrical connecting portion 2 at the center of one end face.
The driven shaft 3 has the same outer diameter as that of the drive shaft 2, and is formed of a bottomed cylindrical body having a circular hole 3b formed in the bottom portion 3a. The drive shaft 2 and the driven shaft 3 are relatively rotatably connected by penetrating the connecting portion 2a into the circular hole 3b and fitting a snap ring 5 at the tip of the connecting portion 2a to prevent the connecting shaft 2a from coming off.

The drive shaft 2 is linked to a power source (not shown) through a connecting member 6 connected to the other side,
The driven shaft 3 is linked to a driven member (not shown) via a connecting member 7 connected to the opening side portion.

The torque transmitting coil spring 4 is tightly wound around the outer periphery of the drive shaft 2 and the driven shaft 3 connected in this manner with both ends being free ends. At this time, the coil spring 4 for torque transmission is in the free state, and the drive shaft 2 and the driven shaft 3 are free.
Is formed to have an inner diameter smaller than the outer diameter, and the diameter is expanded and externally inserted on the drive shaft 2 and the driven shaft 3. Therefore, the coil spring 4 for torque transmission after extrapolation is pressed against the drive shaft 2 and the driven shaft 3 with a sufficient tightening margin. The pressure contact force at this time is determined by the number of coil turns in the torque transmitting coil spring 4 formed with the same wire diameter and coil inner diameter.

In this embodiment, the number of coil turns is larger on the drive shaft 2 side than on the driven shaft 3, and the pressure contact force of the torque transmitting coil spring 4 is larger on the drive shaft 2 side than on the driven shaft 3. For this reason, the torque transmitted from the drive shaft 2 to the driven shaft 3 is controlled by the pressure contact force of the torque transmitting coil spring 4 on the side of the driven shaft 3, and when a load larger than this pressure contact force is generated in the driven shaft 3, the torque is transmitted. The portion of the coil spring 4 on the driven shaft 3 side slides with respect to the driven shaft 3, and the coil spring 4 idles together with the drive shaft 2.

Further, in FIG. 1, reference numerals 2b and 3c are protrusions formed on the outer peripheral surfaces of the drive shaft 2 and the driven shaft 3, respectively, and are located outside both ends of the coil spring 4 for torque transmission. Is prevented from moving in the axial direction.
By preventing the coil spring 4 from moving in the axial direction, the transmitted torque can be made constant.

The overload prevention device 1 operates as follows. The drive shaft 2 is a coil spring 4 for torque transmission by a power source.
When it is rotated in the winding direction, the rotation torque is always transmitted to the driven shaft 3 via the coil spring 4, the driven shaft 3 rotates in the same direction at the same rotation speed, and the driven member (via the connecting member 7). (Not shown) is driven.

When the driven member is overloaded more than the transmission torque during the driving of the driven member, the driven shaft 3 side portion of the torque transmission coil spring 4 slides with respect to the driven shaft 3 to transmit the torque. Is cut off, and the drive shaft 2 idles. The overload generated on the driven member due to the idling is not transmitted to the power source side, and the failure on the power source side due to the overload is prevented in advance.

2 and 3 show an overload prevention device 10 as a second embodiment of the present invention. The device 10 is different from the device 1 only in that the torque transmission coil spring 4 is mounted by engaging the end 4a on the drive shaft 2 side with a groove 2c formed in the drive shaft 2 in the axial direction. .. Therefore, the same elements as those of the device 1 are designated by the same reference numerals and the description thereof will be omitted.

According to this apparatus 10, the coil spring 4 for torque transmission always rotates integrally with the drive shaft 2, and the magnitude of the torque transmitted from the drive shaft 2 to the driven shaft 3 depends on the driven shaft 3 of the coil spring 4. It is controlled by the pressure contact force of the side part. This control is not affected by the number of coil windings of the portion of the spring 4 on the drive shaft 2 side, so that the number of coil windings of the portion can be reduced to achieve a more compact design.

This device 10 operates in the same manner as the device 1 described above, and the driven shaft 3 of the coil spring 4 for torque transmission is applied to the driven member.
When an overload exceeding the pressure contact force of the side portion occurs, the drive shaft 2 idles together with the coil spring 4 so as not to transmit the overload to the power source side.

FIG. 4 shows an overload prevention device 20 according to the third embodiment of the present invention. This device 20 is mounted so that the torque transmission coil spring 4 is pressed against the drive shaft 2 and the driven shaft 3 from the inside. In the drive shaft 2, a connecting portion 21 with the driven shaft 3 is formed in a large-diameter cylindrical shape, and a core shaft 22 is provided at a central portion of the connecting portion 21 so as to extend in the axial direction. The open end of the connecting portion 21 has a large inner diameter and is formed in a step portion 21a, and the tip end of the core shaft 22 is formed in a small diameter shaft portion 22a.

The driven shaft 3 is formed in a cylindrical shape in which the connecting portion 31 with the drive shaft 2 has the same inner and outer diameters as the connecting portion 21, and has a bearing hole having a hole diameter substantially the same as the outer diameter of the small diameter shaft portion 22a at the bottom thereof. 31b is provided. A step portion 31a is formed at the opening end of the connecting portion 31 with a small outer diameter.
The drive shaft 2 and the driven shaft 3 are connected to each other 2
The stepped portions 21a and 31a of 1 and 31 are meshed with each other, and the small diameter shaft portion 22a of the core shaft 22 is inserted into the bearing hole 31b and rotatably connected to each other.

The torque transmitting coil spring 4 is attached to the inside of the connecting portions 21 and 31 in the above-mentioned connected state with both ends free. The coil spring 4 for torque transmission is wound and formed so that the outer diameter in the free state is larger than the inner diameter of the connecting portions 21 and 31, and the diameter is reduced and inserted into the connecting portions 21 and 31. Therefore, the torque transmitting coil spring 4 after the insertion is attached to the inner walls of the connecting portions 21 and 31 by pressing.

Overload prevention device 2 having such a structure
In 0, the drive shaft 2 is rotated in a direction in which the coil diameter of the torque transmission coil spring 4 is expanded, so that the rotation is transmitted to the driven shaft 3 side. At this time, when an overload exceeding the transmission torque occurs on the driven shaft 3 side, the drive shaft 2 slides against the coil spring 4 and runs idle, so that the overload is not transmitted to the drive shaft 2 side. There is.

5 and 6 show overload prevention devices 30 and 40 as the fourth and fifth embodiments, respectively. The overload prevention devices 30 and 40 are of the inscribed type like the overload prevention device 20 described above. In the overload prevention devices 30 and 40, the coil spring 4 for torque transmission is attached so that the coil portion thereof presses only the inner wall of the connecting portion 31 of the driven shaft 3. Therefore, the connecting portion on the side of the drive shaft 2 is not formed in a cylindrical shape, but is connected to the core shaft 22 and the connecting portion 31.
And a flange portion 23 that closes the opening of the.

Here, one end 4a of the torque transmitting coil spring 4 is locked to the core shaft 22 or the flange portion 23,
Each constitutes an overload prevention device 30 or 40. In the overload preventing devices 30 and 40, when an overload exceeding the transmission torque occurs on the driven shaft 3 side, the torque transmission coil spring 4 slides on the connecting portion 31 of the driven shaft 3 and idles with the drive shaft 2. .. An overload generated on the driven shaft 3 side due to this idling is not transmitted to the drive shaft 2 side. The torque transmission in the overload prevention devices 30 and 40 is performed in the same manner as the above-described overload prevention device 20.

FIG. 7 shows an overload prevention device 50 as a sixth embodiment. The overload prevention device 50 is the same as the overload prevention device 30 of FIG. 5 described above except that an oil seal 51 is incorporated between the flange portion 23 of the drive shaft 2 and the opening of the connecting portion 31 of the driven shaft 3. With the structure, the torque transmission and the interruption of the torque transmission at the time of overload can be obtained similarly to the overload prevention device 30. This overload prevention device 50 has a structure in which the degree of sealing of the opening of the connecting portion 31 is enhanced,
Lubricating oil or the like can be enclosed in the connecting portion 31 for stable operation and improved wear resistance.

These inscribed type overload prevention devices 20,
In 30 and 40, the torque transmission coil spring 4 is mounted in the connecting portion 31 (and 21), so that it is sufficiently protected from external requirements such as dust and water, and its axial movement. Since it is possible to prevent even without providing a special protrusion, it is possible to ensure stable operation.

The present invention is not limited to the above-described embodiments, but various modifications such as the following can be considered. In the overload prevention device 1, the torque transmission coil spring 4 may have a larger number of coil turns on the driven shaft 3 side than on the drive shaft 2 side.
In this case, the torque transmitted from the drive shaft 2 to the driven shaft 3 is controlled by the pressure contact force of the coil spring 4 on the drive shaft 2 side, and when an overload exceeding the pressure contact force is generated in the driven member, only the drive shaft 2 is driven. When the idling coil spring 4 stops integrally with the driven shaft 3, the transmission of the overload to the power source side is cut off.

In the overload prevention device 10, the torque transmission coil spring 4 may have the end 4a on the drive shaft 2 side as a free end and the end on the driven shaft 3 side engaged with the driven shaft 3.
In this case, when the driven member is overloaded, the drive shaft 2 slides with respect to the torque transmission coil spring 4 to idle, and the coil spring 4 stops integrally with the driven shaft 3.

Further, the overload prevention devices 1, 10, 20, 3
At 0 and 40, grease may be applied between the torque transmission coil spring 4 and the drive shaft 2 and the driven shaft 3. The application of this grease stabilizes the operation and prevents the generation of abnormal noise during the operation.

[0041]

As described above, according to the present invention, since the torque transmitting coil spring is closely wound on the same inner peripheral surface or outer peripheral surface of the drive shaft and the driven shaft, the drive shaft Also, the transmission torque can be easily designed from low torque to high torque by adjusting the pressure contact force of the torque transmission coil spring with respect to the driven shaft, and the number of parts is small and the structure is simple and the assembly is easy.

Moreover, the present invention can provide a compact and lightweight overload preventing device which does not require a radial space for the drive shaft and the driven shaft.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an overload prevention device according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of an overload prevention device according to a second embodiment of the present invention.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a vertical sectional view of an overload prevention device according to a third embodiment of the present invention.

FIG. 5 is a vertical sectional view of an overload prevention device according to a fourth embodiment of the present invention.

FIG. 6 is a vertical sectional view of an overload prevention device according to a fifth embodiment of the present invention.

FIG. 7 is a vertical sectional view of an overload prevention device according to a sixth embodiment of the present invention.

FIG. 8 is an exploded cross-sectional view of a conventional overload prevention device.

[Explanation of symbols]

 1,10,20,30,40 Overload prevention device 2 Drive shaft 3 Driven shaft 4 Torque transmission coil spring 21,31 Connection part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunifumi Goto 2-chome, Toyota-cho, Kariya city, Aichi Prefecture Toyota Industries Corporation

Claims (3)

[Claims] 1. A coil spring for torque transmission is closely wound on the same inner or outer circumferential surface of a drive shaft and a driven shaft, and an overload equal to or greater than the transmission torque of the coil spring is applied to the driven shaft. An overload prevention device, wherein a spring portion of the coil spring, which is in close contact with at least one of the two shafts when it occurs, slides relative to the shaft so that the drive shaft idles. 2. The overload prevention device according to claim 1, wherein the drive shaft and the driven shaft are provided with protrusions for restricting axial movement of the coil spring for torque transmission. 3. A torque transmitting coil spring is attached in close contact with a cylindrical connecting portion formed in at least one shaft portion where the drive shaft and the driven shaft are connected. Load prevention device.