JP3326951B2 - Torque limiter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque limiter used for a screw tightening operation or the like.

[0002]

2. Description of the Related Art Generally, a torque limiter includes an input shaft,
An output shaft, an input shaft, a torque setting member for determining a degree of coupling between the output shafts, and when the torque of the output shaft exceeds a set value determined based on the degree of coupling, the input shaft and the output shaft are coupled. To a non-coupled state.

FIGS. 3 and 4 show the structure of a conventional torque limiter, respectively.

[0004] The torque limiter shown in FIG.
1, a sun gear 102 fixed to the input shaft 101, planetary gears 103 and 103 meshed with the sun gear 102,
Carrier 104 axially mounted on planet gears 103
, An output shaft 105 connected to the carrier 104, and a planetary gear 10 rotatably disposed in the housing 106.
3, 103 and the internal gear 107 meshed with
A steel ball which is vertically movably inserted into a through hole 108 formed in the inner gear 107 and is kept in contact with an inclined surface 107 a provided on the lower surface of the internal gear 107 when the torque of the output shaft 105 is equal to or less than a set value. 109, a pusher pin 111 for receiving the elastic restoring force of the compression coil spring 110 to push the steel ball 109 to the lower surface of the internal gear 107, and a flange 112 disposed between the compression coil spring 110 and the pusher pin 111.
And When the torque of the output shaft 105 is equal to or less than the set value, the steel ball 109 prevents the rotation of the internal gear 107, and the sun gear 102, the planetary gear 10
3, 103, the torque is transmitted to the output shaft 105 via the carrier 104, and when the torque of the output shaft 105 exceeds the set value, the inclined surface 107a of the internal gear 107 is changed to the steel ball 109, the pusher pin 111, the compression coil spring 110 Down,
The internal gear 107 rotates so that the input shaft 101 idles, so that the torque of the input shaft 101 is not transmitted to the output shaft 105.

On the other hand, the torque limiter shown in FIG. 4 has an input shaft 101, an output shaft 105 rotatably disposed with respect to the input shaft 101, a rotatable support for the output shaft 105, and a compressed air supply port 106a. And a ring-shaped cylinder portion 106b formed in the housing 106 and opening the compressed air supply port 106a.
A ring-shaped piston 113 housed in the cylinder portion 106b so as to be able to advance and retreat in the axial direction, a flange 114 abutting on the front surface of the piston 113, a bearing 115 housed in the flange 114, and a pusher abutting on the bearing 115 A ring 116 and a steel ball 109 that is received in the recess 105 a formed in the output shaft 105, receives the thrust of the pusher ring 116, and is locked in the engagement recess 101 a formed in the input shaft 101. When the torque of the output shaft 105 is equal to or less than the set value, the steel ball 109 is kept locked in the engagement recess 101 a of the input shaft 101, and the input shaft 101, the steel ball 109, the pusher ring 116 and the output shaft When the torque of the output shaft 105 exceeds the set value, the engagement concave portion 101a retreats the steel ball 109, the pusher ring 116, the bearing 115, the flange 114, and the piston 113 so that the input shaft 105 rotates. 101 idles, input shaft 1
01 is not transmitted to the output shaft 105.

[0006]

However, in the former torque limiter, since the mass of the internal gear 107 is large and its inertia is large, when the torque of the output shaft 105 exceeds a set value, the internal gear 107 is not moved. There was a problem that it was not possible to smoothly transition from the stationary state to the rotating state, and it was difficult to instantaneously idle the input shaft 101. This problem was particularly noticeable during high-speed rotation. In addition, since the set value is set by the compression coil spring, the set value is fixed, and there is a problem that it is not easy to change the set value.

In the latter torque limiter, since the mass of the bearing 115 is large and its inertia is large, when the torque of the output shaft 105 exceeds the set value, the steel ball 10
9 cannot smoothly escape from the engagement recess 101a, and the input shaft 1
There is a problem that it is difficult to instantaneously idle 01. This problem was remarkable at the time of high-speed rotation like the former torque limiter. Further, in the latter torque limiter, since the sliding resistance of the packing 17 disposed on the outer periphery of the piston 113 becomes one of the setting elements of the above set value, the cylinder is simply provided through the compressed air supply port 106a. By simply setting the compressed air pressure to be supplied to the portion 106b,
Since the set value is not uniquely determined, the set value cannot be easily set, and the lower limit of the set value is limited by the sliding resistance of the packing 117, so that the set range of the set value is narrowed. There was a problem.

An object of the present invention is to provide a torque limiter which solves these problems, and which is particularly suitable for high-speed rotation and which can expand the setting range of a set value.

Another object of the present invention is to achieve a simple configuration of the input shaft bearing and torque setting.

[0010]

According to a first aspect of the present invention, there is provided a torque limiter for determining a coupling between an input shaft, an output shaft, and the input shaft and the output shaft. When the torque of the output shaft exceeds a set value determined based on the degree of coupling, the input shaft and the output shaft change from a coupled state to a non-coupled state in a torque limiter. , the fluid pressure magnitude
The coupling degree is determined steplessly in accordance with the degree, and the configuration is such that the hydrostatic bearing rotates integrally with the input shaft.

Further, the torque limiter according to claim 2 is
2. The torque limiter according to claim 1, wherein the output shaft and the input shaft are connected by a cam and a ball, and the torque setting member is rotatably and slidably supported by the static pressure bearing. And a coupling degree between the cam and the ball is changed by switching a supply / exhaust path of a fluid constituting the hydrostatic bearing.

[0012]

According to the torque limiter of the first aspect, when the torque of the output shaft is equal to or less than the set value, the input shaft and the output shaft are maintained in a coupled state, and the torque of the input shaft is transmitted to the output shaft. You.

When the torque of the output shaft exceeds the set value, the state between the input shaft and the output shaft changes to a non-coupled state, the input shaft idles, and the torque of the input shaft is not transmitted to the output shaft.

[0014] The torque setting member determines the degree of coupling between the input shaft and the output shaft according to the fluid pressure, and rotates integrally with the input shaft by means of a hydrostatic bearing. Here, even when the hydrostatic bearing is involved in the determination of the degree of coupling, since the frictional resistance of the hydrostatic bearing is extremely small, the hydrostatic bearing can be almost ignored in determining the degree of coupling.
Therefore, the degree of coupling can be uniquely determined by adjusting the fluid pressure, and the setting of the set value is facilitated, and the set value can be set to a small value.
The setting range of the setting value can be expanded. Also,
Since the frictional resistance is extremely small by the hydrostatic bearing,
It is not necessary to provide a rotation separating mechanism such as a bearing on the torque setting member. For this reason, the weight of the torque setting member can be reduced, and the inertia decreases due to the reduction in weight.
It is also suitable for high-speed rotation.

Further, according to the torque limiter of the second aspect, the fluid constituting the bearing and the fluid controlling the coupling of the input shaft and the output shaft can be shared, and the structure can be simplified.

[0016]

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

FIG. 1 shows a torque limiter according to one embodiment. FIG. 1 (A) is a sectional view taken along the line AA in FIG. 1 (B).
FIG. 1B is a sectional view taken along line BB in FIG. 1A.

In FIG. 1, a torque limiter includes a housing 1, a driving force introducing member 2 for introducing a driving force from the outside to the inside of the housing 1, and a torque limiter housed inside the housing 1 and driven by the driving force introducing member 2. Input shaft 3
An output shaft 4 for taking out torque outside the housing 1;
A torque setting member that rotates integrally with the input shaft and determines a degree of coupling between the input shaft and the output shaft;
An output-side rotating member 6 is housed inside, rotates integrally with the output shaft 4, and receives a thrust by the torque setting member 5.

The housing 1 has a window 1a through which the driving force introducing member 2 passes, a through hole 1b through which the output shaft 4 passes, an input shaft 3,
A housing chamber 1c for housing the torque setting member 5 and the output side rotating member 6, a compressed air supply port 1d, a compressed air chamber 1e,
A compressed air outlet 1f is formed.

The driving force introducing member 2 is constituted by a timing belt driven by driving means (not shown).

The input shaft 3 is composed of a hollow cylindrical pulley around which the timing belt 2 is hung.

The output shaft 4 has, at its tip, an engaging portion 4a which is engaged with the head of a screw (not shown) to be tightened. A drive unit (not shown) for driving the output shaft 4 in the axial direction is provided on the base side of the output shaft 4.

The torque setting member 5 comprises a hollow cylindrical piston 7, a pusher pin 8, and a ball (steel ball) 9.

The piston 7 is accommodated in the cylinder portion 1g of the housing 1 so as to be rotatable and movable in the axial direction. The piston 7 is connected to the input shaft 3 by a plurality of connecting pins 10 so as to be movable in the axial direction with respect to the input shaft 3 and to be rotatable integrally with the input shaft 3. I have. The piston 7 is provided with a throttle portion 7a for communicating between the pressure receiving surface on the side of the compressed air chamber 1e and the outer peripheral surface, and blowing compressed air to the inner peripheral surface of the cylinder portion 1g to form a static pressure bearing portion. Air passage 7b is formed. The piston 7 is relatively lightweight, and is made of, for example, a synthetic resin.

The pusher pin 8 is formed in the pulley 3 so as to be axially movable in each of a plurality of, for example, three through holes 3a formed in the axial direction and at equal intervals in the rotational direction. Is housed in The pusher pin 8 has a function in which the piston 7 receives an axial thrust given by compressed air and transmits this thrust to the steel ball 9.

The steel balls 9 are provided in one-to-one correspondence with the respective pusher pins 8, and can be moved in the axial direction in the through holes 3a, and partially exposed outside the through holes 3a. Are housed to be.

The output side rotating member 6 is rotatably supported by the housing 1 and comprises a spline 11 and a cylindrical body 12 with a cam. The spline 11 is fitted into the output shaft 4 and allows the output shaft 4 to move in the axial direction.
And it rotates integrally with the output shaft 4. The cylindrical body with cam 12 is provided with a key 13 on the outer periphery of the spline 11.
It is fixed at. The cylindrical body with cam 12 is rotatably supported by the housing 1. The steel ball 9 is pressed into contact with the cam portion 12a of the cylindrical body 12 with cam.

Next, the operation and effect of the torque limiter having the above configuration will be described.

When compressed air of a predetermined pressure is applied to the compressed air chamber 1e from the air pressure source (not shown) via the compressed air supply port 1d, the piston 7 receives the compressed air pressure and generates a thrust in the axial direction. This thrust is applied to the cam portion 12 a of the cylindrical body 12 with cam via the pusher pin 8 and the steel ball 9.
Act on. This thrust can be adjusted by adjusting the compressed air pressure generated by the air pressure source. Therefore, the degree of coupling between the steel ball 9 and the cam portion 12a is determined according to the magnitude of the compressed air pressure. When the compressed air pressure is large, the degree of coupling is large, while when the compressed air pressure is small, the degree of coupling is small. The degree decreases.

The compressed air in the compressed air chamber 1e is blown out to the inner peripheral surface of the cylinder portion 1g through the air passage 7b to form a static pressure bearing portion 14 for the piston 7, so that the piston 7 is rotatable. You. Accordingly, the frictional resistance of the piston 7 is extremely small, and the degree of coupling between the steel ball 9 and the cam portion 12a, in other words, the set value is uniquely determined by the compressed air pressure, and the set value is easily set. Further, since the frictional resistance of the piston 7 is extremely small, the set value can be set to a small value, and the set range of the set value can be expanded. Further, since the frictional resistance of the piston 7 is extremely small, the piston 7 is hardly worn.

When the timing belt 2 is driven, the pulley 3 rotates together with the piston 7. Since the steel ball 9 and the cam portion 12a are connected to each other, the torque of the pulley 3 is controlled by the cylinder 12 with the cam, the spline 11
To the output shaft 4, and the engaging portion 4a at the tip of the output shaft 4 rotates. Here, since the piston 7 rotates integrally with the pulley 3, there is no need for a rotation separation mechanism such as a bearing between the piston 7 and the pulley 3, and only the mass of the rotation separation mechanism will be described later. The inertia when the steel ball 9 retreats is reduced, and the pulley 3 can be smoothly shifted to the idling state.

The torque of the output shaft 4 is changed between the steel ball 9 and the cam portion 12.
As long as the value is equal to or less than the set value determined by the degree of coupling with the a, the steel ball 9 and the cam portion 12a are kept in the coupled state, and the torque of the input shaft 3 is transmitted to the output shaft 4.

When the torque of the output shaft 4 exceeds the set value, the cam portion 12a retreats the steel ball 9, and the steel ball 9 and the cam portion 12a change to a non-coupled state.
Idle, and the torque of the pulley 3 is not transmitted to the output shaft 4. Here, the steel ball 9 is retracted instantaneously because the mass of the pusher pin 8 and the piston 7 is relatively small and the inertia is small. Therefore, pulley 3
The transition to the idling state is performed very smoothly.

As described above, in the torque limiter of this embodiment, when the torque of the output shaft 4 exceeds the set value, the steel ball 9 retreats instantaneously, and the pulley 3 can smoothly shift to the idling state. For this reason, when the torque limiter is used for a high-speed screw tightening operation, as shown in FIG. 2 (A), in order to prevent the screw from being broken, the conventional torque limiter has to be mounted before the screw is seated. It was necessary to reduce the rotation speed of the output shaft and terminate the screw tightening at this low rotation speed, and thus the working time was long, but in the torque limiter of this embodiment, the screw was seated. Output shaft 4
When the torque exceeds the set value, the pulley 3 can smoothly shift to the idling state, and as shown in FIG. 2B, the output shaft 4 can be rotated at high speed until the screw is seated. Therefore, the working time can be reduced. As shown in FIG. 1 (B), a position sensor 15 for detecting the axial position of the piston 7 is provided in the housing 1, and the timing belt 2 is stopped when the position sensor 15 detects the displacement of the piston 7. By doing so, it is possible to prevent noise, abrasion, and the like caused by the steel ball 9 hitting the cam portion 12a when the pulley 3 rotates.

[Brief description of the drawings]

FIG. 1 is a sectional view of a torque limiter according to one embodiment.

FIG. 2 is a graph for explaining the effect of the torque limiter.

FIG. 3 is a sectional view of a conventional torque limiter.

FIG. 4 is a sectional view of another conventional torque limiter.

[Explanation of symbols]

 Reference Signs List 3 input shaft (pulley) 4 output shaft 5 torque setting member 7 piston 7b air passage 9 ball (steel ball) 12a cam (cam portion)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23P 19/06 B25B 23/157

Claims (2)

(57) [Claims] 1. An input shaft, an output shaft, and a torque setting member for determining a degree of coupling between the input shaft and the output shaft, wherein a torque of the output shaft is set based on the degree of coupling. If it exceeds, in the torque limiter in which the input shaft and the output shaft change from the connected state to the non-coupled state, the torque setting member is determined steplessly according to the magnitude of the fluid pressure, and A torque limiter characterized by being configured to rotate integrally with an input shaft by a hydrostatic bearing. 2. The output shaft and the input shaft according to claim 1, wherein the output shaft and the input shaft are connected by a cam and a ball, and the torque setting member is rotatably and slidably supported by the hydrostatic bearing. Having a piston,
A torque limiter, wherein a degree of coupling between the cam and the ball is changed by switching a supply / exhaust path of a fluid constituting the hydrostatic bearing.