JPH0151694B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a centrifugal friction clutch operable by a lever configured as a centrifugal weight, the lever being supported pivotably about an axis arranged on a centrifugal weight support; A spring acts on the lever against centrifugal force, and the lever is further provided with a clutch shoe which can be pressed against the clutch friction surface by the lever, and the clutch shoe is rotated about an axis arranged on the lever. Relates to a type that is pivotably supported. In the case of known clutches, a clutch lever, a clutch friction surface and a clutch shoe are provided externally to the pulley, which results in an overall large construction of the clutch. Furthermore, in known clutches, at low rotational speeds,
This means that after the centrifugal clutch has been disengaged under low centrifugal forces, the clamping body is carried into the sickle-shaped recess due to the extremely high frictional force between the clamping body and the boss of the centrifugal weight support. i.e. there is no frictional connection between the boss and the clutch face, which means that the coefficient of friction between the clamping body and the clutch face is equal to or greater than the coefficient of friction between the clamping body and the boss. This is due to its small size. In the configuration of the present invention, the two axes are located on a straight line connecting the axes, and this straight line corresponds to the vertical force of the clutch against the friction surface and the maximum static friction surface between the friction surface and the clutch. furthermore, the clutch is configured as a two-stage switching drive with two pulleys, between which a freewheel is arranged, and the hub of the centrifugal weight support of the clutch is At least one wedge-shaped clamping body is slidably arranged along the outer periphery in at least one sickle-shaped cutout formed in cooperation with one of the pulleys, the clamping body being free to move. The direction of rotation is limited by the stopper, so that the coefficient of friction between the clamping body and the surface of the clutch part that comes into contact with the clamping body is greater than the coefficient of friction between the clamping body and the boss. did. The advantage of the centrifugal friction clutch according to the invention is that it is space-saving and compact and can therefore be installed particularly advantageously when integrated into motor vehicles. This means that the installation space is only defined by the belt pulley that is required in any case. A further advantage of the centrifugal friction clutch according to the invention is that the functionality of the clutch is guaranteed under all operating conditions. This requires only extremely simple and inexpensive components that do not require heat treatment or precision machining. Particularly advantageously, the clamping body can be made of plastic with a plurality of recesses, so that the weight of the component is considerably reduced and the wear is accordingly reduced. Advantageous embodiments and improvements of the centrifugal friction clutch according to claim 1 are possible with the embodiments described in the following claims. The invention will now be explained with reference to the illustrated embodiment. The centrifugal friction clutch is constructed as a two-stage switching drive and has a first pulley 11 and a second pulley 12, the diameter of which is significantly greater than the diameter of the first pulley 11. It is formed small. The first pulley 11 is mounted on a centrifugal weight support 14 via a double-row ball bearing 13, whereas the second pulley 12 is likewise mounted on a boss 16 via a double-row ball bearing 15. Supported. The centrifugal weight support 14 is connected to the vertical hole 1 of the boss 16.
It has a vertical hole 17 aligned with 8. The centrifugal weight support 14 and the boss 16 are arranged on the output shaft (not shown) of the drive motor and are fixedly connected to the output shaft. The upper part of the rotating centrifugal weight support 14 is provided with two webs 19, 20 with two aligned holes 21, 22 in which a pin 23 is arranged. A lever 25 is rotatably supported on the pin 23 and extends in an arcuate manner within the first pulley 11 over approximately half of the circumference of this pulley 11. The lever 25 is at the same time designed as a centrifugal weight and serves as a mechanism for actuating the clutch by centrifugal force. An annular bearing 26 is formed at one end of the lever 25 and has a hole 27 in which a pin 28 is fixedly arranged. The clutch 2 has a friction lining 30 on the pin 28.
9 is pivotably mounted, the clutch 29 is designed in the form of a segment and does not extend completely over a quarter of the circumference.
The friction lining 30 of the clutch shoe 29 is the first
The friction surface 31 of the inner peripheral surface of the pulley 11 cooperates with the friction surface 31 of the pulley 11 .
The normal force F _N of the frictional force passes through the axis of rotation M at the center of the pulley. In this case, pin 2 of lever 25
The pivot axis L at the center of 7 is located somewhat to the right of the action of the normal force of the frictional force. A connecting line connecting the pivot axis L to the pivot axis D of the pin 23 forms an angle γ with the normal force F _N , and this angle γ is shown as a design angle. The lever 2 resists the centrifugal force acting on the lever 25.
A push spring 33 acts on the spring 5, and this push spring 33 is supported by two spring discs 34, 35 in the shape of a socket. The spring plate 34 is attached to the centrifugal weight support 14
The spring plate 35 abuts against the edge 36' of the screw pin 36 fixed to the pin 37.
The pin 37 rests on the edge 37' of the lever 25, which is fixed to the end face 25' of the lever 25, somewhat below the annular bearing 26. The distance in the direction of action of the spring force F _F with respect to the pivot axis D is designated by the symbol q. The centrifugal force of the lever 25 is designated by the symbol _FZ . The centrifugal force has a lever k relative to the pivot axis D. The frictional force is designated F _R and extends through the pivot axes L and D at a designed angle γ with respect to the normal force F _N . A boss 40 extending toward the second pulley 12 is formed on the centrifugal weight support 14 . boss 40
is not exactly annular in shape, but is approximately polygonal (see Figure 3), which allows
Three sickle-shaped chambers 42, 4 are attached to an annular body 41 to which a pulley 12 is fixed by welding or brazing.
3,44 is formed. Each chamber 42, 43,
A number of clamping wedges 4 are located side by side within 44.
5, 46, 47 are arranged, and these tightening wedges 45, 46, 47 abut against stopper pins 48, 49, 50 at predetermined positions. The annular body 41 at the same time forms a friction surface for the clamping wedge. Centrifugal weight support 14 opposite screw pin 36
An end face 52 is arranged, which screw 52 serves as an end stop for the lever 25 or the centrifugal weight formed by the lever 25, for which purpose the lever 25 is formed with a projection 25''. As shown in the exploded view in FIG. 4, the friction surface 31 has a large number of notches 53, 54, and these notches 53, 54 are elongated and slightly inclined with respect to the rotation axis to reduce friction. It extends over the width of the lining 30. Centrifugal friction clutches with freewheels and pulleys are used in particular for driving auxiliary devices in motor vehicles. 1, and in this case the clutch is engaged, i.e. the spring force of the push spring 33 is greater than the centrifugal force of the lever, so that the friction lining 30 of the clutch shoe 29 is pressed against the friction surface. 31. In this case, the second pulley 12 is idling, that is, the tightening wedge 4
5, 46, 47 are stopper pins 48, 49, 50
pressed against the tightening wedges 45, 46, 47
There is no frictional connection between the annular body and the annular body. For example, in the case of a high rotation speed of 2000/min or more, the centrifugal force increases, causing the lever 25 to pivot around the pivot axis D. In this case, the push spring 33 is compressed and the clutch shoe is lifted from the friction surface 31. It will be done. This disengages the centrifugal friction clutch and brings the clamping wedges 45, 46, 47 into the sickle-shaped chamber.
6 and 47, the annular body 41 and the boss 40, as well as the second pulley 12, are frictionally connected. The auxiliary device is thus driven via the second pulley 12. so that the clutch is switched when the rotational moment of the forces acting on the lever 25 (i.e. spring force F _F , centrifugal force F _Z and friction force F _R ) shifts from balanced to unbalanced about the pivot axis D; The clutch is configured. The configuration of the lever 25 and clutch shoe 29 increases the frictional force. The increase rate a=1/1-tan・cotγ is determined by the geometrical positional relationship between the lever 25 and the clutch 29, that is, the friction lining 30 and the friction surface 3.
1 and the design angle γ. For the clutch, firstly, the disengagement takes place without a slip range or only in a very small slip range, and secondly, the coupling takes place without disturbing shocks and the clutch does not slip continuously or for a long time. The requirement that no The first requirement results in a design angle γ = static friction, which in this case is equal to the maximum static friction angle. For the connection, the circumferential force F _U = a sliding friction F _p tan sliding friction applies, where sliding friction = angle of friction in sliding friction and a sliding friction = rate of increase in sliding friction, F _p = pressure force of the friction lining against the friction surface during connection. Given γ and sliding friction, the second requirement can be obtained by determining F. F relates to the switching systeresis of the clutch during engagement, and the switching systeresis is defined by the arrangement of the pressure spring and the pivot angle Δ of the lever 25. As mentioned above, the clutch is switched when the rotational moment of the force acting on the lever changes from balanced to unbalanced about the pivot axis D. Bearing friction and acceleration forces are ignored for simplicity. In the following formula, L means disconnection and E means connection. Uncoupling is ^F F _L・q _L < ^F
The connection is performed when Z _L・k _L , and the connection is ^F F _E・q _E > ^F Z _E・
This is done in the case of k _E (see diagram in Figure 5).
Depending on the spring arrangement and design, ^F F _L・q _L > ^F
F _E・q _E , and as a result, the switching systeresis and the crimp force of the clutch during connection, F _p , are

In this case, A is the point of application of the frictional force at the center of the clutch. The transmittable circumferential force FU _E during engagement is therefore adjusted by limiting the pivot angle Δ of the lever 25 using the stop screw 52 when assembling the clutch. The type of support for the pressure spring 33 is selected such that the centers of rotation of the spring plates inside the pressure spring (pin edges 36', 37') are located at an interval of approximately one-third of the spring length. . This gives the function shown diagrammatically in Figure 5, where = _L
In the range (constant release speed even in case of wear of the friction lining) a gentle curve occurs, and in the range = _E (required switching systeresis at small swing angles) a steep downward slope occurs.
The advantage of the internally offset spring bearing type, which is designed as a knife-edge bearing element, is that the friction is low and buckling is well prevented. The spring moment is smaller in the coupled state than in the uncoupled state. In order to minimize the change in the design angle γ in the event of wear, the distance between the point of action A and the pivot axis L must be as small as possible. In order to guarantee the function of the freewheel, the coefficient of friction between the clamping wedges 45, 46, 47 and the boss 40 is lower than the coefficient of friction between the clamping wedges 45, 46, 47 and the inner surface 41' of the annular body 41. also needs to be made smaller. This ensures that the clamping wedge is entrained into the sickle-shaped chambers 42, 43, 44 when the centrifugal friction clutch is disengaged. This can be achieved, for example, by providing a dry lubricant between the clamping wedge and the boss surface. Furthermore, the dry lubricant can be provided, for example, on the underside of the clamping wedge or on the surface of the boss 40 facing the clamping wedge. Another possibility of reducing the coefficient of friction consists in arranging a sliding plate 51' between the clamping wedge and the boss 40 (see FIG. 6). Advantageously, the sliding plate 51' is made of polytetrafluoroethylene (PTFE).
covered by. Preferably, the clamping wedges 45, 46, 47 are made of plastic with honeycomb-shaped cutouts 52' in order to reduce weight. Such a component is simple to manufacture, does not require heat treatment, as does the clamping body in the case of known freewheels, and is extremely light. This significantly reduces wear.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a plan view of a centrifugal friction clutch, Fig. 2 is a sectional view taken along the line of Fig. 1, and Fig. 3 is a sectional view taken along the line of Fig. 2. 4 is a developed view of the friction surface, FIG. 5 is a diagram, and FIG. 6 is a diagram showing a tightening wedge. 11, 12... Pulley, 13, 15... Double row ball bearing, 14... Centrifugal weight supporter, 16, 40... Boss, 17, 18... Vertical hole, 19, 20... Web, 2
1, 22, 27...hole, 23, 28, 37...pin,
25...Lever, 25'...End face, 25''...Protrusion, 26
...Annular bearing part, 29...Clutch shoe, 30...Friction lining, 31...Friction surface, 33...Press spring,
34, 35...Spring plate, 36...Screw pin, 36',
37'... Edge, 41... Annular body, 41'... Inner surface, 4
2, 43, 44... Chamber, 45, 46, 47... Tightening wedge, 48, 49, 50... Stopper pin, 51
...end face, 51'...sliding thin plate, 52...screw, 52',
53, 54...Notch, M...Rotation axis, L, D...Turning axis, F _F ...Spring force, F N...Normal force, F _p ...Crimping force, F _R ...Frictional force, F _{U ...} Circumferential force , F _Z ... centrifugal force,
q...distance, k...lever arm, γ...angle, A...point of action,
...Friction angle.

Claims (1)

Claims: 1. A centrifugal friction clutch, actuable by a lever 25 configured as a centrifugal weight, which lever 25 pivots about an axis D arranged on the centrifugal weight support 14. A spring 33 acts against the centrifugal force on the lever, and the lever is further provided with a clutch shoe 29 which can be pressed against the friction surface of the clutch by the lever. 29 is rotatably supported around an axis L disposed on the lever, the two axes D and L are located on a straight line connecting these axes, and this straight line is A two-stage switching drive in which the normal force F _N of the clutch shoe 29 on the friction surface 31 forms an angle γ equal to the maximum static friction angle between the friction surface 31 and the clutch shoe 29, and in which the clutch has two pulleys. a freewheel is arranged between the two pulleys, and at least one sickle-like shape is formed in cooperation with one of the pulleys 12 along the outer periphery of the boss 40 of the centrifugal weight support of the clutch. Notches 42, 43, 4
at least one wedge-shaped clamping body 4 in 4
5, 46, 47 are slidably arranged, the movement of the clamping bodies 42, 43, 44 is restricted in the free rotation direction by stoppers 48, 49, 50, and the clamping bodies 45, 46, 47 and tightening body 4
The coefficient of friction between the surface 41' of the clutch portion 41 that contacts the clamping bodies 45, 46, 47
47 and the boss 40. 2. A centrifugal friction clutch according to claim 1, wherein the lever (25) together with the clutch shoe (29) and the spring (33) are arranged inside the other pulley (11). 3. A patent in which the clutch 29 is composed of a segment-shaped block, and the pivot axis L of this block is located on the joining line between the point of application A of frictional force (the center of the clutch) and the pivot axis D of the lever 25. A centrifugal friction clutch according to claim 1. 4 The distance between the rotation axis L and the point of action A is the rotation axis D
2. A centrifugal friction clutch according to claim 1, wherein the clutch is smaller than one quarter of the distance between the point of application A and the point of application A. 5. The centrifugal friction clutch according to claim 1, wherein the pivot angle Δ of the lever 25 is limited. 6 Spring plate 3 with a spring plate 3 that is shaped like a spring so that the spring 33 can swing
4, 35, the spring plates 34, 35 themselves resting against the edges of the pins 36, 37, one of which is arranged on the centrifugal weight support 14 of the clutch and the other on the lever 25. has been
A centrifugal friction clutch according to claim 1, wherein the edge of the pin is located inside the spring. 7 Notches 53 and 54 are formed in the friction surface 31, and these notches 53 and 54 are shaped like elongated holes and are slightly inclined with respect to the rotation axis to form the friction lining 3.
A centrifugal friction clutch according to claim 1, wherein the centrifugal friction clutch extends over a width of 0. 8. The centrifugal force friction clutch according to claim 1, wherein a dry lubricant is provided between the fastening bodies 45, 46, 47 and the boss 40. 9. Centrifugal force according to claim 1, wherein a thin sliding plate 51' made of a thin plate coated with polytetrafluoroethylene (PTFE) is provided between the fastening bodies 45, 46, 47 and the boss 40. Friction clutch. 10. A centrifugal friction clutch according to claim 1, in which the clamping bodies 45, 46, 47 are made of plastic. 11. The centrifugal friction clutch according to claim 1, wherein three clamping bodies 45, 46, 47 are provided.