JPS596268Y2 - dry friction clutch - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a dry friction clutch.

A clutch is generally provided between an engine crankshaft and a transmission input shaft.

That is, the annular friction facing of the clutch plate with its hub splined on the transmission input shaft as the driven shaft of the clutch to the annular surface of the flywheel fixed to the engine crankshaft as the drive shaft of the clutch; Pressed by the annular pressing plate, torque is transmitted from the crankshaft to the transmission input shaft via the flywheel and clutch plate.

In such a clutch, even when the clutch is disengaged, the friction facing of the clutch plate remains in contact with the flywheel due to the sliding resistance between the hub of the clutch plate and the transmission input shaft that is spline-fitted to the hub of the clutch plate. In some cases, torque is transmitted from the crankshaft to the transmission input shaft, making it impossible to change gears in the transmission.

This phenomenon is called clutch disengagement failure.

In order to eliminate this disconnection failure, the surface of the annular friction facing on the flywheel side of the clutch plate is coated starting from the inner circumferential edge of the ring, not reaching the outer circumferential edge of the ring, but at an angle to the radius in the direction of rotation of the flywheel. We proposed that a plurality of inclined grooves be provided at equal intervals in the circumferential direction.

As a result, when the clutch is disengaged, air that enters the groove from the inner peripheral edge of the annular friction facing flows radially outward in this groove, changes direction from the outer end of the groove, and exits in the axial direction. The reaction force and fluid wedging that occurs during airflow redirection aids in disengaging the clutch plate from the flywheel and improves clutch disengagement.

These grooves are formed at the same time during hot press processing of the friction facings, and as a result of various experiments, clutch disengagement is related to the surface roughness of the inner surface of the grooves, and this surface roughness is 160 μm.
We found that the following is preferable.

It has also been found that such surface roughness also improves the cooling of the friction facing by the air flowing through the grooves.

The invention will be explained below with reference to the drawings.

1 and 2, the engine crankshaft 1
A flywheel 2 is fixed to the frame with bolts or the like.

The flywheel 2 has an annular surface 3 forming a frictional engagement surface.

The flywheel 2 is provided with an air inflow through hole 2a near the center, and an inclined surface 2b extending from the center to the annular surface 3 is formed on the inner peripheral surface of the tray-shaped recess. Fins 33 are provided.

A transmission input shaft 4 is provided coaxially with the crankshaft 1 and is rotatable relative to the crankshaft 1 via a bearing 5.

An axial spline 6 is formed on the input shaft 4, and a clutch plate 3 has an axial spline groove that fits into the spline 6.
A hub 7 of No. 0 is supported on the input shaft 4 so as to be movable only in the axial direction.

A plurality of windows 9 are formed in the disk portion 8 of the hub 7 at equal intervals in the circumferential direction, and a cylindrical spring 10 (rubber or coil spring) is inserted into each of these windows. An annular holding plate 11 and annular side plates 12 are arranged on both sides of the disc portion 8 and are connected to each other by pins 13.

The retaining plate 11 and the side plates 12 also have windows 14 and 15, respectively, into which springs 10 fit, connecting the hub 7 and the retaining plate 11 in the circumferential direction.

Around the periphery of the holding plate 11, a plurality of substantially rectangular plate-shaped cushion springs 50 having mounting ears 51 and extending in the circumferential direction are riveted with the mounting ears 51 at equal intervals around the circumference.

In order to smoothly connect the clutch and facilitate half-clutch operation, this spring plate 50 is gently bent into an S-shape in the circumferential direction, and has protrusions 5 that protrude to opposite sides of the plate surface.
2 and 53, annular friction facings 16,17 are fixed by studs 54.

An annular pressing plate 18 that presses the clutch plate 30 toward the annular surface 3 of the flywheel 2 is supported by a clutch force bar 19 held by the flywheel 2 so as to be movable in the axial direction.

The annular diaphragm spring 20 with radial notches is
The pressing plate 18 is moved by a retraction spring 20a engaging its outer edge
The clutch force bar 19 rests on a protrusion 21 on the outer edge of the clutch force bar 19, and its intermediate portion is supported by a stud 22 on the clutch force bar 19.

FIG. 1 shows a state in which a clutch pedal (not shown) is depressed and the clutch is disengaged.

That is, the diaphragm spring 20 assumes the position shown,
The pressure plate 18 is separated from the flywheel 2 via a retraction spring 20a that engages its outer edge.

When the depression force on the clutch pedal is removed, the inner edge of the diaphragm spring 20 is moved to the right by a clutch release fork (not shown) via a release bearing (also not shown), and the diaphragm spring 20 is moved around the stud 22 as a fulcrum. is reversed, its outer edge moves to the left, and protrusion 2
1 to move the press plate 18 to the left.

As a result, the friction facings 16 of the clutch plate 30,
17 is held between the annular surface 3 of the flywheel 2 and the pressing plate 18 with a predetermined pressing force.

The torque of the crankshaft 1 is now transmitted to the transmission input shaft 4 via the flywheel 2 and the clutch plate 3a that is frictionally engaged with the flywheel 2.
transmitted to.

The surface of the annular friction facing 16 is formed with a plurality of grooves 25 at equal circumferential intervals, starting from the inner periphery of the facing and not extending to the outer periphery of the ring.

Are these grooves 25 inclined in the direction of rotation A of the flywheel at an angle with respect to the radial direction (Fig. 2)?
, or on the radius (FIG. 5).

Further, the cross section of this groove 25 can take the shape of a rectangle (FIG. 6a) or an isosceles trapezoid (FIG. 6b).

Further, the groove 25 may have a constant depth and end with an arcuate outer end wall as shown in FIG. 7a, or an end wall of constant depth and an acute angle to the facing surface as shown in FIG. It can be made to end with

Note that the holding plate 11 in front of these grooves 25 is provided with fins 34 for introducing air into the grooves 25.

Now, considering the state of the air inside the clutch force bar 19, as shown in FIG. is due to the centrifugal force generated by the rotation and the action of the fin 33, as shown by the arrow,
The air flows toward the outer circumference of the clutch force bar 19 centering around the air inlet through hole 2a provided in the flywheel 2, and in particular, the air in the space between the flywheel 2 and the clutch plate 30 flows between the annular surface 3 and the friction facing 16, which are opposed to each other. The flow tends to flow radially outward between the surface and the surface.

With the clutch in the connected state, when the clutch pedal is depressed and the pressing force of the annular pressing plate 18 is removed, the air inflow hole 2
The air flowing in from a is guided by the fins 34,
It flows radially outwardly in a groove 25 provided in the friction facing 16 and exits the groove 25 at the outer end of the groove as indicated by arrow B in FIG. 7a.

The reaction force R caused by the deflection of the air flow and the fluid wedging effect then facilitate the disengagement of the friction facing 16 and thus of the clutch plate 30 from the flywheel 2.

Now, as mentioned above, the grooves 25 in the friction facings 16 of the clutch plate 30 are formed at the same time as the friction facings are hot-pressed, but the roughness of the inner surface of the grooves 25 affects the disengagement of the clutch. I understand.

In other words, as shown in Figure 8a, if the inner surface of the groove is smooth, the air flow will flow in a laminar state along the inner surface of the groove to its outer edge, and change direction at the outer edge. Most of the airflow flowing through the groove serves to generate a reaction force, but if the inner surface of the groove is rough, as shown in Figure 8b,
Due to the unevenness of the inner surface, the airflow inside the groove becomes turbulent, making it impossible to obtain a uniform flow of air to the outer edge of the groove, and because the airflow changes direction in a thin pattern within the groove. , the resulting reaction force R'
is small.

As a result of experiments on actual friction facings, a relationship as shown in FIG. 9 was obtained between the surface roughness Rz of the groove and the clutch disengagement force F.

In this case, surface roughness is the 10-point average roughness of each randomly selected part of the solid surface (UIS BO601).
is the arithmetic mean value of each.

In the figure, the circles indicate measured values, and the hatched areas indicate the range of variation in the measured values.

Fa represents the lower limit of the disengagement force that eliminates the problem of clutch disengagement, and the surface roughness at this time is 162μ.

On the other hand, when considering the actual usage conditions of the clutch, poor disengagement generally occurs when the friction lining is worn to some extent.

Therefore, it is best to set the surface roughness in consideration of eliminating cutting defects in this worn state of the lining. For example, if the surface roughness is 80 μ or less (range marked with an X in the figure), cutting defects will occur. is completely resolved.

Note that the disengagement force of the clutch plate differs depending on the ratio of the groove area to the area of the friction facing, but this difference is not significant because the size of the groove area is set taking into account wear and cutting defects of the facing. No.

As described above, according to the present invention, by appropriately setting the surface roughness of the groove of the friction facing, the surface roughness Rz decreases until the surface roughness Rz reaches 160μ or less, as shown in FIG. However, with the present invention, when the surface roughness becomes 160μ or less, the breakaway force decreases. It was found that there was a rapid improvement.

Thus, according to the invention, the groove 2 of the annular friction facing 16
The surface roughness of the inner surface of No. 5 is set to 160μ or less, making it possible to use the reaction force of the air flow more effectively for disengaging the clutch.

A further advantage is that the cooling effect of the friction facings is improved as a result of the improved air flow within the grooves.

[Brief explanation of drawings]

Figure 1 is a sectional view along the central axis of the clutch according to the present invention;
Fig. 2 is a front view of the clutch plate, Figs. 3 and 4 are a front view and a plan view of the cushion spring, Fig. 5 is an enlarged front view of a part of a different embodiment of the clutch plate, and Fig. 6a. 6b is a cross-sectional view of different grooves of an annular friction facing, FIGS. 7a and 7b are longitudinal sectional views of similarly different grooves, and FIGS. 8a and 8b are surface roughness of the grooves. FIG. 9 is a longitudinal cross-sectional view showing the state of air flow depending on the degree of air flow, and FIG. 9 is a diagram illustrating the operation of the present invention. 1... Drive shaft, 2... Annular engagement plate, 4... Driven shaft, 16. 17... Annular friction facing, 18.
...Annular pressure plate, 25...Groove, 30...Clutch plate.

Claims (1)

[Scope of utility model registration request] An annular engagement plate fixed to the drive shaft, a clutch plate supported for axial movement on a driven shaft coaxial with the drive shaft, and annular friction facings attached to both sides around the clutch plate. , an annular pressing plate that presses the friction facing of the clutch plate against the engagement plate, and a plurality of annular pressing plates that are provided on the annular friction facing on the annular engagement plate side of the clutch plate and that start from the inner circumferential edge of the ring and do not reach the outer circumferential edge of the ring. A dry friction clutch comprising grooves, the inner surfaces of these grooves having a surface roughness of 160μ or less.