GB2076101A - A device for signalling the clutch wear in servoclutches particularly for motor vehicles - Google Patents

Abstract

A device for sensing and signalling the wear in servoclutches has a cap 20 secured to the upper end of the tube 8 in which the stem 9 operatively connected with the clutch is slidably mounted. The end of the stem 9 is perforated to house a bush 28 with a flange 27 which is retained in engagement relationship by a spring 30 against the edge of said tube 8. The lower end of a perforated pin 24 integral with the cap 20 and provided with radial holes 25 and 26 of different section is slidable in the hole of bush 28. As the clutch wear increases, the bush 28 is lifted so that its upper edge gradually closes the larger hole 26, limiting or choking the passage of oil from the connector 22 to the chamber G, thus signalling the clutch wear to the user through the increased resistance to clutch pedal operation by which the oil is pumped to the connector 22. The clutch is actuated pneumatically when a valve is opened by oil passing from chamber G to that valve through a hole 10. <IMAGE>

Description

SPECIFICATION A device for signalling the clutch wear in servoclutches, particularly for motor vehicles This invention is concerned with a device for signalling the clutch wear in servoclutches, particularly servoclutches of motorvehicles; the invention is also extended to servoclutches provided with such a device.

Servoclutches are known and comprise a cylinder-piston assembly actuating the clutch through a pressure fluid (air or oil) under the operator's control. In case of servoclutches for motor-vehicles, it is important to signal or warn the operator about the consumption or wear extent of the clutch engagement surfaces, and at present such a requirement is fulfilled by electrical signallers, the circuits of which are controlled by contacts operated by the piston of the cylinderpiston assembly of the servoclutch.

However, these signalling devices suffer fron an inherent drawback in that the elelctrical circuits can become overburdened by the work conditions in which some servoclutches operate, such as those of industrial vehicle. Additionally, particular cares and installation criteria are required for housing and retaining the contacts and electric wires or conductors to the servoclutch. As a result of these factors, such known devices are subject to failures and breakages which render poor and uncertain the operation thereof.

The device according to the invention seeks to provide a mechanical arrangment for signalling the user about the existence of the clutch wear and in some degree also the extent of such wear.

In its inventive essence, a device according to the invention, applicable to servoclutches in which the pressure generated by a pump by means of a cylinder-piston assembly operated by the user, is applied to the moving element of a commutable valve connecting the chamber of the cylinderpiston assembly of the servoclutch either with the pressure fluid source or with the environment, is characterized by shut off means inserted between the pressure chamber of the pump operated by the user and the chamber of an operating plunger of the commutable valve of the servoclutch, and means for operatively connecting the moving element of said shut off means with the moving element of the cylinder-piston assembly of the servocl utch.

In an advantageous embodiment of the device, applicable to servoclutches for motor vehicles, the shut off means signals the user about clutch wear by increasing the resistance which the user experiences when wear has occured. To this end, the shut off means comprise a bush or sleeve coupled with an axially perforated pin and provided with at least one radial hole, which bush or sleeve and pin are movable relative to each other, and one of which is operatively restrained with the stem of the cylinder-piston assembly of the servoclutch, so that, with the clutch wear, the relative displacement between bush or sleeve and perforated pin is checked, and accordingly the choke or shut off of the radial hole in the perforated pin.Thus, the passage is restrained or hindered for the fluid between the pressure chamber of the pump and that of the plunger operating the commutable valve of the servoclutch to signal the user, through the resistance encountered in the pump operation about the clutch wear, while the operation of the clutch being still allowed.

These and other characteristics and details of the invention will become apparent from the following description referring to the accompanying drawings showing be mere way of example an advantageous embodiment of the device as applied to a servoclutch. In such drawings: Fig. 1 is an axial sectional view of a servocloth equipped with a signalling device according to the invention; Fig. 2 is a sectional view taken along line Il-Il of Fig.1; and Fig. 3 is an enlarged view showing the top portion of Fig. 1 showing details of the signalling device.

The servoclutch shown has a cylinder 1 , the drive piston 2 which is maintained at rest position by a spring 3 and which in its operating phase actuates a thrust or push rod 4 provided with a perforated fork 6 operatively connected to the clutch (not shown). Said cylinder 1 has a tube or sleeve 8, in which a stem 9 connected to piston 2 is slidably mounted.

The tube sleeve 8 has holes 10 and 11 (Fig. 2), the latter of which opens into a chamber A defined by a plunger 12 terminating with a perforated push rod 13 driving a commutable valve 14 controlling the communication between a chamber B connected through a connector 1 6 with a pressure air source (not shown and a supply chamber C through a conduit 18 provided by the chamber F of cylinder 1.

The free end of said tube or sleeve 8 has secured thereon a cap 20 connecting through a connector 22 (Fig. 3) with the chamber of a cylinder-piston assembly of a hydraulic pump (not shown) controlled by the user through the operation of the clutch pedal.

Said cap 20 holds a axially perforated pin 24, coaxially arranged with said stem 9, which is provided with radial holes 25 and 26 of different section.

The free end of the perforated pin 24 extends within the chamber G of cap 20 for sliding insertion in the hole or bore of a bush or sleeve 28, which is accommodated within an axial hole 29 in the end portion of stem 9.

At the upper end, said bush or sleeve 28 has a flange 27 which is maintained in contact with a shoulder formed by the free edge of tube or sleeve 8 through the action of a spring 30.

Said cap 20 has a screw 31 holding a sprung ball valve 32 in bypass controlling through a passage 34 the communication between said chamber G and connector 22 and accordingly with the supply pump.

Said valve 32 operates for providing this communication when the user releases the clutch pedal to allow the oil in chamber G and other parts to flow rapidly back into the cylinder of the supply pump.

In operation of the servoclutch, a user actuating the clutch pedal causes through the operation of the supply pump oil to flow through the connector 22, axial of pin 24 and radial holes 25 and 26 into the chamber G. Then, by passing through the holes 10 and 11, the oil reaches the above mentioned chamber A (Fig. 2) to act upon plunger 12 which, by means of said perforated push rod 13, opens said valve 14 after having shut off the exhaust to atmosphere. Therefore, the pressure air in chamber B passes to chamber C and through said conduit 18 reaches the chamber F, exerting a thrust action on piston 2 controlling the clutch by means of rod 4.

Upon release of the clutch pedal, the oil from chamber A flows back to the pump, enabling the plunger 12 to resume the rest position shown in Fig. 2. Thus, the pressure air in chamber F can exhaust to atmosphere through the inner hole of push rod 13 and outlet D.

When the clutch is not worn, the bush or sleeve 28 takes the position shown in Figs. 1 and 3 of the accompanying drawings.

On the other hand, when the clutch starts to be gradually worn out, a displacement of the push rode 4 takes place and accordingly the stem 9 or piston 2 is displaced in the direction of arrow X. As a result, by overcomming the action of spring 30, said bush or sleeve 28 slides on the perforated pin 24 to partially or completely cover said radial hole 26.

Under these conditions, the passages of oil from connector 22 to chamber A is hindered by the choke of said hole 26. Thus, the user through the strain required for actuating the pedal, receives a signal warning him that the clutch wear exceeds the limit desired for normal operation.

Thus, the object of the present invention is achieved of providing a device applicable to servoclutches which reliably signals the clutch wear state. Of course, the device may provide modifications and changes in connection with the characteristics of the servoclutch to which it is applied. Therefore, the present invention also extends to a servoclutch incorporating the device according to the invention.

Claims (8)

1. A device for sensing and signalling the wear in servoclutches wherein the pressure generated by a pump comprising a cylinder-piston assembly actuated by the user, is applied to the moving element of a commutable valve connecting the cylinder-piston assembly of the servoclutch either with the pressure fluid source or with the ambient or environment, characterized by shut off means (28, 24, 25 and 26) inserted between the pressure chamber (22) of the pump actuated by the user and the chamber (A) of a plunger (12) operating the commutable valve (13 and 14) of the servoclutch, and means (9) for operatively connecting the moving element (28) of said shut off means with the moving element (2 and 4) of the cylinder-piston assembly (1 and 2) of the servoclutch.

2. A device according to Ciaim 1, characterized by a bush or sleeve (28) slidably housing a perforated pin (24) for interconnecting the pressure chamber (22) of the pump operating the servoclutch and the chamber (A) of a plunger(1'2) integral with the operating push rod (13) of the commutable valve (13 and 14) of said servoclutch.

3. A device according to Claims 1 and 2, characterized by a second gauged hole (25) radially presented by the perforated pin (24) and axially displaced from the first radial hole (26) of said pin to establish a choked passage for the fluid when such a first radial hole (26) is covered by the edge of the bush or sleeve (28) to signal the clutch wear to the user.

4. A device according to Claims 1-3, characterized by a sprung valve (32) at bypass position between the pressure chamber (22) of the servoclutch pump and the chamber (A) of the plunger (12) of the commutable valve to allow a rapid back flow of the fluid from said chamber of the plunger to the pump.

5. A device according to Claims 1-4, characterized by a cap (20) removably restrained to the guide body (8) by the servoclutch stem (9) and holding one (24) of the elements of the shut off means, of which the other (28) is restrained with said stem (9), while such a cap has conduits and connectors (10 and 22) connecting it with the chamber (A) of the plunger (12) and with the pressure chamber of the servoclutch pump.

6. A device according to Claims 1-5, characterized by a hole (29) axially persented by one end of the servoclutch stem (9) to house the bush or sleeve (28) which at the outer side has a flange (27) holding one end of a spring (30), the other end of which is retained by the cap (20), said flange engaging against both the edge of said stem (9), and also against an abutment of the servoclutch guide body (8).

7. A servoclutch, particularly for motorvehicles, characterized by involving the clutch wear signalling device according to any of the preceding claims 1-6.

8. A device for sensing and signalling the wear in servoclutches, according to Claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.