192 clutches and power-stop control – Clutches – Operators
Reexamination Certificate
1999-11-24
2001-06-12
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Clutches
Operators
C192S10900B, C091S447000, C137S116300
Reexamination Certificate
active
06244410
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a starting control to control a hydraulic piston/cylinder unit, in particular to control a multi-disc clutch. The present invention further relates to a multi-disc clutch having a disc package which can be compressed by a piston, having a feed for a hydraulic medium being disposed in such a way that a force directed to the disc package can be generated on the piston when pressure is applied to the feed, and having one or more restoring elements which apply a counter-force to the piston working against the force which can be applied by the hydraulic medium. The present invention further relates to a vehicle, in particular a commercial vehicle, having a piston/cylinder unit which can be subjected to a hydraulic medium.
A multi-disc clutch possesses several clutch discs disposed on a drive shaft which clutch disks are, when the clutch is actuated, connected non-positively to gears or disks provided between the discs and being in communication with a drive shaft and allowing in this way the transfer of a torque. When the clutch is actuated, a movably disposed piston is subjected to hydraulic oil and thus moved in the direction of the disc package. After overcoming the release path existing between piston and disc package, the piston abuts the disc package and compresses the disc package in dependence on the oil pressure being applied, whereby the output shaft and the input shaft are connected non-positively to each other. When the piston is relieved of the oil pressure, it is pressed back by the restoring springs of the clutch and the clutch is disengaged in this way.
To ensure the secure separation of the clutch, a certain release path has to be observed whose size depends not only on production tolerances of the discs, but also on the wear of the clutch. As the wear of the discs increases, the release path also becomes longer. With known prior multi-disc clutches, it is disadvantageous that the time slope of the clamping pressure of the piston on the disc package is dependent on the size of the release path to be covered. It follows from this that production tolerances or clutch wear increasing in operation impact on the shift characteristic of the clutch. This can, for example, lead to the clamping pressure increasing in a relatively short time with increased wear, which results in a correspondingly short actuation of the clutch.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide an apparatus by means of which a soft actuation of the clutch can be effected.
This object is solved by a starting control of the generic type which comprises a control valve which can be moved into an open and a closed position, a first connecting line which can be connected to the hydraulic piston/cylinder unit and a second connecting line which can be connected to a pressure feed. The first and second connecting lines are in communication with the control valve. The first connecting line is designed in such a way that when pressure is applied to it, a force acting in the closing position can be generated on the control valve. Furthermore, a first control line is provided which is in communication with the control valve in such a way that when pressure is applied to it, a force acting in the open position can be generated on the control valve. The starting control in accordance with the invention further possesses a restrictor element whose inlet can be connected to the pressure feed and whose outlet is in communication with the pressure store and the first control line. The control valve is designed in accordance with the invention in such a way that it is moved from the open position into the closed position when the pressure force acting in the first connecting line exceeds the pressure force acting in the first control line by a given amount.
By means of the starting control in accordance with the invention, it is achieved that oil or any other suitable hydraulic medium first flows into the piston chamber of a multi-disc clutch until the control valve closes. The control valve is closed in accordance with the invention when the force acting in the closed position when pressure is applied to the first connecting line exceeds the force acting in the open position when pressure is applied to the first control line by a given amount. This given amount should advantageously be coordinated in such a way that the pressure existing in the piston chamber of the piston/cylinder unit or the multi-disc clutch is sufficient to guide the piston of the multi-disc clutch to the disc package against the force of the restoring springs.
If the pressure existing in the first connecting line increases, the control valve is closed when the difference which can be given is exceeded.
The hydraulic medium flowing in is now led into the pressure store via the restrictor element, with the pressure existing in the outlet of the restrictor element also applying in the first control line of the control valve. Increasing the pressure in the first control line leads to the control valve opening again, whereby finally pressure builds up in the piston chamber of the piston/cylinder unit or the multi-disc clutch at the same speed as in the pressure store of the starting control in accordance with the invention. In this way, it is achieved that irrespective of the length of the release path to be covered always the desired time slope of the clamping pressure of the piston on the disc package exists. The clamping pressure is increased in a given time from zero to the maximum value.
In accordance with a preferred aspect of the present invention, a second control line is provided which is in communication with the first connecting line and the control valve and which is designed in such a way that when pressure is applied to the second control line, a force acting in the closing position can be generated on the control valve. It thus becomes possible not to exert the force acting in the closed position on the control valve or not to exert it exclusively through the first connecting line, but through the second control line. The second control line can be designed as a branch from the first connecting line.
A spring can be provided by means of which the control valve is biased in the open position. The control valve is thus held in the open position until the difference in the pressure forces acting on the control valve exceeds the spring force. The spring and the hydraulic medium located in the first control line and being under pressure act in the same direction while the counter-force is applied by the hydraulic medium existing in the first connecting line or in the second control line and also being under pressure.
In accordance with a preferred aspect of the present invention an electrical measuring and control unit
1000
is provided by means of which the pressures in the first control line and in the first connecting line and/or in the second control line can be recorded and assessed and by means of which, in dependence on the assessment, a force acting in the open and closed positions of the control valve can be exerted. The actuation of the control valve is thus also possible with the help of measurement value detectors and a corresponding assessment of the measurement results, whereby a working of the control valve identical to the mechanical design can be realized.
It is particularly advantageous if a solenoid valve is provided by means of which the starting control can be locked from the pressure feed. The solenoid valve is opened when the clutch should be actuated, whereby correspondingly communication is manufactured between the pressure feed and the s starting control in accordance with the invention.
In another aspect of the present invention it is provided that the restrictor element and/or the control valve possess a by-pass line in which a check valve is provided by means of which the hydraulic medium can be led out of the pressure store and/or the piston/cylinder unit. When the clutch is disengaged, the hydraulic medium flows from the p
Dilworth & Barrese LLP.
Liebherr Markus
Lorence Richard M.
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