Machine element or mechanism – Gearing – Interchangeably locked
Patent
1997-03-17
1998-11-17
Wright, Dirk
Machine element or mechanism
Gearing
Interchangeably locked
F16H 6128
Patent
active
058362070
DESCRIPTION:
BRIEF SUMMARY
This invention relates to ratio selector mechanisms and in particular to such mechanisms for the selection of the operative ratio in a vehicle transmission.
Selector mechanisms, hereinafter referred to as bearing "of the type specified", are known in which a fluid pressure operated actuating means operates synchromesh units in an associated synchromesh vehicle transmission.
It is an object of the present invention to provide an improved from of selector mechanism of the type specified.
Thus according to the present invention there is provided a selector mechanism of the type specified in which the operating pressure of the actuating means is varied during selection of a given ratio in the associated transmission or dependant on the ratio being selected in the associated transmission.
For example, the operating pressure may be lowered when selecting the higher ratios of the associated transmission.
In one form of the invention the actuating means comprises a first fluid pressure operated actuator which moves a selector member in a first direction to engage one of a number of ratio shift rails and a second fluid pressure operated actuator which moves the selector member in a second direction to longitudinally displace the engaged shift rail to engage an associated selected ratio.
The level of fluid pressure applied to the second actuator may be varied dependent on the position of the first actuator.
Using such an arrangement the pressure applied to the second actuator (which determines the force used in actually engaging the selected ratio) can be lowered when the first actuator is in engagement with the selector rail(s) associated with the higher ratios of the associated vehicle transmission. This is particularly advantageous in synchromesh transmissions where the synchromesh units associated with the higher ratios are normally of a smaller diameter and therefore less powerful as they have a small speed differential to accommodate.
In a preferred arrangement the level of pressure supplied to the second actuator may be controlled by a valve member which acts against a bias force which is varied in dependence on the position of the first actuator.
Conveniently the above arrangement can be provided by an abutment which moves with the first actuator and which bears on a spring which biases the valve member towards a closed position, movement of the first actuator thus varying the effective bias force of the spring.
In an alternative arrangement pressure is supplied to the actuating means via a master control valve which operates as a solenoid-operated proportional pressure regulating valve which outputs fluid at a pressure proportional to a signal (solenoid current) issued to an electronic control means in accordance with predetermined transmission or vehicle operating criteria.
In a still further alternative arrangement the master control valve may be a solenoid-operated proportional flow valve and a pressure transducer is provided which senses the pressure level supplied to the actuating means and whose output is fed to an electronic control means which issues signals to the solenoid of the master control valve to control the actuating means pressure in accordance with predetermined transmissin or vehicle operating criteria.
The advantage of such electronically controlled arrangements are that the pressure supplied to the selector actuators can be controlled by the master control valve not only in dependence on the ratio to be engaged but also in accordance with additional criteria such as: a given transmission which are of a different design to other synchros used in the same transmission; could be arranged to be higher than the transmission member sustain permanently but which might be required during kickdown in a fully automated transmission which used synchromesh units; of operation of the associated transmission. For example, if the transmission is operating in "sport" mode quicker and noisier shifts are acceptable than when operating in for example, an "economy" or "winter" mode, and cycle. For example
REFERENCES:
patent: 5138905 (1992-08-01), Kouno
patent: 5224392 (1993-07-01), Hutchison et al.
patent: 5231895 (1993-08-01), Stine
patent: 5697251 (1997-12-01), Lorriette et al.
Harries David Anthony
Spooner John
Willows Mark Stanley
Germain Lee A.
Kongsberg Techmatic UK Limited
Milliken Paul E.
Wright Dirk
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