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Title:
VALVE FOR USE WITH A PNEUMATIC CLUTCH ACTUATION SYSTEM
Document Type and Number:
WIPO Patent Application WO/2017/208208
Kind Code:
A1
Abstract:
One embodiment of a pneumatic clutch actuation system includes a valve housing that defines an inlet, an outlet, a first seat, and a second seat with a cavity disposed between the first and second seats. A plunger is mounted to the valve housing and disposed in a first closed position engaged with the first seat when a supply valve is disposed in a closed supply position. A biasing device biases the plunger to the first closed position. The plunger moves from the first closed position to an open position spaced between first and second seats to bleed air through the inlet, the cavity, and the outlet at a bleeding flow rate. The plunger moves from the open position to a second closed position engaged with the second seat when the supply valve is disposed in an open supply position such that a clutch actuator is disposed in an engaged position.

Inventors:
LJØSNE, Knut Tore (Toppåsveien 71A, 1262 Oslo, 1262, NO)
Application Number:
IB2017/053287
Publication Date:
December 07, 2017
Filing Date:
June 02, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
KONGSBERG AUTOMOTIVE AS (Dyrmyrgata 48, P.O. Box 62, Kongsberg, NO-3601, NO)
International Classes:
F16D48/02
Domestic Patent References:
WO2009092395A12009-07-30
Foreign References:
EP1344949A22003-09-17
DE19717486A11998-10-29
EP0344039A11989-11-29
GB2057607A1981-04-01
Other References:
None
Download PDF:
Claims:
CLAIMS

1. A pneumatic clutch actuation system comprising:

a clutch actuator having a pressure housing and an actuator movable within said pressure housing between a first position when said pressure housing receives air at a pressure that is at or above an operational pressure and a second position when said actuator receives air at a pressure that is below said operational pressure;

a supply valve fluidly connected to said clutch actuator, with said supply valve movable between an open supply position for flowing air to said pressure housing of said clutch actuator at a supply flow rate to obtain said operational pressure and move said actuator to said first position and a closed supply position to prevent air from flowing to said pressure housing of said actuator such that said actuator is disposed in said second position;

a valve housing coupled to one of said supply valve and said pressure housing of said actuator, with said valve housing defining a first seat and a second seat with a cavity disposed between said first and second scats, an inlet, and an outlet;

a plunger mounted to said valve housing and disposed in a first closed position engaged with said first seat when said supply valve is disposed in said closed supply position; and

a biasing device continuously biasing said plunger to said first closed position;

said plunger moving from said first closed position to an open position spaced between said first and second seats to bleed air from at least one of said supply valve and said pressure housing and through said inlet, said cavity, and said outlet at a bleeding flow rate below said supply rate such that said clutch actuator remains disposed in said second position when said supply valve is disposed in said closed supply position;

said plunger moving from said open position to a second closed position engaged with said second seat when said supply valve is disposed in said open supply position such that said clutch actuator is disposed in said first position.

2. The clutch actuator of claim 1, wherein said first seat comprises an annular ridge,

3. The clutch actuator of claim 1 , wherein said plunger comprises a first shoulder engaging said first seat when said plunger is disposed in said first closed position, and said first shoulder has a surface deflecting air to move said plunger from said open position to said second closed position.

4. The clutch actuator of claim 3, wherein said valve housing comprises a flow regulating bore having an inner diameter surface^ and said plunger further comprises a first cylindrical portion coupled to said first shoulder and having an outer diameter surface facing said inner diameter surface of said flow regulating bore to define an annular gap between said first cylindrical portion and said flow regulating bore for flowing air through said annular gap when said plunger is disposed in said open position.

5. The clutch actuator of claim 4, wherein said valve housing defines a first guiding bore, and said plunger has a first guiding end sliding along said valve housing within said first guiding bore to hold said cylindrical portion concentrically within said flow regulating bore to define said annular gap.

6. The clutch actuator of claim 5, wherein said first guiding end defines at least one passage fluidly connecting said first guiding bore to said flow regulating bore when said plunger is disposed in said open position.

7. The clutch actuator of claim 6, wherein said first guiding end comprises a tip, and said at least one passage comprises a channel extending diametrically across said tip and fluidly communicating with said first guiding bore, said first guiding end further comprising a neck coupled to said tip and defining at least one annular groove fluidly connected to said channel to flow air from said first guiding bore and through said channel and said groove to said flow regulating bore when said plunger is disposed in said open position.

8, The clutch actuator of claim 7, wherein said plunger defines a plurality of vent notches spaced apart from one another along the surface of said plunger, with said plurality of vent notches fluidly connected to said gap and said cavity to flow air from said gap to said cavity when said plunger is disposed in said open position.

9. The clutch actuator of claim 8, wherein said channel has a longitudinal axis, and each of said plurality of said vent notches is defined by at least one surface arranged parallel with said longitudinal axis to facilitate flow from said channel through said plurality of vent notches.

10. The clutch actuator of claim 8, wherein said channel has a longitudinal axis, and two of said plurality of said vent notches are spaced from the other vent notches relative to said longitudinal axis and smaller than the other vent notches to distribute flow of air around said plunger.

1 1. The clutch actuator of claim 1 , wherein said biasing device comprises a first spring coupled to said plunger to move said plunger to said first closed position when said pressure is below a vent pressure for preventing air from flowing through said cavity and said outlet.

12. The clutch actuator of claim 1 1, wherein said biasing device further comprises a second spring engaging said plunger when said plunger is disposed in one of said open position and said second closed position, with said first and second springs holding said plunger in said open position when said pressure is above said vent pressure and below said operational pressure for flowing air through said inlet, said cavity, and said outlet of said valve housing.

13. The clutch actuator of claim 12, wherein said first and second springs are disposed concentrically about each other and are disposed concentrically about said plunger.

14. The clutch actuator of claim 12, further comprising a spring seat coupled to said second spring such that said second spring continuously biases said spring seat to engage at least one of said valve housing and said plunger.

15. The clutch actuator of claim 14, wherein said spring seat comprises a first side engaging said valve housing when said plunger is disposed in said first closed position and engaging said plunger when said plunger is disposed in one of said open position and said second closed position, and said spring seat further has a second side coupled to said second spring.

16. The clutch actuator of claim 15, wherein said plunger has an outside diameter, said spring seat having an outer diameter that is larger than said outside diameter of said plunger, and said spring seat has an inner diameter that is less than said outside diameter of said head.

17. The clutch actuator of claim 16, wherein said second spring has a spring diameter that is between said inner and outer diameters of said spring seat.

18. The clutch actuator of claim 15, wherein said spring seat further has an outer surface sliding along said valve housing within said cavity when said plunger moves between said open position and said second closed position.

19. The clutch actuator of claim 14, wherein said spring seat is disposed concentrically about said first spring, and said first spring is disposed concentrically about said plunger.

20. The clutch actuator of claim 1 , wherein said valve housing comprises a first housing portion having said first seat and a second housing portion coupled to said first housing portion and having said second seat,

21. The clutch actuator of claim 20, wherein said first housing portion is integrally formed with said supply valve.

22. The clutch actuator of claim 20, wherein said first housing portion is integrally formed with said pressure housing of said clutch actuator.

23. The clutch actuator of claim 1 , wherein said second seat comprises an annular ridge.

24. The clutch actuator of claim 23, wherein said plunger comprises a second shoulder engaging said second seat when said plunger is disposed in said second closed position, and said second shoulder has a surface directing air to said outlet of said valve housing when said plunger is disposed in said open position.

25. The clutch actuator of claim 24, wherein said valve housing defines a second guiding bore, and said plunger has a second guiding end sliding along said valve housing within said second guiding bore to hold said cylindrical portion concentrically within said flow regulating bore to define said annular gap.

26. The clutch actuator of claim 25, wherein said second guiding end defines at least one passage fluidly connecting said cavity to said outlet when said plunger is disposed in said open position.

27. The clutch actuator of claim 26, wherein said second guiding end comprises a tip, and said at least one passage comprises a channel extending diametrically across said tip and fluidly communicating with said second guiding bore and said cavity to flow air from said cavity through said channel to said flow air from said cavity to said outlet when said plunger is disposed in said open position.

28. The clutch actuator of claim 26, wherein said tip comprises at least one detention barb attaching said plunger to said valve housing.

29. A method of bleeding air from a pneumatic clutch actuation system having a clutch actuator, an air supply, a supply valve selectively fluidly connecting the air supply to said clutch actuator, and a bleed valve having a valve housing and a plunger, said method comprising the steps of:

moving the supply valve to a closed supply position;

flowing air from the air supply around the supply valve and to the clutch actuator when the supply valve is disposed in the closed supply position;

biasing the plunger to a first closed position when the pressure of air supplied to the clutch actuator is below a vent pressure;

moving the plunger to an open position when the supply valve is disposed in the closed supply position and the pressure of air supplied to the clutch actuator is at or above the vent pressure and below an operational pressure;

moving the plunger to a second closed position when the supply valve is moved to an open supply position and the pressure of air supplied to the clutch actuator is at or above the operational pressure; and

moving the clutch actuator from a second position to a first position when the pressure of air supplied to the clutch actuator is at or above the operational pressure.

Description:
VALVE FOR USE WITH A PNEUMATIC CLUTCH ACTUATION SYSTEM

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/344,750 filed June 2, 2016, herein incorporated in its entirety.

BACKGROUND OF THE INVENTION

[0002] It is known to provide a pneumatically controlled clutch actuator for actuating components in a powertrain system, such as gears and clutches in a transmission. The clutch actuator typically includes a movable internal piston disposed in a chamber. Leakage can cause a slow pressure buildup in the pressure circuit, until pressure within the chamber reaches an operational pressure causing undesired movement of the clutch actuator to move from a disengaged position to an engaged position followed by undesired shifting of the transmission. As such, it is desirable to reduce or eliminate such pressure buildup.

SUMMARY OF THE DISCLOSURE

[0003] One example of the present invention provides a pneumatic clutch actuation system including a clutch actuator, which has a pressure housing and an actuator. The actuator is movable within the pressure housing between an engaged position when the pressure housing receives air at a pressure that is at or above an operational pressure and a disengaged position when the actuator receives air at a pressure that is below the operational pressure. The system further includes a supply valve fluidly connected to the clutch actuator. The supply valve is movable between an open supply position for flowing air to the pressure housing of the clutch actuator at a supply flow valve is further movable to a closed supply position to prevent air from flowing to the pressure housing of the actuator such that that the actuator is disposed in the disengaged position. A valve housing is coupled to one of the supply valve and the pressure housing of the actuator. The valve housing defines an inlet, an outlet, a first seat, and a second seat with a cavity disposed between the first and second seats. The system has a plunger mounted to the valve housing and disposed in a first closed position engaged with the first seat when the supply valve is disposed in the closed supply position. A biasing device continuously biases the plunger to the first closed position. The plunger moves from the first closed position to an open position spaced between the first and second seats to bleed air from at least one of the supply valve and the pressure housing and through the inlet, the cavity, and the outlet at a bleeding flow rate below the supply rate such that the clutch actuator remains disposed in the disengaged position when the supply valve is disposed in the closed supply position. The plunger moves from the open position to a second closed position engaged with the second seat when the supply valve is disposed in the open supply position such that the clutch actuator is disposed in the engaged position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

[0005] Figure 1 is a schematic view of one embodiment of a pneumatic clutch actuation system having a valve in accordance with the invention for controlling bleeding air from the pneumatic clutch actuation system. [0007] Figure 3 is a cross-sectional view of the valve of Figure 2.

[0008] Figure 4 is an exploded view of the valve of Figure 2, showing the valve including a valve housing and a plunger movable within the valve housing.

[0009] Figure 5 A is an enlarged perspective view of the plunger of Figure 4.

[0010] Figure 5B is top elevation view of the plunger of Figure 5 A.

[0011] Figure 5C is a side view of the plunger of Figure 5A.

[0012] Figure 5D is another side view of the plunger of Figure 5C, illustrating the plunger of Figure 5C rotated 90 degrees.

[0013] Figure 5E is a bottom elevation view of the plunger of Figure 5 A.

[0014] Figure 6A is a cross-sectional view of the valve as taken along a cross-sectional line 6A of Figure 3, illustrating the plunger disposed in a first closed position.

[0015] Figure 6B is a cross-sectional view of the valve of Figure 3, disposed 90 degrees relative to the plunger of Figure 6A.

[0016] Figure 7A is a cross-sectional view of the valve of Figure 3, illustrating the plunger disposed in an open position.

[0017] Figure 7B is a cross-sectional view of the valve of Figure 3, disposed 90 degrees relative to the plunger of Figure 7A.

[0018] Figure 8A is a cross-sectional view of the valve of Figure 3, illustrating the plunger disposed in a second closed position.

[0019] Figure 8B is a cross-sectional view of the valve of Figure 3, disposed 90 degrees relative to the plunger of Figure 8A.

[0020] Figure 9 is an exemplary chart of valve flow for the valve of Figure 2 as a function DETAILED DESCRIPTION OF THE INVENTION

[0021] With reference to the Figures, wherein like numerals indicate like parts throughout the several views, a pneumatic clutch actuation system 100 includes a valve 102 to control pressure in a clutch actuator 104 for a powertrain component (not shown). More specifically, the valve 102 can bleed air from the pneumatic clutch actuation system 100 and prevent a leak or slow buildup of pressure from inadvertently causing the clutch actuator to actuate the powertrain component. In one embodiment, the powertrain component can be a transmission, and the clutch actuator 104 can be pneumatically controlled to move a component of the transmission, such as gears or clutches (not shown).

[0022] Put another way, in the transmission, leakage in a supply valve can cause a slow pressure buildup in the pneumatic clutch actuation system, followed by undesired shifting of the clutch actuator between a disengaged position and an engaged position. A rapid pressure increase in the pneumatic clutch actuation system is necessary to activate the clutch actuator. In order to prevent the slow pressure build up, excess pressure must be released from the pneumatic clutch actuation system 100 through the valve 102; however, the pressure released from the pneumatic clutch actuation system 100 must not be greater than the pressure required to actuate the clutch actuator. The valve 102 is configured to either seal the system 100 or to vent system 100. In the vented configuration, the fluid may pass through the valve 102 and in the sealed configuration, fluid is restricted from flowing through the valve 102. The valve configuration depends on pressure in the system 100. When pressure in the system 100 is below the vent pressure A, the valve 102 will be sealed. When pressure in the system 100 is below the operation pressure B and the operation pressure B, the valve 102 will be sealed. Advantageously, the valve 102 will be sealed at low pressures, which allows the system 100 to have a negative or vacuum pressure.

[0023] Referring to Figure 1, one embodiment of the pneumatic clutch actuation system 100 includes an air supply 106 and the clutch actuator 104 having a pressure housing 108 and an actuator 110 movable within said pressure housing 108. The actuator is movable between an engaged position when the pressure housing 108 receives air from the air supply 106 at a pressure that is at or above an operational pressure and a disengaged position when the actuator 110 receives air at a pressure that is below the operational pressure.

[0024] The pneumatic clutch actuation system 100 can further include a supply valve 102 fluidly connected to the clutch actuator 104. The supply valve 102 can be movable between an open supply position for flowing air from the air supply 106 to the pressure housing 108 of the clutch actuator 104 at a supply flow rate to obtain the operational pressure and move the actuator 110 to the engaged position. The supply valve 102 can be further movable to a closed supply position to prevent air from flowing from the air supply 106 to the pressure housing 108 of the actuator 110 such that the actuator 110 is disposed in the disengaged position. As mentioned above, the pneumatic clutch actuator system 100 can leak air around the supply valve 102 to the pressure housing 108, which could inadvertently increase the pressure of the air within the pressure housing 108. The leakage of air is schematically shown in Figures 1 and 7A as passage 112. Passage 112 can be caused by a number of different factors, including wear of certain components of the supply valve.

[0025] The valve 102 can include a valve housing 114 coupled to the supply valve 102 or the pressure housing 108 of the actuator 110. The valve housing 114 can define an inlet 116, an second seats 120, 122. The valve housing 114 includes a first housing portion 126 having the first seat 120 and a second housing portion 128 coupled to the first housing portion 126 and having the second seat 122. The first housing portion 126 can define a socket 130 with an internal threaded fastener 132, and the second housing portion 128 can define a plug 134 with an external threaded fastener 136 engaging the internal threaded fastener 132 of the socket 130. The first housing portion 126 can have a groove 138 and a seal 139 disposed within the groove 138 and sandwiched between the first and second housing portions 126, 128. Moreover, the first housing portion 126 can be an integral part of the supply valve 102 or an integral part of the pressure housing 108 of the clutch actuator 104. However, it is contemplated that the first housing portion can be a component of the valve housing that is separate from the supply valve and pressure housing and mounted to either one of the supply valve or the pressure housing.

[0026] Referring to Figures 1 and 3, the valve housing 114 can define a plurality of passages fluidly connected with one another for flowing air from the inlet 116 to the outlet 118 when the valve 102 is opened. In particular, the valve housing 114 can include a first guiding bore 140 fluidly connected to the inlet 116 for flowing air from the inlet 116 to the first guiding bore 140. The first seat 120 can be an annular ridge 142 coupled to the valve housing 114 and surrounding the first guiding bore 140. In other embodiments, the first seat can be a seal or O-ring mounted to the valve housing or other suitable seats. The valve housing 114 may further define a flow regulating bore 144 fluidly connected to the first guiding bore 140 to flow air from the first guiding bore 140 to the flow regulating bore 144 when the valve 102 is open. The cavity 124 can be fluidly connected to the flow regulating bore 144 to flow air from the flow regulating bore 144 to the cavity 124 when the valve 102 is open. In addition, the valve housing 114 can further include second guiding bore 146, which is in turn fluidly connected to the outlet 118 for flowing air to through the outlet 118. The second seat 122 can be an annular ridge 148 coupled to the valve housing 114 and surrounding the second guiding bore 146. Similar to the first seat, other embodiments of the second seat may be an O-ring mounted to the housing or any other suitable seat.

[0027] Referring to Figures 6A and 6B, the valve 102 can further include a plunger 150 mounted to the valve housing 114 and disposed in a first closed position engaged with the first seat 120 when the supply valve 102 is disposed in the closed supply position. In this embodiment, the plunger 150 can have a first shoulder 152 engaging the first seat 120 when the plunger 150 is disposed in the first closed position. This first shoulder 152 can have a frustroconical surface 154 deflecting air radially outward to facilitate moving the plunger 150 along a longitudinal axis 156 of the cavity 124 from the open position to the second closed position. However, it is contemplated that the first shoulder can instead be a planar annular flange or any other suitable structure that engages the first seat to prevent the flow of air through the valve.

[0028] Referring to Figures 7 A and 7B, the plunger 150 is movable within the valve housing 114 from the first closed position to an open position spaced between the first and second seats 120, 122 to bleed air from the supply valve 102 and/or the pressure housing 108 through the inlet 116, the cavity 124, and the outlet 118 at a bleeding flow rate below the supply rate, such that the clutch actuator 104 remains disposed in the disengaged position when the supply valve 102 is disposed in the closed supply position. The plunger 150 can have a first guiding end 158 sliding along the valve housing 114 and hold the plunger 150 concentrically within the valve housing 114 to maintain passages defined between the plug 134 and the valve housing 114 and allow the without the plunger becoming misaligned and obstructed from moving to any one of the positions. The first guiding end 158 can define at least one passage 160 fluidly connecting the first guiding bore 140 to the flow regulating bore 144 when the plunger 150 is disposed in the open position. The first guiding end 158 can comprise a tip 162, and the passage 160 can comprise a channel 164 extending diametrically across the tip 162 and fluidly communicating with the first guiding bore 140. The first guiding end 158 can further include a neck 166 coupled to the tip 162 and defining one or more annular grooves 168 fluidly connected to the channel 164 to flow air from the first guiding bore 140 and through the channel 164 and groove 168 to the flow regulating bore 144 when the plunger 150 is disposed in the open position. The flow regulating bore 144 of the valve housing 114 can have an inner diameter surface 170, and the plunger 150 can further comprise a first cylindrical portion 172 coupled to the first shoulder 152 and having an outer diameter surface 174 facing the inner diameter surface 170 of the flow regulating bore 144 to define an annular gap 176 between the first cylindrical portion 172 and the flow regulating bore 144 for flowing air through the annular gap 176 when said plunger is disposed in the open position. The annular gap 176 is remains constant when the plunger 150 moves between the first closed position, the open position, and the second closed position because the first guiding end 158 and the first guiding bore 140 hold the plunger 150 concentrically within the valve housing 114 as the plunger 150 moves between the first closed position, the open position, and the second closed position.

[0029] The plunger 150 can define a plurality of vent notches 178 spaced apart from one another along the surface of the plunger 150, with the vent notches 178 being fluidly connected to the annular gap 176 and the cavity 124 to flow air from the gap 176 to the cavity 124 when the plunger 150 is disposed in the open position. The channel 164 can have a longitudinal axis 156, respect to the longitudinal axis 156 to facilitate flow from said channel 164 through the vent notches 178. Also in this embodiment, two of the vent notches 182 are spaced from the other vent notches 184 relative to the longitudinal 156 and smaller than the other vent notches 184, which are disposed farther from the channel, in order to distribute the flow of air around the plunger 150 into the cavity 124 when the plunger 150 is moved to the open position. When the plunger is in the open position, the first shoulder 152 is spaced apart from the first seat 120, and the plunger 150 has a second shoulder 186 spaced apart from the second seat 122 to direct flow from the cavity toward the outlet 118. The second shoulder 186 can have a frustroconical surface 188 directing air radially inward to the outlet 118 of the valve housing 114 when the plunger 150 is disposed in the open position. The plunger 150 can have a second guiding end 190 sliding along the valve housing 114 within the second guiding bore 146 to facilitate the first guiding end 158 and first guiding bore 140 with holding the cylindrical portion 172 of the plunger 150 concentrically within the flow regulating bore 144 and define a constant annular gap 176 as the plunger 150 moves between the first closed position, the open position, and the second closed position. The second guiding end 190 defines one or more passages 192 fluidly connecting the cavity 124 to the second guiding bore 146 and the outlet 118 when the plunger 150 is disposed in the open position. The second guiding end 190 can include a tip 194, and the passages 192 can comprise a channel 196 extending diametrically across the tip 194 and fluidly communicating the cavity 124 and second guiding bore 146 with one another and to flow air from the cavity 124 through the channel 164 to the outlet 118 when the plunger 150 is disposed in the open position. The tip 194 is slidably secured to the valve housing 114. In one embodiment, the tip 194 comprises at least one detention barb 198 attaching the plunger 150 to the valve housing 114 and extending beyond a diameter of the second guiding bore 146 to engage the valve housing 114 and prevent the plunger 150 from being removed from the valve 102.

[0030] The valve 102 can further include a biasing device 200 continuously biasing the plunger 150 to the first closed position. In this embodiment, the biasing device 200 comprises a first spring 202 coupled to the plunger 150 to move the plunger 150 to the first closed position when the pressure is below a vent pressure for preventing air from flowing through the cavity 124 and the outlet 118. The biasing device 200 can further comprise a second spring 204 engaging the plunger 150 when the plunger 150 is disposed in the open position or the second closed position, with the first and second springs 202, 204 holding the plunger 150 in the open position when the pressure is above the vent pressure and below the operational pressure for flowing air through the inlet 116, the cavity 124, and the outlet 118 of the valve housing 114. The second spring 204 can be disposed concentrically about the first spring 202, and the first spring 202 is disposed concentrically about the plunger 150.

[0031] The valve 102 can further include a spring seat 206 coupled to the second spring 204 such that the second spring 204 continuously biases the spring seat 206 to engage at least one of the valve housing 114 and the plunger 150. The spring seat 206 can have a first side 208 engaging the valve housing 114 when the plunger 150 is disposed in the first closed position and engaging the plunger 150 when the plunger 150 is disposed in one of the open position and the second closed position, and the spring seat 206 further has a second side 210 coupled to the second spring 204.

[0032] The plunger 150 has an outside diameter, with the spring seat 206 having an outer diameter that is larger than said outside diameter of said plunger, and the spring seat has an inner diameter that is between the inner and outer diameters of the spring seat 206. The spring seat 206 further has an outer surface 212 sliding along the valve housing 114 within the cavity 124 when the plunger 150 moves between the open position and the second closed position. The spring seat 206 is disposed concentrically about the first spring 202, and the first spring 202 is disposed concentrically about the plunger 150.

[0033] Referring to Figures 8A and 8B, the plunger 150 can move from the open position to the second closed position engaged with the second seat 122 when the supply valve 102 is moved to the open supply position such that the air flows from the air supply 106 to the clutch actuator 104 at the supply flow rate to obtain the operational pressure and dispose the clutch actuator 104 in the engaged position.

[0034] One embodiment of a method for operating the pneumatic clutch actuation system 100 of Figures 1-9 begins with the step of moving the supply valve 102 to the closed supply position, and moving the exhaust valve 102 to the open exhaust position to decrease pressure within the pressure housing 108 of the clutch actuator and disengage the clutch.

[0035] As mentioned above, air can flow through the passage 112 formed in or around the supply valve 102 to the pressure housing 108 of the clutch actuator 104, when the supply valve remains in the closed supply position. The flow or leak of air into the pressure housing 108 can build up pressure within the pressure housing 108. As also mentioned above, the passage 112 may be formed by a worn or damaged seal of the supply valve 102 or other worn or defective component in the supply valve 102, such that air flows through the passage 112 while the supply valve remains in the closed supply position. When the pressure of the air supplied to the clutch actuator 104 remains below the vent pressure, the biasing device 200 holds the plunger 150 in the first closed supplied to the clutch actuator 104 builds to or above the vent pressure and below the operational pressure, the plunger 150 moves from the first closed position to the open position and air flows from the inlet 116 through the cavity 124 and the outlet 118 to bleed air from the pneumatic clutch actuation system and prevent unintentional activation of the clutch actuator 104. When the supply valve 102 is moved to the open supply position and the pressure of air supplied to the clutch actuator 104 is at or above the operational pressure, the plunger 150 moves from the open position to the second closed position to in turn move the clutch actuator 104 from the disengaged position to the engaged position.

[0036] Referring to Figure 9, it is to be appreciated that pressure in the pressure circuit controls the position of the plunger. When pressure in the pressure circuit is below the vent pressure A, the plunger will be in the first position and the valve assembly will be sealed. In the first position, the valve assembly is sealed, which allows for a vacuum in the pressure circuit. When pressure in the pressure circuit is below the operation pressure B and above the vent pressure A, the plunger will be in the second position and the valve assembly will be vented. When pressure in the pressure circuit is above the operation pressure B, the plunger will be in the third position and the valve assembly will be sealed.

[0037] The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.