Fluid operated clutch control system having latch member

Abstract: Provided is an improved fluid operated clutch control system having a latch member operable to lock the clutch in a selected condition of engagement or disengagement when the fluid pressure falls below a predetermined minimum value. In one embodiment a system (100) is provided in which a latch member (26) is controlled by fluid pressure in a channel (36) in a stationary wall housing (10). In another embodiment, a system (200) is provided in which a latch member (62) is controlled by the combination of fluid pressure sensed by a sensor (64) and the energization and de-energization of a solenoid (60) and, in yet another embodiment, a system (300) is provided with a latch member (62) that is controlled by the energization and de-energization of a solenoid (60).

Description: INTRODUCTION This invention relates generally to a fluid operated clutch control system operable to enable engagement and disengagement between a driver member and a driven member such as a vehicular engine and change gear transmission and more particularly to an improved clutch control system that includes a latch member operable to lock the clutch in a preselected condition when the fluid pressure is below a predetermined minimum value. BACKGROUND OF THE INVENTION A variety of fluid operated clutch control systems for controlling engagement and disengagement of the vehicle master friction clutch between a driver member and driven member, such as a vehicular engine and change gear transmission, have been developed over past years. Early examples of such systems are disclosed in United States Patents 1,317,029; 2,137,961; 2,137,939 and more recent examples of such systems are disclosed in United States Patents 3,548,981; 3,719,102; 3,799,309; 4,236,617 and 4,448,293, the disclosures of all of which are incorporated herein by reference. Locking mechanisms have been employed to a lesser extent in the past to lock vehicle components in selected positions upon the occurance of one or more predetermined conditions such as the pressure actuated ratchet used in the air brake control system disclosed in United States Patent 2,099,453; the fluid actuated latch used in the power shifting mechanism disclosed in United States Patent 2,180,154; the ratchet member used in the power system for operating control members disclosed in United States Patent 2,932,282, and the latch member used in the automatic clutch control system disclosed in United States Patent 4,729,462, the disclosure of all which are incorporated herein by reference and the last of which is owned by the assignee of the present invention. As disclosed in the above described prior art, the latch members have characteristically been devices that engage external members of the control system whereas the present invention provides a latching member that is operable to enter directly into the fluid chamber containing the pressurized fluid that controls the clutch condition and is thus advantageously effective in locking the clutch in a preselected condition when the fluid pressure is below a predetermined minimum value so as, for example, to prevent the engine from driving the transmission when for some reason the fluid pressure has dropped below the predetermined minimum value and the vehicle is traveling at low speed or alternately, to prevent the engine from disengaging from the transmission to assure engine braking when the vehicle is decending a hill. US-A-4 116 113 proposes a control system for locking a brake piston, which is otherwise definitive of the precharacterizing portion of Claim 1. FR-A-2 402 805 discloses an electromagnetic clutch requiring two external dedicated pneumatic sources to lock the clutch actuator in either of two positions. Accordingly, it is an object of this invention to provide an improved fluid operated clutch control system having a latch member operable to lock the clutch in a preselected condition when the fluid pressure is below a predetermined minimum value. It is another object of this invention to provide an improved fluid operated clutch control system having a latch member that enters the pressurized fluid chamber actuating the clutch and is responsive to the same pressurized fluid to lock the clutch in a preselected condition when the fluid pressure is below a predetermined minimum value. The invention is set out in Claim 1. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a central cross-sectional view of a clutch control system 100 of the invention that utilizes pressured fluid to actuate a latch member 26; and FIGURE 2 is a partial central cross-sectional view of head 74 of a piston rod 72 having a tapered surface 88 engagable with the tapered surface 90 on a latch member 86. DESCRIPTION OF SOME PREFERRED EMBODIMENTS In FIGURE 1, clutch 2 is operable to engage and disengage a drive member such as a vehicular engine to a driven member such as a transmission in response to pivotal movement of linkage arm 4 between the two conditions. Linkage arm 4 is pivoted by reciprocal movement of a movable member such as by the operable connection between arm 4 and piston rod 6 having an enlarged head 8 movably disposed in chamber 12 contained within a surrounding stationary housing wall 10. Head 8 is provided with a suitable fluid seal such as a resilient "O" ring 16 that fluid sealingly engages the inner surface of wall 10 of the housing member. Pressurized fluid referenced by numeral 42 is introduced into chamber 12 through inlet 41 in wall 10 which also includes a vent opening 18 to prevent air from being compressed in chamber 12 to the right of head 8 when head 8 moves towards the viewer's right. A plate 22 is secured to wall 10 within chamber 12. Plate 22 has an opening through its center through which piston rod 6 is able to reciprocably move. A seal 23 is provided in plate 22 for sealing engagement with rod 6. Another seal 21 is provided at the outside diameter of plate 22 for sealing engagement with housing 10. A plate 24 is fixedly secured to piston rod 6 in spaced-apart relationship to plate 22. First resilient biasing means, such as a coiled spring 20, is disposed about piston rod 6 between plates 22 and 24 with the result that piston rod 6 is urged towards the viewer's left to move clutch 2 into the engaged condition whenever fluid pressure in chamber 12 is below a predetermined minimum value which, in part can be controlled by the spring constant selected for spring 20. The engagement and disengagement of clutch 2 is controlled by the introduction of pressurized fluid into chamber 12 through inlet 41 as previously described. Inlet 40 may, of course, also act as an outlet to enable the pressurized fluid to exit chamber 12 according to the means by which the pressurized fluid is being controlled such as by a speed signal that controls optimum change gear shifting points. Hydraulic circuits for controlling engagement and disengagement of clutches are well known and are thus not described in detail herein except to the extent that chamber 12 may have more than one entry for receiving and/or dumping pressurized fluid with various flow restricting orifices for modulating the flow. Wall 10 has an opening 25 therethrough and piston head 8 is provided with engagement means preferably in the form of an open-sided groove 14 therein facing towards and registerable with opening 25. An elongate portion of a latch member 26 is movably disposed in opening 25 and a "U" cup shaped portion thereof is disposed in chamber 34 enclosed by a surrounding housing wall 28 that is secured to wall 10. Latch member 26 is thus reciprocally movable in chamber 34 and in opening 25. A second resilient biasing means, such as coiled spring 30, is disposed in chamber 34 within the "U" cup shaped portion of latch member 26 and one end engages a stop plate 32 and the opposite end engages the bottom of the "U" cup shaped section of latch member 26. As a result latch member 26 is urged downwardly as viewed in FIGURE 1 so that the lower end of the portion of latch member 26 extending through opening 25 will slide along the outer surface of piston head 8 and enter groove 14 to lockingly secure the movable member at a preselected position determined by the location that latch member 26 enters chamber 12. A fluid channel 36 extends through wall 10 providing fluid communication between chamber 12 and an end of a pin 38 that is movably disposed in a continuation of channel 36 in wall 10 that extends in a radially outwardly direction from chamber 12. The opposite end of pin 38 is engagable with a contact surface 40 of latch member 26 facing towards chamber 12. Pin 38 is reciprocally movable in channel 36 and preferably includes a fluid seal such as a resilient "O" ring 37 in its outer surface to prevent fluid from leaking past pin 38. Although the use of pin 38 is preferred, it can be omitted in favor of including a fluid chamber beneath the "U" cup shaped portion of latch member 26 which is then itself preferably provided with fluid seals such as a resilient "O" ring in the outer surface of the "U" cup shaped portion to prevent fluid from exiting into chamber 34. In operation, when the fluid pressure in chamber 12 is above a predetermined minimum value, the equivalent pressure in channel 36 urges pin 38 into engagement with contact surface 40 and overcomes the resilient biasing force of spring 30 and moves latch member 26 upwardly so that piston head 8 (and rod 6) are able to reciprocate within chamber 12 according to the instruction being given on whether to engage or disengage the clutch. However, when the fluid pressure falls below the predetermined minimum value, the biasing force of spring 30 overcomes the force of pin 38 and urges the end of latch member 26 into groove 14 in piston head 8 which is moved into registration therewith by spring 20. Thus, although linkage arm 4 is shown in FIGURES 1 and 2 in a neutral condition for illustrative purposes, the axial location of opening 25 and the axial length of piston head 8 as well as the selection of spring constants for springs 20 and 30 will enable the latch member to lockingly engage the engagement means in piston head 8 at a location at which the clutch is in a selected one of an engaged or a disengaged condition when the fluid pressure falls below a predetermined minimum value. FIGURE 2 shows a preferred feature on piston head 74 having piston rod 72 extending therefrom and moveably disposed in chamber 80 enclosed by surrounding housing wall 78. Piston head 74 is essentially the same as piston head 8 previously described. It has latch member engagement means in the form of annular groove 76 facing towards the inner surface of wall 78 that is registerable with an opening 84 through wall 78 through which a latch member 86 is reciprocally moveable. Latch member 86 is operable to lockingly engage groove 76 and lock piston head 74 a preselected position in the manner hereinbefore described. Piston head 74 includes a tapered surface 88 adapted to engage and urge latch member 86 outwardly from chamber 80 as it moves towards the viewer's right. Such is of advantage in preventing latch member 86 from dropping down into chamber 80 in the space between the end of head 74 and the end of housing- wall 78 towards the viewer's right. Preferably the end of latch member 86 that extends into chamber 80 also has a tapered surface 90 that is adapted to engage tapered surface 88 of head 74 to enhance the movement of latch member 86 outwardly from chamber 80. FIGURE 2 also illustrates that the moveable member such as piston head 84 may have more than one open-sided latch member engagement groove such as groove 76' that is spaced apart from groove 76 such that latch member 86 is able to hold the clutch in either the engaged or the disengaged condition according to the groove selected.

Claims: A control system (100) for a fluid operated device (2) of the type including linkage (4) operable to effect a condition of disengagement or engagement thereof, said system including first resilient biasing means (20) operatively connected to the linkage (4) and a movable member (8,74) actuated by pressurized fluid and having one end disposed within a fluid chamber (12,80) contained within a stationary housing wall (10,78) and operably connected to the linkage (4), said system being operable such that the first resilient biasing means (20) is adapted to cause the linkage to effect a selected condition of disengagement or engagement of the clutch (2) and the movable member (8,74) is adapted to correspondingly allow the linkage (4) to effect the selected condition of disengagement or engagement of the clutch when the movable member (8,74) is actuated by fluid pressure operable to create a force less than a minimum predetermined by the first biasing means (20), and means for latching the movable member (8,74) at at least one preselected position when the fluid pressure falls below a predetermined minimum value, said latching means comprising : an opening through the housing wall; at least one engagement means (14,76) on the movable member facing towards the housing wall and being registrable with the housing wall opening; a latch member (26,86) extending through the housing wall opening and being lockingly engageable with the movable member engagement means at the preselected position; and second resilient biasing means (30) operable to urge the latch member (26,86) into engagement with the movable member engagement means (14,76) in registration therewith; said latching means being operable such that when the fluid pressure in the chamber is above the predetermined minimum the resultant force upon the latch member (26,86) is operative to overcome the second resilient biasing means (30) and prevent the latch member from engaging the movable member engagement means; and when the fluid pressure is below the predetermined minimum, the second resilient biasing means is operable to urge the latch member into engagement with the movable member engagement means and thus to lock the movable member (8,74) at the preselected position, and said control system being characterized by, for use where the fluid-operated device is a clutch: a contact surface (40) on the latch member (26) facing towards the chamber (12); a channel (36) extending through the housing wall (10) between the fluid chamber (12) and the contact surface (40); and a pin (38) movably disposed between the channel (36) and the latch member contact surface (40), said pin being operable to engage said contact surface and impart a force thereagainst in opposition to the second resilient biasing means (30); said latching means being operable such that, when the fluid pressure in the channel (36) is above the predetermined minimum value, the resultant force of the pin (38) against the contact surface (40) is effective to overcome the second resilient biasing means and prevent the latch member from engaging the movable member engagement means (14) and, when the fluid pressure in the channel between the chamber (12) and the pin is below the predetermined minimum value, the second resilient biasing means is not overcome, but is operable to urge the latch member into engagement with the movable member at the preselected position. The system of Claim 1 wherein the movable member engagement means is an open-sided groove (14). The system of Claim 1 or 2 wherein the movable member (8) is a piston. The system of Claim 1,2 or 3 wherein the first resilient biasing means is a spring. The system of Claim 1,2 or 3 wherein the first and second resilient biasing means are springs. The system of any of Claims 1 - 5 wherein the movable member includes a tapered surface (88) operable to urge the latch member outwardly from the fluid chamber upon engagement therewith. The system of Claim 6 wherein the latch member includes a tapered surface (90) engagable with the movable member tapered surface. The system of any of Claims 1 - 7 wherein the movable member engagement means is more than one open-sided groove (76).

Inventors: BRAUN EUGENE RALPH, BRAUN, EUGENE RALPH
Applicants: EATON CORP, EATON CORPORATION
Application year: 1991
Main classification: F16D25
IPC codes: F16H63, B60T17, F16D25, F16D48, F15B15