Vehicle differential lock disengagement bypass

Abstract

A method and system for bypassing a control valve that would otherwise disengage differential and/or inter-axle locking means. The bypass is achieved by a valve that can be actuated by a vehicle condition change.

Claims

1. A bypass system for use with a disengagement system for a differential lock in a vehicle having a selectively lockable differential, the differential lock powered by a power fluid selectively allowed by a disengagement control valve, the bypass system comprising: a bypass valve for receiving the power fluid alternatively from the disengagement control valve in a first position and a power fluid source in a second position; a biasing member for biasing the bypass valve in the first position; a bypass valve actuator for switching the bypass valve from the first position to the second position; and power fluid transfer lines for supplying the power fluid to the disengagement control valve and the bypass valve; such that in the first position, the bypass valve allows unimpeded flow of the power fluid between the disengagement control valve and the differential lock; and in the second position, the bypass valve blocks flow of the power fluid between the disengagement control valve and the differential lock and thereby prevents disengagement of the differential lock by the disengagement control valve while allowing flow of the power fluid directly from the power fluid source to the differential lock.

2. The system of claim 1 wherein the disengagement system disengages the differential lock in response to a low-traction event.

3. The system of claim 1 wherein the disengagement control valve comprises a solenoid valve capable of controlling flow of the power fluid to the differential lock.

4. The system of claim 1 wherein the power fluid is a pressurized gas.

5. The system of claim 1 wherein the bypass valve actuator moves the bypass valve to the second position by introduction of the power fluid to the bypass valve actuator of the valve.

6. The system of claim 5 wherein the introduction of the power fluid to the bypass valve actuator occurs in response to a vehicle condition change.

7. The system of claim 6 wherein the vehicle is a road/rail vehicle and the vehicle condition change is actuation of air bags during conversion of the road/rail vehicle to a rail mode of vehicle operation.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the accompanying drawings, which illustrate an exemplary embodiment:

(2) FIG. 1 is a simplified schematic view of a bypass system in the un-actuated position; and

(3) FIG. 2 is a simplified schematic view of the bypass system of FIG. 1 in the actuated position.

(4) An exemplary embodiment of the method and system of the present disclosure will now be described with reference to the accompanying drawings.

DETAILED DESCRIPTION

(5) A pneumatic control system is described in the following, but it will be clear to those skilled in the art that the bypass method and system of the present disclosure could be applied with any other suitable system including a hydraulic control system. Only those parts or components of the vehicle systems that are necessary for an understanding of the present disclosure will be described herein, as those skilled in the art will fully understand the broader mechanical and operational context of the bypass system of the present disclosure and its application in particular situations.

(6) In prior art systems, a solenoid valve is inserted in the air feed line between the air source and the differential lock and inter-axle lock (the differential lock and inter-axle lock collectively referred to herein as the differential lock or lock). The solenoid therefore acts as a gate to alternatively allow or restrict air flow to the lock depending on the solenoid design. As explained above, such solenoids are designed to respond to ABS initiation (low-traction events) to block air flow to the locks, thereby disengaging the locks, and then subsequently allow air flow back to the locks once the trigger event has ceased.

(7) Turning now to FIGS. 1 and 2, a bypass system 10 is illustrated. The method and system will be described with reference to these Figures.

(8) In the bypass system 10, the factory standard control valve 12 (a solenoid) is in place between the air source 16 and the output line 44 to the differential locks. The control valve 12 is fed by a feed line 18 from the air source 16 and comprises an inlet 20 and an outlet 22, the outlet 22 feeding air to an output line 28. This portion of the illustrated embodiment is similar to the prior art design, and the control valve 12 is wired to receive signals from the ABS in a conventional manner that will not be described further herein. The bypass system 10 also comprises a bypass valve 14, which in the illustrated embodiment is an air piloted three-port air valve. The bypass valve 14 is operated remotely by pneumatic signals provided by pressurized gas, as will be explained below.

(9) The bypass valve 14 comprises upper and lower blocks 24, 26. The upper block 24 comprises a closed port 34 and an open port 36, while the lower block 26 comprises a closed port 30 and an open port 32. The bypass valve 14 further comprises an actuator 38 that is controlled by means of an air bag air pressure source 40 and pressurized air supply line 42, the actuator 38 of conventional design.

(10) The bypass valve 14 is biased by means of a spring 46 into a first position, which is illustrated in FIG. 1, and there is no counteracting pressure 40 through supply line 42 to signal the actuator 38 to switch the bypass valve 14 to the second position. In this first position, pressurized air is supplied to the differential locks through the control valve 12. Pressurized air is provided by the air source 16 and is forced through the feed line 18. As the lower port 30 of the lower block 26 is closed, the pressurized air must flow to the control valve 12 through the inlet 20. At this point, the control valve 12 will either allow the pressurized air to flow through the outlet 22, output line 28 and open port 32 of the lower block 26 to the output line 44 to the locks (in which case the differential is locked) or will block the flow of pressurized air to the locks (in which case the differential is unlocked). In the exemplary embodiment, the control valve 12 is configured to receive a signal from the vehicle ABS, such that the control valve 12 blocks air flow in response to initiation of an ABS event and subsequently allows air flow in response to a signal indicating cessation of the ABS event. In the first position, then, the control valve 12 determines on an automatic basis whether the locks will be engaged or disengaged.

(11) In a road/rail vehicle, this first position would normally be preferred when the vehicle is in the road transport mode of operation. In the rail transport mode of operation, however, this would be problematic, as described above. The bypass valve 14 is accordingly capable of shifting to a second position as described below.

(12) The bypass valve 14 can be shifted into the second position, as illustrated in FIG. 2. When it is desired to operate a road/rail vehicle in a rail transport mode of operation, for example, air bags are inflated to lower the rail gear relative to the vehicle body and push the vehicle body upwardly, such that the rubber tires are elevated and the rail wheels can engage the rails. Inflating the air bags 40 sends pressurized air through the supply line 42 to the actuator 38 of the bypass valve 14, thereby countering the force of the spring 46 and switching the bypass valve 14 to the second position. For other vehicles, other means of signalling the actuator 38 would be appropriate and within the knowledge of those skilled in the art.

(13) In the second position, the upper block 24 is now engaged. Pressurized air is provided by the air source 16 and is forced through the feed line 18, but the lower port 36 is open and pressurized air can therefore flow directly through the bypass valve 14 to the output line 44 for the differential locks. The upper port 34 is closed, with the result that pressurized air fed through the feed line 18 and inlet 20 to the control valve 12 can pass through the outlet 22 into the output line 28 but is blocked from passing through the bypass valve 14. Therefore, in the second position, the effect of the control valve 12 is negated such that it does not impact pressurized air supply to the locks, while a direct open supply of pressurized air to the locks is supplied through the open port 36. Pressurized air is accordingly constantly supplied to the locks during this bypass phase, such that the locks remain engaged even in the event of a low-traction event triggering the control valve 12 flow restriction.

(14) When the bypass valve 14 is switched back to the first position, the control valve 12 once again can automatically allow or restrict pressurized air supply to the locks, as shown in FIG. 1. In the case of a road/rail vehicle, for example, this would occur when the vehicle was converted from a rail transport mode of operation to a road transport mode of operation by deflation of the air bags and release of the pressure on the actuator 38.

(15) The foregoing is considered as illustrative only of the principles of the invention. The scope of the claims should not be limited by the exemplary embodiment set forth in the foregoing, but should be given the broadest interpretation consistent with the specification as a whole.