IE20040688U1 - A fluid control valve - Google Patents

Abstract

ABSTRACT The invention provides a fluid control valve for controlling the flow of hydraulic fluid from a hydraulic pump to and from a plurality of hydraulic motors. The valve conveniently includes selector valve for selectively energizing a flow divider/combiner spool that controls the flow of hydraulic fluid to and from the motors. The flow divider/combiner spool has on its periphery lubrication grooves which also act as metering grooves. An advantage of the fluid control valve of the invention is that it regulates and equalises the flow and pressure of the hydraulic fluid delivered between a hydraulic pump and a plurality of hydraulic motors, thereby enabling each hydraulic motor to rotate in a synchronized fashion when traction control is required and without the operator having to deactivate the valve, the valve will disengage once traction to all wheels has been regained.

Description

A FLUID CONTROL VALVE The present invention relates to a fluid control valve for controlling the flow of hydraulic fluid from a hydraulic pump to and from a plurality of hydraulic motors. More particularly, the invention relates to a hydraulic fluid control valve for dividing, regulating and equalizing the flow and pressure of the hydraulic fluid delivered to and from two or more hydraulic motors when configured as a parallel drive circuit.

Fluid control valves are well known in the art and have found application in both fuel control systems and compression release engine brakes of vehicles. In particular, such valves are commonly used to control the flow of hydraulic fluid in the hydraulic drive systems of vehicles. Taking as an example, a hydraulic parallel drive system for a vehicle such as a three—wheel drive forklift, an inherent feature of this type of drive system is an open differential whereby an unregulated but balanced amount of hydraulic fluid is delivered to each wheel of the Vehicle. This arises because hydraulic fluid such as oil will always flow through the path of least resistance. Having an open differential is an advantage when a vehicle is travelling on feasible ground such as a paved surface. In such conditions, the open differential allows driving around bends and turning when the tyres are in Contact with the feasible driving surface. However, this advantage is lost when the vehicle encounters terrain where traction is compromised.

With an open differential, if a wheel looses traction, all drive power is delivered to that wheel resulting in the wheel spinning without gripping the surface to enable it to move the vehicle in the direction of travel. In such conditions, full flow of hydraulic fluid is supplied to the wheel that is spinning, resulting in a drop in system pressure. With no remaining flow available for the other drive wheels that do have traction, the vehicle eannot continue its motion in a forward or reverse direction. In order to regain vehicle motion, power must be taken from the wheel that is spinning out and redistributed to the wheels that are not. In hydraulic parallel drive systems this is achieved by regulating or metering the fluid flow to the wheel that is spinning out while also maintaining sufficient system flow and pressure to drive the remaining wheels that do have traction.

United States Patent Specification No. US 5,647,211 discloses a valve for controlling the flow of hydraulic fluid from a hydraulic pump to and back from a pair of hydraulic motors.

The valve disclosed in US 5,647,211 is a complex flow divider which comprises two flow dividers, namely one flow divider for each wheel motor. Also several spools and a plurality of pressure selector valvesl solenoid control valves are used. The valve as disclosed in US 5,647,211 also does not readily or easily lend itself to driving a three wheeled vehicle having three wheel motors.

It is therefore an object of the present invention to provide an improved fluid control valve for use in hydraulic parallel drive systems to divide, regulate and equalize the flow and pressure of the hydraulic fluid to and from a plurality of hydraulic motors.

Thus, the present invention seeks to alleviate the disadvantages of known fluid control valves by providing an improved control valve, with a simple and robust design, and having less components than existing valves known in the art.

Accordingly, the present invention provides a fluid control valve for use in controlling the flow of hydraulic fluid from a hydraulic transmission pump to and from a plurality of hydraulic motors, the valve comprising a plurality of fluid lines for providing fluid to the respective hydraulic motors, a spool chamber and a flow divider/combiner spool which is longitudinally slideably moveable within the spool chamber between a first position and a second position; wherein in the first position, the flow divider/combiner spool provides unrestricted flow from the transmission pump to and from the plurality of motors, and in the second position the flow divider/combiner spool provides metered flow from the transmission pump to and from the plurality of motors.

Conveniently, the fluid control valve includes a single spool chamber and a single flow divider/combiner spool.

Thus, the fluid control valve of the invention has the significant advantage that it allows for a single flow divider/combiner spool which is capable of controlling the flow of hydraulic IE 040688 fluid from the pump to and from a plurality of wheel motors. This represents a significant advance over the prior art.

Conveniently, the flow divider/combiner spool is held in the first position by a compression spring.

The fluid control valve also includes operator—controllable selector means for controlling the position of the spool in the spool chamber. Conveniently, this operator-controllable selector means comprises a solenoid operated, 3-way selector valve, which when energized causes the flow divider/combiner spool to move within the spool chamber under pressure from an external charge pump to the second position in which the spring is compressed.

Alternatively, the operator—controllable selector means may be a switch operable by pneumatic, mechanical, electrical or manual means.

Ideally, metered flow is provided by means of a plurality of fluid metering means located in a non—continuous manner along the length of the flow divider/combiner spool.

Ideally, the plurality of fluid metering means comprise a series of grooves formed on the outer surface of the flow divider/combiner spool.

Preferably, when the flow divider/combiner spool is in the second position the fluid metering grooves are in fluid communication with the fluid lines connecting the transmission pump and the plurality of motors, thereby allowing metered flow from the transmission pump to and from the plurality of motors.

Advantageously, the grooves on the outer surface of the flow divider/combiner spool act as lubrication grooves to aid movement of the spool to and from the first and the second position within the spool chamber.

IE 040688 Conveniently, the lubrication grooves on the outer surface of the spool also function as a metering flow path when the spool is in the second position.

Preferably, the flow divider/combiner spool also includes a plurality of full-flow means provided along the length of the spool. The full—flow means/ full—flow sections are ideally provided in an arrangement with a full—flow section adjacent the metering means (metering grooves). Thus, full-flow sections and metered flow grooves are provided in an alternate arrangement along the length of the spool.

Conveniently, when the spool is in the first position, the full—flow sections are in fluid communication with the fluid lines connecting the transmission pump and the plurality of motors, thereby allowing full flow from the transmission pump to and from the plurality of I1’l0tOI'S .

The invention will hereinafter be described more particularly with reference to the accompanying drawings in which are shown, one example of a fluid control valve in accordance with the present invention.

In the drawings: Figure 1 is a schematic diagram of a parallel circuit hydraulic drive system for a three- wheel drive vehicle which includes the fluid control valve of the present invention; Figure 2 is a front sectioned View of the fluid control valve when the selector valve is de- energized, showing the flow divider/combiner spool in a first position permitting full unrestricted flow to and from a plurality of motors and a transmission pump; Figure 3 is a front sectioned view of the fluid control valve when the selector valve is energized, showing the flow divider/combiner spool in a second position, thereby allowing metered flow to and from a plurality of motors and a transmission pump; IE 040688 Figure 4 is an exploded view showing the components of the fluid control valve of the present invention including a detailed side view of one of the grooved segments provided on the flow divider/combiner spool; Figure 5 is a top section view of the manifold block of the fluid control valve along the lines A—A of Figure 2; Figure 6 is a side section view of the manifold block of the fluid control valve along the lines B—B of Figure 2; Figure 7 is a top section view of the manifold block of the fluid control valve along the lines C-C of Figure 3; and Figure 8 is a side section view of the manifold block of the fluid control valve along the lines D—D of Figure 3.

Referring to the drawings and initially to Figure 1, there is shown and indicated generally by reference letter A, a parallel circuit hydraulic drive system for a vehicle such as a three wheel drive forklift which incorporates the fluid control valve of the present invention.

The hydraulic drive system A includes a prime mover 6, and a high-pressure transmission pump 5 coupled to the prime mover 6 to provide the hydraulic drive for the hydraulic drive system A. Also included in the hydraulic drive system A are a charge pump 4, fluid supply and return lines 8 and 9, motors 7, a source of fluid 19 and a reservoir (or sump) 14.

The high-pressure transmission pump 5 is operable in forward or reverse bias thereby providing high-pressure fluid supply to line 8 or 9 while the other line 9 or 8 acts as a low pressure fluid return line.

The fluid control valve 1 comprises a manifold block la having fluid lines 8, 8a, 8b, 8c, 11, 12, 13, a spool chamber (not shown), a flow divider/combiner spool 2 and a control compression spring 10. Additionally and conveniently, the fluid control valve comprises a IE 040688 solenoid operated, 3-way, selector valve 3. Fluid path 11 connects the flow divider/combiner spool 2 to the reservoir 14, as well as linking selector valve 3 to the reservoir. Fluid path 12 provides a pressure connection between the selector valve 3 and the charge pump 4 whereas fluid path 13 connects the flow divider/combiner spool 2 to the selector valve 3.

Referring now to Figures 1 and 2, the flow dividerl combiner spool 2 comprises a high pressure shuttle type spool. The spool position in the spool chamber is determined by whether or not the selector valve is energized. When the flow divider/combiner spool 2 is in the first position, as shown in Figure 2, allowing unrestricted flow to and from a transmission pump and the plurality of motors, the flow divider/combiner spool 2 is held in the first position by the force of the compression spring 10. When it is desired to move the flow divider/combiner spool 2 to the second position in which metered flow to and from the motors is possible, the selector valve 3 is energized, resulting in a charge pressure from a charge pump 4 overcoming the compression force of the spring 10 and acting to move the spool 2 in the spool chamber 21 to a second position (as shown in Figure 3), in which the spring 10 is shown fully compressed.

The manifold block 1a of the fluid control valve is mounted on a vehicle chassis or axle through mounting holes 20. The flow divider/combiner spool 2 extends along the length of the manifold block la and is capped at either end with a sealing member 17 and access plug 16.

Fluid line 8 splits into fluid lines 8a, 8b and 8c which intersect the flow divider/combiner spool 2. The fluid control valve 1 provides divided flow from transmission pump 5 to motors 7 via fluid lines 8a, 8b and 8c or combined flow from motors 7 to transmission pump 5 via fluid lines 8a, 8b or 8c.

Divided flow to the motors 7 is provided when the transmission pump 5 is operating in forward bias and fluid line 8 is a high—pressure fluid supply line, with fluid line 9 acting as a low—pressure fluid return line. Combined flow from the motors 7 is provided when the transmission pump 5 is operating in reverse bias and fluid line 8 is a low—pressure fluid IE 040688 return line, with fluid line 9 acting as a high-pressure fluid supply line. Fluid line 9 splits into fluid lines 921, 9b and 9c which feed the motors 7. Fluid flow through the flow divider/combiner spool to or from the motors can either be unrestricted or metered depending on whether or not the selector valve 3 is energized.

As shown in Figure 2, when the selector valve 3 is de—energized, a connection between fluid path 11 and fluid path 13 is made while blocking the connection to fluid path 12.

This enables the compression spring 10 to control the position of the high—pressure flow divider/combiner spool 2 since fluid path 13 has a direct connection to the reservoir 14. In this mode, full unrestricted flow to or from the motors 7 is permitted.

Referring now to Figures 1 and 3, when the selector valve 3 is energized, a connection between fluid path 12 and fluid path 13 is made while blocking the connection to fluid path 11. As a result, a charge pressure from the charge pump 4 overcomes the compression spring 10 and the position of the high—pressure flow divider/combiner spool 2 shifts within the spool chamber 21 to a second position which provides metered flow to or from the motors 7.

Referring now to Figure 4, the high pressure flow divider/combiner spool 2 is shown in more detail. The spool 2 includes a plurality of full flow sections 221 and a plurality of discrete (non—continuous) metered flow sections (grooves) 2b. The full flow sections 2a are aligned with the fluid lines 8a, 8b and 8c when the selector valve 3 is de—energized, whereas the metered flow sections 2b are aligned with the fluid lines 8a, 8b and 8c when the selector valve 3 is energized. The flow divider/combiner spool 2 has cylindrical metering and lubrication grooves 15 on the outer surface of flow sections 2b which act as a metering flow path when the selector valve 3 is energized. Construction hole plugs 18 on the periphery of the manifold block la block access to fluid lines 11, 12 and 13.

Considering the operation of the flow divider/combiner spool 2 in more detail. Referring to Figures 5 and 6, when the selector valve is de—energized, a fully extended compression spring 10 holds the spool 2 in a first position such that full flow sections 2a are aligned with fluid lines 8a, 8b and 8c permitting full unrestricted flow to or from the motors 7. In particular, Figure 6 shows an unrestricted flow path from fluid line 8a, 8b or 8c around the shuttle spool 2 to a motor 7.

Referring now to Figures 7 and 8, when the selector valve is energized, a charge pressure from charge pump 4 results in shifting of the flow divider/combiner spool 2 within the spool chamber 21, overcoming the force of the compression spring 10 such that the flow divider combiner spool 2 assumes a second position in which metered flow sections 2b are aligned with fluid lines 8a, 8b, and 8c. The cylindrical metering and lubrication grooves on the outer surface of metered flow sections 2b are aligned with fluid lines 8a, 8b and c permitting metered flow to or from the motors.

In particular, Figure 8 shows the metered flow path from fluid line 8a, 8b or 8c through the spool chamber 21 to a motor 7 through the metering and lubrication grooves 15 on the outer surface of flow sections 2b. A metering channel flow path 22, formed by and between metering and lubrication grooves 15 and the spool chamber 21 provide a metered flow path from fluid line 8a, 8b or 8c to a motor 7.

The fluid control valve 1 will now be described in use. In normal driving mode, that is, on a good traction surface such as a paved surface, the compression spring 10 forces the high pressure flow divider/combiner spool 2 to one side thereby enabling full free flow from the transmission pump 5 to or from the wheel motors 7.

When driving on uneven ground, in conditions where wheel slip is likely, the selector valve 3 is activated by the driver causing a charge pressure from the charge pump 4 to overcome the compression spring force and move the divider/combiner spool 2 in the opposite direction. This results in metered flow to or from the wheel motors 7. Metered flow is only provided while the selector valve 3 is activated. By restricting the flow of fluid to or from the wheel motors 7, the same flow and pressure is delivered to each wheel allowing vehicle motion to be resumed.

IE 040688 It will of course be understood that the invention is not limited to the specific details herein described which are given by way of example only and that various modifications and alternations are possible without departing from the scope of the invention.

MACLACHLAN & DONALDSON Applicants’ Agents Merrion Square DUBLIN 2 IE 040688 The following replacement page 9 was filed on 11/10/2005 P3559688 It will of course be understood that the invention is not limited to the specific details herein described which are given by way of example only and that various modifications and alternations are possible without departing from the scope of the invention as defined in the appended claims.

Claims (5)

CLAIMS:

1. A fluid control valve for use in controlling flow of hydraulic fluid between a hydraulic transmission pump and a plurality of hydraulic motors, the valve comprising a plurality of fluid lines for providing fluid to the respective hydraulic motors, a spool chamber and a flow divider/combiner spool which is longitudinally slideably moveable within the spool chamber between a first position and a second position; wherein in the first position, the flow divider/combiner spool provides unrestricted flow between the transmission pump and the plurality of motors, and in the second position, the flow divider/combiner spool provides controlled flow between the transmission pump and the plurality of motors.

2. A fluid control Valve as claimed in Claim 1, wherein the fluid control valve includes a single spool chamber and a single flow divider/combiner spool, and further comprises operator—controllable selector means for initiating the controlling position of the flow divider/combiner spool in the spool chamber; optionally wherein the flow divider/combiner spool is held in the first position by a compression spring and wherein the operator—controllable selector means comprises a solenoid operated, 3-way selector valve; whereby the selector means need only be activated by the operator to overcome the force of the compression spring so as to move the spool from the first position to the second position.

3. A fluid control valve as claimed in Claim 1 or Claim 2, wherein a plurality of fluid flow control members located in a non-continuous manner along the length of the flow divider/combiner spool provides controlled flow; optionally wherein the plurality of fluid flow control members comprise a series of grooves formed on the outer surface of the flow divider/combiner spool, whereby with the flow divider/combiner spool in the second position, the fluid control members are in fluid communication with the fluid lines connecting the transmission pump and the plurality of IE M0688 ll motors, thereby allowing controlled flow from the transmission pump to and from the plurality of motors; optionally wherein the grooves on the outer surface of the flow divider/combiner spool act as lubrication grooves to aid movement of the spool to and from the first and the second position within the spool chamber.

4. A fluid control valve as claimed in any preceding claim, wherein the flow divider/combiner spool includes a plurality of full-flow means provided along the length of the flow divider/combiner spool; optioanlly wherein the filll-flOW means are sections provided in an arrangement with a full- flow section adjacent the flow control members; optionally wherein the full-flow sections and the flow control members are provided in an alternate arrangement along the length of the flow divider/combiner spool; and optionally wherein with the flow divider/combiner spool in the first position, the full-flow sections are in fluid communication with the fluid lines connecting the transmission pump and the plurality of motors, thereby allowing full flow from the transmission pump to and from the plurality of motors.

5. A fluid control valve, substantially in accordance with any of the embodiments herein described with reference to and/or shown in the accompanying drawings. MACLACHLAN & DONALDSON, Applicants’ Agents, 47 Merrion Square,