GB2367095A

GB2367095A - Valve arrangement in separating plate of multiple hydraulic pump and motor ass emblies

Info

Publication number: GB2367095A
Application number: GB0022359A
Authority: GB
Inventors: Ian David Patterson; Julian Edward Nelson
Original assignee: Sauer Danfoss GB Ltd
Current assignee: Sauer Danfoss Swindon Ltd
Priority date: 2000-09-13
Filing date: 2000-09-13
Publication date: 2002-03-27
Also published as: GB0022359D0; GB2367095A8

Abstract

A valve arrangement is provided within a separating plate 20 located between neighbouring pump units 15,3,5 and/or motor units 13 within a multiple unit assembly, each unit having a pair of intermeshing gears. The valve arrangement is in fluid communication with an inlet gallery or an outlet gallery of the intermeshing gears of at least one of the neighbouring units and may comprise a pressure relief poppet valve 60,30 and a flow control spool valve 50 to regulate fluid.

Description

2367095 TITLE Sandwich plate for multiple hydraulic pump and motor

assemblies

DESCRIPTION

Field of the Invention

The invention relates to hydraulic assemblies containing multiple pumps or motors and, in particular, to the provision of hydraulic valve means in a sandwich plate disposed between a pair of neighbouring pumps or motors within such an assembly. Throughout this specification the term "sandwich plate" has been used to define the inter pump/motor sealing plate between neighbouring pump/motor sections. Although the invention is equally applicable to both pumps and motors operating under hydraulic pressure, in the following description, reference is almost exclusively made to pumps.

Background Art

A conventional method of controlling the output characteristics of a hydraulic pump is to communicate fluid derived from a high pressure port of the pump to valve means prior to delivery to a hydraulic load. Two of the most commonly used valve means are pressure relief valves which attempt to sustain the pressure of the fluid derived from the high pressure port of the pump within predetermined thresholds and flow control valves which attempt to ensure that the flow rate of the fluid derived from the high pressure port matches that required by the hydraulic load.

Generally, such valve means are mounted on an external housing to the pump assembly. Typically, the valves are provided on a rear cover of the pump or, in certain instances, in an end plate of the pump. However, substantial lengths of fluid passageways are required in these applications since the positions at which the valves are mounted on the pumps are generally remote from the high pressure ports of the pumps. As the skilled person will appreciate, this problem is exaggerated further in multiple pump assemblies wherein a series of neighbouring pumps, in close proximity, are driven by a common drive shaft. In such an assembly, valve means associated with any of the intermediate pumps must be mounted on the external housing of the pur-nps.

Accordingly, it is an objective of the present invention to reduce the number and length of fluid passageways interconnecting the high pressure outlet ports of pumps within a multiple pump assembly to respective hydraulic valve means for governing the quality of the fluid supplied to an external hydraulic load.

Summary of the Invention

The present invention provides a hydraulic sandwich plate for separating neighbouring units within a multiple unit assembly. The units may be hydraulic pumps, hydraulic motors or a combination thereof and each unit has a pair of intermeshing gears. The sandwich plate contains valve means in fluid communication with an inlet gallery or an outlet gallery of the intermeshing gears of at least one of the neighbouring units to regulate hydraulic fluid at said gallery.

Preferably, the valve means includes a pressure relief valve to maintain the pressure of the hydraulic fluid at said gallery within predetermined thresholds.

Furthermore, the valve means may include a flow control valve to maintain the flow of the hydraulic fluid at said gallery within predetermined thresholds.

Preferably, when the sandwich plate is provided between two pumps, the valve means communicates with a high pressure outlet gallery from the intermeshing gears of one or both pumps.

On the contrary, when the sandwich plate is provided between two motors, it is preferable for the valve means to communicate with a high pressure inlet gallery to the intermeshing gears of one or both motors.

Brief Description of the Drawings

The invention is illustrated in the accompanying drawings, of which:

Figure 1 is a plan view of a tandem gear pump assembly incorporating a sandwich plate in accordance with a first embodiment of the invention; Figure 2a is a cross-section of the sandwich plate of Fig. 1 taken along the axis of the pump assembly:

Figure 2b is a plan view of the left face of the sandwich plate illustrated in Fig. 2a; Figure 2c is a plan view of the right face of the sandwich plate illustrated in Fig. 2a; Figure 3a is a cross-section of the sandwich plate of Fig. 2a taken along line A-A; Figure 3b is a plan view taken along line C-C of Fig. 3a; Figure 3c is a section taken along line E-E of Fig. 3b; Figure 4 is an exploded view of the.pressure relief valve of Fig. 3a; Figure 5 is a plan view of a multiple unit hydraulic assembly incorporating a sandwich plate in accordance with a second embodiment of the invention; Figure 6 is a schematic of the assembly of Fig. 5; and Figure 7 is a cross-section of the sandwich plate of Fig. 5.

Specific Description of the Preferred Embodiments

A tandem gear pump assembly 1 is shown in Fig. 1 which includes a front pump 3 and a rear pump 5. Both of these pumps 3,5 are conventional gear pumps that are driven by a common drive shaft 7 which is externally powered to drive internal intermeshing gears (not shown) of the pumps 3,5 so as to transfer fluid from a low pressure inlet port (not shown) on each pump 3,5 to 'a high pressure outlet port (not shown) on each pump 3, 5. The intermeshing gears of each pump 3,5 are contained within a housing 9 which is sealed at one side by an end plate 11. A sandwich plate 20 is provided between the pumps to separate and seal the front pump 3 from the rear pump 5. A pressure relief valve 30 is mounted within the sandwich plate 20 to regulate the fluid derived from one or both of the pumps 3,5.

Fig. 2a shows the sandwich plate 20 of Fig. 1 in further detail, and Figs. 2b and 2c are plan views of the side faces of the sandwich plate 20 of Fig. 2a taken from the left and right, respectively. In this particular embodiment, an orifice 21 on the left side face of the sandwich plate 20 is in direct communication with the high pressure outlet gallery of the front pump 3. Accordingly, high pressure fluid from the front pump 3 is fed into the orifice 21, through a supply passageway 23 (shown in Fig. 3c) to an annular region 25 machined into the sandwich plate 20. As will become apparent from the following description, the annular region 25 acts as the high pressure input to the pressure relief valve 30 and depending on the pressure of the fluid in the annular region 25, the pressure relief valve 30 will either permit of prevent fluid flow to a relief passageway 27. This passageway 27 is in fluid communication with a relief annulus 28 which in turn is in communication with a shaped gallery 29. The shaped gallery 29 extends through the sandwich plate 20 and connects on either side of the sandwich plate 20 with the low pressure inlet gallery to each of the pumps 3,5. Hence, any fluid supplied to the relief passageway 27 from the pressure relief valve 30 is exhausted to the low pressure inlet gallery of each of the pumps 3,5.

An advantage of exhausting fluid from the relief valve 30 in this manner is that it enables re-circulation through both of the pumps 3,5 and thereby prevents possible heat build up which would result from returning fluid to only that pump from which it was sourced. Furthermore, this arrangement boosts the inlet to both pumps 3,5 during periods when the pressure relief valve 30 is most likely to open, namely when the pumps 3, 5 are at maximum load.

Alternatively, the exhaust fluid from the pressure relief valve 30 can be transferred to either one of the pump inlets or to the inter pump cavity or it could be taken externally through an exhaust port in the sandwich plate 20.

The pressure relief valve 30 of the present embodiment is shown in situ within the sandwich plate 20 in Fig. 3a and in enlarged form in Fig. 4. Although the relief valve 30 is a reverse flow, differential area version, this particular construction is not an essential feature of the invention as any pressure relief valve can be utilised.

The pressure relief valve 30 incorporates a relief valve body 31 which houses a poppet 33 that is biased by a spring 35 towards a seat 37. Fluid is communicated from the annular region 25 of the sandwich plate 20 to the poppet 33 through drilling 39. The poppet 33 is provided with a large diameter section 33a and a small diameter section 33b. When the pressure of the fluid acting on the poppet reaches a level predetermined by the spring 35, the poppet 33 will lift to allow fluid to flow from the annular region 25 of the sandwich plate 20 through the valve body 31 to the relief passageway 27, thereby regulating the pressure of the fluid flowing through the high pressure outlet port of the front pump 13 to the external hydraulic load.

The skilled person will readily appreciate that the configuration of the tandem gear pump assembly 1 can be reversed to give a motor assembly wherein potential energy stored in a high pressure fluid supplied to the assembly is converted so as to rotate the common shaft 7. In this instance, the pressure relief valve 30 in the sandwich plate 20 would be configured to regulate and govern the incoming high pressure fluid which is supplied to the intermeshing gears.

A second embodiment of the invention will now be described with reference to Figs. 5 to 7. Fig. 5 shows a complex hydraulic assembly which has been specifically designed for use on a large earth moving dump truck. The hydraulic assembly comprises a motor 13, a large front pump 15 and a pair of smaller rear pumps 3,5. The rear pair of pumps 3,5 are essentially the same as those incorporated in the tandem gear pump assembly 1 of the previously described embodiment, only in the present configuration the most rearward pump 5 is sealed with an end plate 11 and its output is regulated by a further pressure relief valve 30 mounted within the end plate 11. Alternatively, if the outputs from both of the rear pumps 3,5 are used to feed the same hydraulic load, then it is not necessary to keep them isolated from each other. In such a case, the pressure relief valve 30 in the end plate 11 to the most rearward pump 5 becomes redundant as the pressure relief valve 30 disposed in the sandwich plate 20 separating the two pumps 3,5 could be arranged to regulate the fluid derived from both of the pumps 3,5.

The motor 13 is supplied with fluid from a high pressure source and, in turn, drives the intermeshing gears of all three pumps 15,3,5 via a common drive shaft 7. The pumps feed fluid to axle reduction units to lubricate and cool the gearing of the dump truck. The pressure relief valves 60,30 associated with the pumps 15,3,5 are required to open when the working pressure of the fluid reaches 5 bar. As the speed of the motor 13 (typically related to the prime mover engine speed) increases, the pressure of the fluid controlled by the pressure relief valves 60,30 must not exceed 7 bar. - In practice, it was found that the pressure relief valves 30 associated with the rear pair of pumps 3,5 were capable of achieving the desired pressure relief characteristics. However, since the large front pump 15 is prone to flow rates in the region of 90 litres per minute, it was an extremely difficult task to ensure that the pressure of the fluid derived from this pump 15 did not exceed 7 bar by pressure regulating means 60 alone. At high speeds, the lubrication flow from the large front pump 15 is in excess of that actually required. This excess can reasonably be spilled off at the pump 15 rather than feeding it to the axle and, accordingly, the applicant has designed a second sandwich plate 40 incorporating a flow control valve 50 in combination with a pilot relief valve 60 to separate the front pump 15 from the rear pair of pumps 3,5. The flow control-valve 50 limits the flow rate of the fluid derived from the high pressure output gallery of the intermeshing gears of the pump 15, in the instance to 60 litres per minute, and the pilot valve 60 provides the necessary pressure relief.

Fig. 7 shows a cross-section through the second sandwich plate 40 and, in particular, illustrates the flow control valve 50 and the pilot relief valve 60 housed therein. The flow control valve 50 comprises a spring biased spool 51 that is mounted within the sandwich plate 40. The spool 51 is biased against an end plug 55 by a spring 53 which itself is captive within a second end plug 57. The spool 51 has an associated damping characteristic which is established by a radial drilling 59a and an axial drilling 59b within the spool 51, and a damping orifice 59c provided in a orifice plug 58 at the non-spring end of the spool 51. The damping prevents unwanted instability when the spool 51 is under dynamic conditions.

As in the previous embodiment, fluid from the high pressure outlet gallery of the large front pump 15 is fed directly through an orifice and passage (neither of which are shown) in the sandwich plate 40 to a supply annulus 41. In its rest position, as shown in Fig. 7, the spool 51 is in abutment with the end plug 55 and fluid is permitted to flow from the supply annulus 41 to a preferred service annulus 43. The preferred service annulus 43 is in fluid communication with an outlet port 47 via an orifice 46a and a drilling 46b. A connection is made from the drilling 46b to a spring chamber 52 within the second end plug 57 via a further drilling 46c. This provides both a pressure sensing feed and also a damping function as will be described in more detail later on.

Pressurised fluid is fed from the spring chamber 52 through more drillings 48a and 48b to the pilot operated pressure relief valve 60. The pilot relief valve 60 comprises a poppet 63 which is biased by a spring 65 towards a seat 67, and a closure plug 69 which seals the valve 60 and houses the spring 65. The exhaust from the pilot relief valve 60 is fed through a drilling 49a to a tank annulus 45.

The control of fluid flow from the supply annulus 41 to the outlet port 47 is achieved by continuously monitoring the flow of fluid across orifice 46a. The pressure difference between the upstream and downstream sides of this orifice 46a is sensed in both directions. The pressure of the fluid upstream of the orifice 46a is fed through the spool 51 via drillings 59a and 59b and damping orifice 59c to the non-spring end of the spool 51. The pressure of the fluid downstream of the orifice 46a is fed through drillings 46b and 46c to the spring chamber 52 at the opposite end of the spool 51. The flow control valve 50 is designed such that when the pressure of the fluid reaches a predetermi.ned control level, the difference in pressure caused by the pressure drop across the orifice 46a is sufficient to move the spool 51 against the spring 53. Accordingly, if the flow control valve 50 detects an excessive flow rate through the orifice 46a, the spool 51 moves against the spring 53 thereby directing the excess fluid from the supply annulus 41 to the tank annulus 45.

When the pressure of the fluid in the system exceeds the required level, the poppet 63 of the pilot relief valve 60 lifts against the spring 65 permitting pilot fluid flow from the spring chamber 52 through drillings 48a, 48b and 49a to the tank annulus 45. This pilot flow, which passes through drilling 46c, further lowers the pressure of the fluid in the spring chamber 52 which in turn encourages the spool 51 to move further against the spring 53 and thereby an increased quantity of the fluid from the supply annulus 41 is passed to the tank annulus 45. If the pressure continues to increase, the pilot flow will increase such that the spool 51 will ultimately direct all fluid from the supply annulus 41 to the tank annulus 45. Hence, both the flow rate and the pressure of the fluid supplied to the outlet port 47 are regulated.

In the present embodiment, all of the fluid developed by the intermeshing gears of the front pump 15 is passed to the supply annulus 41, from whence it is modified by the flow control valve 50 and the pilot relief valve 60 to give a regulated output at the outlet port 47 of the sandwich plate 40. As such, the pump 15 does not have an outlet port itself, but regulated fluid is supplied to the axle reduction units of the dump truck from the outlet port 47 of the sandwich plate 40.

As with the previous embodiment, the second sandwich plate can be used in a multiple motor assembly to regulate and govern the high pressure fluid supplied to the motors.

Claims

1. A hydraulic sandwich plate for separating neighbouring units within a multiple unit assembly, the units being either hydraulic pumps, hydraulic motors or a combination thereof, each unit having a pair of intermeshing gears, wherein the sandwich plate contains valve means in fluid communication with an inlet gallery or an outlet gallery of the intermeshing gears of at least one of the neighbouring units to regulate hydraulic fluid at said gallery.

2. A sandwich plate according to claim 1, wherein the valve means includes a pressure relief valve to maintain the pressure of the hydraulic fluid at said gallery within predetermined thresholds.

3. A sandwich plate according to claim 1 or claim 2, wherein the valve means includes a flow control valve to maintain the flow of the hydraulic fluid at said gallery within predetermined thresholds.

4. A sandwich plate according to any of claims 1 to 3, wherein the or each unit with which the valve means is in communication is a pump, the valve means communicating with a high pressure outlet gallery from the intermeshing gears of the pump.

5. A sandwich plate according to any of claims 1 to 3, wherein the or each unit with which the valve means is in communication is a motor, the valve means communicating with a high pressure inlet gallery to the intermeshing gears of the motor.

6. A sandwich plate substantially as hereinbefore described with reference to Figures 1, 2a-c, 3a-c and 4, or Figures 5 to

7.