WO2014095631A1

WO2014095631A1 - Hydraulic drive mounting

Info

Publication number: WO2014095631A1
Application number: PCT/EP2013/076542
Authority: WO
Inventors: Werner BARNSTEINER; Richard Heindl
Original assignee: Agco International Gmbh
Priority date: 2012-12-21
Filing date: 2013-12-13
Publication date: 2014-06-26
Also published as: GB201223541D0

Abstract

A hydraulic drive system mounting for a vehicle. The mounting comprises a rigid body (100) having a first portion (102) configured to receive an adjustable main pump in fixed attachment thereto, and a plurality of mounting lugs (112, 114) shaped to cooperate with mounting means within a transmission housing of the vehicle. The rigid body (100) has a second portion (106), which may be an external mounting boss, configured to receive an additional fluid pump provided in parallel with the main pump in fixed attachment to the rigid body. Suitably, the rigid body has a third portion (104) configured to receive a hydraulic driving motor in fixed attachment thereto.

Description

Hydraulic Drive Mounting

The present invention is related to hydraulic drive arrangements for vehicles, especially but not exclusively agricultural vehicles such as harvesting machinery and tractors.

Hydraulic, or more exactly hydrostatic, drives are widely used to propel the axles/wheels of various vehicles. There are vehicles which are provided with fully hydrostatic drive systems, including agricultural vehicles such as harvesting machines and construction equipment such as loaders or crawlers, wherein the power is completely transmitted over the hydrostatic arrangement. Furthermore, there are vehicles, especially tractors, wherein hydrostatic- mechanical power split drive systems are used. Generally speaking, these split drive arrangements are characterised by having the power of the engine split into a mechanical branch and a hydrostatic branch and summed up in the transmission. The hydrostatic branch thereby serves to make the gear ratio continuously variable.

The hydrostatic branch of a hydrostatic-mechanical power split drive system and a pure hydrostatic drive system show no relevant differences in terms of their general function, so both types are covered by the name "hydrostatic drive" in the further description.

Furthermore, for the purposes of the present application, the terms "hydraulic" and

"hydrostatic" are considered equivalent and interchangeable.

Figure 1 of the attached drawings schematically shows the main components of a hydrostatic drive 1 comprising primary mover, such as a combustion engine 2, which is drivingly connected to a first hydrostat working as hydraulic pump 3. Pump 3 supplies pressurised fluid to a second hydrostat working as a hydraulic driving motor 4 via a hydraulic circuit HC. Hydraulic driving motor 4 is connected to the driven axle(s) of the vehicle. As a basic configuration, one of the hydrostats 3, 4 may be adjustable to adapt fluid (oil) flow so that gear ratios and driving in both directions can be provided.

In the shown embodiment, both hydrostats 3, 4 are of adjustable type. In general, the driving motor 4 could also be a fixed displacement type. Both variations enable that the oil flow can be regulated in both directions, shown in Figure 1 with arrow F for forward driving of the vehicle and arrow R, for reverse driving of the vehicle. One type of adjustable hydrostat is an axial piston hydrostat of oblique-axle design, of which the delivery/intake volume is changed by pivoting the axis of rotation of the pistons relative an axle input shaft (see EP 0 491 903 A1 ). By pivoting the axial piston the oil flow can be regulated. Furthermore, by pivoting one or each of the pistons for hydrostats 3, 4, the drive system can reverse the direction of the driving motor 4 and thereby reverse the driving direction of the vehicle. In such an arrangement, the pivot angles of pump and driving motor can vary depending on the characteristic map of the drive, so the respective pivoting angles are not equal at all points of operation. This is especially the case for standstill, where the only requirement for the drive system is that pump 3 is pivoted to produce zero flow rate (which may be zero degree pivot angle) while the driving motor at this point can still have a different pivot angle, as no oil is supplied to it. As the variability of driving motor 4 is not relevant for the invention, this will not be considered furthermore. Other types of hydrostat (radial piston, gear-types, georotor) are well known in the art and may serve the same purpose.

Dimensioning a hydrostatic drive requires the consideration of several issues. In vehicles of the types discussed above, the primary mover (engine 2) is running in a quite small range of engine speeds, say 1000 to 2200 rpm, and the pump 3 can be dimensioned in a small operating range to deliver the maximum performance over the full range of speeds.

Compared to the pump, however, the driving motor 4 is operated in various operating conditions. A first condition can be described as the pull-mode, wherein the vehicle runs with low vehicle speed and high drag forces, for example when a tractor does soil work with a plough. In this mode, the driving motor 4 runs at low speed >0 rpm but has to supply maximum torque. A second operating condition, say transport mode, requires high vehicle speed but lower drag forces. In this mode, the driving motor 4 runs at high speed, such as 5000 rpm, but supplies less torque. These two varying operational conditions result in the requirement that the driving motor 4 must be oversized to accommodate both operating points while the pump 3 is dimensioned without available surplus.

The applicants have recognised that, if the overall performance of the system must be increased, the pump 3 is the limiting factor while the motor 4, depending on the operating point, would still be able to provide surplus depending of the operating conditions. For example, if the same driving motor 4 is used to drive a vehicle with reduced requirements in terms of maximum vehicle speed or drag forces, the driving motor 4 is still capable to bear the load, so that the pump 3 can be enlarged without reducing reliability. However, there are various reasons why enlarging the existing pump may be disadvantageous. Especially in the case of hydrostatic-mechanical power split drive systems, pump, motor and hydraulic circuit are conventionally installed in a unit within a transmission housing which replaces the conventional stepped gear transmission. If a larger pump has to be installed, the design of the housing and surrounding parts cannot readily be adapted and so must be redesigned completely. This issue becomes particularly acute for vehicles with high performance which are more likely to require the performance increase but which may be sold in relatively small numbers, making the above described design changes economically unsustainable.

In accordance with the present invention there is provided a hydraulic drive system mounting for a vehicle, said mounting comprising a rigid body having a first portion configured to receive an adjustable main pump in fixed attachment thereto, and a plurality of mounting lugs shaped to cooperate with mounting means within a transmission housing, characterised in that the rigid body has a second portion configured to receive an additional fluid pump provided in parallel with the main pump in fixed attachment to the rigid body. The rigid body may be a unitary item or may comprise two or more body parts or sections rigidly joined together. In addition to facilitating the benefits arising from the provision of an additional pump, the mounting of the invention provides a number of benefits:

1. All components related to the hydraulic / mechanical branch of a can be preassembled and moved into the outer housing, which has an opening through which the subassembly can pass.

2. The mounting may be attached to the outer housing by silencer means to reduce vibration and noise, as described in US5345839. So attaching the additional pump to the mounting also damps the additional pump. If it were attached to the outer housing, noise and vibration due to the additional pump would be transferred through the outer housing to the chassis.

3. The hydraulic circuit of the hydraulic branch is operated with a very high pressure level (max 500bar) compared to the work hydraulic for tractor linkages etc, which are operated with 300 bar max. So if the additional pump would be connected to the outer housing while the main pump is attached to inner housing, the connecting pipes would have to face higher vibration.

4. The outer housing builds a protective cage (for the components and the operator) around this high pressure circuit and components. Adding the additional pump to the inner housing also protects this additional pump. Further features of the present invention will become apparent from reading of the following description of exemplary embodiments and are defined in the claims attached hereto.

Figure 1 is a schematic representation of a known hydraulic drive system arrangement, as described above;

Figure 2 shows a vehicle including a hydraulic drive system;

Figure 3 is a schematic representation of a configuration of hydraulic drive system;

Figure 4 is a perspective view of a hydraulic drive system mounting according to the present invention;

Figure 5 is a further perspective view of the mounting of Figure 4 with components of a hydraulic drive system attached; and

Figure 6 is a schematic representation of the mounting of Figures 4 and 5 mounted within a transmission housing. In the following embodiments, the reference numerals from Figure 1 are re-used where appropriate. Ideal processes without losses are assumed in the description of operation of the drive system.

Figure 2 shows an agricultural vehicle in the form of a tractor 12 having a prime mover (combustion engine 2) coupled to a hydraulic drive arrangement 1 within a transmission housing 15 via driveshaft 13. The output of the drive arrangement 1 is drivingly coupled to the tractor rear axle assembly 14. Arrangements for driving the front wheels, where provided, are conventional and are omitted from the Figure. Figure 3 shows a configuration of hydraulic (hydrostatic) drive system which may be used with a drive system mounting embodying the invention. A main pump 3 is connected via a hydraulic circuit HC to driving motor 4. An additional pump 5 is installed in parallel with the main pump 3 via an additional hydraulic circuit AHC. The additional pump 5 is of fixed displacement type and is driven by the engine 2. As the engine rotates in one direction only, the additional pump 5 can only supply oil flow in one direction, shown in Figure 3 by arrow A.

Looking now at the different operations relating to the driving conditions of the vehicle, and considering that both pumps 3 and 5 are of the same size in terms of flow rate:

If the main pump 3, which is of adjustable type, is pivoted to supply in direction F, the oil flow of both pumps 3 and 5 is summed. For example, if the flow rate of the main pump 3 is 80 litres per minute and the flow rate of the additional pump 5 is 80 litres per minute, the driving motor 4 would be supplied by an oil flow of 160 litres per minute. If the main pump 3 is pivoted to zero flow rate, the additional pump 5 would continue, resulting in the driving motor 4 continuing to rotate as the overall oil flow is 80 litres per minute.

If the main pump 3 supplies in the opposite direction R, the flow rates from the two pumps would neutralize each other, and the driving motor 4 would not receive any oil flow.

As a consequence the drive system is not able to go in reverse direction. To enable this, a clutch 6 is provided to disconnect the additional pump 5 from the engine input. Without further means, this would result in the additional pump 5 then being driven by the oil flow from the main pump 3, with the result that the driving motor 4 is not supplied with the maximum available oil flow, which is inefficient. Therefore, an additional brake 7 is provided. If the clutch 6 is disengaged, the brake 7 is simultaneously activated so that the additional pump 5 is mechanically blocked and the driving motor 4 is supplied with maximum available oil flow.

The mounting arrangements for the main and auxiliary pump are now described with reference to Figures 4 to 6. Figure 4 shows a mounting comprising a rigid body 100 having a number of specifically shaped portions to which the components of the CVT are to be mounted. A first portion 102, configured to receive an adjustable main pump 3 in fixed attachment thereto, is provided at the rear left hand side of the body (in the orientation of the Figure). Adjacent that, again at the rear of the body, is a mounting portion 104 configured to receive a hydraulic driving motor 4 in fixed attachment thereto. Extending from the outer surface of the mounting is a further portion 106 configured as a mounting boss to receive an additional fluid pump 5 provided in parallel with the main pump 3 in fixed attachment to the rigid body.

Figure 5 shows the mounting of Figure 4 with a number of components, including main 3 and auxiliary 5 pumps, attached. The rigid body 100 is provided with a number of mounting lugs 1 12, 1 14 shaped to cooperate with mounting means within a transmission housing 15, as will be described further below. The rigid body has one or more apertures through which connectors of a hydraulic circuit fluidically connecting the main pump 3 and additional fluid pump 5, when fitted, may pass, with one or more of those apertures being closed by a blanking plate when the additional fluid pump 5 is not fitted. In use on a tractor, the CVT assembly of Figure 5 (indicated generally by reference numeral 120) is mounted within a housing 15 as illustrated in Figure 6, which housing 15 forms part of the tractor chassis. In order to maintain vibration and sound emission levels within tolerable limits, the CVT assembly 120 is supported with respect to the housing 15 by mounting means in the form of structure-borne noise damping components supporting mounting bars 122 which extend laterally across the casing (between opposed interior surfaces of the housing) and cooperate with the mounting lugs 1 12, 1 14 of the mounting structure. The mounting bars 122 are rigidly attached to the mounting lugs 1 12, 1 14, suitably by tightening bolts 124 which close up the mounting lug aperture. The bars 122 are attached via one or more noise damping components to the transmission housing.

For assembly, the housing 15 has a closable aperture 126 through which the CVT assembly 120 is inserted. Further apertures in the side walls allow the mounting bars 122 to be fitted, together with the damping components, from outside the casing. Such a mounting arrangement is described in greater detail in United States Patent 5,345,839.

From reading of the present disclosure, other modifications will be apparent to those skilled in the art. Such modifications may involve other features which are already known in the field of vehicle transmission and drive systems and component parts therefore and which may be used instead of or in addition to features described herein.

Claims

CLAIMS 1. A hydraulic drive system mounting for a vehicle, said mounting comprising a rigid body (100) having a first portion (102) configured to receive an adjustable main pump in fixed attachment thereto, and a plurality of mounting lugs (1 12, 1 14) shaped to cooperate with mounting means within a transmission housing, characterised in that the rigid body (100) has a second portion (106) configured to receive an additional fluid pump provided in parallel with the main pump in fixed attachment to the rigid body (100).

2. A hydraulic drive system mounting as claimed in claim 1 , wherein the rigid body (100) has a third portion (104) configured to receive a hydraulic driving motor in fixed attachment thereto.

3. A hydraulic drive system mounting as claimed in claim 1 or claim 2, wherein the rigid body (100) has one or more apertures through which a hydraulic circuit fluidically connecting said main pump and additional fluid pump, when fitted, may pass.

4. A hydraulic drive system mounting as claimed in claim 3, wherein at least one of said one or more apertures is closed by a blanking plate when an additional fluid pump is not fitted.

5. A hydraulic drive system mounting as claimed in any of claims 1 to 4, wherein the second portion (106) is a mounting boss on an external surface of the mounting (100).

6. A hydraulic drive system mounting as claimed in any preceding claim, further comprising a transmission housing (15) disposed around the rigid body (100) and mounting means (122) extending from an interior surface of the housing (15) to cooperate with the mounting lugs (1 12, 1 14) of the rigid body to support the rigid body (100) within the housing (15).

7. A hydraulic drive system mounting as claimed in claim 6, wherein the mounting lugs (1 12, 1 14) each comprise an extended portion of the rigid body (100) with a respective aperture therethrough, and the mounting means (122) comprise at least two bars each extending between opposed interior surfaces of the housing (15) and each passing through a respective mounting lug aperture.

8. A hydraulic drive system mounting as claimed in claim 6 or claim 7, wherein the mounting means (122) are rigidly attached to the mounting lugs (1 12, 1 14), and are attached via one or more noise damping components to the transmission housing (15).

9. A hydraulic drive system mounting as claimed in any preceding claim, wherein the rigid body comprises at least first and second sections rigidly joined together.

10. A hydraulic drive system for a vehicle having a primary mover (2), such as an internal combustion engine, and at least one axle driven by said drive system, said drive system comprising a mounting as claimed in claim 1 , 2 or 3, to which are attached:

an adjustable main pump (3) drivingly connectable to a primary mover;

an additional fluid pump (5) is provided in parallel with the main pump (3);

a hydraulic driving motor (4) drivingly connectable to at least one driven axle; and - a hydraulic circuit (HC) fluidically connecting said main pump (3), additional fluid pump (5) and driving motor (4), whereby through fluid flow control the driving motor can be rotated in two directions and zero rotation.