GB2557591A

GB2557591A - Hydraulic system for a compact wheel loader

Info

Publication number: GB2557591A
Application number: GB1620971.0A
Authority: GB
Inventors: Hudson Henry
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2016-12-09
Filing date: 2016-12-09
Publication date: 2018-06-27
Anticipated expiration: 2036-12-09
Also published as: GB201620971D0; GB2557591B

Abstract

A hydraulic system 32 for a compact wheel loader (10 in Figure 1) is provided. The hydraulic system 32 comprises first and second priority valves 36, 38 configured in series. The first priority valve 36 is connected at its supply input 40 to a source of hydraulic fluid 22, 24 and connected at its primary output 42 to a steering circuit 26. The second priority valve 38 is connected at its supply input 48 to a secondary output 44 of the first priority valve 36. The second priority valve 38 is connected at its primary output 62 to the rear auxiliary circuit 30, and connected at its secondary output 64 to the main implement circuit 28. Hydraulic fluid is supplied, in order of priority, to the steering circuit 26, then to the rear auxiliary circuit 30, and then to the main implement circuit 28. A method for distributing hydraulic fluid using the hydraulic system, and a compact wheel loader having the hydraulic system are also disclosed.

Description

(71) Applicant(s):

Caterpillar Inc.

100 N.E. Adams Street, Peoria, Illinois 61629-9510, United States of America (72) Inventor(s):

Henry Hudson (74) Agent and/or Address for Service:

Novagraaf UK

2nd Floor Renown House, 33-34 Bury Street, LONDON, EC3A 5AR, United Kingdom (51) INT CL:

F15B 11/16 (2006.01) A01B 63/10 (2006.01) E02F 9/22 (2006.01) (56) Documents Cited:

DE 102014226182 A1 US 4966066 A US 20080047423 A1 (58) Field of Search:

INTCLA01B, E02F, F15B Other: WPI; EPODOC (54) Title ofthe Invention: Hydraulic system for a compact wheel loader Abstract Title: A hydraulic system for a compact wheel loader (57) A hydraulic system 32 for a compact wheel loader (10 in Figure 1) is provided. The hydraulic system 32 comprises first and second priority valves 36, 38 configured in series. The first priority valve 36 is connected at its supply input 40 to a source of hydraulic fluid 22, 24 and connected at its primary output 42 to a steering circuit 26. The second priority valve 38 is connected at its supply input 48 to a secondary output 44 of the first priority valve 36. The second priority valve 38 is connected at its primary output 62 to the rear auxiliary circuit 30, and connected at its secondary output 64 to the main implement circuit 28. Hydraulic fluid is supplied, in order of priority, to the steering circuit 26, then to the rear auxiliary circuit 30, and then to the main implement circuit 28. A method for distributing hydraulic fluid using the hydraulic system, and a compact wheel loader having the hydraulic system are also disclosed.

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FIG. 3

-1Title

HYDRAULIC SYSTEM FOR A COMPACT WHEEL LOADER

Technical Field [001] The present disclosure relates to a hydraulic system for a compact wheel loader. More particularly, the present disclosure relates to a hydraulic system for a compact wheel loader to prioritize hydraulic fluid supply to a steering circuit, a main implement and a rear auxiliary implement.

Background [002] Compact wheel loaders are machines in which a work tool, also referred to as a main implement, is fitted to the machine. The main implement is powered by a hydraulic circuit. A variety of implements are available for compact wheel loaders, enabling these loaders to be used in a range of applications according to the implement fitted to the loader. Examples of where compact wheel loaders may be used include digging, grading, and carrying materials.

[003] In compact wheel loaders typical of the art the hydraulic circuit also controls the steering system. Some compact wheel loaders may include an auxiliary implement in addition to the main implement, and in such compact wheel loaders the main implement is fitted to the front of the loader and the auxiliary implement is fitted at the rear of the loader. For this reason the auxiliary implement is also referred to as a ‘rear auxiliary implement’. The auxiliary implement is also powered by the hydraulic circuit.

[004] With multiple systems being powered by the hydraulic circuit, there is a need to ensure important systems are supplied with sufficient hydraulic fluid from the hydraulic circuit. In compact wheel loaders typical of the art the hydraulic circuit is configured to prioritize the steering system. The term steering system as used here typically includes the braking system as well. The main implement is given the next priority by the hydraulic circuit in compact wheel loaders typical of the art.

[005] US patent publication US2011/0252778 to Deere & Company discloses a hydraulic system for controlling supply priorities. The system uses two priority valves connected in parallel to a hydraulic pump. One of the values prioritizes supply to a first load over an optional second load according to a load-pressure line from the first load. The other value supplies a third load and is controlled by a load-pressure line which is the

-2greater of the load-pressure lines from the first and second loads via a shuttle valve.

[006] Three-way pressure-compensated valves can also be used to prioritize the distribution of hydraulic fluid in a hydraulic circuit, however such three-way valves are expensive.

Summary of the Disclosure [007] In accordance with one aspect of the present disclosure, a hydraulic system is provided for a compact wheel loader having a hydraulic circuit. The hydraulic circuit comprises a hydraulic reservoir and a pump that distributes hydraulic fluid in the hydraulic reservoir to a steering circuit, a main implement circuit and a rear auxiliary circuit. The hydraulic system comprises first and second priority valves, each having a supply input, a primary output, a secondary output, and a control input. The first priority valve is connected at its supply input to the pump and connected at its primary output to the steering circuit, the control input of the first priority valve being connected to a loadsensing line from the steering circuit. The second priority valve is connected at its supply input to the secondary output of the first priority valve, connected at its primary output to the rear auxiliary circuit, and connected at its secondary output to the main implement circuit, the control input of the second priority valve being connected to a load-sensing line from the rear auxiliary circuit, wherein hydraulic fluid is supplied, in order of priority, to the steering circuit, then to the rear auxiliary circuit, and then to the main implement circuit. [008] In accordance with another aspect of the present disclosure, a compact wheel loader is provided having a main implement and a main implement circuit for supply of hydraulic fluid to operate the main implement, a rear auxiliary implement and a rear auxiliary circuit for supply of hydraulic fluid to operate the rear auxiliary implement, and a steering circuit for supply of hydraulic fluid to a steering system. The compact wheel loader comprises a reservoir of hydraulic fluid and a pump that distributes hydraulic fluid in the hydraulic reservoir to the steering circuit, the main implement circuit and the rear auxiliary circuit via a hydraulic system. The hydraulic system comprises first and second priority valves, each having a supply input, a primary output, a secondary output, and a control input. The first priority valve is connected at its supply input to the pump and connected at its primary output to the steering circuit, the control input of the first priority valve being connected to a load-sensing line from the steering circuit. The second priority valve being connected at its supply input to the secondary output of the first priority valve,

-3connected at its primary output to the rear auxiliary circuit, and connected at its secondary output to the main implement circuit, the control input of the second priority valve being connected to a load-sensing line from the rear auxiliary circuit, wherein hydraulic fluid is supplied, in order of priority, to the steering circuit, then to the rear auxiliary circuit, and then to the main implement circuit.

[009] In accordance with another aspect of the present disclosure, a method is provided for distributing hydraulic fluid in a compact wheel loader having a hydraulic circuit comprising a hydraulic reservoir and a pump that distributes hydraulic fluid in the hydraulic reservoir to a steering circuit, a main implement circuit and a rear auxiliary circuit. The method comprises providing a first priority valve that directs hydraulic fluid from the pump to the steering circuit, and further directs hydraulic fluid to a second priority valve according to a pressure in a steering circuit load sense line connected to the first priority valve. The second priority valve is configured to direct hydraulic fluid received from the first priority valve to the rear auxiliary circuit, and to further direct hydraulic fluid to the main implement circuit according to a pressure in a rear auxiliary circuit load sense line connected to the second priority valve, wherein hydraulic fluid is supplied, in order of priority, to the steering circuit, then to the rear auxiliary circuit, and then to the main implement circuit.

[010] Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings [Oil] FIG. 1 illustrates a compact wheel loader in which embodiments of the present disclosure may be employed;

[012] FIG. 2 illustrates a hydraulic system according to embodiments of the present disclosure; and [013] FIG. 3 illustrates a method for distributing hydraulic fluid in a compact wheel loader according to embodiments of the present disclosure.

Detailed Description [014] Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer

-4to the same or corresponding parts. Moreover, references to various elements described herein, are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims.

[015] FIG. 1 illustrates a compact wheel loader 10 in which embodiments of the present disclosure may be employed. The compact wheel loader 10 includes a cabin 12 in which steering controls 14 are provided for operator control of the compact wheel loader

10. A main implement 16, in the form of a snow plough, is provided at a front of the compact wheel loader 10. A rear auxiliary implement 18, in the form of a salt spreader, is provided at a rear of the compact wheel loader 10. The operator may control operation of the main implement 16 and the rear auxiliary implement 18 using controls (not shown) in the cabin 12. Such controls may take any suitable form known to those skilled in the art. [016] Referring now to FIG. 2, the compact wheel loader includes a hydraulic circuit 20 comprising a hydraulic reservoir 22 and a pump 24 that distributes hydraulic fluid from the hydraulic reservoir 22 to a steering circuit 26, a main implement circuit 28 and a rear auxiliary circuit 30 via a hydraulic system 32.

[017] One example form of the steering circuit 26 is shown in FIG. 2. The steering circuit 26 controls a supply of hydraulic fluid to a steering system 34 in response to operator use of the steering controls 14. The main implement circuit 28 shown in FIG. 2 takes the form of a valve that controls a supply of hydraulic fluid to operate the main implement 16. Similarly, the rear auxiliary circuit 30 shown in FIG. 2 takes the form of a valve that controls a supply of hydraulic fluid to operate the rear auxiliary implement 18. Other suitable forms, known to the skilled person, of the steering circuit 26, the main implement circuit 28 and the rear auxiliary circuit 30 may be used in other embodiments, according to the application requirements.

[018] The hydraulic system 32 comprises a first priority valve 36 and a second priority valve 38. The hydraulic system 32 supplies hydraulic fluid from the pump 24 to the steering circuit 26, the main implement circuit 28 and the rear auxiliary circuit 30 according to a priority order, as will be described below.

[019] The first priority valve 36 has a supply input 40, a primary output 42, a

-5secondary output 44, and a control input 46. The supply input 40 of the first priority valve 36 is connected to the pump 24. The primary output 42 is connected to the steering circuit 26. The secondary output 44 is connected to a supply input 48 of the second priority valve 38. The control input 46 is connected to a load-sensing line 50 of the steering circuit 26. [020] The first priority valve 36 may be a dynamic load-sensing priority valve in some embodiments, in which an orifice 52 provided between the primary output 42 and the control input 46. The orifice 52 may be provided internally to the first priority valve 36. In some embodiments of the present disclosure, it may be preferred that the first priority valve 36 is a dynamic load-sensing priority valve, as it has been found this arrangement reduces judder in the steering system 34 and provides smoother operator experience of the steering controls 14.

[021] The first priority valve 36 may comprise a 3/2 control valve having a valve slide 54 movable between a first valve slide position 56 and a second valve slide position 58. The valve slide 54 may be biased towards the first valve slide position 56 by a spring 60. When the valve slide 54 is in the first valve slide position 56, hydraulic fluid flows from the supply input 40 to the primary output 42 while no hydraulic fluid flows to the secondary output 44. When the valve slide 54 is in the second valve slide position 58, hydraulic fluid flows from the supply input 40 to both the primary output 42 and the secondary output 44. Flow to the primary output 42 is constrained when the valve slide 54 is in the second valve slide position 58, for instance by the valve slide 54 partially obstructing the primary output 42. The first priority valve 36 prioritizes supply of hydraulic fluid from the pump 24 to the steering circuit 26, with excess flow being supplied to the second priority valve 38 according to a pressure in the load-sensing line 50 from the steering circuit 26.

[022] In addition to the supply input 48, the second priority valve 38 has a primary output 62, a secondary output 64, and a control input 66. The primary output 62 is connected to the rear auxiliary circuit 30. The secondary output 64 is connected to the main implement circuit 28. The control input 66 is connected to a load-sensing line 68 from the rear auxiliary circuit 30.

[023] The second priority valve 38 may comprise a 3/2 control valve of similar configuration to the first priority valve 36 with the exception that the second priority valve 38 may omit the orifice 52. Like reference numerals in the second priority valve 38 are used to show like parts to those in the first priority valve 36. In the configuration shown in

-6FIG. 2, the second priority valve 38 may be a static load-sensing priority valve. The second priority valve 38 prioritizes supply of hydraulic fluid, received from the first priority valve 36, to the rear auxiliary circuit 30, with excess flow being supplied to the main implement circuit 28 according to a pressure in the load-sensing line 68 from the rear auxiliary circuit 30. In the event that the rear implement 18 is removed from the compact wheel loader 10, the second priority valve 38 will provide fluid pressure to the main implement 16.

[024] While embodiments of the present disclosure have been described with reference to the first priority valve 36 being a dynamic load-sensing priority valve and the second priority valve 38 being a static load-sensing priority valve, other combinations and types of priority valves may also be used. For instance, in some embodiments, the first and second priority valves 36, 38 may both be static load-sensing priority valves, both be dynamic load-sensing priority valve, or the first priority valves 36 may be a static priority valve and the second priority 38 valve may be a dynamic priority valve. Other types and combinations of priority valves, as would be apparent to a skilled person, may also be used.

Industrial Application [025] Embodiments of the present disclosure provide a hydraulic system 32 in which the first and second priority valves 36, 38 are provided in series and configured to prioritize supply of hydraulic fluid, in order, to the steering circuit 26, the rear auxiliary circuit 30, and then the main implement circuit 28.

[026] As the name suggests, typically in the art the rear auxiliary implement circuit is provided with a lower priority for supply of hydraulic fluid than the main implement circuit. However, the arrangement of the present disclosure may be particularly advantageous with some combinations of main implements and rear auxiliary implements. For instance, it has been found that prioritizing supply of hydraulic fluid to a salt spreader attached as a rear auxiliary implement over a snow plough attached as the main implement may provide improved performance of the compact wheel loader 10 in this configuration, since a more consistent distribution of salt is achieved.

[027] Further, the hydraulic system 32 of the present disclosure requires fewer components than hydraulic systems typical of the art, reducing the cost of providing a compact wheel loader where the rear auxiliary implement is prioritized over the main implement. For instance, the hydraulic system 32 of the present disclosure omits shuttle

-7valves in the load-pressure lines typical of prior art systems.

[028] FIG 3 illustrates a method 100 for distributing hydraulic fluid in a compact wheel loader according to embodiments of the present disclosure. At step 102, the method provides a first priority valve that directs hydraulic fluid from the pump to the steering circuit, and further directs hydraulic fluid to a second priority valve according to a pressure in a steering circuit load sense line connected to the first priority valve.

[029] At step 104, the second priority valve is configured to direct hydraulic fluid received from the first priority valve to the rear auxiliary circuit, and to further direct hydraulic fluid to the main implement circuit according to a pressure in a rear auxiliary circuit load sense line connected to the second priority valve.

[030] At step 106, hydraulic fluid is supplied, in order of priority, to the steering circuit, then to the rear auxiliary circuit, and then to the main implement circuit.

[031] While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

Claims

1. A hydraulic system for a compact wheel loader having a hydraulic circuit comprising a hydraulic reservoir and a pump that distributes hydraulic fluid in the hydraulic reservoir to a steering circuit, a main implement circuit and a rear auxiliary circuit, the hydraulic system comprising:

first and second priority valves, each having a supply input, a primary output, a secondary output, and a control input;

the first priority valve being connected at its supply input to the pump and connected at its primary output to the steering circuit, the control input of the first priority valve being connected to a load-sensing line from the steering circuit;

the second priority valve being connected at its supply input to the secondary output of the first priority valve, connected at its primary output to the rear auxiliary circuit, and connected at its secondary output to the main implement circuit, the control input of the second priority valve being connected to a load-sensing line from the rear auxiliary circuit;

wherein hydraulic fluid is supplied, in order of priority, to the steering circuit, then to the rear auxiliary circuit, and then to the main implement circuit.

2. The compact wheel loader of claim 1, wherein the main implement comprises a snow plough and the rear auxiliary implement comprises a salt spreader, whereby the hydraulic system prioritizes supply of hydraulic fluid to the salt spreader over the snow plough.

3. The hydraulic system of claim 1 or 2, wherein the hydraulic system omits the use of shuttle valves in the load-sensing lines.

4. The hydraulic system of claim 3, wherein the first priority valve comprises a dynamic load-sensing priority valve.

5. The hydraulic system of claim 4, wherein the first priority valve comprises an orifice provided between the primary output and the control input.

6.

The hydraulic system of claim 5, wherein the second priority valve comprises a

-9static load-sensing priority valve.

7. A compact wheel loader having a main implement and a main implement circuit for supply of hydraulic fluid to operate the main implement, a rear auxiliary implement and a rear auxiliary circuit for supply of hydraulic fluid to operate the rear auxiliary implement, and a steering circuit for supply of hydraulic fluid to a steering system, comprising:

a reservoir of hydraulic fluid;

a pump that distributes hydraulic fluid in the hydraulic reservoir to the steering circuit, the main implement circuit and the rear auxiliary circuit via a hydraulic system;

the hydraulic system comprising:

the second priority valve being connected at its supply input to the secondary output of the first priority valve, connected at its primary output to the rear auxiliary circuit, and connected at its secondary output to the main implement circuit, the control input of the second priority valve being connected to a loadsensing line from the rear auxiliary circuit;

8. The compact wheel loader of claim 7, wherein the main implement comprises a snow plough and the rear auxiliary implement comprises a salt spreader, whereby the hydraulic system prioritizes supply of hydraulic fluid to the salt spreader over the snow plough.

9. The hydraulic system of claim 7 or 8, wherein the hydraulic system omits the use of shuttle valves in the load-sensing lines.

-1010. The compact wheel loader of claim 9, wherein the first priority valve comprises a dynamic load-sensing priority valve.

11. The compact wheel loader of claim 10, wherein the first priority valve comprises an 5 orifice provided between the primary output and the control input.

12. The compact wheel loader of claim 11, wherein the second priority valve comprises a static load-sensing priority valve.

10

13. A method for distributing hydraulic fluid in a compact wheel loader having a hydraulic circuit comprising a hydraulic reservoir and a pump that distributes hydraulic fluid in the hydraulic reservoir to a steering circuit, a main implement circuit and a rear auxiliary circuit, the method comprising:

providing a first priority valve that directs hydraulic fluid from the pump to the

15 steering circuit, and further directs hydraulic fluid to a second priority valve according to a pressure in a steering circuit load sense line connected to the first priority valve;

configuring the second priority valve to direct hydraulic fluid received from the first priority valve to the rear auxiliary circuit, and to further direct hydraulic fluid to the

20 main implement circuit according to a pressure in a rear auxiliary circuit load sense line connected to the second priority valve;

Intellectual

Property

Office

Application No: GB 1620971.0