HYDRAULIC FLUID TANK ARRANGEMENT

Abstract

A hydraulic fluid tank arrangement for a working machine is provided, the arrangement including a hydraulic fluid tank; an inlet portion for receiving hydraulic fluid into the hydraulic fluid tank; and an oil filter arranged in fluid communication with the inlet portion; wherein the hydraulic fluid tank arrangement further includes a gas removal device arranged in fluid communication with the oil filter downstream the inlet portion and upstream the oil filter for removing gas from the hydraulic fluid before the hydraulic fluid reaches the oil filter. A method for removing gas from hydraulic fluid contained in a hydraulic fluid tank arrangement is also provided.

Claims

1. A hydraulic fluid tank arrangement (200) for a working machine (101), the arrangement (200) comprising a hydraulic fluid tank (202); an inlet portion (206) for receiving hydraulic fluid (204) into the hydraulic fluid tank (202); and an oil filter (220) arranged in fluid communication with the inlet portion (206); characterized in that the hydraulic fluid tank arrangement (200) further comprises a gas removal device (212) arranged in fluid communication with said oil filter (220) downstream said inlet portion (206) and upstream said oil filter (220) for removing gas (218) from the hydraulic fluid before the hydraulic fluid reaches the oil filter (220).

2. The hydraulic fluid tank arrangement (200) according to claim 1, further comprising an outlet portion (208) for providing hydraulic fluid out from the hydraulic fluid tank (202).

3. The hydraulic fluid tank arrangement (200) according to claims 1 or 2, wherein the hydraulic fluid tank (202) comprises a first hydraulic fluid chamber (228), the gas removal device (212) being arranged in fluid communication with the first hydraulic fluid chamber (228) for providing gas removed from the hydraulic fluid into the first hydraulic fluid chamber (228).

4. The hydraulic fluid tank arrangement (200) according to claims 2 or 3, wherein the hydraulic fluid tank (202) comprises a second hydraulic fluid chamber (230), the second hydraulic fluid chamber (230) being arranged downstream said oil filter (220) in fluid communication with the oil filter (220) and the outlet portion (208) of the hydraulic fluid tank arrangement (200).

5. The hydraulic fluid tank arrangement (200) according to claim 4 when dependent on claim 3, wherein the first hydraulic fluid chamber (228) is in fluid communication with the second hydraulic fluid chamber (230).

6. The hydraulic fluid tank arrangement (200) according to claim 3, further comprising a venting filter (338) arranged in communication with the first hydraulic fluid chamber (228) for directing gas in the first hydraulic fluid chamber out from the hydraulic fluid tank arrangement (200).

7. The hydraulic fluid tank arrangement (200) according to any one of the preceding claims, wherein the gas removal device (212) comprises a gas outlet portion (216) for evacuating the gas removed from the hydraulic fluid out from the gas removal device (212).

8. The hydraulic fluid tank arrangement (200) according to claim 4 when dependent on claim 3, wherein the hydraulic fluid tank arrangement (200) further comprises a separation wall (232) dividing the hydraulic fluid tank (202) into the first hydraulic fluid chamber (228) and the second hydraulic fluid chambers (230), said separation wall (232) extending from an upper wall (234) of the hydraulic fluid tank (202) to a level below the gas outlet portion (216).

9. The hydraulic fluid tank arrangement (200) according to claim 8, wherein the separation wall (232) comprises an opening (336) for directing gas in the second hydraulic fluid chamber (230) into the first hydraulic fluid chamber (228).

10. The hydraulic fluid tank arrangement (200) according to claim 2, wherein the hydraulic fluid tank arrangement (200) comprises a pump (210) arranged in fluid communication with the outlet portion (208) downstream said outlet portion (208).

11. The hydraulic fluid tank arrangement (200) according to any one of the preceding claims, wherein the gas removal device (212) is a cyclone deaerator.

12. A working machine (101) comprising a hydraulic fluid tank arrangement (200) according to any one of claims 1-11.

13. A method for removing gas from hydraulic fluid contained in a hydraulic fluid tank arrangement (200) comprising a hydraulic fluid tank (202), wherein the method comprises the steps of: providing (S1) hydraulic fluid to an inlet portion (206) of said hydraulic fluid tank arrangement (200); directing (S2) said hydraulic fluid through a gas removal device (212) arranged in downstream fluid communication with said inlet portion (206) for removing gas from the hydraulic fluid; and directing (S3) said hydraulic fluid to an oil filter (220) arranged in downstream fluid communication with said gas removal device (212).

14. The method according to claim 13, wherein the hydraulic fluid tank (202) comprises a first hydraulic fluid chamber (228), the gas removal device (212) being arranged in fluid communication with the first hydraulic fluid chamber (228), wherein the method further comprises the step of: providing (S4) the gas removed from the hydraulic fluid into the first hydraulic fluid chamber (228).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above, as well as additional features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

[0038] FIG. 1 is a lateral side view illustrating a working machine in the form of a wheel loader having an implement for loading operations, and a hydraulic system for operating the implement and steering the wheel loader;

[0039] FIG. 2 shows a schematic view illustrating a hydraulic fluid tank arrangement according to an example embodiment of the present invention;

[0040] FIG. 3 shows a perspective view of a gas removal device according to an example embodiment of the present invention;

[0041] FIG. 4 is a top view of the interior configuration of the exemplary gas removal device depicted in FIG. 3; and

[0042] FIG. 5 is a flow chart of a method for removing gas from hydraulic fluid contained in a hydraulic fluid tank according to an example embodiment of the present invention.

DETAIL DESCRIPTION

[0043] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

[0044] FIG. 1 is a lateral side view illustrating a working machine 101 in the form of a wheel loader having an implement 102 for loading operations. The term “implement” is intended to comprise any kind of tool using hydraulics, such as a bucket, a fork or a gripping tool arranged on a wheel loader, or a container arranged on an articulated hauler. The implement illustrated in FIG. 1 comprises a bucket 103 which is arranged on an arm unit 104 for lifting and lowering the bucket 103. The bucket 103 can also be tilted or pivoted relative to the arm unit 104. The wheel loader 101 is provided with a hydraulic system comprising at least one hydraulic machine (not shown in FIG. 1). According to an example embodiment, and as depicted in FIG. 2, the hydraulic machine can be a hydraulic pump 210. The wheel loader 101 further comprises two hydraulic cylinders 105a, 105b for the operation of the arm unit 104 and a hydraulic cylinder 106 for tilting the bucket 103 relative to the arm unit 104. Furthermore, the hydraulic system comprises working cylinders 107a, 107b for turning the wheel loader by means of relative movement of a front body 108 and a rear body 109. In other words, the working machine is frame-steered by means of the steering cylinders 107a, 107b.

[0045] Reference is now made to FIG. 2 which illustrates a hydraulic fluid tank arrangement 200 according to an example embodiment of the present invention. The hydraulic fluid tank arrangement 200 comprises a hydraulic fluid tank 202 arranged to be provided with hydraulic fluid 204. The hydraulic fluid 204 can, for example, be hydraulic oil. The specific type of hydraulic fluid is however not a scope of the present invention and depends of course on the specific use and purpose. Moreover, the hydraulic fluid tank arrangement further comprises an inlet portion 206 and an outlet portion 208. The inlet portion 206 is configured to receive hydraulic fluid 204 from hydraulically operated arrangements of the working machine, such as e.g. the above described hydraulic cylinders 105a, 105b, 106 depicted and described in relation to FIG. 1. Hence, after the hydraulic fluid has been used for operation of the hydraulic cylinders, the hydraulic fluid is provided into the hydraulic tank 202 through the inlet portion 206. The outlet portion 208 on the other hand is a position of the hydraulic fluid tank arrangement 200 where the hydraulic fluid 204 is evacuated from the hydraulic fluid tank 202 to e.g. the hydraulic cylinders depicted in FIG. 1. Hence, when the hydraulic cylinder is to be operated, the hydraulic fluid is drawn out of the outlet portion 208 of the hydraulic fluid tank 202. For this purpose, the outlet portion 208 is in fluid communication with a hydraulic pump 210 that forces the hydraulic fluid out from the hydraulic fluid tank 202. The hydraulic pump 210 is in the example embodiment depicted in FIG. 3 in downstream fluid communication with the outlet portion 208.

[0046] Moreover, the hydraulic fluid tank arrangement 200 further comprises a gas removal device 212 arranged in downstream fluid communication with the inlet portion 206. More specifically, a fluid inlet 222 of the gas removal device 212 is arranged in fluid communication with the inlet portion 206. An example embodiment of the gas removal device 212 is described below in relation to FIGS. 3 and 4. The gas removal device may also be referred to as a deaerator and is configured to remove gas from the hydraulic fluid 204 entering the hydraulic fluid tank, which will be further described below. Moreover, the gas removal device 212 may be arranged in downstream fluid communication with the inlet portion 206 by means of an inlet conduit 214. Still further, the gas removal device 212 comprises a gas outlet portion 216 through which the removed gas is configured to be evacuated. Although the gas removal device 212 is depicted in FIG. 2 as positioned within the hydraulic fluid tank 202, the present invention is equally applicable with a gas removal device 212 arranged and positioned on the exterior of the hydraulic fluid tank 202.

[0047] Furthermore, the hydraulic fluid tank arrangement 200 comprises an oil filter 220. The oil filter 220 is arranged in downstream fluid communication with the gas removal device 212. More specifically, the oil filter 220 is arranged in fluid communication with a fluid outlet 224 of the gas removal device 212. Hereby, hydraulic fluid 204 will be directed into the oil filter 220 after passing through the gas removal device 212. The oil filter 220 may be arranged in fluid communication with the gas removal device 212 by means of an outlet conduit 226 arranged between the gas removal device 212 and the oil filter 220.

[0048] The hydraulic fluid tank 202 further comprises a first 228 and a second 230 hydraulic fluid chamber. The gas removal device 212 is arranged in fluid communication with the first hydraulic fluid chamber 228 and the oil filter 220 is arranged in fluid communication with the second hydraulic fluid chamber 230. In detail, and as depicted in the example embodiment of FIG. 2, the gas outlet portion 216 of the gas removal device 212 is arranged in upstream fluid communication with the first hydraulic fluid chamber 228 and the oil filter 220 is arranged in upstream fluid communication with the second hydraulic fluid chamber 230. The gas bubbles 218 removed from the hydraulic fluid 204 will thus be provided into the first hydraulic fluid chamber 228 via the gas outlet portion.

[0049] Moreover, the first 228 and the second 230 hydraulic fluid chambers are arranged in fluid communication with each other, which means that hydraulic fluid is allowed to be transported between the first 228 and the second 230 hydraulic fluid chambers without passing through the oil filter 220. However, the first 228 and second 230 hydraulic fluid chambers are separated from each other by means of a separation wall 232 which extends from an upper wall 234 of the hydraulic fluid tank 202 down to a level below the gas outlet portion 216. Hereby, the gas 218 removed from the hydraulic fluid 204 will be provided into the first hydraulic fluid chamber 228 at a vertical level above a lower end position of the separation wall 232. Furthermore, the separation wall 232 is provided with an opening 336 for allowing air present in the second hydraulic fluid chamber 230 to be transported into the first hydraulic fluid chamber 228 and further out through the hydraulic fluid tank arrangement 200 via a venting filter 338. Although only one venting filter 338 is depicted in FIG. 2, the present invention may function equally as well with a separate venting filter for each of the first 228 and the second 230 hydraulic fluid chambers. In such a case there is no need for an opening 336 in the separation wall 232.

[0050] Reference is now made to FIGS. 3 and 4 which illustrate an example embodiment of a gas removal device 212. More specifically, the example embodiment depicted in FIGS. 3 and 4 is a cyclone deaerator. According to the embodiment depicted in FIG. 3, the gas removal device 212 comprises the fluid inlet 222 at an upper portion of the gas removal device, and the fluid outlet 224 at a lower portion of the gas removal device 212. Also, a gas outlet portion 216 is arranged at the top surface 302 of the gas removal device 212. In detail, the gas outlet portion 216 is provided with a restriction 304, here in the form of an orifice. The restriction 304 is arranged in such a way as to force the main part of the hydraulic fluid entering the gas removal device 212 to be forced out through the fluid outlet 224. In more detail, the hydraulic fluid entering the gas removal device will have a slight overpressure which may force the hydraulic fluid to be directed to the same outlet as the gas bubbles. The gas outlet portion 216, with its restriction 304, thus prevents the main part of the hydraulic fluid from being directed into the first hydraulic fluid chamber 228. This is achieved since the gas bubbles have much lower viscosity than the hydraulic fluid, which will allow the gas bubbles to be directed through the restriction while preventing the hydraulic fluid from being provided therethrough. The specific dimensions of the gas outlet portion 216 and the restriction 304 are of course depending on the specific use, quality of hydraulic fluid, etc., and the present invention should hence not be construed as limited to a specific dimension thereof.

[0051] With particular reference to FIG. 4, when the hydraulic fluid 204 enters the gas removal device 212 through the fluid inlet 222, the hydraulic fluid 204 comprises gas bubbles 218. The hydraulic fluid 204 and the gas bubbles 218 are thus provided to the internal area of the gas removal device 212. Within the gas removal device 212, the hydraulic fluid 204 is exposed to a rotating movement around an axial geometric axis of the gas removal device 212. Hereby, the hydraulic fluid 204 will be exposed to a circumferential movement 402 as well as an axial movement downwards towards the fluid outlet 224 of the gas removal device 212. During the movement of the hydraulic fluid, the gas bubbles 218 will be forced towards a center of the gas removal device 212 and the hydraulic fluid will be forced towards the inlet periphery of the gas removal device 212 due to the difference in density between the gas bubbles 218 and the hydraulic fluid 204. In detail, the gas bubbles 218 have lower density in comparison to the hydraulic fluid 204 which will force the gas bubbles 218 towards the center and the hydraulic fluid towards the periphery of the gas removal device 212. The gas bubbles will hence have a radial force 404 pulling the gas bubbles towards the center and a tangential force 406 pulling the gas bubbles 218 in the circumferential direction of the gas removal device 212. When the gas bubbles 218 are in a center portion of the gas removal device 212 they will rise towards the gas outlet portion 216 and further into the first hydraulic chamber 228 of the hydraulic fluid tank 202. This is caused by the lower gravity of the gas bubbles in comparison to the hydraulic fluid, as well as the slight overpressure that arise in the gas removal device 212 when forcing hydraulic fluid into the fluid inlet 222 of the gas removal device 212.

[0052] Finally, reference is now made to FIG. 5 in combination with FIG. 2 in order to more clearly describe a method for removing gas from hydraulic fluid of the above described hydraulic fluid tank arrangement 200 according to an example embodiment of the present invention.

[0053] After the hydraulic fluid 204 has been used to operate e.g. one of the hydraulic cylinders of the wheel loader depicted in FIG. 1, the hydraulic fluid is provided S1 to the inlet portion 206 of the hydraulic fluid tank arrangement 200. At this stage, the hydraulic fluid 204 comprises gas bubbles 218 which are generated in the hydraulic fluid 204 during operation of the hydraulic cylinders. Thereafter, the hydraulic fluid 204 is directed S2 through the gas removal device 212. In detail, the hydraulic fluid is provided into the fluid inlet 222 of the gas removal device 212. In the gas removal device 212, the gas bubbles 218 are separated from the hydraulic fluid as described above in relation to FIG. 4. The hydraulic fluid 204, which is substantially free from, or at least only contains a heavily reduced number of gas bubbles 218 is further directed S3 to the oil filter 220. The gas bubbles 218 on the other hand move S4 through the gas outlet portion 216 of the gas removal device 212 and into the first hydraulic fluid chamber 228, where the gas bubbles 218 will rise towards the hydraulic fluid surface and crack.

[0054] The hydraulic fluid which was provided to the oil filter 220 is thereafter further directed through the oil filter 220 and into the second hydraulic fluid chamber 230. Once the hydraulic fluid 204 is provided in the second hydraulic fluid chamber 230 it can be used to operate, for example, the hydraulic cylinders of the working machine. This is achieved by forcing the hydraulic fluid out from the second chamber through the outlet portion 208 by means of the hydraulic pump 210.

[0055] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.