This Application is a Section 371 National Stage Application of International Application No. PCT/KR2011/010095, filed Dec. 26, 2011 and published, not in English, as WO2012/087081 on Jun. 28, 2012.
The present disclosure relates to an oil pressure system for a wheel loader, and more particularly to a wheel loader which includes an oil pressure system having a confluent circuit and reduces the occurrence of impact during loading work.
A construction machine, such as a wheel loader, performs so-called loading work, and frequently performs an operation of raising a boom connected with a bucket to a predetermined height during the work. For example, in order to transfer a bucket on which a product is loaded to a specific position, such as an upper side of a cargo box of a truck during loading work, the boom connected with the bucket is raised to a position higher than that of the cargo box of the truck.
When the bucket is raised to a position lower than the specific position, there exists a risk of collision between the bucket and the cargo box to damage the bucket. Further, in a case where the boom is raised as described above, the boom is generally controlled at a maximum speed for work efficiency.
For example, force applied to the boom cylinder 22 may be expressed as Equation 1 below based on the illustration of
P=W×L1/L2 cos θ Equation
Here, P means force applied to the boom cylinder 22, W means external force applied to a center point A of the bucket 30, L1 is a length of A-C, L2 is a length of B-C, and θ means an angle of B-D-E.
As described above, the force P applied to the boom cylinder 22 is a function related to an angle between the boom cylinder 22 (for example, B-D of
Accordingly, in a case where the boom cylinder 22 is expanded for loading work, the boom cylinder 22 is generally expanded at a maximum speed to increase work efficiency.
Further, the wheel loader in the related art generally includes a pair of left and right oil pressure pumps in order to drive the front working device, and the pair of left and right oil pressure pumps may supply hydraulic oil to the front working device, such as the boom cylinder, through a so-called confluent circuit.
Further, a predetermined cutoff pressure is set in each oil pressure pump. As a result, the cutoff pressure limits, for example, a pressure range of the boom cylinder, that is, a maximum rising pressure range of the boom, and determines maximum force generable by each oil pressure pump.
For example, as illustrated in
However, as illustrated in
Since the loading work is generally to load a product on the bucket and load the product on a cargo box of a truck, and the like, when the impulse is transferred to the bucket, the product loaded on the bucket may be lost. Further, when the boom cylinder is abruptly halted during the expansion of the boom cylinder at the maximum speed, stress due to the impact may also be accumulated to a whole machine including the boom cylinder.
In order to solve the problem, technology of tracking a position (height) of the boom and controlling a rise of the boom by an electronic control method has been developed. However, for the technology, additional problems, such as complexity of a manufacturing process including a necessity to additionally include required electronic constituent elements, and an increase in cost, may be incurred, and further, a new problem, such as an occurrence of failure by the additionally included electronic constituent elements, may be incurred.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
This summary and the abstract are provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The summary and the abstract are not intended to identify key features or essential features of the claimed subject matter, nor are they intended to be used as an aid in determining the scope of the claimed subject matter.
In order to solve the aforementioned problem, the present disclosure provides an oil pressure system for a wheel loader with an improved raising process of a boom, thereby, especially, decreasing impact generated when the boom approaches a maximum height during loading work.
In order to achieve the above object, the present disclosure provides an oil pressure system for a wheel loader including oil pressure pumps having different cutoff pressures, the wheel loader including: a pair of oil pressure pumps configured to discharge hydraulic oil; a plurality of working devices including a bucket cylinder (such as bucket cylinder 121 depicted in
The present disclosure is characterized by first cutting off an oil pressure pump supplying the hydraulic oil to the working device between the pair of oil pressure pumps.
Further, the present disclosure is characterized in that the different cutoff pressures set in the pair of oil pressure pumps are a maximum cutoff pressure corresponding to a pressure when the boom approaches a maximum height, and a predetermined cutoff pressure corresponding to a pressure when the boom approaches a predetermined height close to the maximum height.
Further, the present disclosure is characterized in that the predetermined height close to the maximum height is a height corresponding to approximately 90% of the maximum height.
According to the present disclosure, it is possible to provide the wheel loader with the improved boom raising process without including an additional electronic constituent element, and the like.
Further, according to the present disclosure, it is possible to decrease generated impact by decreasing a raising speed of the boom when the boom approaches a maximum height, for example, during loading work.
Hereinafter, an exemplary embodiment of the present disclosure will be described with reference to the accompanying drawings.
Referring to
In addition, the pair of left and right oil pressure pumps 110a and 110b is characterized by having different cutoff pressures. For example, a pressure corresponding to a maximum height of the boom is set as a maximum cutoff pressure value in one oil pressure pump (for example, the oil pressure pump 110a) similar to the related art, but a pressure corresponding to a predetermined height close to the maximum height of the boom may be set as a predetermined cutoff pressure value in the other oil pressure pump (for example, the oil pressure pump 110b). For example, as shown in
In the meantime, the present disclosure further requires a sensor (not illustrated) capable of measuring a height of the boom, and the sensor may be configured in a form of an angle sensor installed in the boom cylinder to measure a stroke of the boom cylinder or measure a rotation angle of the boom.
As described above, the wheel loader according to the present disclosure is characterized by setting the different cutoff pressure values for the pair of left and right oil pressure pumps supplying the hydraulic oil through the confluent circuit. The different cutoff pressure values are set for the pair of left and right oil pressure pumps, respectively, so that it is possible to decrease impact generated when raising of the boom at the maximum speed and stopping during the loading work. For example, the present disclosure is characterized by setting a pressure corresponding to the maximum height of the boom as the maximum cutoff pressure value for one oil pressure pump similar to the related art, and setting a pressure corresponding to a height of approximately 90% of the maximum height of the boom as the predetermined cutoff pressure value for the other oil pressure pump according to the characteristic of the present disclosure. In the above description, the prevention of the impact by setting the cutoff pressure has been described as an example. However, when the oil pressure pump 110a is cutoff regardless of the cutoff pressure according to the height of the boom, the similar effect may be induced even in a case where a weight of the products is small, as well as a case where the boom is raised at the maximum pressure. That is, the effect of the boom impact prevention of the present disclosure may also be achieved by restricting, that is, cutting off, the discharge of the hydraulic oil of one oil pressure pump between the pair of oil pressure pumps in response to the height of the boom.
In the oil pressure system in which the pair of oil pressure pumps 110a and 110b are confluent during typical driving of the boom, any one pump supplies the entire hydraulic oil to a front working device including the boom and the bucket, and the other pump divides the hydraulic oil and supplies the hydraulic oil to the aforementioned front working device and an additional device 142, for example, a steering device. In this case, the setting of a low cutoff pressure according to the exemplary embodiment of the present disclosure may be applied to the oil pressure pump 110a supplying the entire hydraulic oil to the front working device. The reason is that a case where the oil pressure pump 110 dividing and supplying the hydraulic oil to another additional device is set to have a low cutoff pressure may have a considerable effect in relieving the impact of the boom promoted in the present disclosure, but may incur other problems due to a shortage of a pressure or a flow of the hydraulic oil supplied to another additional device.
As illustrated in
As described above, when the boom approaches approximately 90% of the maximum height, one oil pressure pump approaches the cutoff pressure, so that the supply of the hydraulic oil from the corresponding oil pressure pump is stopped, and thus the boom is raised only with the pressure of the hydraulic oil discharged from the other remaining oil pressure pump from the height corresponding to approximately 90% of the maximum height to the maximum height (100% height).
Accordingly, as illustrated in
Accordingly, through a simple characteristic of setting the different cutoff pressures for the pair of left and right oil pressure pumps, it is possible to considerably decrease impact applied to the boom, the bucket, and the like at the maximum height of the boom during the loading work, and thus it is possible to considerably decrease a risk of losing a product due to impact, and also considerably decrease the amount of stress accumulated in each constituent element and the like.
Further, according to the characteristic of the present disclosure, since an additional constituent element is not required, it is possible to achieve the object of decreasing the impulse during the loading work to be achieved in the present disclosure without causing an increase in additional costs and inconvenience, such as an increase in complexity of a manufacturing process.
The present disclosure may be used in a wheel loader for decreasing impact generable during loading work.
Although the present disclosure has been described with reference to exemplary and preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the disclosure.
Number | Date | Country | Kind |
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10-2010-0134608 | Dec 2010 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR2011/010095 | 12/26/2011 | WO | 00 | 6/24/2013 |
Publishing Document | Publishing Date | Country | Kind |
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WO2012/087081 | 6/28/2012 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4586330 | Watanabe | May 1986 | A |
7318292 | Helbling | Jan 2008 | B2 |
7637039 | Toda | Dec 2009 | B2 |
20030097836 | Takahashi | May 2003 | A1 |
20040128868 | Helbling | Jul 2004 | A1 |
20090151346 | Kim | Jun 2009 | A1 |
Number | Date | Country |
---|---|---|
09-217384 | Aug 1997 | JP |
11-181842 | Jul 1999 | JP |
2001-248187 | Sep 2001 | JP |
10-2009-0053523 | May 2009 | KR |
Entry |
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Search Report dated Jul. 9, 2012 and written in Korean with English translation attached for International Patent Application No. PCT/KR2011/010095 filed Dec. 26, 2011, 5 pages. |
Number | Date | Country | |
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20130283775 A1 | Oct 2013 | US |