Hydraulic oil tank air filter

Abstract

The present invention belongs to an air filter, particularly a hydraulic oil tank air filter. It includes an air filter element disposed inside an air filter element outer cover and communicating with each other. The upper end of an extension pipe is connected to the bottom of the air filter element outer cover, and a fixed filter screen is coaxially sleeved and fixed inside it. The air filter element and the air filter element outer cover are coaxially positioned and sleeved. A pin shaft is inserted and fitted with the central hole of a fixed ring. The outer edge of the piston in the middle of the pin shaft is in a tension fit with the inner wall of the fixed ring. The air holes opened on the inner wall of the fixed ring above and below the piston are respectively in communication with the inside and outside of the air filter element. A positioning member is provided at the bottom of the pin shaft, and first and second return springs are sleeved on the outer sides of the pin shaft below and above the piston. The present invention solves the problems in the prior art that frequent changes in positive and negative pressure inside the fuel tank are likely to cause the fuel tank to crack, etc. It has the advantages of safe and reliable structure and long service life of the fuel tank.

Description

Technical Field

[0001] The present invention belongs to the field of air filters, and particularly relates to a hydraulic oil tank air filter. Background Art

[0002] Air filters are widely used in hydraulic oil tanks. Their functions are as follows: First, when the hydraulic system is working, the liquid level in the oil tank sometimes rises or falls. When it rises, air is discharged from the inside to the outside, and when it falls, air is inhaled from the outside to the inside (while filtering the inhaled air); Second, the air filter is also an oil filling port. The newly injected working oil must pass through the filter and then enter the oil tank, so as to filter out the impurity particles in the oil.

[0003] Purifying the working oil in the hydraulic system is a very important link. The air filter can keep the oil in the oil tank clean, which can not only prevent debris particles from entering the oil tank from the outside, but also extend the working cycle and service life of the oil and components, thus ensuring the normal operation of the hydraulic system. In addition, when the hydraulic system is working, the air filter can maintain the pressure balance between the oil tank and the atmospheric pressure to avoid cavitation of the pump.

[0004] Since the working locations of dump trucks are mostly construction sites and mining areas, the environment is relatively harsh, there is more dust in the air, and the replacement frequency of the air filter element is relatively high. However, due to the driver's untimely replacement, the vehicle continues to work when the filter element is blocked. In this state, the air inside and outside the oil tank cannot be effectively exchanged. When the system sucks oil, a negative pressure will be formed inside the oil tank and the tank plate will contract inward. When the system returns oil, a positive pressure will be formed inside the oil tank and the tank plate will expand outward. The frequent alternation of positive and negative pressures will cause the tank plate of the oil tank to contract / expand frequently. When the number of contractions / expansions reaches the fatigue limit of the oil tank, cracks are likely to occur at relatively weak positions such as the welding of the oil tank and the stretching of the tank plate.

[0005] The patent documents retrieved by the applicant include:

[0006] A utility model patent with the patent number 201320140427.2 discloses a hydraulic oil tank air filter device. The device includes a filter housing and a fuel filling port seat. The top end of the fuel filling port seat is connected to the bottom end of the filter housing. A fuel filling filter screen is installed in the fuel filling port seat, and an air filter is installed in the housing. The top end of the fuel filling port seat is fixed to the bottom end of the filter housing with screws. The bottom of the fuel filling port base is provided with a screw hole and is connected to the oil tank with screws. The main problems existing in the above prior art are as follows: First, the fuel filling port base is provided with a threaded hole to connect with the oil tank, and bolts are needed to fasten it to the oil tank, so the installation is relatively cumbersome; Second, the air filter does not have a bypass valve structure and an anti-overflow structure inside.

[0007] The applicant has not retrieved relevant literature reports in domestic patent documents related to the present application. Summary of the Invention

[0008] The object of the present invention is to provide a hydraulic oil tank air filter, which can effectively reduce the cracking of the welding parts of the oil tank and the stretching parts of the tank plate and head caused by the change of the internal pressure of the oil tank due to the blockage of the air filter element.

[0009] The overall technical concept of the present invention is:

[0010] The hydraulic oil tank air filter includes an air filter element disposed inside the air filter element outer cover and communicating with each other. The upper end of the extension pipe is communicated with the bottom of the air filter element outer cover, and a filter screen is coaxially sleeved and fixed inside it. The air filter element and the air filter element outer cover are coaxially positioned by a rabbet and a fixing ring. The pin shaft is inserted and fitted with the central hole of the fixing ring. The outer edge of the piston disposed in the middle of the pin shaft is in tight fit with the inner wall of the fixing ring. The air holes opened on the inner wall of the fixing ring above and below the piston are respectively communicated with the inside and outside of the air filter element. A positioning member is provided at the bottom of the pin shaft. A first return spring is sleeved outside the pin shaft between the upper part of the piston and the top of the fixing ring, and a second return spring is sleeved outside the pin shaft between the lower part of the piston and the positioning member.

[0011] The specific technical concept of the present invention includes:

[0012] The main function of the positioning member is to facilitate the adjustment and positioning of the second return spring below the piston, and thus adjust the pressure of the piston. The preferred technical implementation means is that the positioning member includes a nut threadedly engaged with the pin shaft and a gasket above it.

[0013] To prevent the positioning member from coming out from below the pin shaft, the preferred technical implementation method is that a split pin is provided on the pin shaft below the positioning member.

[0014] To facilitate the sealing between the extension pipe and the bottom of the air filter element outer cover, the preferred technical implementation means is that the upper end of the extension pipe is communicated with the bottom of the air filter element outer cover and a sealing ring is provided at the connection part.

[0015] To prevent the overflow of hydraulic oil, the preferred technical implementation means is that a float switch is provided at the bottom of the extension pipe.

[0016] The preferred structural design of the float switch is that the float switch includes a sealing frame assembled at the lower part of the extension pipe. The positioning piece is located on the central hole of the sealing frame. The positioning piece is connected with the float through a connecting rod. A conical seal can be formed between the upper part of the float and the central hole of the sealing frame.

[0017] To facilitate the positioning of the fixing ring, the preferred technical implementation means is that the fixing ring and the air filter element outer cover are threadedly assembled with the upper cover.

[0018] The applicant needs to explain:

[0019] In the description of the present invention, the orientation or positional relationship indicated by terms such as "upper end", "bottom", "inside", "outer edge", "inner wall", "upper part", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of simplifying the description of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention. The terms "first" and "second" in the present invention are only for the purpose of describing the differences between components and cannot be construed as implying importance.

[0020] To verify the technical effects of the present invention, the applicant conducted the following tests:

[0021] I. Air flow rate and anti-fatigue tests of the fuel tank panel and head

[0022] When the air filter element is blocked, the air flow rate of the filter element decreases, and the filter element cannot effectively exchange the air inside and outside the fuel tank when the vehicle is lifted / lowered. After testing the internal pressure of the fuel tank (the filter element is blocked): when the vehicle is lifted (the hydraulic system sucks oil), the internal pressure of the fuel tank is negative pressure, reaching a maximum of 0.05 MPa; when the vehicle is lowered (the hydraulic system returns oil), the internal pressure of the fuel tank is positive pressure, reaching a maximum of 0.03 MPa. In addition, the deformation of the fuel tank was tested. When the internal pressure of the fuel tank is 0.03 MPa, the deformation of its head is 4 mm; when the internal pressure is 0.05 MPa, the deformation of its head is 6 mm. As the number of operations of the vehicle hydraulic system increases, the fuel tank panel and head will break after reaching the material fatigue strength, and then oil will leak from the crack.

[0023] After testing, when the air filter of the hydraulic oil tank in the present invention is blocked (the air filter element has been blocked after 3 months of use in the market), during the vehicle lifting process, the internal air pressure of the oil tank ≤ 0.01 MPa, and during the vehicle lowering process, the internal pressure of the oil tank ≤ 0.005 MPa. The air filter of the dump truck requires an air flow rate of 1350 L / min to ensure that no pressure is generated inside the oil tank during the vehicle lifting and lowering processes. The hydraulic oil tank air filter in the present invention can still meet the requirements when the filter element is blocked (the air flow rate reaches 1350 L / min when the filter element is blocked); the deformation of the oil tank is tested: the deformation at the head of the oil tank during the lifting and lowering processes is less than 1 mm. After testing, when the air filter element is blocked, during the vehicle lifting (hydraulic system oil suction), the internal of the oil tank is in negative pressure, reaching a maximum of 0.05 MPa, and during the vehicle lowering (hydraulic system oil return), the internal of the oil tank is in positive pressure, reaching a maximum of 0.03 MPa. In addition, the deformation of the oil tank is tested. When the internal pressure of the oil tank is 0.03 MPa, the deformation of the head is 4 mm, and when the internal pressure is 0.05 MPa, the deformation of the head is 6 mm. As the number of operations of the vehicle hydraulic system increases, the tank plate and head of the oil tank will break after reaching the material fatigue strength, and then oil will leak from the crack. The tests in the past year using the present invention have confirmed that the situation of the oil tank plate cracking has decreased from 5% before use to 0.03%, with significant economic benefits.

[0024] II. Service life of air filter element

[0025] The present invention can effectively prevent the filter element from being blocked due to oil soaking, and extends the service life of the filter element. It has been confirmed by the applicant's tests that no phenomenon of filter element soaking has been found for one year after installing the present invention. The air filter element of the original structure needs to be replaced after 2 - 3 months of use. The service life of the filter element of the new structure air filter reaches an average of 6 - 7 months, and the service life is extended by 2 - 3 times. The new structure air filter extends the maintenance period of users and reduces the maintenance cost at the same time.

[0026] The substantial features and significant technical progress of the present invention are as follows:

[0027] 1. A two-way bypass device is added to the air filter. When the air filter element is blocked, the internal of the hydraulic oil tank exchanges air with the outside through the bypass device to keep the pressure inside and outside the oil tank consistent. It has been confirmed by the applicant's tests that using the present invention significantly reduces the deformation of the tank body caused by the pressure change inside the tank due to this reason, and further reduces the situation of cracking, with significant economic benefits.

[0028] 2. When the air filter element is blocked by particulate matter, due to the structural design of the piston, fixed ring, return spring, etc., the pressure adjustment can be conveniently realized. The opening pressure of the piston is adjusted by the positioning component, with a simple structure, convenient pressure adjustment, and convenient installation.

[0029] 3. The structural design of the sealing frame and the floating ball can effectively prevent oil spillage. The sealing frame and the floating ball can be separately molded, and the structure is simple. The adoption of the above structure significantly extends the service life of the filter element and greatly reduces the maintenance and repair costs of the filter element. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings of the present invention are as follows:

[0031] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0032] The reference numerals in the drawings are as follows:

[0033] 1. Upper cover; 2. Fixed ring; 3, 4. Outer cover of air filter element; 5. Sealing ring; 6. Filter screen; 7. Extension pipe; 8. Sealing frame; 9. Floating ball; 10. Positioning piece; 11. Split pin; 12. Nut; 13. Gasket; 14. Pin shaft; 15. Second return spring; 16. Piston; 17. First return spring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The embodiments of the present invention will be further described below with reference to the drawings, but it is not a limitation to the present invention. The protection scope of the present invention is subject to the content recorded in the claims. Any equivalent technical means substitution based on the description of the specification does not depart from the protection scope of the present invention.

[0035] Embodiment

[0036] The overall structure of this embodiment is as shown in the figure, which includes an air filter element 3 disposed inside the outer cover 4 of the air filter element and communicating with each other. The upper end of the extension pipe 7 is connected to the bottom of the outer cover 4 of the air filter element, and a filter screen 6 is coaxially sleeved and fixed inside it. The air filter element 3 and the outer cover 4 of the air filter element are coaxially positioned by a rabbet and a fixed ring 2. The pin shaft 14 is inserted and matched with the central hole of the fixed ring 2. The outer edge of the piston 16 provided in the middle of the pin shaft 14 is in tight fit with the inner wall of the fixed ring 2. The air holes opened on the inner wall of the fixed ring 2 above and below the piston 16 are respectively communicated with the inside and outside of the air filter element 3. A positioning member is provided at the bottom of the pin shaft 14, and the positioning member includes a nut 12 threadedly engaged with the pin shaft and a gasket 13 above it. A first return spring 17 is sleeved outside the pin shaft 14 between the upper part of the piston 16 and the top of the fixed ring 2, and a second return spring 15 is sleeved outside the pin shaft 14 between the lower part of the piston 16 and the positioning member.

[0037] A split pin 11 is provided on the pin shaft 14 below the positioning member.

[0038] The upper end of the extension pipe 7 is connected to the bottom of the outer cover 4 of the air filter element, and a sealing ring 5 is provided at the connection part.

[0039] A float switch is provided at the bottom of the extension pipe 7. The float switch includes a sealing frame 8 assembled at the lower part of the extension pipe 7. A positioning piece 10 is located on the central hole of the sealing frame 8. The positioning piece 10 is connected to the float 9 through a connecting rod. A conical seal can be formed between the upper part of the float 9 and the central hole of the sealing frame 8.

[0040] The fixing ring 2 and the air filter outer cover 4 are threadedly assembled with the upper cover 1.

[0041] The working principle of this embodiment is as follows:

[0042] 1. The air filter is in a clean state

[0043] When the hydraulic system sucks oil, the liquid level in the fuel tank drops. Air enters the inside of the air filter outer cover 4 from the openings above the side and the bottom surface of the air filter outer cover 4, and enters the hydraulic fuel tank through the air filter 3. When the hydraulic system returns oil, the liquid level in the fuel tank rises. The air in the fuel tank enters the inside of the extension pipe 7 through the sealing frame 8, then enters the inside of the air filter 3 through the filter screen 6, and after being filtered, enters the cavity between the air filter outer cover 4 and the air filter 3, and finally exits from the openings above the side and the bottom surface of the air filter outer cover 4.

[0044] 2. The air filter is in a state of being blocked by particulate matter

[0045] When the hydraulic system sucks oil, the liquid level in the fuel tank drops. Air enters the inside of the air filter outer cover 4 from the openings above the side and the bottom surface of the air filter outer cover 4. Since the air filter 3 is blocked and the air flow rate through the filter decreases, the external air cannot enter the fuel tank in time, causing a negative pressure to be formed in the fuel tank. The negative pressure acts on the lower surface of the piston 16, causing it to move downward and compress the second return spring 15. At this time, part of the air inside the air filter outer cover 4 will enter the hydraulic fuel tank after passing through the air filter 3 and being filtered, and part of the air enters the hydraulic fuel tank through the opening above the fixing ring 2 and the air holes opened on the inner wall of the fixing ring 2 above and below the piston 16, ensuring that the pressure inside the fuel tank is the same as the external atmospheric pressure. When the system finishes sucking oil, the piston 16 will return to the middle position under the action of the second return spring 15. When the hydraulic system returns oil, the liquid level in the fuel tank rises. Air needs to be discharged. However, since the air filter 3 is blocked by particulate matter and the air flow rate decreases, the pressure inside the fuel tank will increase. The air pressure acts on the piston 16, causing it to move upward and compress the first return spring 17 at the same time. The air enters the inside of the air filter outer cover 4 through the opening above the fixing ring 2 and the air holes opened on the inner wall of the fixing ring 2 above and below the piston 16, and exits from the openings above the side and the bottom surface of the air filter outer cover 4. When the system finishes returning oil, the piston 16 will return to the middle position under the action of the first return spring 17.

[0046] 3. Anti-overflow oil device

[0047] Due to phenomena such as system oil leakage, the oil level in the fuel tank will decrease. And if the driver fails to refuel in time, there will be a situation where the hydraulic oil in the fuel tank of some dump trucks cannot meet the requirements for the cylinder to lift. When the vehicle continues to lift with the system running out of oil, the gear pump will suck in air, and the air will enter the hydraulic cylinder. When the vehicle descends, the oil returns to the hydraulic fuel tank. At this time, the inhaled air mixes with the hydraulic oil, causing the oil to foam. This situation will increase the volume of the hydraulic oil in the fuel tank. When the volume of the oil returning to the fuel tank exceeds the volume of the hydraulic fuel tank, the bubbles will overflow from the fuel filler port and soak the air filter 3 (the filter element is a paper filter). After being soaked and attached with dust, it will accelerate the blockage of the air filter 3.

[0048] When the volume of the hydraulic oil in the fuel tank increases and the liquid level reaches the top of the fuel tank, the float ball 9 will move upward under the action of buoyancy. The float ball 9 and the central hole of the sealing frame 8 form a conical seal to prevent the oil from overflowing. When the system returns oil and the air in the fuel tank is discharged outward, due to the self-weight of the float ball 9, the air pressure cannot push the float ball 9 upward, and the float ball 9 and the sealing frame 8 are in an open state. The air is discharged outward from the openings on the sealing frame 8. When the oil return is completed and the bubbles disappear, the float ball 9 will return to its free state under the action of gravity.

Claims

1. Hydraulic oil tank air filter, including an air filter element (3) arranged inside an air filter element outer cover (4) and communicating with each other, It is characterized in that The upper end of the extension pipe (7) communicates with the bottom of the air filter element outer cover (4), and a filter screen (6) is coaxially sleeved and fixed inside it. The air filter element (3) and the air filter element outer cover (4) are coaxially positioned by a rabbet and a fixing ring (2). Openings communicating with the inside of the air filter element outer cover (4) are provided above the side surface and the bottom surface of the air filter element outer cover (4). The pin shaft (14) is inserted and matched with the central hole of the fixing ring (2). The outer edge of the piston (16) arranged in the middle of the pin shaft (14) is in tight fit with the inner wall of the fixing ring (2). The air holes opened on the inner wall of the fixing ring (2) above and below the piston (16) are respectively communicated with the inside and outside of the air filter element (3). An opening for communicating with the inside of the air filter element outer cover (4) is opened above the fixing ring (2). A positioning member is arranged at the bottom of the pin shaft (14). A first return spring (17) is sleeved outside the pin shaft (14) between the upper part of the piston (16) and the top of the fixing ring (2). A second return spring (15) is sleeved outside the pin shaft (14) between the lower part of the piston (16) and the positioning member.

2. The hydraulic oil tank air filter according to claim 1, It is characterized in that The positioning member includes a nut (12) threadedly engaged with the pin shaft and a gasket (13) above it.

3. The hydraulic oil tank air filter according to claim 1 or 2, It is characterized in that A split pin (11) is arranged on the pin shaft (14) below the positioning member.

4. The hydraulic oil tank air filter according to claim 1, It is characterized in that The upper end of the extension pipe (7) communicates with the bottom of the air filter element outer cover (4), and a sealing ring (5) is provided at the connecting part.

5. The hydraulic oil tank air filter according to claim 1 or 4, It is characterized in that A float switch is arranged at the bottom of the extension pipe (7).

6. The hydraulic oil tank air filter according to claim 5, It is characterized in that The float switch includes a sealing frame (8) assembled at the lower part of the extension pipe (7). The positioning piece (10) is located on the central hole of the sealing frame (8). The positioning piece (10) is connected with the float (9) through a connecting rod. A conical surface seal can be formed between the upper part of the float (9) and the central hole of the sealing frame (8).

7. The hydraulic oil tank air filter according to claim 1, It is characterized in that The fixing ring (2) and the air filter element outer cover (4) are threadedly assembled with the upper cover (1).

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