By-pass valve for hydraulic filter

Abstract

This utility model relates to a bypass valve for hydraulic filters, belonging to the field of hydraulic technology. Addressing the problem of low sealing reliability caused by radial sealing with an O-ring in the annular groove of the center rod in existing bypass valves, which results in easy wear and breakage of the O-ring, this utility model proposes a technical solution to replace the radial sealing with an end-face sealing. The bypass valve includes a center rod, valve seat, valve core, sealing gasket, support gasket, spring, spring support, and nut. The right end face of the valve core has a stepped sealing groove, housing the sealing gasket and support gasket. The center hole of the sealing gasket is interference-fitted with the center rod, and annular protrusions are provided on both sides. It is pre-tightened by the spring, spring support, and anti-loosening nut. The sealing gasket thickness far exceeds the diameter of existing O-rings, making it less prone to damage during assembly. The stepped groove limits excessive compression, the annular protrusions enhance the sealing effect, and the semi-threaded center rod reduces sliding friction. This utility model significantly improves sealing reliability and durability, increases assembly qualification rate, and is suitable for various hydraulic filters, ensuring normal oil flow in the system when the filter element is clogged or during cold starts.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic technology, specifically to a bypass valve for a hydraulic filter. Background Technology

[0002] In hydraulic systems, hydraulic filters are critical components for ensuring oil cleanliness, intercepting contaminants through their filter elements to prevent wear on downstream components. To avoid filter element clogging or damage caused by a sudden increase in system pressure during cold starts, filters typically integrate bypass valves. These valves automatically open when the pressure difference across the filter element exceeds a predetermined value, allowing unfiltered oil to flow directly downstream and ensuring continuous system operation. The sealing performance and operational reliability of the bypass valve directly affect the filter's filtration efficiency and system safety; its structural design must balance sealing effectiveness with assembly feasibility.

[0003] In the prior art, the closest bypass valve structure is as follows: Figure 1 As shown, the system includes components such as a center rod 1, valve seat 2, valve core 3, O-ring 31, spring 6, and nut 8. The center rod's optical shaft section is machined with an annular groove, within which an O-ring 31 with a cross-sectional diameter of 0.4~0.8mm is placed. The O-ring 31 forms a radial seal with the valve core's central hole, preventing upstream oil from leaking directly to the downstream without being filtered by the filter element. This structure became the mainstream design for early hydraulic filter bypass valves due to the low procurement cost of the O-ring 31 (a standard national standard part) and its simple installation method (groove positioning).

[0004] Although the above structure is widely used in hydraulic systems, it has the following key drawbacks: 1. O-rings 31 are prone to wear and breakage, resulting in a low assembly qualification rate.

[0005] Because the bypass valve is relatively small in size, the O-ring 31 has a wire diameter of only 0.4~0.8mm. During assembly, it needs to be embedded in the annular groove of the center rod. During this process, the O-ring 31 is prone to scratches or breakage due to friction with the edge of the groove. In addition, the O-ring 31 is in radial line contact with the center hole of the valve core. After long-term sliding, it is easy to lose its sealing ability due to friction and wear.

[0006] 2. Poor sealing reliability and high maintenance costs.

[0007] In the existing technology, the sealing effect of O-ring 31 depends on its radial compression. However, the elastic deformation range of small-diameter O-ring 31 is limited. When the system pressure fluctuates or the temperature changes, it is easy to cause leakage due to insufficient compression. If a custom-made large-size O-ring 31 is used, the groove structure needs to be redesigned, which significantly increases the cost (the price of a custom-made sealing ring is 3 to 5 times that of a standard part).

[0008] In early hydraulic component designs, radial seals were preferred due to their simple structure (low difficulty in groove machining) and high versatility (standard O-rings 31 are readily available), leading to the technical path of "center rod groove + O-ring 31". Existing technologies have not considered the optimization of the sealing direction (from radial to axial) and the seal carrier (from center rod to valve core), resulting in the long-standing problem of seal susceptibility.

[0009] Existing bypass valves for hydraulic filters employ a radial sealing structure of "center rod annular groove + small-diameter O-ring 31," which suffers from drawbacks such as easy wear and breakage of the O-ring 31 during assembly, low sealing reliability, and high maintenance costs, making it difficult to meet the long-term stable operation requirements of hydraulic systems. Therefore, an improved bypass valve structure is urgently needed to address the shortcomings of existing technologies and improve sealing reliability and durability through optimized sealing methods and seal design. Utility Model Content

[0010] The purpose of this utility model is to provide a bypass valve for a hydraulic filter, which changes the position of the sealing ring between the center rod and the valve core from inside the annular groove of the center rod to inside the end face sealing groove of the valve core outside the center rod, and changes the radial seal to an end face seal, thereby improving the reliability and durability of the seal.

[0011] To achieve the above objectives, the present invention provides a bypass valve for a hydraulic filter, comprising a center rod, a valve seat, a valve core, a sealing gasket, a support gasket, a spring, a spring support, and a nut. The central rod passes through the valve seat and valve core axially, and its right end is provided with a threaded section; The valve core is conical, wider on the right and narrower on the left, with a beveled surface on its circumferential surface; the valve core slides axially with the central rod, and its right end face is recessed axially to form a sealing groove. The valve seat is cylindrical, with threads on its radial outer circumference and screwed onto the filter base. Its central hole contacts the inclined surface of the valve core to form a sealing fit. The valve seat is provided with distributed oil flow channels. A sealing gasket and a support gasket are arranged sequentially from left to right in the sealing groove, and the central hole of the sealing gasket is interference-fitted with the central rod. The right side of the support pad is pressed against the spring, and the spring is pre-tightened by the spring support and the nut. The nut is threadedly connected to the threaded section of the center rod and locks the spring support.

[0012] Two annular protrusions are provided on each of the two end faces of the sealing gasket at intervals. The left annular protrusion is pressed tightly against the bottom of the sealing groove, and the right annular protrusion is pressed tightly against the support pad.

[0013] The sealing groove is a stepped groove, including a first step and a second step. The first step accommodates the support pad, and the second step accommodates the sealing pad. The depth of the second step is less than the thickness of the sealing pad.

[0014] The central rod is a semi-threaded central rod, with a threaded section at the right end for connecting a nut.

[0015] The nut is a lock-lock nut. After being threadedly connected to the threaded section of the center rod, the spring is pre-tightened by pressing the spring support with the end face.

[0016] This utility model has the following advantages: The sealing groove 23 on the right end face of the valve core 3 accommodates the sealing gasket 4 and the support gasket 5, changing the traditional radial seal between the center rod 1 and the valve core 3 to an end face seal. This increases the sealing area (the sealing gasket thickness is about 2mm, far exceeding the O-ring wire diameter of 0.4~0.8mm), making it less prone to wear during assembly. The sealing gasket 4 and the support gasket 5 work together to bear the force, and the preload of the spring 6 is evenly transmitted to the sealing gasket 4 through the support gasket 5, avoiding excessive local pressure that could lead to deformation, and significantly improving the sealing reliability and durability.

[0017] The annular protrusion 24 transforms the sealing surface from planar contact to line contact, increases local contact pressure, improves the interface fit between the sealing gasket 4 and the bottom of the sealing groove 23 and the support pad 5, and forms multiple sealing barriers to further prevent hydraulic oil leakage.

[0018] The stepped groove structure limits the leftward movement of the support pad 5, preventing excessive pressure from the spring 6 that could cause excessive compression of the sealing gasket 4, thus limiting the amount of deformation of the sealing gasket 4 under pressure and extending its service life. At the same time, the layered containment design makes the assembly and positioning of the sealing gasket 4 and the support pad 5 more precise.

[0019] This utility model eliminates the radial groove on the optical axis of the center rod 1, avoiding scratches on the seal during assembly due to the edge of the traditional groove, and simplifies the processing of the center rod 1; the semi-threaded design only sets the thread at the right end, ensuring that the valve core 3 slides smoothly along the optical axis and reducing frictional resistance.

[0020] The anti-loosening nut 8 can prevent the preload from decreasing due to vibration, ensure the pressure of the spring 6 is stable, and prevent the sealing gasket 4 from failing due to insufficient preload. The opening pressure of the bypass valve can be precisely controlled by adjusting the compression of the spring 6 through the nut 8. Attached Figure Description

[0021] Figure 1 This is a cross-sectional structural diagram that is closest to the existing bypass valve for hydraulic filters.

[0022] Figure 2 This is a cross-sectional structural schematic diagram of the bypass valve for the hydraulic filter in this utility model.

[0023] Figure 3 This is an enlarged cross-sectional view of the sealing gasket. Detailed Implementation

[0024] like Figures 1 to 3As shown, this utility model provides a bypass valve for a hydraulic filter, including a center rod 1, a valve seat 2, a valve core 3, a sealing gasket 4, a support gasket 5, a spring 6, a spring support 7, and a nut 8; The central rod 1 passes through the valve seat 2 and the valve core 3 axially, and its right end is provided with a threaded section; The valve core 3 is conical in shape, wider on the right and narrower on the left, with a beveled surface on its circumferential surface; the valve core 3 slides axially with the central rod 1, and its right end face is recessed axially to form a sealing groove 23. The valve seat 2 is cylindrical, with threads on its radial outer circumference and screwed onto the filter base. Its central hole contacts the inclined surface of the valve core 3 to form a sealing fit. The valve seat 2 is provided with symmetrically distributed oil passages 21. The sectional view direction of the attached drawing determines that only one oil passage 21 can be shown in the attached drawing.

[0025] The sealing groove 23 is provided with a sealing gasket 4 and a support gasket 5 from left to right, and the central hole of the sealing gasket 4 is interference-fitted with the central rod 1. The right side of the support pad 5 is pressed against the spring 6. The spring 6 is pre-tightened through the spring support 7 and the nut 8. The nut 8 is threadedly connected to the threaded section of the center rod 1 and locks the spring support 7.

[0026] The sealing groove 23 on the right end face of the valve core 3 accommodates the sealing gasket 4 and the support gasket 5, changing the traditional radial seal between the center rod 1 and the valve core 3 to an end face seal. This increases the sealing area (the sealing gasket thickness is about 2mm, far exceeding the O-ring wire diameter of 0.4~0.8mm), making it less prone to wear during assembly. The sealing gasket 4 and the support gasket 5 work together to bear the force, and the preload of the spring 6 is evenly transmitted to the sealing gasket 4 through the support gasket 5, avoiding excessive local pressure that could lead to deformation, and significantly improving the sealing reliability and durability.

[0027] The sealing gasket 4 is made of nitrile rubber or fluororubber, and the diameter of the center hole is 0.1~0.3mm smaller than the shaft diameter of the center rod 1 (interference fit); the concentricity of the left end hole of the valve seat 2 (used to pass through the center rod 1) and the 2b inclined hole (fitting with the inclined surface of the valve core 3) is not less than ∅0.1, and the coaxiality of the center hole of the valve core 3 and the inclined surface is not less than ∅0.1.

[0028] During normal operation, the spring 6 pushes the valve core 3 to the left through the support pad 5 and the sealing pad 4, and the inclined surface of the valve core 3 fits against the inclined hole of the valve seat 2, sealing the upstream oil passage; when the upstream oil pressure exceeds the set value, the valve core 3 compresses the spring 6 and moves to the right, and the upstream oil flows downstream through the oil passage 21 and the gap between the valve core 3 and the valve seat 2.

[0029] Two annular protrusions 24 are provided on each of the two end faces of the sealing gasket 4. The left annular protrusion 24 is pressed and engaged with the bottom of the sealing groove 23, and the right annular protrusion 24 is pressed and engaged with the support pad 5.

[0030] The annular protrusion 24 transforms the sealing surface from planar contact to line contact, increases local contact pressure, improves the interface fit between the sealing gasket 4 and the bottom of the sealing groove 23 and the support pad 5, and forms multiple sealing barriers to further prevent hydraulic oil leakage.

[0031] The setting of the annular protrusion 24 must match the elastic deformation of the sealing gasket 4 to ensure that the protrusion undergoes elastic compression without plastic deformation under the preload of the spring 6.

[0032] The sealing groove 23 is a stepped groove, including a first step and a second step. The first step accommodates the support pad 5, and the second step accommodates the sealing pad 4. The depth of the second step is less than the thickness of the sealing pad 4.

[0033] The stepped groove structure limits the leftward movement of the support pad 5, preventing excessive pressure from the spring 6 that could cause excessive compression of the sealing gasket 4, thus limiting the amount of deformation of the sealing gasket 4 under pressure and extending its service life. At the same time, the layered containment design makes the assembly and positioning of the sealing gasket 4 and the support pad 5 more precise.

[0034] The center rod 1 is a semi-threaded center rod, and its optical axis portion is not provided with radial grooves, with only the right end having a threaded section for connecting the nut 8.

[0035] This utility model eliminates the radial groove on the optical axis of the center rod 1, avoiding scratches on the seal during assembly due to the edge of the traditional groove, and simplifies the processing of the center rod 1; the semi-threaded design only sets the thread at the right end, ensuring that the valve core 3 slides smoothly along the optical axis and reducing frictional resistance.

[0036] The surface roughness Ra of the optical axis portion of center rod 1 is ≤1.6μm. Center rod 1 is made of 45 steel with a quenched and tempered finish, with a hardness of HRC28~32, to ensure sufficient strength and wear resistance.

[0037] The nut 8 is a lock nut. After being threadedly connected to the threaded section of the center rod 1, the spring 6 is pre-tightened by pressing the spring support 7 on the end face.

[0038] The anti-loosening nut 8 can prevent the preload from decreasing due to vibration, ensure the pressure of the spring 6 is stable, and prevent the sealing gasket 4 from failing due to insufficient preload. The opening pressure of the bypass valve can be precisely controlled by adjusting the compression of the spring 6 through the nut 8.

[0039] Nut 8 is a hexagonal flange anti-loosening nut with a thread specification that matches the thread section of the center rod 1. The contact area between the flange and the spring support 7 is not less than the cross-sectional area of ​​the spring 6.

[0040] The working process of this utility model is described below.

[0041] I. Sealing process under normal filtration conditions.

[0042] When the hydraulic filter is working normally, the filter element is not clogged, and the upstream oil pressure is lower than the bypass valve opening threshold. At this time, the spring 6 applies a preload through the spring support 7 and the nut 8, pushing the support pad 5 to press the sealing gasket 4 to the left. Under the pressure of the support pad 5, the left annular protrusion 24 of the sealing gasket 4 fits tightly with the bottom of the sealing groove 23 of the valve core 3, and the right annular protrusion 24 contacts the support pad 5. The central hole hugs the central rod 1 due to the interference fit (the hole size is smaller than the shaft diameter of the central rod 1), forming a triple seal: the end face seal between the sealing gasket 4 and the bottom of the sealing groove 23, the end face seal between the sealing gasket 4 and the support pad 5, and the radial clamping seal between the sealing gasket 4 and the central rod 1.

[0043] Under the thrust of spring 6, valve core 3 moves to the left, and its conical inclined surface contacts the inclined hole of valve seat 2, sealing the oil flow channel 21 of valve seat 2. The upstream oil can only flow downstream after being filtered by the filter element, thus achieving normal filtration function. During this process, the thickness of sealing gasket 4 (approximately 2mm) far exceeds the diameter of traditional O-rings (0.4~0.8mm), and the first step of stepped groove 23 restricts the support pad 5 from excessively moving to the left, avoiding plastic deformation of sealing gasket 4 and significantly improving sealing reliability and durability.

[0044] II. Bypass opening process when the filter element is clogged or during a cold start.

[0045] When the filter element becomes clogged or a cold start causes the upstream oil pressure to rise to the bypass valve opening pressure (typically 0.7~1.2MPa), the upstream oil enters the upstream oil chamber (22) through the oil passage 21 of the valve seat 2, generating a rightward thrust on the left conical surface of the valve core 3. This thrust overcomes the preload of the spring 6, pushing the valve core 3 to slide axially to the right along the center rod 1. The valve core 3 separates from the inclined surface of the valve seat 2, forming an annular gap. The upstream oil flows to the downstream oil circuit through this gap, achieving the bypass function.

[0046] During this process, the valve core 3 moves to the right, causing the sealing gasket 4 and support gasket 5 in the sealing groove 23 to move to the right simultaneously. The spring 6 is further compressed, and the spring support 7 is locked to the threaded section of the central rod 1 by the nut 8, ensuring the stable transmission of the compression force of the spring 6. Since the optical axis of the central rod 1 has no annular groove, the sliding friction resistance of the valve core 3 is smaller, and the sealing gasket 4 and the central rod 1 are in surface contact rather than the line contact of the traditional O-ring, which greatly reduces the wear rate and extends the service life of the seal.

[0047] III. Shutdown and reset process after pressure recovery.

[0048] When the filter element clogging problem is resolved or the system temperature rises, causing the viscosity to decrease and the upstream oil pressure to drop below the opening threshold, the elastic restoring force of spring 6 pushes the support pad 5, sealing gasket 4, and valve core 3 to move to the left. The conical inclined surface of valve core 3 re-fits the inclined hole of valve seat 2, closing the connection between oil passage 21 and the downstream oil passage. Under the pressure of support pad 5, sealing gasket 4 achieves triple sealing again. The semi-threaded design of center rod 1 (threaded only at the right end) ensures the guiding accuracy of valve core 3 during reset. The anti-loosening function of nut 8 prevents the preload of spring 6 from decaying due to vibration, ensuring that the bypass valve can still accurately reset after multiple open-close cycles, maintaining stable sealing performance.

[0049] The above embodiments are only used to illustrate and not limit the technical solutions of this utility model. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the utility model without departing from the spirit and scope of the utility model. Any modifications or partial substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A hydraulic filter by-pass valve characterized by: Includes center rod (1), valve seat (2), valve core (3), sealing gasket (4), support pad (5), spring (6), spring support (7), and nut (8); The central rod (1) passes through the valve seat (2) and the valve core (3) axially, and its right end is provided with a threaded section; The valve core (3) is a cone shape with a larger right side and a smaller left side, and its circumferential surface forms an inclined surface; the valve core (3) is axially slidingly fitted with the central rod (1), and its right end face is recessed along the axial direction to form a sealing groove (23). The valve seat (2) is cylindrical, with threads on its radial outer circumference and screwed onto the filter base. Its central hole contacts the inclined surface of the valve core (3) to form a sealing fit. The valve seat (2) is provided with distributed oil passages (21). The sealing groove (23) is provided with a sealing gasket (4) and a support gasket (5) from left to right. The center hole of the sealing gasket (4) is interference-fitted with the center rod (1). The right side of the support pad (5) is pressed against the spring (6). The spring (6) is pre-tightened by the spring support (7) and the nut (8). The nut (8) is threadedly connected to the threaded section of the center rod (1) and locks the spring support (7).

2. The hydraulic filter by-pass valve according to claim 1, characterized in that: The sealing gasket (4) has two annular protrusions (24) spaced apart on each of its two end faces. The left annular protrusion (24) is pressed against the bottom of the sealing groove (23), and the right annular protrusion (24) is pressed against the support pad (5).

3. The hydraulic filter by-pass valve according to claim 1 or 2, characterized in that: The sealing groove (23) is a stepped groove, including a first step and a second step. The first step accommodates the support pad (5), and the second step accommodates the sealing pad (4). The depth of the second step is less than the thickness of the sealing pad (4).

4. The hydraulic filter by-pass valve of claim 1, wherein: The central rod (1) is a semi-threaded central rod, with a threaded section at the right end for connecting the nut (8).

5. The bypass valve for a hydraulic filter according to claim 1, characterized in that: The nut (8) is a lock nut. After being threaded to the threaded section of the center rod (1), the spring (6) is pre-tightened by pressing the spring support (7) on the end face.

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