CN217582709U - Hydraulic equipment and filter - Google Patents

Abstract

The utility model relates to a hydraulic equipment and filter. This filter includes connecting portion and filter house, wherein: the connecting part is used for being connected with a liquid conveying channel of the hydraulic system and is provided with a first circulation port; the filtering part is provided with a first side surface, a second side surface and a side edge positioned between the first side surface and the second side surface, the second side surface is provided with a second circulation port, and the second circulation port, the inner cavity of the filtering part and the first circulation port are sequentially communicated; when the connecting part is installed in the liquid conveying channel, a first filtering gap is formed between the lateral edge and the inner wall of the liquid conveying channel. The filter is suitable for a hydraulic system, can realize higher filtering precision, and has the advantages of high strength, small failure rate, long service life and difficult damage of filter residues.

Description

Hydraulic equipment and filter

Technical Field

The application relates to the technical field of fluid filtration, in particular to a filter suitable for a hydraulic system and hydraulic equipment provided with the filter.

Background

The filter is a hydraulic element commonly used in a hydraulic system, and can be installed in a plurality of places of an oil suction loop, a pressure pipeline, an oil return pipeline, a bypass system and the like of the system as an element for ensuring the cleanliness of the system.

Common filtration methods used in hydraulic systems include the following:

1) Screen filter

Referring to fig. 1, generally, the steel wire mesh 102 is directly embedded in the bracket 101, and the mesh diameter represents the filtration precision, is convenient to clean, and can be reused, but the filtration precision is generally low, and the common particles with the size of 0.425mm are generally coarse-filtered and are generally 40x40 meshes.

The screen-filtering meshes are washed out, which is often found in after-sales maintenance, and cause the broken wires to contaminate the hydraulic pump motor, the hydraulic valves, and even the entire hydraulic system.

2) Line clearance filtering

Referring to fig. 2, the line gap filtering generally refers to that a metal wire 202 (copper wire or aluminum wire) is wound on a U-shaped framework 201, and oil is filtered through gaps between the metal wires 202, so that the filtering precision is not high.

Therefore, how to design a filter with high filtering precision and difficult damage is a technical problem to be solved urgently by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem, the utility model provides a be applicable to hydraulic system's filter to and a be provided with the hydraulic equipment of this filter, it can realize higher filter fineness, and intensity is high, the fault rate is little, long service life, not fragile the filter residue that appears.

A filter for a hydraulic system, the filter comprising a connection portion and a filter portion, wherein:

the connecting part is used for being connected with a liquid conveying channel of a hydraulic system and is provided with a first circulation port;

the filtering part is provided with a first side surface, a second side surface and a side edge positioned between the first side surface and the second side surface, the second side surface is provided with a second circulation port, and the second circulation port, the inner cavity of the filtering part and the first circulation port are communicated in sequence;

when the connecting part is installed in the liquid conveying channel, a first filtering gap is formed between the lateral edge and the inner wall of the liquid conveying channel.

Optionally, in the above filter, the first filter gap has a gap width of 0.04mm to 0.5mm; alternatively, the first filter gap has a gap width of 0.06mm to 0.15mm.

Optionally, in the above filter, the filter portion is provided with four or six or eight side edges along a circumferential direction, and two sides of each side edge are the first side surface and the second side surface respectively.

Optionally, in the above filter, the first side surface is a plane structure, one end of which is connected to the connecting portion, and the other end of which forms an inlet or an outlet with an inner wall of the liquid conveying passage.

Optionally, in the filter, the second side surface is a planar structure, one end of the second side surface is connected to the connecting portion, and the other end of the second side surface is provided with a flow blocking protrusion;

when the connecting part is installed in the liquid conveying channel, a second filtering gap is formed between the top surface of the flow blocking bulge and the inner wall of the liquid conveying channel.

Alternatively, in the above filter, the liquid delivery passage is a passage circular in cross section, an end opening of which is provided with an internal thread, and:

the connecting part is of a cylindrical structure and is provided with an external thread matched with the internal thread.

Optionally, in the filter, the top surface of the flow blocking protrusion and the side edge are located on the same virtual cylindrical surface.

Optionally, in the above filter, the second circulation port is a polygonal opening.

Optionally, in the filter, a guide portion is further disposed between the connecting portion and the filtering portion, and a diameter of the guide portion is larger than the virtual cylindrical surface and is in clearance fit with an inner diameter of a thread of the connecting portion.

A hydraulic apparatus which is a hydraulic pump or a hydraulic motor, said hydraulic apparatus being provided with a liquid conveying passage, said liquid conveying passage being provided with a filter as described hereinabove.

Optionally, in the hydraulic apparatus, the liquid delivery passage is a control oil passage provided in a rear cover of the hydraulic apparatus, and is configured to deliver hydraulic oil to a hydraulic valve of the hydraulic apparatus.

The filter is fixedly installed in the liquid conveying channel through the connecting part, at the moment, a first filtering gap is formed between the lateral edge of the filtering part and the inner wall of the liquid conveying channel, a first through cavity is formed between the first lateral surface of the filtering part and the inner wall of the liquid conveying channel, and a second through cavity is formed between the second lateral surface of the filtering part and the inner wall of the liquid conveying channel.

Under operating condition, the fluid to be filtered sequentially passes through the first side face, the lateral edge and the second side face, then enters the inner cavity of the filtering part through the second circulation port, and is output to the liquid conveying channel through the first circulation port. Namely, the liquid passes through the first through-flow cavity, the first filtering gap, the second through-flow cavity and the filter inner cavity in sequence. In the process, a first filtering gap formed by the lateral edge of the filtering part and the inner wall of the channel is equivalent to a narrow slit, and impurities/pollutants and the like larger than the width of the slit can be blocked in the first through-flow cavity, so that the impurities/pollutants are prevented from flowing downstream, and a downstream element (such as a downstream control valve) is protected.

It can be seen that by controlling the distance from the side edges of the filter to the central axis of the filter (or the central axis of the liquid conveying channel), the gap width of the first filter gap can be controlled, thereby controlling the filtering accuracy of the filter. Therefore, the filter adopts a 'boundary filtering' mode, and compared with the screen filtering and the line gap filtering, the filter has the advantages that the filtering precision is easy to control, and the high-precision filtering can be realized. In addition, this filter is the integral type structure that obtains through the mode of machining generally, and not only intensity is high, the fault rate is little, long service life, and not fragile filter residue that appears moreover.

Drawings

In order to facilitate understanding of the invention, the invention is described in more detail below on the basis of exemplary embodiments and with reference to the attached drawings. The same or similar reference numbers are used in the drawings to refer to the same or similar parts. It should be understood that the drawings are merely schematic and that the dimensions and proportions of elements in the drawings are not necessarily precise.

FIG. 1 is a schematic view of a screen filter;

FIG. 2 is a schematic view of a line gap filter;

FIG. 3 is an isometric view of a filter having four side edges according to a first embodiment of the present invention;

FIG. 4 is a cross-sectional view of the filter of FIG. 3;

FIG. 5 is a schematic view of the filter of FIG. 3 in an operating condition with liquid flowing around the filter;

FIG. 6 is a schematic view of the filter of FIG. 5 in an operative configuration in cooperation with a fluid delivery passageway;

fig. 7 is a schematic view of the installation structure of the filter in the liquid conveying passage according to the first embodiment of the present invention;

FIG. 8 is an isometric view of a filter having six side edges according to a second embodiment of the present invention;

fig. 9 is an isometric view of a filter having eight side edges according to a third embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

First embodiment

Referring to fig. 3 and 4, a first embodiment of the present invention provides a filter for a hydraulic system. The filter includes a connection portion 301 and a filter portion 302. Wherein: the connecting portion 301 is used for connecting with a liquid delivery passage 400 of the hydraulic system, and is provided with a first communication port 312 at an end portion; the filter portion 302 has a first side 323 and a second side 324, and a side edge 325 between the first side 323 and the second side 324, the second side 324 has a second fluid opening 326, and the second fluid opening 326, the inner cavity of the filter portion 302, and the first fluid opening 312 are sequentially connected.

In specific implementation, the filter is fixedly installed in the liquid conveying channel 400 through the connecting portion 301, in this case, a first filtering gap is formed between the side edge 325 and the inner wall of the liquid conveying channel 400, a first flow cavity is formed between the first side surface 323 and the inner wall of the liquid conveying channel 400, and a second flow cavity is formed between the second side surface 324 and the inner wall of the liquid conveying channel 400.

In an operating state, a fluid to be filtered sequentially passes through the first side 323, the side edge 325, and the second side 324, enters the inner cavity of the filter portion 302 through the second through hole 326, and is output to the liquid conveying channel 400 through the first through hole 312. Namely, the liquid passes through the first flow cavity, the first filtering gap, the second flow cavity and the filter inner cavity in sequence.

The filtering principle of the filter can be seen in fig. 5 to 7:

the direction of the arrows in fig. 5 and 7 indicate the direction of the liquid as it passes through the filter;

d in fig. 6, which is the gap width of the filter gap, relates to the filter accuracy;

after reaching the end of the filter part 302, the oil first enters the first through-flow chamber formed by the first side surface 323 and the inner wall of the passage, then passes through the first filter gap formed by the side edge 325 and the inner wall of the passage, then enters the second through-flow chamber formed by the second side surface 324 and the inner wall of the passage, and finally flows out of the filter through the second through-flow opening 326 and the first through-flow opening 312. In the process, the first filtering gap formed by the side edge 325 and the inner wall of the passage is equivalent to a narrow slit, and can block impurities/pollutants and the like larger than the width of the slit in the first through-flow cavity, so that the impurities/pollutants are prevented from flowing downstream, and downstream elements (such as a downstream control valve) are protected.

It can be seen that by controlling the distance from the side edges 325 of the filter to the central axis of the filter (or the central axis of the fluid delivery channel), the gap width of the first filter gap can be controlled, thereby controlling the filtration accuracy of the filter. It can be seen that the filter adopts a 'boundary filtering' mode, and compared with the screen filtering mode shown in fig. 1 and the line gap filtering mode shown in fig. 2, the filter precision is easy to control, and high-precision filtering can be realized. In addition, this filter is the integral type structure that obtains through the mode of machining generally, and not only intensity is high, the fault rate is little, long service life, and the filter residue that appears is not fragile moreover.

In a specific implementation, the gap width of the first filtering gap may be set to be 0.04mm to 0.5mm, or 0.06mm to 0.15mm. For example, a nominal gap width dimension of 0.125mm for the first filter gap means that all contaminants/pollutants having a dimension greater than 0.125mm cannot pass through the first filter gap between the side edges 325 and the inner wall of the liquid conveying channel 400.

In specific implementation, as shown in fig. 3, 5 and 6, the filter portion 302 of the filter is provided with four side edges 325 along the circumferential direction, and a first side surface 323 and a second side surface 324 are respectively arranged at two sides of each side edge 325. That is, two first side surfaces 323 and two second side surfaces 324 are arranged on the side surfaces of the filter portion 302 in sequence at intervals in the circumferential direction, and a side edge 325 is formed between the adjacent first side surfaces 323 and second side surfaces 324.

In a specific embodiment, the first side 323 preferably has a planar structure, one end of which is connected to the connection portion 301, and the other end of which forms an inlet with the inner wall of the liquid conveying passage 400. The second side surface 324 is preferably a flat surface having one end connected to the connection portion 301 and the other end provided with a flow blocking protrusion. When the connection portion 301 is installed in the liquid delivery passage 400, a second filtering gap is formed between the top surface 322 of the baffle protrusion and the inner wall of the liquid delivery passage 400.

Referring specifically to fig. 3, 5 and 6, the edge 321 of the top surface 322 of the flow-blocking protrusion, which is opposite to the end edge of the connecting portion 301, forms a boundary filter edge intersecting the flow direction of the liquid in the liquid conveying channel 400; the top surface 322 of the baffle projection forms a second filter gap with the inner wall of the fluid delivery passageway 400, which is generally equal to the first filter gap.

In operation, a portion of the fluid to be filtered passes through the second filter gap and directly onto the second side 324, enters the inner cavity of the filter portion 302 through the second communication opening 326, and is output downstream of the liquid delivery channel 400 through the first communication opening 312.

The first side 323 and the second side 324 are planar and can be formed by milling, grinding, casting, and other conventional methods. However, the present invention is not limited to this, as long as it can form a through-flow chamber with the inner wall of the liquid transport passage 400, for the specific structure of the first side 323 and the second side 324.

In summary, the filter has four equal-length side edges 325, which form four boundary filters. In addition, the end of the filter part 302 far from the connection part 301 is provided with two flow blocking protrusions at positions corresponding to the two second side surfaces 324, and the top surface 322 and the end edge 321 form a second filter gap, which also has a boundary filtering effect, so that the filter has six narrow edges for filtering oil.

In general, since the liquid supply passage 400 has a circular cross section, an internal thread for attaching a filter is provided at an end opening thereof. Correspondingly, the connecting portion 301 of the filter has a cylindrical structure and is provided with an external thread 311 adapted to the internal thread. So that the filter can be conveniently fixedly installed in the liquid transfer passage 400 and can be disassembled, inspected and replaced at any time.

In practice, referring to fig. 6, since the cross-section of the liquid conveying channel 400 is generally circular, in order to ensure the same filtering precision in the second filtering gap (formed by the top surface 322 and the end edge 321 of the flow-blocking protrusion of the filtering part and the inner wall of the channel) and the first filtering gap (formed by the side edge 325 and the inner wall of the channel), the side edge 325 at the side of the filtering part 302 and the top surface 322 of the flow-blocking protrusion at the end of the filtering part 302 are located on the same virtual cylindrical surface. That is, the top surface 322 of the baffle protrusion is a partial side surface of the virtual cylinder, each side edge 325 is a generatrix of the virtual cylinder, and the radius difference between the virtual cylinder and the liquid conveying channel 400 is the gap width of the filtering gap, i.e. the filtering precision.

Further, referring to fig. 3 to 5 and fig. 7, in the filter, a guiding portion 303 is further disposed between the connecting portion 301 and the filtering portion 302, and a diameter of the guiding portion 303 is larger than the virtual cylindrical surface and is equal to or slightly smaller than an inner diameter of the liquid conveying channel 400, that is, the guiding portion 303 is in clearance fit with the liquid conveying channel 400. Therefore, when the filter is installed in the liquid conveying channel 400, the guide part 303 can play a certain role in guiding the installation direction of the filter, so that the alignment and screwing of the filter and the liquid conveying channel 400 are facilitated, and the influence on the filtering precision due to the inclination of the filter is prevented. In addition, the guide 303 also substantially prevents fluid from leaking through the guide and threaded portion.

In a specific implementation, the first fluid opening 312 of the filter is a polygonal opening, preferably a hexagonal opening. Therefore, when the filter is attached to the liquid transport passage 400, the filter can be attached to and detached from the liquid transport passage 400 by inserting the polygonal tool into the first communication port 312 and controlling the rotation of the filter.

It will be appreciated that although the above description describes the case where the liquid flows in from the first side 323 and out from the first flow opening 312, the strainer may be fully installed such that the liquid flows in from the first flow opening 312 and out from the first side 323, and the edge and the flow-blocking protrusion still perform a straining function, and will not be described in detail herein.

In a specific implementation, the filter can be used as a high-pressure filter element and integrally arranged on a hydraulic pump or a hydraulic motor element for filtering key components such as a control valve in the hydraulic pump or the hydraulic motor.

To sum up, the utility model also provides a hydraulic equipment, this hydraulic equipment be hydraulic pump or hydraulic motor, and it is provided with liquid conveying channel 400, is provided with above-mentioned filter in the liquid conveying channel 400.

In specific implementation, the liquid conveying channel 400 is a control oil path arranged on a rear cover of the hydraulic equipment and is used for conveying hydraulic oil to a hydraulic valve of the hydraulic equipment. Thus, impurities/contaminants can be prevented from damaging the hydraulic valve by the above-mentioned filter.

Second embodiment

Referring to fig. 8, a second embodiment of the present invention provides a filter for a hydraulic system. This filter differs from the filter of the first embodiment described above only in that: the utility model discloses the filter part 302 of the filter that the second embodiment provided is provided with six arriss 325 along circumference, and the both sides of every arris 325 are first side 323 and second side 324 respectively.

Third embodiment

Referring to fig. 9, a third embodiment of the present invention provides a filter for a hydraulic system. This filter differs from the filter of the first embodiment described above only in that: the utility model discloses the filter part 302 of the filter that the second embodiment provided is provided with eight arriss 325 along circumference, and the both sides of every arris 325 are first side 323 and second side 324 respectively.

In general, the main indexes for measuring filtration include filtration efficiency, compressive strength and flow capacity.

1) Filtration efficiency beta

The filtration efficiency β is an indication of the efficiency and performance of the filter by comparing the number of particles of a given size before and after the filter;

such as:

2) Strength against pressure loss

The pressure loss resistance is the lowest pressure difference limit which can be borne by the filter element, and the internal structure of the filter element can be damaged beyond the limit. When the filter element reaches a certain degree of corking, or cold start, or both, the differential pressure between the inlet (dirty side) and the outlet (clean side) of the filter element increases, and if the differential pressure is too great, the filter element will rupture or collapse.

3) Current capacity

The flow resistance mainly refers to how much resistance or pressure loss the oil has after passing through the filter, and the parameter is related to the viscosity of the oil.

In practice, the gap width of the first filter gap between the side edge 325 of the filter portion 302 and the liquid conveying passage 400 (i.e., d1 shown in fig. 6) and the gap width of the second filter gap between the end edge 321 and the inner wall 400 of the oil duct hole (i.e., d2 shown in fig. 6) can be designed according to the required filtering precision. For example, the nominal size of each filter gap (single sided nominal gap) is designed to be 0.125mm, which means that particles with a size greater than 0.125mm will be filtered and blocked in the oil gallery from entering the control valve system.

For the condition with higher precision requirement, a fine machining mode can be adopted, even a small unilateral nominal gap is obtained by slow wire electrical discharge machining (the precision can reach 0.001 mm), and therefore higher filtering precision is obtained.

However, the improved filtering accuracy also has other effects, such as: the small clearance means that the oil flowing speed is reduced, the pressure loss of the oil passing through the filter is increased, and particularly, under the condition of transient sudden change, the pressure drop is large; this slows the response of the pump. In addition, the method of reducing the filter gap also increases the cost of manufacturing the filter.

Therefore, in the specific implementation, if the through-flow capacity needs to be increased, the through-flow capacity can be increased by increasing the gaps of the narrow edges and adding a plurality of filter edges. Such as:

referring to fig. 8, in a second embodiment of the present invention, the number of the filtering side edges 325 and the number of the end edges 321 in the filter of the first embodiment are increased from 4 to 6, and the number of the second through holes 326 is increased from 4 to 6;

referring to fig. 9, in a third embodiment of the present invention, the number of the filtering side edges 325 and the number of the end edges 321 in the filter of the first embodiment are increased from 4 to 8, and the number of the second through holes 326 is increased from 4 to 8.

This increases the throughflow capacity of the filter. Moreover, the flow capacity of the filter can be ensured even improved under the condition of improving the filtering precision, and the response speed of the hydraulic pump/hydraulic motor is not influenced.

4) Calculation of current capacity

The utility model provides a "border filtering" mode that filter adopted can imagine into the linking together of countless thin wall aperture ideally, forms a line, so we can use the flow formula of thin wall aperture:

to make a calculation that estimates the throughput of narrow-edge filtering.

The amount of control oil liquid required by the variable of the hydraulic pump is not large generally, but has a direct relation with the response speed and the return speed of the pump, the variable oil liquid required by the control variable of different hydraulic pumps is different due to different designed variable mechanism structures, different sizes and the like, and the 193 displacement of an open pump of the Danfoss model is taken as a research object. For the electric proportional control of the pump, if the electric proportional control belongs to a slow variable, about 1L of flow is generally needed; but if a fast variable is required then the instantaneous flow demand can reach 4-5L. We here follow the extreme case 5L.

We take:

the flow coefficient C is 0.61

Flow-through interface A =0.125mm × 11mm (boundary length h) =1.375mm ²

Density =0.875x10 of hydraulic oil ³ kg·m ^-3

Then substituting:

so when the flow rate is 5L, instant Δ P =43bar

Δ P =1.7bar when the flow rate is 1L

The relationship between the increase of the filtration precision and the current capacity is a linear corresponding relationship:

so if the filtration accuracy is improved from 0.125mm to 0.1mm, the flow rate is correspondingly reduced by 20%;

so if the filtration accuracy is improved from 0.125mm to 0.08mm, the flow rate is correspondingly reduced by 36%;

in practical design of the through flow rate, the processing difficulty and the cost increment are also considered.

If the previous 4-side filtering scheme is replaced by 6-side filtering, the oil flow can reach the following value: (1-0.36) × 6/4=1.11

If the previous 4-side filtering scheme is replaced by 8-side filtering, the oil flow can reach the following value: (1-0.36) × 8/4=1.48

Since the pressure difference before and after filtration becomes large when the flow area is reduced, the 8-side filtration is selected in consideration of reducing the pressure difference before and after filtration as much as possible.

It should be noted that, in the specific implementation, the connection portion and the filtering portion of the filter provided by the present invention are generally coaxially disposed, but not limited thereto, and in a specific case, the filtering portion may also be disposed such that the central axis is an arc, a right-angle or an obtuse-angle bending structure, and is adapted to the corresponding portion of the liquid conveying channel. In this case, the liquid supply channel may be of a split construction, so that the filter of this particular shape can be installed. The boundary edge of the filter for forming a filter gap with the inner wall of the liquid conveying channel may be a linear side edge, or may be a spiral shape or other shapes.

It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.

In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A filter for a hydraulic system, characterized in that the filter comprises a connection portion (301) and a filter portion (302), wherein:

the connecting part (301) is used for being connected with a liquid conveying channel (400) of a hydraulic system and is provided with a first circulation port (312);

the filter part (302) is provided with a first side surface (323) and a second side surface (324), and a side edge (325) located between the first side surface (323) and the second side surface (324), the second side surface (324) is provided with a second circulation port (326), and the second circulation port (326), the inner cavity of the filter part (302) and the first circulation port (312) are communicated in sequence;

when the connecting part (301) is installed in the liquid conveying channel (400), a first filtering gap is formed between the side edge (325) and the inner wall of the liquid conveying channel (400).

2. The filter of claim 1, wherein the first filter gap has a gap width of 0.04mm to 0.5mm; alternatively, the gap width of the first filtering gap is 0.06mm to 0.15mm.

3. A filter according to claim 1, characterised in that the filter house (302) is circumferentially provided with four or six or eight side edges (325), each side edge (325) being flanked by a first side face (323) and a second side face (324), respectively.

4. A filter according to claim 1, characterised in that the first side (323) is of planar construction, one end of which meets the connection (301) and the other end of which forms an inlet or outlet with the inner wall of the liquid conveying channel (400).

5. A filter according to claim 4, characterised in that the second side (324) is of a planar configuration, one end of which is connected to the connection (301) and the other end of which is provided with a flow-blocking projection;

when the connecting part (301) is installed in the liquid conveying channel (400), a second filtering gap is formed between the top surface (322) of the flow blocking protrusion and the inner wall of the liquid conveying channel (400).

6. A filter according to claim 5, characterised in that the liquid delivery channel (400) is a channel of circular section, the end opening of which is provided with an internal thread, and in that:

the connecting part (301) is of a cylindrical structure and is provided with an external thread (311) matched with the internal thread.

7. A filter according to claim 5, characterised in that the top surface of the baffle projection is located on the same imaginary cylinder as the lateral edge (325).

8. The filter of claim 7, wherein the first flow port (312) is a polygonal opening;

and/or a guide part is further arranged between the connecting part (301) and the filtering part (302), the diameter of the guide part is larger than the diameter of the virtual cylindrical surface, and the guide part is in clearance fit with the inner diameter of the liquid conveying channel (400).

9. A hydraulic apparatus, which is a hydraulic pump or a hydraulic motor, characterized in that the hydraulic apparatus is provided with a liquid conveying channel (400), and that the liquid conveying channel (400) is provided with a filter according to any one of claims 1-8.

10. The hydraulic apparatus according to claim 9, wherein the liquid delivery channel (400) is a control oil path provided in a rear cover of the hydraulic apparatus for delivering hydraulic oil to a hydraulic valve of the hydraulic apparatus.

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