A reversing valve and a braking system

Abstract

The present invention relates to the technical field of brake systems, and discloses a reversing valve and a brake system. The reversing valve includes a housing and a valve core assembly, and the housing is provided with an installation cavity, an oil inlet circuit and an oil return circuit; the valve core assembly is slidably arranged in the installation cavity, and the position of the valve core assembly includes an oil inlet station and an oil return station. When the valve core assembly is located at the oil inlet station, the oil inlet circuit is a passage, and the oil return circuit is an open circuit; when the valve core assembly is located at the oil return station, the oil inlet circuit is an open circuit, and the oil return circuit is a passage; during the process of the valve core assembly moving from the oil return station to the oil inlet station, the open circuit stroke of the oil return circuit is X1, and the passage stroke of the oil inlet circuit is X2, and X1 is less than X2. The present invention realizes the unidirectional flow of hydraulic oil, has a simple structure, low cost, and the oil inlet and the oil return are different, so as to achieve the effect of replenishing and cooling the new oil in the pipeline and the oil cylinder, and solves the problem of high-temperature boiling of oil caused by trapped oil in the pipeline in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of brake systems, and in particular to a reversing valve and a brake system. Background Art

[0002] At present, the control method of single-acting oil circuit in working machinery mostly adopts two-position two-way reversing valve for control. When the oil cylinder extends, the hydraulic oil enters the large cavity of the oil cylinder through the valve. When the oil cylinder retracts, under the action of external force, the oil in the large cavity returns to the original path. Such as the brake caliper in the driver brake system, the brake cylinder in the hydraulic motor, etc. When the cylinder diameter of the single-acting oil cylinder is large, when the oil cylinder retracts, most of the hydraulic oil inside the single-acting oil cylinder will be discharged through the pipeline. When the oil is filled again, the hydraulic oil entering the oil cylinder is new oil that has been circulated.

[0003] However, when the cylinder diameter is small, the amount of oil discharged by the single-acting cylinder at one time is very small, and this part of the oil cannot return to the oil tank through the entire set of hydraulic pipelines. When it is extended next time, the hydraulic oil discharged from the cylinder into the hydraulic pipeline last time is pressed into the cylinder again. If it works repeatedly like this, the hydraulic oil from the pipeline to the hydraulic cylinder will boil at high temperature, causing equipment failure. For example, the brake piston of the brake caliper, the brake disc of the hydraulic motor, etc.

[0004] Based on this, a reversing valve and a braking system are urgently needed to solve the above-mentioned problems. Summary of the invention

[0005] Based on the above, the purpose of the present invention is to provide a reversing valve and a braking system, which realize different oil inlet and oil return routes, thereby achieving the effect of replenishing new oil and cooling the inside of the pipeline and the cylinder, and solving the problem of high-temperature boiling of oil caused by oil trapped in the pipeline in the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, a reversing valve is provided, comprising:

[0008] A housing, wherein the housing is provided with a mounting cavity, an oil inlet passage and an oil return passage;

[0009] A valve core assembly is slidably disposed in the installation cavity, wherein the position of the valve core assembly includes an oil inlet position and an oil return position, wherein when the valve core assembly is located at the oil inlet position, the oil inlet path is a passage and the oil return path is a disconnected path; when the valve core assembly is located at the oil return position, the oil inlet path is a disconnected path and the oil return path is a passage;

[0010] During the movement of the valve core assembly from the oil return station to the oil inlet station, the circuit breaking stroke of the oil return circuit is X1, the passage stroke of the oil inlet circuit is X2, and X1 is smaller than X2.

[0011] As a preferred technical solution of a reversing valve, the reversing valve is a two-position four-way reversing valve, and the reversing valve is provided with an A port, a B port, a P port and a T port, the oil inlet path is formed between the A port and the P port, and the B port and the T port form the oil return path;

[0012] The reversing valve includes an elastic member, which is used to drive the valve core assembly to move to the oil return position; when the pressure of the hydraulic oil at the P port is greater than the elastic force of the elastic member, the hydraulic oil drives the valve core assembly to move to the oil inlet position.

[0013] As a preferred technical solution of the reversing valve, the valve core assembly includes a circulating valve core and a working valve core, the circulating valve core is provided with a first delivery hole, the first end of the first delivery hole is connected to the T port, and when the oil return path is connected, the second end of the first delivery hole is connected to the B port;

[0014] The working valve core is provided with a second delivery hole, a first end of the second delivery hole is connected to the P port, and a second end of the second delivery hole is connected to the A port when the oil inlet passage is opened.

[0015] As an optimal technical solution for a reversing valve, the outer diameter of the circulating valve core is smaller than the outer diameter of the working valve core, the circulating valve core is connected to the working valve core, the elastic member is a spring, the spring is sleeved on the circulating valve core, and one end of the spring abuts against the side wall of the mounting cavity, and the other end abuts against the end face of the working valve core close to one end of the circulating valve core.

[0016] As a preferred technical solution for a reversing valve, the circulation valve core and the working valve core are split structures and are fixedly connected to form a whole.

[0017] As an optimal technical solution for a reversing valve, the valve core assembly also includes a positioning pin and a first retaining spring, the working valve core is provided with a positioning hole, the side wall of the positioning hole is provided with a first pin hole, the circulating valve core is provided with a positioning shaft, the side wall of the positioning shaft is provided with a second pin hole, the positioning shaft extends into the positioning hole, the positioning pin is penetrated through the first pin hole and the second pin hole, and the positioning pin is fixed in the first pin hole by a first retaining spring.

[0018] As a preferred technical solution for a reversing valve, the circulation valve core and the working valve core are integrally formed.

[0019] As a preferred technical solution of a reversing valve, a second retaining spring is installed in the installation cavity, and when the valve core assembly is located at the oil return position, one end of the working valve core away from the circulation valve core abuts against the second retaining spring.

[0020] As an optimal technical solution for a reversing valve, the circulating valve core is stepped, the shell is provided with a first guide hole, the first guide hole is connected to the mounting cavity, the stepped small diameter section slides into the first guide hole, and when the valve core assembly is located at the oil inlet station, the end face of the large diameter section of the circulating valve core abuts against the side wall of the mounting cavity close to one end of the first guide hole.

[0021] As a preferred technical solution for a reversing valve, the small diameter section and the large diameter section are connected by a conical surface, and the first guide hole is provided with a chamfer near one end of the installation cavity, and the chamfer can fit the conical surface; or the first guide hole is provided with a rounded corner near one end of the installation cavity.

[0022] On the other hand, a braking system is provided, comprising a single-acting cylinder, a braking source, an oil return collection device and a reversing valve as described in any of the above schemes, wherein the outlet of the oil inlet circuit and the inlet of the oil return circuit of the reversing valve are respectively connected to the rodless chamber of the single-acting cylinder, the inlet of the oil inlet circuit is connected to the braking source, and the outlet of the oil return circuit is connected to the oil return collection device.

[0023] The beneficial effects of the present invention are:

[0024] The present invention provides a reversing valve, wherein the outlet of the oil inlet circuit and the inlet of the oil return circuit are respectively connected to the rodless chamber of the single-acting oil cylinder, the inlet of the oil inlet circuit is connected to the oil tank through a booster pump, and the outlet of the oil return circuit is connected to the oil tank. In the process of the valve core assembly moving from the oil return station to the oil inlet station, the circuit breaking stroke of the oil return circuit is X1, and the passage stroke of the oil inlet circuit is X2, and X1 is smaller than X2. In the process of the valve core assembly 2 moving from the oil return station to the oil inlet station under the pressure of the hydraulic oil, the oil inlet circuit can be opened only after the oil return circuit is completely disconnected, and there is no leakage in the oil return circuit, thereby ensuring the working pressure of the single-acting oil cylinder. In the process of the valve core assembly moving from the oil inlet station to the oil return station, the oil return circuit will be opened only after the oil inlet circuit is completely closed, ensuring that when the single-acting oil cylinder retracts, the hydraulic oil in the rodless chamber and the pipeline is completely transported to the oil tank through the oil return circuit to complete the circulation. The above structure plays the role of unidirectional flow of hydraulic oil, and has a simple structure and low cost. The present invention realizes different oil inlet and oil return paths, thereby achieving the effect of new oil replenishment and cooling inside the pipeline and the oil cylinder, and solves the problem of high-temperature boiling of oil caused by oil trapped in the pipeline in the prior art.

[0025] The present invention provides a braking system, which includes a single-acting oil cylinder, a braking source, an oil return collection device and the above-mentioned reversing valve. The outlet of the oil inlet circuit and the inlet of the oil return circuit of the reversing valve are respectively connected to the rodless chamber of the single-acting oil cylinder, the inlet of the oil inlet circuit is connected to the braking source, and the outlet of the oil return circuit is connected to the oil return collection device, thereby improving the reliability of the braking system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0027] Figure 1 It is a structural schematic diagram of a reversing valve provided in a specific embodiment of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a braking system provided in a specific embodiment of the present invention.

[0029] The following are marked in the figure:

[0030] 10. Directional valve; 101. Port A; 102. Port B; 103. Port P; 104. Port T;

[0031] 20. Single-acting cylinder; 30. Braking source; 40. Return oil collection device;

[0032] 1. Shell; 11. Mounting cavity; 12. First guide hole; 13. Chamfer; 2. Valve core assembly; 21. Circulation valve core; 211. Positioning shaft; 212. First delivery hole; 213. Large diameter section; 214. Small diameter section; 215. Conical surface; 22. Working valve core; 221. Second delivery hole; 222. Positioning hole; 223. Positioning pin; 224. First retaining spring; 3. Second retaining spring; 4. Elastic member. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0037] like Figure 1 As shown, the present embodiment provides a reversing valve 10, including a housing 1 and a valve core assembly 2, the housing 1 being provided with an installation cavity 11, an oil inlet circuit and an oil return circuit; the valve core assembly 2 is slidably arranged in the installation cavity 11, and the position of the valve core assembly 2 includes an oil inlet position and an oil return position, when the valve core assembly 2 is located at the oil inlet position, the oil inlet circuit is a passage, and the oil return circuit is a disconnection; when the valve core assembly 2 is located at the oil return position, the oil inlet circuit is a disconnection, and the oil return circuit is a passage; in the process of the valve core assembly 2 moving from the oil return position to the oil inlet position, the disconnection stroke of the oil return circuit is X1, and the passage stroke of the oil inlet circuit is X2, and X1 is smaller than X2.

[0038] When in use, the outlet of the oil inlet circuit and the inlet of the oil return circuit are respectively connected to the rodless chamber of the single-acting cylinder, the inlet of the oil inlet circuit is connected to the oil tank through a booster pump, and the outlet of the oil return circuit is connected to the oil tank. In the process of the valve core assembly 2 moving from the oil return station to the oil inlet station, the circuit-breaking stroke of the oil return circuit is X1, and the passage stroke of the oil inlet circuit is X2, and X1 is less than X2. It can be inferred that in the process of the valve core assembly 2 moving from the oil inlet station to the oil return station, the passage stroke of the oil return circuit is X3, and the circuit-breaking stroke of the oil inlet circuit is X4, and X3 is greater than X4. Among them, in the process of the valve core assembly 2 moving from the oil return station to the oil inlet station, it is ensured that the oil inlet circuit can only be opened after the oil return circuit is completely disconnected, and there is no leakage in the oil return circuit, thereby ensuring the working pressure of the single-acting cylinder. During the movement of the valve core assembly 2 from the oil inlet station to the oil return station, the oil return line will be opened only after the oil inlet line is completely closed, ensuring that when the single-acting cylinder retracts, the hydraulic oil in the rodless chamber and the pipeline is completely transported to the oil tank through the oil return line to complete the cycle. The above structure plays the role of unidirectional flow of hydraulic oil, with a simple structure and low cost. This embodiment realizes different oil inlet and oil return lines, thereby achieving the effect of replenishing new oil and cooling the inside of the pipeline and the oil cylinder, and solves the problem of high-temperature boiling of oil caused by trapped oil in the pipeline in the prior art.

[0039] Furthermore, the reversing valve 10 is a two-position four-way reversing valve 10, and the reversing valve 10 is provided with an A port 101, a B port 102, a P port 103 and a T port 104. An oil inlet circuit is formed between the A port 101 and the P port 103, and an oil return circuit is formed between the B port 102 and the T port 104; the reversing valve 10 includes an elastic member 4, and the elastic member 4 is used to drive the valve core assembly 2 to move to the oil return position; when the pressure of the hydraulic oil at the P port 103 is greater than the elastic force of the elastic member 4, the hydraulic oil drives the valve core assembly 2 to move to the oil inlet position.

[0040] During assembly, the A port 101 and the B port 102 of the reversing valve 10 are respectively connected to the rodless chamber of the single-acting oil cylinder, the P port 103 is connected to the oil tank through the booster pump, and the T port 104 is connected to the oil tank. In this embodiment, the reversing valve 10 is of internal control type and does not require external control during operation. When the pressure of the hydraulic oil at the P port 103 is greater than the elastic force of the elastic member 4, the hydraulic oil drives the valve core assembly 2 to move to the oil inlet position. At this time, the P port 103 and the A port 101 are connected, the oil inlet path is a passage, the T port 104 and the B port 102 are blocked by the valve core assembly 2, the oil return path is an open circuit, and the hydraulic oil in the oil tank moves to the single-acting cylinder through the oil inlet path to drive the single-acting cylinder to work; when the pressure of the hydraulic oil at the P port 103 is less than the elastic force of the elastic member 4, the elastic member 4 drives the valve core assembly 2 to move to the oil return position. At this time, the P port 103 and the A port 101 are blocked by the valve core assembly 2, the oil inlet path is an open circuit, the T port 104 and the B port 102 are connected, the oil return path is a passage, and the hydraulic oil in the single-acting cylinder moves to the oil tank through the oil return path to complete the cycle.

[0041] Furthermore, the valve core assembly 2 includes a circulating valve core 21 and a working valve core 22. The circulating valve core 21 is provided with a first delivery hole 212. The first end of the first delivery hole 212 is connected to the T port 104. When the return oil circuit is open (that is, when the valve core assembly 2 is located at the return oil position), the second end of the first delivery hole 212 is connected to the B port 102 to realize the passage of the return oil circuit; the working valve core 22 is provided with a second delivery hole 221. The first end of the second delivery hole 221 is connected to the P port 103. When the oil inlet circuit is open (that is, when the valve core assembly 2 is located at the oil inlet position), the second end of the second delivery hole 221 is connected to the A port 101 to realize the passage of the oil inlet circuit.

[0042] In this embodiment, the outer diameter of the circulating valve core 21 is smaller than the outer diameter of the working valve core 22. The circulating valve core 21 is connected to the working valve core 22. The elastic member 4 is a spring. The spring is sleeved on the circulating valve core 21, and one end of the spring abuts against the side wall of the installation cavity 11, and the other end abuts against the end surface of the working valve core 22 close to one end of the circulating valve core 21 (the abutting portion is the portion of the end surface of the working valve core 22 connected to the circulating valve core 21 that is exposed to the circulating valve core 21).

[0043] In order to reduce the processing difficulty of the coaxiality between the working valve core 22 and the circulation valve core 21, the circulation valve core 21 and the working valve core 22 are split structures, which are fixedly connected to form a whole. Specifically, the valve core assembly 2 also includes a positioning pin 223 and a first retaining spring 224, the working valve core 22 is provided with a positioning hole 222, the side wall of the positioning hole 222 is provided with a first pin hole, the circulation valve core 21 is provided with a positioning shaft 211, the side wall of the positioning shaft 211 is provided with a second pin hole, the positioning shaft 211 extends into the positioning hole 222, the positioning pin 223 is penetrated by the first pin hole and the second pin hole, and the positioning pin 223 is fixed in the first pin hole by the first retaining spring 224, so that the circulation valve core 21 is connected to the working valve core 22, and the processing difficulty of the secondary concentricity of the working valve core 22 and the circulation valve core 21 is reduced by the matching clearance of the positioning pin 223. Of course, in other embodiments, the connection method of the circulation valve core 21 and the working valve core 22 can also be threaded connection, clamping or other methods. Furthermore, the circulation valve core 21 and the working valve core 22 can also be made into an integrated type. The circulation valve core 21 and the working valve core 22 are integrally formed, and their coaxiality is ensured by machining accuracy.

[0044] Preferably, a second retaining spring 3 is installed in the installation cavity 11. When the valve core assembly 2 is located at the oil return position, the end of the working valve core 22 away from the circulation valve core 21 abuts against the second retaining spring 3. When the valve core assembly 2 moves to the oil return position driven by the elastic member 4, the second retaining spring 3 limits the valve core assembly 2.

[0045] Preferably, the circulation valve core 21 is stepped, the housing 1 is provided with a first guide hole 12, the first guide hole 12 is connected to the installation cavity 11, the stepped small diameter section 214 slides into the first guide hole 12, the first guide hole 12 guides the movement of the circulation valve core 21, when the valve core assembly 2 is located at the oil inlet position, the end face of the large diameter section 213 of the circulation valve core 21 abuts against the side wall of the installation cavity 11 near one end of the first guide hole 12, and the end face of the installation cavity 11 acts as a limiter when the valve core assembly 2 moves to the oil inlet position. The first delivery hole 212 is located in the circulation valve core 21, one end of the first guide hole 12 is connected to the T port 104, and the other end is connected to the first delivery hole 212.

[0046] Further preferably, the small diameter section 214 and the large diameter section 213 are connected by a conical surface 215, and the first guide hole 12 is provided with a chamfer 13 at one end close to the installation cavity 11, and the chamfer 13 can fit the conical surface 215. When the valve core assembly 2 is located at the oil return position, the conical surface 215 fits with the chamfer 13 to achieve the sealing between the circulation valve core 21 and the first guide hole 12, so as to completely block the T port 104. In other embodiments, the first guide hole 12 is provided with a rounded corner at one end close to the installation cavity 11. The rounded corner is in linear sealing contact with the conical surface 215.

[0047] It should be noted that, when the valve core assembly 2 is located at the oil inlet position, one end of the first delivery hole 212 is connected to the T port 104, and the other end is blocked by the side wall of the first guide hole 12, and one end of the second delivery hole 221 is connected to the P port 103, and the other end is connected to the A port 101; when the valve core assembly 2 is located at the oil return position, one end of the first delivery hole 212 is connected to the T port 104, and the other end is connected to the B port 102, and one end of the second delivery hole 221 is connected to the P port 103, and the other end is blocked by the side wall of the installation cavity 11.

[0048] like Figure 2As shown, the present embodiment further provides a braking system, comprising a single-acting oil cylinder 20, a braking source 30, an oil return collection device 40 and the above-mentioned reversing valve 10, wherein the outlet of the oil inlet circuit and the inlet of the oil return circuit of the reversing valve 10 are respectively connected to the rodless chamber of the single-acting oil cylinder 20 (i.e., the A port 101 and the B port 102 of the reversing valve 10 are respectively connected to the rodless chamber of the single-acting oil cylinder), the inlet of the oil inlet circuit is connected to the braking source 30, and the outlet of the oil return circuit is connected to the oil return collection device 40. In the present embodiment, the braking source 30 is a booster pump and an oil tank, the P port 103 of the reversing valve 10 is connected to the oil tank through the booster pump, the oil return collection device 40 is an oil tank or an oil pot, and the T port 104 of the reversing valve is connected to the oil return collection device 40, so that the oil inlet and the oil return in the braking system are different, thereby achieving the effect of replenishing and cooling the new oil in the pipeline and the oil cylinder, and improving the reliability of the braking system. The reversing valve 10 in this embodiment can be applied to the circulation and cooling of brake oil in the pneumatic brake and full hydraulic brake systems of engineering machinery, and the circulation of brake oil inside components such as hydraulic motors or gearboxes with internal brake structures.

[0049] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A reversing valve, characterized in that: include: A housing (1), wherein the housing (1) is provided with a mounting cavity (11), an oil inlet passage and an oil return passage; A valve core assembly (2) is slidably arranged in the installation cavity (11); the position of the valve core assembly (2) includes an oil inlet position and an oil return position; when the valve core assembly (2) is located at the oil inlet position, the oil inlet path is a passage and the oil return path is a disconnected path; when the valve core assembly (2) is located at the oil return position, the oil inlet path is a disconnected path and the oil return path is a passage; When the valve core assembly (2) moves from the oil return position to the oil inlet position, the circuit breaking stroke of the oil return circuit is X1, and the passage stroke of the oil inlet circuit is X2, wherein X1 is smaller than X2.

2. The reversing valve according to claim 1, characterized in that: The reversing valve is a two-position four-way reversing valve, and is provided with an A port (101), a B port (102), a P port (103) and a T port (104). The A port (101) and the P port (103) form the oil inlet path, and the B port (102) and the T port (104) form the oil return path. The reversing valve comprises an elastic member (4), and the elastic member (4) is used to drive the valve core assembly (2) to move to the oil return position; when the pressure of the hydraulic oil at the P port (103) is greater than the elastic force of the elastic member (4), the hydraulic oil drives the valve core assembly (2) to move to the oil inlet position.

3. The reversing valve according to claim 2, characterized in that: The valve core assembly (2) comprises a circulation valve core (21) and a working valve core (22); the circulation valve core (21) is provided with a first delivery hole (212); a first end of the first delivery hole (212) is connected to the T port (104); when the oil return passage is open, a second end of the first delivery hole (212) is connected to the B port (102); The working valve core (22) is provided with a second delivery hole (221), a first end of the second delivery hole (221) is connected to the P port (103), and when the oil inlet passage is open, a second end of the second delivery hole (221) is connected to the A port (101).

4. The reversing valve according to claim 3, characterized in that: The outer diameter of the circulating valve core (21) is smaller than the outer diameter of the working valve core (22); the circulating valve core (21) is connected to the working valve core (22); the elastic member (4) is a spring, which is sleeved on the circulating valve core (21), and one end of the spring abuts against the side wall of the installation cavity (11), and the other end abuts against the end surface of the working valve core (22) close to one end of the circulating valve core (21).

5. According to the reversing valve of claim 3, the circulating valve core (21) and the working valve core (22) are of split structure and are fixedly connected to form a whole.

6. The reversing valve according to claim 5, characterized in that: The valve core assembly (2) further comprises a positioning pin (223) and a first retaining spring (224); the working valve core (22) is provided with a positioning hole (222); a first pin hole is provided on a side wall of the positioning hole (222); the circulating valve core (21) is provided with a positioning shaft (211); a second pin hole is provided on a side wall of the positioning shaft (211); the positioning shaft (211) extends into the positioning hole (222); the positioning pin (223) is passed through the first pin hole and the second pin hole, and the positioning pin (223) is fixed in the first pin hole by a first retaining spring (224).

7. The reversing valve according to claim 3, characterized in that: The circulation valve core (21) and the working valve core (22) are integrally formed.

8. The reversing valve according to claim 3, characterized in that: A second retaining spring (3) is installed in the installation cavity (11); when the valve core assembly (2) is located at the oil return position, one end of the working valve core (22) away from the circulation valve core (21) abuts against the second retaining spring (3).

9. The reversing valve according to claim 3, characterized in that: The circulation valve core (21) is stepped, the housing (1) is provided with a first guide hole (12), the first guide hole (12) is connected to the installation cavity (11), the stepped small diameter section (214) slides into the first guide hole (12), and when the valve core assembly (2) is located at the oil inlet position, the end surface of the large diameter section (213) of the circulation valve core (21) abuts against the side wall of the installation cavity (11) close to one end of the first guide hole (12).

10. The reversing valve according to claim 9, characterized in that: The small diameter section (214) and the large diameter section (213) are connected via a tapered surface (215); a chamfer (13) is provided at one end of the first guide hole (12) close to the installation cavity (11); the chamfer (13) can fit the tapered surface (215); or a rounded corner is provided at one end of the first guide hole (12) close to the installation cavity (11).

11. A braking system, characterized in that: It comprises a single-acting cylinder (20), a braking source (30), an oil return collecting device (40) and a reversing valve as claimed in any one of claims 1 to 10, wherein the outlet of the oil inlet circuit and the inlet of the oil return circuit of the reversing valve are respectively connected to the rodless chamber of the single-acting cylinder (20), the inlet of the oil inlet circuit is connected to the braking source (30), and the outlet of the oil return circuit is connected to the oil return collecting device (40).

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