Variable pump system pressure control method, control device, and variable pump system

Abstract

The application discloses a variable pump system pressure control method, a control device and a variable pump system, and belongs to the technical field of hydraulic systems. The variable pump system pressure control method, the control device and the variable pump system have the following advantages. When the output pressure of the variable pump body is not less than the preset pressure, the time length that the variable pump body is in the state of the output pressure being not less than the preset pressure is taken as a reference condition, the overflow pressure of the first overflow valve is controlled, and the maximum output pressure of the variable pump body is controlled. When the overflow pressure of the first overflow valve is the initial overflow pressure, the maximum output pressure of the variable pump body can reach the rated pressure, and the variable pump system can fully exert its performance. When the overflow pressure of the first overflow valve is the preset overflow pressure, the maximum output pressure of the variable pump body cannot reach the rated pressure, the maximum output pressure of the variable pump body is limited, and the variable pump body is protected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic systems, and particularly relates to a variable pump system pressure control method, a control device and a variable pump system. BACKGROUND

[0002] The existing plunger pump usually only guarantees that the output pressure thereof does not exceed the rated pressure. When the plunger pump works in a harsh working condition, the output pressure thereof fluctuates around the rated pressure for a long time, and the problems of serious heating and reduced service life are prone to occur.

[0003] In order to solve the above problems, in the prior art, a pressure cut-off valve is added in the plunger pump, so that when the output pressure of the plunger pump reaches the pressure cut-off set value (which is lower than the rated pressure of the plunger pump), the pressure no longer increases, and thus the maximum output pressure of the plunger pump is limited to a certain value below the rated pressure, thereby protecting the plunger pump. However, in a conventional working condition, the maximum output pressure of the plunger pump is limited, and the rated pressure cannot be reached, so that the plunger pump cannot exert its maximum capacity, resulting in that the existing plunger pump cannot adapt to various complex working conditions well, and performance is wasted. SUMMARY

[0004] The present application aims to provide a variable pump system pressure control method, a control device and a variable pump system, which can not only make the variable pump body fully exert its performance, but also protect the variable pump body.

[0005] To achieve the above-mentioned purpose, the following technical solutions are provided:

[0006] In a first aspect, a variable pump system pressure control method is provided. The variable pump system comprises a variable pump body, a pump control unit and a pressure regulating unit. The pump control unit is used to control the swing angle of a swash plate of the variable pump body to control the output displacement of the variable pump body. The pressure regulating unit comprises a first overflow valve and a second overflow valve. The inlet of the first overflow valve is in communication with the outlet of the variable pump body. The outlet of the first overflow valve is in communication with the inlet of the second overflow valve and the pump control unit respectively. The outlet of the second overflow valve is in communication with an oil tank.

[0007] The variable pump system pressure control method comprises the following steps:

[0008] The output pressure of the variable pump body is obtained and timing is performed.

[0009] The output pressure is compared with a preset pressure.

[0010] If the output pressure is not less than the preset pressure, the time length during which the variable pump body is in the state that the output pressure is not less than the preset pressure is compared with a first preset time length.

[0011] According to the comparison result, the relief pressure of the first relief valve is determined, and the first relief valve is controlled to adjust to the determined relief pressure; the relief pressure of the first relief valve includes an initial relief pressure and a preset relief pressure, the initial relief pressure is greater than the rated pressure of the variable pump body; and the preset relief pressure is less than the rated pressure of the variable pump body.

[0012] As an alternative to the variable pump system pressure control method, according to the comparison result, the relief pressure of the first relief valve is determined, and the first relief valve is controlled to adjust to the determined relief pressure, including the following steps:

[0013] If the variable pump body is in a state where the output pressure is not less than the preset pressure for a time period less than the first preset time period, the relief pressure of the first relief valve is the initial relief pressure.

[0014] As an alternative to the variable pump system pressure control method, according to the comparison result, the relief pressure of the first relief valve is determined, and the first relief valve is controlled to adjust to the determined relief pressure, including the following steps:

[0015] If the variable pump body is in a state where the output pressure is not less than the preset pressure for a time period not less than the first preset time period, the relief pressure of the first relief valve is the preset relief pressure.

[0016] As an alternative to the variable pump system pressure control method, after the relief pressure of the first relief valve is set to the preset relief pressure, the following steps are further included:

[0017] If the output pressure decreases to be less than the preset pressure, the time period that the variable pump body is in a state where the output pressure is less than the preset pressure is compared with a second preset time period;

[0018] According to the comparison result again, the relief pressure of the first relief valve is determined, and the first relief valve is controlled to adjust to the determined relief pressure.

[0019] As an alternative to the variable pump system pressure control method, according to the comparison result again, the relief pressure of the first relief valve is determined, and the first relief valve is controlled to adjust to the determined relief pressure, including the following steps:

[0020] If the variable pump body is in a state where the output pressure is less than the preset pressure for a time period less than the second preset time period, the relief pressure of the first relief valve continues to be maintained at the preset relief pressure.

[0021] As an alternative to the variable pump system pressure control method, the relief pressure of the first relief valve is determined again according to the comparison result, and the first relief valve is controlled to adjust to the determined relief pressure, comprising the following steps:

[0022] If the variable pump body is in the state that the output pressure is less than the preset pressure for a time length not less than the second preset time length, the relief pressure of the first relief valve is restored to the initial relief pressure.

[0023] As an alternative to the variable pump system pressure control method, after comparing the output pressure with the preset pressure, the following steps are further included:

[0024] If the output pressure is less than the preset pressure, the relief pressure of the first relief valve is the initial relief pressure.

[0025] In a second aspect, a variable pump system pressure control device is provided, the variable pump system comprising a variable pump body, a pump control unit and a pressure regulating unit, the pump control unit being used to control the swing angle of the swash plate of the variable pump body to control the output displacement of the variable pump body; the pressure regulating unit comprising a first relief valve and a second relief valve, the inlet of the first relief valve being communicated with the outlet of the variable pump body, the outlet of the first relief valve being communicated with the inlet of the second relief valve and the pump control unit respectively, and the outlet of the second relief valve being communicated with an oil tank;

[0026] The variable pump system pressure control device comprises:

[0027] A data acquisition module is used to acquire the output pressure of the variable pump system and perform timing;

[0028] A first data processing module is used to compare the output pressure with a preset pressure;

[0029] A second data processing module is used to compare the time length that the variable pump body is in the state that the output pressure is not less than the preset pressure with a first preset time length when the output pressure is not less than the preset pressure;

[0030] A control module is used to determine the relief pressure of the first relief valve according to the comparison result, and control the first relief valve to adjust to the determined relief pressure; the relief pressure of the first relief valve comprises an initial relief pressure and a preset relief pressure, the initial relief pressure being greater than the rated pressure of the variable pump system; and the preset relief pressure being less than the rated pressure of the variable pump system.

[0031] In a third aspect, a variable pump system is provided, comprising:

[0032] A variable pump body and a pump control unit for controlling a swing angle of a swash plate of the variable pump body to control an output displacement of the variable pump body;

[0033] A pressure regulating unit including a first relief valve and a second relief valve, an inlet of the first relief valve being communicated with an outlet of the variable pump body, outlets of the first relief valve being respectively communicated with the pump control unit and an inlet of the second relief valve, an outlet of the second relief valve being communicated with an oil tank;

[0034] A pressure detecting member for detecting an output pressure of the variable pump body;

[0035] A system control assembly being communicatively connected with the pressure detecting member, the pump control unit and the first relief valve, and being further configured to perform the variable pump system pressure control method according to any one of claims 1-7.

[0036] As an alternative to the variable pump system, the variable pump system further includes an oil supplement unit for providing pilot oil to the pump control unit, and an outlet of the second relief valve being communicated with an output end of the oil supplement unit.

[0037] In a third aspect, there is provided

[0038] Compared with the prior art, the variable pump system pressure control method, the control device and the variable pump system have the following beneficial effects:

[0039] The variable pump system pressure control method, the control device and the variable pump system of the present application, when the output pressure of the variable pump body is not less than the preset pressure, it indicates that the variable pump body is in a harsh working condition, at this time, the time length of the variable pump body in the state that the output pressure is not less than the preset pressure is taken as a reference condition, the relief pressure of the first relief valve is controlled, and the maximum output pressure of the variable pump body is controlled. When the relief pressure of the first relief valve is the initial relief pressure, the maximum output pressure of the variable pump body can reach the rated pressure, thereby enabling the variable pump system to fully exert its performance; when the relief pressure of the first relief valve is the preset relief pressure, the maximum output pressure of the variable pump body cannot reach the rated pressure, so as to limit the maximum output pressure of the variable pump body, thereby protecting the variable pump body. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a structural principle diagram of the variable pump system in the embodiment of the present application;

[0041] Figure 2 It is a flowchart of the variable pump system pressure control method in the embodiment of the present application.

[0042] REFERENCE NUMERALS:

[0043] 1, variable pump body; 2, pump control unit; 21, pilot valve; 22, pilot control valve; 3, pressure regulating unit; 31, first overflow valve; 32, second overflow valve; 4, oil supplement unit; 41, hydraulic pump; 42, third overflow valve; 51, pressure control valve; 6, pressure detecting member. DETAILED DESCRIPTION

[0044] To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0046] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0047] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance. In the description of the present application, unless otherwise specified, the meaning of "multiple" is two or more.

[0048] In the description of the present application, it should also be noted that, unless otherwise specified and limited, the terms "set", "connected" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0051] Example 1

[0052] like Figures 1-2 As shown, this embodiment provides a variable pump system and a variable pump system pressure control method. The variable pump system adopts the variable pump system pressure control method to not only enable the variable pump body 1 to fully perform its function, but also to protect the variable pump body 1.

[0053] like Figure 1 As shown, in this embodiment, the variable pump system includes a variable pump body 1, a pump control unit 2, a pressure regulating unit 3, and a replenishing unit 4. The pump control unit 2 is used to control the swashplate angle of the variable pump body 1 to control the output displacement of the variable pump body 1. The replenishing unit 4 is used to provide pilot oil to the pump control unit 2. The pressure regulating unit 3 includes a first overflow valve 31 and a second overflow valve 32. The inlet of the first overflow valve 31 is connected to the outlet of the variable pump body 1, and the outlet of the first overflow valve 31 is connected to the pump control unit 2 and the inlet of the second overflow valve 32, respectively. The outlet of the second overflow valve 32 is connected to the oil tank and the output end of the replenishing unit 4, respectively.

[0054] Optionally, the pump control unit 2 includes a pilot valve 21 and two pilot control valves 22. The pilot chambers at both ends of the pilot valve 21 are respectively connected to the oil replenishment unit 4 through one pilot control valve 22, so as to control the oil supply from the oil replenishment unit 4 to the pilot chambers at both ends of the pilot valve 21 through the two pilot control valves 22. Specifically, the outlet of the first relief valve 31 is connected to one of the pilot chambers of the pilot valve 21. For example, the outlet of the first relief valve 31 can be connected to the pilot chamber at the left end of the pilot valve 21 or the pilot chamber at the right end of the pilot valve 21, which can be determined according to actual needs and is not limited here.

[0055] The spill pressure of the second spill valve 32 is not greater than the pressure at the outlet of the first spill valve 31, and since the outlet of the first spill valve 31 is communicated with the pilot chamber of the pilot valve 21, the pilot valve 21 can be protected by the second spill valve 32 to avoid the pressure in the pilot chamber of the pilot valve 21 exceeding the pressure threshold of the pilot valve 21.

[0056] Exemplarily, the pilot control valve 22 is a pilot type electric proportional pressure reducing valve.

[0057] Optionally, the oil supplement unit 4 comprises a hydraulic pump 41 capable of pumping hydraulic oil in the oil tank to the two pilot control valves 22.

[0058] Optionally, the oil supplement unit 4 further comprises a third spill valve 42, and the output end of the hydraulic pump 41 is communicated with the oil tank through the third spill valve 42. When the supplement amount of the oil supplement unit 4 is too large, the excessive hydraulic oil can be returned to the oil tank through the third spill valve 42.

[0059] In this embodiment, the outlet of the second spill valve 32 is communicated with the third spill valve 42, so that when the second spill valve 32 works, the hydraulic oil can be returned to the oil tank through the third spill valve 42.

[0060] Optionally, the variable pump body 1 comprises two pump outlets, the two pump outlets are respectively communicated with two pressure control valves 51, and the outlets of the two pressure control valves 51 are communicated with each other and then communicated with the oil tank. When the output pressure of the pump outlet is too large and the pressure regulating unit 3 cannot timely depressurize, at this time, the pressure control valves 51 can work simultaneously with the pressure regulating unit 3 to depressurize the system. Exemplarily, the pressure control valve 51 is a high-pressure spill valve integrated with the oil supplement function.

[0061] Further, the output end of the hydraulic pump 41 is also communicated with the outlets of the two pressure control valves 51, in other words, the outlets of the two pressure control valves 51 are also communicated with the inlet of the third spill valve 42, so that when any pressure control valve 51 works, the hydraulic oil can be returned to the oil tank through the third spill valve 42.

[0062] Further, the pressure detection member 6 and the system control assembly, the pressure detection member 6 is used for detecting the output pressure of the variable pump body 1; the system control assembly is in communication connection with the pressure detection member 6, the pump control unit 2 and the first spill valve 31 respectively; specifically, the hydraulic pump 41 and the two pilot control valves 22 are in communication connection with the system control assembly; the system control assembly is also used for executing the variable pump system pressure control method.

[0063] In this embodiment, the first spill valve 31 is an electric control pilot type spill valve, which is convenient for adjusting the spill pressure of the first spill valve 31; and the second spill valve 32 is a pilot type spill valve.

[0064] Figure 2 For the flow chart of the variable pump system pressure control method of the present embodiment, the following will be described in combination with Figure 2 The variable pump system pressure control method of the present embodiment will be described in detail.

[0065] The variable pump system pressure control method of the present embodiment comprises the following steps:

[0066] S1, obtaining the output pressure of the variable pump body 1 and timing;

[0067] In the present embodiment, the pressure at the output end of the variable pump body 1 is detected by the pressure detection member 6, and then the output pressure of the variable pump body 1 is obtained, which is simple and easy to operate. Exemplarily, the pressure detection member 6 is a pressure sensor.

[0068] S2, comparing the output pressure with the preset pressure;

[0069] It should be noted that the preset pressure can be determined according to experience or through multiple tests, and the present embodiment does not limit the value range of the preset pressure.

[0070] S3, if the output pressure is less than the preset pressure, the overflow pressure of the first overflow valve 31 is the initial overflow pressure;

[0071] The initial overflow pressure is the initial setting value of the overflow pressure of the first overflow valve 31, and the initial overflow pressure is greater than the rated pressure of the variable pump body 1. When the overflow pressure of the first overflow valve 31 is the initial overflow pressure, the maximum output pressure of the variable pump body 1 can reach the rated pressure within a certain time.

[0072] If the output pressure of the variable pump body 1 is less than the preset pressure, it indicates that the variable pump body 1 is in a normal working condition, and the output pressure of the variable pump body 1 will not fluctuate around the rated pressure for a long time. At this time, the overflow pressure of the first overflow valve 31 is the initial overflow pressure, so that the maximum output pressure of the variable pump body 1 can reach the rated pressure, and the variable pump body 1 can fully exert its performance.

[0073] S4, if the output pressure is not less than the preset pressure, comparing the time length of the state that the variable pump body 1 is in the output pressure not less than the preset pressure with the first preset time length;

[0074] It should be noted that the first preset time length can be determined according to experience or through multiple tests, and the present embodiment does not limit the value range of the first preset time length.

[0075] S5, according to the comparison result, determining the overflow pressure of the first overflow valve 31, and controlling the first overflow valve 31 to adjust to the determined overflow pressure.

[0076] It should be noted that, in addition to the initial relief pressure, the relief pressure of the first relief valve 31 also includes a preset relief pressure, which is less than the rated pressure of the variable pump body 1. When the relief pressure of the first relief valve 31 is the preset relief pressure, the maximum output pressure of the variable pump body 1 can only reach the preset relief pressure, and cannot reach the rated pressure.

[0077] If the output pressure of the variable pump body 1 reaches or exceeds the preset pressure, it indicates that the output pressure of the variable pump body 1 is large, in other words, the variable pump body 1 is in a harsh working condition, and the working burden of the variable pump body 1 is large. If the variable pump body 1 is in a harsh working condition for a long time, it is easy to cause serious heating and affect the service life, so the time length of the variable pump body 1 in the harsh working condition is taken as a reference condition to determine whether the relief pressure of the first relief valve 31 should be adjusted to the initial relief pressure or the preset relief pressure.

[0078] Specifically, in the embodiment, step S5 includes the following steps:

[0079] S51, if the time length of the variable pump body 1 in the state of the output pressure being not less than the preset pressure is less than the first preset time length, the relief pressure of the first relief valve 31 is the initial relief pressure.

[0080] The time length of the variable pump body 1 in the state of the output pressure being not less than the preset pressure is less than the first preset time length, in other words, the time length of the variable pump body 1 in the harsh working condition is short, which generally does not cause the problem of serious heating, at this time, the relief pressure of the first relief valve 31 can be the initial relief pressure, so that the maximum output pressure of the variable pump body 1 can reach the rated pressure, and the performance of the variable pump body 1 can be fully exerted.

[0081] S52, if the time length of the variable pump body 1 in the state of the output pressure being not less than the preset pressure is not less than the first preset time length, the relief pressure of the first relief valve 31 is the preset relief pressure.

[0082] The time length of the variable pump body 1 in the state of the output pressure being not less than the preset pressure is not less than the first preset time length, in other words, the time length of the variable pump body 1 in the harsh working condition is long, which is easy to cause the problem of serious heating and affect the service life, at this time, the relief pressure of the first relief valve 31 is the preset relief pressure, so as to limit the maximum output pressure of the variable pump body 1, and further make the maximum output pressure of the variable pump body 1 unable to reach the rated pressure, thereby protecting the variable pump body 1.

[0083] S53, after the relief pressure of the first relief valve 31 is the preset relief pressure, if the output pressure is reduced to be less than the preset pressure, the time length of the variable pump body 1 in the state of the output pressure being less than the preset pressure is compared with the second preset time length.

[0084] It should be noted that the second preset time length can be determined according to experience or through multiple tests, and the embodiment does not limit the value range of the second preset time length.

[0085] S54, according to the comparison result, the overflow pressure of the first overflow valve 31 is determined, and the first overflow valve 31 is controlled to adjust to the determined overflow pressure.

[0086] After the overflow pressure of the first overflow valve 31 is set to the preset overflow pressure, and the output pressure is reduced to the preset pressure, the time length when the variable pump body 1 is in the state that the output pressure is less than the preset pressure is taken as a reference condition to determine whether to adjust the overflow pressure of the first overflow valve 31 again, which can avoid frequent adjustment of the overflow pressure of the first overflow valve 31, and ensure the working stability of the variable pump system.

[0087] Step S54 includes the following steps:

[0088] S541, if the time length when the variable pump body 1 is in the state that the output pressure is less than the preset pressure is less than the second preset time length, the overflow pressure of the first overflow valve 31 continues to be kept as the preset overflow pressure;

[0089] S542, if the time length when the variable pump body 1 is in the state that the output pressure is less than the preset pressure is not less than the second preset time length, the overflow pressure of the first overflow valve 31 is restored to the initial overflow pressure.

[0090] If the time length when the variable pump body 1 is in the state that the output pressure is less than the preset pressure is less than the second preset time length, it indicates that the output pressure of the variable pump body 1 is only temporarily reduced, and the time length when the variable pump body 1 is in the harsh working condition is still relatively long, so the overflow pressure of the first overflow valve 31 continues to be kept as the preset overflow pressure to continue to protect the variable pump body 1. When the time length when the variable pump body 1 is in the state that the output pressure is less than the preset pressure reaches or exceeds the second preset time length, the overflow pressure of the first overflow valve 31 is restored to the initial overflow pressure to ensure the performance of the variable pump body 1 and avoid frequent adjustment of the overflow pressure of the first overflow valve 31.

[0091] It should be noted that the variable pump system pressure control method of the embodiment adjusts the maximum output pressure of the variable pump body 1 according to the actual working condition of the variable pump body 1, which can limit the maximum output pressure of the variable pump body 1 when the variable pump body 1 is in the harsh working condition, thereby protecting the variable pump body 1, and can release the limitation on the maximum output pressure of the variable pump body 1 when the variable pump body 1 is in the normal working condition, so that the variable pump body 1 can reach the rated pressure and fully exert its performance, thereby being adaptable to various working conditions and having stronger versatility.

[0092] Embodiment two

[0093] The embodiment also provides a variable pump system pressure control device for implementing the variable pump system pressure control method, and the variable pump system pressure control device comprises a data acquisition module, a first data processing module, a second data processing module and a control module. The data acquisition module is configured to acquire the output pressure of the variable pump system and perform timing. The first data processing module is configured to compare the output pressure with the preset pressure. The second data processing module is configured to compare the time length during which the variable pump body 1 is in the state of the output pressure being not less than the preset pressure with the first preset time length when the output pressure is not less than the preset pressure. The control module is configured to determine the overflow pressure of the first overflow valve 31 according to the comparison result, and control the first overflow valve 31 to be adjusted to the determined overflow pressure. The overflow pressure of the first overflow valve 31 comprises an initial overflow pressure and a preset overflow pressure. The initial overflow pressure is greater than the rated pressure of the variable pump system. The preset overflow pressure is less than the rated pressure of the variable pump system.

[0094] The variable pump system pressure control device of the embodiment can execute the variable pump system pressure control method, and has the same functions and advantages as the variable pump system pressure control method.

[0095] It should be noted that the above are only preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A variable pump system pressure control method, a variable pump system comprising a variable pump body (1), a pump control unit (2) and a pressure regulating unit (3), the pump control unit (2) being configured to control a swing angle of a swash plate of the variable pump body (1) to control an output displacement of the variable pump body (1); the pressure regulating unit (3) comprising a first overflow valve (31) and a second overflow valve (32), an inlet of the first overflow valve (31) being in communication with an outlet of the variable pump body (1), an outlet of the first overflow valve (31) being in communication with the pump control unit (2) and an inlet of the second overflow valve (32) respectively, an outlet of the second overflow valve (32) being in communication with an oil tank; the variable pump system pressure control method comprising the following steps: obtaining an output pressure of the variable pump body (1) and timing; comparing the output pressure with a preset pressure; if the output pressure is not less than the preset pressure, comparing a time length that the variable pump body (1) is in a state that the output pressure is not less than the preset pressure with a first preset time length; determining an overflow pressure of the first overflow valve (31) according to the comparison result, and controlling the first overflow valve (31) to adjust to the determined overflow pressure; the overflow pressure of the first overflow valve (31) comprising an initial overflow pressure and a preset overflow pressure, the initial overflow pressure being greater than a rated pressure of the variable pump body (1); the preset overflow pressure being less than the rated pressure of the variable pump body (1); determining the overflow pressure of the first overflow valve (31) according to the comparison result, and controlling the first overflow valve (31) to adjust to the determined overflow pressure, comprising the following steps: if the time length that the variable pump body (1) is in the state that the output pressure is not less than the preset pressure is less than the first preset time length, making the overflow pressure of the first overflow valve (31) be the initial overflow pressure; determining the overflow pressure of the first overflow valve (31) according to the comparison result, and controlling the first overflow valve (31) to adjust to the determined overflow pressure, comprising the following steps: if the time length that the variable pump body (1) is in the state that the output pressure is not less than the preset pressure is not less than the first preset time length, making the overflow pressure of the first overflow valve (31) be the preset overflow pressure; after making the overflow pressure of the first overflow valve (31) be the preset overflow pressure, further comprising the following steps: if the output pressure is reduced to be less than the preset pressure, comparing a time length that the variable pump body (1) is in a state that the output pressure is less than the preset pressure with a second preset time length; again determining the overflow pressure of the first overflow valve (31) according to the comparison result, and controlling the first overflow valve (31) to adjust to the determined overflow pressure; again determining the overflow pressure of the first overflow valve (31) according to the comparison result, and controlling the first overflow valve (31) to adjust to the determined overflow pressure, comprising the following steps: if the time length that the variable pump body (1) is in the state that the output pressure is less than the preset pressure is less than the second preset time length, making the overflow pressure of the first overflow valve (31) be the initial overflow pressure; if the time length that the variable pump body (1) is in the state that the output pressure is less than the preset pressure is not less than the second preset time length, making the overflow pressure of the first overflow valve (31) be the preset overflow pressure. characterized in that ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ If the variable pump body (1) is in the state that the output pressure is less than the preset pressure for a time less than the second preset time, the overflow pressure of the first overflow valve (31) is kept as the preset overflow pressure; According to the comparison result, the overflow pressure of the first overflow valve (31) is determined, and the first overflow valve (31) is controlled to adjust to the determined overflow pressure, including the following steps: If the variable pump body (1) is in the state that the output pressure is less than the preset pressure for a time not less than the second preset time, the overflow pressure of the first overflow valve (31) is restored to the initial overflow pressure.

2. The variable pump system pressure control method of claim 1, wherein, After comparing the size of the output pressure and the preset pressure, the following steps are further included: If the output pressure is less than the preset pressure, the overflow pressure of the first overflow valve (31) is the initial overflow pressure.

3. A variable pump system pressure control device for implementing the variable pump system pressure control method according to any one of claims 1-2, the variable pump system comprising a variable pump body (1), a pump control unit (2) and a pressure regulating unit (3), the pump control unit (2) being configured to control the swing angle of the swash plate of the variable pump body (1) to control the output displacement of the variable pump body (1); the pressure regulating unit (3) comprising a first overflow valve (31) and a second overflow valve (32), the inlet of the first overflow valve (31) being communicated with the outlet of the variable pump body (1), the outlet of the first overflow valve (31) being communicated with the inlet of the second overflow valve (32) and the pump control unit (2) respectively, and the outlet of the second overflow valve (32) being communicated with an oil tank; characterized in that The variable pump system pressure control device comprises: a data acquisition module configured to acquire the output pressure of the variable pump system and perform timing; a first data processing module configured to compare the size of the output pressure and a preset pressure; a second data processing module configured to compare the time that the variable pump body (1) is in the state that the output pressure is not less than the preset pressure with a first preset time when the output pressure is not less than the preset pressure; a control module configured to determine the overflow pressure of the first overflow valve (31) according to the comparison result, and control the first overflow valve (31) to adjust to the determined overflow pressure; the overflow pressure of the first overflow valve (31) comprising an initial overflow pressure and a preset overflow pressure, the initial overflow pressure being greater than the rated pressure of the variable pump system, and the preset overflow pressure being less than the rated pressure of the variable pump system.

4. A variable pump system characterized by, comprise: a variable pump body (1) and a pump control unit (2), the pump control unit (2) being configured to control the swing angle of the swash plate of the variable pump body (1) to control the output displacement of the variable pump body (1); a pressure regulating unit (3) comprising a first overflow valve (31) and a second overflow valve (32), an inlet of the first overflow valve (31) being communicated with an outlet of the variable pump body (1), an outlet of the first overflow valve (31) being communicated with the pump control unit (2) and an inlet of the second overflow valve (32) respectively, an outlet of the second overflow valve (32) being communicated with an oil tank; a pressure detecting member (6) for detecting an output pressure of the variable pump body (1); a system control assembly being communicatively connected with the pressure detecting member (6), the pump control unit (2) and the first overflow valve (31) respectively, the system control assembly being further configured to perform the variable pump system pressure control method according to any one of claims 1-2.

5. The variable pump system of claim 4, wherein, The variable pump system further comprises an oil supplement unit (4) for providing pilot oil to the pump control unit (2), an outlet of the second overflow valve (32) being communicated with an output end of the oil supplement unit (4).

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