CN217783888U - Load sensitive valve, variable displacement hydraulic pump and hydraulic system - Google Patents

Abstract

The present disclosure provides a load sensitive valve including a main body portion and a spool, a variable displacement hydraulic pump, and a hydraulic system. The main body part comprises a first cavity chamber, a valve cavity and a second cavity chamber which are connected in sequence. The valve spool is located in the valve chamber and includes a first end facing the first chamber and a second end facing the second chamber, the first end including a first surface for withstanding the pressure of the first chamber and the second end including a second surface for withstanding the pressure of the second chamber. In the axial extension direction of the valve chamber, the pressure-bearing area of the first surface is smaller than the pressure-bearing area of the second surface. By the load sensitive valve, the output flow of the hydraulic system can be ensured to be increased along with the increase of the load pressure, so that the normal work of the actuating mechanism is ensured.

Description

Load sensitive valve, variable displacement hydraulic pump and hydraulic system

Technical Field

The utility model relates to a hydraulic pressure field, concretely relates to sensitive valve of load, variable displacement hydraulic pump and hydraulic system.

Background

The hydraulic system is based on hydraulic pressure and flow to effect energy transfer to drive the implement. Hydraulic systems do not normally operate at a constant pressure, for example when the external load varies, the operating pressure of the hydraulic system also needs to be adjusted, in the process of which the hydraulic and flow demands need to be adjusted, in which case a load sensitive valve is usually provided to detect the pressure of the hydraulic system and to adjust the flow demand. However, when maintaining the hydraulic system flow constant, if the load pressure rises, the actuator may instead experience a deceleration.

Disclosure of Invention

The utility model provides a sensitive valve of load, variable displacement hydraulic pump and hydraulic system, through designing the structure of the sensitive valve of load for the bearing area of its case both sides is inequality, so that the pressure differential before and after the main valve of hydraulic system is in direct proportion relation with the flow of main pump, increases along with load pressure in order to guarantee hydraulic system's output flow, guarantees that actuating mechanism normally works.

A first aspect of the present disclosure provides a load sensitive valve for a variable displacement hydraulic pump, the load sensitive valve comprising a main body portion and a spool. The main body part comprises a first cavity, a valve cavity and a second cavity which are connected in sequence. The valve spool is located in the valve cavity and includes a first end facing the first chamber and a second end facing the second chamber, the first end including a first surface for receiving the pressure of the first chamber, and the second end including a second surface for receiving the pressure of the second chamber. The bearing area of the first surface is smaller than the bearing area of the second surface in the axial extension direction of the valve chamber.

In one embodiment of the first aspect of the present disclosure, the pressure-bearing area of the second surface is 1.01 to 1.1 times the pressure-bearing area of the first surface.

In a particular embodiment of the first aspect of the present disclosure, the valve cavity comprises a first cavity section for receiving the first end portion and a second cavity section for receiving the second end portion. On a plane perpendicular to the axial extension direction of the valve chamber, the cross-sectional dimension of the first chamber section is smaller than the cross-sectional dimension of the second chamber section.

In a particular embodiment of the first aspect of the present disclosure, the first cavity section and the first end section have a cross-sectional dimension substantially equal in a plane perpendicular to the axial extension direction of the valve cavity, the surface of the first end section facing the first chamber being a first surface; and/or the cross-sectional dimension of the second cavity segment and the cross-sectional dimension of the second end portion are substantially equal, and the surface of the second end portion facing the second cavity is a second surface.

In one embodiment of the first aspect of the present disclosure, the load sensitive valve may further include a resilient structure located in the second chamber and having one end supported on the body portion and another end supporting the second end of the spool.

In a particular embodiment of the first aspect of the present disclosure, the valve cartridge may further include a connection portion through which the first end portion and the second end portion are connected. The valve cavity comprises a third cavity section for accommodating the connecting part. The main body part further comprises a first flow passage and a second flow passage, the first flow passage and the second flow passage are communicated to the third cavity section, and the first flow passage is located between the first cavity and the second flow passage. In a first state that the valve core is stressed in a balanced manner, the valve core is located at a preset position so that the first flow passage and the second flow passage are closed; or in a second state that the stress of the first end part of the valve core is larger than that of the second end part, the valve core moves towards the second cavity relative to the preset position, so that the first flow passage is communicated with the first cavity; or in a third state that the stress of the first end part of the valve core is smaller than that of the second end part, the valve core moves towards the first cavity relative to the preset position, so that the first flow passage is communicated with the second flow passage.

In a specific embodiment of the first aspect of the present disclosure, the main body further includes a third flow passage communicating with the first chamber, the third flow passage communicates with the third chamber section, and the third flow passage is located between the first chamber and the first flow passage, and in the second state, the first flow passage and the third flow passage communicate.

In the above scheme, in the second state, the fluid in the first chamber does not flow into the first flow channel, so that the fluid with the pressure of the first chamber can be ensured to enter the first flow channel, and meanwhile, the first chamber can be prevented from generating large pressure fluctuation, and the precision of the load sensitive valve is ensured.

In another embodiment of the first aspect of the present disclosure, the main body part is not provided with the third flow passage, and in the second state, the first chamber may communicate with the first flow passage.

In the scheme, the structural design of the load sensitive valve can be simplified, and the processing difficulty is reduced.

A second aspect of the present disclosure provides a variable displacement hydraulic pump comprising a main pump, a servo mechanism and the load sensitive valve of the first aspect described above. The main pump includes a swash plate, a cylinder block, and an axial plunger. The first chamber of the load sensitive valve is communicated to the output end of the main pump. The servo mechanism is connected to the swash plate and is connected with the load sensitive valve through a hydraulic oil path to control the displacement of the main pump.

In a second aspect of the present disclosure, there is provided a variable displacement hydraulic pump in which the spool further includes a connection portion through which the first end portion of the spool and the second end portion of the spool are connected. The valve cavity comprises a cavity section for accommodating the connection portion. The main body part further comprises a first flow passage and a second flow passage, one end of the first flow passage is communicated with the cavity section, the other end of the first flow passage is communicated with the servo mechanism, one end of the second flow passage is communicated with the cavity section, the other end of the second flow passage is used for discharging, and the first flow passage is located between the first cavity and the second flow passage. In a first state that the valve core is stressed in a balanced manner, the valve core is located at a preset position so that the first flow passage and the second flow passage are closed; or in a second state that the stress of the first end part of the valve core is larger than that of the second end part, the valve core moves towards the second cavity relative to the preset position, so that the first flow passage is communicated with the first cavity; or in a third state that the stress of the first end part of the valve core is smaller than that of the second end part, the valve core moves towards the first cavity relative to the preset position, so that the first flow passage is communicated with the second flow passage.

In one embodiment of the second aspect of the present disclosure, the body portion further includes a third flow passage in communication with the first chamber, the third flow passage communicates to the third cavity section, and the third flow passage is located between the first chamber and the first flow passage. In the second state, the first flow passage and the third flow passage are communicated.

A third aspect of the present disclosure provides a hydraulic system including the variable displacement hydraulic pump of the second aspect described above, a control valve, and an actuator driven by the variable displacement hydraulic pump. The control valve is disposed between the variable displacement hydraulic pump and the actuator and controls a pressure supplied to the actuator, and includes a control main valve and a pressure compensator disposed between the control main valve and the actuator. The second chamber of the load sensitive valve is connected between the actuator and the pressure compensator.

Drawings

Fig. 1 is a schematic structural diagram of a hydraulic system according to an embodiment of the present disclosure;

FIG. 2A is a schematic illustration of a load sensitive valve of the hydraulic system of FIG. 1 in a first state;

FIG. 2B is a cross-sectional view of an embodiment of the load sensitive valve of FIG. 2A;

FIG. 3A is a schematic diagram of a portion of the components of the load sensitive valve shown in FIG. 2A;

FIG. 3B is a fragmentary cross-sectional view of a portion of the components of the load sensitive valve shown in FIG. 3A;

FIG. 4A is a schematic diagram of a portion of the components of the load sensitive valve shown in FIG. 2A;

FIG. 4B is a fragmentary cross-sectional view of a portion of the components of the load sensitive valve shown in FIG. 4A;

FIG. 5 is a schematic diagram of the load sensitive valve of FIG. 2A in a second state;

fig. 6 is a schematic diagram of the load sensitive valve shown in fig. 2A in a third state.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

In at least one embodiment of the present disclosure, as shown in fig. 1, a hydraulic system may include a main pump 10, a servo 20, an actuator 30, a load sensitive valve 40, a control main valve 50, and a pressure compensator 60. The main pump 10 includes a swash plate, a cylinder block, and an axial plunger, and the servo mechanism 20 is connected to the swash plate of the main pump 10 to control the displacement of the main pump 10. The load-sensitive valve 40 communicates between the output of the main pump 10 (at the location of node N1 in fig. 1) and the working pressure downstream of the hydraulic system (where the load pressure is fed back, for example at node N2 between the actuator 30 and the pressure compensator 60 in fig. 1) and is connected to the servo mechanism via a hydraulic circuit to control the servo mechanism 20. In this manner, the load sensitive valve 40 controls the output flow of the hydraulic system by sensing the pressures at the nodes N1, N2 (which may indicate corresponding pressures) and feeding them back to the servo 20 to control the displacement of the main pump 10 by the servo 20.

It should be noted that, in practical applications, the main pump 10, the servo mechanism 20 and the load sensitive valve 40 will be integrated together and referred to as a variable displacement hydraulic pump; the control main valve 50 and the pressure compensator 60 may also be integrated and referred to as a control valve.

In the following, a specific structure of the load sensitive valve is described based on the entire hydraulic system to explain an operation principle of the load sensitive valve provided by the present disclosure.

As shown in fig. 1, 2A, 3A, and 4A, the load sensitive valve 40 includes a main body portion 100 and a valve spool 200 located in the main body portion 100. The main body portion 100 includes a first chamber 110, a valve chamber 130, and a second chamber 120 connected in series, the first chamber 110 being connected to the outlet of the main pump 10 (node N1 in fig. 1), and the second chamber 120 being adapted to be connected to the load feedback (node N2 in fig. 1). The valve spool 200 is mainly located in the valve chamber 130 and extends from the first chamber 110 to the second chamber 120, where an end of the valve spool 200 facing the first chamber 110 is referred to as a first end 210 and an end of the valve spool 200 facing the second chamber 120 is referred to as a second end 220, such that the first end 210 comprises a first surface 201 for withstanding the pressure of the first chamber 110 and the second end 220 comprises a second surface 202 for withstanding the pressure of the second chamber 120.

In the embodiment of the present disclosure, the pressure bearing area of the first surface 201 is designed to be smaller than the pressure bearing area of the second surface 202 in the axial extension direction along the valve chamber 130, so that the output flow of the hydraulic system increases with increasing load pressure.

It should be noted that, in the embodiments of the present disclosure, the "pressure bearing area" is related to the area and shape of the surface for bearing pressure, and is not equal to the area of the surface for bearing pressure, and the "pressure bearing area" can be obtained by calculating the axial component of the force of the pressure on the pressure bearing surface along the spool (or the valve cavity 130).

Furthermore, if the entirety of the second surface 202 is located on the side of the valve spool 200 facing away from the first chamber 110, the "pressure-bearing area" of the second surface 202 may also be: the area of the orthogonal projection of the second surface 202 on a plane perpendicular to the axial direction of the spool 200 (or the valve chamber 130).

In the following, the working process of the load sensitive valve is compared under two schemes that the pressure bearing areas of the first surface and the second surface are respectively designed to be equal and unequal, so as to illustrate the working principle of the load sensitive valve provided by the embodiment of the disclosure.

Before describing the working principle of the load sensitive valve with the two structures, a mechanical model of the valve core of the load sensitive valve in a balanced state is established. For example, in an actual process, since a pressure drop may occur in the oil path, that is, the pressure at the node N2 may be lower than the pressure at the node N1, an elastic structure 300 for supporting the valve cartridge 200 may be provided at the second chamber 120, and the elastic structure 300 provides an elastic support for balancing the axial pressures of the first end portion 210 and the second end portion 220 of the valve cartridge 200. Assuming that the elastic structure 300 is a spring, in order to maintain the balance of the valve core (the hydraulic system maintains a constant flow state), the stiffness of the spring is K, and the compression amount is X, the axial stress provided by the spring supporting the valve core is K X (i.e. the product of K and X, K and X can be designed according to actual requirements). The manner for balancing the axial pressure of the first end portion 210 and the second end portion 220 of the valve core 200 may be selected according to actual needs, and is not limited to providing the elastic structure 300.

In addition, in case that the elastic structure 300 is provided, a base 400 for supporting the elastic structure 300 may be provided in the load sensitive valve, and the base 400 may be fixed in the second chamber 120 of the main body 100. It should be noted that, as shown in fig. 2A and 2B, in order to ensure the support of the valve core 200 by the elastic structure 300, a support body is disposed at one end of the elastic structure 300 for supporting the second end portion 220 of the valve core 200 to increase a contact area, in this case, an axial pressure caused by the pressure of the second chamber 220 is transmitted to the second end portion 220 of the valve core 200 through the support body, that is, a side surface of the second end portion 220 facing the second chamber 120 is still used as a pressure-bearing surface to transmit the pressure to the second surface 202 even if the second surface 202 is partially covered by the support body, i.e., an actual pressure-bearing area of the second surface 202 is not changed even though the support body is disposed in the whole process.

In a first design, i.e. assuming equal bearing areas of the first and second surfaces in the axial extension of the valve chamber:

based on the main pump initial full displacement output flow, a system pressure P (i.e., the output pressure of the main pump) is established, assuming that the load pressure is Px, the pressure-bearing area of the first surface is a, the pressure-bearing area of the second surface is Ax, and the differential pressure across the main valve 50 is controlled to be Δ P. Thus, under the condition that the hydraulic system maintains a constant flow rate state, the valve core is in a stress balance state: p × a = Px Ax + K × X.

For example, under the condition that the load pressure Px is reduced, the stress state of the valve core is changed to be P A > Px Ax + K X, so that the axial stress of the second end part of the valve core is smaller than the axial stress of the first end part of the valve core, the valve core of the load sensitive valve moves towards the second chamber, and the system pressure cavity oil (with the system pressure P) is led into the servo mechanism through the load sensitive valve, so that the servo piston of the servo mechanism is controlled to push the displacement of the main pump to be reduced, and the output pressure P of the main pump can be matched with the load pressure Px.

In the above process, since the system pressure feedback area a and the load pressure feedback area Ax of the spool of the load sensitive control valve are equal, it is known that the control differential pressure P-Px = kxx/a is constant, that is, the differential pressure Δ P = kxx/a before and after the control main valve is constant, that is, the differential pressure of the control main valve is proportional to the main pump flow, so that the system output flow can be ensured to be constant.

In the above design, the servo mechanism is configured to: in the case of an increase in the flow of system-pressure-chamber oil which is admitted via the load-sensitive valve (in which case the system pressure P also increases), the main pump displacement is driven to decrease in order to lower the system pressure P, and correspondingly, in the case of a decrease in the flow of system-pressure-chamber oil which is admitted via the load-sensitive valve (in which case the system pressure P also decreases), the main pump displacement is driven to increase in order to raise the system pressure P.

In the first design described above, when the load sensitive valve maintains the hydraulic system at a constant flow, if the load pressure Px rises, the actuator leakage increases, causing the actuator to slow down. In addition, as the load pressure Px increases, the feedback loop of the load-sensitive valve (for example, at X in fig. 1, where the pressure can represent the load feedback pressure) also decreases due to the increase of the leakage amount of the feedback loop, resulting in unequal load pressure and load feedback pressure, i.e., the load feedback pressure Px is smaller than the load pressure, which results in the simultaneous decrease of the system pressure P output by the main pump, during which the control main valve keeps the load pressure unchanged due to the decrease of the system pressure P output by the main pump, i.e., the differential pressure Δ P of the control main valve becomes smaller, which results in a smaller output flow of the control main valve and further causes the deceleration of the actuator. In this way, this design is confronted with a problem that the load pressure rises and the actuator is decelerated more than necessary.

The load sensitive valve in the second design provided by the embodiments of the present disclosure can solve the technical problem existing in the first design, in the load sensitive valve in the second design, the pressure bearing areas of the first surface and the second surface of the valve core in the axial extension direction of the valve cavity are not equal, that is, the pressure bearing area of the first surface in the axial extension direction of the valve cavity is smaller than the pressure bearing area of the second surface in the axial extension direction of the valve cavity. Based on some parameters of the model under the first design, and with reference to fig. 1, fig. 2A, fig. 3A, and fig. 4A, the technical principle of the second design is as follows:

in the axial extension direction of the valve chamber 130, let the bearing area of the first surface 201 be a and the bearing area of the second surface 202 be Ax, and assume Ax > a.

In the case where the hydraulic system maintains a state in which the flow rate is constant, P × a-Px Ax = K × X.

The above formula is modified to P-Px Ax/a = K X/a, and further deduces P-Px + Px-Px Ax/a = K X/a.

Let P-Px = Δ P, the above formula can be transformed into formula one: Δ P = K × X/a-Px (1-Ax/a).

In one of the equations, the parameters K, X, ax and A are fixed values, so that only two variables Δ P and Px exist, and since Ax > A, i.e., 1-Ax/A is negative, Δ P and Px are linearly proportional, i.e., Δ P increases with increasing Px. In this way, it is ensured that the output flow of the hydraulic system (output flow of the main pump 10) increases with the increase of the load pressure Px, so as to compensate the flow loss caused by the leakage of the actuator 30 and the leakage of the feedback loop of the load sensitive valve 40 (as shown at X in fig. 1), thereby solving the technical problem in the first design.

In the embodiment of the disclosure, the difference degree of the pressure bearing areas of the first surface and the second surface of the valve core of the load sensitive valve can be designed according to actual needs. For example, in view of the conventional hydraulic system to which the current load sensitive valve is applied, in the case that the pressure-bearing area of the second surface is 1.01 to 1.1 times of the pressure-bearing area of the first surface, the technical problem existing in the first design can be substantially alleviated or solved, and in addition, in the case that the multiple relation is further 1.03 to 1.07 or further 1.04 to 1.06, the application of the current conventional hydraulic system can be more matched.

In the embodiment of the disclosure, the technical means for realizing the difference of the pressure bearing areas of the first surface and the second surface of the valve core is not limited, and the valve core can be designed according to the requirements of the actual process. For example, in the load-sensitive valve provided in at least one embodiment of the present disclosure, as shown in fig. 2A, 3A and 4A, the valve chamber 130 includes a first chamber section 131, a third chamber section 133 and a second chamber section 132 connected in sequence, the first chamber section 131 is used for accommodating the first end 210 of the valve spool 200, and the second chamber section 132 is used for accommodating the second end 220 of the valve spool 200. In a plane perpendicular to the axial extension of the valve chamber 130, the cross-sectional dimension of the first chamber section 131 is smaller than the cross-sectional dimension of the second chamber section 132, i.e. the first chamber section 131 is thinner than the second chamber section 132, such that the area of the first surface 201 is directly smaller than the area of the second surface 202, such that the pressure bearing area of the first surface 201 may be smaller than the pressure bearing area of the second surface 202.

In embodiments of the present disclosure, the cross-sectional dimensions (e.g., diameters) of the first and second cavity sections may be determined according to the specific dimensions (e.g., cross-sectional areas) of the first and second ends of the spool. For example, in the load sensitive valve provided in at least one embodiment of the present disclosure, as shown in fig. 2A, 3A and 4A, the cross-sectional dimension of the first cavity segment 131 and the cross-sectional dimension of the first end portion 210 are substantially equal on a plane perpendicular to the axial extension direction of the valve cavity 130, and the surface of the first end portion 210 facing the first cavity 110 is a first surface 201; further, the cross-sectional dimensions of the second cavity segment 132 and the second end 220 are substantially equal, and the surface of the second end 220 facing the second cavity 120 is the second surface 202.

In the embodiment of the present disclosure, a plurality of flow passages may be disposed in the load-sensitive valve, the flow passages being communicated with the valve cavity, and the flow passages are respectively used for communicating a servo mechanism (e.g., a servo cavity), a low-pressure cavity (e.g., a tank), and the like, the spool is disposed to space at least one of the flow passages in a specific position state, and when the spool moves due to pressure variation of the first and second chambers, the specific flow passages or the flow passages and the chamber (e.g., the first chamber) may be communicated with each other to regulate oil pressure of the servo mechanism 20, so that displacement of the main pump 10 is controlled by the servo mechanism 20.

For example, in a load sensitive valve provided in at least one embodiment of the present disclosure, as shown in fig. 1, 2A, 3A, and 4A, the valve spool 200 may further include a connection portion 230 for connecting the first end portion 210 and the second end portion 220, the connection portion 230 being received in the third cavity section 133 of the valve cavity 130. The main body 100 is provided with a first flow passage 121, a second flow passage 122 and a third flow passage 123 which are communicated to the third cavity section 133, the first flow passage 121, the second flow passage 122 and the third flow passage 123 are positioned between the first chamber 110 and the second chamber 120, and the third flow passage 123, the first flow passage 121 and the second flow passage 122 are sequentially arranged along the direction from the first chamber 110 to the second chamber 120. The first flow passage 121 communicates with a servo chamber of the servo mechanism 20, the second flow passage 122 communicates with a low pressure chamber (e.g., a tank), and the third flow passage 123 communicates with an outlet of the main pump 10 (node N1 in fig. 1) to achieve pressure common to the first chamber 110 (e.g., at node N3 in fig. 1). A flow passage that allows the first flow passage 121 to communicate with the third flow passage 123 and that allows the first flow passage 121 to communicate with the second flow passage 122 is provided in the third cavity section 133 of the valve chamber 130 or the connection portion 230 of the valve spool 200, and a first protrusion structure that blocks communication between the first flow passage 121 and the third flow passage 123 and between the first flow passage 121 and the second flow passage 122 in a case where the hydraulic system maintains a state in which the flow rate is constant (for example, a first state described below) and that allows the first flow passage 121 to communicate with the third flow passage 123 or allows the first flow passage 121 to communicate with the second flow passage 122 as the valve spool 200 moves is provided in the third cavity section 133 of the valve chamber 130 or in the connection portion 230 of the valve spool 200.

In the embodiment of the present disclosure, there are three positions of the valve core, and the operation principle of the load sensitive valve in the three positions will be described with reference to fig. 2A, fig. 5, and fig. 6.

As shown in fig. 2A, the valve spool 200 is in a first state of force equilibrium, i.e., P × a = Px Ax + K × X. In this case, the spool 200 is located at a preset position so that the space between the first flow passage 121 and the second flow passage 122 is closed.

As shown in fig. 5, assuming that the load pressure Px is decreased, the valve element 200 is in the second state where the force applied to the first end portion 210 is greater than the force applied to the second end portion 220, i.e., P × a < Px Ax + K × X, and the valve element 200 is moved toward the second chamber 120 with respect to the preset position so that the first flow passage 121 and the third flow passage 123 are communicated (and actually, the first flow passage 121 and the first chamber 110 are also communicated). Thus, the oil with high pressure sequentially passes through the third flow passage 123 and the first flow passage 121 to enter the servo cavity of the servo mechanism 20, so that the servo mechanism 20 drives the swash plate of the main pump 10 to reduce the displacement of the main pump 10, that is, to reduce the system pressure P, and as the system pressure P gradually decreases, the stress of the valve spool 200 gradually tends to P × a = Px + K × X, so as to return to the stress balance state. In the second state, since the first chamber 110 and the first flow channel 121 are spaced, it is possible to prevent a large pressure fluctuation from occurring in the first chamber 110, thereby ensuring the accuracy of the load sensitive valve.

As shown in fig. 6, assuming that the load pressure Px increases, the valve spool is in a third state where the force applied to the first end portion 210 is smaller than the force applied to the second end portion 220, i.e., P × a > Px Ax + K × X, and the valve spool 200 is moved toward the first chamber 110 with respect to the preset position so that the first flow passage 121 and the second flow passage 122 are communicated. Thus, the oil in the servo chamber of the servo mechanism 20 is discharged (e.g., returned to the oil tank) through the first flow passage 121 and the second flow passage 122 in sequence, and as the pressure in the servo chamber decreases, the servo mechanism 20 drives the swash plate of the main pump 10 to increase the displacement of the main pump 10, i.e., increase the system pressure P, and as the system pressure P gradually increases, the force applied to the valve spool 200 gradually tends to be pa = Px Ax + K X, so as to return to the force balance state.

At least one embodiment of the present disclosure provides a variable displacement hydraulic pump including a main pump, a servo mechanism, and the load sensitive valve of the above embodiments. The main pump includes a swash plate, a cylinder block, and an axial plunger. The first chamber of the load sensitive valve is communicated to the output end of the main pump. The servo mechanism is connected to the swash plate and is connected with the load sensitive valve through a hydraulic oil path to control the displacement of the main pump. The relationship between the components included in the variable displacement hydraulic pump can be referred to the related description in the embodiment shown in fig. 1, and the description thereof is omitted.

At least one embodiment of the present disclosure provides a hydraulic system including the variable displacement hydraulic pump of the second aspect described above, a control valve, and an actuator driven by the variable displacement hydraulic pump. The control valve is disposed between the variable displacement hydraulic pump and the actuator and controls a pressure supplied to the actuator, and includes a control main valve and a pressure compensator disposed between the control main valve and the actuator. The second chamber of the load sensitive valve is connected between the actuator and the pressure compensator. The relationship between the structures included in the hydraulic system can be referred to the related description of the embodiment shown in fig. 1, and will not be described herein again.

The above description is meant to be illustrative of the preferred embodiments of the present disclosure and not to be taken as limiting the disclosure, as the invention is intended to cover any modifications, equivalents, etc. which fall within the spirit and scope of the present disclosure.

Claims (11)

1. A load sensitive valve for a variable displacement hydraulic pump, the load sensitive valve comprising:

the main body part comprises a first chamber, a valve cavity and a second chamber which are connected in sequence; and

a valve spool located in the valve chamber and including a first end facing the first chamber and a second end facing the second chamber, the first end including a first surface for withstanding the pressure of the first chamber and the second end including a second surface for withstanding the pressure of the second chamber;

wherein, in the axial extension direction of the valve cavity, the bearing area of the first surface is smaller than that of the second surface.

2. The load sensitive valve of claim 1,

the pressure-bearing area of the second surface is 1.01 to 1.1 times of the pressure-bearing area of the first surface.

3. The load sensitive valve of claim 1 or 2, wherein the valve chamber comprises a first chamber section for receiving the first end portion and a second chamber section for receiving the second end portion, and

on a plane perpendicular to the axial extension direction of the valve cavity, the cross-sectional dimension of the first cavity section is smaller than the cross-sectional dimension of the second cavity section.

4. The load sensitive valve of claim 3, wherein, in a plane perpendicular to the axial extent of the valve chamber,

a cross-sectional dimension of the first cavity segment and a cross-sectional dimension of the first end portion are substantially equal, a surface of the first end portion facing the first chamber being the first surface; and/or

The cross-sectional dimension of the second cavity segment and the cross-sectional dimension of the second end portion are substantially equal, the surface of the second end portion facing the second cavity being the second surface.

5. The load sensitive valve of claim 1 or 2, further comprising:

and the elastic structure is positioned in the second chamber, one end of the elastic structure is supported on the main body part, and the other end of the elastic structure supports the second end part of the valve core.

6. The load sensitive valve of claim 5,

the valve element further comprises a connecting part, and the first end part and the second end part are connected through the connecting part;

the valve cavity comprises a third cavity section for accommodating the connecting part;

the main body further includes a first flow passage and a second flow passage, the first flow passage and the second flow passage communicating to the third cavity section, and the first flow passage being located between the first cavity and the second flow passage; and

in a first state that the valve core is stressed and balanced, the valve core is located at a preset position so that the first flow passage and the second flow passage are closed; or

In a second state that the stress of the first end part of the valve core is larger than that of the second end part, the valve core moves towards the second chamber relative to a preset position so that the first flow passage is communicated with the first chamber; or

In a third state that the force applied to the first end of the valve element is smaller than the force applied to the second end, the valve element moves towards the first chamber relative to a preset position, so that the first flow passage and the second flow passage are communicated.

7. The load sensitive valve of claim 6,

the body portion further includes a third flow passage in communication with the first chamber, the third flow passage communicating to the third cavity section, and the third flow passage being located between the first chamber and the first flow passage, an

In the second state, the first flow passage and the third flow passage are communicated.

8. A variable displacement hydraulic pump, comprising:

the main pump comprises a swash plate, a cylinder body and an axial plunger;

a load sensitive valve according to any of claims 1 to 5 having its first chamber connected to the output of the main pump; and

and the servo mechanism is connected to the swash plate and is connected with the load sensitive valve through a hydraulic oil way so as to control the displacement of the main pump.

9. A variable displacement hydraulic pump as claimed in claim 8,

the valve core further comprises a connecting part, and the first end part of the valve core and the second end part of the valve core are connected through the connecting part;

the valve cavity comprises a cavity section for accommodating the connecting part;

the main body part further comprises a first flow passage and a second flow passage, one end of the first flow passage is communicated to the cavity section, the other end of the first flow passage is communicated to the servo mechanism, one end of the second flow passage is communicated to the cavity section, the other end of the second flow passage is used for drainage, and the first flow passage is located between the first cavity and the second flow passage; and

in a first state that the valve core is stressed in balance, the valve core is located at a preset position so that the first flow passage and the second flow passage are closed; or

In a second state that the stress of the first end part of the valve core is larger than that of the second end part, the valve core moves towards the second chamber relative to a preset position so that the first flow passage is communicated with the first chamber; or

In a third state that the force applied to the first end of the valve element is smaller than the force applied to the second end, the valve element moves towards the first chamber relative to a preset position, so that the first flow passage and the second flow passage are communicated.

10. The variable displacement hydraulic pump of claim 9, the main body portion further including a third flow passage in communication with the first chamber, the third flow passage communicating to the cavity segment, and the third flow passage being located between the first chamber and the first flow passage, and

in the second state, the first flow passage and the third flow passage are communicated.

11. A hydraulic system, comprising:

the variable displacement hydraulic pump as claimed in any one of claims 8-10;

an actuator driven by the variable displacement hydraulic pump;

a control valve disposed between the variable displacement hydraulic pump and the actuator and controlling a pressure supplied to the actuator, the control valve including a control main valve and a pressure compensator disposed between the control main valve and the actuator;

wherein the second chamber of the load sensitive valve is connected between the actuator and the pressure compensator.

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