Hydraulic system and engineering machinery

Abstract

The invention provides a hydraulic system and engineering machinery. The hydraulic system comprises a hydraulic pump, a proportional directional valve, a compensation valve and a first overflow valve. An oil outlet of the compensation valve is communicated with an oil inlet of the proportional reversing valve, and an oil inlet of the compensation valve is communicated with an oil outlet of the hydraulic pump; an oil inlet of the first overflow valve can selectively communicate with a first oil port of the proportional reversing valve or a second oil port of the proportional reversing valve, a first cavity of the compensation valve and the oil inlet of the first overflow valve are connected with the same oil port of the proportional reversing valve, and an oil inlet of the proportional reversing valve can communicate with a second cavity of the compensation valve. The first chamber and the second chamber are located on a rearward side of the compensation valve. As the compensation valve can control the front and back pressure difference of the proportional reversing valve to be basically constant, the output flow is not influenced by the load. The overflow valve limits the maximum pressure of an oil way, and the minimum overflow energy consumption is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control, and in particular to a hydraulic system and engineering machinery. Background Art

[0002] The hydraulic system of the forklift currently uses a proportional reversing valve to control the direction of the action, such as Figure 1 As shown, when the forklift needs to work, the hydraulic pump outputs hydraulic oil, and the oil output by the hydraulic pump reaches the proportional reversing valve 1 from the P port. When the S1 end of the proportional reversing valve 1 is energized, the hydraulic oil at the P port reaches the B port, pushing the actuator 10 (such as a hydraulic cylinder) to move in one direction; when the S2 end of the proportional reversing valve 1 is energized, the hydraulic oil at the P port reaches the A port, pushing the actuator 10 (such as a hydraulic cylinder) to move in the other direction. However, when the actuator cannot be fed with oil, the output oil of the actuator will directly flow into the oil tank through the stable overflow valve 1' connected to the inlet of the proportional reversing valve 1, resulting in serious overflow loss.

[0003] Therefore, a hydraulic system is urgently needed to solve the above-mentioned technical problems. Summary of the invention

[0004] The object of the present invention is to provide a hydraulic system capable of reducing overflow losses.

[0005] Another object of the present invention is to provide an engineering machine capable of reducing overflow loss during the operation of the engineering machine.

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

[0007] In a first aspect, a hydraulic system is provided for controlling oil entering an actuator, comprising:

[0008] A hydraulic pump having an oil outlet;

[0009] Proportional reversing valve, used for reversing;

[0010] A compensating valve, used to adjust the pressure difference between the inlet and outlet of the proportional reversing valve, the oil outlet of the compensating valve is connected to the oil inlet of the proportional reversing valve, and the oil inlet of the compensating valve is connected to the oil outlet of the hydraulic pump;

[0011] a first overflow valve, wherein an oil inlet of the first overflow valve can be selectively connected to a first oil port of the proportional reversing valve or a second oil port of the proportional reversing valve;

[0012] In which, the first chamber of the compensation valve can be selectively connected to the first oil port of the proportional reversing valve or the second oil port of the proportional reversing valve, and the first chamber of the compensation valve and the oil inlet of the first overflow valve are connected to the same oil port of the proportional reversing valve, the oil inlet of the proportional reversing valve can be connected to the second chamber of the compensation valve, and the first chamber and the second chamber are located on the back side of the compensation valve.

[0013] As a preferred technical solution of the above-mentioned hydraulic system, it also includes a shuttle valve, the two inlets of which are respectively connected to the first oil port of the proportional reversing valve and the second oil port of the proportional reversing valve; the outlet of the shuttle valve is respectively connected to the oil inlet of the first overflow valve and the first chamber of the compensation valve.

[0014] As a preferred technical solution of the above hydraulic system, the shuttle valve is provided with a first throttling structure, and the first throttling structure is used to limit the flow of hydraulic oil flowing from the first oil port or the second oil port to the first overflow valve; or,

[0015] A first throttling structure is provided between the shuttle valve and the first relief valve, and the first throttling structure is used to limit the flow of the hydraulic oil flowing out of the shuttle valve.

[0016] As a preferred technical solution of the above-mentioned hydraulic system, the first throttling structure includes a first throttling hole and a second throttling hole, and the aperture of the first throttling hole and the aperture of the second throttling hole are both smaller than the aperture of each oil outlet; or, the first throttling structure includes a throttle valve.

[0017] As a preferred technical solution for the above-mentioned hydraulic system, a second throttling structure is also provided on the compensating valve, and the second throttling structure includes a throttling part. The compensating valve has two working states. When the compensating valve is in the first working state, the inlet of the compensating valve and the outlet of the compensating valve are directly connected. When the compensating valve is in the second working state, the inlet of the compensating valve is connected to the outlet of the compensating valve through the throttling part.

[0018] As a preferred technical solution of the above hydraulic system, the second throttling structure also includes a throttling gap, and the throttling gap is used to limit the flow of hydraulic oil flowing from the outlet of the compensation valve to the non-spring end of the compensation valve.

[0019] As a preferred technical solution for the above hydraulic system, the proportional reversing valve is a three-position four-way solenoid valve.

[0020] As a preferred technical solution of the above hydraulic system, it also includes a second overflow valve, the oil inlet of the compensation valve is connected to the oil inlet of the second overflow valve, and the oil outlet of the second overflow valve is connected to the oil tank.

[0021] In a second aspect, there is provided an engineering machinery comprising the hydraulic system described in any of the above schemes.

[0022] As a preferred technical solution of the above-mentioned engineering machinery, the engineering machinery includes a forklift.

[0023] The present invention has at least the following beneficial effects:

[0024] The hydraulic system provided by the present invention comprises a hydraulic pump, a proportional reversing valve, a compensating valve and a first overflow valve. The hydraulic pump has an oil outlet, the oil inlet of the hydraulic pump is connected to the oil tank, and the hydraulic pump provides power for the oil; the proportional reversing valve is used for reversing; the compensating valve is used to adjust the pressure difference between the inlet and outlet of the proportional reversing valve, the oil outlet of the compensating valve is connected to the oil inlet of the proportional reversing valve, and the oil inlet of the compensating valve is connected to the oil outlet of the hydraulic pump, thereby realizing the balanced control of the oil amount entering the actuator; the oil inlet of the first overflow valve can be selectively connected to the first oil port of the proportional reversing valve or the second oil port of the proportional reversing valve, and the first chamber of the compensating valve and the oil inlet of the first overflow valve are connected to the same oil port of the proportional reversing valve, and the oil inlet of the proportional reversing valve can be connected to the second chamber of the compensating valve, and the first chamber and the second chamber are located on the back side of the compensating valve.

[0025] In the hydraulic system and engineering machinery provided by the present invention, when the pressure of the hydraulic oil entering the actuator reaches the set pressure of the first relief valve, the first relief valve will overflow, so that the pressure of the hydraulic oil entering the actuator will no longer increase. At this time, because the maximum pressure of the oil outlet of the proportional reversing valve has been limited, the pressure will be fed back to the first chamber of the compensation valve, so that the pressure at the first chamber end of the compensation valve will no longer increase. At the same time, the pressure will also be fed back to the oil inlet end of the proportional reversing valve (that is, the second chamber of the compensation valve), so that the opening of the compensation valve becomes smaller, and the flow output to the actuator also becomes smaller. This will have a positive effect on the energy consumption of the system and reduce energy consumption. The compensation valve can control the front and rear pressure difference of the proportional reversing valve to be basically constant, so that the output flow is not affected by the load. The maximum pressure of the oil circuit limited by the relief valve achieves the minimum overflow energy consumption. 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 Hydraulic schematic diagram provided for background technology;

[0028] Figure 2 A hydraulic principle diagram of a hydraulic system provided in an embodiment of the present invention.

[0029] In the figure:

[0030] 1. Proportional reversing valve; 2. Compensation valve; 3. Shuttle valve; 4. First relief valve; 5. First throttle hole; 6. Second throttle hole; 7. Throttle section; 8. Throttle gap; 9. Second relief valve; 10. Actuator; 1', Stable relief valve. DETAILED DESCRIPTION

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In the description of this embodiment, the terms "upper", "lower", "right", etc., 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 operated 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.

[0035] The present invention provides a hydraulic system that can reduce overflow damage while controlling the speed of oil entering an actuator to achieve controllable actuator speed. Figure 2As shown, the hydraulic system includes a hydraulic pump, a proportional reversing valve 1, a compensating valve 2 and a first relief valve 4. The hydraulic pump has an oil outlet, and the oil inlet of the hydraulic pump is connected to the oil tank, and the hydraulic pump provides power for the oil; the proportional reversing valve 1 is used for reversing, so that the actuator is suitable for the needs of different working occasions; the compensating valve 2 is used to adjust the pressure difference between the inlet and outlet of the proportional reversing valve 1, the oil outlet of the compensating valve 2 is connected to the oil inlet of the proportional reversing valve 1, and the oil inlet of the compensating valve 2 is connected to the oil outlet of the hydraulic pump, so as to achieve balanced control of the oil amount entering the actuator; the oil inlet of the first relief valve 4 can be selectively connected to the first oil port of the proportional reversing valve 1 or the second oil port of the proportional reversing valve 1, and the first chamber of the compensating valve 2 and the oil inlet of the first relief valve 4 are connected to the same oil port of the proportional reversing valve 1, and the oil inlet of the proportional reversing valve 1 can be connected to the second chamber of the compensating valve 2, and the first chamber and the second chamber are located on the back side of the compensating valve 2.

[0036] In the hydraulic system provided by the present invention, when the pressure of the hydraulic oil entering the actuator reaches the set pressure of the first relief valve 4, the first relief valve 4 will overflow, so that the pressure of the hydraulic oil entering the actuator will no longer increase. At this time, because the maximum pressure of the oil outlet of the proportional reversing valve 1 has been limited, the pressure will be fed back to the first chamber of the compensation valve 2, so that the pressure at the first chamber end of the compensation valve 2 will no longer increase. At the same time, the pressure will also be fed back to the oil inlet end of the proportional reversing valve 1 (that is, the second chamber of the compensation valve 2), so that the opening of the compensation valve 2 becomes smaller, and the flow output to the actuator also becomes smaller. This will have a positive effect on the energy consumption of the system and reduce energy consumption. The compensation valve 2 can control the front and rear pressure difference of the proportional reversing valve 1 to be basically constant, so that the output flow is not affected by the load. The maximum pressure of the limited oil circuit of the relief valve achieves the minimum overflow energy consumption.

[0037] Taking the application of the hydraulic system to a forklift as an example, in the present invention, when the forklift is working, the oil of the hydraulic pump enters from the P port, passes through the compensation valve 2 to reach the inlet of the proportional reversing valve 1, and at the same time, the oil will also reach the effective surface of one end of the valve core of the compensation valve 2, and the area of ​​the effective surface is A1. When the control current is passed through the S1 end of the proportional reversing valve 1, the oil at the P port is output to the B port through the proportional reversing valve 1. At this time, due to the flow of the oil, a pressure difference is formed at the inlet and outlet of the proportional reversing valve 1. Assuming that the inlet pressure is P1 and the outlet pressure is P2, the front and rear pressure difference of the proportional reversing valve 1 will be △P. After the proportional reversing valve 1 is energized, a part of the oil is also fed back to the spring chamber of the valve core of the compensation valve 2 after being selected by the shuttle valve 3, and the effective area is also A1. In this way, the front and rear pressure difference of the proportional reversing valve 1 will be equal to the spring compression pressure of the compensation valve 2, and the output flow of the proportional reversing valve 1 will be kept stable. The hydraulic oil at the B port will push the actuator (such as a hydraulic cylinder) to move in one direction without being affected by the load;

[0038] When the pressure of the oil outlet load reaches the set pressure of the first relief valve 4, the first relief valve 4 overflows, so that the spring chamber force of the valve core of the compensation valve 2 is limited, and the valve core of the compensation valve 2 moves toward the spring side under the action of the inlet pressure, slowly closing the valve core opening of the compensation valve 2, so that the flow rate of the oil outlet is reduced and gradually reaches the set pressure of the first relief valve 4. In this way, the overflow amount of the first relief valve 4 is very small, and the overflow loss of the working link B port will be very small, with obvious energy-saving effect, and thus more refined control and greatly improved experience.

[0039] When the control current is passed through the S2 end of the proportional reversing valve 1, the oil at the P port is output to the A port through the proportional reversing valve 1. At this time, due to the flow of oil, a pressure difference is formed at the inlet and outlet of the proportional reversing valve 1. Assuming that the inlet pressure is P1 and the outlet pressure is P2, the front and rear pressure difference of the proportional reversing valve 1 will be △P. After the proportional reversing valve 1 is energized, a part of the oil is also fed back to the spring chamber of the valve core of the compensation valve 2 after being selected by the shuttle valve 3, and the effective area is also A1. In this way, the front and rear pressure difference of the proportional reversing valve 1 will be equal to the spring compression pressure of the compensation valve 2, keeping the output flow of the proportional reversing valve 1 stable. The hydraulic oil at the A port will push the actuator (such as a hydraulic cylinder) to move in one direction without being affected by the load;

[0040] When the pressure of the oil outlet load reaches the set pressure of the first relief valve 4, the first relief valve 4 overflows, so that the spring chamber force of the valve core of the compensation valve 2 is limited, and the valve core of the compensation valve 2 moves toward the spring side under the action of the inlet pressure, slowly closing the valve core opening of the compensation valve 2, so that the flow rate of the oil outlet is reduced and gradually reaches the set pressure of the first relief valve 4. In this way, the overflow amount of the first relief valve 4 is very small, and the overflow loss of the working link A port will be very small, with obvious energy-saving effect, and thus more refined control and greatly improved experience.

[0041] In some embodiments, the hydraulic system further comprises a shuttle valve 3, wherein two inlets of the shuttle valve 3 are respectively connected to the first oil port of the proportional reversing valve 1 and the second oil port of the proportional reversing valve 1; and an outlet of the shuttle valve 3 is respectively connected to the oil inlet of the first relief valve 4 and the first chamber of the compensation valve 2. The arrangement of the shuttle valve 3 enables the first relief valve 4 to selectively connect to the first oil port of the proportional reversing valve 1 or the second oil port of the proportional reversing valve 1.

[0042] In some embodiments, the shuttle valve 3 is provided with a first throttling structure, which is used to limit the flow of hydraulic oil flowing from the first oil port or the second oil port to the first relief valve 4, and to reduce the impact of the hydraulic oil on the valve core of the compensation valve 2. In this way, no matter whether the hydraulic oil flows out from the A port or the B port of the actuator, it can be throttled by the first throttling structure, so that the flow into the compensation valve 2 and the first relief valve 4 is stable, and the compensation valve 2 and the first relief valve 4 operate smoothly without impact.

[0043] For example, the first throttling structure includes a first throttling hole 5 and a second throttling hole 6, and the apertures of the first throttling hole 5 and the second throttling hole 6 are both smaller than the apertures of the oil outlets.

[0044] In some other embodiments, a first throttling structure is provided between the first relief valve 4 and the shuttle valve 3, and the first throttling structure is used to limit the flow of the hydraulic oil flowing from the first oil port or the second oil port to the first relief valve 4. With such a configuration, the flow of the hydraulic oil flowing into the compensation valve 2 and the first relief valve 4 can be stabilized, and the compensation valve 2 and the first relief valve 4 can operate smoothly without impact. For example, the first throttling structure includes a throttling valve, which can throttle the hydraulic oil flowing out of the shuttle valve 3 to ensure the stability of the hydraulic oil flowing into the spring chamber of the compensation valve 2 and the first relief valve 4.

[0045] Of course, in other embodiments, the first throttling structure may also be a third throttling hole arranged on the shuttle valve 3 , and the third throttling hole is specifically arranged at the oil outlet of the shuttle valve 3 .

[0046] In some embodiments, the compensating valve 2 is further provided with a second throttling structure, which includes a throttling portion 7. The compensating valve 2 has two working states. When the compensating valve 2 is in the first working state, the inlet of the compensating valve 2 and the outlet of the compensating valve 2 are directly connected. When the compensating valve 2 is in the second working state, the inlet of the compensating valve 2 is connected to the outlet of the compensating valve 2 through the throttling portion 7. The setting of the throttling portion 7 can stabilize the hydraulic oil flowing from the inlet of the compensating valve 2 to the outlet of the compensating valve 2, so that the valve core of the compensating valve 2 operates smoothly. It can be understood that the inlet and outlet openings of the valve core of the compensating valve 2 are determined according to the pressure fed back by the shuttle valve 3, the oil inlet amount and the oil inlet pressure.

[0047] In some embodiments, the second throttling structure further includes a throttling gap 8, which is used to limit the flow of hydraulic oil flowing from the outlet of the compensation valve 2 to the non-spring end of the compensation valve 2, and the aperture of the throttling gap 8 is smaller than the aperture of each oil outlet. The setting of the throttling gap 8 can stabilize the hydraulic oil entering the non-spring end of the compensation valve 2 and prevent the non-spring end from receiving impact.

[0048] In some embodiments, the proportional reversing valve 1 is a three-position four-way solenoid valve. The proportional reversing valve 1 includes a first oil port, a second oil port, a third oil port and a fourth oil port. When the valve core of the proportional reversing valve 1 is in the left position, the first oil port is connected to the fourth oil port, and the second oil port is connected to the third oil port. When the valve core of the proportional reversing valve 1 is in the right position, the second oil port is connected to the fourth oil port, and the first oil port is connected to the third oil port. When the valve core of the proportional reversing valve 1 is in the middle position, the proportional reversing valve 1 blocks the connection.

[0049] In some embodiments, the hydraulic system further comprises a second relief valve 9, the oil inlet of the compensation valve 2 is connected to the oil inlet of the second relief valve 9, and the oil outlet of the second relief valve 9 is connected to the oil tank. The second relief valve 9 can be used for the oil flowing out of the hydraulic pump. The present invention also provides an engineering machine, which includes the hydraulic system provided in this embodiment.

[0050] For example, the construction machinery is a forklift.

[0051] Since the hydraulic system described above is included, the engineering machinery of the embodiment of the present invention has all the advantages and beneficial effects of the above embodiments, which will not be described in detail herein.

[0052] In addition, 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 hydraulic system for controlling oil entering an actuator (10), characterized in that: include: A hydraulic pump having an oil outlet; A proportional directional valve (1) for switching direction; A compensating valve (2) is used to adjust the pressure difference between the inlet and outlet of the proportional reversing valve (1), the oil outlet of the compensating valve (2) being connected to the oil inlet of the proportional reversing valve (1), and the oil inlet of the compensating valve (2) being connected to the oil outlet of the hydraulic pump; a first overflow valve (4), wherein an oil inlet of the first overflow valve (4) can be selectively connected to a first oil port of the proportional reversing valve (1) or a second oil port of the proportional reversing valve (1); The first chamber of the compensating valve (2) can selectively communicate with the first oil port of the proportional reversing valve (1) or the second oil port of the proportional reversing valve (1), and the first chamber of the compensating valve (2) and the oil inlet of the first overflow valve (4) are connected to the same oil port of the proportional reversing valve (1), and the oil inlet of the proportional reversing valve (1) can communicate with the second chamber of the compensating valve (2), and the first chamber and the second chamber are located on the back side of the compensating valve (2).

2. The hydraulic system according to claim 1, characterized in that: It also comprises a shuttle valve (3), the two inlets of which are respectively connected to the first oil port of the proportional reversing valve (1) and the second oil port of the proportional reversing valve (1); the outlet of the shuttle valve (3) is respectively connected to the oil inlet of the first overflow valve (4) and the first chamber of the compensation valve (2).

3. The hydraulic system according to claim 2, characterized in that: The shuttle valve (3) is provided with a first throttling structure, and the first throttling structure is used to limit the flow of hydraulic oil flowing from the first oil port or the second oil port to the first overflow valve (4); or, A first throttling structure is provided between the shuttle valve (3) and the first overflow valve (4), and the first throttling structure is used to limit the flow rate of the hydraulic oil flowing out of the shuttle valve (3).

4. The hydraulic system according to claim 3, characterized in that: The first throttling structure comprises a first throttling hole (5) and a second throttling hole (6), and the apertures of the first throttling hole (5) and the second throttling hole (6) are both smaller than the apertures of the oil outlets; or, The first throttling structure includes a throttle valve.

5. The hydraulic system according to any one of claims 1 to 4, characterized in that: The compensating valve (2) is also provided with a second throttling structure, the second throttling structure comprising a throttling portion (7). The compensating valve (2) has two working states. When the compensating valve (2) is in the first working state, the inlet of the compensating valve (2) and the outlet of the compensating valve (2) are directly connected. When the compensating valve (2) is in the second working state, the inlet of the compensating valve (2) is connected to the outlet of the compensating valve (2) through the throttling portion (7).

6. The hydraulic system according to claim 5, characterized in that: The second throttling structure further comprises a throttling gap (8), wherein the throttling gap (8) is used to limit the flow of hydraulic oil flowing from the outlet of the compensating valve (2) to the non-spring end of the compensating valve (2).

7. The hydraulic system according to any one of claims 1 to 4, characterized in that: The proportional reversing valve (1) is a three-position four-way solenoid valve.

8. The hydraulic system according to any one of claims 1 to 4, characterized in that: It also comprises a second overflow valve (9), the oil inlet of the compensation valve (2) is connected to the oil inlet of the second overflow valve (9), and the oil outlet of the second overflow valve (9) is connected to the oil tank.

9. An engineering machine, characterized in that: A hydraulic system comprising any one of claims 1-8.

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