Load-sensitive mechanical precise control hydraulic system

Abstract

The invention belongs to the technical field of engineering machinery, and discloses a load-sensitive mechanical precise control hydraulic system, and a machine can realize switching between a normal working state and a precise working state through a switch according to needs. The constant-power load-sensitive plunger pump is mainly composed of a constant-power load-sensitive plunger pump body, an LS electromagnetic valve and a load-sensitive main valve. The LS electromagnetic valve is controlled to be opened and closed through an electric signal. When the loading machine is started, the electric signal does not control the LS electromagnetic valve, and all operation actions of the whole machine are normally operated according to the designed speed; when the LS electromagnetic valve is controlled to be opened by the electric signal, the constant-power load-sensitive plunger pump is influenced by the increase of the load pressure, and the pump flow is reduced, so that each operation action of the machine is slowed down during heavy load, and accurate operation is realized; when accurate control is not needed, the electric signal does not control the LS electromagnetic valve, and the machine can recover normal operation.

Description

Technical Field

[0001] The present invention relates to a precise control hydraulic system for a load-sensitive backhoe loader, belonging to the technical field of construction machinery. Background Art

[0002] After the backhoe loader equipped with a negative-sensitivity constant power control piston pump has completed the overall machine design and production trial, the flow rate and pressure required for each operating action have been adjusted. Therefore, during the operation of the backhoe loader, the time for each operating action is fixed, meeting the requirements of most working conditions. However, for individual working conditions where the backhoe loader needs to complete precise installation work, since the operating time of the whole machine is determined, it cannot meet the precise adjustment requirements of this working condition. Therefore, there is an urgent need to invent a load-sensitive mechanical precise control hydraulic system, which can switch between the normal working state and the precise working state according to needs through a switch. Summary of the Invention

[0003] The problem to be solved by the present invention is to provide a load-sensitive mechanical precise control hydraulic system with simple principle, strong versatility and wide application range, so as to solve the problem that the backhoe loader equipped with a load-sensitive constant power control hydraulic system requires different operating speeds under different working conditions.

[0004] To achieve the above object, a load-sensitive mechanical precise control hydraulic system is provided, including: a piston pump, which is a load-sensitive constant power piston pump and has an LS control oil port;

[0005] A load-sensitive main valve, whose LS oil port is communicated with the LS control oil port of the piston pump;

[0006] An LS solenoid valve, whose oil inlet A is communicated with the LS oil port of the load-sensitive main valve, and the oil outlet B is communicated with the LS control oil port of the piston pump;

[0007] A throttle orifice c, integrated inside the LS solenoid valve, communicating the oil inlet A and the oil outlet B of the LS solenoid valve;

[0008] Wherein, when the LS solenoid valve is powered off, it is directly connected, and PA = PB; when it is powered on, the throttle orifice c is conducted, and PA > PB.

[0009] In this technical solution, the LS solenoid valve is in a normally closed state. The opening and closing of the LS solenoid valve are controlled by an electrical signal.

[0010] According to the present invention, further, when the LS solenoid valve is in the powered-off state, the oil inlet A and the oil outlet B are directly connected, and the load pressure signal is transmitted to the piston pump without attenuation.

[0011] According to the present invention, further, when the LS solenoid valve is in the powered-on state, the load pressure signal is transmitted to the piston pump after attenuation through the throttle orifice c, and the output flow rate of the piston pump decreases.

[0012] According to the present invention, further, the aperture of the throttle hole c is 0.8 mm - 1.0 mm, and the flow rate is less than that in the normal mode.

[0013] According to the present invention, further, the load-sensing main valve is connected to an oil cylinder.

[0014] According to the present invention, further, the hydraulic oil tank is connected to the plunger pump and the load-sensing main valve through a hydraulic output pipeline to form a communicating oil circuit.

[0015] According to the present invention, further, the hydraulic oil tank is connected to the oil return port T of the load-sensing main valve through a hydraulic oil circuit, and a radiator is provided on the second hydraulic output pipeline to adjust the temperature of the hydraulic oil returning to the hydraulic oil tank 5.

[0016] When the wheel loader starts, the fast-slow control rocker switch is in the fast-closed state, and at the same time, the LS solenoid valve is in the normally closed state. When the whole machine is working at the excavation end, each control action is not affected by the LS solenoid valve and is in the optimal state. When the whole machine performs precise operation, the fast-slow control rocker switch is opened in advance, and each control action of the whole machine will become slower when working under heavy load conditions, so as to smoothly complete the precise operation. When the whole machine needs normal control, just close the fast-slow control rocker switch.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention adopts the above structure and has the characteristics of simple structure, good processability, strong versatility and convenient use.

[0019] The present invention controls the on-off of the LS solenoid valve through a rocker switch: when powered off, the LS oil circuit is directly connected, and the system is in the normal operation mode; when powered on, the load signal is attenuated and transmitted to the plunger pump through the throttle hole, so that its output flow rate is reduced, and it is switched to the precise operation mode. It solves the problem that the existing load-sensing system cannot adapt to the precise loading and unloading working conditions, and has the advantages of one-key switching, simple structure and strong compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a load-sensing mechanical precise control hydraulic system of the present invention.

[0021] In the figure: 1 - plunger pump, 2 - LS solenoid valve, 3 - load-sensing main valve, 4 - oil cylinder, 5 - oil tank, 51 - hydraulic output pipeline, 52 - hydraulic oil circuit, 6 - radiator, c - throttle hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] This invention provides a load-sensing mechanical precision control hydraulic system, primarily used on backhoe loaders. It comprises a load-sensing constant-power plunger pump 1 and a connected load-sensing main valve 3. The LS oil port of the load-sensing main valve 3 is connected to the LS control oil port of the plunger pump 1 via a hydraulic pipeline. The load-sensing main valve 3 is connected to a hydraulic cylinder 4. A hydraulic oil tank 5 is connected to the plunger pump 1 and the load-sensing main valve 3 via a hydraulic output pipeline 51, forming a connecting oil circuit.

[0024] Furthermore, the system includes an LS solenoid valve 2, whose oil inlet A is connected to the LS oil port of the load-sensing main valve 3, and whose oil outlet B is connected to the LS control oil port of the plunger pump 1. A throttle orifice c is provided within the LS solenoid valve 2, and a bypass throttle orifice c connects the oil inlet A and oil outlet B of the LS solenoid valve 2. A speed control rocker switch electrically connected to the LS solenoid valve 2 controls the on and off of the LS solenoid valve 2. The speed control rocker switch is an existing component and will not be described in detail here.

[0025] Specifically, LS solenoid valve 2 is a two-position, two-way valve. When de-energized, it flows directly through (PA = PB). When energized, orifice c is open (PA > PB). When de-energized, LS solenoid valve 2 connects its oil inlet A and oil outlet B, allowing the load pressure signal to be transmitted to plunger pump 1 without attenuation. When energized, the load pressure signal is attenuated by orifice c before being transmitted to plunger pump 1, reducing the output flow rate of plunger pump 1. Preferably, the orifice c has a diameter of 0.8mm-1.0mm to ensure linear flow rate attenuation, allowing the flow rate in precision operation mode to be 60%-80% of that in normal mode.

[0026] In the embodiment of the present application, the hydraulic oil tank 5 is connected to the return oil port T of the load-sensing main valve 3 through a hydraulic oil circuit 52 , and a radiator 6 is provided on the second hydraulic output pipeline 52 to adjust the temperature of the hydraulic oil returned to the hydraulic oil tank 5 .

[0027] The operating principle of this invention is as follows: After the backhoe loader is started, the electromagnet of LS solenoid valve 2 is de-energized. When the load-sensing main valve 3 is operated, a load signal is transmitted through its LS port to the LS solenoid valve 2's oil inlet A. This signal is then transmitted through LS solenoid valve 2's oil outlet B to the LS control port of the load-sensing constant-power plunger pump 1, thereby controlling the pump swash plate opening. In this state, the pressure PA at LS solenoid valve 2's oil inlet A and oil outlet B is equal to PB, and the LS solenoid valve 2 has virtually no effect on the hydraulic system.

[0028] When precise operation is required after the backhoe loader starts and the electromagnet of the LS solenoid valve 2 is energized, the LS solenoid valve 2 is in the position-changing state. When the load-sensing main valve 3 operates, the load signal is transmitted to the oil inlet A of the LS solenoid valve 2 through its LS oil port. Since the LS solenoid valve 2 is in the spool a position, the load position number of the oil inlet A of the LS solenoid valve 2 is transmitted to the oil outlet B through the throttle orifice c of the LS solenoid valve 2. The oil outlet B of the LS solenoid valve 2 is transmitted to the LS control oil port of the load-sensing constant-power piston pump 1, thereby controlling the opening size of the pump swash plate. In this state, since the hydraulic oil flows out from the oil outlet B through the throttle orifice c via the oil inlet A, the pressure PA of the oil inlet A and the oil outlet B of the LS solenoid valve 2 is greater than PB. Since the piston pump 1 is a constant-power load-sensing variable pump, when the piston pump 1 detects a falsely high pressure PB, which is higher than the normal state, the swash plate angle decreases. According to the principle that the flow rate of the constant-power pump decreases as the pressure increases, at this time, the power control cylinder 4 of the piston pump 1 reduces the pump swash plate angle, so that the flow rate provided by the piston pump 1 to the load-sensing main valve 3 decreases, thereby achieving precise operation.

[0029] When normal operation is to be achieved after the backhoe loader starts, it is only necessary for the electromagnet of the LS solenoid valve 2 to be de-energized.

[0030] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A load-sensitive mechanical precision control hydraulic system, characterized in that, include: The plunger pump is a load-sensitive constant-power plunger pump with an LS control oil port; The LS oil port of the load-sensing main valve is connected to the LS control oil port of the plunger pump; LS solenoid valve, its oil inlet A is connected to the LS oil port of the load sensing main valve, and its oil outlet B is connected to the LS control oil port of the plunger pump; The throttle hole c is integrated inside the LS solenoid valve and connects the oil inlet A and the oil outlet B of the LS solenoid valve; Among them, when the LS solenoid valve is powered off, it is directly connected, PA=PB; when powered on, the throttle hole c is connected, PA>PB.

2. The load-sensitive mechanical precision control hydraulic system according to claim 1, wherein: When the LS solenoid valve is in a power-off state, the oil inlet A and the oil outlet B are directly connected, and the load pressure signal is transmitted to the plunger pump without attenuation.

3. A load-sensitive mechanical precision control hydraulic system according to claim 1, characterized in that: When the LS solenoid valve is energized, the load pressure signal is attenuated through the throttle hole c and then transmitted to the plunger pump, and the output flow of the plunger pump is reduced.

4. The load-sensitive mechanical precision control hydraulic system according to claim 1, characterized in that, The aperture of the throttle hole c is 0.8 mm to 1.0 mm, and the flow rate is smaller than that in the normal mode.

5. A load-sensitive mechanical precision control hydraulic system according to claim 1, characterized in that, The load-sensing main valve is connected to an oil cylinder.

6. The load-sensitive mechanical precision control hydraulic system according to claim 5, characterized in that The hydraulic oil tank is connected to the plunger pump and the load-sensing main valve through a hydraulic output pipeline to form a communicating oil circuit.

7. The load-sensitive mechanical precision control hydraulic system according to claim 6, characterized in that, The hydraulic oil tank is connected to the oil return port T of the load-sensing main valve through a hydraulic oil circuit. A radiator is provided on the second hydraulic output pipeline to adjust the temperature of the hydraulic oil returned to the hydraulic oil tank 5.

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