阅读说明：本技术 一种负载敏感液压系统、绿篱修剪设备 (Load-sensitive hydraulic system and hedge trimming equipment ) 是由 刘振 曾建国 覃先云 刘伯祥 丁伟 于 2021-01-21 设计创作，主要内容包括：本发明公开了一种负载敏感液压系统、绿篱修剪设备,所述液压系统包括割刀马达控制阀组、臂架控制阀组,所述割刀马达控制阀组包括主定压差阀、第一电磁换向阀、第二电磁换向阀、二通流量阀,所述臂架控制阀组包括至少一组定压差阀和电比例换节阀。本发明一方面通过PWM信号即可决定各液压执行件的流量而不随负载变化；另一方面,当绿篱修剪装置修剪绿篱遇到障碍时,液压油将优先流向驱动臂架及刀盘旋转机构运动的液压执行件快速响应调整姿态,多余流量通过主定压差阀流向割刀马达机构进行减速修剪,从而使绿篱修剪设备避障响应快且割刀马达机构一直工作不会留下大片绿篱待人工二次修剪,避障更安全可靠、作业效率更高,且有效预防液压系统过载。(The invention discloses a load-sensitive hydraulic system and hedge trimming equipment, wherein the hydraulic system comprises a cutting knife motor control valve group and a boom control valve group, the cutting knife motor control valve group comprises a main constant pressure difference valve, a first electromagnetic reversing valve, a second electromagnetic reversing valve and a two-way flow valve, and the boom control valve group comprises at least one group of constant pressure difference valves and an electric proportional change valve. On one hand, the flow of each hydraulic actuating element can be determined through the PWM signal without changing along with the load; on the other hand, when the hedgerow trimming device trims the hedgerow and meets an obstacle, hydraulic oil flows to the hydraulic execution part which drives the arm support and the cutter head rotating mechanism to move preferentially to respond quickly to adjust the posture, redundant flow flows to the cutter motor mechanism through the main constant pressure difference valve to perform deceleration trimming, accordingly, the hedgerow trimming device is quick in obstacle avoidance response, the cutter motor mechanism works all the time, large hedgerows of hedgerows cannot be left to be trimmed manually for the second time, obstacle avoidance is safer and more reliable, the operation efficiency is higher, and overload of a hydraulic system is effectively prevented.)

1. The utility model provides a sensitive hydraulic system of load, includes cutting knife motor valve unit (72), cantilever crane valve unit (73), its characterized in that:

the cutting knife motor control valve group (72) comprises a main constant pressure difference valve (722), a first electromagnetic directional valve (723), a second electromagnetic directional valve (724) and a two-way flow valve (725), wherein the input end of the main constant pressure difference valve (722) is connected with an oil pump (704), the output end of the main constant pressure difference valve is connected with a P port of the second electromagnetic directional valve (724), the P port of the first electromagnetic directional valve (723) is connected with the output end of the main constant pressure difference valve (722), the T port is communicated with an oil tank (701) through an oil return pipe, the spring end of the main constant pressure difference valve (722) is provided with an LS pressure induction port, and the LS pressure induction port is connected with the output end of the main constant pressure difference valve (722) through the two-way flow valve (725); the port A and the port B of the second electromagnetic directional valve (724) are connected with a cutting knife motor mechanism, and the port T is communicated with an oil tank (701) through a pipeline;

the boom control valve group (73) comprises at least one group of constant pressure differential valve and an electric proportional change valve, a P0 port and a T port of the electric proportional change valve are respectively connected with an oil pump (704) and an oil tank (701), an A port and a B port of the electric proportional change valve are respectively connected with a hydraulic executive part for driving the boom and the cutter head rotating mechanism to move, an outlet of a flow sensing port of the electric proportional change valve is connected with the P port of the constant pressure differential valve, the T port of the constant pressure differential valve is connected with a P1 port of the electric proportional change valve through a one-way valve, and when the electric proportional change valve is in a left working position and a right working position, the P1 port of the electric proportional change valve is communicated with the A port or the B port; the LS pressure sensing port of the constant pressure differential valve is connected with the LS pressure sensing port of the main constant pressure differential valve (722) through a load sensing pipeline and used for controlling the pressure difference of the flow sensing ports of the corresponding electric proportional change valves to be constant and screening out the maximum change valve flow sensing port outlet pressure to act on the LS pressure sensing port of the main constant pressure differential valve (722) through the load sensing pipeline.

2. The load-sensitive hydraulic system according to claim 1, wherein the constant pressure differential valve is a three-position three-way constant pressure differential valve without a regulating spring, one side of the constant pressure differential valve is provided with an LS pressure sensing port and a T port, the other side of the constant pressure differential valve is provided with a P port, one end of the constant pressure differential valve is provided with a first spool control port for guiding pressure oil in the LS pressure sensing port to push the spool to move, the other end of the constant pressure differential valve is provided with a second spool control port for guiding pressure oil in an outlet of the flow sensing port of the electric proportional change valve to push the spool to move reversely, when no pressure oil exists in the outlet of the flow sensing port of the electric proportional change valve, the spool of the constant pressure differential valve is in a first position, and at the time, the P port, the T port and the LS pressure sensing port of the constant pressure differential valve are all in a stop state, and when an oil pressure in the outlet of the flow sensing port of the electric proportional, the valve core of the constant pressure differential valve is positioned at a second position, and pressure oil entering the port P of the constant pressure differential valve flows into the port T of the constant pressure differential valve after being throttled; when the oil pressure at the outlet of the flow sensing port of the electric proportional throttling valve reaches a set threshold value b, b is greater than a, one part of the pressure oil entering the P port of the constant differential pressure valve flows into the LS pressure sensing port of the constant differential pressure valve after being throttled, and the other part of the pressure oil flows into the T port of the constant differential pressure valve.

3. The load-sensitive hydraulic system according to claim 2, wherein the electro proportional change valve is a three-position seven-way electro proportional change valve, one side of the electro proportional change valve is provided with a port P0, a port P1 and a port T, the other side of the electro proportional change valve is provided with a port A, a port B and two merged flow induction port outlets, when a valve core of the electro proportional change valve is at a middle position, the two merged flow induction port outlets, the port P0 and the port P1 are all in a stop state, and the port A, the port B and the port T are communicated; when the valve core of the electric proportional change valve moves to the left side position, pressure oil entering a port P0 of the electric proportional change valve flows into an outlet of a flow sensing port, a port P of a constant pressure difference valve, a port T of the constant pressure difference valve, a port P1 of the electric proportional change valve, a port A of the electric proportional change valve, a hydraulic actuating part for driving a boom and a cutter head rotating mechanism to move and a port B of the electric proportional change valve after being throttled, and finally flows back to an oil tank (701) after entering the port T of the electric proportional change valve; when the valve core of the electric proportional change valve moves to the right position, pressure oil entering the port P0 of the electric proportional change valve flows into the outlet of the flow sensing port, the port P of the constant pressure difference valve, the port T of the constant pressure difference valve, the port P1 of the electric proportional change valve, the port B of the electric proportional change valve, the hydraulic actuating part for driving the arm support and the cutter head rotating mechanism to move and the port A of the electric proportional change valve in sequence after throttling, and finally flows back to the oil tank (701) after flowing into the port T of the electric proportional change valve after throttling.

4. The load sensitive hydraulic system of claim 3,

the boom control valve group (73) comprises: a first constant pressure difference valve (732), a second constant pressure difference valve (734), a third constant pressure difference valve (736), a fourth constant pressure difference valve (738), a first electric proportional change valve (731), a second electric proportional change valve (733), a third electric proportional change valve (735), and a fourth electric proportional change valve (737), wherein the first constant pressure difference valve (732) is connected with the first electric proportional change valve (731), the second constant pressure difference valve (734) is connected with the second electric proportional change valve (733), the third constant pressure difference valve (736) is connected with the third electric proportional change valve (735), the fourth constant pressure difference valve (738) is connected with the fourth electric proportional change valve (737), the A port and the B port of the fourth electric proportional change valve (737) are connected with a cutter head rotating motor (708), the A port and the B port of the third electric proportional change valve (735) are connected with a third arm cylinder (707), an opening A and an opening B of the second electric proportional change valve (733) are connected with a second-joint arm oil cylinder (706), an opening A and an opening B of the first electric proportional change valve (731) are connected with a main arm oil cylinder (705), and LS pressure sensing openings of the first constant pressure difference valve (732), the second constant pressure difference valve (734), the third constant pressure difference valve (736) and the fourth constant pressure difference valve (738) are connected in parallel and then communicated with an LS pressure sensing opening of the main constant pressure difference valve (722).

5. The load sensitive hydraulic system of claim 4,

a first bidirectional balance valve (710) and a second bidirectional balance valve (711) are respectively arranged between oil inlets and oil outlets of the two-section arm oil cylinder (706) and the three-section arm oil cylinder (707), and a first balance valve (709) is arranged between the oil inlets and the oil outlets of the main arm oil cylinder (705).

6. The load sensitive hydraulic system of claim 2,

a pressure difference delta p between the input end of the main constant pressure difference valve (722) and the LS pressure sensing port of the main constant pressure difference valve (722)_D00.5 to 1 MPa.

7. The load sensitive hydraulic system of claim 1,

second electromagnetic directional valve (724) are two cross valves, and are provided with two-way overflow valve (713) between its A mouth and the B mouth, wherein, if A mouth or B mouth are the oil return opening, still be provided with on the pipeline between A mouth and two-way overflow valve (713) or between B mouth and two-way overflow valve (713) and prevent that motor reversal and oil return backpressure from causing check valve (714) of influence to the motor.

8. The load sensitive hydraulic system of claim 1 or 7,

the cutting knife motor mechanism comprises at least two sequentially cascaded cutting knife motors, and overflow valves are arranged at oil inlets of all the other cutting knife motors except the first-stage cutting knife motor.

9. The load sensitive hydraulic system of claim 1,

the cutting knife motor control valve group (72) further comprises an LS overflow valve (726), the input end of the LS overflow valve (726) is connected with an LS pressure sensing opening of the main constant pressure difference valve (722) in a bypassing mode, and the output end of the LS overflow valve is connected with the oil tank (701).

10. A hedge trimming apparatus comprising a load sensitive hydraulic system according to any one of claims 1 to 9.

Technical Field

The invention relates to the field of hydraulic control, in particular to a load-sensitive hydraulic system and hedge trimming equipment.

Background

In consideration of cost and structure simplification, a single-pump system adopted by most of existing environment-friendly equipment for hedge trimming, guardrail cleaning and the like is characterized in that an oil pump supplies oil to a knuckle arm and a cutter motor, so that when the equipment avoids an obstacle, the attitude of the knuckle arm can only be adjusted firstly, then the cutter motor is started, and if the attitude of the knuckle arm and the rotation of the cutter motor are started simultaneously, the cutter motor is overloaded, so that the equipment is slow in obstacle avoidance response and low in reliability, and a large area to be processed is left due to the fact that the cutter motor stops rotating when the attitude of the knuckle arm is adjusted easily to be manually processed for secondary processing, so that the operation intensity of workers is increased, and the operation efficiency is seriously affected.

Disclosure of Invention

The invention provides a load-sensitive hydraulic system, which aims to solve the problems that the existing environment-friendly equipment is slow in obstacle avoidance response and low in reliability, increases the working intensity of workers and is low in working efficiency.

The technical scheme adopted by the invention is as follows:

a load-sensitive hydraulic system comprises a cutting knife motor control valve group and an arm support control valve group, wherein the cutting knife motor control valve group comprises a main constant pressure difference valve, a first electromagnetic directional valve, a second electromagnetic directional valve and a two-way flow valve, the input end of the main constant pressure difference valve is connected with an oil pump, the output end of the main constant pressure difference valve is connected with a P port of the second electromagnetic directional valve, the P port of the first electromagnetic directional valve is connected with the output end of the main constant pressure difference valve, the T port is communicated with an oil tank through an oil return pipe, the spring end of the main constant pressure difference valve is provided with an LS pressure induction port, and the LS pressure induction port is connected with the output end of the main constant pressure difference valve through the two-way flow valve; the port A and the port B of the second electromagnetic directional valve are connected with a cutting knife motor mechanism, and the port T is communicated with an oil tank through a pipeline;

the boom control valve group comprises at least one group of constant pressure differential valve and an electric proportional change valve, a P0 port and a T port of the electric proportional change valve are respectively connected with an oil pump and an oil tank, an A port and a B port of the electric proportional change valve are respectively connected with a hydraulic actuator for driving the boom and the cutter head rotating mechanism to move, an outlet of a flow sensing port of the electric proportional change valve is connected with the P port of the constant pressure differential valve, the T port of the constant pressure differential valve is connected with a P1 port of the electric proportional change valve through a one-way valve, and when the electric proportional change valve is in a left working position and a right working position, the P1 port of the electric proportional change valve is communicated with the A port or the B port; the LS pressure sensing port of the constant pressure differential valve is connected with the LS pressure sensing port of the main constant pressure differential valve through a load sensing pipeline and used for controlling the pressure difference of the flow sensing ports of the corresponding electric proportional throttling valves to be constant and screening out the maximum pressure at the outlet of the flow sensing port of the throttling valve to act on the LS pressure sensing port of the main constant pressure differential valve through the load sensing pipeline.

Furthermore, the constant pressure differential valve is a three-position three-way constant pressure differential valve and is not provided with an adjusting spring, one side of the constant pressure differential valve is provided with an LS pressure induction port and a T port, the other side is provided with a P port, one end of the constant pressure difference valve is provided with a first valve core control port for guiding pressure oil of the LS pressure sensing port to push the valve core to move, the other end of the constant pressure difference valve is provided with a second valve core control port for guiding pressure oil of the flow sensing port outlet of the electric proportional change valve to push the valve core to move reversely, when the outlet of the flow sensing port of the electric proportional throttling valve has no pressure oil, the valve core of the constant pressure differential valve is in a first position, and the P port, the T port and the LS pressure sensing port of the constant pressure differential valve are all in a cut-off state, when the oil pressure at the outlet of the flow sensing port of the electric proportional throttling valve reaches a set threshold value a, the valve core of the constant pressure differential valve is in a second position, and the pressure oil entering the P port of the constant pressure differential valve flows into the T port of the constant pressure differential valve after being throttled; when the oil pressure at the outlet of the flow sensing port of the electric proportional throttling valve reaches a set threshold value b, b is greater than a, one part of the pressure oil entering the P port of the constant differential pressure valve flows into the LS pressure sensing port of the constant differential pressure valve after being throttled, and the other part of the pressure oil flows into the T port of the constant differential pressure valve.

Furthermore, the electric proportional change valve is a three-position seven-way electric proportional change valve, one side of the electric proportional change valve is provided with a P0 port, a P1 port and a T port, the other side of the electric proportional change valve is provided with an A port, a B port and two converged flow induction port outlets, when a valve core of the electric proportional change valve is in a middle position, the two converged flow induction port outlets, the P0 port and the P1 port are all in a stop state, and the A port, the B port and the T port are communicated; when the valve core of the electric proportional change valve moves to the left side position, pressure oil entering the port P0 of the electric proportional change valve flows into the outlet of the flow sensing port, the port P of the constant pressure difference valve, the port T of the constant pressure difference valve, the port P1 of the electric proportional change valve, the port A of the electric proportional change valve, a hydraulic actuating part for driving the arm support and the cutter head rotating mechanism to move and the port B of the electric proportional change valve in sequence after being throttled, and finally flows back to the oil tank after entering the port T of the electric proportional change valve; when the valve core of the electric proportional change valve moves to the right position, the pressure oil entering the port P0 of the electric proportional change valve flows into the outlet of the flow sensing port, the port P of the constant pressure difference valve, the port T of the constant pressure difference valve, the port P1 of the electric proportional change valve, the port B of the electric proportional change valve, the hydraulic actuating part for driving the arm support and the cutter head rotating mechanism to move and the port A of the electric proportional change valve in sequence after throttling, and finally flows back to the oil tank after throttling and entering the port T of the electric proportional change valve.

Further, the boom control valve group includes: the hydraulic control system comprises a first constant pressure differential valve, a second constant pressure differential valve, a third constant pressure differential valve, a fourth constant pressure differential valve, a first electric proportional change valve, a second electric proportional change valve, a third electric proportional change valve and a fourth electric proportional change valve, wherein the first constant pressure differential valve is connected with the first electric proportional change valve, the second constant pressure differential valve is connected with the second electric proportional change valve, the third constant pressure differential valve is connected with the third electric proportional change valve, the fourth constant pressure differential valve is connected with the fourth electric proportional change valve, an A port and a B port of the fourth electric proportional change valve are connected with a cutter disc rotating motor, an A port and a B port of the third electric proportional change valve are connected with a three-joint-arm oil cylinder, an A port and a B port of the second electric proportional change valve are connected with a two-joint-arm oil cylinder, an A port and a B port of the first electric proportional change valve are connected with an oil cylinder, and the first constant pressure differential valve and the second constant pressure differential valve are connected with a main arm oil cylinder, LS pressure sensing ports of the third constant pressure difference valve and the fourth constant pressure difference valve are connected in parallel and then communicated with the LS pressure sensing port of the main constant pressure difference valve.

Furthermore, a first bidirectional balance valve and a second bidirectional balance valve are respectively arranged between the oil inlet and the oil outlet of the two-section arm oil cylinder and between the oil inlet and the oil outlet of the three-section arm oil cylinder, and a first balance valve is arranged between the oil inlet and the oil outlet of the main arm oil cylinder.

Further, the pressure difference between the input end of the main constant pressure difference valve and the LS pressure sensing port of the main constant pressure difference valve is 0.5-1 Mpa.

Further, the second electromagnetic directional valve is two cross valves, and is provided with the two-way overflow valve between its A mouth and the B mouth, wherein, if A mouth or B mouth are the oil return opening, still be provided with the check valve that prevents that motor reversal and oil return backpressure from causing the influence to the motor on the pipeline between A mouth and the two-way overflow valve, or between B mouth and the two-way overflow valve.

Furthermore, the cutting knife motor mechanism comprises at least two sequentially cascaded cutting knife motors, and overflow valves are arranged at oil inlets of all the other cutting knife motors except the first-stage cutting knife motor.

Furthermore, the cutting knife motor control valve group also comprises an LS overflow valve, the input end of the LS overflow valve is connected with the LS pressure induction port of the main constant pressure difference valve in a side-by-side mode, and the output end of the LS overflow valve is connected with the oil tank.

In another aspect, the invention also provides hedge trimming equipment comprising the load sensitive hydraulic system.

The invention has the following beneficial effects:

in the load-sensitive hydraulic system provided by the invention, the LS pressure sensing port of the constant pressure differential valve is connected with the LS pressure sensing port of the main constant pressure differential valve through a load-sensitive pipeline, so that the pressure difference of the flow sensing ports of the corresponding electric proportional throttle valves is controlled to be constant, the outlet pressure of the flow sensing port of the maximum throttle valve is screened out from the pressure difference, and the outlet pressure acts on the LS pressure sensing port of the main constant pressure differential valve through the load-sensitive pipeline; on the other hand, once the hydraulic executive component for driving the arm support and the cutter head rotating mechanism to move works, the invention can reduce the flow of hydraulic oil flowing into the cutting knife motor mechanism by applying the maximum flow induction port outlet pressure of the node changing valve to the LS pressure induction port of the main constant pressure differential valve through the load sensitive pipeline to push the valve core of the main constant pressure differential valve to move, when the pump flow is constant, the invention preferably supplies oil to the hydraulic executive component for driving the arm support and the cutter head rotating mechanism to move, namely when the hedge trimming device trims hedges against obstacles, the arm support actively avoids the obstacles, the first electromagnetic directional valve, the second electromagnetic directional valve and the electric proportional node changing valve are simultaneously electrified, the flow of the oil pump preferentially flows to the hydraulic executive component for driving the arm support and the cutter head rotating mechanism to move, the redundant flow flows to the cutting knife motor mechanism through the main constant pressure differential valve, and at the moment, the arm support and the cutter, meanwhile, the cutting knife motor mechanism is decelerated but does not stop rotating, so that the obstacle avoidance response of the hedge trimming equipment is fast, large hedges cannot be left when the cutting knife motor mechanism works all the time, and manual secondary trimming is needed.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic diagram of the load sensitive hydraulic system configuration of the preferred embodiment of the present invention.

Fig. 2 is a schematic view of the hedge trimming apparatus according to the preferred embodiment of the present invention.

Fig. 3 is a block diagram of the hydraulic transmission and control principle of the hedge trimming apparatus according to the preferred embodiment of the present invention.

Fig. 4 is a schematic structural view of the guardrail cleaning device according to the preferred embodiment of the invention.

In the figure: 1. a base; 2. a main arm; 3. a two-section arm; 4. a three-section arm; 5. a cutter head; 6. a cutter disc slewing mechanism;

7. a load-sensitive hydraulic system;

701. an oil tank; 702. an oil absorption filter; 703. a ball valve; 704. an oil pump; 705. a main arm cylinder; 706. a two-section arm cylinder; 707. three-section arm oil cylinder; 708. a cutter head rotating motor; 709. a first counter-balance valve; 710. a first bidirectional balancing valve; 711. a second bidirectional balancing valve; 712. an oil return filter; 713. a two-way relief valve; 714. a one-way valve; 715. a first overflow valve; 716. a second overflow valve; 717. a first cutter motor; 718. a second cutter motor; 719. a third cutter motor; 720. an air cleaner; 72. a cutting knife motor control valve group; 721. a main overflow valve; 722. a primary constant differential pressure valve; 723. a first electromagnetic directional valve; 724. a second electromagnetic directional valve; 725. a two-way flow valve; 726. an LS overflow valve; 73. a boom control valve group; 731. a first electrical proportional change valve; 732. a first constant differential pressure valve; 733. a second electrical proportional change valve; 734. a second constant differential pressure valve; 735. a third electric proportional change valve; 736. a third constant differential pressure valve; 737. a fourth electric proportional change valve; 738. a fourth constant differential pressure valve; 8. an electrical component; 801. a first tilt sensor; 802. a first tilt sensor; 803. a third tilt sensor; 804. a cutter head rotary encoder; 9. and (4) cleaning brushes.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As shown in fig. 1, a preferred embodiment of the present invention provides a load-sensitive hydraulic system, which includes a cutting knife motor control valve group 72 and a boom control valve group 73, where the cutting knife motor control valve group 72 includes a main constant pressure differential valve 722, a first electromagnetic directional valve 723, a second electromagnetic directional valve 724, and a two-way flow valve 725, an input end of the main constant pressure differential valve 722 is connected to an oil pump 704, an output end of the main constant pressure differential valve 722 is connected to a port P of the second electromagnetic directional valve 724, a port P of the first electromagnetic directional valve 723 is connected to an output end of the main constant pressure differential valve 722, the port T is communicated to an oil tank 701 through an oil return pipe, a spring end of the main constant pressure differential valve 722 is provided with an LS pressure sensing port, and the LS pressure sensing port is connected to an output end of the main constant pressure differential valve 722 through the two-; the port A and the port B of the second electromagnetic directional valve 724 are connected with a cutting knife motor mechanism, and the port T is communicated with the oil tank 701 through a pipeline;

the boom control valve group 73 comprises at least one group of constant pressure differential valve and an electric proportional change valve, a P0 port and a T port of the electric proportional change valve are respectively connected with the oil pump 704 and the oil tank 701, an A port and a B port of the electric proportional change valve are respectively connected with a hydraulic executive part for driving the boom and the cutter head rotating mechanism to move, an outlet of a flow sensing port of the electric proportional change valve is connected with the P port of the constant pressure differential valve, the T port of the constant pressure differential valve is connected with a P1 port of the electric proportional change valve through a one-way valve, and when the electric proportional change valve is in a left working position and a right working position, the P1 port of the electric proportional change valve is communicated with the A port or the B port; the LS pressure sensing port of the constant pressure differential valve is connected with the LS pressure sensing port of the main constant pressure differential valve 722 through a load sensing pipeline and is used for controlling the pressure difference of the flow sensing ports of the corresponding electric proportional throttling valves to be constant and screening out the maximum outlet pressure of the flow sensing ports of the throttling valves to act on the LS pressure sensing ports of the main constant pressure differential valve 722 through the load sensing pipeline.

The load-sensitive hydraulic system provided by the embodiment comprises a cutting knife motor control valve group 72 and a boom control valve group 73, wherein the cutting knife motor control valve group 72 comprises a main constant pressure difference valve 722, a first electromagnetic directional valve 723, a second electromagnetic directional valve 724 and a two-way flow valve 725, and the boom control valve group 73 comprises at least one set of constant pressure difference valve and an electric proportional throttle valve. In addition, the hydraulic system of this embodiment further includes a main overflow valve 721, the input end of the oil pump 704 is sequentially connected to a ball valve 703 and an oil suction filter 702, an oil return filter 712 is disposed on the oil return pipe, and an air cleaner 720 is further disposed on the oil tank 701. The LS pressure sensing port of the constant pressure differential valve is connected with the LS pressure sensing port of the main constant pressure differential valve 722 through a load sensing pipeline, so that the pressure difference of the flow sensing ports of the corresponding electric proportional throttle valves is controlled to be constant, the maximum throttle valve flow sensing port pressure is screened out from the pressure, and the maximum throttle valve flow sensing port pressure acts on the LS pressure sensing port of the main constant pressure differential valve 722 through the load sensing pipeline; on the other hand, once the hydraulic actuator for driving the boom and cutter head rotation mechanism to move operates, the embodiment can push the spool of the main constant pressure differential valve 722 to move by applying the maximum outlet pressure of the flow sensing port of the node-changing valve to the LS pressure sensing port of the main constant pressure differential valve 722 through the load-sensitive pipeline, so that when the pump flow is constant, the flow of the hydraulic oil flowing into the cutter motor mechanism can be reduced, preferably, the hydraulic actuator for driving the boom and cutter head rotation mechanism to move is supplied with oil, i.e. when the hedge trimming device trims a hedge and encounters an obstacle, the boom is actively avoided, the first electromagnetic directional valve 723, the second electromagnetic directional valve 724 and the electric proportional node-changing valve are simultaneously powered on, the flow of the oil pump 704 will preferentially flow to the hydraulic actuator for driving the boom and cutter head rotation mechanism to move, and the surplus flow flows to the cutter head motor mechanism through the main constant pressure differential valve 722, at this time, meanwhile, the cutting knife motor mechanism is decelerated but does not stop rotating, so that the obstacle avoidance response of the hedge trimming equipment is fast, large hedges cannot be left when the cutting knife motor mechanism works all the time, and manual secondary trimming is needed.

In a preferred embodiment of the invention, the constant pressure differential valve is a three-position three-way constant pressure differential valve and is not provided with an adjusting spring, one side of the constant pressure differential valve is provided with an LS pressure sensing port and a T port, the other side of the constant pressure differential valve is provided with a P port, one end of the constant pressure differential valve is provided with a first valve core control port for guiding pressure oil of the LS pressure sensing port to push a valve core to move, the other end of the constant pressure differential valve is provided with a second valve core control port for guiding pressure oil of an outlet of a flow sensing port of the electric proportional pressure change valve to push the valve core to move reversely, when no pressure oil exists at the outlet of the flow sensing port of the electric proportional pressure change valve, the valve core of the constant pressure differential valve is at a first position, at the moment, the P port, the T port and the LS pressure sensing port of the constant pressure differential valve are all in a stop state, when the oil pressure at the outlet of the flow sensing port of the electric, the pressure oil entering the port P of the constant pressure difference valve flows into the port T of the constant pressure difference valve after being throttled; when the oil pressure at the outlet of the flow sensing port of the electric proportional throttling valve reaches a set threshold value b, b is greater than a, one part of the pressure oil entering the P port of the constant differential pressure valve flows into the LS pressure sensing port of the constant differential pressure valve after being throttled, and the other part of the pressure oil flows into the T port of the constant differential pressure valve.

In a preferred embodiment of the invention, the electric proportional change valve is a three-position seven-way electric proportional change valve, one side of the electric proportional change valve is provided with a port P0, a port P1 and a port T, the other side of the electric proportional change valve is provided with a port A, a port B and two merged flow induction port outlets, when a valve core of the electric proportional change valve is in a middle position, the two merged flow induction port outlets, the port P0 and the port P1 are all in a stop state, and the port A, the port B and the port T are communicated; when the valve core of the electric proportional change valve moves to the left position, pressure oil entering the port P0 of the electric proportional change valve flows into the outlet of the flow sensing port, the port P of the constant pressure difference valve, the port T of the constant pressure difference valve, the port P1 of the electric proportional change valve, the port A of the electric proportional change valve, a hydraulic actuating element for driving the arm support and the cutter head rotating mechanism to move and the port B of the electric proportional change valve after being throttled, and finally flows back to the oil tank 701 through the port T of the electric proportional change valve after being throttled; when the valve core of the electric proportional change valve moves to the right position, pressure oil entering the port P of the electric proportional change valve flows into the outlet of the flow sensing port, the port P0 of the constant pressure difference valve, the port T of the constant pressure difference valve, the port P1 of the electric proportional change valve, the port B of the electric proportional change valve, the hydraulic actuator for driving the arm support and the cutter head rotating mechanism to move and the port A of the electric proportional change valve in sequence after being throttled, and finally flows back to the oil tank 701 after being throttled and entering the port T of the electric proportional change valve.

In this embodiment, the pressure flowing into the port P0 of the electric proportional change valve does not immediately flow into the ports a and B, but flows into the port P1 of the electric proportional change valve after passing through the constant pressure differential valve, then flows into the ports a and B, and the hydraulic oil flowing into the constant pressure differential valve is also guided into the LS pressure sensing port of the constant pressure differential valve, and then feeds the pressure back to the LS pressure sensing port of the main constant pressure differential valve 722 to drive the spool of the main constant pressure differential valve 722 to move, so as to reduce the flow rate of the hydraulic oil flowing into the cutter motor mechanism, which performs deceleration operation, so that most of the hydraulic oil preferably flows into the hydraulic actuators driving the arm support and the cutter head rotation mechanism to move, thereby achieving obstacle avoidance. In the embodiment, all the pressure oil entering the port P0 of the electric proportional throttle valve is led into the constant pressure differential valve and then flows into the port A and the port B after returning to the port P1, the flow sensing port is arranged in front of the constant pressure differential valve, and the reversing function is arranged behind the constant pressure differential valve, so that only one constant pressure differential valve is needed for each electric proportional throttle valve.

In a preferred embodiment of the present invention, the boom control valve group 73 includes: a first constant pressure difference valve 732, a second constant pressure difference valve 734, a third constant pressure difference valve 736, a fourth constant pressure difference valve 738, a first electric proportional change-over valve 731, a second electric proportional change-over valve 733, a third electric proportional change-over valve 735, and a fourth electric proportional change-over valve 737, wherein the first constant pressure difference valve 732 is connected with the first electric proportional change-over valve 731, the second constant pressure difference valve 734 is connected with the second electric proportional change-over valve 733, the third constant pressure difference valve 736 is connected with the third electric proportional change-over valve 735, the fourth constant pressure difference valve 738 is connected with the fourth electric proportional change-over valve 737, an A port and a B port of the fourth electric proportional change-over valve 737 are connected with a cutter plate rotating motor 735, an A port and a B port of the third electric proportional change-over valve are connected with a three-joint arm cylinder 707, an A port and a B port of the second electric proportional change-over valve 733 are connected with a second joint arm cylinder 706, an A port and a port of the first electric proportional change-over valve 731 is connected with a main arm cylinder 707, LS pressure sensing ports of the first constant pressure difference valve 732, the second constant pressure difference valve 734, the third constant pressure difference valve 736 and the fourth constant pressure difference valve 738 are connected in parallel and then communicated with an LS pressure sensing port of the main constant pressure difference valve 722.

In this embodiment, the boom control valve group 73 includes: the hydraulic control system comprises a first constant pressure difference valve 732, a second constant pressure difference valve 734, a third constant pressure difference valve 736, a fourth constant pressure difference valve 738, a first electric proportional change valve 731, a second electric proportional change valve 733, a third electric proportional change valve 735 and a fourth electric proportional change valve 737, wherein the constant pressure difference valves and the electric proportional change valves are correspondingly connected to form four groups of hydraulic control valve groups in parallel connection, each group respectively controls different hydraulic execution parts, such as a cutter head rotating motor 708, a three-joint arm oil cylinder 707, a two-joint arm oil cylinder 706 and a main arm oil cylinder 705, and controls the actions of a cutter head, a three-joint arm, a two-joint arm and a main arm of an arm frame to avoid obstacles, wherein each constant pressure difference valve can enable the hydraulic flow entering the cutter head rotating motor 708, the three-joint arm oil cylinder 707, the two-joint arm oil cylinder 706 and the main arm oil cylinder 705 to be free from being influenced by loads, and is convenient to adjust the flow sensing port flow area by controlling a valve core 708 of each electric proportional change valve to realize the rotating motor, In addition, LS pressure sensing ports of all constant pressure difference valves are connected in parallel and then communicated with an LS pressure sensing port of a main constant pressure difference valve 722 through a load sensing pipeline, the load sensing pipeline screens the highest oil pressure in a cutter rotating motor 708, a three-section arm oil cylinder 707, a two-section arm oil cylinder 706 and a main arm oil cylinder 705 to act on the LS pressure sensing port of the main constant pressure difference valve 722, so that a valve core of the main constant pressure difference valve 722 correspondingly moves, inflow is reduced, the flow of hydraulic oil of a cutter motor mechanism is ensured, the rotating speed of all cutter motors is reduced, hydraulic oil preferably flows into the cutter rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, and finally the arm support and the cutter are driven to act to avoid obstacles, although the oil pump 704 simultaneously drives the cutter rotating motor 708, the two-section arm oil cylinder 706 and the cutter rotating motor 705 to avoid obstacles, The three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705 are supplied with oil, but the flow rate of hydraulic oil flowing into the cutting knife motor mechanism can be automatically reduced after the LS pressure sensing port of the main constant differential pressure valve 722 senses the load oil pressure of the cutter rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, the reduced flow rate is positively correlated with the current maximum load oil pressure in the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, therefore, when the rated output flow of the oil pump 704 is fixed, the sum of the hydraulic oil flows flowing into each hydraulic actuator is ensured to be matched with the rated output flow of the oil pump 704, and finally, the hydraulic system cannot have the problem of system overload even when the trimming and obstacle avoidance work is carried out simultaneously, so that the safety of the system is improved, and the trimming work efficiency is improved.

In a preferred embodiment of the present invention, a first two-way balance valve 710 and a second two-way balance valve 711 are respectively disposed between oil inlets and oil outlets of the two-joint boom cylinder 706 and between oil inlets and oil outlets of the three-joint boom cylinder 707, and a first balance valve 709 is disposed between oil inlets and oil outlets of the main boom cylinder 705.

In this embodiment, the first balancing valve 709, the first bidirectional balancing valve 710 and the second bidirectional balancing valve 711 can resist the load change when the knuckle arm ascends or descends, so that the movement is more gradual. When the device is not in operation at rest, the knuckle arm is kept from descending or being pulled up by other loads, and the device plays a role of a safety valve when a pipe is burst.

In a preferred embodiment of the present invention, the pressure difference between the input end of the main constant pressure differential valve 722 and the LS pressure sensing port of the main constant pressure differential valve 722 is 0.5-1 Mpa, so that the spring of the main constant pressure differential valve 722 can be adjusted to be smaller, thereby saving more energy.

In a preferred embodiment of the present invention, the second electromagnetic directional valve 724 is a two-position four-way valve, and a two-way relief valve 713 is disposed between the port a and the port B, wherein if the port a or the port B is an oil return port, a one-way valve 714 is further disposed on a pipeline between the port a and the two-way relief valve 713 or between the port B and the two-way relief valve 713, so that influence on the motor due to reverse rotation of the motor and oil return back pressure can be prevented.

In the preferred embodiment of the invention, the cutting knife motor mechanism comprises three sequentially cascaded cutting knife motors, including a first cutting knife motor 717, a second cutting knife motor 718 and a third cutting knife motor 719, and besides the first cutting knife motor 717, oil inlets of the second cutting knife motor 718 and the third cutting knife motor 719 are respectively provided with a first overflow valve 715 and a second overflow valve 716.

In this embodiment, the first and second relief valves 715 and 716 are integrated at oil inlets of the second and third cutting knife motors 718 and 719, and when the second and third cutting knife motors 718 and 719 are locked, the closer the relief valves are to the motors, the faster the reaction is, and the safety is more reliable.

In a preferred embodiment of the present invention, the cutting knife motor control valve set 72 further includes an LS overflow valve 726, an input end of the LS overflow valve 726 is connected to an LS pressure sensing port of the main constant pressure difference valve 722, and an output end of the LS overflow valve is connected to the oil tank 701.

In this embodiment, LS relief valve 726 limits the pressure in the load sense line, preventing flow saturation.

As shown in fig. 2, another embodiment of the present invention further provides a hedge trimming apparatus, which includes a base 1, a main arm 2, a two-section arm 3, a three-section arm 4, a cutterhead 5, a cutterhead revolving mechanism 6, an electrical component 8, and the load-sensitive hydraulic system 7 according to the above embodiment, wherein the electrical component 8 includes a first inclination sensor 801, a second inclination sensor 802, a third inclination sensor 803, and a cutterhead revolving encoder 804.

The base 1 is an installation platform of hedge trimming equipment and connects the hedge trimming equipment to mobile equipment (a special vehicle chassis, an engineering mechanical equipment chassis and the like), the arm support consists of a main arm 2, a two-section arm 3 and a three-section arm 4, and the change of the operation pose of a cutter head can be realized by adjusting the amplitude-changing angles of the main arm 2, the two-section arm 3 and the three-section arm 4, so that the requirements of different hedge trimming angles are met; and the three joint arms are coordinated and linked to realize the control of the motion track of the cutter head 5. The cutter head rotating mechanism 6 mainly rotates the rotary supporting movable cutter head 5 within the range of 0-360 degrees by rotating, and is linked with the arm support to realize the obstacle avoidance function of the cutter head 5. The load sensitive hydraulic system 7 and the electric part 8 are used for driving and controlling the movement mechanism, so that obstacle avoidance and hedge trimming are realized. Since the flow rate of the hydraulic actuator of this embodiment is unrelated to the load, and the flow rate is determined by the flow area of the flow sensing port, i.e., the PWM signal, in this embodiment, the hydraulic system, the first tilt sensor 801, the second tilt sensor 802, the third tilt sensor 803, and the cutter head rotary encoder 804 can be combined, and a corresponding arm rest posture adjustment strategy is adopted to precisely adjust the arm rest posture, so that the speed and the direction (track) of the cutter head can be directly controlled in real time, and the posture of the arm rest is monitored in real time for feedback compensation, so that the hedge trimming device can perform level trimming on an ultra-wide hedge or perform complex curved surface trimming on the hedge, and the specific control principle is shown in fig. 2.

The operation of the above-described embodiment will be described in further detail below.

Firstly, the hedge trimming equipment adopts a constant flow load sensitive loop with a postpositive constant pressure difference valve to drive a knuckle arm oil cylinder and a cutter head rotating motor 708, and the working flow Q of the three knuckle arm oil cylinders and the cutter head rotating motor 708_jFlow induction port flow area A of electric proportional change valve_jAnd constant pressure difference Δ p_DjIt is decided not to vary with load.

The outlet pressure of the flow sensing port of each electric proportional change valve is maintained to be higher than the load sensitive pressure p by adjusting the opening sizes of the first constant differential pressure valve 732, the second constant differential pressure valve 734, the third constant differential pressure valve 736 and the fourth constant differential pressure valve 738_LSHigh Δ p_DjFor example, the first fixed differential pressure valve 732 maintains the outlet pressure p of the first electrically proportional throttle valve 731_c1Specific load sensitive pressure p_LSHigh Δ p_D1Namely:

p_c1＝p_LS+Δp_D1

the main constant differential pressure valve 722 maintains the outlet pressure (electric proportional throttle inlet pressure) p of the oil pump 704 by adjusting the opening size to bypass the excess flow_pSpecific load sensitive pressure p_LSHigh Δ p_D0Namely:

p_p＝p_LS+Δp_D0

therefore, if the load of the master arm 2 is the maximum, the pressure difference Δ p of the flow sensing port of the first electric proportional throttle valve 731 is increased₁：

Δp₁＝p_p-p_c1＝(p_LS+Δp_D0)-(p_LS+Δp_D1)＝Δp_D0-Δp_D1

Correspondingly, the pressure difference delta p of the flow sensing ports of other electric proportional throttle valves_j：

Δp_j＝p_p-p_cj＝(p_LS+Δp_D0)-(p_LS+Δp_Dj)＝Δp_D0-Δp_Dj

Flow rate Q of each flow sensing port_j：

According to the above formula, the working flow rates of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705 are changed from the flow rate sensing port flow area A of the respective electric proportional change valve_jAnd constant pressure difference Δ p_DjDetermination of where Δ p_DjHas been set in advance, so that the flow rate is measured by the flow area A of the flow sensing port_jI.e. the PWM signal, is determined to be invariant with load.

Compared with the traditional constant-flow throttling and speed-regulating hydraulic system, the constant-flow load sensitive hydraulic system with the rear constant-pressure differential valve in the embodiment is more energy-saving.

When the traditional constant flow throttling and speed regulating hydraulic system regulates speed, the oil pump 704 is always maintained at the highest pressure, the speed regulation is realized by overflowing redundant flow through the main overflow valve 721, and meanwhile, the traditional constant flow throttling and speed regulating hydraulic system cannot realize the composite linkage of an actuator (an oil cylinder or a motor), so that the hydraulic system has a large amount of throttling and overflow speed regulating energy consumption during working.

When the constant-flow load sensitive hydraulic system with the postpositional constant-pressure differential valve works, the outlet pressure p of the oil pump_pPressure p sensitive to load only_LSHigh Δ p_D0While carrying a sensitive pressure p_LSThe maximum load pressure screened by the hydraulic system is smaller than the overflow pressure of the main overflow valve 721 of the hydraulic system, so the system is more energy-saving.

The constant-flow load sensitive hydraulic system with the rear-mounted constant-pressure differential valve can realize composite linkage, the system can distribute more pressure oil to apply work to an actuator, and the bypass waste pressure oil is less, so that the energy is saved.

Since the first, second, third, and fourth constant pressure difference valves 732, 734, 736, 738 have no regulating springs, Δ p is_DjApproximately 0, known electric proportional change valvesDifferential pressure Δ p of flow sensing port_j＝Δp_D0-Δp_DjTherefore, the load sensitive loop only needs to maintain the pressure difference delta p of the flow sensing port of each electric proportional change valve_jSlightly larger than 0, so the spring of the main constant pressure difference valve 722 can be adjusted smaller, i.e. Δ p_D0Can be approximately adjusted to about 0.7 Mpa.

Therefore, when each of the electric proportional change valves is operated, the pressure difference Δ p of the pressure oil passing through the flow sensing port of each of the electric proportional change valves_jThe throttling loss of each electric proportional throttling valve is small; when the electric proportional throttle valves, the first electromagnetic directional valve 723 and the second electromagnetic directional valve 724 do not work, the hydraulic system is in a low-energy-consumption standby state, hydraulic oil bypasses the oil return tank 701 through the main constant pressure difference valve 722, and at the moment, the load sensitive pressure p is_LSAnd the cutter motor mechanism load P at the output of the main constant differential pressure valve 722_C5Are all 0, i.e.:

p_LS＝p_c5＝0

p_p＝p_LS+Δp_D0

the operating differential pressure of the main constant differential pressure valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0-p_c5＝Δp_D0

due to Δ p_D0And the throttling loss of the main constant pressure difference valve 722 is small, so that the energy is saved compared with the common constant flow load sensitive system.

Third, the cutting knife motor mechanism is connected to the rear of the main constant pressure difference valve 722 in the above embodiment, and the LS pressure sensing port of the main constant pressure difference valve 722 is communicated with the oil inlet of the cutting knife motor mechanism through the two-way flow valve 725, so that the hedge trimming device based on the hydraulic system can simultaneously perform boom posture adjustment and cutting knife set rotation, and can realize that the boom posture adjustment is prior to the cutting knife set rotation, which is beneficial to boom avoidance.

1. When the first electromagnetic directional valve 723 and the second electromagnetic directional valve 724 are powered off and all the electric proportional change valves are powered on, the load sensitive pressure p_LSFor each electric proportional change valve outlet pressure p_c1～p_c4The maximum value of (a), namely, the deck rotation motor 708,Maximum load in three-joint arm cylinder 707, two-joint arm cylinder 706, main arm cylinder 705:

p_LS＝max(p_c1 p_c2 p_c3 p_c4)

p_c5＝0

if p is_p＝p_LS+Δp_D0Then, the working pressure difference of the main constant pressure difference valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0＞0

then the formula p_p＝p_LS+Δp_D0When this is true, the main constant differential pressure valve 722 has a sufficient operating differential pressure (p)_LS+Δp_D0) Can be used to regulate and bypass excess flow in an effort to maintain p_pRatio p_LSHigh Δ p_D0. At this time, the working flow Q of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705_jFlow induction port flow area A of each electric proportional change valve_jDecision, independent of load. Then the cutter head rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705 work, and the cutting knife motor mechanism does not work, so that the arm support posture is adjusted.

2. When the first electromagnetic directional valve 723 and the second electromagnetic directional valve 724 are powered on and all the electric proportional change valves are powered off, the LS pressure sensing port of the main constant differential pressure valve 722 is communicated with the oil inlet of the cutter motor mechanism through the two-way flow valve 725, and at the moment, the load sensitive pressure p is_LSAnd the pressure P at the output of the main constant differential pressure valve 722_C5And (3) equality:

p_LS＝p_c5

if p is_p＝p_LS+Δp_D0Then, the working pressure difference of the main constant pressure difference valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0-p_c5＝Δp_D0＞0

then the formula p_p＝p_LS+Δp_D0When the pressure is established, all the hydraulic oil drives the cutting knife motor mechanism to do work through the main constant pressure difference valve 722, and the cutter head rotates the cutter headAnd when the hydraulic trimming machine reaches 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705 do not work, the hedge trimming is normally carried out.

3. When the first electromagnetic directional valve 723 and the second electromagnetic directional valve 724 are powered and all the electric proportional throttle valves are powered, the LS pressure sensing port of the main constant pressure differential valve 722 is communicated with the oil inlet of the cutter motor mechanism through the two-way flow valve 725, and at this time:

a. if the load p of the cutter motor mechanism_c5If the load is less than the maximum load of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, then:

p_LS＝max(p_c1 p_c2 p_c3 p_c4)

p_c5＜p_LS

if p is_p＝p_LS+Δp_D0Then, the operating pressure difference of the main constant pressure difference valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0-p_c5＞0

then the formula p_p＝p_LS+Δp_D0When this is true, the main constant differential pressure valve 722 has a sufficient operating differential pressure (p)_LS+Δp_D0-p_c5) Regulate and bypass excess flow in an effort to maintain p_pRatio p_LSHigh Δ p_D0. At this time, the working flow Q of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705_jFlow induction port flow area A of each electric proportional change valve_jDecision, independent of load. Then, the pressure oil preferentially flows to the cutter head rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, and the redundant flow flows to the cutting knife motor mechanism through the main constant pressure difference valve 722, namely, the hedge is trimmed by decelerating while the posture of the arm support is adjusted.

b. If the load p of the cutter motor mechanism_c5If the load is greater than the maximum load of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, then:

p_LS＝p_c5

if p is_p＝p_LS+Δp_D0Then, the operating pressure difference of the main constant pressure difference valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0-p_c5＝Δp_D0＞0

then the formula p_p＝p_LS+Δp_D0When this is true, the main constant differential pressure valve 722 has a sufficient operating differential pressure (Δ p)_D0) Regulate and bypass excess flow in an effort to maintain p_pRatio p_LSHigh Δ p_D0. At this time, the working flow Q of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705_jFlow induction port flow area A of each electric proportional change valve_jDecision, independent of load. Then, the pressure oil preferentially flows to the cutter head rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, and the redundant flow flows to the cutting knife motor mechanism through the main constant pressure difference valve 722, namely, the hedge is trimmed by decelerating while the posture of the arm support is adjusted.

4. If the LS pressure sensing port of the primary constant differential pressure valve 722 communicates with the oil tank 701 through the two-way flow valve 725 instead of communicating with the cutter motor mechanism oil inlet.

When the first electromagnetic directional valve 723, the second electromagnetic directional valve 724 and all the electric proportional change valves are electrified, if the load p of the cutting knife motor mechanism is on_c5If the load is greater than the maximum load of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, then:

p_LS＝max(p_c1 p_c2 p_c3 p_c4)

p_c5＞p_LS

if p is_p＝p_LS+Δp_D0Then, the operating pressure difference of the main constant pressure difference valve 722 is:

p_VD0＝p_p-p_c5＝p_LS+Δp_D0-p_c5＝Δp_D0＜0

then the formula p_p＝p_LS+Δp_D0If not, the main constant pressure difference valve 722 is not enoughWorking differential pressure regulating and bypassing excess flow in an effort to maintain p_pRatio p_LSHigh Δ p_D0. At this time, the working flow Q of the cutterhead rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705_jUncontrollable, and uncontrollable posture and obstacle avoidance track of the arm support.

In summary, when the hedge trimming device trims the hedge and meets an obstacle, the arm support actively avoids the obstacle, at this time, the first electromagnetic directional valve 723, the second electromagnetic directional valve 724 and the electric proportional change valves are powered on simultaneously, the flow of the oil pump 704 preferentially flows to the cutter head rotating motor 708, the three-section arm oil cylinder 707, the two-section arm oil cylinder 706 and the main arm oil cylinder 705, the surplus flow flows to the cutter motor mechanism through the main constant pressure difference valve 722, at this time, the section arm and cutter head rotating mechanism quickly responds to adjust the posture, meanwhile, the cutter motor mechanism decelerates but does not stop rotating, at this time, the obstacle avoidance response of the hedge trimming device is quick, and the cutter motor mechanism always works without leaving a large hedge and needs manual secondary trimming, and the obstacle avoidance is more reliable and safe because the priorities of the section arm oil cylinder and the cutter head rotating mechanism are higher than that of the cutter.

The load-sensitive hydraulic system in the above embodiment can be applied to hedge trimming equipment and guardrail cleaning equipment, and at this time, only the cutter head 5 needs to be replaced by the cleaning brush 9, and the hydraulic motor drives the cleaning brush 9 to rotate, so as to clean the guardrail.

The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.