WO2021212714A1 - 压力耦合液压混合动力驱动回路及其控制方法、挖掘机 - Google Patents

压力耦合液压混合动力驱动回路及其控制方法、挖掘机 Download PDF

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Publication number
WO2021212714A1
WO2021212714A1 PCT/CN2020/111986 CN2020111986W WO2021212714A1 WO 2021212714 A1 WO2021212714 A1 WO 2021212714A1 CN 2020111986 W CN2020111986 W CN 2020111986W WO 2021212714 A1 WO2021212714 A1 WO 2021212714A1
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Prior art keywords
pressure
port
oil
way
matcher
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PCT/CN2020/111986
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English (en)
French (fr)
Inventor
何清华
方庆琯
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山河智能装备股份有限公司
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Publication of WO2021212714A1 publication Critical patent/WO2021212714A1/zh

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2264—Arrangements or adaptations of elements for hydraulic drives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
    • F15B1/02—Installations or systems with accumulators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/14—Energy-recuperation means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/214—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being hydrotransformers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/62—Hybrid vehicles

Definitions

  • the invention relates to hydraulic transmission technology, in particular to a pressure-coupled hydraulic hybrid drive circuit and a control method thereof, and an excavator.
  • hydraulic systems with energy recovery function usually use hydraulic pump + accumulator as the drive circuit of the hybrid power source.
  • the load of the actuator is negative, the load does work on the actuator, and the hydraulic energy (pressure oil) output by the actuator is stored in the accumulator. At this time, the hydraulic pump is in a state of unloading or low-power operation.
  • the accumulator releases the stored hydraulic energy (pressure oil) together with the pressure oil output by the hydraulic pump to drive the actuator to perform work on the load; at this time, the hydraulic pump is in a high-power operation state .
  • the hydraulic hybrid drive circuit of hydraulic pump + accumulator is widely used in construction machinery, lifting machinery and steel rolling equipment.
  • the technical problem that restricts the popularization and application of the hydraulic hybrid drive circuit is the pressure matching problem between the hydraulic pump pressure, the load pressure of the actuator and the hydraulic oil pressure of the accumulator (hereinafter referred to as the accumulator oil pressure).
  • the pressure of the hydraulic pump is determined by the minimum load pressure; the pressure of the actuator is determined by the external load; the oil pressure of the accumulator is determined by the change of the charging pressure and the gas volume, and has nothing to do with the external load.
  • this method is only suitable for working conditions with a certain external load and small changes, and is basically not suitable for construction machinery.
  • This is the main method currently used in the hydraulic hybrid power system of construction machinery. This method will produce greater overflow energy loss and throttling energy loss, and attenuate the energy-saving effect of accumulators as auxiliary power sources.
  • the system is complicated, which increases the failure rate and the difficulty of maintenance.
  • the technical problem to be solved by the present invention is to provide a pressure-coupled hydraulic hybrid drive circuit and its control method, as well as an excavator in view of the shortcomings of the prior art.
  • the online matching of hydraulic pump pressure, actuator load pressure and accumulator hydraulic oil pressure ensures that the function of the accumulator as an auxiliary power source is not lost due to load changes.
  • a pressure-coupled hydraulic hybrid drive circuit including a three-way pressure matching device, the first external oil port of the three-way pressure matching device is connected to the first external oil port of the actuator An oil port; the second oil port of the three-way pressure matcher and the second external oil port of the actuator are connected to the hydraulic pump and the oil tank through the control valve; the third oil port of the three-way pressure matcher is connected to the accumulator oil port.
  • the present invention is equipped with a three-way pressure matcher in the hydraulic circuit.
  • a three-way pressure matcher By adjusting the pressure and flow rate of the three-way pressure matcher, online hydraulic pump pressure, actuator load pressure and accumulator hydraulic oil pressure can be realized.
  • Matching ensures that the function of the accumulator as an auxiliary power source is not lost due to load changes, and is easy to implement.
  • the drive circuit has a simple structure and will not cause overflow energy loss and throttling energy loss.
  • the three-way pressure matcher includes a first energy conversion device and a second energy conversion device; the first energy conversion device and the second energy conversion device are connected to one side of the oil port to form a first part of the three-way pressure matcher.
  • An oil port; the oil port on the other side of the first energy conversion device and the oil port on the other side of the second energy conversion device are the second oil port and the third oil port of the three-way pressure matcher, respectively;
  • the transmission shaft of the first energy conversion device is rigidly coaxially connected with the transmission shaft of the second energy conversion device, and the movement directions of the first energy conversion device and the second energy conversion device are the same.
  • the three-way pressure matching device of the invention has simple structure, easy realization, strong practicability, low failure rate and easy maintenance.
  • the first energy conversion device and the second energy conversion device may be hydraulic motors, and the two hydraulic motors have the same rotation direction; the hydraulic motors may be in a motor working condition or a pump working condition;
  • the hydraulic motor is one of a plunger motor, a gear motor, and a vane motor;
  • the plunger motor includes a radial plunger motor and an axial plunger motor;
  • the gear motor includes an internal gear Gear motors and external gear motors;
  • the vane motors include single-acting vane motors and double-acting vane motors.
  • the first oil port, the second oil port, and the third oil port of the three-way pressure matching device of the present invention are all equipped with pressure detection devices.
  • the pressure detection device such as pressure sensor
  • the hydraulic pump and the control valve are all electrically connected to the controller.
  • the pressure detection device sends the detected data to the controller, and the controller can adjust the discharge of the hydraulic pump according to the pressure and flow value. Volume and control valve opening.
  • the three oil ports of the three-way pressure matcher satisfy the following mathematical model:
  • q2 and q3 are the flow rate of the second port and the third port of the three-way pressure matcher respectively;
  • ⁇ P is the pressure loss at the inlet of the energy conversion device in the three-way pressure matcher;
  • PA1 is the positive load drive cavity of the actuator or The load pressure of the negative load return cavity,
  • P2 is the second port pressure of the three-way pressure matcher.
  • the pressure and flow rate of the second oil port of the three-way pressure matching device are adjusted to achieve the three-way pressure matching
  • the pressure values of the three oil ports of the actuator are matched with the load pressure of the actuator.
  • the pressure and flow rate of the second oil port of the three-way pressure matcher can be adjusted by controlling the displacement of the hydraulic pump and the opening of the control valve, and the control is simple and easy to implement.
  • control valve of the present invention includes a multi-way reversing valve; the pressure oil port of the multi-way reversing valve is connected to the outlet of the hydraulic pump; the oil return port of the multi-way reversing valve is connected to the oil tank; The first working oil port of the multi-way reversing valve is connected to the second oil port of the three-way pressure matcher; the second working oil port of the multi-way reversing valve is connected to the second external oil port of the actuator.
  • the present invention also provides an excavator, the above-mentioned pressure coupling hydraulic hybrid drive circuit of the excavator.
  • the present invention also provides a control method of the above-mentioned pressure-coupled hydraulic hybrid drive circuit.
  • the method mainly includes: adjusting the pressure and flow rate of the second oil port of the three-way pressure matcher to achieve the The three-way pressure matcher matches the pressure values of the three oil ports with the load pressure of the actuator.
  • the pressure and flow rate of the second oil port of the three-way pressure matcher can be adjusted by controlling the displacement of the hydraulic pump and the opening of the control valve.
  • the following mathematical model can be used to efficiently adjust the pressure and flow rate of the second oil port of the three-way pressure matcher:
  • q2 and q3 are the flow rate of the second port and the third port of the three-way pressure matcher respectively;
  • ⁇ P is the pressure loss at the inlet of the energy conversion device in the three-way pressure matcher;
  • PA1 is the positive load drive cavity of the actuator or The load pressure of the negative load return cavity,
  • P2 is the second port pressure of the three-way pressure matcher.
  • the present invention has the following beneficial effects:
  • the function of the accumulator in the circuit of the present invention as an auxiliary power source will not be lost due to changes in the load pressure of the actuator, and can be effectively used for energy-saving operation when the load of the actuator has a positive-negative interval changing working condition, which solves the existing problem.
  • the present invention has simple structure, easy realization, low failure rate and easy maintenance
  • the invention does not produce overflow energy loss and throttling energy loss, and has a good energy saving effect.
  • Figure 1 is a schematic diagram of the structure of the three-way pressure matching device of the present invention.
  • Figure 2 is a schematic diagram of the pressure-coupled hydraulic hybrid drive circuit structure of the present invention.
  • Figure 3 is a schematic diagram of the pressure and the flow rate at the three oil ports K1, K2, K3 of the three-way pressure matcher of the present invention
  • FIG. 4 is a schematic diagram of the driving circuit of the present invention for driving the hydraulic cylinder of the hydraulic excavating arm;
  • Fig. 5 is a schematic diagram of a prior art driving circuit of a hydraulic cylinder of a hydraulic excavating arm.
  • the invention uses a hydraulic pump as the main power and an accumulator (air-filled accumulator) as an auxiliary power hydraulic drive circuit, referred to as a pressure-coupled hydraulic hybrid drive circuit.
  • the pressure-coupled hydraulic hybrid drive circuit is used for energy-saving operation when the load of the actuator is changed between positive and negative intervals.
  • the circuit can recover the pressure energy generated by the negative load on the execution element.
  • the circuit can release the recovered pressure energy as an auxiliary power source.
  • the actuator can be either a hydraulic cylinder or a hydraulic motor; the negative load can be external force (including gravity), or the inertial force generated by the actuator when braking.
  • the pressure-coupled hydraulic hybrid drive circuit includes conventional hydraulic system variable hydraulic pumps, control valves (multi-way reversing valves or other related valves), fuel tanks and actuators, and is also specially configured to be useful Inflatable accumulator used as auxiliary power source, three-way pressure matching device using pressure coupling technology, several pressure sensors and controllers.
  • the inflatable accumulator can be either a bladder type or a piston type; the inflatable body can be nitrogen or some inert gas (such as helium).
  • the inflation pressure of the inflatable accumulator must be greater than the load pressure produced by the positive and negative loads in the working chamber of the actuator.
  • the pressure-coupled hydraulic hybrid drive circuit can transfer the pressure oil generated in the oil return cavity of the actuator to the accumulator for storage when the negative load is doing work on the actuator. This storage process can be carried out smoothly even when the pressure in the return cavity of the actuator is lower than the charging pressure of the accumulator, and is not affected by load changes.
  • the pressure-coupled hydraulic hybrid drive circuit can input the pressure oil stored in the accumulator into the actuator drive cavity when the actuator drives the external load, and use it as auxiliary power to achieve energy saving. The process is not affected by the pressure change of the accumulator. Influence.
  • the reason why the pressure-coupled hydraulic hybrid drive circuit has the above-mentioned functions is because it is equipped with a three-way pressure matching device using pressure coupling technology.
  • the three-way pressure matcher is formed by coupling the first energy conversion device and the second energy conversion device.
  • the energy conversion device can input hydraulic energy through the oil port and output mechanical energy on the drive shaft; it can also input mechanical energy on the drive shaft and output hydraulic energy through the oil port.
  • the energy conversion device may be a certain hydraulic component, such as a hydraulic cylinder, a hydraulic pump, a hydraulic motor, and so on.
  • the hydraulic motor can be a plunger motor (including radial and axial), gear motor (including internal meshing and external meshing) or vane motor (including single-acting and double-acting); each motor can be in the motor
  • the working condition can also be in the pump working condition.
  • the three-way pressure matching device adopting pressure coupling technology is formed by coupling two hydraulic motors (pumps).
  • the coupling in the present invention includes: (1) connecting the oil ports on one side of the two motors to form a common external oil port K1, and the oil ports K2 and K3 on the other side of each motor maintain independent external connections; (2) The drive shafts of the two motors adopt rigid coaxial connection.
  • the coaxial connection can be coaxial connection of inner and outer spline shafts, or coaxial connection of shaft and shaft sleeve with flat keys, or other coaxial connection methods ; (3)
  • the rotation of the two motors must be the same, but they can rotate forward and reverse; (4)
  • the displacement of the two motors can be the same or different.
  • K1, K2, and K3 are the external oil ports, and K1 is the common oil port.
  • the pressure-coupled hydraulic hybrid drive circuit including the three-way pressure matcher, and the connection mode of each component is shown in Figure 2.
  • the two external oil ports of the actuator are A1 and B1;
  • A1 is the oil return port when the actuator bears a negative load, and is also the oil inlet when the actuator drives a positive load;
  • B1 is the oil inlet when the actuator bears a negative load. Oil port.
  • the pressure-coupled hydraulic hybrid drive circuit including the three-way pressure matcher, and the connection mode of each component is shown in Figure 2.
  • the two external oil ports of the actuator are A1 and B1;
  • A1 is the oil return port when the actuator bears a negative load, and it is also the oil inlet when the actuator drives a positive load;
  • B1 is the oil return port when the actuator bears a negative load. imported oil.
  • connection modes of the components of the above-mentioned circuit include (but are not limited to) the following: (1)
  • the pressure port P of the multi-way reversing valve is connected to the outlet of the variable hydraulic pump, and the oil return port T of the multi-way reversing valve is connected to the oil tank.
  • the working port B of the directional valve is connected to the actuator port B1 (the second external port), and the working port A is connected to the three-way pressure matching device port K2; (2) the three-way pressure matching device port K3 is connected to the air-filled type Accumulator inlet and outlet port X, three-way pressure matcher port K1 connected to the actuator port A1 (the first external port); (3) The pressure oil output by the variable hydraulic pump is controlled by the multi-way reversing valve.
  • the three ports of the three-way pressure matcher are equipped with pressure sensors PU1, PU2, and PU3. These sensors (including but not limited to the above three) send online detection values to the controller for the pressure coupling algorithm to adjust the variable The displacement of the hydraulic pump and the opening of the multi-way reversing valve are controlled.
  • the working mode of the three-way pressure matcher is: when the hydraulic oil flows from K1 port to K2 and K3, the motor of K2 port (the left motor in Figure 2) is the motor working condition, K3 The motor of the oil port (the right motor in Fig. 2) is in the pump mode; when the hydraulic oil flows from K2 and K3 ports to K1, the motor of the K2 port (the left motor in Fig. 2) is in the pump mode, and the K3 port The motor (the right motor in Figure 2) is the motor working condition.
  • the working mode of the three-way pressure matcher is: when the hydraulic oil flows from port K1 to K2 and K3, the motor at port K2 (the left motor in Figure 2) is the motor driver.
  • the motor of K2 port (the left motor in Figure 2) is in the pump mode.
  • the motor of the K3 port (the right motor in Figure 2) is the motor working condition.
  • the pressure coupling hydraulic hybrid drive circuit of the present invention can be passed when the load pressure PA1 of the actuator changes or the oil pressure PX of the accumulator fluctuates in the field conditions.
  • P2 value and q2 value are adjusted to ensure the stability of the accumulator's function of retracting and discharging the pressure oil, and is used for energy-saving operation when the load of the actuator is changed between positive and negative intervals (that is, to ensure the stability of the accumulator’s function of retracting and discharging the pressure oil. ).
  • the pressure-coupled hydraulic hybrid drive circuit can collect the pressure oil generated in the oil return cavity of the actuator into the accumulator for storage; this income storage process, even when the pressure of the actuator return cavity is low It can also proceed smoothly when the accumulator is charged with pressure, and is not affected by load changes.
  • the pressure-coupled hydraulic hybrid drive circuit can input the pressure oil stored in the accumulator into the actuator drive cavity, which can be used as auxiliary power to achieve energy saving. The process is not affected by the pressure change of the accumulator. Influence.
  • the adjustment of the P2 value and the q2 value can be controlled by the displacement of the variable hydraulic pump and the opening of the multi-way reversing valve.
  • the displacement of the variable hydraulic pump and the opening of the multi-way reversing valve are reasonably adjusted to realize the matching of the pressure values of the three ports of the three-way pressure matcher with the load pressure PA1 of the actuator, which ensures the circuit of the present invention
  • the function of the middle-charged accumulator as an auxiliary power source is not lost due to the change of the load pressure of the actuator, and it can be effectively used for energy-saving operation when the load of the actuator is changed between positive and negative.
  • the pressure coupling hydraulic hybrid drive circuit of the hydraulic excavating boom hydraulic cylinder includes a boom cylinder bearing gravity load, a three-way pressure matcher, a gas-filled accumulator, a multi-way valve boom linkage, a variable hydraulic pump, and a number of pressure sensors (P1, P2, P3, PA1, PB1) and the controller.
  • the K1 port of the three-way pressure matcher is connected to the rodless cavity port A1 of the boom cylinder, the K2 port is connected to the working port A of the multi-way valve boom linkage, and the K3 port is connected to the inlet and outlet port X of the gas-filled accumulator ,
  • the boom cylinder has rod cavity oil port B1 connected to the working oil port B of the multi-way valve boom linkage, and the variable hydraulic pump is connected to the oil port P of the multi-way valve.
  • the pilot control oils of the multi-way valve boom linkage are pa7 and pb7 respectively.
  • the boom cylinder In the actual working condition of the hydraulic excavator, the boom cylinder has to bear the weight of the entire boom and bucket (including cargo) of the hydraulic excavator.
  • the weight converted to the force of the boom cylinder piston rod end is G.
  • G When the hydraulic excavating boom descends and the boom cylinder piston rod retracts, G is a negative load; when the hydraulic excavating boom rises and the boom cylinder piston rod extends, G is a positive load.
  • A1 is the pressure bearing area of the boom cylinder without rod cavity
  • B1 is the pressure bearing area of the boom cylinder with rod cavity
  • PA1 (G+PB1 ⁇ B1 )/A1.
  • PB1 is the hydraulic pressure of the rod cavity of the boom cylinder.
  • the oil pressure PX of the gas-filled accumulator should be about 5-10Mpa greater than PA1.
  • the multi-way valve boom linkage When the pilot control oil pb7 of the multi-way valve boom linkage works, the multi-way valve boom linkage is in the left position, and the pressure oil output by the variable hydraulic pump passes through the boom linkage B port to the boom cylinder rod cavity oil port B1.
  • the negative load G drives the boom cylinder piston rod to retract, and the rodless cavity of the boom cylinder returns oil to the three-way pressure matcher K1 port through the oil port A1.
  • the oil return pressure is PA1, and the oil return flow is q1.
  • the flow After q1 enters the three-way pressure matcher, the flow is divided into two channels, and the flow q2 flows out of port K2 through the left motor, and returns to the fuel tank after reaching port A of the multi-way valve boom linkage.
  • the flow q3 exits K3 port through the right motor and enters the accumulator for storage.
  • the left motor inlet pressure P1 is PA1
  • the outlet pressure P2 is approximately 0, which is the motor working condition.
  • the input hydraulic power is PA1 ⁇ q2, and the output mechanical power is used to drive the right motor.
  • PA1 ⁇ q2- ⁇ P ⁇ q1 (PX-PA1) ⁇ q3
  • the value of q1 is determined by the descending speed of the excavating boom and cannot be changed arbitrarily after the working condition is determined.
  • the value of q2 is determined by the displacement of the variable pump, which can be used as an adjustment parameter to be controlled by the controller according to equations (6) and (7). For a certain PA1 value and PX value, a suitable q2 value can always be found, so that the formula (7) holds, even when PX is greater than PA1, the q2 value can be found.
  • Equations (6) and (7) are the mathematical models of the pressure coupling algorithm for the descending conditions of the hydraulic excavating boom.
  • the multi-way valve boom linkage When the pilot control oil pa7 of the multi-way valve boom linkage works, the multi-way valve boom linkage is in the right position, and the pressure oil output by the variable hydraulic pump passes through the boom linkage A port to the three-way pressure matcher K2 port, and accumulates energy
  • the pressure oil stored in the device enters the right motor through the K2 port of the three-way pressure matcher, and the outlet pressure of the right motor is PA1.
  • the right motor is in motor mode
  • the input hydraulic power is (PX-PA1) ⁇ q3
  • the output mechanical power drives the left motor, increasing the oil inlet pressure of port K2 from P2 to PA1, and the left motor is in pump mode .
  • Equations (6) and (8) are the mathematical model of the pressure coupling algorithm for the hydraulic excavating boom in the rising working condition.
  • the controller adjusts P2 or q2 according to formulas (6) and (8) to realize the matching of determined PA1 and PX.
  • the driving circuit currently used in hydraulic excavating boom hydraulic cylinders is shown in Figure 5.
  • the pressure-coupled hydraulic hybrid drive circuit of the present invention is used to drive the hydraulic cylinder of the hydraulic excavating arm, which can significantly reduce the energy consumption of the hydraulic pump and realize energy saving compared with the existing circuit shown in FIG. 5. Assuming that the rising and falling strokes of the boom hydraulic cylinder are all L, and the time is all t.
  • the output pressure of the hydraulic pump is 3-5Mpa, and the energy consumption of the two circuits is basically the same.
  • the return oil whose pressure in the rodless cavity of the boom hydraulic cylinder is PA1 is returned to the oil tank through the multi-way valve, and the pressure energy becomes heat energy wasted.
  • the pressure of the rodless chamber of the boom hydraulic cylinder is both PA1
  • Wi is all provided by a hydraulic pump; while in the circuit of the present invention, Wi is provided by a hydraulic pump and an accumulator as auxiliary power.
  • Wx is about 180-220 kJ, which means that the energy-saving effect is quite obvious.

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Abstract

本发明公开了一种压力耦合液压混合动力驱动回路及其控制方法、挖掘机，压力耦合液压混合动力驱动回路包括三通压力匹配器，所述三通压力匹配器的第一外接油口接执行元件的第一油口；所述三通压力匹配器第二油口、执行元件第二外接油口通过控制阀接液压泵和油箱；所述三通压力匹配器第三油口接蓄能器油口。三通压力匹配器油口压力和流量满足压力耦合关系式：(PA1±△P)q1＝P2·q2+PX·q3和q1＝q2+q3。通过调节P2和q2，实现蓄能器作为辅助动力源的功能不会因执行元件负载压力PA1的变化而缺失，解决了混合动力现有技术中液压泵压力、执行元件的负载压力和蓄能器的液压油压力难以匹配、节能运行困难的问题。

Description

压力耦合液压混合动力驱动回路及其控制方法、挖掘机 技术领域
本发明涉及液压传动技术，特别是一种压力耦合液压混合动力驱动回路及其控制方法、挖掘机。
背景技术
为适应执行元件所受负载在正负区间变化的工况，具有能量回收功能的液压系统通常采用液压泵+蓄能器作混合动力源的驱动回路。当执行元件的负载为负时，负载对执行元件做功，执行元件输出的液压能(压力油)被储存在蓄能器中，此时液压泵处于卸荷或小功率运行状态。当执行元件的负载为正时，蓄能器将储存的液压能(压力油)释放出来和液压泵输出的压力油一起，共同驱动执行元件对负载做功；此时液压泵虽然为大功率运行状态，但由于有蓄能器作辅助动力源，所以也节省了驱动功率，实现了节能。因此液压泵+蓄能器的液压混合动力驱动回路在工程机械、起重举升机械和轧钢设备中都会得到广泛应用。目前，制约该液压混合动力驱动回路推广应用的技术难题是液压泵压力、执行元件的负载压力和蓄能器的液压油压力(以下简称蓄能器油压)三者之间的压力匹配问题。液压泵的压力由最小的负载压力决定；执行元件的压力由外负载决定；蓄能器油压由充气压力及气体容积的变化决定，与外负载无关。这就给压力匹配带来困难：(1)负负载工况，外负载对执行元件做功时，执行元件输出液压油的压力由负载决定，若此压力小于蓄能器油压，则执行元件输出的压力油根本不能进入蓄能器储存。(2)正负载工况时，若执行元件的负载压力不小于蓄能器油压，则蓄能器储存的压力油释放不出来，无法起辅助动力源作用；而执行元件的负载压力过多小于蓄能器油压时，又会产生蓄能器储存压力油的瞬间释放，超出执行元件所需后溢流浪费。(3)无论负负载工况或正负载工况，只要外负载变化引起的执行元件负载压力的变化达到一定限度，都会使蓄能器正常的收(储存)或放(释放)压力油过程终止，无法起辅助动力源作用。(4)若考虑到蓄能器油压还会在蓄能器收(储存)或放(释放)油的过程中发生变化(因蓄能器充气体积变化)，则问题就更加复杂。
现有技术克服上述困难的方法有两种。其一，优化设计执行元件的承压面积(或马达排量)，精准计算蓄能器的充气压力和初始容积，使蓄能器油压和执行元件的负载压力匹配(蓄能器收油时，负载压力始终略大于蓄能器油压；蓄能器放油时，负载压力始终略小于蓄能器油压)。显然，优化设计承压面积的难度很大，因为承压面积的设计首 先是要保证满足负载驱动力的需要和负载速度的需要，此后才能考虑和蓄能器油压的匹配。同时，这种方法只适用于外负载确定且变化较小的工况，对工程机械基本不适用。其二，在执行元件和蓄能器、液压泵之间设置增压器、比例减压阀或调压阀组，实时调节蓄能器出口油压、液压泵输出压力及负负载时执行元件输出油压，以实现基本的压力匹配。这是目前工程机械液压混合动力系统中采用的主要方法。这种方法将产生较大的溢流能量损失和节流能量损失，衰减蓄能器作辅助动力源的节能效果。同时还使系统复杂，增加了故障率和检修难度。
发明内容
本发明所要解决的技术问题是，针对现有技术不足，提供一种压力耦合液压混合动力驱动回路及其控制方法、挖掘机，在不产生溢流能量损失和节流能量损失的前提下，实现液压泵压力、执行元件负载压力和蓄能器液压油压力的在线匹配，保证蓄能器作为辅助动力源的功能不因负载变化而缺失。
为解决上述技术问题，本发明说采用的技术方案为：一种压力耦合液压混合动力驱动回路，包括三通压力匹配器，所述三通压力匹配器的第一外接油口接执行元件的第一油口；所述三通压力匹配器第二油口、执行元件第二外接油口通过控制阀接液压泵和油箱；所述三通压力匹配器第三油口接蓄能器油口。
本发明借由上述结构，在液压回路中设置三通压力匹配器，通过调节三通压力匹配器的压力和流量，即可实现液压泵压力、执行元件负载压力和蓄能器液压油压力的在线匹配，保证蓄能器作为辅助动力源的功能不因负载变化而缺失，容易实现，驱动回路结构简单，不会产生溢流能量损失和节流能量损失。
所述三通压力匹配器包括第一能量转换装置和第二能量转换装置；所述第一能量转换装置、第二能量转换装置一侧的油口连通后形成所述三通压力匹配器的第一油口；所述第一能量转换装置另一侧的油口、第二能量转换装置另一侧的油口分别为所述三通压力匹配器的第二油口、第三油口；所述第一能量转换装置的传动轴与所述第二能量转换装置的传动轴刚性同轴连接，且所述第一能量转换装置和第二能量转换装置的运动方向相同。本发明三通压力匹配器结构简单，容易实现，实用性强，故障率低，检修容易。
本发明中，为了设计简单，第一能量转换装置与所述第二能量转换装置可以是液压马达，两台所述液压马达转向相同；液压马达可以处于马达工况，也可以处于泵工况；优选的，所述液压马达为柱塞马达、齿轮马达、叶片马达中的一种；优选的，所述柱塞马达包括径向柱塞马达和轴向柱塞马达；所述齿轮马达包括内啮合齿轮马达和外啮合齿 轮马达；所述叶片马达包括单作用叶片马达和双作用叶片马达。
为了实现三通压力匹配器油口的压力和流量检测，本发明的三通压力匹配器第一油口、第二油口、第三油口处均安装有压力检测装置。
本发明中，压力检测装置(例如压力传感器)、液压泵、控制阀均与控制器电连接，压力检测装置将检测得到数据发送给控制器，控制器可以根据压力和流量值调节液压泵的排量和控制阀的开度。
本发明中，所述三通压力匹配器三个油口满足以下数学模型：
当液压油从所述三通压力匹配器第二油口、第三油口流向所述三通压力匹配器第一油口时，(PA1+△P)×(q2+q3)＝P2·q2+PX·q3；
当液压油从所述三通压力匹配器第一油口流向第二油口、第三油口时，(PA1-△P)×(q2+q3)＝P2·q2+PX·q3；
其中，q2、q3分别为三通压力匹配器第二油口流量、第三油口流量；△P为三通压力匹配器内能量转换装置进口的压力损失；PA1为执行元件正负载驱动腔或负负载回油腔的负载压力，PA1＝P1，P1为三通压力匹配器第一油口压力；PX为蓄能器油口压力，PX＝P3，P3为所述三通压力匹配器第三油口压力；P2为三通压力匹配器第二油口压力。
通过以上数学模型，可以有效调节三通压力匹配器油口的压力和流量。
本发明中，当所述执行元件的负载压力变化，和/或蓄能器进出油压力波动时，调节所述三通压力匹配器第二油口的压力和流量，实现所述三通压力匹配器三个油口压力值与所述执行元件负载压力的匹配。
本发明中，通过控制所述液压泵的排量和控制阀的开度，即可调节所述三通压力匹配器第二油口的压力和流量，控制简单易实现。
为了进一步降低结构复杂度，本发明的控制阀包括多路换向阀；所述多路换向阀压力油口接所述液压泵出口；所述多路换向阀回油口接油箱；所述多路换向阀第一工作油口接所述三通压力匹配器第二油口；所述多路换向阀第二工作油口接所述执行元件第二外接油口。
相应地，本发明还提供了一种挖掘机，该挖掘机上述压力耦合液压混合动力驱动回路。
作为一个发明构思，本发明还提供了一种上述压力耦合液压混合动力驱动回路的控制方法，该方法主要包括：通过调节所述三通压力匹配器第二油口的压力和流量，实现 所述三通压力匹配器三个油口压力值与所述执行元件负载压力的匹配。
如前所示，为了使控制过程简单易实现，可以通过控制液压泵的排量和控制阀的开度，调节所述三通压力匹配器第二油口的压力和流量。
本发明的控制方法中，可以利用以下数学模型，高效地调节三通压力匹配器第二油口的压力和流量：
当液压油从所述三通压力匹配器第二油口、第三油口流向所述三通压力匹配器第一油口时，(PA1+△P)×(q2+q3)＝P2·q2+PX·q3；
当液压油从所述三通压力匹配器第一油口流向第二油口、第三油口时，(PA1-△P)×(q2+q3)＝P2·q2+PX·q3；
其中，q2、q3分别为三通压力匹配器第二油口流量、第三油口流量；△P为三通压力匹配器内能量转换装置进口的压力损失；PA1为执行元件正负载驱动腔或负负载回油腔的负载压力，PA1＝P1，P1为三通压力匹配器第一油口压力；PX为蓄能器油口压力，PX＝P3，P3为所述三通压力匹配器第三油口压力；P2为三通压力匹配器第二油口压力。
与现有技术相比，本发明所具有的有益效果为：
1、本发明回路中蓄能器作为辅助动力源的功能不会因执行元件负载压力的变化而缺失，能有效用于执行元件负载有正负区间变换工况时的节能运行，解决了现有技术中液压泵压力、执行元件的负载压力和蓄能器的液压油压力难以匹配的问题；
2、本发明结构简单，容易实现，故障率低，检修容易；
3、本发明不会产生溢流能量损失和节流能量损失，节能效果好。
附图说明
图1为本发明三通压力匹配器结构示意图；
图2为本发明压力耦合液压混合动力驱动回路结构示意图；
图3为本发明三通压力匹配器三个油口K1、K2、K3处的压力和通过流量示意图；
图4为本发明驱动回路用于驱动液压挖掘机动臂液压缸的示意图；
图5为液压挖掘机动臂液压缸现有技术的驱动回路示意图。
具体实施方式
本发明以液压泵为主动力，蓄能器(充气蓄能器)为辅助动力的液压驱动回路，简称压力耦合液压混合动力驱动回路。压力耦合液压混合动力驱动回路用于执行元件负载有正负区间变换工况时的节能运行。当执行元件承受负负载时，回路可回收负负载对执 行元件做功产生的压力能，而在执行元件驱动正负载时，回路可释放回收的压力能，作为辅助动力源。本发明中，执行元件既可以是液压缸，也可以是液压马达；负负载可以是外力(包含重力)，也可以是执行元件制动时产生的惯性力。
需要注意的是，本发明中，压力耦合液压混合动力驱动回路除包含常规液压系统的变量液压泵、控制阀(多路换向阀或其它相关阀)、油箱和执行元件外，还特别配置有用作辅助动力源的充气式蓄能器、采用压力耦合技术的三通压力匹配器、若干压力传感器和控制器。
充气式蓄能器既可是皮囊式，也可是活塞式；所充气体可以是氮气，也可以是某种惰性气体(例如氦气)。充气式蓄能器的充气压力必须大于正、负负载在执行元件工作腔产生的负载压力。
压力耦合液压混合动力驱动回路能将负负载对执行元件做功时，在执行元件回油腔产生的压力油收入蓄能器储存。该收入储存过程，即使在执行元件回油腔压力低于蓄能器充气压力时也能顺利进行，并且不受负载变换的影响。压力耦合液压混合动力驱动回路，能在执行元件驱动外负载时，将储存于蓄能器的压力油输入执行元件驱动腔，用作辅助动力，实现节能，该过程不受蓄能器压力变化的影响。压力耦合液压混合动力驱动回路具备上述功能的原因是因为配置了采用压力耦合技术的三通压力匹配器。
三通压力匹配器由第一能量转换装置和第二能量转换装置耦合而成。能量转换装置既能通过油口输入液压能，在传动轴上输出机械能；也能在传动轴上输入机械能、通过油口输出液压能。能量转换装置可以是某种液压元件，如液压缸、液压泵、液压马达等。所述液压马达可以是柱塞马达(包括径向和轴向)，也可以是齿轮马达(包括内啮合和外啮合)或叶片马达(包括单作用和双作用)；每台马达既可处于马达工况，也可处于泵工况。以下说明虽然以能量转换装置是液压马达为例，但也适用能量转换装置是其它元件的技术方案。
本发明的实施例中，采用压力耦合技术的三通压力匹配器由两台液压马达(泵)耦合而成。本发明中的耦合包括：(1)联通两台马达某一侧的油口，构成一个公共的外接油口K1，每台马达另一侧的油口K2和K3各自保持独立外接；(2)两台马达的传动轴采用刚性同轴联接，所述同轴联接既可以是内外花键轴同轴联接，也可以是轴与轴套的平键同轴联接，还可以是其它同轴联接方式；(3)两台马达的转向一定相同，但既能正转，也能反转；(4)两台马达的三个外接油口，只要把其中任一油口封堵，马达将不能转动，相当于其它油口也被封堵；(5)两台马达的排量可以相同，也可以不相同。
由两台液压马达(泵)耦合而成的三通压力匹配器的液压职能符号如图1所示。K1、K2、K3为其外接油口，其中K1为公共油口。
包含三通压力匹配器的压力耦合液压混合动力驱动回路，各组成部件的联接模式如图2所示。图中，执行元件的两个外接油口为A1、B1；A1为执行元件承受负负载时的回油口，也是执行元件驱动正负载的进油口；B1为执行元件承受负负载时的进油口。
包含三通压力匹配器的压力耦合液压混合动力驱动回路，各组成部件的联接模式如图2所示。该回路中，执行元件的两个外接油口为A1、B1；A1为执行元件承受负负载时的回油口，也是执行元件驱动正负载的进油口；B1为执行元件承受负负载时的进油口。
上述回路各组成部件的联接模式包括(但不限于)以下各项：(1)多路换向阀压力油口P接变量液压泵的出口，多路换向阀回油口T接油箱，多路换向阀工作油口B接执行元件油口B1(第二外接油口)，工作油口A接三通压力匹配器油口K2；(2)三通压力匹配器油口K3接充气式蓄能器进出油口X，三通压力匹配器油口K1接执行元件油口A1(第一外接油口)；(3)变量液压泵输出的压力油，在多路换向阀操控下，或者通过多路换向阀B口进入执行元件B1口，或者通过多路换向阀A口进入三通压力匹配器油口K2，或者经过多路换向阀T口卸荷；(4)在三通压力匹配器的三个油口处装有压力传感器PU1、PU2、PU3，这些传感器(包括，但不限于上述三个)将在线检测值传送给控制器，用于按压力耦合算法对变量液压泵的排量和多路换向阀的开度进行控制。
在图2所示联接模式下，三通压力匹配器的工作模式为：当液压油从K1口流向K2、K3时，K2油口的马达(图2中的左马达)为马达工况，K3油口的马达(图2中的右马达)为泵工况；当液压油从K2、K3口流向K1时，K2油口的马达(图2中的左马达)为泵工况，K3油口的马达(图2中的右马达)为马达工况。
压力耦合液压混合动力驱动回路的联接模式下，三通压力匹配器的工作模式为：当液压油从K1口流向K2、K3时，K2油口的马达(图2中的左马达)为马达工况，K3油口的马达(图2中的右马达)为泵工况；当液压油从K2、K3口流向K1时，K2油口的马达(图2中的左马达)为泵工况，K3油口的马达(图2中的右马达)为马达工况。
尽管由于某些需要，可以对图2所示的回路进行液压元件及管路的添加，但只要具备上述基本特征，都属于本发明的保护范围。
三通压力匹配器运行时，由于两只马达传动轴的同轴联接，保证了两只马达传动轴 上的机械功率相等。因此，忽略摩擦和内泄漏损失时：两只马达各自进出口间的液压功率差也相等。设三通压力匹配器三个油口K1、K2、K3处的压力和通过流量分别为：P1、q1，P2、q2，P3、q3。如图3所示。则有：P1·q2-P2·q2＝P3·q3-P1·q3；即：P1(q2+q3)＝P2·q2+P3·q3。
由流量连续性原理可知：q1＝q2+q3   (1)
所以液压功率关系式为：P1·q1＝P2·q2+P3·q3   (2)
考虑摩擦和内泄漏损失时，液压功率会有损失，该损失均表现为马达进口的的压力损失△P。△P的值因马达的种类型号及液压油的粘度不同而异，可由试验测得，通常为0.5Mpa左右。此时的液压功率关系式为：
(P1±△P)q1＝P2·q2+P3·q3   (3)
考虑回路的联接模式有：P1＝PA1、P3＝PX，其中PA1为执行元件正负载驱动腔(负负载回油腔)的负载压力，PX为充气式蓄能器进出油压力。
可得：(PA1±△P)q1＝P2·q2+PX·q3   (4)
当液压油从K2、K3口流向K1时，取+号；当液压油从K1口流向K2、K3时，取-号。
联立(1)、(4)式，即得本发明回路中，压力耦合算法的数学模型。
依据上述压力耦合算法的数学模型，本发明的压力耦合液压混合动力驱动回路，当现场工况中，执行元件的负载压力PA1有变化，或蓄能器进出油压力PX有波动时，都可以通过P2值和q2值的调节，来保证蓄能器收放压力油功能的稳定，用于执行元件负载有正负区间变换工况时的节能运行(即保证蓄能器收放压力油功能的稳定)。即：当负负载对执行元件做功时，压力耦合液压混合动力驱动回路能将在执行元件回油腔产生的压力油收入蓄能器储存；该收入储存过程，即使在执行元件回油腔压力低于蓄能器充气压力时也能顺利进行，并且不受负载变换的影响。在执行元件驱动正外负载时，压力耦合液压混合动力驱动回路能将储存于蓄能器的压力油输入执行元件驱动腔，用作辅助动力，实现节能，该过程不受蓄能器压力变化的影响。而P2值和q2值的调节是可以用变量液压泵的排量和多路换向阀的开度进行控制的。通过压力耦合算法，合理调节变量液压泵的排量和多路换向阀的开度，实现三通压力匹配器三个油口压力值与执行元件的负载压力PA1的匹配，保证了本发明回路中充气蓄能器作为辅助动力源的功能不因执行元件负载压力的变化而缺失，能有效用于执行元件负载有正负区间变换工况时的节能运行。
实施例
本发明压力耦合液压混合动力驱动回路用于驱动液压挖掘机动臂液压缸的实际应用系统如图4所示。液压挖掘机动臂液压缸的压力耦合液压混合动力驱动回路包括承受重力负载的动臂缸、三通压力匹配器、充气式蓄能器、多路阀动臂联、变量液压泵、若干压力传感器(P1、P2、P3、PA1、PB1)和控制器。三通压力匹配器的K1油口接动臂缸无杆腔油口A1，K2油口接多路阀动臂联的工作油口A，K3油口接充气式蓄能器的进出油口X，动臂缸有杆腔油口B1接多路阀动臂联的工作油口B，变量液压泵接多路阀的油口P。多路阀动臂联的先导控制油分别是pa7和pb7。
在液压挖掘机的实际工况中，动臂缸要承受液压挖掘机整台动臂和铲斗(含货物)的重量，该重量折算到动臂缸活塞杆端的力为G。当液压挖掘机动臂下降，动臂缸活塞杆缩回时，G为负负载；当液压挖掘机动臂上升，动臂缸活塞杆伸出时，G为正负载。无论动臂上升或下降，若A1为动臂缸无杆腔承压面积、B1为动臂缸有杆腔承压面积，均有动臂缸无杆腔油压PA1＝(G+PB1·B1)/A1。式中，PB1为动臂缸有杆腔油压。图4中，充气式蓄能器的油压PX应比PA1大5-10Mpa左右。
当多路阀动臂联的先导控制油pb7起作用时，多路阀动臂联为左位，变量液压泵输出的压力油经动臂联B口到动臂缸有杆腔油口B1。负负载G驱动动臂缸活塞杆缩回，动臂缸无杆腔回油经油口A1到三通压力匹配器K1口。该回油压力为PA1，回油流量为q1。q1进入三通压力匹配器后，分流为两路，流量q2经左马达出K2口，到多路阀动臂联A口后回油箱。流量q3经右马达出K3口，进入蓄能器储存。此工况下，左马达进口压力P1为PA1，出口压力P2近似为0，是马达工况，输入的液压功率为PA1·q2，输出的机械功率用于驱动右马达。此时，右马达是泵工况，输入左马达提供的机械功率，用于将进口压力PA1提升到P3＝PX；右马达输出的液压功率为(PX-PA1)·q3。设三通压力匹配器的内泄漏和摩擦损失的液压功率表现为压力损失△P，依据能量守恒定律有：
PA1·q2-△P·q1＝(PX-PA1)·q3
即PA1(q2+q3)-△P·q1＝PX·q3   (5)
依据流量连续性方程有：q1＝q2+q3   (6)
(5)式可改写为：PA1·q1-△P·q1＝PX(q1-q2) (7)
q1值由挖掘机动臂下降的速度决定，工况确定后不能随意改变，而q2值由变量泵排量决定，可作为调节参数由控制器依据(6)、(7)式控制。对于某PA1值和PX值，总可以找到一个合适的q2值，使(7)式成立，即使当PX大于PA1时，该q2值也能找到。
(6)、(7)式就是液压挖掘机动臂下降工况的压力耦合算法的数学模型。
当多路阀动臂联的先导控制油pa7起作用时，多路阀动臂联为右位，变量液压泵输出的压力油经动臂联A口到三通压力匹配器K2口，蓄能器储存压力油经三通压力匹配器K2口进入右马达，右马达出口压力为PA1。此时，右马达是马达工况，输入的液压功率为(PX-PA1)·q3，输出的机械功率驱动左马达，将K2口的进油压力由P2升为PA1，左马达为泵工况。由能量守恒定律和流量连续性方程同理可得：
(PA1-P2)·q2+△P·q1＝(PX-PA1)·q3
PA1·q1-P2·q2+△P·q1＝PX(q1-q2)(8)
(6)、(8)式就是液压挖掘机动臂上升工况的压力耦合算法的数学模型。控制器依据(6)、(8)式调节P2或q2，就可实现对确定的PA1和PX的匹配。
通常，液压挖掘机动臂液压缸现在应用的驱动回路如图5所示。本发明压力耦合液压混合动力驱动回路用于驱动液压挖掘机动臂液压缸可以比图5所示的现有回路明显减少液压泵的能耗，实现节能。设动臂液压缸上升下降的行程均为L，时间均为t。
在动臂下降工况，两种回路中，动臂液压缸有杆腔的压力PB1均很小，动臂液压缸无杆腔的压力PA1用于平衡重力G，PA1＝G/A1，A1为无杆腔承压面积。此时液压泵的输出压力均为3-5Mpa，两种回路的能耗基本相同。所不同的是：现有回路中，动臂液压缸无杆腔压力为PA1的回油经多路阀回油箱，压力能变为热能浪费了。本发明回路中，动臂液压缸无杆腔压力为PA1的回油经三通压力匹配器后，流量为q2的压力油驱动左马达对右马达做功，使流量为q3的油压力由PA1升高到PX，并收入蓄能器储存。因此，在动臂下降工况，压力耦合液压混合动力驱动回路中，动臂液压缸无杆腔压力为PA1的回油，其压力能并没有像现有回路那样变为热能浪费了，而是得到了回收储存，回收压力能的理论值为Wx＝(PX-PA1)·q3·t。
在动臂上升工况，两种回路中，动臂液压缸无杆腔压力均为PA1，图5所示现有回路的进入无杆腔的流量qA也和本发明回路的流量q1相同。即，两种回路中进入动臂液压缸无杆腔的液压能Wi基本相等，Wi＝(G/A1)·q1·t＝PA1·q1·t。但是，图5所示的现有回路中，Wi全部由液压泵提供；而本发明回路中，Wi由液压泵和作为辅助动力的蓄能器共同提供。若忽略三通压力匹配器的能量损失，蓄能器可将动臂下降时回收储存的液压能Wx＝(PX-PA1)·q3·t全部提供给动臂液压缸无杆腔，此时，液压泵提供液压能只需(Wi-Wx)即可。所以，从理论上分析，本发明压力耦合液压混合动力驱动回路，在动臂下降上升的一个工作循环中，即可节省液压泵的能耗Wx＝(PX-PA1)·q3·t。对 一台35吨的液压挖掘机而言，Wx约为180-220千焦，节能效果相当明显。
尽管由于某些需要，可以对图4所示的回路进行液压元件及管路的添加，可以有其它形式的挖掘机液压系统组合，可以用于挖掘机其它执行元件的驱动，但只要具备本发明压力耦合液压混合动力驱动回路的基本特征(两台能量转换装置耦合而成的三通压力匹配器、压力匹配器三油口在回路中的联接模式、压力耦合算法的数学模型及控制方法)，都属于本发明的实施应用，是本发明的保护范围。

Claims (10)

  1. 一种压力耦合液压混合动力驱动回路，其特征在于，包括三通压力匹配器，所述三通压力匹配器的第一外接油口接执行元件的第一油口；所述三通压力匹配器第二油口、执行元件第二外接油口通过控制阀接液压泵和油箱；所述三通压力匹配器第三油口接蓄能器油口；所述三通压力匹配器包括第一能量转换装置和第二能量转换装置；所述第一能量转换装置、第二能量转换装置一侧的油口连通后形成所述三通压力匹配器的第一油口；所述第一能量转换装置另一侧的油口、第二能量转换装置另一侧的油口分别为所述三通压力匹配器的第二油口、第三油口；所述第一能量转换装置的传动轴与所述第二能量转换装置的传动轴刚性同轴连接，且所述第一能量转换装置和第二能量转换装置的运动方向相同。
  2. 根据权利要求1所述的压力耦合液压混合动力驱动回路，其特征在于，所述第一能量转换装置与所述第二能量转换装置均为液压马达，两台所述液压马达转向相同；优选地，所述液压马达处于马达工况或泵工况；优选的，所述液压马达为柱塞马达、齿轮马达、叶片马达中的一种；优选的，所述柱塞马达包括径向柱塞马达和轴向柱塞马达；所述齿轮马达包括内啮合齿轮马达和外啮合齿轮马达；所述叶片马达包括单作用叶片马达和双作用叶片马达。
  3. 根据权利要求1或2所述的压力耦合液压混合动力驱动回路，其特征在于，所述三通压力匹配器第一油口、第二油口、第三油口处均安装有压力检测装置；优选地，所有压力检测装置、液压泵、控制阀均与控制器电连接。
  4. 根据权利要求1～3之一所述的压力耦合液压混合动力驱动回路，其特征在于，所述三通压力匹配器三个油口满足以下数学模型：
    当液压油从所述三通压力匹配器第二油口、第三油口流向所述三通压力匹配器第一油口时，(PA1+△P)×(q2+q3)＝P2·q2+PX·q3；
    当液压油从所述三通压力匹配器第一油口流向第二油口、第三油口时，(PA1-△P)×(q2+q3)＝P2·q2+PX·q3；
    其中，q2、q3分别为三通压力匹配器第二油口流量、第三油口流量；△P为三通压力匹配器内能量转换装置进口的压力损失；PA1为执行元件正负载驱动腔或负负载回油腔的负载压力，PA1＝P1，P1为三通压力匹配器第一油口压力；PX为蓄能器油口压力，PX＝P3，P3为所述三通压力匹配器第三油口压力；P2为三通压力匹配器第二油口压力。
  5. 根据权利要求1～4之一所述的压力耦合液压混合动力驱动回路，其特征在于，当所述执行元件的负载压力变化，和/或蓄能器进出油压力波动时，调节所述三通压力匹配器第二油口的压力和流量，实现所述三通压力匹配器三个油口压力值与所述执行元件负载压力的匹配。
  6. 根据权利要求5所述的压力耦合液压混合动力驱动回路，其特征在于，通过控制所述液压泵的排量和控制阀的开度，调节所述三通压力匹配器第二油口的压力和流量。
  7. 根据权利要求1～6之一所述的压力耦合液压混合动力驱动回路，其特征在于，所述控制阀包括多路换向阀；所述多路换向阀压力油口接所述液压泵出口；所述多路换向阀回油口接油箱；所述多路换向阀第一工作油口接所述三通压力匹配器第二油口；所述多路换向阀第二工作油口接所述执行元件第二外接油口。
  8. 一种挖掘机，其特征在于，该挖掘机采用权利要求1～7之一所述的压力耦合液压混合动力驱动回路。
  9. 一种权利要求1～7之一所述压力耦合液压混合动力驱动回路的控制方法，其特征在于，该方法主要包括：通过调节所述三通压力匹配器第二油口的压力和流量，实现所述三通压力匹配器三个油口压力值与所述执行元件负载压力的匹配；优选地，通过控制液压泵的排量和控制阀的开度，调节所述三通压力匹配器第二油口的压力和流量。
  10. 根据权利要求9所述的控制方法，其特征在于，利用以下数学模型调节三通压力匹配器第二油口的压力和流量：
    当液压油从所述三通压力匹配器第二油口、第三油口流向所述三通压力匹配器第一油口时，(PA1+△P)×(q2+q3)＝P2·q2+PX·q3；
    当液压油从所述三通压力匹配器第一油口流向第二油口、第三油口时，(PA1-△P)×(q2+q3)＝P2·q2+PX·q3；
    其中，q2、q3分别为三通压力匹配器第二油口流量、第三油口流量；△P为三通压力匹配器内能量转换装置进口的压力损失；PA1为执行元件正负载驱动腔或负负载回油腔的负载压力，PA1＝P1，P1为三通压力匹配器第一油口压力；PX为蓄能器油口压力，PX＝P3，P3为所述三通压力匹配器第三油口压力；P2为三通压力匹配器第二油口压力。
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