JP3676635B2 - Pressure control method and pressure control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a pressure control method and a pressure control apparatus using a pilot valve and a main valve.
[0002]
[Prior art]
  FIG. 15 shows a separate meter-in / meter-out control circuit provided in a conventional construction machine such as a hydraulic excavator, for example, a variable displacement pump 1 and a cylinder-type fluid pressure actuator 2 that drives a load W. Are provided with a bridge circuit 3 composed of two meter-in valves A1IMV and A2IMV and two meter-out valves A3IMV and A4IMV.
[0003]
  Further, a load hold check valve 4 is provided in a passage between the pump 1 and the bridge circuit 3, and a drift reduction valve (a leak prevention valve (for preventing leakage) is provided in two passages between the bridge circuit 3 and the fluid pressure actuator 2. Pilot operated check valves) 5 are provided.
[0004]
  In addition, a bridge circuit (not shown) for controlling another fluid pressure actuator (not shown) is similarly connected to the discharge port of the pump 1 by a passage 6.
[0005]
  Furthermore, between the discharge port of the pump 1 and the tank 7, there is one common bypass valve 8 that is controlled in conjunction with the control of the bridge circuit 3 of the plurality of fluid pressure actuators 2, and the pump discharge pressure. A main relief valve 9 to be set is provided.
[0006]
  Meter-in valves A1IMV and A2IMV, meter-out valves A3IMV and A4IMV, and common bypass valve 8 are usually spool valve type open / close valves with an intermediate throttle notch. The spool valve stroke is controlled by a push solenoid operated by the output electric signal.
[0007]
  In this circuit, for example, when the fluid pressure actuator 2 is extended against the load W, the drift reduction valve 5 is opened and the meter-in valve A1IMV and the meter-out valve A4IMV are closed, and the discharge of the variable displacement pump 1 is performed. The amount is gradually increased, the common bypass valve 8 is gradually closed, and the meter-in valve A2IMV and the meter-out valve A3IMV are controlled to open gradually.
[0008]
  On the other hand, when contracting the fluid pressure actuator 2, the drift reduction valve 5 is opened, the meter-in valve A2IMV and the meter-out valve A3IMV are closed, and the discharge amount of the variable displacement pump 1 is gradually increased. The common bypass valve 8 is gradually closed and the meter-in valve A1IMV and the meter-out valve A4IMV are controlled to open gradually. Such control is performed via a controller by an operating lever (not shown).
[0009]
  As shown in FIG. 16, conventionally, the load pressure of the fluid pressure actuator 2 is detected by the pressure sensor 10A, and the control valve such as the meter-in valve A2IMV is electrically controlled by the controller 10B (the opening area is reduced). Thus, the load pressure controlled by the control valve does not exceed a preset pressure.
[0010]
[Problems to be solved by the invention]
  However, there is a risk that the control system may become unstable due to a delay in the calculation of feedback, and it takes time to stabilize.
[0011]
  The present invention has been made in view of these points, and an object thereof is to improve stability in pressure control.
[0012]
[Means for Solving the Problems]
  In the first aspect of the invention, the pilot flow is controlled by the pilot valve to pilot the main flow control main valve, the load pressure of the main flow is fed back to the pilot valve, and the pilot pressure is increased by increasing the load pressure. The valve is displaced in the direction of decreasing the pilot flow rate, and by reducing the pilot flow rate, the main valve is controlled in the direction of decreasing the main flow rate to reduce the load pressure and act on the pilot valve from the direction opposite to the load pressure fed back to the pilot valve. This is a pressure control method that adjusts the load pressure by controlling the thrust from the outside, and the feedback force by the load pressure when raising the thrust from the outsideIn response to theThis is a pressure control method for temporarily reducing the thrust.
[0013]
  When the load pressure increases, the load pressure is directly fed back to the pilot valve, the pilot valve is displaced in the pilot flow rate decreasing direction by the feedback force, and the pilot valve displacement controls the main valve in the main flow rate decreasing direction. Since the pressure decreases with good response, high-load driving is prevented, fluctuations in the load pressure are suppressed, and instability due to a delay in calculation of feedback does not occur. Further, the load pressure to be driven is adjusted by adjusting the thrust against the load pressure. In particular, the feedback force due to the load pressure when raising the thrust against the load pressureIn response to theBy temporarily reducing the thrust, the pilot valve returns toward the neutral position with good response and stabilizes the control system.
[0014]
  According to the second aspect of the present invention, a pilot valve for controlling a pilot flow rate, a main valve for main flow rate control pilot operated by the pilot valve, and a load pressure of the main flow rate are fed back to the pilot valve to increase the load pressure. The pilot valve is displaced in the pilot flow rate decreasing direction and the main valve is controlled in the main flow rate decreasing direction to reduce the load pressure, and the pilot valve acts from the direction opposite to the load pressure fed back to the pilot valve. A pressure control device having a driving means for adjusting the load pressure by controlling the thrust force, and a feedback force due to the load pressure when the thrust of the driving means is raisedIn response to theThe pressure control device includes a controller that temporarily reduces the thrust of the driving means.
[0015]
  When the load pressure increases, the load pressure is directly fed back to the pilot valve by the load pressure feedback mechanism, and the pilot valve is displaced in the pilot flow rate decreasing direction by the feedback force, and thereby the main valve is displaced in the main flow rate decreasing direction. Therefore, high load driving is prevented, fluctuation of load pressure is suppressed, stability is ensured, and the pilot valve drive means is controlled to counter the load pressure. The load pressure to be driven is adjusted by adjusting the thrust of the driving means. In particular, the feedback force due to load pressure when the thrust of the drive means is raised by the controller.In response to theBy temporarily reducing the thrust of the driving means, the pilot valve is returned to the neutral position with good response by the load pressure, and the control system is stabilized.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0017]
  First, an embodiment shown in FIGS. 1 and 2 will be described. The same parts as those in the conventional control circuit shown in FIG.
[0018]
  Fig. 2 shows a meter-in / meter-out separated control circuit composed of a bridge circuit 3 combining meter-in valves A1IMV and A2IMV as control valves and meter-out valves A3IMV and A4IMV as control valves. A pump discharge passage 11 is connected to a discharge port of a variable displacement pump 1 whose discharge flow rate can be variably controlled by a pump swash plate 1a. A bridge for controlling one fluid pressure actuator 2 is connected to the pump discharge passage 11. Passages 12 and 13 communicating with the two meter-in valves A1IMV and A2IMV of the circuit 3 are connected to the pump discharge passage 11 and another bridge circuit 3a for controlling another fluid pressure actuator 2a. A communicating passage 6 is also connected.
[0019]
  Furthermore, a common bypass valve 8 for controlling the supply amount of the working fluid discharged from the pump 1 to the bridge circuits 3 and 3a, and a main relief valve 9 for setting an upper limit of the pump discharge pressure are provided at the discharge port of the pump 1. Is provided in common for the plurality of bridge circuits 3 and 3a.
[0020]
  One bridge circuit 3 will be described. Two meter-in valves A1IMV and A2IMV are connected to the pump discharge passage 11 via passages 12 and 13, respectively. These meter-in valves A1IMV and A2IMV are connected to the fluid pressure actuator 2. Two meter-out valves A3IMV and A4IMV for controlling between the passages 14 and 15 and the tank passages 16 and 17 are connected to each other, and the tank passages 16 and 17 are connected to the tank 7.
[0021]
  Further, the passage 14a drawn through the meter-in valve A1IMV and the meter-out valve A3IMV shown on the upper side of the bridge circuit 3 is a chamber in which the rod side is located from the piston 2p of the fluid pressure actuator 2 (hereinafter referred to as “rod side chamber”). 2r "), and the passage 15a drawn through the meter-in valve A2IMV and meter-out valve A4IMV shown on the lower side is a chamber (head side) from the piston 2p of the fluid pressure actuator 2. Hereinafter, it is connected to “head side chamber 2h”).
[0022]
  The meter-out valves A3IMV and A4IMV will be described with reference to FIG. 1 and FIG. The main poppets 22 are provided in the valve chambers 23 respectively formed in the valve housing 21 so as to be axially displaceable, and return passages 14a and 15a from the fluid pressure actuator 2 communicate with the valve chambers 23, respectively. Has been.
[0023]
  On the side surface portion of the main poppet 22 on the meter-out side, a variable slot 25 is formed in the axial direction in which the opening area of each main poppet 22 increases in proportion to the axial displacement. ing.
[0024]
  These variable slots 25 are respectively provided with spring chambers 28 formed in the valve housing 21 in a state in which a drain flow control unit 26 formed at the opposite end of each main poppet 22 is seated on the seat 27. It has a slight opening 25a communicating therewith. Each seat 27 communicates with the tank 7 through tank passages 16 and 17.
[0025]
  Each spring chamber 28 for the meter-out side main poppet 22 includes a compression coil-like return spring 29 that presses the drain flow rate control unit 26 toward the seat 27, that is, in the closing direction.
[0026]
  Further, as means for controlling the opening degree of each main poppet 22, a passage 31 and a passage 32 that can communicate with each other through the seat 30 are drawn from the spring chambers 28 to the tank passages 16 and 17, respectively. The pilot spools 33 serving as pilot valves are respectively interposed in the pilot spools 33. The pilot spools 33 perform drain control of the spring chambers 28 in response to an electric signal from a controller (not shown). A return spring 34 in the spring chamber 24 urged to a position (closed position) and a push solenoid 35 as drive means for driving the pilot spool 33 against the return spring 34 are provided.
[0027]
  When the displacement of the pilot spool 33 is a minute displacement below the dead band near the neutral position, the flow rate through the seat 30 is zero.
[0028]
  Return passages 14a and 15a from the fluid pressure actuator 2 are connected to the pilot spools 33 of the meter-out valves A3IMV and A4IMV by passages 36, respectively, and have a relief function to be described later against excessive load pressure.
[0029]
  As shown in FIG. 1, the push solenoid 35 includes an exciting coil 35 a and a movable iron core 35 b integrated on the upper part of the pilot spool 33.
[0030]
  Each of the meter-out valves A3IMV and A4IMV has a pilot spool 33 formed with a load pressure sensing portion 38 having a large diameter, and a load pressure chamber 39 formed above the load pressure sensing portion 38, respectively. Return passages 14a and 15a from the fluid pressure actuator 2 are connected to the chamber 39 by passages 36, respectively.
[0031]
  A load pressure feedback mechanism is formed by the passage 36 that guides the load pressure, the load pressure chamber 39, and the load pressure sensing unit 38 of the pilot spool 33 that receives the load pressure.
[0032]
  As a result, when an excessive load pressure is generated in the return passages 14a and 15a from the fluid pressure actuator 2, the load pressure is guided to the load pressure chamber 39 and presses the load pressure sensing unit 38 downward in the figure. The seat 30 is opened, and the spring chamber 28 is decompressed and the main poppet 22 is lifted, thereby providing a relief function for communicating the valve chamber 23 with the tank 7.
[0033]
  A displacement sensor 40 for detecting the axial stroke of the pilot spool 33 is attached to the upper side of the push solenoid 35. In this displacement sensor 40, a coil 40a is mounted on a push solenoid 35 via a sensor mounting cylinder 40b, and a core 40c that moves integrally with the movable iron core 35b is fitted inside the sensor mounting cylinder 40b. The axial displacement amount of the core 40c, that is, the axial displacement amount of the pilot spool 33 is detected by the coil 40a.
[0034]
  The pilot spool 33, the movable iron core 35b, and the core 40c are provided with drain holes 37 for discharging the working fluid over the entire length.
[0035]
  In each of the meter-out valves A3IMV and A4IMV configured as described above, a part of the return flow Q from the fluid pressure actuator 2 flows into the spring chamber 28 through the opening 25a of the pilot variable slot 25. The stroke control of the main poppet 22 is achieved by opening control of the seat 30 communicated with the spring chamber 28 by the pilot spool 33, and the flow rate passing through the pilot spool 33 is q.
[0036]
  By the stroke control of the main poppet 22 on the meter-out side, the drain flow rate control unit 26 controls the opening degree of the seat 27, so the main flow rate LQ is controlled, and this main flow rate LQ is controlled as if by the pilot spool 33. The pilot flow q is amplified.
[0037]
  On the other hand, when the pilot spool 33 is closed and the flow rate q and the main flow rate LQ are both zero, the return pressures of the return passages 14a and 15a from the fluid pressure actuator 2 rise, and pass through the passage 36 to the pilot spool. When the sum of the force acting on the load pressure sensing portion 33 of 33 and the thrust of the push solenoid 35 overcomes the urging force of the return spring 34, the pilot spool 33 is displaced and the seat 30 opens, and the pilot flow rate q is When the flow starts, a differential pressure is generated before and after the opening 25a of the variable slot 25 of the main poppet 22 on the meter-out side, the main poppet 22 moves to the spring chamber 28 side, the seat 27 opens, and the main flow rate LQ is generated. Thus, the return pressure of the return passage 14a or 15a from the fluid pressure actuator 2 is suppressed from rising abnormally, and the compression coil-shaped return spring 34 and the pusher acting on the pilot spool 33 are pushed. It has a relief valve function to settle at a certain pressure value set by the thrust of the solenoid 35.
[0038]
  Next, the meter-in valves A1IMV and A2IMV will be described. The meter-in valves A1IMV and A2IMV are configured around a pilot flow rate amplification type main poppet 41 as a main valve provided in the valve housing 21, and this point is a meter-out valve. Although it is the same as A3IMV and A4IMV, the structure of the main poppet 41 itself and its pilot control means are different from the meter-out valves A3IMV and A4IMV.
[0039]
  Since the structures of the meter-in valves A1IMV and A2IMV are the same, here, the meter-in valve A2IMV on the cylinder head side will be described in detail as an example.
[0040]
  As shown in FIG. 2, the main poppet 41 on the meter-in side has a shuttle valve 42 as a high-pressure selection means inside, and a passage 43 formed on one inlet side of the shuttle valve 42 is connected to the pump 1. Opened in a passage 13 communicated with the discharge port via a pump discharge passage 11, the pump discharge pressure is guided to the shuttle valve 42, and the passage 44 formed on the other inlet side of the shuttle valve 42 is a fluid pressure actuator. 2 is opened to an annular space 45 communicated with the head side chamber 2h via the passage 15, and the pressure supplied to the fluid pressure actuator 2 or the load pressure of the fluid pressure actuator 2 is led to the shuttle valve 42. The high pressure side is selected from among the pressures.
[0041]
  A passage 46 in the main poppet 41 formed on the output side of the shuttle valve 42 communicates with a variable slot 47 that is machined in the axial direction on the peripheral surface of the main poppet 41. The opening area of the variable slot 47 increases in accordance with the movement stroke of the main poppet 41.
[0042]
  The variable slot 47 has a slight opening 47a communicating with a spring chamber 51 as a pressure chamber formed in the valve housing 21 in a state where the flow control unit 48 of the main poppet 41 is seated on the seat 49. It is.
[0043]
  The spring chamber 51 for the main poppet 41 is provided with a compression coil-shaped return spring 52 that presses the flow control unit 48 of the main poppet 41 against the seat 49. The spring chamber 51 is provided as a pilot valve by a passage 53. The pilot spool 54 communicates.
[0044]
  As shown in FIG. 1, the pilot spool 54 is slidably fitted into a fitting hole 55 formed in the valve housing 21, and the pilot spool 54 opens and closes the tip of the fitting hole 55. A seat 56 is provided.
[0045]
  The pilot spool 54 is stroke-controlled by a push solenoid 57 as an external driving means. The push solenoid 57 is configured such that a movable iron core 57b integrated with an upper end portion of the pilot spool 54 is movably fitted in a coil 57a installed on the valve housing 21, and energizes the coil 57a. As a result, it is possible to obtain an exciting force that urges the pilot spool 54 in the direction in which the pilot spool 54 is pushed into the valve housing 21 (the direction in which the pilot spool 54 opens from the seat 56).
[0046]
  The lower end of the pilot spool 54 shown in the figure is inserted into a spring chamber 61 formed in the valve housing 21, and the pilot spool 54 is returned upward in the drawing by a compression coil-shaped return spring 62 provided in the spring chamber 61. The urging force to be applied is given.
[0047]
  The spring chamber 61 communicates with the check valve 64 through a passage 63 and further communicates with the passage 15 through a passage 65.
[0048]
  A land portion 68 and a poppet portion 69 are formed in a relatively lower portion of the pilot spool 54 via a circumferential groove 66, and the poppet portion 69 is locked to the seat 56 in a neutral position.
[0049]
  When the displacement of the pilot spool 54 is a minute displacement below the dead band near the neutral position, the flow rate through the seat 56 becomes zero.
[0050]
  An annular groove 71 that always opens in the circumferential groove 66 is formed in the fitting hole 55, and the spring chamber 51 of the main poppet 41 on the meter-in side is communicated with the annular groove 71 through the passage 53.
[0051]
  In addition, a large-diameter load pressure sensing unit 77 is formed in a relatively upper part of the pilot spool 54, and a load is fitted on the lower side of the load pressure sensing unit 77 in the figure by a fitting hole that fits the load pressure sensing unit 77. A pressure chamber 78 is formed, and the load pressure chamber 78 is communicated with the passage 65 by a passage 79. The upper portion of the load pressure sensing unit 77 is communicated with the tank 7 by a passage 81.
[0052]
  A load pressure feedback mechanism is formed by the passage 79 that guides the load pressure, the load pressure chamber 78, and the load pressure sensing unit 77 of the pilot spool 54 that receives the load pressure.
[0053]
  The pilot spool 54 is provided with a displacement sensor 82 as an opening area monitoring means that can monitor the opening area of the pilot spool 54 by detecting its operating stroke.
[0054]
  In the displacement sensor 82, a coil 82a is mounted on the push solenoid 57 via a sensor mounting cylinder 82b, and a core 82c that moves integrally with the movable iron core 57b is fitted inside the sensor mounting cylinder 82b. The axial displacement amount of the core 82c, that is, the axial displacement amount of the pilot spool 54 is detected by the coil 82a.
[0055]
  Further, a drain hole 83 for discharging the working fluid is formed through the entire length of the pilot spool 54, the movable iron core 57b, and the core 82c.
[0056]
  The main poppet 22 and the pilot spool 33 constitute one control valve, and the main poppet 41 and the pilot spool 54 constitute the other control valve.
[0057]
  In the meter-in valves A1IMV and A2IMV configured in this way, when the push solenoid 57 is excited and moves in the direction in which the pilot spool 54 is pushed against the spring force of the return spring 62, the poppet portion of the pilot spool 54 Since 69 opens the seat 56, the spring chamber 51 of the main poppet 41 has a passage 53, an annular groove 71, a circumferential groove 66, a seat 56, a spring chamber 61 of the pilot spool 54, a passage 63, a check valve 64 and a passage 65. Then, the fluid pressure actuator 2 communicates with the passage 15, the spring chamber 51 is pressure-reduced according to the displacement amount of the pilot spool 54, the stroke control is performed so that the main poppet 41 is opened, and the passage 49 passes through the seat 49. The main flow rate flowing out into the passage 15 is as if the pilot flow rate controlled by the pilot spool 54 is amplified.
[0058]
  As shown in FIG. 2, reference numeral 86 denotes a controller mounted on a construction machine such as a hydraulic excavator, and an operation lever 87 for issuing a command signal to each actuator 2 and 2a to the input terminal of the controller 86, a pump discharge passage. 11 is connected to the pump pressure sensor 88 for detecting the pump discharge pressure, the displacement sensor 82 of the meter-in valves A1IMV and A2IMV, and the displacement sensor 40 of the meter-out valves A3IMV and A4IMV. , Meter-in valves A1IMV and A2IMV push solenoid 57 and meter-out valves A3IMV and A4IMV push solenoid 35 are connected to each other, and the command signal input from the operating lever 87 is processed by the controller 86, and the meter-in valves A1IMV and A2IMV and meter-out valves A3IMV and A4IMV as described below Controlled by optimal conditions.
[0059]
  FIG. 3 is a block diagram showing a combined pressure / flow rate control system for the meter-in valve A2IMV that supplies hydraulic oil from the pump 1 to the head side chamber 2h of the fluid pressure actuator 2. This control system is a lever of the operating lever 87. A three-dimensional map 91 showing the relationship between the operation amount L, the flow rate Q controlled by the main poppet 41, that is, the actuator speed, and the load pressure P, that is, the actuator operating force is provided.
[0060]
  The three-dimensional map 91 can obtain the corresponding flow rate Q by inputting the lever operation amount L and the load pressure P, and can also correspond by inputting the lever operation amount L and the flow rate Q. The load pressure P can be obtained.
[0061]
  The curve on the LQ plane indicates the flow rate characteristic at the time of no load, that is, the velocity modulation characteristic, and the curve on the L-P plane indicates the pressure characteristic, that is, the force modulation characteristic in the stall state where the fluid pressure actuator 2 cannot move due to the load. In general, a load pressure P or a flow rate Q corresponding to the lever operation amount L on the curved surface between them is used.
[0062]
  A solid line drawn from the three-dimensional map 91 indicates the flow rate Q, and a dotted line indicates the load pressure P.
[0063]
  This control system includes a load pressure P of the fluid pressure actuator 2 without using a pressure sensor._loadIs provided. As will be described in detail later, this load pressure calculation device 92 is mainly based on the driving current I supplied to the push solenoid 57 of the pilot spool 54 on the meter-in side and the displacement amount X detected by the displacement sensor 82 or on the meter-out side. From the drive current I supplied to the push solenoid 35 of the pilot spool 33 and the displacement amount X detected by the displacement sensor 40, the load pressure P_loadIs estimated.
[0064]
  The flow rate Q controlled by the main poppet 41 can be expressed by the following formula 1.
[0065]
[Formula 1]
Q = α ・ A ・ (P_P-P_load)^1/2
[0066]
  Here, α is a constant, A is the opening area between the flow control unit 48 and the seat 49 of the main poppet 41, P_PIs the pump discharge pressure detected by the pump pressure sensor 88, P_loadIs the load pressure.
[0067]
  From Expression 1, the opening area A of the main poppet 41 is expressed by the following Expression 2.
[0068]
[Formula 2]
A = Q / {α · (P_P-P_load)^1/2}
[0069]
  Accordingly, when the required flow rate value Q output from the three-dimensional map 91 is given by inputting the lever operation amount L with the operation lever 87, the pump discharge pressure P detected by the pump pressure sensor 88 is given._PAnd the load pressure P estimated with high accuracy by the load pressure calculation device 92_loadThus, the opening area A of the main poppet 41 can be calculated.
[0070]
  The opening area A of the main poppet 41 and the displacement X of the main poppet 41_PIs a predetermined relationship designed in advance, and when the relationship is expressed by a function, X_P= F (A), which is indicated by function 93 in FIG.
[0071]
  Displacement amount X of main poppet 41_PIs determined, flow rate value Q, pump discharge pressure P_P, Load pressure P_loadThe amount of displacement X of the main poppet 41_PThe displacement amount X of the pilot spool 54 for realizing_CX_C= F (X_P).
[0072]
  This displacement X_CIs used as a target value, and an error from the actual displacement amount X of the pilot spool 54 detected by the displacement sensor 82 is calculated by the comparator 95, and two types of variable adjustable gain K are used for the error._iAnd gain K_PAnd the result is input to the adder 96.
[0073]
  Gain K_iAnd gain K_PThe gain adjustment device 97 variably adjusts the spring constant of the return spring 62 of the pilot spool 54 relative to the load pressure P by adjusting the current value I supplied to the push solenoid 57 by gain adjustment._loadIt can change arbitrarily according to.
[0074]
  That is, since the push solenoid 57 and the return spring 62 act in the opposite directions with respect to the pilot spool 54, for example, when the return spring 62 needs to be strengthened, the current value I to the push solenoid 57 is supplied by the gain adjusting device 97. Gain K to determine_iAnd gain K_PBy adjusting so as to reduce the thrust of the push solenoid 57, the same effect as when the spring constant of the return spring 62 is relatively increased and strengthened can be obtained.
[0075]
  The gain adjusting device 97 directly determines the gain K of the flow control system._iAnd gain K_PThus, there is also a function of adjusting the balance with the pressure control system such as the next pressure control device 98.
[0076]
  The adder 96 also receives a signal that has passed through the pressure controller 98 and the feedforward controller 99.
[0077]
  The pressure control device 98 includes a pressure feedback controller 101 and a work load estimation device 102.
[0078]
  The pressure feedback controller 101 has a load pressure P estimated by the load pressure calculation device 92._loadFor example, the load pressure P is controlled by controlling the current value supplied to the push solenoid 57._loadIt is possible to achieve stability of the control system by controlling the pressure so that does not exceed the set pressure.
[0079]
  For example, when the front working device of a hydraulic excavator is operating, the work load estimating device 102 estimates the load pressure of the boom cylinder or the like, and the load pressure P estimated by the load pressure calculating device 92 is used._loadHowever, on the assumption that not only the pure work load (static load of the load) but also the inertia load of the front work equipment is removed, by removing the influence of the inertia load, The work load is accurately estimated.
[0080]
  The feedforward controller 99 is installed in order to improve the possibility that the control system becomes unstable due to calculation delay of the feedback control system.
[0081]
  Next, the operation of the embodiment shown in FIGS. 1 and 2 will be described.
[0082]
  When the operation lever 87 is operated, a command electric signal transmitted from the operation lever 87 is processed by the controller 86, and the common bypass valve 8 is gradually closed by an electric signal such as a current value output from the controller 86. At the same time, the pump discharge amount gradually increases by controlling the pump swash plate 1a.
[0083]
  At the same time, a command signal (current) corresponding to the amount of operating lever is supplied from the controller 86 to the push solenoid 57 of the meter-in valves A1IMV and A2IMV or the push solenoid 35 of the meter-out valves A3IMV and A4IMV, and the push solenoid 57 to which the current is supplied , 35 generates a thrust, and the pilot spools 54, 33 are displaced against the spring force of the return springs 62, 34, thereby generating a pilot flow rate.
[0084]
  As a result, the spring chamber 51 or the spring chamber 28 is depressurized, the meter-in side main poppet 41 or the meter-out side main poppet 22 is lifted, and the pump 1 moves to one of the rod side chamber 2r and the head side chamber 2h of the fluid pressure actuator 2. The hydraulic oil that is supplied and discharged from the other to the tank 7 is controlled by a bridge circuit 3 formed by two meter-in valves A1IMV and A2IMV and two meter-out valves A3IMV and A4IMV.
[0085]
  For example, the meter-in valves A1IMV and A2IMV displace the pilot spool 54 against the return spring 62 by the push solenoid 57 and open the seat 56, whereby the passages 13, 43, 46, the opening 47a of the variable slot 47, When a pilot flow to the passage 15 through the spring chamber 51, the passage 53, the seat 56, the spring chamber 61, the passage 63, the check valve 64, and the passage 65 occurs, a differential pressure is generated before and after the opening 47a of the variable slot 47. Due to the differential pressure, the main poppet 41 is displaced against the return spring 52, the seat 49 of the main poppet 41 is opened, and the working fluid (pressure oil) that has passed through the passages 11 to 13 and 15 is the head of the fluid pressure actuator 2. Supply to side chamber 2h, load pressure P_loadWill occur.
[0086]
  During work, the load pressure P in the head side chamber 2h_loadWhen the pressure rises, the lower stepped portion of the load pressure sensing portion 77 facing the load pressure chamber 78 of the pilot spool 54 increases the raised load pressure P_loadIn response, the pilot spool 54 is displaced toward the neutral position on the upper side in the figure, and the opening degree of the poppet portion 69 relative to the seat 56 is reduced.
[0087]
  As a result, the pressure in the spring chamber 51 on the main poppet 41 is increased, the pressure difference acting on the upper and lower surfaces of the main poppet 41, that is, the differential pressure is reduced, and the main poppet 41 is moved in the closing direction by the restoring force of the return spring 52. Acts to prevent high-load driving, and the load pressure P_loadLoad pressure P fed back to the load pressure chamber 78 even if_loadAs a result, the pilot spool 54 is immediately returned to the neutral position side, and accordingly, the main poppet 41 is also immediately returned to the neutral position side, and the load pressure decreases with good response, so that fluctuations in the load pressure can be suppressed. This pressure control will be further described later.
[0088]
  On the other hand, the meter-out valves A3IMV and A4IMV displace the pilot spool 33 against the return spring 34 by the push solenoid 35 and open the seat 30, thereby opening the passage 15a, the opening 25a of the variable slot 25, the spring chamber 28, When a pilot flow to the tank 7 through the passage 31, the seat 30, the spring chamber 24, the passage 32, and the tank passage 17 is generated, a differential pressure is generated before and after the opening 25a of the variable slot 25, and the differential pressure causes the main poppet 22 to move. The seat 27 of the main poppet 22 is displaced against the return spring 29, and the working fluid (pressure oil) passing through the passage 15 a, the seat 27 and the tank passage 17 from the head side chamber 2 h of the fluid pressure actuator 2 enters the tank 7. Discharged.
[0089]
  During work, the load pressure P in the head side chamber 2h_loadWhen the pressure rises, the upper stepped portion of the load pressure sensing portion 38 facing the load pressure chamber 39 of the pilot spool 33 increases its load pressure P._loadIn response, the pilot spool 33 is displaced in a direction away from the seat 30.
[0090]
  As a result, the pressure in the spring chamber 28 on the main poppet 22 is reduced, the differential pressure acting on the upper and lower surfaces of the main poppet 22 increases, and the main poppet 22 acts in the opening direction against the restoring force of the return spring 29. Since the passage 15a communicates with the tank 7, the load pressure P can be reduced by an abrupt input operation of the operation lever 87._loadLoad pressure P due to load pressure feedback to the load pressure sensing unit 38_loadAutomatically decreases with good response, so that this load pressure P_loadFluctuations can be suppressed.
[0091]
  The leak reduction function of the meter-in valves A1IMV and A2IMV will be explained. When the operation lever 87 is in the neutral position and no command (current value) is given to each push solenoid 57, the pilot spool 54 is shown in FIG. As in the neutral position. Since the common bypass valve 8 is open and the pump discharge amount from the variable displacement pump 1 is also minimal, the pressure in the passage 13 is low.
[0092]
  In this case, the load pressure P higher than the pressure in the passage 13 is applied to the head side chamber 2h of the cylinder type fluid pressure actuator 2._loadIf there is, the high pressure is selected by the shuttle valve 42 from the passage 15 and this load pressure P_loadIs introduced into the spring chamber 51 through the opening 47a of the variable slot 47 and the main poppet 41 on the meter-in side is pressed toward the seat 49 together with the spring force of the return spring 52, so that no leak from the passage 15 to the passage 13 occurs.
[0093]
  Further, the load hold check valve function of the meter-in valves A1IMV and A2IMV will be described. When the operation lever 87 is operated, the common bypass valve 8 is closed, the pump discharge amount is increased, and the push solenoid 57 is supplied from the controller 86. When a command (current value) is supplied and acts in the direction in which the pilot spool 54 is pushed in, the poppet unit 69 opens the seat 56.
[0094]
  At this time, the load pressure P of the passage 15 is still_loadIs higher than the pressure in the passage 13, the spring chamber 51 of the main poppet 41 is equal to the pressure in the passage 15 on the high pressure side, and the main poppet 41 remains closed, which functions as a load hold check valve. Will play.
[0095]
  Further, when the common bypass valve 8 is closed and the pump discharge amount increases, the pump discharge pressure in the passage 13 eventually becomes the load pressure P in the passage 15._loadIt becomes higher than
[0096]
  At this time, the pressure on the passage 13 side is selected by the shuttle valve 42 and acts on the poppet portion 69 of the pilot spool 54 from the spring chamber 51 of the main poppet 41. This pressure is the pressure of the passage 65 (= pressure of the passage 15). Therefore, a pilot flow rate that flows from the passage 53 to the passage 65 through the seat 56, the spring chamber 61, and the check valve 64 is generated.
[0097]
  Since the main poppet 41 on the meter-in side has a pilot flow rate amplification function, the pressure in the spring chamber 51 decreases as the pilot flow rate increases, and the flow rate control unit 48 of the main poppet 41 lifts from the seat 49. As the opening area of the valve tip gradually increases, a controlled main flow rate is generated from the passage 13 to the passage 15, and the cylinder-type fluid pressure actuator 2 slowly expands.
[0098]
  Next, each part of the control system shown in FIG. 3 will be described together with its function.
[0099]
(1) Load pressure estimation function
  In the bridge circuit 3 in which the pilot spool 54 on the supply side (meter-in side) and the pilot spool 33 on the discharge side (meter-out side) are made independent, when the pilot spool 54 is driven, the pilot spool 33 becomes the non-drive side, When the pilot spool 33 is driven, the pilot spool 54 is on the non-driving side, but the non-driving side pilot spool 54 or 33 is placed in a dead band near the neutral position where the passing flow rate remains zero. The load pressure P_loadIs estimated.
[0100]
  For example, when the meter-in side pilot spool 54 is on the non-driving side, the pilot spool 54 is slightly displaced downward. In this case, when the pilot spool 54 is slightly displaced downward by the displacement amount X, FIG. The force acting upward at²X / dt²Reaction force md when exercising²X / dt²And the viscous resistance C · dX / dt (C is a damping constant related to the viscous resistance) when the pilot spool 54 moves in oil, and the repulsive force K · X (K is the spring constant) due to the compression amount X of the return spring 62 And the load R of the return spring 62 and the load pressure P fed back from the passage 15 to the donut area-like load pressure chamber 78 through the passages 65 and 79._loadIs the lower pressure receiving area A of the load pressure sensor 77 of the pilot spool 54_reaForce P acting on_load・ A_reaOn the other hand, the force acting downward in the figure is that the pressure F proportional to the current I generated when the current I flows through the push solenoid 57 and the common tank 7 from the plurality of bridge circuits 3 and 3a. The tank line pressure Pt resulting from the structure in which the hydraulic oil is discharged is the upper pressure receiving area A of the load pressure sensing unit 77._reaForce Pt · A acting on_reaIn the dead band in the vicinity of the neutral position of the pilot spool 54, no passing flow rate is generated between the seat 56 and the poppet portion 69. Therefore, it is necessary to consider the flow force generated along with this passing flow rate. Since the upward force and the downward force are balanced, the following Expression 3 is established.
[0101]
[Formula 3]
m ・ d²X / dt²+ C ・ dX / dt + K ・ X + R + P_load・ A_rea= F + Pt · A_rea
[0102]
  When rewritten, the following expression 4 is obtained.
[0103]
[Formula 4]
P_load= {F- (m · d²X / dt²+ C ・ dX / dt + K ・ X + R) + Pt ・ A_rea} / A_rea
[0104]
  In this formula 4, m, C, K, R and A_reaAre known constants, X, dX / dt and d²X / dt²Can be measured by the displacement sensor 82 or calculated from the measured value, F can be calculated from the solenoid current I, and the tank line pressure Pt can be detected by a common pressure sensor._loadCan be estimated by the above equation.
[0105]
  FIG. 4 is a block diagram of a load pressure calculation device 92 for estimating and calculating such load pressure. The current I to the push solenoid 57 is converted into a pressing force F by a function 112, and this pressing force F Since noise includes noise, the noise is removed by the noise filter 113. Then, each numerical value such as the pressing force F is input to the calculation unit 114, and the load pressure P_loadIs obtained by calculation.
[0106]
  Further, the load pressure calculation device 92 includes a displacement X of the pilot spool 54, a speed dX / dt, and an acceleration d.²X / dt²A noise filter 115 is provided to remove noise from the noise.
[0107]
  On the other hand, when the pilot spool 33 of the meter-out side passage 15 is on the non-driving side, similarly, the pilot spool 33 is slightly displaced within the range of the dead band, so that the load pressure P_loadCan be estimated.
[0108]
  Thus, the load pressure P is applied to the load pressure sensing parts 38 and 77 formed in steps on the pilot spools 33 and 54, respectively._loadAnd the load pressure P from the balance between the feedback force and the thrust of the pilot spools 33, 54, etc._loadIs formed.
[0109]
  In short, this load pressure calculation device 92 is a neutral position where the supply side (pump side) pilot valve and the discharge side (tank side) pilot valve are independent, and the flow rate through the non-drive side pilot valve is zero. In the nearby dead band, a pressure sensor is used to detect the load pressure without considering the flow force generated by the passing flow rate by slightly displacing the pilot valve on the non-driving side. Without load pressure P_loadCan be estimated with high accuracy.
[0110]
(2) Flow control function
  Formula 1
Q = α ・ A ・ (P_P-P_load)^1/2
Pump discharge pressure P_PIs detected by the pump pressure sensor 88 and the load pressure P_loadCan be calculated by the load pressure calculation device 92, the drive current is supplied to the push solenoid 57 by lever operation, and the displacement amount X of the pilot spool 54 calculated by the functions 93 and 94 is calculated._CAs described above, the amount of displacement of the main poppet 41 is controlled, that is, the opening area A of the main poppet 41 is controlled, thereby realizing the flow rate Q in the main poppet 41 and the fluid pressure. The operating speed of the actuator 2 is controlled.
[0111]
(3) Pressure control function
  For example, the load pressure P in the head side chamber 2h of the fluid pressure actuator 2_loadRises, the lower stepped portion of the load pressure sensing portion 77 facing the load pressure chamber 78 of the pilot spool 54 becomes the load pressure P_loadIn response, the pilot spool 54 is displaced upward in the figure. Thereby, the opening degree of the poppet portion 69 with respect to the seat 56 is reduced, and high load driving is prevented.
[0112]
  Even when the discharge pressure from the pump 1 is higher than the load pressure to be driven, the pilot spool 54 is returned to the neutral position (the closed position shown in the figure) even in the opening of the poppet portion 69 by this high load drive prevention function. When the poppet 69 closes the seat 56, the load pressure P_loadCan be prevented from rising to the pump discharge pressure.
[0113]
  Further, the load pressure is fed back to a load pressure sensing unit 77 provided in a stepped shape on the pilot spool 54, and consequently the load pressure is fed back to the flow control mechanism of the main poppet 41 controlled by the pilot spool 54. A pressure feedback mechanism is formed, and the main poppet 41 can control the load pressure to a set value.
[0114]
  This will be described with reference to FIG. 5. When the actual load pressure suddenly rises and protrudes with respect to the step input of the operation lever 87, the load pressure sensing unit 77 is shown as shown in the characteristic curve of the actual pilot spool displacement. It is returned to the neutral position side by a load pressure feedback mechanism such as. Along with this, the main poppet 41 is also returned to the neutral position side as shown in the characteristic curve of the actual main poppet displacement, and the actual load pressure decreases with good response, so that fluctuations in the load pressure can be suppressed.
[0115]
  At this time, the load pressure P to be driven_loadIs adjusted by the thrust of the push solenoid 57, that is, the drive current.
[0116]
  That is, the load pressure P_loadTherefore, the load pressure P can be estimated using the push solenoid 57 connected to the pilot spool 54._loadAdjust the thrust to counter.
[0117]
  For example, when the thrust of the push solenoid 57 is raised by the pressure feedback controller 101, this thrust is countered by the load pressure P_loadFeedback force (upward force acting on the lower pressure-receiving surface of the load pressure sensor 77)In response to theBy temporarily reducing the pilot spool 54 slightly, the pilot spool 54 can be returned to the neutral position with good response, and the load pressure can be controlled so as not to exceed the set pressure.
[0118]
  When this is indicated by a solid line in FIG. 6, when the thrust of the push solenoid 57 rises with respect to the step input of the operating lever 87, the input current value to the push solenoid 57 is once lowered immediately after the rise, The thrust is the load pressure P_loadBy reducing the feedback force by the above, the pilot spool 54 is operated in the closing direction, the spring chamber 51 of the main poppet 41 is temporarily increased, and the opening operation of the main poppet 41 is suppressed, thereby reducing the load pressure P_loadHowever, it is possible to achieve stability of the control system by controlling the pressure so as not to overshoot the set pressure. A dotted line is an overshoot state.
[0119]
  In this way, by controlling the thrust, that is, the drive current of the push solenoid 57 without using a pressure control valve such as a relief valve for each fluid pressure actuator and without using a pressure sensor for detecting the load pressure, The main poppet 41, which is also a flow control means, loads the pressure P_loadCan be adjusted.
[0120]
  Conventionally, there is a method of controlling the load pressure so that it does not exceed a preset pressure by measuring the load pressure using a pressure sensor or the like and electrically controlling the throttle of the pilot spool. There is a problem that the control system becomes unstable due to a delay in calculation of feedback.
[0121]
(4) Return spring force adjustment function
  The meter-in valve A2IMV will explain the load pressure P by the gain adjusting device 97._loadAccordingly, the current value supplied to the push solenoid 57 of the pilot spool 54 is controlled to correct the push solenoid 57 so that the thrust of the push solenoid 57 is increased or decreased, thereby substantially adjusting the spring force (spring constant) of the return spring 62. To adjust.
[0122]
  For example, the load pressure P_loadIn a high region, that is, in a region where the feedback force to the load pressure sensing unit 77 is large, by reducing the gain of the current value supplied to the push solenoid 57 by the gain adjusting device 97 and reducing the thrust of the push solenoid 57, Correction is performed so that the spring force (spring constant) of the return spring 62 is relatively increased. Thereby, the displacement of the pilot spool 54 with respect to the fluctuation of the load pressure is suppressed, and the stability of the control system is improved.
[0123]
  Conversely, the load pressure P_loadIn a low region, the gain of the current supplied to the push solenoid 57 by the gain adjusting device 97 is increased, and the thrust of the push solenoid 57 is increased to relatively reduce the spring force (spring constant) of the return spring 62. Correct as follows. As a result, even a slight change in load pressure is sensed by feedback with high sensitivity, the control accuracy is improved, and the responsiveness of pressure control is improved.
[0124]
  In particular, the pilot spool 54 has a load pressure P_loadWhen the load pressure is estimated by the load pressure calculation device 92 from the balance between the thrust acting on the pilot spool 54, the spring force, and the feedback force, this gain adjustment method can be used to estimate the accuracy of the load pressure. Can be improved.
[0125]
  Thus, the load pressure P estimated by the load pressure calculation device 92 is calculated._loadAccordingly, by controlling the current value gain supplied to the push solenoid 57 by the gain adjusting device 97, the spring constant of the return spring 62 of the pilot spool 54 can be substantially variably controlled by controlling the thrust. The stability, control accuracy and responsiveness of the control system can be improved, and smooth operability can be obtained.
[0126]
  This spring force adjustment is also possible with the meter-out valves A3IMV and A4IMV. For example, in the meter-out valve A4IMV, the load pressure P_loadIn the high region, that is, the load pressure P fed back from the passage 36 to the load pressure sensing unit 38._loadIn the region where the force due to is large, the current value supplied to the push solenoid 35 by the gain adjusting device (corresponding to 97 but not shown) is set so that the spring force (spring constant) of the return spring 34 becomes relatively large. By correcting the gain so as to decrease the thrust of the push solenoid 35, the displacement of the spool with respect to the fluctuation of the load pressure is suppressed, and the stability of the control system is improved.
[0127]
  Conversely, the load pressure P_loadIn a low region, the gain of the current supplied to the push solenoid 35 is increased by the gain adjusting device so that the spring force (spring constant) of the return spring 34 becomes relatively small, and the thrust of the push solenoid 35 is increased. By correcting in this way, even a slight change in the load pressure is sensed with high sensitivity, the control accuracy and the estimation accuracy of the load pressure are improved, and the responsiveness of the pressure control is improved.
[0128]
(5) Construction machine workload estimation function
  As shown in FIG. 7, a working arm as a movable body (hereinafter, this working arm is referred to as a front working device FL) is pivotally supported in a vertically movable manner on a hydraulic excavator as a work machine. The work apparatus FL is moved up and down by a fluid pressure actuator (hereinafter, this fluid pressure actuator is referred to as a boom cylinder 2BM).
[0129]
  The work load estimation device 102 is configured to load a bucket load (sediment load) W as a work load in loading work using a hydraulic excavator._LIs estimated as follows.
[0130]
  During work, the boom cylinder 2BM often moves, and the load pressure P generated on the head side of the boom cylinder 2BM_loadIs affected by the inertia load, so the bucket load W is accurate._LIn order to estimate this, it is necessary to remove the influence of the inertial load.
[0131]
  Therefore, first, the load pressure P of the boom cylinder 2BM_loadTime series data is indirectly measured by a load pressure calculation device 92 as a load pressure measuring means, and the load pressure P continuously measured as shown in FIG._loadFrom the time series data of the frequency component (ω₀~ Ω₁) Is extracted and subtracted, and the load pressure P after the subtraction_loadIn-bucket load W_LIs estimated.
[0132]
  Frequency component within a predetermined range due to inertial load (ω₀~ Ω₁) Is the measured load pressure P_loadIs extracted by passing the time series data through the band-pass filter 121 for a certain period of time, and the extracted frequency components (ω₀~ Ω₁) Is measured by the subtractor 122 as a predetermined frequency removal calculating unit._loadBy subtracting from the time series data, it is possible to remove the influence of the inertial load.
[0133]
  The reason why the bandpass filter 121 is used for a certain period of time is to improve the subsequent followability.
[0134]
  In this case, the bandwidth of the bandpass filter 121 (ω₀~ Ω₁) Is adjusted to the natural frequency of the front work apparatus FL. Thereby, the inertial load due to the natural vibration of the front work apparatus FL can be effectively removed.
[0135]
  As shown in FIG. 9, the band-pass filter 121 has a ω₀The following frequencies are cut and₁By cutting the above frequencies, a predetermined range of frequency components (ω₀~ Ω₁).
[0136]
  The frequency component (ω₀~ Ω₁) Minus the load pressure P_loadIs input to the work load calculation unit 125, and the work load in the tip bucket of the front work apparatus FL, that is, the load W in the bucket_LIs estimated by calculation.
[0137]
  In other words, the work load calculation unit 125 measures the posture of the front work apparatus FL with a rotation angle detector provided at each rotation shaft part of the front work apparatus FL, and loads the load W in the bucket._L(X, Z) coordinate value of the boom cylinder 2BM, the load pressure P in the head side chamber of the boom cylinder 2BM from which the influence of the inertial load is removed_loadAnd bucket load W_LFrom the (X, Z) coordinate value of_LW_L= F (P_load, X, Z).
[0138]
  This bucket load W_LBy calculating and accumulating for each work, for example, the total weight of the loaded material such as earth and sand with respect to the transport vehicle can be easily calculated, and an excessive weight can be prevented without using a special load sensor.
[0139]
  FIG. 10 shows a load pressure P affected by an inertial load by a dotted line._loadIn addition, the frequency component (ω in a predetermined range extracted through the band-pass filter 121 is indicated by a solid line.₀~ Ω₁) Removed load pressure P_loadTime series data, that is, the load pressure P excluding the influence of the inertial load of the front working device FL_loadThe time series data of is shown.
[0140]
  In this way, even when the boom cylinder 2BM is operating in the loading operation of the hydraulic excavator, the influence of the inertia load of the front working device FL is eliminated, and the cylinder load pressure P_loadIs accurately estimated, and the cylinder load pressure P_loadAnd the posture of the front work device FL, the load in the bucket W_LCan be obtained quickly and accurately.
[0141]
  Next, the load pressure of the boom cylinder 2BM estimated with high accuracy by eliminating the influence of the inertia load by the work load estimating device 102 is taken into the pressure feedback controller 101 and used for pressure control. The simulation results of the control are shown in FIGS.
[0142]
(Simulation conditions)
  (1) Cylinder initial load: 0 Pa (assuming that the bucket is placed on the ground)
[0143]
  (2) Pump initial load: 20 × 9.81 × 10⁴Pa, however, the pump discharge pressure after lever operation is 20 x 9.81 x 10 from the actual cylinder load pressure⁴It is assumed that the main relief valve 9 is controlled to be higher than Pa.
[0144]
  (3) Lever input: Step input (100%) 0.2 seconds after the start of simulation. However, the lever input is assumed to have passed through a 20 Hz secondary low-pass filter.
[0145]
  (4) Cylinder load pressure: 100 × 9.81 × 10⁴Pa, provided that the cylinder load pressure is generated immediately after the cylinder starts moving.
[0146]
FIG. 11 is a step response characteristic diagram showing simulation results of actual main poppet displacement, required main poppet displacement, actual pilot spool displacement, and required pilot spool displacement with respect to step input of the operation lever to the pressure control system.
[0147]
    A: Control lever position
    B: Actual main poppet displacement
    C: Required main poppet displacement
    D: Actual pilot spool displacement
    E: Required pilot spool displacement
[0148]
FIG. 12 is a step response characteristic diagram showing simulation results of actual cylinder speed and actual cylinder displacement with respect to step input of the operating lever to the pressure control system.
[0149]
    F: Actual cylinder speed
    G: Actual cylinder displacement
[0150]
FIG. 13 is a step response characteristic diagram showing simulation results of actual main poppet displacement, requested main poppet displacement, actual pilot spool displacement, and requested pilot spool displacement with respect to the step input of the operation lever to the flow control system.
[0151]
    A ': Control lever position
    B ': Actual main poppet displacement
    C ': Required main poppet displacement
    D ': Actual pilot spool displacement
    E ′: Required pilot spool displacement
[0152]
FIG. 14 is a step response characteristic diagram showing simulation results of actual cylinder speed and actual cylinder displacement with respect to step input of the operation lever to the flow control system.
[0153]
    F ': Actual cylinder speed
    G ': Actual cylinder displacement
[0154]
(simulation result)
  Comparing the simulation result of FIG. 11 and the simulation result of FIG. 13, it can be seen that the pressure control has a smaller variation in load pressure than the flow rate control and converges more quickly. This is because when the load pressure is high, the pilot spool 54 is returned to the neutral position (closed position) direction, and accordingly, the opening of the main poppet 41 is reduced, thereby reducing the load pressure.
[0155]
  Further, when comparing the simulation result of FIG. 12 with the simulation result of FIG. 14, the cylinder speed change is smoother in the pressure control than in the flow rate control, and the fluid pressure actuator 2 can be operated smoothly.
[0156]
【The invention's effect】
  According to the first aspect of the invention, when the load pressure increases, the load pressure is directly fed back to the pilot valve, and the pilot valve is displaced in the direction of decreasing the pilot flow rate by the feedback force. Since the load pressure is controlled in the direction of decreasing flow rate and the load pressure decreases with good response, high load driving can be prevented without detecting the load pressure using a pressure sensor, and fluctuations in the load pressure can be suppressed to ensure stability. Instability due to calculation delay when feedback of load pressure from the conventional pressure sensor via the calculation system can be prevented, pressure control that converges in a short time is possible, and external thrust against the load pressure is further reduced. By adjusting, the load pressure to be driven can be adjusted. In particular, the feedback force due to the load pressure when raising the thrust against the load pressureIn response to theBy temporarily reducing the thrust, the pilot valve can be returned toward the neutral position with good response, and the stability of the control system can be improved.
[0157]
  According to the second aspect of the present invention, when the load pressure increases, the load pressure is directly fed back to the pilot valve by the load pressure feedback mechanism, and the pilot valve is displaced in the pilot flow rate decreasing direction by the feedback force. Since it is displaced in the main flow rate decreasing direction and decreases the load pressure with good response, it can prevent high-load driving, and can provide a pressure control device that can suppress fluctuations in the load pressure and ensure stability, and can also provide a pilot valve. By controlling the drive means, it is possible to provide a pressure control device that can adjust the load pressure to be driven by adjusting the thrust of the drive means against the load pressure. In particular, the feedback force due to load pressure when the thrust of the drive means is raised by the controller.In response to theBy temporarily reducing the thrust of the driving means, it is possible to provide a pressure control device that can return the pilot valve toward the neutral position with good response by the load pressure and improve the stability of the control system.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a pilot valve and a main valve according to a pressure control device of the present invention.
FIG. 2 is a fluid pressure circuit diagram showing an embodiment of a bridge circuit according to the pressure control device.
FIG. 3 is a block diagram showing an embodiment of a combined pressure-flow rate control system according to the pressure control apparatus.
FIG. 4 is a block diagram showing an example of a load pressure calculation device according to the pressure control device.
FIG. 5 is a characteristic diagram showing an operation example of a load pressure feedback mechanism according to the pressure control device.
FIG. 6 is a characteristic diagram showing an example of a pressure control method according to the pressure control device.
FIG. 7 is an explanatory diagram for explaining the function of the workload estimation device according to the pressure control device;
FIG. 8 is a block diagram showing an example of the workload estimation device.
FIG. 9 is a block diagram showing an example of a band-pass filter in the workload estimation device same as above.
FIG. 10 is a characteristic diagram showing an example of a function for removing the influence of the inertial load by the work load estimation device same as above.
FIG. 11 is a step response characteristic diagram showing simulation results of main poppet displacement and pilot spool displacement with respect to step input of the operating lever to the pressure control system.
FIG. 12 is a step response characteristic diagram showing simulation results of cylinder speed and cylinder displacement with respect to step input of the operating lever to the pressure control system.
FIG. 13 is a step response characteristic diagram showing simulation results of main poppet displacement and pilot spool displacement with respect to step input of the operation lever to the flow control system.
FIG. 14 is a step response characteristic diagram showing simulation results of cylinder speed and cylinder displacement with respect to step input of the operation lever to the flow rate control system.
FIG. 15 is a circuit diagram showing a fluid pressure actuator control circuit including a bridge circuit.
FIG. 16 is a circuit diagram showing a load pressure feedback mechanism using a conventional pressure sensor.
[Explanation of symbols]
        22, 41 Main poppet as main valve
        33, 54 Pilot spool as pilot valve
        35, 57 Push solenoid as drive means
        36, 79 Passage of load pressure feedback mechanism
        38, 77 Load pressure sensor of load pressure feedback mechanism
        86 controller

Claims (2)

Pilot control of the main valve for main flow control by controlling the pilot flow with the pilot valve,
The load pressure of the main flow rate is fed back to the pilot valve,
Displace the pilot valve in the direction of decreasing the pilot flow rate by increasing the load pressure,
By reducing the pilot flow, the main valve is controlled in the main flow reduction direction to reduce the load pressure.
A pressure control method for adjusting a load pressure by controlling an external thrust acting on the pilot valve from a direction opposed to the load pressure fed back to the pilot valve,
A pressure control method characterized by temporarily reducing a thrust according to a feedback force due to a load pressure when raising an external thrust. A pilot valve for controlling the pilot flow rate; and
A main valve for main flow control that is pilot operated by a pilot valve;
A load pressure feedback mechanism that feeds back the load pressure of the main flow rate to the pilot valve, displaces the pilot valve in the pilot flow rate decreasing direction by increasing the load pressure, and controls the main valve in the main flow rate decreasing direction to decrease the load pressure;
A pressure control device comprising driving means for adjusting a load pressure by controlling a thrust acting on the pilot valve from a direction opposite to the load pressure fed back to the pilot valve,
A pressure control device comprising a controller for temporarily reducing the thrust of the driving means in accordance with a feedback force due to a load pressure when raising the thrust of the driving means.

Images