JP5026227B2 - Hydraulic control equipment for construction machinery - Google Patents

Description

  The present invention relates to positive control of a variable displacement pump that supplies pressure oil to each hydraulic actuator during operation of a construction machine such as a hydraulic excavator, and in particular, suppresses vibrations of structures constituting the construction machine such as a boom and an arm. About.

  As shown in FIG. 7 (corresponding to FIG. 15 of Patent Document 1), the positive displacement control of the variable displacement pump is generally performed by providing a pump discharge capacity adjusting mechanism 102 to the switching valves V1, V2, and V3 having the center bypass passage 100. The discharge capacity of the variable displacement pump PM is supplied, and the discharge capacity of the variable displacement pump PM is adjusted by the operation signals (a1, b1), (a2, b2), (a3, b3) of the switching valve. The discharge flow rate of the variable displacement pump PM is increased as the operation amount of each switching valve increases.

  In the case of this positive control system, since part of the oil discharged from the variable displacement pump PM is discharged from the center bypass passage 100 to the tank T during the neutral and operation of the switching valve, the operability is the same as in the negative control system. Although it is good, there are problems in system efficiency and operability during complex operation. In particular, the discharge capacity of the variable displacement pump PM is uniquely determined in accordance with the operation signal of the switching valve regardless of the opening of the center bypass passage 100, so that the opening of the center bypass passage 100 and the opening to the cylinder port are determined. It is difficult to adjust the area and timing with the passage, and there is a possibility that problems such as abnormally high pressure or delay in supply pressure may occur in the pump supply line. In addition, since the discharge capacity of the variable displacement pump PM is adjusted by a signal output in parallel with the operation signal of the switching valve, the response of the system is relatively good.

  Next, a hydraulic circuit diagram of the negative control system is shown in FIG. 8 (corresponding to FIG. 14 of Patent Document 1).

  In this system, the pressure generating means 104 is provided at the center bypass outlet of the switching valve V3 having the center bypass 100, and the upstream pressure of the pressure generating means 104 is caused to act as the signal pressure Pn to the discharge capacity adjusting mechanism 102 of the variable capacity pump PM. In addition, the discharge flow rate adjusting mechanism 102 is configured to increase the discharge capacity in accordance with a decrease in the signal pressure. In this system, the signal fed back from the switching valve to the pump is low pressure, and pressure oil is supplied to the hydraulic actuator while part of the pump discharge oil is bleed off. It has excellent properties and is widely used. However, in this case, the pressure oil supplied from the variable displacement pump PM to the switching valve is partly discharged to the tank through the center bypass passage 100 when the switching valve is neutral or in the middle of operation. It is converted into heat and discarded. In particular, when the load of the hydraulic actuator connected to the switching valve is large, the operation amount of the switching valve until the start is large, and the pressure oil that is squeezed out during this time has a small discharge capacity of the pump PM by the pressure oil. However, there is a problem in that it still wastes energy.

  On the other hand, the amount of oil discharged from the center bypass passage 100 can be made relatively small by reducing the center bypass passage 100 of the switching valve, for example. It is very difficult to adjust the appropriate area and timing, and depending on the processing accuracy and the operation of the switching valve, the pump discharge oil is enclosed in the supply line and an abnormally high pressure is generated, which may lead to deterioration of energy efficiency. In a hydraulic control system for a hydraulic excavator, the operability when a plurality of hydraulic actuators are operated simultaneously, that is, the flow distribution characteristic from the variable displacement pump PM to each hydraulic actuator is extremely important. It is uniquely determined by the opening area of each switching valve with respect to the flow rate at the pump rotation speed. Therefore, there is a possibility that good operability may not be maintained when the engine rotation speed or load pressure changes. There is.

  Further, as shown in FIG. 9 (corresponding to FIG. 16 of Patent Document 1), in the load sensing system, the amount of oil supplied to the hydraulic actuator 106 is changed when the switching valves V1 and V2 are operated. The discharge capacity of the variable displacement pump PM is adjusted so that the differential pressure on the meter-in side becomes constant. Therefore, since there is no oil to be squeezed out unlike the negative control system and the positive control system, the system efficiency is improved accordingly.

  However, in order to properly adjust the pump discharge capacity, the differential pressure on the meter-in side must be maintained to some extent, for example, about 20 bar or more, and as a result, the amount of oil passing through each time the switching valves V1 and V2 are passed. Regardless, pressure loss occurs and there are still problems with system efficiency.

  Furthermore, regarding the adjustment of the pump discharge capacity, first, the switching valve is operated, and as a result, the pump capacity is adjusted.

  As a method for solving such a problem, as shown in the block diagram of FIG. 10 (corresponding to FIG. 1 of Patent Document 1), it is disclosed that the discharge flow rate of the variable displacement pump is controlled by the discharge capacity adjusting unit. ing. The pressure oil supplied from the variable displacement pump is supplied to one or more hydraulic actuators via a switching valve unit including one or more switching valves and a peripheral hydraulic circuit.

  From the operator operation command section, the drive direction and drive amount of each hydraulic actuator are commanded to the switching valve unit as pilot pressure oil. Further, an adjustment signal X as a signal pressure is given to the adjustment amount correction unit from the operator operation command unit. As the adjustment signal X, the highest pressure is selected from among the pilot pressure oils supplied to the switching valve of the switching valve unit.

  On the other hand, the discharge oil pressure Pd of the variable displacement pump and the pressure Ps of the pressure oil supplied to the hydraulic actuator are detected across the switching valve unit, and the differential pressure is formed by the differential pressure generating unit. The adjustment signal Y output as a signal pressure from the differential pressure generating unit is given to the adjustment amount correcting unit. The adjustment amount correcting unit reduces the adjustment signal X by causing the adjustment signal Y to act on the adjustment signal X. The output of the adjustment amount correction unit is given to the discharge flow rate adjustment unit.

  That is, the maximum pressure of the drive signal to the switching valve is corrected in accordance with the differential pressure (Pd−Ps) and applied to the discharge flow rate adjusting unit. (Patent Document 1)

  However, in FIG. 10, the function of the adjustment amount correction unit is that the adjustment signal X from the operator operation command unit is corrected by the signal Y from the differential pressure generation unit. That is, considering this function in terms of opening characteristics of the switching valve spool, the opening characteristics of the switching valve spool are apparently changed by the differential pressure so that the differential pressure between the pressure of the hydraulic actuator and the pump discharge pressure is constant. However, only the function of correcting the adjustment signal X from the operator operation command unit by this differential pressure is uncomfortable from the viewpoint of the operability of the operator with respect to the hydraulic actuator.

  For example, as shown by Q2 in FIG. 11, when the operator increases the operation amount (Pm), a relatively small flow rate is supplied up to the operation amount Pm1, and the operation amount Pm1. There is a case in which it is desired to drive the hydraulic actuator so that a relatively large flow rate is supplied in a larger range. In order to satisfy such a requirement, as indicated by Q1, it cannot be realized simply by correcting the operation amount (Pm) by the differential pressure. In order to modify the opening characteristics of such a switching valve spool, notches and other notches are provided on the outer periphery of the spool to change its characteristics, but such measures require skill and are treated as know-how. It was not clear. Moreover, even if it is going to change what formed the specific notch, it is virtually impossible to rework, and the same spool cannot have a plurality of opening characteristics.

  Further, in the system shown in FIG. 10, during the operation, the structure such as the boom and arm of the construction machine described above may vibrate at its natural frequency and the smooth operation may not be performed. A waveform Vw indicated by a broken line superimposed on Q1 in FIG. 11 illustrates a state in which the pump discharge amount changes when the structure vibrates.

  According to the knowledge of the present inventors, the type of vibration (natural frequency) is not always one, but the frequency is at most about several hertz. For example, if vibration occurs during the boom lowering operation, the boom will not move down smoothly, but will be intermittently lowered, and noise will be generated along with it. There is a risk of damaging the structure.

  In addition, the operator may not be able to predict the timing of occurrence and termination of such vibrations, and thus feels not only the above-mentioned operational discomfort, but also that the construction machine itself may be damaged.

JP 2004-28333 A

  As a result of various studies in view of the above-mentioned points, the present inventors have described above by giving an external signal generated according to the operation state of the hydraulic actuator different from the differential pressure signal to the differential pressure adjusting unit. I found that the problem could be solved basically.

  Accordingly, an object of the present invention is to introduce an external signal generated in accordance with the operation state of the hydraulic actuator to the differential pressure adjusting unit in the positive control of the variable displacement pump adopting load sensing to suppress the natural vibration of the structure. An object of the present invention is to provide a hydraulic control device for a construction machine.

In order to achieve the above object, the hydraulic control device for a construction machine according to the present invention adjusts the discharge flow rate of the variable displacement pump according to the flow rate adjustment signal given according to the operation amount of the operation valve, and adjusts the hydraulic actuator pressure. In a hydraulic control device for a construction machine having a differential pressure adjusting means for detecting and adjusting the flow rate adjustment signal so as to maintain a differential pressure between a meter-in side pump pressure of a switching control valve and a hydraulic actuator pressure below a predetermined value. The differential pressure adjusting means is configured to adjust by a first external signal having a waveform that suppresses a natural vibration of the construction machine structure generated according to an operation state of a hydraulic actuator of the construction machine , and the construction machine structure The waveform for suppressing the vibration of the object is a waveform obtained by inverting the phase of the vibration waveform of the construction machine structure .

  In this case, the differential pressure adjusting means is responsive to the first external signal having a waveform that suppresses the natural vibration of the construction machine structure generated according to the operation state of the hydraulic actuator of the construction machine, and the operation amount of the operation valve. The flow rate adjustment signal to be applied can be adjusted by an external signal obtained by adding the second external signal generated by the function generating means for supplying the flow rate adjustment signal as a function value of the electric signal obtained by oil-electric conversion.

  Further, in this case, the differential pressure adjusting means has a valve body structure in which a spool is housed therein, and is formed on one end portion side of the spool so that a load detection pressure of the hydraulic actuator is guided and the spool is connected to the other end portion. A first oil chamber (RM1) provided with a spring urging toward the first oil chamber, and a second oil chamber arranged on the other end side of the spool so as to face the first oil chamber and to which the meter-in side pump pressure is guided (RM2), and the first and second oil chambers are partitioned by the first and second spool large diameter portions, respectively, and further divided by the third third spool diameter large portion provided at the center thereof. And a third oil chamber (RM3) connected to the high pressure side flow rate adjustment signal port of the operation valve, a fourth oil chamber (RM4) connected to the tank port, and a spool on the first oil chamber side The external signal facing the end face A fifth oil chamber (RM5) to be supplied and a swash plate port connected to the oil chamber of the swash plate adjusting mechanism of the variable displacement pump and formed to face the outer peripheral surface of the third large diameter portion can do.

  According to the first aspect of the present invention, the discharge flow rate of the variable displacement pump is adjusted according to the flow rate adjustment signal given according to the operation amount of the operation valve, the hydraulic actuator pressure is detected, and the switching control valve In the hydraulic control apparatus for a construction machine, comprising the differential pressure adjusting means for adjusting the flow rate adjustment signal so as to maintain the differential pressure between the meter-in side pump pressure and the hydraulic actuator pressure below a predetermined value, the differential pressure adjusting means Is configured to be adjusted by the first external signal having a waveform that suppresses the vibration of the construction machine structure generated according to the operation state of the hydraulic actuator of the construction machine, so that the vibration of the structure occurs during the operation of the operator. Even so, the vibration can be suppressed immediately.

  According to the second aspect of the present invention, the differential pressure adjusting means includes the first external signal having a waveform that suppresses the natural vibration of the construction machine structure that is generated according to the operation state of the hydraulic actuator of the construction machine. The flow rate adjustment signal given in accordance with the operation amount of the operation valve is adjusted by an external signal obtained by adding a second external signal generated by function generating means for giving a function value of an electric signal obtained by oil-electric conversion. Therefore, even if vibration occurs in the structure during the adjustment with respect to the differential pressure adjusting means by the second external signal, the first external signal is superimposed on the second external signal. Can be suppressed.

  According to the third aspect of the present invention, the waveform for suppressing the natural vibration of the construction machine structure is a waveform obtained by inverting the phase of the vibration waveform of the construction machine structure. Thus, a phase inversion waveform can be easily generated.

  According to the fourth aspect of the present invention, the differential pressure adjusting means is a valve body structure in which a spool is accommodated therein, and is formed on one end portion side of the spool, and the load detection pressure of the hydraulic actuator is guided. And a first oil chamber provided with a spring for biasing the spool toward the other end, and disposed on the other end of the spool so as to face the first oil chamber, and the meter-in side pump pressure is guided. The second oil chamber, and the first and second oil chambers are divided by the first and second spool diameter large portions, respectively, and further provided with a third spool diameter large portion provided at the center portion thereof. And a third oil chamber connected to the high-pressure side flow rate adjustment signal port of the operation valve, a fourth oil chamber connected to the tank port, and a spool end face on the first oil chamber side. A fifth oil chamber to which an external signal is supplied; Since the swash plate port is connected to the oil chamber of the swash plate adjusting mechanism of the variable displacement pump and is formed so as to face the outer peripheral surface of the third large diameter portion, in addition to the effects described above, the operation of the operator The above-mentioned uncomfortable feeling can be reduced as much as possible, the differential pressure adjusting means can be configured as a single valve body structure, and the second external signal is transmitted from a spring provided in the first oil chamber. Since it acts so as to increase the urging force, the movement of the spool with respect to the change in the differential pressure can be slowed, thereby giving the operator a stable operational feeling against the load fluctuation.

  Hereinafter, examples based on the embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6 of the accompanying drawings.

  FIG. 1 shows a schematic configuration of an entire hydraulic excavator as a typical construction machine to which the present invention is applied. In FIG. 1, an excavator SHV has an upper swing body 6 mounted on a lower traveling body DRV driven by a hydraulic motor via a swing mechanism RM. The upper swing body 6 is provided with a cab 8 on one front side thereof, and a boom Bm is attached to the front center portion so as to be able to be raised and lowered. Further, an arm Am is attached to the tip of the boom Bm so as to be rotatable up and down, and a bucket Bk is attached to the tip of the arm Am. Reference numeral BCL is a hydraulic cylinder for driving the boom, AmCL is a hydraulic cylinder for driving the arm, and BCL is a hydraulic cylinder for driving the bucket. As is apparent from FIG. 1, when the boom Bm is operated from the horizontal posture, the load pressure on the boom cylinder BCL becomes very large. Reference numerals S1, S2, and S3 are vibration detection sensors. The sensor S1 is provided in the vicinity of the driver's cockpit, S2 is provided in the boom Bm, and S3 is provided in the arm Am.

  FIG. 2 is a control block diagram illustrating the concept of the present invention. In the figure, the hydraulic oil 10 of the construction machine is supplied with pressure oil from a variable displacement pump 22 via a switching control valve 20. From the operator operation command section 14, an operation pressure signal X is given to the switching control valve 20 and the differential pressure adjusting means 28. As indicated by the broken line, the differential pressure adjusting means 28 is supplied with the discharge pressure Pd of the pump 22 and the pressure Ps of the hydraulic actuator 10. Further, the differential pressure adjusting means 28 is supplied with an external signal Z which is a pressure oil signal from the external signal generating unit 32. The output of the differential pressure adjusting means 28 is given to a discharge flow rate adjusting mechanism 26 that adjusts the swash plate angle of the variable displacement pump 22. The external signal generator 32 generates an external signal Z that is generated according to the operation status of the hydraulic actuator 10.

  FIG. 3 is a schematic diagram of a hydraulic circuit in which the concept shown in FIG. 2 is applied to a positive control system of a variable displacement pump. In the figure, reference numeral 20 schematically shows a switching control valve for the hydraulic cylinder BmCL that drives the boom Bm, and ΔP is a differential pressure corresponding to the degree of restriction related to the spool opening characteristics. Reference sign Qac indicates a supply flow rate to the hydraulic cylinder BmCL (not shown). The angle of the swash plate 24 of the variable displacement pump 22 is uniquely determined by the supply pressure Pm to the oil chamber 26 a that opposes the elastic force of the spring 26 b of the discharge flow rate adjusting mechanism 26. In the illustrated example, the theoretical discharge amount Qth of the pump 22 increases as the supply pressure Pm increases.

  Reference numeral 28 denotes the differential pressure adjusting means shown in FIG. 2, and the whole is formed of a single valve body structure. In the differential pressure adjusting means 28, reference numeral 28a is a spool that is slidably inserted into an opening H formed inside the valve body, and has three large diameter portions D1, D2, and D3 provided in the middle portion thereof. It has been. A spring 28b is accommodated in the oil chamber RM1 on the left side of the large diameter portion D1. Further, the maximum detected load pressure Ps on the side of the plurality of hydraulic actuators including the hydraulic cylinder BmCL is guided to the oil chamber RM1 through the port PT1, as indicated by a broken line L1. On the other hand, an oil chamber RM2 is provided on the right side of the large diameter portion D2, and the port PT5 provided in the oil chamber RM2 is discharged to the pump 22 via the port PT5 as indicated by a broken line L2. An outlet side pressure Pd is introduced.

  An oil chamber RM3 is provided on the left side of the large-diameter portion D3, and an operator command is given to the port PT2 provided adjacent to the oil chamber RM3 via the port PT2, as indicated by a broken line L3. The operation command pressure X from the operation valve, that is, the maximum pressure Pmax selected by the high pressure selection means 30 is derived. Further, an oil chamber RM4 is provided on the right side of the large diameter portion D3, and a port PT4 provided adjacent to the oil chamber RM4 is led to the tank line T. The left end surface of the spool 28a faces the oil chamber RM5, and the oil chamber RM5 is further provided with a stopper 28c that determines a left stop position of the spool 28a. An external signal Z is supplied to the oil chamber RM5 from an electrohydraulic converter (hereinafter referred to as an electro-oil converter) 32b.

  The signal SG1 given to the electro-oil conversion unit 32b detects the vibration waveform when the boom Bm vibrates with its natural vibration while the operator operates the shovel, and changes the command pressure Pm for the variable displacement pump 22. It is generated to act to suppress the vibration.

  Reference numeral 100 denotes a vibration suppression signal generator that generates the signal SG1, and a vibration detector 100a (S1, S2, S3, etc. in FIG. 1) attached to an excavator structure such as a boom Bm and an arm Am. The determination unit 100b determines that the detection signal from the detection unit 100a is the natural vibration of the structure, and the waveform generation unit 100c generates a phase inversion signal waveform of the vibration waveform of the determined detection signal. ing. The vibration suppression signal generation unit 100 exemplifies one of the external signal generation units 32 in FIG.

  FIG. 4 schematically shows a state in which another embodiment of the external signal generator 32 in FIG. 2 is added to FIG. In FIG. 4, the operation command pressure X from the operation valve is converted into an electric signal by the hydroelectric conversion unit 32a and input to the external signal generation unit 32A. Further, the output signal SG2 of the external signal generation unit 32A is added to the signal SG1 which is the output of the vibration suppression signal generation unit 100 of FIG. 3 by the addition unit 102, and is converted into a pressure oil signal by the electro-oil conversion unit 32b. Is an external signal Z. In the present invention, the signal SG1 is defined as a first external signal, and SG2 is defined as a second external signal.

  FIG. 5A is a diagram illustrating the vibration suppression signal generation unit 100. In FIG. 5A, the detection outputs of the sensors S1 to S3 are always given to the determination unit 100b. In the determination part 100b, it is determined whether it is the natural vibration of the said structure by the frequency, amplitude, duration, etc. of the vibration waveform from each sensor. In the figure, the vibration waveform Vw (S2) from the sensor S2 attached to the boom Bm corresponds to the occurrence of natural vibration, and the other S1 and S3 are supplied with vibration waveforms having a high frequency and a small amplitude. An example is shown.

  The vibration waveforms from S1 and S3 correspond to vibrations associated with the rotation of, for example, a prime mover of a construction machine or a rotary shaft of a pump. In the phase inversion waveform generation unit 100c, the signal Vw (S2) is inverted and becomes -Vw (S2) as indicated by a broken line. The amplitude of the signal is further adjusted to generate a signal SG1.

  The gain adjustment can be automatically set so that the amplitude of the signal SG1 is gradually increased and the amplitude of the detection signal Vw (S2) becomes zero, but may be adjusted manually by the operator.

  FIG. 5B is a diagram illustrating the function of the external signal generation unit 32A in FIG. In FIG. 5B, function waveforms f1, f2, and f3 indicate changes in the value Eout of each function with respect to the value of the electric signal Ein corresponding to the operation command pressure X. For example, in the function f1, Eout with respect to the change in Ein has an upward convex conversion characteristic. On the other hand, the function f2 is a case where Eout stays slowly increasing until Ein increases, and Eout increases relatively rapidly with respect to an increase after a certain value.

  Further, the function f3 is a case in which Eout increases rapidly until Ein increases, and Eout remains relatively slow with respect to the subsequent increase. The function f0 is a case where Eout is always zero. Reference numeral 34 indicates a push button for selecting each function waveform. In addition, it is possible to display the waveform characteristics themselves or pictographs instead of the symbols f0 to f3 so that the operator can select the button instantaneously and accurately. In this case, it is preferable that the selection button displays the operation characteristics required by the operator, not the converted waveform itself. Furthermore, in that case, you may make it select with a voice instead of selection operation.

  Although FIG. 5B illustrates the functions based on the analog signals Ein and Eout, digital processing can also be performed using an A / D converter and a D / A converter. In that case, the functions f0 to f3 are given as corresponding memory tables.

  Next, the operation will be described with reference to FIGS. 5A and 5B and FIG.

  Assume that there is no occurrence of natural vibration in the structure, that is, the signal SG1 is zero in FIG. 5B.

  A case will be described in which the function f0 is selected and, therefore, no pressure oil is supplied to the oil chamber RM5.

  Here, if the operation command pressure X to the hydraulic actuator is zero, the differential pressure ΔP between the pressures Pd and Ps is also zero, and the spool 28a is slightly left of the drawing by the stopper 28c due to the elastic force of the spring 28b. At the stop position, the oil chamber RM3 and the port PT3 are electrically connected.

  In this state, when the operation command pressure X is applied to the port PT2 to drive the hydraulic actuator, the pressure Pm corresponding to the pressure X is applied from the oil chamber RM3 to the oil chamber 26a of the discharge flow rate adjusting mechanism 26 via the port PT3. Then, the swash plate 24 tilts and the variable displacement pump 22 discharges the pressure oil from the discharge port. A differential pressure ΔP is generated in the switching control valve 20 by the discharge flow rate Qac at this time. Due to this differential pressure, the discharge pressure Pd is applied to the port PT5, and the pressure Ps is applied to the port PT1. As the pressure X is gradually increased and the flow rate Qac is increased, the differential pressure ΔP is also increased. When the value of the pressure Pd becomes larger than the added value of the pressure Ps and the spring force of the spring 28b, the spool 28a moves to the left. As a result, the port PT3 and the oil chamber RM4 are electrically connected, and immediately the pressure of the oil chamber 26a. Drops, and the discharge flow rate of the variable displacement pump 22 is reduced. As a result, the differential pressure ΔP becomes smaller, the spool 28a returns to the right, and the oil chamber RM4 and the port PT3 are shut off.

  In this way, when a certain operation command pressure X is given, the position of the spool 28a is maintained so that the differential pressure (pd-Ps) at the ports PT1 and PT5 and the spring force of the spring 28b are balanced. That is, the spool position is controlled so that the differential pressure ΔP becomes equal to the elastic force of the spring 28b.

  Next, a case where a specific function fi other than f0 is selected in advance and the external signal Z obtained by converting the function of the operation command pressure X is supplied to the oil chamber RM5 will be described.

  In order to simplify the explanation, it is assumed that the operation command pressure X is applied in the state shown in FIG. 4 and the hydraulic actuator is being driven, and the spool 28a is in a balanced position as described above.

  In this case, if an external signal pressure Z having a certain magnitude is given to the oil chamber RM5 based on the function fi, the pressure Z acts on the left end surface of the spool 28a, so that the spring force of the spring 28b is increased. Accordingly, when the operation command pressure X is further commanded to increase by ΔX, the pressure Pd also increases by ΔPd as a result of the increase in the flow rate of the pump 22, and the process of newly reaching the balance state is Compared to the case where the pressure Z is not applied because the force obtained by adding the pressure Z to ΔPd is applied to 28a, the operation command pressure is suppressed while suppressing the change in the balance position of the spool 28a due to the load fluctuation between them. The balance position can be reached more faithfully with respect to X. This apparently corresponds to an increase in the spring constant of the spring 28b, and means that a stable response to a change in the operation command pressure X can be obtained.

  That is, as in the case of the function f0, the spool 28a is moved to the left by utilizing the increase in the differential pressure when the discharge flow rate Qac passing through the switching control valve becomes excessive, thereby the port PT3. And PT4 are communicated with the tank line, and the pressure in the oil chamber 26a is reduced to maintain the differential pressure within a predetermined range. When the spool 28a is further pressed from the left side with the external signal Z by the function fi Equivalently, the opening characteristic of the spool in the switching control valve is apparently changed so as to increase, and the change is made by making the pressure Z variable within the command range of the operation command pressure X. It can be set arbitrarily.

  FIG. 6 is a graph illustrating such an operation. In the figure, the horizontal axis St represents the operation amount (spool stroke amount) of the switching control valve 20, and the vertical axis Q represents the flow rate (opening characteristic) of the switching control valve 20. q1 represents a flow characteristic in which the differential pressure ΔP on the meter-in side is constant when no external signal Z is given, and q2 represents a flow characteristic determined by a remote pilot pressure command to the pump, that is, a flow characteristic of the variable displacement pump 22 itself. Q3 indicates a flow rate characteristic such that the differential pressure ΔP on the meter-in side when the differential pressure ΔP is increased is constant. Here, the characteristic q3 indicates a theoretical characteristic, but the actual flow rate does not exceed the characteristic q2 corresponding to the maximum discharge flow rate of the pump 22. That is, for example, when the external signal Z is given to the value Qa on the characteristic q1 at the manipulated variable Stj and the value Qc on the characteristic q3 is set, the actual flow rate at that time becomes Qc. As shown by the characteristic q3, when the external signal Z is applied so as to be larger than the characteristic q2, the actual flow rate is Qb, that is, the maximum flow rate of the pump 22 corresponding to the operation amount Stj. In the process until reaching Qb, the position of the spool 28a is stably reached without being affected by the fluctuation of the load or the like.

  In FIG. 6, reference symbols St1 and St2 indicate the range of intermediate operations. In general, in this range, the operator feels a lot of discomfort during operation of the hydraulic actuator that is being operated. Therefore, stable driving of the hydraulic actuator that is faithful to the operation command is required.

  On the other hand, if natural vibration has occurred in the structure in a state where the signal SG2 from the above-described external signal generation unit 32A is supplied, the vibration waveform of the natural vibration is phase-inverted and the gain thereof is adjusted to obtain the signal SG1. Is superimposed on the signal SG2 by the adding unit, and the external signal Z is generated by the electro-oil converting unit 32b. The spool 28a is vibrated in the axial direction by the pressure component of the signal SG1 in the external signal Z, thereby changing the command pressure Pm to the pump flow rate adjusting mechanism 26. As a result, the discharge pressure of the pump 22 is detected. It acts to cancel out the natural vibration waveform.

  Although the natural frequency of the structure depends on the size and weight of the hydraulic excavator, it is about several hertz at the maximum. The time interval of one cycle is the electrical processing for generating the phase inversion signal and the position change of the spool 28a. Since the time required for the pressure signal Pm to be reflected in the rolling angle of the swash plate 24, that is, the time required for the external signal Z to be reflected in the pump discharge amount via the differential pressure adjusting means 28 is sufficiently large, vibration suppression is suppressed. It can be done accurately and quickly.

  Although the preferred embodiments of the present invention have been described with reference to the drawings, those skilled in the art can make various modifications based on these disclosed examples. For example, in FIG. 5B, the external signal generation unit 32A electrically performs function conversion processing, but equivalent conversion processing can also be configured by a hydraulic circuit.

  Further, the signal Ein uses the high voltage selection means 30, but this is not necessarily limited to this. During the operation of the construction machine, the operator operates an electric signal generator provided separately from the high voltage selection means to generate the signal Ein. It is also possible to form

It is a figure showing the schematic structure of the whole hydraulic excavator to which the present invention is applied. It is a block diagram explaining the concept of this invention. FIG. 3 is a schematic diagram of a hydraulic circuit in which the concept shown in FIG. 2 is applied to a positive control system of a variable displacement pump. In FIG. 3, it is a figure which shows typically the state which added the other Example of the external signal generation part. It is a figure explaining a vibration suppression signal generation part. It is a figure explaining the function of the external signal generation part of FIG. It is a graph for demonstrating the flow volume characteristic of the switching control valve of FIG. It is a hydraulic circuit diagram of positive control control of a conventional general variable displacement pump. It is a hydraulic circuit diagram of the negative control of the conventional general variable displacement pump. It is a hydraulic circuit diagram of load sensing control of a conventional general variable displacement pump. It is a conceptual diagram of the system which controls the discharge flow volume of the conventional variable displacement pump by a discharge capacity adjustment part. It is a graph explaining presence of the discomfort felt when an operator operates a hydraulic actuator.

Explanation of symbols

6 slewing base 8 cab 10 hydraulic actuator 14 operator operation command section 20 switching control valve 22 variable displacement pump 24 swash plate 26 discharge flow rate adjusting mechanism (swash plate angle adjusting mechanism)
26a Oil chamber 26b Spring 28 Differential pressure adjusting means 28a Spool 28b Spring 28c Stopper 30 High pressure selecting means 32A External signal generating unit 32a Oil-electric converting unit 32b Electro-oil converting unit 34 Push button 100 Vibration suppression signal generating unit 100a Vibration detecting unit 100b Inherent Vibration generation determination unit 100c Phase inversion waveform generation unit 102 Addition unit D1, D2, D3 Large diameter portion H Opening L1, L2, L3 Line Pd Discharge pressure Ps Maximum detection load pressure PT1, PT2, PT3, PT4, PT5 port RM1, RM2, RM3, RM4, RM5 Oil chamber S1, S2, S3 Sensor SG1 First external signal SG2 Second external signal X Operation command pressure Z External signal

Claims (3)

Adjust the discharge flow rate of the variable displacement pump according to the flow rate adjustment signal given according to the operation amount of the operation valve, detect the hydraulic actuator pressure, and detect the differential pressure between the meter-in side pump pressure of the switching control valve and the hydraulic actuator pressure In the hydraulic control device for a construction machine having a differential pressure adjusting means for adjusting the flow rate adjustment signal so as to maintain the flow rate below a predetermined value,
The differential pressure adjusting means is configured to adjust by a first external signal having a waveform that suppresses vibration of a construction machine structure that occurs according to an operation state of a hydraulic actuator of the construction machine ,
The hydraulic control device for a construction machine , wherein the waveform for suppressing the vibration of the construction machine structure is a waveform obtained by inverting the phase of the vibration waveform of the construction machine structure .   The differential pressure adjusting means is a flow rate given in accordance with a first external signal having a waveform that suppresses vibration of a construction machine structure generated according to an operation state of a hydraulic actuator of the construction machine and an operation amount of the operation valve. 2. The hydraulic control device for a construction machine according to claim 1, wherein the adjustment is made by an external signal obtained by adding a second external signal generated by function generating means for giving an adjustment signal as a function value of an electric signal obtained by hydroelectric conversion. . The differential pressure adjusting means has a valve body structure in which a spool is housed therein, and is formed on one end portion side of the spool to guide the load detection pressure of the hydraulic actuator and attach the spool toward the other end portion. A first oil chamber (RM1) having a spring to be energized, and a second oil chamber (RM2) arranged on the other end side of the spool so as to face the first oil chamber and guided by the meter-in side pump pressure. The first and second oil chambers are partitioned by the first and second spool diameter large portions, respectively, and further partitioned by another third spool diameter large portion provided at the center thereof, and The third oil chamber (RM3) connected to the high pressure side flow rate adjustment signal port of the operation valve, the fourth oil chamber (RM4) connected to the tank port, and the spool end surface on the first oil chamber side The external signal is supplied Oil chamber (RM5), characterized by consisting of the variable displacement pump of the swash plate is connected to the oil chamber of the adjusting mechanism and the third swashplate ports, which are formed so as to face the large-diameter outer peripheral surface of the The hydraulic control device for a construction machine according to claim 1 or 2 .

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