JP4949345B2 - Hydraulic pump control device - Google Patents

Description

  The present invention relates to a hydraulic pump control device for construction machinery such as a hydraulic excavator, and in particular, a hydraulic pump that supplies pressure oil discharged from two variable displacement hydraulic pumps to corresponding ones of left and right traveling hydraulic motors, respectively. The present invention relates to a control device.

  Conventionally, when the left and right travel levers are tilted in a common direction when the engine is running at low speed, the pressure oil discharged from each of the two hydraulic pumps is set to the minimum while 2. Description of the Related Art A variable displacement hydraulic pump control device that supplies power to a corresponding one of traveling hydraulic motors is known (see, for example, Patent Document 1).

  This variable displacement hydraulic pump control device is in a minimum tilt position fixedly defined in advance (the position at which the discharge amount is stabilized compared to other tilt positions because the swash plate is mechanically fixed). By tilting the swash plate of each hydraulic pump, the hydraulic excavator is allowed to go straight while preventing variations in the discharge amount of each pump as much as possible.

  On the other hand, when the low horsepower mode is selected, when the left and right travel levers are tilted in the same direction, the pressure oil discharged from each of the two hydraulic pumps is set to the maximum while the left and right travel levers are driven to the left and right. 2. Description of the Related Art There is known a hydraulic pump control device that supplies a corresponding hydraulic motor (for example, see Patent Document 2).

  This hydraulic pump control device uses the maximum discharge flow rate fixedly defined by the stopper to prevent variations in the discharge rate of each pump as much as possible, and to generate skew when the hydraulic excavator runs straight ahead. To prevent.

  However, in the hydraulic pump control devices described in Patent Documents 1 and 2, the discharge amount of the left and right hydraulic pumps is less varied by mechanical means such as a stopper (maximum setting or minimum setting). If this is not done, the hydraulic excavator cannot travel straight ahead.

  Further, in the hydraulic pump control device described in Patent Documents 1 and 2, the discharge amount is fixed by mechanical means such as a stopper, as in the case where there is a difference in internal leakage of the hydraulic pump or the traveling hydraulic motor. However, when the variation between the left and right becomes large, the hydraulic excavator can no longer go straight.

On the other hand, a tuning circuit that realizes straight traveling of a hydraulic excavator by increasing or decreasing the discharge amount of either the left or right hydraulic pump based on the pressure difference downstream of the left and right traveling hydraulic motors is known. (For example, see Patent Document 3).
JP-A-6-137309 Japanese Patent Laid-Open No. 7-34488 Japanese Patent Laid-Open No. 11-132202

  However, the tuning circuit described in Patent Document 3 defines a state in which there is no pressure difference downstream of the left and right traveling hydraulic motors as a state in which the hydraulic excavator is traveling straight, and then the left and right traveling hydraulic motors. A throttle is provided on each downstream side, and the pressure generated by the throttle is applied as a signal pressure in a direction facing the servo piston for operating the pump swash plate, and the servo piston is displaced by the pressure difference. By adjusting the tilt angle of the pump swash plate, the discharge amount of one of the hydraulic pumps is automatically increased and decreased to try to eliminate the pressure difference. In addition, there is no difference in the flow rate of the left and right traveling hydraulic motors, and there is no difference in the flow rate from the downstream side of the traveling hydraulic motor to the direction control valve, or from the direction control valve to the throttle. If internal leakage amount as different left and right travel hydraulic motor of the hydraulic fluid in line, there is a possibility that rather would promote the curvilinear progression traveling of the hydraulic excavator.

  Furthermore, when adjusting the tilt angle of the left and right hydraulic pumps using the electromagnetic proportional valve, it is possible to prevent skewing and meandering of the fuselage caused by variations in the magnetic hysteresis characteristics of the electromagnetic proportional valve and the spring constant of the tilt regulator. It ’s hard to say that it ’s a radical solution.

  In view of the above-described points, an object of the present invention is to provide a hydraulic pump control device that can improve traveling straightness when the traveling straightness of a construction machine is deteriorated.

  To achieve the above object, a hydraulic pump control device according to a first aspect of the present invention is a hydraulic pump mounted on a construction machine having two hydraulic pumps with variable discharge amounts corresponding to the left and right traveling hydraulic motors, respectively. A control device that detects lever operation detecting means for detecting the operation content of the left and right traveling levers for operating each of the left and right traveling hydraulic motors, and detects a first physical quantity that is an indicator of a traveling state of the construction machine; A traveling state detecting means; a discharge amount increasing / decreasing means for individually increasing / decreasing the discharge amount by changing a controllable second physical quantity serving as an index of the discharge amount of each of the two hydraulic pumps; and a lever for straight traveling When the operation is performed and when it is detected that there is a difference between the discharge amounts of the two hydraulic pumps based on the first physical amount, the discharge amount is increased or decreased by the discharge amount increasing / decreasing means. Increase / decrease, and based on the first physical quantity after the increase / decrease, the second physical quantity when it is detected that the discharge quantities of the two hydraulic pumps substantially match each other is the discharge quantity of the two hydraulic pumps when traveling straight ahead. The straight traveling condition recording means for recording as the straight traveling condition to be determined respectively, and when it is detected that the lever operation for the straight traveling is performed, the straight traveling condition is referred to and the first traveling condition recorded as the straight traveling condition is recorded. And straight running condition reproducing means for reproducing the discharge amounts of the two hydraulic pumps based on two physical quantities.

  Further, the second invention is a hydraulic pump control device according to the first invention, wherein the discharge amount increasing / decreasing means adjusts a control pressure introduced into a regulator for controlling the discharge amount of the hydraulic pump. A pressure control valve is individually provided for each hydraulic pump, and the first physical quantity is a discharge pressure of each of the two hydraulic pumps or a discharge pressure of each of the left and right traveling hydraulic motors, and the second physical quantity Is a control command value of the electromagnetic pressure control valve.

  With the above-described means, the present invention can provide a hydraulic pump control device that can improve the straight travel performance of the construction machine when the straight travel performance of the construction machine deteriorates.

  Embodiments of the present invention will be described below.

  FIG. 1 is a perspective view of a hydraulic excavator 1 equipped with a hydraulic pump control device according to the present invention. The hydraulic excavator 1 is mounted on a lower traveling body 2 and a lower traveling body 2 via a turning mechanism. And an upper swing body 3.

  The lower traveling body 2 includes left and right crawlers 2L and 2R, and causes the excavator 1 to move forward, backward, turn, or bend. Further, the upper swing body 3 includes a boom 4, an arm 5 and a bucket 6, and a drilling attachment including a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9 as hydraulic cylinders for driving them.

  FIG. 2 is a hydraulic circuit diagram of the hydraulic pump control device according to the present invention. The hydraulic pump control device 100 is driven by an engine or an electric motor, and the discharge amount (cc / rev) per rotation is variable. Pressure is supplied from the two hydraulic pumps 10L, 10R to the pressure oil tank 22 through the center bypass conduit 30L that communicates the switching valves 12L, 13L, and 14L or the center bypass conduit 30R that communicates the switching valves 12R, 13R, and 14R. Circulate the oil.

  The switching valves 12L and 12R are spool valves that switch the flow of pressure oil so that the hydraulic oil discharged from the hydraulic pumps 10L and 10R is circulated by the traveling hydraulic motors 42L and 42R, respectively.

  Further, the switching valve 13L is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged from the hydraulic pump 10L by the turning hydraulic motor 44. The switching valve 13R is a pressure oil discharged from the hydraulic pump 10R. Is a spool valve that switches the flow of pressure oil to discharge the pressure oil in the boom cylinder 7 to the pressure oil tank 22.

  The switching valve 14L is a spool valve that switches the flow of pressure oil in order to supply the pressure oil discharged from the hydraulic pump 10L to the arm cylinder 8 and to discharge the pressure oil in the arm cylinder 8 to the pressure oil tank 22. The switching valve 14R is a spool valve that supplies the pressure oil discharged from the hydraulic pump 10R to the bucket cylinder 9 and switches the flow of the pressure oil to discharge the pressure oil in the bucket cylinder 9 to the pressure oil tank 22. is there.

  The center bypass pipes 30L, 30R are respectively provided with negative control throttles 20L, 20R between the switching valves 14L, 14R and the pressure oil tank 22 located on the most downstream side, and the flow of the pressure oil discharged by the hydraulic pumps 10L, 10R. Is a pressure oil line that generates a control pressure (hereinafter referred to as “negative control pressure”) for controlling the hydraulic pump regulators 40L and 40R upstream of the negative control throttles 20L and 20R.

  The control pressure lines 32L and 32R indicated by broken lines are control pressure lines for transmitting the negative control pressure generated upstream of the negative control throttles 20L and 20R to the hydraulic pump regulators 40L and 40R.

  Here, the hydraulic pump regulators 40L and 40R will be described with reference to FIG. FIG. 3 is an enlarged view of region III in FIG. 2, and is a schematic diagram of a hydraulic pump regulator 40R. Note that the hydraulic pump regulator 40L is symmetrical with the hydraulic pump regulator 40R and is not shown in the figure.

  The hydraulic pump regulator 40R includes a tilt actuator 41R for tilting and driving a swash plate (yoke) for changing the pump capacity of the hydraulic pump 10R to control the discharge amount of the hydraulic pump 10R, and the tilt actuator 41R. A spool valve mechanism 70R for supplying and discharging pressure oil, a total horsepower controller 53R for displacing the spool valve 700R of the spool valve mechanism 70R during full horsepower control, and a spool valve 700R for negative control control. And a feedback lever 72R for feeding back the drive displacement of the tilting actuator 41R to the spool valve 700R.

  The tilting actuator 41R corresponds to the operating piston 410R having the large diameter pressure receiving part PR1 at one end and the small diameter pressure receiving part PR2 at the other end, the pressure receiving chamber 411R corresponding to the large diameter pressure receiving part PR1, and the small diameter pressure receiving part PR2. The pressure receiving chamber 412R is configured such that the discharge pressure P2 of the hydraulic pump 10R is introduced into the pressure receiving chamber 411R through the spool valve 700R, or the pressure oil is discharged from the pressure receiving chamber 411R through the spool valve 700R to the pressure receiving chamber 412R. The discharge pressure P2 of the hydraulic pump 10R is respectively introduced. When the pressure oil is introduced into the pressure receiving chamber 411R and displaced toward the pressure receiving chamber 412R, the operating piston 410R drives the swash plate (yoke) of the hydraulic pump 10R to tilt toward the small flow rate.

  The spool valve mechanism 70R has a first port into which the discharge pressure P2 of the hydraulic pump 10R is introduced, a second port communicating with the pressure oil tank 22, and an output port communicating with the pressure receiving chamber 411R. A first position for communicating the port and the output port (a chamber on the left side of the spool valve 700R), a second position for communicating the second port and the output port (a chamber on the right side of the spool valve 700R), or the first port, A spool valve 700R that is selectively switched to a neutral position where neither of the two ports communicates with the output port (a central chamber of the spool valve 700R), and a spring 701R that biases the spool valve 700R in a direction to displace it to the second position. It consists of.

  The total horsepower control unit 53R includes a servo piston 530R that can be pressed in a direction in which the spool valve 700R is displaced to the first position, a spring 531R that returns the servo piston 530R from the pressed state, and a pressure receiving unit PR3 provided in the servo piston 530R. Corresponding to the pressure receiving chamber 532R into which the discharge pressure P2 of the hydraulic pump 10R is introduced, the pressure receiving chamber 533R into which the discharge pressure P1 of the hydraulic pump 10L is introduced corresponding to the pressure receiving portion PR4, and the electromagnetic wave described later corresponding to the pressure receiving portion PR5. A pressure receiving chamber 534R into which the control pressure of the valve 52 is introduced. In the total horsepower controller 53L, the discharge pressure P1 of the hydraulic pump 10L is introduced into the pressure receiving chamber 532L, and the discharge pressure P2 of the hydraulic pump 10R is introduced into the pressure receiving chamber 533L.

  The negative control unit 71R includes a servo piston 710R that can be pressed in a direction to displace the spool valve 700R to the first position, a spring 711R that returns the servo piston 710R from the pressed state, and a pressure receiving unit PR6 provided in the servo piston 710R. Correspondingly, it comprises a pressure receiving chamber 712R into which a control pressure of the control pressure line 32R or a control pressure of an electromagnetic valve 51R described later is introduced via the shuttle valve 73R.

  In the feedback lever 72R, the spool valve 700R is switched to the first position or the second position by the displacement of the servo piston 530R or the servo piston 710R, pressure oil is introduced into the pressure receiving chamber 411R, or pressure oil is discharged from the pressure receiving chamber 411R. Thus, when the operating piston 410R moves, the movement amount is physically fed back to the spool valve 700R to return to the neutral position.

  With this configuration, the hydraulic pump regulator 40R decreases the discharge amount of the hydraulic pump 10R as the control pressure introduced to the servo piston 530R or the servo piston 710R increases, and the hydraulic pump 10R decreases as the introduced control pressure decreases. The discharge amount is increased.

  As shown in FIG. 2, when any hydraulic actuator in the hydraulic excavator 1 is not used (hereinafter referred to as “standby mode”), the hydraulic oil discharged from the hydraulic pumps 10L and 10R has a minimum flow rate. However, at this time, the negative control pressure generated upstream of the negative control throttles 20L and 20R through the center bypass pipes 30L and 30R becomes a predetermined pressure via the shuttle valves 73L and 73R by the control pressure pipes 32L and 32R. This is transmitted to the hydraulic pump regulators 40L and 40R.

  The hydraulic pump regulators 40L and 40R displace the spool valves 700L and 700R at positions corresponding to the negative control pressure introduced into the negative control units 71L and 71R, and the tilt actuators 41L and 41R are interlocked with the displacement. Driven to reduce the discharge amount of the hydraulic pumps 10L, 10R to the minimum discharge amount, and as a result, suppress the pressure loss (pumping loss) when the discharged pressure oil passes through the center bypass pipelines 30L, 30R. To do.

  On the other hand, when any hydraulic actuator in the hydraulic excavator 1 is used, the pressure oil discharged from the hydraulic pumps 10L and 10R flows into the hydraulic actuator via the switching valve corresponding to the hydraulic actuator, and the negative control throttle 20L. , 20R is further reduced or eliminated, and the negative control pressure generated upstream of the negative control throttles 20L and 20R is reduced to below a predetermined pressure.

  As a result, the hydraulic pump regulators 40L and 40R increase the discharge amount of the hydraulic pumps 10L and 10R to a level corresponding to the negative control pressure, circulate sufficient pressure oil to each hydraulic actuator, and ensure that each actuator is driven. It shall be

  With the above-described configuration, the hydraulic pump control device 100 causes wasteful energy consumption in the hydraulic pumps 10L and 10R (pressure oil discharged from the hydraulic pumps 10L and 10R is generated in the center bypass pipes 30L and 30R in the standby mode. In the case where various hydraulic actuators are operated while suppressing the pumping loss), necessary and sufficient pressure oil can be reliably supplied to the various hydraulic actuators from the hydraulic pumps 10L and 10R.

  The traveling levers 46L and 46R are remote control valves for stroking the switching valves 12L and 12R corresponding to the left and right traveling hydraulic motors 42L and 42R, respectively, and levers using the pressure oil discharged by the control pump 50 are used. A control pressure corresponding to the operation amount is introduced into either the left or right pilot port of the switching valves 12L, 12R.

  A boom operation lever, an arm operation lever, a bucket operation lever, and a turning lever (all not shown) respectively operate the raising and lowering of the boom 4, the raising and lowering of the arm 5, the opening and closing of the bucket 6, and the turning of the upper turning body 3. As with the traveling levers 46L and 46R, the control pressure corresponding to the lever operation amount is made using the pressure oil discharged from the control pump 50, and the corresponding switching valves 13L, 13R, 14L, It is introduced into either the left or right pilot port of 14R.

  The control pump 50 discharges the original pressure to the electromagnetic valves 51L, 51R, 52 for regulating the control pressure flowing through the control pressure lines 35L, 35R, 37 in addition to the control pressure oil supplied to the various operation levers. The hydraulic pump is a fixed displacement hydraulic pump that continuously discharges control pressure oil at a predetermined discharge pressure (for example, 4 MPa).

The electromagnetic valves 51L, 51R, 52 are electromagnetic proportional pressure reducing valves (pressure control valves) disposed on the control pressure lines 35L, 35R, 37, respectively, and correspond to the magnitude of the current supplied from the main controller 60. The control pressure in the control pressure lines 35L, 35R, 37 is adjusted. The electromagnetic valve 52 is an electromagnetic proportional pressure reducing valve used for so-called speed sensing control that changes the discharge amount of the hydraulic pumps 10L and 10R according to the rotation speed of the engine or the electric motor. The pressure sensors PS1, PS2, and PS9 are These are sensors for measuring the control pressure in the control pressure lines 35L, 35R, 37, respectively, and the pressure sensors PS3, PS4 are for detecting the control pressure generated according to the lever operation amount of the left travel lever 46L. Sensor.

  The pressure sensors PS5 and PS6 are sensors for detecting the control pressure generated according to the lever operation amount of the right travel lever 46R, and the pressure sensors PS7 and PS8 are the discharge pressures of the hydraulic pumps 10L and 10R, respectively. It is a sensor for detecting.

  The main controller 60 includes a computer having a CPU (Central Processing Unit), RAM (Random Access Memory), NVRAM (Non-Volatile Random Access Memory), ROM (Read Only Memory), etc. While storing programs corresponding to each of the detecting means, the discharge amount increasing / decreasing means, the straight traveling condition recording means, and the straight traveling condition reproducing means in the ROM, the CPU is caused to execute processing corresponding to each means.

  The lever operation detection means is a means for detecting the operation contents of the lever. For example, while receiving the outputs of the pressure sensors PS3 to PS6, the lever operation amount, the operation direction, the tilting speed, etc. of the travel levers 46L and 46R are detected. To detect.

  The traveling state detection means is a means for detecting a physical quantity that serves as an indicator of the traveling state of the hydraulic excavator 1. For example, the traveling state detection means receives the outputs of the pressure sensors PS7 and PS8 and changes the discharge pressures of the hydraulic pumps 10L and 10R in the traveling state. Detect as an indicator.

  The traveling state detection means receives the output of a pressure sensor (not shown) that measures the pressure generated by the throttle disposed between each of the traveling hydraulic motors 42L and 42R and the pressure oil tank 22. The running state may be detected while detecting the discharge pressure of the running hydraulic motors 42L and 42R.

  The discharge amount increasing / decreasing means is a means for individually increasing / decreasing the discharge amounts of the hydraulic pumps 10L, 10R, and is introduced into the hydraulic pump regulators 40L, 40R while controlling the control current supplied to the solenoid valves 51L, 51R. The control pressure is adjusted, and the discharge amounts of the hydraulic pumps 10L and 10R are individually increased or decreased.

  The straight travel condition recording means is a means for recording the straight travel condition. For example, an operation (an operation in the same direction) for causing the hydraulic excavator 1 to move straight forward by a maximum operation amount by the lever operation detection means is performed. It is detected that the learning switch 61 is on, and it is detected that the discharge pressures P1 and P2 of the hydraulic pumps 10L and 10R detected by the running state detecting means are greater than a predetermined value ΔP1. In addition, after the start of tilting of the left and right traveling levers, when the fluctuation ranges of the discharge pressures of the hydraulic pumps 10L and 10R within a predetermined period are within a predetermined range, the traveling straightness improving process is executed.

  The learning switch 61 is a switch for selecting execution / non-execution of the traveling straightness improvement process. For example, the learning switch 61 is an on / off switch installed in the cab, and receives a control signal indicating on / off of the switch. Output to the main controller 60.

  The “straight running condition” is a command value of the control current of the solenoid valves 51L and 51R when the excavator 1 is caused to travel straight. For example, an intermediate output of the solenoid valves 51L and 51R (between the minimum value and the maximum value). Command current values set so that the hydraulic pumps 10L and 10R have the maximum discharge amount are set individually as initial values when the excavator 1 is shipped. Has been.

  The “traveling straightness improving process” refers to a process for improving the traveling straightness of the lower traveling body 2 that is curved on a flat ground, and an electromagnetic that adjusts the control pressure introduced into each of the hydraulic pump regulators 40L and 40R. Change the command value of the control current for the valves 51L and 51R to reduce the discharge amount of the hydraulic pump with the higher discharge pressure, or increase the discharge amount of the hydraulic pump with the lower discharge pressure. A straight traveling state is ensured, and the command value of the control current of the solenoid valves 51L and 51R when the straight traveling state is reached is recorded in the NVRAM as a straight traveling condition. The straight traveling condition recording means records the initial value of the control current of the solenoid valves 51L and 51R in a fixed manner, and records only the amount of increase / decrease relative to the initial value of the command value of the control current. May be.

  The straight travel condition reproduction means is a means for reproducing the straight travel condition recorded in the NVRAM. For example, when the travel levers 46L and 46R are operated so that the excavator 1 moves straight forward, the straight travel condition Referring to FIG. 4, the discharge pressures of the hydraulic pumps 10L and 10R are set by adjusting the magnitude of the control pressure introduced into the hydraulic pump regulators 40L and 40R by the electromagnetic valves 51L and 51R.

  Next, the straight traveling performance improvement process will be described with reference to FIGS.

  FIG. 4 is a diagram showing the relationship between the travel path of the lower traveling body 2 and the discharge amounts and discharge pressures of the hydraulic pumps 10L and 10R. FIG. FIG. 4B is a graph showing a temporal transition of the discharge amount of the hydraulic pumps 10L and 10R, and FIG. 4C is a graph showing a temporal transition of the discharge pressure of the hydraulic pumps 10L and 10R. It is a graph to show.

  FIG. 5 is a hydraulic circuit diagram showing the state of the hydraulic pump control device 100 when both the left and right traveling levers 46L and 46R are tilted in the forward direction by the maximum lever operation amount, and the left and right crawlers 2L, This shows a state in which there is no variation in the rotational speed of 2R, and the lower traveling body 2 is traveling straight as intended by the operator, and there is no need to improve traveling straightness by the straight traveling condition recording means.

  On the other hand, FIG. 6 is a hydraulic circuit diagram showing a state of the hydraulic pump control device 100 when both the left and right traveling levers 46L and 46R are tilted in the forward direction by the maximum lever operation amount, as in FIG. However, since the rotational speeds of the left and right crawlers 2L and 2R vary and the lower traveling body 2 is slightly bent to the left against the intention of the operator, the straight traveling performance is improved by the straight traveling condition recording means. Indicates the state in which

  As shown in FIG. 4A, when the left and right traveling levers 46L and 46R are tilted by the maximum lever operation amount in the forward direction, the lower traveling body 2 essentially goes straight along the movement path R1. The discharge amount of the hydraulic pumps 10L and 10R, which should be essentially the same, due to changes over time and initial variations of the magnetic hysteresis characteristics of the solenoid valves 51L and 51R, changes over time and initial variations of the spring constants of the hydraulic pump regulators 40L and 40R, etc. When the rotational speed of the right crawler 2R becomes larger than the rotational speed of the left crawler 2L due to a difference or the like, the vehicle travels along the movement path R3.

  At this time, as shown in FIG. 4B, the discharge amount of the hydraulic pump 10R is Q2, and the discharge amount of the hydraulic pump 10L is Q1, which is smaller than Q2, so the traveling hydraulic motor 42R travels. The rotational speed becomes higher than that of the hydraulic motor 42L, and the lower traveling body 2 is bent.

  Normally, when the left and right traveling levers 46L and 46R are tilted in the forward direction by the maximum lever operation amount, the switching valves 12L and 12R receive the control pressure from the left and right traveling levers 46L and 46R at the pilot ports, respectively, and spools. Stroke and supply the hydraulic oil discharged from the hydraulic pumps 10L and 10R to the traveling hydraulic motors 42L and 42R at the maximum flow rate of the spool (in FIG. 5, the flow of the hydraulic oil discharged from the hydraulic pumps 10L and 10R is black The left and right crawlers 2L and 2R are rotated at the same speed in the forward direction.

  However, when the rotational speed of the traveling hydraulic motor 42R becomes higher than that of the traveling hydraulic motor 42L due to a difference in the discharge amount of the hydraulic pumps 10L and 10R, the right crawler 2R is relatively more than the left crawler 2L. In order to move forward, the lower traveling body 2 turns. At this time, the traveling hydraulic motor 42R that drives the right crawler 2R also bears a load that pulls the left crawler 2L, which is relatively delayed in advance, and the discharge pressure of the hydraulic pump 10R increases due to the increase in the load. Conversely, when the traveling hydraulic motor 42R bears a part of the load, the traveling hydraulic motor 42L that drives the left crawler 2L reduces the driving load, and the discharge pressure of the hydraulic pump 10L decreases. Therefore, in such a state, as shown in FIG. 4C, a large difference occurs in the discharge pressures P1 and P2 of the hydraulic pumps 10L and 10R.

  The main controller 60 detects that the left and right travel levers 46L and 46R are tilted by the maximum lever operation amount in the forward direction based on the outputs of the pressure sensors PS4 and PS6 by the lever operation detection means.

  The main controller 60 detects the discharge pressures P1 and P2 of the hydraulic pumps 10L and 10R by receiving the outputs of the pressure sensors PS7 and PS8 by the traveling state detection means, and discharges pressures P1 and P2 by the straight traveling condition recording means. It is detected that there is a difference greater than or equal to a predetermined value ΔP1.

  Further, the main controller 60 detects that the learning switch 61 is turned on, and the discharge pressures P1 and P2 during the predetermined time from the start of the straight traveling are within the predetermined fluctuation range by the straight traveling condition recording unit. It is monitored whether or not.

  After a predetermined time has passed without any fluctuation, at time T1, the straight traveling condition recording means is supplied to the electromagnetic valve 51R by the discharge amount increasing / decreasing means so as to decrease the discharge amount of the hydraulic pump 10R having a high discharge pressure. The command value of the control current is increased with a predetermined width for each processing cycle.

  Receiving the control current increase command, the electromagnetic valve 51R adjusts the pressure oil discharged from the control pump 50 to increase the pressure in the control pressure line 35R.

  The pressure oil in the control pressure line 35R raised to the pressure corresponding to the control current reaches the hydraulic pump regulator 40R via the shuttle valve 73R (see arrow AR1 in FIG. 6), and as a result, the hydraulic pump 10R. Reduce the discharge amount.

  The hydraulic pump 10R whose discharge amount has been reduced reduces the flow rate of the pressure oil supplied to the traveling hydraulic motor 42R (in FIG. 6, the flow of the pressure oil whose flow rate has been reduced is indicated by a thick gray arrow. And the rotational speed of the right crawler 2R is decreased.

  The controller 60 repeats the process until it detects that the difference between the discharge pressures P1 and P2 is equal to or less than a predetermined value ΔP2 (a small value close to zero) by the straight traveling condition recording means, and the left and right crawlers 2L and 2R Synchronize the rotation speed.

  FIG. 4B shows that at time T1, the discharge amount increasing / decreasing means starts the process of increasing the command value of the control current supplied to the electromagnetic valve 51R, and the hydraulic oil for traveling 42R that rotates the right crawler 2R is pressurized with oil. 4C shows that the discharge amount of the hydraulic pump 10R that supplies the pressure starts to decrease, and FIG. 4C shows a process for increasing the command value of the control current supplied to the electromagnetic valve 51R by the discharge amount increasing / decreasing means at time T1. This indicates that the discharge pressure of the hydraulic pump 10R starts to decrease and the discharge pressure of the hydraulic pump 10L starts to increase.

  In FIG. 4B, at time T2, when the discharge amount of the hydraulic pump 10L decreases to the value Q1, the increase process of the command value of the control current supplied to the electromagnetic valve 51R by the discharge amount increasing / decreasing means is completed. FIG. 4C shows a state where the discharge pressure of the hydraulic pump 10R and the discharge pressure of the hydraulic pump 10L substantially match at time T2 (the difference between the discharge pressures P1 and P2 is equal to or less than a predetermined value ΔP2. ).

  The controller 60 records the command value of the control current of the solenoid valves 51L and 51R at the time T2 in the NVRAM as the straight traveling condition by the straight traveling condition recording means.

  In detail, since the solenoid valves 51L and 51R have an upper limit value and a lower limit value in the command value of the control current, the upper limit value is reached by the process of increasing the control current of the solenoid valve 51R. Is switched to the process of reducing the control current of the solenoid valve 51L. Also in this case, the command value of the control current supplied to the electromagnetic valve 51L is reduced by a predetermined amount for each processing cycle.

  In this way, the rotation speed of the right crawler 2R with the faster rotation is synchronized with the rotation speed of the left crawler 2L with the lower rotation, and as shown by the movement path R2 in FIG. The straight running performance of No. 2 is improved.

  Next, the flow of the straight traveling improvement process will be described with reference to FIG. FIG. 7 is a flowchart showing the flow of the straight travel improvement process. The main controller 60 is a case where both the left and right travel levers are tilted in the forward direction by the maximum lever operation amount, and the learning switch 61 Is executed, and when the fluctuation range of the discharge pressures of the hydraulic pumps 10L and 10R within a predetermined period is within a predetermined range after the left and right traveling levers start to tilt, this straight traveling improvement process is executed. Shall.

  Note that the lower traveling body 2 of the hydraulic excavator 1 moves forward while slightly turning leftward when this traveling straightness improving process is not performed, and follows the movement route R3 in FIG.

  First, the main controller 60 determines which of the two hydraulic pumps 10L and 10R is a hydraulic pump having a high discharge pressure (step S1).

  When the hydraulic pump having a high discharge pressure is the hydraulic pump 10L (the left hydraulic pump in step S1), the main controller 60 determines that the value obtained by adding the predetermined width ΔI to the command value of the current control current of the solenoid valve 51L is the solenoid valve 51L. It is determined whether or not it is equal to or less than the upper limit value in the control (step S2).

  When it is determined that the value obtained by adding the predetermined width ΔI to the command value of the current control current of the solenoid valve 51L is equal to or less than the upper limit value for control of the solenoid valve 51L (less than the upper limit value of step S2), the main controller 60 Then, the command value of the control current of the electromagnetic valve 51L is increased by a predetermined width ΔI, and the discharge amount of the hydraulic pump 10L is decreased (step S3).

  On the other hand, when it is determined that the value obtained by adding the predetermined width ΔI to the current control current command value of the solenoid valve 51L exceeds the upper limit value in the control of the solenoid valve 51L (exceeding the upper limit value in step S2), the main The controller 60 determines whether or not the value obtained by subtracting the predetermined width ΔI from the command value of the current control current of the solenoid valve 51R is equal to or greater than the lower limit value in the control of the solenoid valve 51R (step S4).

  When it is determined that the value obtained by subtracting the predetermined width ΔI from the command value of the current control current of the solenoid valve 51R is equal to or greater than the lower limit value in control of the solenoid valve 51R (greater than the lower limit value of step S4), the main controller 60 Then, the command value of the control current of the electromagnetic valve 51R is decreased by a predetermined width ΔI, and the discharge amount of the hydraulic pump 10R is increased (step S5).

  When it is determined that the value obtained by subtracting the predetermined width ΔI from the command value of the current control current of the solenoid valve 51R is less than the lower limit value on the control of the solenoid valve 51R (less than the lower limit value of step S4), the main controller 60 Then, the failure flag is set and the process is terminated (step S6).

  When the hydraulic pump with high discharge pressure is the hydraulic pump 10R (the right hydraulic pump in step S1), the main controller 60 instructs the control current of the solenoid valve 51R in the same manner as when the hydraulic pump with high discharge pressure is the hydraulic pump 10L. The value is increased by a predetermined width ΔI within a range not exceeding the control upper limit value, and the discharge amount of the hydraulic pump 10R is decreased (step S7, step S8), or the control current command value of the solenoid valve 51L Is decreased by a predetermined width ΔI within a range that does not fall below the lower limit value for control, and the discharge amount of the hydraulic pump 10L is increased (steps S9 and S10).

  Thereafter, the main controller 60 determines whether or not the difference between the discharge pressures P1 and P2 is equal to or less than a predetermined value ΔP2 (step S12), and the control current of the electromagnetic valves 51L and 51R at the time when the difference becomes equal to or less than the predetermined value ΔP2. The command value is recorded in the NVRAM as a straight traveling condition, and the process is terminated (step S13). When the difference between the discharge pressures P1 and P2 is not less than or equal to the predetermined value ΔP2, the process is returned and steps S1 to S12 are repeated.

  When the lever operation detecting unit detects that the straight traveling state by the maximum operation is released, or when the controller 60 detects that the learning switch 61 is turned off, the straight traveling improvement processing is performed. Cancel.

  Thus, the command value of the control current of the solenoid valves 51L and 51R during straight travel recorded by the straight travel performance improving process is applied during normal straight travel by the straight travel condition reproducing means, and the hydraulic pump 10L. The discharge amount of 10R is kept the same.

  In this way, since the rotational speed of the right crawler 2R having the higher rotational speed is decreased and the rotational speeds of the left and right crawlers 2L and 2R are synchronized, the straight traveling performance of the lower traveling body 2 is improved. The rotation speeds of the left and right crawlers 2L and 2R can be synchronized even when at least one of 10L and 10R has already discharged the pressure oil at the maximum discharge amount.

  Further, the main controller 60 can record the improvement contents of the straight traveling performance in the NVRAM and reproduce the improvement contents at the next straight traveling, so that it is possible to avoid forcing the operator to execute the improvement process. it can. In addition, when traveling straight ahead, the discharge amounts of the hydraulic pumps 10L and 10R are reproduced in advance based on the details of the improvement. Does not occur.

  With the above configuration, the hydraulic pump control device 100 individually corrects the discharge amount of the hydraulic pumps 10L and 10R to cancel out the difference in rotational speed between the left and right crawlers 2L and 2R, so that the traveling straightness of the lower traveling body 2 is improved. Can be improved.

  In addition, the hydraulic pump control apparatus 100 has the right and left crawlers 2L, 2R in spite of the fact that the hydraulic pump regulators 40L, 40R operate normally and the hydraulic pumps 10L, 10R discharge the pressure oil with the same discharge amount. Even when the lower traveling body 2 varies and the lower traveling body 2 bends, the discharge amounts of the hydraulic pumps 10L and 10R are made to be different and the rotation speeds of the left and right crawlers 2L and 2R are changed. By canceling the difference, the straight traveling performance can be improved.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are within the scope of the gist of the present invention described in the claims. It can be changed.

  For example, in the above-described embodiment, the hydraulic pump control device 100 is configured such that the negative control pressure selectively introduced into the negative control units 71L and 71R via the shuttle valves 73L and 73R (the discharge amounts of the hydraulic pumps 10L and 10R during negative control). Discharge pressure of the hydraulic pumps 10L and 10R according to the control pressure by the solenoid valves 51L and 51R (pressure introduced to improve the straight travel performance during straight travel). However, according to the negative control pressure detected by the sensor, the control pressures of the electromagnetic valves 51L and 51R are controlled not only during straight running but also during negative control. To control the discharge amount of the hydraulic pumps 10L, 10R, the control pressure lines 32L, 32R and the shuttle valves 73L, 7 It may be omitted R.

  Further, in the above-described embodiment, when both the left and right traveling levers are tilted in the forward direction by the maximum lever operation amount, the traveling straightness processing is executed. When the vehicle is tilted in the forward direction by a small predetermined same lever operation amount, the straight traveling processing may be executed.

  Further, in the above-described embodiment, the solenoid valves 51L and 51R are exemplified as those controlled by the current value, but instead of this, the duty control is performed, and the command value of this duty control is used as the straight running condition as the NVRAM. May be recorded.

  Further, in the above-described embodiment, the command value of the control current of the solenoid valves 51L and 51R is increased or decreased by a predetermined width every cycle, but instead of this, the hydraulic pump 10L at that time point, The increase / decrease width may be increased as the difference in the discharge pressure of 10R increases.

  In the above-described embodiment, the process of reducing the discharge amount of the hydraulic pump having a high discharge pressure is executed first, but the process of increasing the discharge amount of the hydraulic pump having a low discharge pressure is executed first. When the lower limit value in the control of the solenoid valves 51L and 51R is reached by this increase process, the process may be switched to a process for reducing the discharge amount of the hydraulic pump having a high discharge pressure.

  Moreover, although the above-mentioned Example demonstrates the case where the hydraulic shovel 1 goes straight ahead, the same description shall be applied also when the hydraulic shovel 1 goes straight back.

Further, in the above-described embodiment, in the hydraulic circuit diagram, the traveling hydraulic motors 42L and 42R that drive the left and right crawlers 2L and 2R and the actuator of any one of the upper swing body 3 (for example, the boom cylinder 7 and the arm cylinder 8). , The bucket cylinder 9 or the turning hydraulic motor 44) is operated at the same time, the pressure is applied to the left and right traveling hydraulic motors 42L and 42R from only the hydraulic pump 10L in order to improve the straightness of the lower traveling body 2. Although the straight traveling valve for circulating the oil is omitted, it does not prevent such a configuration from being applied to the present invention.

1 is a perspective view of a hydraulic excavator equipped with a hydraulic pump control device according to the present invention. It is a hydraulic circuit diagram which shows the state of the hydraulic pump control apparatus which concerns on this invention. It is an enlarged view of the area | region III of FIG. It is a figure which shows the relationship between the movement path | route of a lower traveling body, and the transition of the discharge amount and discharge pressure of a hydraulic pump. FIG. 6 is a hydraulic circuit diagram (No. 1) illustrating a state of the hydraulic pump control device when both the left and right traveling levers are tilted in the forward direction by the same lever operation amount. FIG. 6 is a hydraulic circuit diagram (part 2) illustrating a state of the hydraulic pump control device when both the left and right traveling levers are tilted in the forward direction by the same lever operation amount. It is a flowchart which shows the flow of a driving | running | working straightness improvement process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydraulic excavator 2 ... Lower traveling body 2L, 2R ... Crawler 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8. .... Arm cylinder 9 ... Bucket cylinder 10L, 10R ... Hydraulic pump 12L, 12R, 13L, 13R, 14L, 14R ... Switching valve 20L, 20R ... Negative control throttle 22 ... Pressure oil tank 30L, 30R: Center bypass line 32L, 32R, 35L, 35R ... Control pressure line 40L, 40R ... Regulator for hydraulic pump 41L, 41R ... Tilt actuator 42L, 42R ... For travel Hydraulic motor 44 ... turning hydraulic motor 46L, 46R ... travel lever 50 ... control pump 51L 51R, 52 ... Solenoid valve 53L, 53R ... Total horsepower control unit 60 ... Main controller 61 ... Learning switch 70L, 70R ... Spool valve mechanism 71L, 71R ... Negative control unit 72L 72R ... Feedback lever 73L, 73R ... Shuttle valve 100 ... Hydraulic pump controller PS1-PS9 ... Pressure sensor

Claims (2)

A hydraulic pump control device mounted on a construction machine having two hydraulic pumps with variable discharge amount corresponding to left and right traveling hydraulic motors,
Lever operation detecting means for detecting the operation content of the left and right traveling levers for operating each of the left and right traveling hydraulic motors;
Traveling state detecting means for detecting a first physical quantity serving as an indicator of the traveling state of the construction machine;
A discharge amount increasing / decreasing means for individually increasing or decreasing the discharge amount by changing a controllable second physical quantity serving as an index of the discharge amount of each of the two hydraulic pumps;
When it is detected that there is a difference between the discharge amounts of the two hydraulic pumps based on the first physical quantity, when the lever operation for straight traveling is performed, the discharge amount increasing / decreasing means The second physical quantity when the discharge amount of the two hydraulic pumps is substantially matched based on the first physical quantity after the increase / decrease is detected, and the second physical quantity of the two hydraulic pumps during straight traveling is calculated. Rectilinear travel condition recording means for recording as straight travel conditions for determining each discharge amount;
When it is detected that a lever operation for straight traveling is performed, the discharge amount of each of the two hydraulic pumps is referred to based on the second physical quantity recorded as the straight traveling condition with reference to the straight traveling condition Straight running condition reproduction means to reproduce,
A hydraulic pump control device comprising: The discharge amount increasing / decreasing means individually has an electromagnetic pressure control valve for adjusting a control pressure introduced into a regulator for controlling the discharge amount of the hydraulic pump for each hydraulic pump,
The first physical quantity is a discharge pressure of each of the two hydraulic pumps or a discharge pressure of each of the left and right traveling hydraulic motors.
The second physical quantity is a control command value of the electromagnetic pressure control valve.
The hydraulic pump control device according to claim 1.