JPH07139510A - Hydraulic transmission of hydraulic working machine - Google Patents

Abstract

PURPOSE:To provide excellent metering characteristics regardless of the size of the inclination angle of a travel variable capacity hydraulic motor. CONSTITUTION:This device is equipped with a variable capacity hydraulic pump 2; a regulator 3 to control the inclination angle of the hydraulic pump 2; plural actuators including a travel variable capacity hydraulic motor 4 driven by pressure oil discharged from the hydraulic pump 2; a travel direction control valve 7 to control the flow of pressure oil that is supplied to the hydraulic motor 4 from the hydraulic pump 2; and an operation device 8 to operate this travel direction control valve 7. Also, the device has a built-in third output means that constitutes a motor supply quantity change control means to conduct control to increase by a predetermined quantity a flow quantity to be supplied to the hydraulic motor 4 when a high speed mode is outputted from a travel speed changeover switch 6 to a controller 11, that is, when the inclination angle of the hydraulic motor 4 is a specific small inclination angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system equipped with a hydraulic working machine such as a hydraulic excavator and having a traveling variable displacement hydraulic motor capable of changing the traveling speed.

[0002]

2. Description of the Related Art An open center type hydraulic drive device and a closed center type hydraulic drive device provided with an unload valve are known as conventional hydraulic drive devices having a variable displacement hydraulic motor for traveling provided in a hydraulic excavator or the like. is there. Of these, the conventional open center type hydraulic drive system is shown in FIG.
1 to 24, and a closed center type hydraulic drive system will be described with reference to FIGS.

A conventional open-center type hydraulic drive system shown in FIG. 21 is provided, for example, in a hydraulic excavator, and includes a prime mover 1, a variable displacement hydraulic pump 2 driven by the prime mover 1, and a discharge from the hydraulic pump 2. An actuator that is driven by the pressure oil that is generated, for example, a variable displacement hydraulic motor 4 for traveling that drives a traveling body (not shown), actuators such as a boom cylinder, an arm cylinder, a bucket cylinder, and a swing motor (not shown), and a center bypass passage 7a are provided. A directional control valve 7 for traveling that controls the flow of pressure oil supplied from the hydraulic pump 2 to the hydraulic motor 4 and a directional control valve (not shown) that controls the boom cylinder and the like are provided.

Also, connected to the pilot hydraulic power source 12,
An operating device 8a for generating a pilot pressure for driving the traveling directional control valve 7, a shuttle valve 10 for taking out the pilot pressure given to the traveling directional control valve 7, and a magnitude of the pilot pressure taken out by the shuttle valve 10. Pump tilt angle control device that controls the displacement of the hydraulic pump 2, that is, the tilt angle of the swash plate, that is, the regulator 3 and the motor tilt angle switching that controls the tilt angle of the hydraulic motor 4. It is arranged between the device 5, the pilot oil pressure source 12 and the motor tilt angle switching device 5, and reduces the pressure oil of the pilot oil pressure source 12 and outputs the secondary pressure as a control pressure to the motor tilt angle switching device 5. The proportional electromagnetic pressure reducing valve 9 and a traveling speed selecting means for outputting a signal for determining the traveling speed of the hydraulic motor 4, for example, one of a high speed mode and a low speed mode is manually selected. A traveling speed change-over switch 6 to, and a controller 11a for controlling the proportional solenoid pressure reducing valve 9.

The controller 11a determines which one of the high speed mode and the low speed mode is selected on the basis of the signal output from the speed change switch 6, and when it is determined that the low speed mode is selected. A drive signal for driving the proportional electromagnetic pressure reducing valve 9 is output so as to increase the tilt angle of the hydraulic motor 4, and a proportional electromagnetic signal is output so as to decrease the tilt angle of the hydraulic motor 4 when the high speed mode is determined. The output means for outputting a drive signal for driving the pressure reducing valve 9 is built in.

In the prior art thus constructed, when the operation amount of the operation lever of the operation device 8a is gradually increased, the pilot pressure applied to the drive portion of the traveling directional control valve 7 is gradually increased accordingly. The traveling direction switching valve 7 is gradually switched, and the center bypass passage 7a communicating with the tank in the neutral state is gradually closed.
On the other hand, the hydraulic pump 2 and the hydraulic motor 4 start communicating. At the same time, the pilot pressure applied to the drive portion of the traveling directional control valve 7 is taken out by the shuttle valve 10, and the pilot pressure is applied to the regulator 3, which drives the regulator 3 to tilt the hydraulic pump 2, that is, to displace it. The volume is gradually increased, whereby the flow rate discharged from the hydraulic pump 2 is gradually increased. FIG. 22 is a diagram showing the relationship between the lever operation amount of the operating device 8a and the flow rate of the hydraulic pump 2 at this time. As is clear from the characteristic line 2A1, the pump flow rate gradually increases as the lever operation amount increases. It is characteristic.

The relationship between the lever operation amount of the operating device 8a and the discharge pressure of the hydraulic pump 2 is shown by the characteristic line 2A in FIG.
As indicated by 2, the pump pressure gradually increases as the lever operation amount increases. Here, when the load pressure of the actuator, that is, the hydraulic motor 4 is the low pressure P1, the pump pressure becomes P1 when the lever operation amount is relatively small L1, and the pressure is applied to the hydraulic motor 4 as the lever operation amount becomes L1 or more. The metering characteristic that oil starts to be supplied and the supply flow rate to the hydraulic motor 4 increases relatively gently as the lever operation amount of the operating device 8a increases as shown by the characteristic line M1 in FIG. It is possible to obtain the characteristic that the operating speed of is relatively slowly increased. As shown in FIG. 23, when the load pressure of the hydraulic motor 4 is the high pressure P2, the lever operation amount L2 is larger than the above-described L1.
Then, the pump pressure becomes P2, and the hydraulic oil is supplied to the hydraulic motor 4 by the subsequent increase in the lever operation amount, and as shown by the characteristic line M2 in FIG. 24, the hydraulic motor 4 is supplied with the increase in the lever operation amount. The metering characteristic is such that the supply flow rate sharply increases, that is, the operating speed of the hydraulic motor 4 rapidly increases, which is not desirable.

As described above, when the traveling speed changeover switch 6 selects, for example, the low speed mode, the output means of the controller 11a determines the traveling mode as the low speed mode based on the signal output from the changeover switch 6. A drive signal corresponding to the low speed mode is output to the proportional electromagnetic pressure reducing valve 9, the proportional electromagnetic pressure reducing valve 9 is operated, the pressure oil of the pilot hydraulic pressure source 12 is reduced, and the secondary pressure thereof is used as the control pressure to cause the motor tilt. The motor tilt angle switching device 5 is driven by the angle switching device 5 and is controlled so that the tilt angle of the hydraulic motor 4 is increased. When the high speed mode is selected by the travel speed changeover switch 6, the output means of the controller 11a determines that the travel mode is the high speed mode, and a drive signal corresponding to this high speed mode is output to the proportional electromagnetic pressure reducing valve 9 to drive the motor. The tilt angle switching device 5 is driven so that the tilt angle of the hydraulic motor 4 is controlled to be small.

Further, the conventional closed center type hydraulic drive system shown in FIG. 25 is also provided in a hydraulic excavator, for example. The difference from the configuration shown in FIG. As shown in FIG. 26 (a), the pump pressure Pd and the actuator, that is, the hydraulic motor 4 are not provided.
An unload valve 23 that operates according to the pressure difference from the load pressure PL of the hydraulic pump 2 and allows the flow rate of the hydraulic pump 2 to escape to the tank.
A differential pressure sensor 24 that detects a differential pressure between the pump pressure Pd and the load pressure PL and outputs a differential pressure signal to the controller 11a, and a differential pressure signal that is built in the controller 11a and that is output from the differential pressure sensor 24. A proportional electromagnetic pressure reducing valve 1 for obtaining a drive signal and controlling the drive of the drive signal with the drive signal
The output means for outputting to 6 is provided. Others are equivalent to those shown in FIG. 21 described above. The unload valve 23, the differential pressure sensor 24, the output means of the controller 11a, and the proportional electromagnetic pressure reducing valve 16 described above.
Constitutes a load sensing control means for controlling the pump discharge amount so that the differential pressure between the pump pressure Pd and the load pressure PL becomes a predetermined target differential pressure.

Also in the prior art shown in FIG. 25, when the traveling directional control valve 7F is switched according to the lever operation amount of the operating device 8a and the pump pressure Pd becomes larger than the load pressure PL, the hydraulic oil of the hydraulic pump 2 becomes hydraulic. The hydraulic motor 4 is supplied to the motor 4, and the hydraulic motor 4 has an operating speed corresponding to the supply flow rate. When the differential pressure detected by the differential pressure sensor 24 is smaller than the predetermined target differential pressure, the controller 11a outputs a drive signal for increasing the pump flow rate to the proportional electromagnetic pressure reducing valve 16 in order to increase the pump pressure Pd. By driving the proportional electromagnetic pressure reducing valve 16, the regulator 3 is driven so as to make the tilt angle of the hydraulic pump 2 larger than before, and the hydraulic pump 2
From the controller 11a to the proportional electromagnetic pressure reducing valve 16 when the differential pressure detected by the differential pressure sensor 24 is larger than a predetermined target differential pressure. A drive signal for reducing the pump flow rate is output to reduce the pump flow rate, and the proportional electromagnetic pressure reducing valve 16 is driven to drive the regulator 3 so that the tilt angle of the hydraulic pump 2 becomes smaller than that before, and the hydraulic pump 2 outputs the tilt angle. The flow rate supplied to the hydraulic motor 4 is controlled to be small.

In the prior art shown in FIG. 25, as shown by the characteristic line 2B1 in FIG.
The opening area A of the unload valve 23 increases as the differential pressure between the pump pressure Pd and the load pressure PL increases.
The flow rate Q flowing from the tank to the tank increases as the pump pressure Pd increases, as indicated by the characteristic line 2B2 in FIG.

In the prior art shown in FIG. 25, as in the prior art shown in FIG. 21, the pump pressure Pd increases as the load pressure PL increases, so that the characteristic line M2 in FIG. The metering characteristic is equivalent to that, and eventually, the metering characteristic is deteriorated.

[0013]

FIG. 27 shows the relationship between the supply flow rate to the hydraulic motor 4 and the rotation speed of the hydraulic motor 4, which is common to the above-described two conventional techniques, and is shown by the characteristic line 4A1 in the low speed mode. As described above, the hydraulic motor 4 is controlled to a large tilt, and in the high speed mode, the tilt is controlled to a small tilt as shown by the characteristic line 4A2. Becomes larger and the operating speed becomes faster.

By the way, in order to obtain a predetermined torque T1 required to rotate the hydraulic motor 4 in such a conventional technique, the hydraulic motor 4 is operated in the low speed mode as shown by a characteristic line 4B1 in FIG. The tilt angle of becomes a large tilt,
Although it can be obtained at the low pressure P1, the tilt angle of the hydraulic motor 4 becomes a small tilt in the high speed mode as shown by the characteristic line 4B2, and the high pressure P2 is required. Therefore, for example, when a traveling body (not shown) provided in the hydraulic excavator climbs a slope in a high speed mode or when a large torque is required such as when turning left and right, the load pressure of the hydraulic motor 4 is illustrated in FIG. 28. Since the pressure is high P2, the relationship between the lever operation amount of the operating device 8a and the supply amount to the hydraulic motor 4 corresponds to the above-described characteristic line M2 in FIG. 24, and the metering characteristic deteriorates. Therefore, the traveling directional control valve 7
Even if a slight switching operation of (7F) was attempted, there was a risk of sudden start, it was difficult to perform fine operation, and the operator felt very tired.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to obtain good metering characteristics regardless of the tilt angle of the variable displacement hydraulic motor for traveling. It is to provide a hydraulic drive system for a hydraulic working machine.

[0016]

In order to achieve this object, the present invention provides a variable displacement hydraulic pump, a pump displacement angle control device for controlling the displacement angle of the variable displacement hydraulic pump,
Controlling a plurality of actuators including a traveling variable displacement hydraulic motor driven by pressure oil discharged from the variable displacement hydraulic pump, and a flow of pressure oil supplied from the variable displacement hydraulic pump to the traveling variable displacement hydraulic motor In a hydraulic drive system for a hydraulic working machine equipped with a traveling directional control valve and an operating device for operating the traveling directional control valve, a tilt angle of the traveling variable displacement hydraulic motor is a predetermined small tilt angle. At this time, the motor supply amount change control means for controlling the flow rate supplied to the traveling variable displacement hydraulic motor to be increased by a predetermined amount as compared with when the tilt angle is a predetermined large tilt angle is provided. There is.

[0017]

Since the present invention is configured as described above, when the traveling variable displacement hydraulic motor is in the state of large tilt in the low speed mode, for example, the motor supply amount change control means does not operate. Similar to the case of the technology, the degree of increase in the hydraulic motor supply amount relative to the increase in the operation amount of the operating device is relatively moderate, that is, good metering characteristics with a gentle slope can be obtained.

Further, when the hydraulic motor is in a state of small tilt in the high speed mode, for example, the motor supply amount change control means is activated and the tilt angle is larger than that in the case of large tilt, that is, Control is performed to increase the motor supply amount by a predetermined amount as compared with the motor supply amount in the case of the small tilt of the prior art. As a result, the discharge pressure of the variable displacement hydraulic pump becomes higher than the discharge pressure of the prior art when the hydraulic motor is tilted a little, and the starting timing of the hydraulic motor can be advanced. The degree of increase in the hydraulic motor supply amount with respect to the increase in the operation amount of is slower than in the high speed mode of the conventional technique, and good metering characteristics can be obtained. In this case, it is also possible to make the metering characteristic close to the above-described metering characteristic at the time of large tilt.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention will be described below with reference to the drawings. 1 to 4 are explanatory views showing a first embodiment corresponding to claims 1, 2, 3, 9 of the present invention, FIG. 1 is a circuit diagram showing a main configuration, and FIG. 2 is a first embodiment. Showing the characteristics of the traveling directional control valve provided in FIG. 3, FIG. 3 is a flowchart showing the processing procedure of the third output means incorporated in the controller provided in the first embodiment, and FIG. 4 is the first embodiment. It is a figure which shows the functional relationship memorize | stored in the memory | storage part contained in the 3rd output means incorporated in the controller with which it is equipped.

The first embodiment shown in FIG. 1 is the same as that shown in FIG.
It is an open center system like the conventional technology of
For example, it is a hydraulic drive device provided in a hydraulic excavator.
Also in the first embodiment, a prime mover 1 equivalent to the prior art shown in FIG. 21, a variable displacement hydraulic pump 2 driven by the prime mover 1, and an actuator driven by pressure oil discharged from the hydraulic pump 2 are also provided. For example, a traveling variable displacement hydraulic motor 4 for driving a traveling body (not shown), actuators such as a boom cylinder, an arm cylinder, a bucket cylinder, and a swing motor (not shown), and a center bypass passage 7a are provided. Traveling directional control valve 7, which controls the flow of pressure oil supplied to the
And a directional control valve (not shown) for controlling the boom cylinder and the like.

A pump tilting angle control device for controlling the displacement of the hydraulic pump 2, that is, the regulator 3
And a motor tilt angle switching device 5 that controls the tilt angle of the hydraulic motor 4, and is arranged between the pilot hydraulic power source 12 and the motor tilt angle switching device 5 to reduce the pressure oil of the pilot hydraulic power source 12. A proportional electromagnetic pressure reducing valve 9 given to the motor tilt angle switching device 5 as control pressure and a traveling speed selecting means for outputting a signal for determining the traveling speed of the hydraulic motor 4, for example, one of a high speed mode and a low speed mode is manually operated. And a traveling speed changeover switch 6 for selecting the second speed.

In particular, in the first embodiment, the pressure generating means, that is, the throttle valve 18 provided downstream of the center bypass passage 7a of the traveling direction control valve 7, and the throttle valve 1 are provided.
8 is arranged between the pressure sensor 17 that detects the downstream pressure of the center bypass passage 7a generated in FIG. 8 and outputs a signal, and the respective drive portions of the pilot hydraulic power source 12 and the directional control valve 7 for traveling. Proportional electromagnetic pressure reducing valve 15 for controlling the magnitude of pilot pressure applied to both drive parts of the direction control valve 7.
A, 15B and their proportional solenoid pressure reducing valves 15A, 15B
It is arranged between the operating device 8 which is an electric lever device for outputting a signal to drive the pilot hydraulic power source 12, and the pilot hydraulic power source 12 and the regulator 3. The pressure oil of the pilot hydraulic power source 12 is depressurized and the secondary pressure thereof is used as the control pressure. The signals output from the proportional electromagnetic pressure reducing valve 16 output to the regulator 3, the traveling speed changeover switch 6, the pressure sensor 17, and the operating device 8 are processed to drive signals to the proportional electromagnetic pressure reducing valves 9, 16, 15A, 15B. And a controller 11 for outputting

The relationship between the lever operation amount of the operating device 8 and the opening area of the traveling directional control valve 7 is shown in FIG.
As shown in Fig. 7, as the lever operation amount gradually increases from the neutral position, the opening area of the center bypass passage 7a decreases as shown by the characteristic line 7A, and as shown by the characteristic line 7B, the lever operation amount shows. As a result, the opening area of the communication passage 7b and the like from the position beyond the dead zone to the hydraulic motor 4 increases proportionally.

The above-mentioned controller 11 has first, second and
It incorporates a third output means. Of these, the first output means determines which one of the high speed mode and the low speed mode is selected based on the signal output from the travel speed changeover switch 6, and determines that the low speed mode is selected. The drive signal for driving the proportional electromagnetic pressure reducing valve 9 is output so as to increase the tilt angle of the hydraulic motor 4 when the high speed mode is activated, and the tilt angle of the hydraulic motor 4 is decreased when the high speed mode is determined. And outputs a drive signal for driving the proportional electromagnetic pressure reducing valve 9.

The second output means is the pressure sensor 17
The proportional electromagnetic pressure reducing valve that controls the regulator 3 so that the hydraulic pump 2 supplies a gradually larger flow rate as the downstream pressure decreases as the value of the signal output from the center bypass passage 7a decreases. A drive signal for driving 16 is output.

The third output means includes a storage section for storing the functional relationship shown in FIG. 4, and determines whether the signal output from the traveling speed changeover switch 6 is the high speed mode or the low speed mode. When the low speed mode is determined, the moving amount of the traveling directional control valve 7 corresponding to the lever operation amount of the operating device 8 is obtained from the relationship of the characteristic line S1 in FIG. 4, and the drive signal corresponding to the moving amount is obtained. In addition to outputting to the proportional electromagnetic pressure reducing valve 15A or 15B, when the high speed mode is determined, the moving amount of the traveling directional control valve 7 corresponding to the lever operating amount of the operating device 8 is determined from the relationship of the characteristic line S2 in FIG. , Proportional solenoid pressure reducing valve 1 for the drive signal corresponding to the movement amount
Output to 5A or 15B. Although FIG. 4 shows the relationship between the lever operation amount of the operating device 8 and the movement amount of the traveling directional control valve 7, the characteristic line S1 has, for example, a characteristic equivalent to that of the conventional technique, and increases in the lever operation amount. Therefore, the movement amount of the traveling directional control valve 7 has a characteristic of increasing relatively slowly, and the characteristic line S2 indicates that the movement amount of the traveling directional control valve 7 is larger than that of the characteristic line S1 as the lever operation amount increases. The characteristic is that it rapidly increases. That is, even if the lever operation amount is the same, when the characteristic line S2 is selected, the characteristic line S1
As compared with the case where is selected, the opening area of the communication passage 7b and the like of the directional control valve 7 illustrated in FIG. 2 is controlled to be larger, and the supply amount to the hydraulic motor 4 is increased.

The above-mentioned third output means of the controller 11 constitutes means for controlling the drive of the traveling directional control valve 7, and at the same time, when the hydraulic motor 4 is in the high speed mode, that is, the tilt angle of the hydraulic motor 4 is changed. It constitutes a motor supply amount change control means for performing control to increase the flow rate supplied to the hydraulic motor 4 by a predetermined amount determined by the characteristic line S2 at a predetermined small tilt angle.

In the first embodiment thus constructed, in the low speed mode in which the traveling speed changeover switch 6 is kept in the OFF state, the first output means of the controller 11 discriminates the low speed mode. A drive signal corresponding to the low speed mode is output from the first output means to the proportional electromagnetic pressure reducing valve 9,
The proportional electromagnetic pressure reducing valve 9 is driven according to the low speed mode, and a predetermined control pressure is output from the proportional electromagnetic pressure reducing valve 9 to the motor tilt angle switching device 5, whereby the tilt angle of the hydraulic motor 4 increases. Controlled as.

When the operating device 8 is operated in this state, the third output means of the controller 11 inputs the signal of the traveling speed changeover switch 6 as shown in step SP1 of FIG. 3, and in step SP2. The traveling speed changeover switch 6 is ON
Determine whether or not. Since it is OFF now, the procedure SP
Go to 4. In step SP4, control based on the characteristic line S1 shown in FIG. 4 stored in the storage unit is executed. That is, the movement amount of the traveling directional control valve 7 according to the lever operation amount of the operating device 8 is obtained based on the characteristic line S1, and the drive signal corresponding to the movement amount is, for example, the proportional electromagnetic pressure reducing valve 15B.
The pilot pressure of the pilot hydraulic power source 12 is reduced by the proportional electromagnetic pressure reducing valve 15B and is given to one drive portion of the traveling directional control valve 7, and the traveling directional control valve is equivalent to the above-described movement amount. 7 is switched.

By the switching operation of the traveling directional control valve 7, the center bypass passage 7a is gradually closed as shown in FIG. 2, and the pressure generated in the throttle valve 18 downstream of the center bypass passage 7a is reduced. However, the pressure is detected by the pressure sensor 17, and a detection signal is output to the controller 11. The first output means of the controller 11 outputs a drive signal such that the secondary pressure output from the proportional electromagnetic pressure-reducing valve 16 increases as the value of the signal output from the pressure sensor 17 decreases. Output to 16. As a result, the above-described gradually increasing secondary pressure is applied from the proportional electromagnetic pressure reducing valve 16 to the regulator 3, and the regulator 3 gradually increases the tilt angle of the hydraulic pump 2, whereby the gradually increasing flow rate is discharged from the hydraulic pump 2. To be done. For example, the communication passage 7b of the traveling directional control valve 7 is gradually opened as shown in FIG. 2, and the pump pressure is the load pressure of the hydraulic motor 4, that is, a relatively small pressure in the low speed mode (corresponding to the low pressure P1 described above). Hydraulic pump 2 when crossed
Is started to be supplied to the hydraulic motor 4, and the hydraulic motor 4 operates. With the operation of the hydraulic motor 4, a traveling body (not shown) is driven and traveling operation is performed.

The above operation is basically the same as the operation in the low speed mode in the prior art, and the relationship between the lever operation amount of the operation device 8 and the supply amount to the hydraulic motor 4 is the characteristic of FIG. As shown by the line M1, the degree of increase of the motor supply amount relative to the increase of the lever operation amount is relatively gradual, and good metering characteristics capable of easily performing fine operation can be obtained.

Further, in the high speed mode in which the traveling speed changeover switch 6 is turned on, the first output means of the controller 11 determines the high speed mode, and the first output means drives corresponding to the high speed mode. A signal is output to the proportional electromagnetic pressure reducing valve 9, the proportional electromagnetic pressure reducing valve 9 is driven in accordance with the high speed mode, and a predetermined control pressure is output from the proportional electromagnetic pressure reducing valve 9 to the motor tilt angle switching device 5. Thus, the tilt angle of the hydraulic motor 4 is controlled to be small.

When the operating device 8 is operated in this state, the third output means of the controller 11 determines that the traveling speed changeover switch 6 is ON in the determination of the procedure SP2 of FIG. 3 and the processing of the procedure SP3. To execute. In step SP3, control based on the characteristic line S2 shown in FIG. 4 stored in the storage unit is executed. That is, a movement amount of the traveling directional control valve 7 corresponding to the lever operation amount of the operating device 8, that is, a movement amount larger than that in the case of the characteristic line S1 is obtained based on the characteristic line S2, and the drive corresponding to the movement amount A signal is output to, for example, the proportional electromagnetic pressure reducing valve 15B, the pilot pressure of the pilot hydraulic pressure source 12 is reduced by the proportional electromagnetic pressure reducing valve 15B, and is given to one drive portion of the traveling directional control valve 7, which is relatively large as described above. The traveling directional control valve 7 is switched by an amount corresponding to the amount of movement.

By the switching operation of the traveling directional control valve 7, the hydraulic pump 2 discharges a flow rate that gradually increases as described above. At this time, since the moving amount of the traveling directional control valve 7 is larger than that in the low speed mode, a flow amount increased by a predetermined amount compared to that in the low speed mode is supplied even if the lever operation amount of the operating device 8 is the same. As a result, the pump pressure increases. When the pump pressure exceeds the load pressure of the hydraulic motor 4, that is, a relatively large pressure (corresponding to the above-described high pressure P2) in the high speed mode, the flow rate of the hydraulic pump 2 starts to be supplied to the hydraulic motor 4. 4 works. In this case, since the pump pressure has already increased in the initial stage of the operation of the hydraulic motor 4, the hydraulic motor 4 can be driven from the timing when the lever operation amount of the operating device 8 is relatively small. Therefore, the relationship between the lever operation amount of the operating device 8 and the supply amount to the hydraulic motor 4 at this time can be the characteristic line M3 shown in FIG. 24, which is similar to the characteristic line M1 of FIG. Also in this high-speed mode, the degree of increase in the motor supply amount with respect to the increase in the lever operation amount can be made relatively gentle, and good metering characteristics can be obtained.

As described above, according to the first embodiment, good metering characteristics can be obtained in both the high speed mode and the low speed mode, that is, regardless of the tilt angle of the hydraulic motor 4. . Therefore, for example, even when a traveling body (not shown) provided in the hydraulic excavator climbs a slope in a high speed mode or when a large torque is required such as when turning left and right, the characteristics of the hydraulic motor 4 in FIG. Since the characteristic line M3 that is similar to the line M1 is obtained, the fine operation is easy, sudden start does not occur, and the operator's fatigue can be reduced.

5 and 6 show the claims 1, 2, 4 of the present invention.
5 and 9 are explanatory diagrams showing a second embodiment, FIG. 5 is a circuit diagram showing a main configuration, and FIG. 6 is a storage unit included in an output means incorporated in a controller provided in the second embodiment. It is a figure which shows the functional relationship memorize | stored in.

The second embodiment shown in FIG. 5 is of the open center type, like the first embodiment shown in FIG. 1, and is, for example, a hydraulic drive system provided in a hydraulic excavator. The difference between the second embodiment and the first embodiment is that
Connected to the pilot hydraulic power source 12, the directional control valve for traveling 7
The controller 11 is provided with an operating device 8a for generating a pilot pressure for driving the controller.

Controller 1 in this second embodiment
Reference numeral 1 denotes the first output means similar to that in the first embodiment, that is, either the high speed mode or the low speed mode is selected based on the signal output from the travel speed changeover switch 6. When it is determined that the low speed mode is set, a drive signal for driving the proportional electromagnetic pressure reducing valve 9 so as to increase the tilt angle of the hydraulic motor 4 is output, and it is determined that the high speed mode is set. At this time, an output means for outputting a drive signal for driving the proportional electromagnetic pressure reducing valve 9 so as to reduce the tilt angle of the hydraulic motor 4 and a fourth output means are provided.

The fourth output means includes a storage unit for storing the functional relationship shown in FIG. 6A, and the signal output from the traveling speed changeover switch 6 is in the high speed mode or the low speed mode. If it is determined that it is in the low speed mode, the discharge amount of the hydraulic pump 2 according to the center bypass flow rate is obtained from the relationship of the characteristic line S21 of FIG. 6A, and the drive according to the pump flow rate is obtained. When a signal is output to the proportional electromagnetic pressure reducing valve 16 and it is determined that the high speed mode is set, the discharge amount of the hydraulic pump 2 is obtained from the relationship of the characteristic line S22 of FIG. The signal is output to the proportional electromagnetic pressure reducing valve 16. 6A shows the relationship between the center bypass flow rate, that is, the control pressure generated in the throttle valve 18 arranged downstream of the center bypass passage 7a and the discharge amount of the hydraulic pump 2, but the characteristic line S21 is, for example, a characteristic equivalent to that of the conventional technique, that is, the pump flow rate increases as the center bypass flow rate decreases,
The characteristic line S22 is a characteristic obtained by moving the characteristic line S21 in parallel to the upper side of the drawing. That is, when the characteristic line S22 is selected, the pump flow rate is controlled to increase even if the center line bypass flow rate is the same as when the characteristic line S21 is selected, and accordingly the hydraulic motor 4 is controlled. The supply amount of is increased.

The fourth output means built in the controller 11 constitutes means for controlling the drive of the regulator 3, and at the same time, when the hydraulic motor 4 is in the high speed mode, that is, the tilt angle of the hydraulic motor 4 is predetermined. When the tilt angle is small,
It constitutes a motor supply amount change control means for controlling to increase the flow rate supplied to the hydraulic motor 4 by a predetermined amount determined by the characteristic line S22.

In the second embodiment thus constructed,
In the low speed mode in which the traveling speed changeover switch 6 is kept OFF, the first output means of the controller 11 determines the low speed mode, and the drive signal corresponding to the low speed mode is output from the first output means by the proportional electromagnetic. The pressure is output to the pressure reducing valve 9 and is controlled so that the tilt angle of the hydraulic motor 4 is increased, as in the first embodiment described above.

When the operating device 8a is operated in this state, the fourth output means of the controller 11 discriminates the low speed mode by the signal of the traveling speed changeover switch 6, and the characteristic line of FIG. The control based on S21 is performed.
That is, the center bypass flow rate according to the control pressure generated by the throttle valve 18 detected by the pressure sensor 17 is obtained, and the pump flow rate is obtained from the characteristic line S21 of FIG. 6A, which corresponds to the pump flow rate. The drive signal is output to the proportional electromagnetic pressure reducing valve 16, the pilot pressure of the pilot hydraulic pressure source 12 is reduced by the proportional electromagnetic pressure reducing valve 16 and given to the regulator 3, and the regulator 3 uses the characteristic line S2 described above.
The tilt angle of the hydraulic pump 2 is controlled so that the pump flow rate is 1 or higher. As a result, the corresponding flow rate is supplied from the hydraulic pump 2 to the hydraulic motor 4 via the traveling directional control valve 7, the hydraulic motor 4 operates at a low speed, and the traveling body (not shown) travels.

The above operation is equivalent to that of the prior art, and the relationship between the lever operation amount of the operating device 8a and the supply flow rate to the hydraulic motor 4 is the same as that of the characteristic line M1 of FIG. Good metering characteristics can be obtained.

Further, in the high speed mode in which the traveling speed changeover switch 6 is turned on, the first output means of the controller 11 determines the high speed mode, and the drive signal corresponding to the high speed mode is proportional from the first output means. It is output to the electromagnetic pressure reducing valve 9, and accordingly, the motor tilt angle switching device 5 is activated to control the tilt angle of the hydraulic motor 4 to be small.

When the operating device 8a is operated in this state,
The fourth output means of the controller 11 discriminates the high speed mode from the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S22 of FIG. 6A is executed. That is, a pump flow rate larger than that of the characteristic line S21 is obtained based on the characteristic line S22, a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the regulator 3 is driven to tilt the hydraulic pump 2. The angle is controlled to be larger than that in the low speed mode. As a result, the supply amount to the hydraulic motor 4 is increased, and the pump pressure is increased in the initial stage of the operation of the hydraulic motor 4. Therefore, the hydraulic motor 4 is driven from the timing when the lever operation amount of the operating device 8a is relatively small. Can be made. Therefore, the operating device 8
The relationship between the lever operation amount of a and the supply amount to the hydraulic motor 4 is
A characteristic line corresponding to the characteristic line M3 in FIG. 24 described above can be used, and also in this case, good metering characteristics can be obtained.

As described above, also in the second embodiment, good metering characteristics can be obtained irrespective of the magnitude of the tilt angle of the hydraulic motor 4, and the same as in the first embodiment described above. The effect can be obtained.

In the second embodiment described above, in the storage unit included in the fourth output means incorporated in the controller 11, as shown in FIG. The characteristic line S22 translated in parallel is stored in the memory, and the control according to the characteristic line S22 is performed in the high speed mode.
Characteristic line S23 as shown in (b), that is, characteristic line S
The characteristic line S23 having a larger inclination than that of No. 21 may be stored in the above-mentioned storage unit, and control may be performed according to the characteristic line S23 of FIG. 6B in the high speed mode. Even with this configuration, the amount of motor supply in the high speed mode can be increased based on the characteristic line S23, the pump pressure can be changed relatively large, and the operation timing of the hydraulic motor 4 can be advanced, so that a good meter can be obtained. The ring characteristic can be obtained.

7 and 8 show claims 1, 2, 4 of the present invention.
FIG. 7 is an explanatory diagram showing a third embodiment corresponding to Nos. 6 and 9, FIG. 7 is a circuit diagram showing a main configuration, and FIG. 8 is a storage unit included in output means incorporated in a controller provided in the third embodiment. It is a figure which shows the functional relationship memorize | stored in.

The third embodiment shown in FIG. 7 is of the open center type, like the second embodiment shown in FIG. 5, and is, for example, a hydraulic drive system provided in a hydraulic excavator. The difference between the third embodiment and the second embodiment is that
In order to realize control for obtaining the flow rate of the hydraulic pump 2 according to the lever operation amount of the operating device 8a, the traveling directional control valve 7
A shuttle valve 10 for extracting a pilot pressure for driving the
The controller 11 is provided with a pressure sensor 20 which detects the magnitude of the pilot pressure taken out by the shuttle valve 10 and outputs it as a signal to the controller 11.
It is the structure of.

Controller 1 in this third embodiment
1 is the first output means similar to that in the second embodiment, that is, either the high speed mode or the low speed mode is selected based on the signal output from the travel speed changeover switch 6. When it is determined that the low speed mode is set, a drive signal for driving the proportional electromagnetic pressure reducing valve 9 so as to increase the tilt angle of the hydraulic motor 4 is output, and it is determined that the high speed mode is set. At this time, an output means for outputting a drive signal for driving the proportional electromagnetic pressure reducing valve 9 so as to reduce the tilt angle of the hydraulic motor 4 is provided, and a fifth output means is provided.

The fifth output means includes a storage unit for storing the functional relationship shown in FIG. 8A, and the signal output from the traveling speed changeover switch 6 is in the high speed mode or the low speed mode. If it is determined that it is in the low speed mode, the discharge amount of the hydraulic pump 2 corresponding to the lever operation amount of the operating device 8a is obtained from the relationship of the characteristic line S31 of FIG. When the drive mode is output to the proportional electromagnetic pressure reducing valve 16 and the high speed mode is determined, the discharge amount of the hydraulic pump 2 is obtained from the relationship of the characteristic line S32 of FIG. A drive signal corresponding to the above is output to the proportional electromagnetic pressure reducing valve 16. In addition, in FIG.
Shows the relationship between the lever operation amount of the operating device 8a and the discharge amount of the hydraulic pump 2, the characteristic line S31 is, for example, a characteristic equivalent to that of the conventional technique, and the pump flow rate is proportional to the increase of the lever operation amount. It is a characteristic that increases, and the characteristic line S3
2 has a characteristic that the inclination is larger than that of the characteristic line S31. That is, when the characteristic line S32 is selected, the pump flow rate is controlled to increase even if the lever operation amount is the same as when the characteristic line S31 is selected, and accordingly, the hydraulic motor 4 is controlled. The supply amount of is increased.

The fifth output means incorporated in the controller 11 constitutes means for controlling the drive of the regulator 3 and, at the same time, when the hydraulic motor 4 is in the high speed mode, that is, the tilt angle of the hydraulic motor 4 is predetermined. When the tilt angle is small,
It constitutes a motor supply amount change control means for performing control to increase the flow rate supplied to the hydraulic motor 4 by a predetermined amount determined by the characteristic line S32.

In the third embodiment thus constructed, in the low speed mode in which the traveling speed changeover switch 6 is kept off, the first output means of the controller 11 discriminates the low speed mode. A drive signal corresponding to the low speed mode is output from the output means No. 1 to the proportional electromagnetic pressure reducing valve 9, and the tilt angle of the hydraulic motor 4 is controlled to be large, as in the second embodiment.

When the operating device 8a is operated in this state, the fifth output means of the controller 11 discriminates the low speed mode from the signal of the traveling speed changeover switch 6, and the characteristic line of FIG. Control based on S31 is implemented.
That is, the lever operation amount according to the magnitude of the pilot pressure applied to the traveling directional control valve 7 detected by the pressure sensor 20 is obtained, and the pump flow rate is obtained from the characteristic line S31 of FIG. A drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, the pilot pressure of the pilot hydraulic pressure source 12 is reduced by the proportional electromagnetic pressure reducing valve 16 and given to the regulator 3, and the regulator 3 uses the characteristic line S31 described above. The tilt angle of the hydraulic pump 2 is controlled so that the pump flow rate becomes higher. As a result, the corresponding flow rate is supplied from the hydraulic pump 2 to the hydraulic motor 4 via the traveling directional control valve 7, the hydraulic motor 4 operates at a low speed, and the traveling body (not shown) travels.

The above operation is the same as in the prior art, and the relationship between the lever operation amount of the operating device 8a and the supply flow rate to the hydraulic motor 4 becomes the same as the characteristic line M1 in FIG. Good metering characteristics can be obtained.

Further, in the high speed mode in which the traveling speed changeover switch 6 is turned on, the first output means of the controller 11 determines the high speed mode, and the drive signal corresponding to the high speed mode is proportional from the first output means. It is output to the electromagnetic pressure reducing valve 9, and accordingly, the motor tilt angle switching device 5 is activated to control the tilt angle of the hydraulic motor 4 to be small.

When the operating device 8a is operated in this state,
The fourth output means of the controller 11 discriminates the high speed mode by the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S32 of FIG. 8A is executed. That is, a pump flow rate larger than that of the characteristic line S31 is obtained based on the characteristic line S32, a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the regulator 3 is driven to tilt the hydraulic pump 2. The angle is controlled to be larger than that in the low speed mode. As a result, the supply amount to the hydraulic motor 4 is increased, and the pump pressure is increased in the initial stage of the operation of the hydraulic motor 4. Therefore, the hydraulic motor 4 is driven from the timing when the lever operation amount of the operating device 8a is relatively small. Can be made. Therefore, the operating device 8
The relationship between the lever operation amount of a and the supply amount to the hydraulic motor 4 is
A characteristic line similar to the characteristic line M3 of FIG. 24 described above can be used, and in this case also, a good metering characteristic can be obtained.

As described above, also in the third embodiment, good metering characteristics can be obtained regardless of the magnitude of the tilt angle of the hydraulic motor 4, and the same as in the second embodiment described above. The effect can be obtained.

In the third embodiment described above, the storage unit included in the fifth output means incorporated in the controller 11 has an inclination more than the characteristic line S31 as shown in FIG. 8 (a). The enlarged characteristic line S32 is stored, and the control according to the characteristic line S32 is performed in the high speed mode. However, instead of such a characteristic line S32, a characteristic line S33 as shown in FIG. , That is, the characteristic line S3
It is also possible to store the characteristic line S33 obtained by moving 1 in parallel upwards as it is in the above-mentioned storage unit, and to perform control according to the characteristic line S33 of FIG. 8B in the high speed mode. Even with this configuration, it is possible to increase the motor supply amount in the high speed mode based on the characteristic line S33.
By changing the pump pressure relatively greatly, the operation timing of the hydraulic motor 4 can be advanced, and good metering characteristics can be obtained.

9 and 10 are views showing the essential parts of the fourth and fifth embodiments corresponding to claims 1, 2, 4, and 7 of the present invention, respectively.

The circuit configuration of the fourth embodiment, the main part of which is shown in FIG. 9, is equivalent to that of FIG. 5, for example. Therefore, FIG.
A description will be given below using the reference numerals shown in.

In the fourth embodiment, the controller 11
Is a first output means similar to the second embodiment described in FIG.
That is, based on the signal output from the traveling speed changeover switch 6, it is determined which one of the high speed mode and the low speed mode is selected, and when it is determined that the low speed mode is selected, the hydraulic motor 4 is driven. The output means for outputting the drive signal for driving the proportional solenoid valve 9 so as to reduce the tilt angle is provided, and the sixth output means is provided.

The sixth output means includes a storage unit for storing the functional relationship shown in FIG. 9, and determines whether the signal output from the traveling speed changeover switch 6 is the high speed mode or the low speed mode. When the low speed mode is determined, the discharge amount of the hydraulic pump 2 corresponding to the center bypass flow rate is obtained from the relationship of the characteristic line S41 in FIG. 9, and the drive signal corresponding to the pump flow rate is sent to the proportional solenoid pressure reducing valve 16. When the output is made and it is determined that the high speed mode is set, the characteristic line S42 in FIG.
The discharge amount of the hydraulic pump 2 is obtained from the relationship of, and a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16.
9 shows the relationship between the center bypass flow rate, that is, the control pressure generated by the throttle valve 18 arranged downstream of the center bypass passage 7a and the discharge amount of the hydraulic pump 2. The characteristic line S41 is, for example, conventional. This characteristic is equivalent to that of the technology, and the pump flow rate increases as the center bypass flow rate decreases. The characteristic line S42 indicates that the center bypass flow rate is at a minimum, that is, when the traveling directional control valve 7 is in a neutral state and when traveling. The characteristics are such that the pump flow rate is increased in advance as compared with the characteristic line 41 at the initial stage of switching the directional control valve 7 and in the standby state when the flow rate is not yet supplied to the hydraulic motor 4. That is, when the characteristic line S42 is selected, control is performed so that the pump flow rate increases even when the center bypass flow rate is the same as when the characteristic line S41 is selected.

The sixth output means incorporated in the controller 11 causes the tilting of the hydraulic pump 2 when the hydraulic motor 4 is in the high speed mode, that is, when the tilting angle of the hydraulic motor 4 is a predetermined small tilting angle. The means for driving the regulator 3 is configured so that the angle becomes a predetermined tilt angle larger than a predetermined minimum tilt angle, and at the same time, the flow rate supplied to the hydraulic motor 4 is increased by a predetermined amount determined by the characteristic line S42. The motor supply amount change control means for performing the control is configured.

In the fourth embodiment thus constructed,
In the low speed mode in which the traveling speed changeover switch 6 is kept OFF, the first output means of the controller 11 determines the low speed mode, and the drive signal corresponding to the low speed mode is output from the first output means by the proportional electromagnetic. It is output to the pressure reducing valve 9 and is controlled so that the tilt angle of the hydraulic motor 4 is increased, as in the second embodiment described above.

When the operating device 8a is operated in this state, the sixth output means of the controller 11 discriminates the low speed mode by the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S41 of FIG. Is carried out. That is, the center bypass flow rate corresponding to the control pressure generated by the throttle valve 18 detected by the pressure sensor 17 is obtained,
The pump flow rate is obtained from the characteristic line S41 of 1., a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the pilot pressure of the pilot hydraulic pressure source 12 is reduced by the proportional electromagnetic pressure reducing valve 16 to the regulator 3. Given,
The regulator 3 controls the tilt angle of the hydraulic pump 2 so that the pump flow rate on the characteristic line S41 described above is achieved. As a result, the corresponding flow rate is supplied from the hydraulic pump 2 to the hydraulic motor 4 via the traveling directional control valve 7, the hydraulic motor 4 operates at a low speed, and the traveling body (not shown) travels.

The above operation is the same as in the prior art, and the relationship between the lever operation amount of the operating device 8a and the pump pressure is shown in FIG.
(A) of the characteristic line 41a, and the relationship between the lever operation amount and the supply amount to the hydraulic motor 4 is shown in FIG.
As shown by the characteristic line M11 in (b), good metering characteristics can be obtained.

In the high speed mode in which the traveling speed changeover switch 6 is turned on, the first output means of the controller 11 determines the high speed mode, and the drive signal corresponding to the high speed mode is proportional from the first output means. It is output to the electromagnetic pressure reducing valve 9, and accordingly, the motor tilt angle switching device 5 is activated to control the tilt angle of the hydraulic motor 4 to be small.

When the operating device 8a is operated in this state,
The sixth output means of the controller 11 discriminates the high speed mode from the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S42 of FIG. 9 is executed. That is, a larger standby flow rate than that on the characteristic line S41 is obtained based on the characteristic line S42, a drive signal corresponding to the standby flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the regulator 3 is driven to drive the hydraulic pump during standby. The tilt angle of 2 is controlled to be larger than that in the low speed mode. As a result, the supply amount to the hydraulic motor 4 is increased,
As shown by the characteristic line S42a in FIG. 11A, the pump pressure increases at the initial stage of the operation of the hydraulic motor 4, so that as shown by the characteristic line M31 in FIG. The hydraulic motor 4 can be driven from the time when the lever operation amount is relatively small, and also in this case, good metering characteristics can be obtained. Note that the characteristic line M21 of FIG. 11B is a characteristic line when the load pressure of the hydraulic motor 4 is large in the high speed mode and small tilt in the conventional technique illustrated for comparison, and is as described above. In addition, in the prior art, the metering characteristic is deteriorated because the characteristic line M21 is steep.

As described above, also in the fourth embodiment, good metering characteristics can be obtained regardless of the tilt angle of the hydraulic motor 4.

The circuit configuration of the fifth embodiment, the main part of which is shown in FIG. 10, is equivalent to that of FIG. 7, for example. Therefore, the following description will be given using the reference numerals shown in FIG. 7.

In this fifth embodiment, the controller 11
Is a first output means similar to the third embodiment described in FIG.
That is, based on the signal output from the traveling speed changeover switch 6, it is determined which one of the high speed mode and the low speed mode is selected, and when it is determined that the low speed mode is selected, the hydraulic motor 4 is driven. An output means for outputting a drive signal for driving the proportional solenoid valve 9 so as to reduce the tilt angle is provided, and a seventh output means is provided.

The seventh output means includes a storage section for storing the functional relationship shown in FIG. 10, and determines whether the signal output from the traveling speed changeover switch 6 is the high speed mode or the low speed mode. When it is determined that the operation mode is the low speed mode, the operation device 8a is determined from the relationship of the characteristic line S51 of FIG.
The discharge amount of the hydraulic pump 2 according to the lever operation amount of
A drive signal corresponding to the pump flow rate is sent to the proportional electromagnetic pressure reducing valve 16
When it is determined that the high speed mode is output,
The discharge amount of the hydraulic pump 2 is obtained from the relationship of the characteristic line S52 of 1 above, and a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16. Although FIG. 10 shows the relationship between the operation amount of the operation lever of the operation device 8a and the discharge amount of the hydraulic pump 2, the characteristic line S51 has, for example, a characteristic equivalent to that of the conventional technique, and increases the lever operation amount. Therefore, the pump flow rate is increased, and the characteristic line S52 indicates that when the lever operation amount is included in the dead zone region, that is, when the traveling directional control valve 7 is in the neutral state and when the traveling directional control valve 7 is initially switched. In addition, the pump flow rate is set to be larger than that of the characteristic line 51 in the standby state when the flow rate is not yet supplied to the hydraulic motor 4. That is, this characteristic line S
When 52 is selected, control is performed so that the pump flow rate increases even when the center bypass flow rate is the same as when the characteristic line S51 is selected.

The seventh output means incorporated in the controller 11 causes the hydraulic pump 2 to tilt when the hydraulic motor 4 is in the high speed mode, that is, when the tilt angle of the hydraulic motor 4 is a predetermined small tilt angle. The means for driving the regulator 3 is configured so that the angle becomes a predetermined tilt angle larger than a predetermined minimum tilt angle, and at the same time, the flow rate supplied to the hydraulic motor 4 is increased by a predetermined amount determined by the characteristic line S52. The motor supply amount change control means for performing the control is configured.

In the fifth embodiment thus constructed,
In the low speed mode in which the traveling speed changeover switch 6 is kept OFF, the first output means of the controller 11 determines the low speed mode, and the drive signal corresponding to the low speed mode is output from the first output means by the proportional electromagnetic. The pressure is output to the pressure reducing valve 9 and is controlled so that the tilt angle of the hydraulic motor 4 is increased, as in the third embodiment.

When the operating device 8a is operated in this state, the seventh output means of the controller 11 discriminates the low speed mode by the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S51 of FIG. Is carried out. That is, the operating device 8 is generated by the signal detected by the pressure sensor 20.
The lever operation amount of a is obtained, the pump flow rate is obtained from the characteristic line S51 of FIG. 10, a drive signal corresponding to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the pilot pressure of the pilot hydraulic pressure source 12 is proportional to this. The pressure is reduced by the electromagnetic pressure reducing valve 16 and is given to the regulator 3, and the regulator 3 controls the tilt angle of the hydraulic pump 2 so that the pump flow rate on the characteristic line S51 is obtained. As a result, the corresponding flow rate is supplied from the hydraulic pump 2 to the hydraulic motor 4 via the traveling directional control valve 7, the hydraulic motor 4 operates at a low speed, and the traveling body (not shown) travels.

The above operation is the same as that of the prior art, and the relationship between the lever operation amount of the operating device 8a and the pump pressure is the same as the characteristic line 41a of FIG. The relationship with the supply amount to the motor 4 is equivalent to, for example, the characteristic line M11 in FIG. 11B, and good metering characteristics can be obtained.

Further, in the high speed mode in which the traveling speed changeover switch 6 is turned on, the first output means of the controller 11 determines the high speed mode, and the drive signal corresponding to the high speed mode is proportional from the first output means. It is output to the electromagnetic pressure reducing valve 9, and accordingly, the motor tilt angle switching device 5 is activated to control the tilt angle of the hydraulic motor 4 to be small.

When the operating device 8a is operated in this state,
The seventh output means of the controller 11 discriminates the high speed mode from the signal of the traveling speed changeover switch 6, and the control based on the characteristic line S52 of FIG. 10 is executed. That is, a larger standby flow rate than that in the characteristic line S51 is obtained based on the characteristic line S52, a drive signal corresponding to the standby flow rate is output to the proportional electromagnetic pressure reducing valve 16, and the regulator 3 is driven to drive the hydraulic pump during standby. The tilt angle of 2 is controlled to be larger than that in the low speed mode. As a result, the supply amount to the hydraulic motor 4 is increased, and the pump pressure is increased in the initial stage of the operation of the hydraulic motor 4 as in the characteristic line S42a of FIG. Similar to the characteristic line M31 of (b), the hydraulic motor 4 can be driven from the timing when the lever operation amount of the operating device 8a is relatively small, and also in this case, good metering characteristics can be obtained.

As described above, also in the fifth embodiment, good metering characteristics can be obtained regardless of the tilt angle of the hydraulic motor 4.

FIG. 12 shows claims 1, 2, 4, 8 of the present invention.
It is a circuit diagram which shows the main structures of the 6th Example corresponding to 9. The sixth embodiment shown in FIG. 12 is similar to that shown in FIG.
As in the prior art, it is of a closed center type and is, for example, a hydraulic drive device provided in a hydraulic excavator. The sixth embodiment shown in FIG. 12 is the controller 1
The configuration is the same as that of the conventional technique shown in FIG.

That is, FIG. 12 showing the sixth embodiment.
25, the traveling directional control valve 7F does not have a center bypass passage as in the prior art shown in FIG. 25, and it depends on the differential pressure between the pump pressure Pd and the load pressure PL of the hydraulic motor 4. And a differential pressure sensor 24 that detects the differential pressure between the pump pressure Pd and the load pressure PL and outputs a differential pressure signal. I have it. Further, the controller 11 uses the same first output means as in the above-mentioned embodiments,
That is, based on the signal output from the traveling speed changeover switch 6, it is determined which one of the high speed mode and the low speed mode is selected, and when it is determined that the low speed mode is selected, the hydraulic motor 4 is driven. A drive signal for driving the proportional electromagnetic pressure reducing valve 9 is output so as to increase the tilt angle, and the proportional electromagnetic pressure reducing valve 9 is controlled so as to reduce the tilt angle of the hydraulic motor 4 when the high speed mode is determined. An eighth output unit is provided as well as an output unit that outputs a drive signal for driving.

The eighth output means includes a storage unit for storing a predetermined target differential pressure equivalent to that in the prior art and a corrected target differential pressure larger than the predetermined target differential pressure, and in the low speed mode. The deviation between the differential pressure signal output from the differential pressure sensor 24 and a predetermined target differential pressure is obtained, and a drive signal corresponding to the deviation is output to the proportional electromagnetic pressure reducing valve 16 that controls the drive of the regulator 3, and in the high speed mode. A deviation between the differential pressure signal output from the differential pressure sensor 24 and the correction target differential pressure is obtained, and a drive signal corresponding to the deviation is output to the proportional electromagnetic pressure reducing valve 16 that controls the drive of the regulator 3.

The unload valve 23 and the differential pressure sensor 2 described above.
4 and the eighth output means of the controller 11 constitute load sensing control means for controlling the pump discharge amount so that the pressure difference between the pump pressure Pd and the load pressure PL becomes a predetermined pressure difference. In addition, the eighth built-in controller 11
The output means of the above constitutes a means for controlling the drive of the regulator 3, and at the same time when the traveling motor 4 is in the high speed mode,
That is, when the tilt angle of the hydraulic motor 4 is a predetermined small tilt angle, the motor supply amount control means is configured to perform control to increase the flow rate supplied to the hydraulic motor 4 by a predetermined amount according to the corrected target differential pressure. is doing.

In the sixth embodiment thus constructed, when the low speed mode is selected by the traveling speed changeover switch 6, the first output means of the controller 11 discriminates the low speed mode and the low speed mode is set. A corresponding signal is output to the proportional electromagnetic pressure reducing valve 9, the motor tilt angle switching device 5 is driven to control the tilt angle of the hydraulic motor 4 to a large tilt angle, and the eighth output means of the controller 11 is also provided. The control is performed based on the predetermined target differential pressure. That is, the deviation between the predetermined target differential pressure and the differential pressure detected by the differential pressure sensor 24 is determined, and the drive signal corresponding to this deviation is proportional to the proportional electromagnetic pressure reducing valve 1.
6, the regulator 3 is controlled in the same manner as in the prior art shown in FIG. 25, and the pump discharge amount is controlled so that the above-mentioned deviation becomes zero. The control at this time is basically the same as that of the conventional technique shown in FIG. 25, and therefore, a good metering characteristic can be secured as in the conventional technique.

When the high speed mode is selected by the traveling speed changeover switch 6, the first output means of the controller 11 determines the high speed mode and outputs a signal corresponding to the high speed mode to the proportional solenoid pressure reducing valve 9. The motor tilt angle switching device 5 is driven to control the tilt angle of the hydraulic motor to a small tilt angle, and the controller 11 responds to the signal indicating the high speed mode output from the traveling speed changeover switch 6.
The eighth output means performs the control based on the corrected target differential pressure that is larger than the predetermined target differential pressure. That is, the deviation between the corrected target differential pressure and the differential pressure detected by the differential pressure sensor 24 is obtained, a drive signal corresponding to this deviation is output to the proportional electromagnetic pressure reducing valve 16, and the regulator 3 is controlled accordingly. The pump discharge amount is controlled so as to make the above deviation zero. In this case, since the differential pressure is the pump pressure Pd-the load pressure PL, when the control is changed to the control by the corrected target differential pressure larger than the predetermined target differential pressure, the corrected target differential pressure and the differential pressure sensor 24.
In order to make the deviation from the differential pressure detected in step 0 be zero, it is necessary to increase the pump discharge amount so that the pump pressure Pd becomes larger than that during control with a predetermined target differential pressure. Is to increase the tilt angle of the hydraulic pump 2 and increase the pump discharge amount, as compared with the case of control with a predetermined target differential pressure in the low speed mode. Therefore, similarly to each of the above-described embodiments, since the pump pressure increases in the initial stage of the operation of the hydraulic motor 4, the hydraulic motor 4 can be driven from the timing when the lever operation amount of the operating device 8a is relatively small. In this case, good metering characteristics can be obtained.

As described above, also in the sixth embodiment, good metering characteristics can be obtained regardless of the tilt angle of the hydraulic motor 4.

FIG. 13 shows claims 1, 2, 4, 8 of the present invention.
It is a circuit diagram which shows the main structures of the 7th Example corresponding to 9 and 10. In addition to the configuration of the sixth embodiment shown in FIG. 12, the seventh embodiment has a pressure sensor 31 that detects the pump pressure Pd and a tilt sensor 32 that detects the tilt angle of the hydraulic pump 2. And a controller 11
And a ninth portion including a storage unit for storing the tilt area shown in FIG.
Output means. The tilting region shown in FIG. 14 includes the hydraulic motor small tilting region E1 for keeping the hydraulic motor 4 at a small tilting angle when the pump tilting angle is large and the pump pressure is low, and the hydraulic motor 4 for other times. The hydraulic motor has a large tilt area E2 that maintains a large tilt angle.

These pressure sensor 31 and tilt sensor 3
2 and the ninth output means of the controller 11 constitute a traveling speed automatic selection means for automatically switching the tilt angle of the hydraulic motor 4 in accordance with the tilt angle of the hydraulic pump 2 and the pump pressure. .

In the seventh embodiment thus constructed, when the tilt angle of the hydraulic motor 4 is controlled, for example, the signal of the ninth output means constituting the above-mentioned running speed automatic selection means is changed to
If it is determined in advance that the signal of the traveling speed changeover switch 6 by manual operation is given priority, for example, a low speed mode is selected by the traveling speed changeover switch 6 and the hydraulic motor 4 is being driven with a large tilt. When the tilt sensor 32 detects a large pump tilt angle and the pressure sensor 31 detects a small pump pressure, the ninth output means of the controller 11 determines that the state is the small tilt region E1 in FIG. , And outputs the signal indicating the high speed mode to the eighth output means described in the sixth embodiment shown in FIG. As described above, the eighth output means of the controller 11 performs the control based on the corrected target differential pressure that is larger than the predetermined target differential pressure, as compared with the control at the predetermined target differential pressure that is in the low speed mode. The tilt angle of the hydraulic pump 2 is increased and the pump discharge amount is increased.

Conversely, for example, the traveling speed changeover switch 6
When the high speed mode is selected by, the small displacement angle of the pump is detected by the displacement sensor 32 while the hydraulic motor 4 is being driven by small displacement, or the large pressure of the pump is detected by the pressure sensor 31. If so, the ninth output means of the controller 11 determines that the state is in the large tilt region E2 of FIG. 14, and outputs the signal indicating the low speed mode to the eighth output means described in the sixth embodiment shown in FIG. Output to. At this time, the eighth output means of the controller 11 performs control based on the predetermined target differential pressure as described above, and holds the tilt angle of the hydraulic pump 2 at the same level as in the conventional technique.

In the seventh embodiment constructed as described above, the pump pressure becomes high when climbing a slope in the high speed mode, for example, so that the ninth output means of the controller 11 causes the large tilt region E2. Is determined and the tilt angle of the hydraulic motor 4 is controlled so as to make a large tilt, so that the metering characteristics are not deteriorated due to the torque in the high speed mode as in the above-described conventional technique, It is possible to make the metering characteristics in the high-speed mode have a relatively gentle slope close to the metering characteristics in the low-speed mode. Therefore, good metering characteristics can be obtained in both the high-speed mode and the low-speed mode. Can be obtained.

FIG. 15 shows claims 1, 2, 4, 5 of the present invention.
It is a circuit diagram which shows the main structures of the 8th Example corresponding to 9 and 11. In addition to the configuration of the second embodiment shown in FIG. 5 described above, the eighth embodiment is provided with a detection switch 6 that responds to the spool of the traveling directional control valve 7, and the controller 1
The tenth output for executing the motor supply amount change control in the fourth output means of the signal of the traveling speed changeover switch 6 only when the detection switch 6 detects that the traveling directional control valve 7 is operated. It is configured to include means.

That is, the controller 11 uses the first output means similar to that of the second embodiment shown in FIG. 5 described above, that is, the high speed mode and the low speed mode based on the signal output from the traveling speed changeover switch 6. It is determined which one of the running modes is selected, and when it is determined that the low speed mode is selected, a drive signal for driving the proportional electromagnetic pressure reducing valve 9 is output so as to increase the tilt angle of the hydraulic motor 4. In addition, when it is determined that the high speed mode is set, the hydraulic motor 4
Output means for outputting a drive signal for driving the proportional electromagnetic pressure reducing valve 9 so as to reduce the tilt angle of the first and fourth output means, that is, a storage section for storing the functional relationship shown in FIG. 6A, it is determined whether the signal output from the traveling speed changeover switch 6 is the high speed mode or the low speed mode. When the low speed mode is determined, the signal shown in FIG.
The discharge amount of the hydraulic pump 2 according to the center bypass flow rate is obtained from the relationship of the characteristic line S21 of 1., and a drive signal according to the pump flow rate is output to the proportional electromagnetic pressure reducing valve 16, and when it is determined that the high speed mode is set, The discharge amount of the hydraulic pump 2 is obtained from the relationship of the characteristic line S22 of FIG. 6A, and an output means for outputting a drive signal corresponding to the pump flow rate to the proportional electromagnetic pressure reducing valve 16 and the tenth output means described above. Is equipped with.

The tenth output means of the controller 11 described above supplies the motor supply by the motor supply amount change control means, that is, the fourth control means of the controller 11 only when the traveling directional control valve 7 is detected by the detection switch 6. It constitutes a means for executing the quantity change control. Other configurations are the same as those of the second embodiment shown in FIG. 5 described above.

In the eighth embodiment thus constructed, when the detection switch 6 detects that the traveling directional control valve 7 has been operated, the tenth output means of the controller 11 causes the traveling speed changeover switch to operate. The motor supply amount changing control of the fourth output means is executed based on the signal of No. 6, and thereby the same control as that described in the second embodiment is performed.

When the traveling directional control valve 7 is not operated, the motor supply amount changing control in the fourth output means is not executed, and the drive signal equivalent to that in the prior art, that is, in the low speed mode is output from the fourth output means. Characteristic line 2 of FIG. 6 (a)
The drive signal obtained from the relationship of 1 is output to the proportional electromagnetic pressure reducing valve 16.

In the eighth embodiment thus constructed, the pump discharge amount can be specially increased only during the drive control of the hydraulic motor 4, and the other pumps (not shown) other than the hydraulic motor 4 can be operated by the above-mentioned pump. It is possible to prevent the influence of the increase in the discharge amount.

In the eighth embodiment, the detection switch 6 which responds to the spool of the traveling direction control valve 7 is provided as the detecting means for detecting whether or not the traveling direction control valve 7 has been operated. Instead of the detection switch 6, a switch that responds to the operation lever of the operation device 8 or a pressure switch that detects the control pressure applied to the drive unit of the traveling directional control valve 7 may be provided.

Further, in each of the above-described embodiments, the hydraulic motor 4 is driven in the high speed mode, that is, the predetermined small tilt, by the corresponding output means of the controller 11 in response to the signal output from the travel speed selection means such as the travel speed changeover switch 6. Although it is configured to determine whether the tilt angle is in the low speed mode or the predetermined large tilt angle, the present invention is not limited to this. For example, a tilt angle sensor that directly detects the tilt angle of the hydraulic motor 4 is provided, The motor supply amount change control may be appropriately performed according to the signal from the tilt angle sensor.

Further, in each of the above embodiments, the traveling speed changeover switch 6 is configured to be switched between the high speed mode and the low speed mode, ie, the second speed. However, the high speed mode, the medium speed mode, the low speed mode, the third speed, or the fourth speed. It may be configured to switch to the above.

For example, FIG. 16 shows a traveling speed switching switch 6
Controller 11 when configured to switch to 3rd speed
A flow chart showing the processing procedure of the output means included in
FIG. 17 is the same as FIG. 6 in the second embodiment shown in FIG.
It is a figure which shows the characteristic of 3-speed corresponding to the characteristic of (a). A description will be given of a case where these three speed control is applied to the second embodiment shown in FIG.
In the fourth output means, instead of the relationship of FIG. 6A, the relationship of FIG. 17, that is, between the characteristic line S21 of the low speed mode and the characteristic line S22 of the high speed mode, the characteristic line S21 of the low speed mode is provided. Curve S2 of the medium speed mode in which the
4 includes a storage unit having 4. With the above-described configuration, the signal of the traveling speed changeover switch 6 is input to the fourth output means of the controller 11 as shown in step SP11 of FIG. 16, and the traveling speed changeover switch 6 is determined by the determination shown in step SP12. When the output signal is in the low speed mode, the relationship of the characteristic line S21 of FIG. 17 is selected as shown in step SP13, and when it is in the medium speed mode, the relationship of the characteristic line S24 of FIG. 17 is selected as shown in step SP14. Is selected and the high speed mode is selected, as shown in step SP15, FIG.
The relationship of the characteristic line S22 of is selected.

The control by the characteristic line S21 in the low speed mode and the control by the characteristic line S22 in the high speed mode are the same as described above, but the control by the characteristic line S24 in the medium speed mode is comparatively performed in the low speed mode equivalent to the prior art. The tilt angle of the small hydraulic pump 2 and the large hydraulic pump 2 in the high speed mode described above
Based on the relationship of the characteristic line S24, the proportional electromagnetic pressure reducing valve 16 outputs a drive signal having a tilt angle positioned between those tilt angles.
Is output to. With such a configuration, even in the medium speed mode, an increased pump flow rate can be supplied to the hydraulic motor 4 although it is smaller than that in the high speed mode, and the pump pressure increases in the initial stage of the operation of the hydraulic motor 4. Therefore, the metering characteristic in the low speed mode, that is, the metering characteristic approximate to the good metering characteristic in the low speed mode in which the degree of increase in the motor supply amount relative to the increase in the lever operation amount of the operating device 8a is relatively gradual is obtained. be able to.

When the third speed control is applied to the second embodiment shown in FIG. 5, the relationship shown in FIG.
You may implement control based on the relationship shown in FIG. This Figure 1
Reference numeral 8 corresponds to the relationship of FIG. 6 (b) described above, and the characteristic line S21 of the low speed mode and the characteristic line S of the high speed mode are shown.
23, a characteristic line S25 for the medium speed mode having a larger inclination than the characteristic line S21 for the low speed mode is provided. Even with such a configuration, it is possible to realize an increase in the motor supply amount in the medium speed mode, which is less than that in the high speed mode, based on the characteristic line S25, and it is possible to obtain good metering characteristics in the low speed mode as in the high speed mode. It is possible to obtain a metering characteristic close to.

19 and 20 are diagrams showing the characteristics of the third speed corresponding to the characteristics of FIGS. 8A and 8B in the third embodiment shown in FIG. When the third speed control is applied to the third embodiment shown in FIG. 7, as shown in FIG. 19, a low speed mode characteristic line S31 and a high speed mode characteristic line S are obtained.
32, a characteristic line S34 of the medium speed mode having a larger inclination than the characteristic line S31 of the low speed mode is provided, or as shown in FIG. 20, the characteristic line S31 of the low speed mode is used.
The characteristic line S35 of the medium speed mode, which is obtained by moving the characteristic line S31 of the low speed mode upward in parallel, may be used between the characteristic curve S33 of the high speed mode and the characteristic line S33 of the high speed mode. In the third embodiment shown in FIG. 7, the relationship shown in FIG. 19 and the relationship shown in FIG. 20 are stored in advance in the storage unit included in the fifth output means of the controller 11, so that based on the characteristic line S34, Alternatively, based on the characteristic line S35, it is possible to realize an increase in the motor supply amount in the medium speed mode, which is smaller than that in the high speed mode, and is similar to the good metering characteristic in the low speed mode as in the high speed mode. Can be obtained.

[0106]

Since the present invention is configured as described above, good metering characteristics can be obtained regardless of the magnitude of the tilt angle of the traveling variable displacement hydraulic motor, and therefore, in the high speed mode or the like. Even if it exists, excellent fine operability can be obtained as compared with the conventional technique, a sudden start, etc. can be reliably prevented, and a feeling of fatigue given to the operator can be reduced.

[Brief description of drawings]

1 is a first diagram corresponding to claims 1, 2, 3, 9 of the present invention;
3 is a circuit diagram showing the main configuration of the embodiment of FIG.

FIG. 2 is a diagram showing characteristics of a traveling directional control valve provided in the first embodiment.

FIG. 3 is a flowchart showing a processing procedure of an output means incorporated in a controller provided in the first embodiment.

FIG. 4 is a diagram showing a functional relationship stored in a storage unit included in an output unit included in the first embodiment.

FIG. 5 is a circuit diagram showing a main configuration of a second embodiment corresponding to claims 1, 2, 4, 5, 9 of the present invention.

FIG. 6 is a diagram showing a functional relationship stored in a storage unit included in output means incorporated in a controller included in the second embodiment.

FIG. 7 is a circuit diagram showing a main configuration of a third embodiment corresponding to claims 1, 2, 4, 6, 9 of the present invention.

FIG. 8 is a diagram showing a functional relationship stored in a storage unit included in output means incorporated in a controller included in the third embodiment.

FIG. 9 is a fourth view corresponding to claims 1, 2, 4, and 7 of the present invention.
It is a figure which shows the principal part of the Example of.

FIG. 10 is a diagram showing a main part of a fifth embodiment corresponding to claims 1, 2, 4, and 7 of the present invention.

FIG. 11 is a diagram showing a relation between a lever operation amount and a pump pressure obtained in a fourth embodiment, and a diagram showing a relation between a lever operation amount and a flow rate to a motor.

FIG. 12 is a circuit diagram showing a main configuration of a sixth embodiment corresponding to claims 1, 2, 4, 8, and 9 of the present invention.

FIG. 13 is a circuit diagram showing a main configuration of a seventh embodiment corresponding to claims 1, 2, 4, 8, 9, and 10 of the present invention.

FIG. 14 is a diagram showing a tilt area stored in a storage unit included in an output means incorporated in a controller provided in a seventh embodiment.

FIG. 15 is a circuit diagram showing a main configuration of an eighth embodiment corresponding to claims 1, 2, 4, 5, 9, and 11 of the present invention.

FIG. 16 is a flowchart showing a processing procedure of output means included in the controller when the traveling speed changeover switch is configured to be changed to the third speed.

17 is a diagram showing characteristics of a third speed corresponding to the characteristics of FIG. 6A in the second embodiment shown in FIG.

18 is a diagram showing characteristics of a third speed corresponding to the characteristics of FIG. 6B in the second embodiment shown in FIG.

19 is a diagram showing characteristics of a third speed corresponding to the characteristics of FIG. 8A in the third embodiment shown in FIG. 7.

20 is a diagram showing characteristics of a third speed corresponding to the characteristics of FIG. 8B in the third embodiment shown in FIG. 7.

FIG. 21 is a circuit diagram showing a main configuration of a conventional hydraulic drive system for an open center hydraulic excavator.

22 is a diagram showing a relationship between a lever operation amount and a pump flow rate in the conventional technique shown in FIG.

23 is a diagram showing the relationship between the lever operation amount and the pump pressure in the conventional technique shown in FIG.

FIG. 24 is a diagram showing a relationship between a lever operation amount and a motor supply amount in the conventional technique shown in FIG. 21.

FIG. 25 is a circuit diagram showing a main configuration of a conventional hydraulic drive device for a closed center type hydraulic excavator.

26A and 26B are views for explaining the unload valve provided in the conventional technique shown in FIG. 25, FIG. 26A is a diagram showing the configuration of the unload valve, and FIG. 26B is a diagram showing the opening characteristic of the unload valve;
(C) is a figure which shows the flow volume characteristic of the said unloading valve.

27 is a diagram showing a relationship between a motor supply flow rate and a motor rotation speed, which is common to the conventional technique shown in FIG. 21 and the conventional technique shown in FIG. 25.

28 is a diagram showing a relationship between load pressure and torque of the hydraulic motor common to the conventional technique shown in FIG. 21 and the conventional technique shown in FIG. 25.

[Explanation of symbols]

 1 prime mover 2 variable displacement hydraulic pump 3 regulator (pump tilt angle control device) 4 travel variable displacement hydraulic motor 5 motor tilt angle switching device 6 travel speed changeover switch (travel speed selection means) 7 travel direction control valve 7a center Bypass passage 8 Electric lever device (operating device) 8a Operating device 9 Proportional electromagnetic pressure reducing valve 10 Shuttle valve 11 Controller (motor supply amount change control means) 12 Pilot hydraulic power source 15A Proportional electromagnetic pressure reducing valve 15B Proportional electromagnetic pressure reducing valve 16 Proportional electromagnetic pressure reducing valve 17 Pressure Sensor 18 Throttle Valve 20 Pressure Sensor 23 Unload Valve 24 Differential Pressure Sensor 28 Detection Switch 31 Pressure Sensor 32 Tilt Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area E02F 9/22 A F15B 11/00

Claims (11)

[Claims] 1. A variable displacement hydraulic pump, and a pump displacement angle control device for controlling the displacement angle of the variable displacement hydraulic pump,
Controlling a plurality of actuators including a traveling variable displacement hydraulic motor driven by pressure oil discharged from the variable displacement hydraulic pump, and a flow of pressure oil supplied from the variable displacement hydraulic pump to the traveling variable displacement hydraulic motor In a hydraulic drive system for a hydraulic working machine including a traveling directional control valve and an operating device for operating the traveling directional control valve, a tilt angle of the traveling variable displacement hydraulic motor is a predetermined small tilt angle. At this time, motor supply amount change control means for controlling the flow rate supplied to the traveling variable displacement hydraulic motor to be increased by a predetermined amount as compared with when the tilt angle is a predetermined large tilt angle is provided. The characteristic hydraulic drive for hydraulic work equipment. 2. A traveling speed selecting means for outputting a signal for determining a traveling speed of the traveling variable displacement hydraulic motor, wherein the motor supply amount changing control means supplies a supply amount according to a selection result of the traveling speed selecting means. The hydraulic drive system for a hydraulic working machine according to claim 1, which is a means for controlling the above. 3. The hydraulic drive system for a hydraulic working machine according to claim 2, wherein the motor supply amount change control means is means for controlling driving of the traveling directional control valve. 4. The hydraulic drive system for a hydraulic working machine according to claim 2, wherein the motor supply amount change control means is means for controlling the drive of the pump tilt angle control device. 5. The traveling directional control valve has a center bypass passage, and the motor supply amount change control means drives the pump tilt angle control device in response to a change in a downstream pressure of the center bypass passage. The hydraulic drive system for a hydraulic working machine according to claim 4, which is a control means. 6. The hydraulic work according to claim 4, wherein the motor supply amount change control means is a means for controlling the drive of the pump tilt angle control device in accordance with the operation amount of the operation device. Hydraulic drive of machine. 7. The motor supply amount change control means, when the tilt angle of the traveling variable displacement hydraulic motor is a predetermined small tilt angle, the tilt angle of the variable displacement hydraulic pump is a predetermined minimum tilt angle. 5. A hydraulic drive system for a hydraulic working machine according to claim 4, wherein the hydraulic drive system is a means for controlling the drive of the pump tilting angle control device so that the tilting angle becomes larger than the predetermined tilting angle. 8. A load sensing control means for controlling a pump discharge amount so that a pressure difference between a pump pressure and a load pressure of an actuator becomes a predetermined pressure difference, and the motor supply amount change control means has the predetermined value. 5. The hydraulic drive system for a hydraulic working machine according to claim 4, wherein the hydraulic drive system is means for changing the differential pressure of the hydraulic working machine. 9. The hydraulic drive for a hydraulic working machine according to claim 2, wherein the traveling speed selecting means is a traveling speed changeover switch for selecting at least one of a high speed mode and a low speed mode by a manual operation. apparatus. 10. The travel speed selecting means is means for automatically switching the tilt angle of the travel variable capacity hydraulic motor according to the tilt angle and pump pressure of the variable capacity hydraulic pump. The hydraulic drive system for the hydraulic working machine according to claim 2. 11. The motor supply device further comprises detection means for detecting that the traveling directional control valve is operated, and only when the detection means detects that the traveling directional control valve has been operated. The hydraulic drive system for a hydraulic working machine according to claim 1, further comprising means for executing the supply amount change control by the amount change control means.