JPH07139509A - Hydraulic transmission of hydraulic working machine - Google Patents

Abstract

PURPOSE:To provide the hydraulic transmission of a hydraulic working machine which provides excellent metering characteristics even in a case in which a travel variable capacity motor is in a high speed travel mode and is in the operation state of an inclination angle being small and high pressure is needed, by providing an inclination angle change control means to conduct control to change an inclination angle into a large specific one. CONSTITUTION:At the time of a low speed travel mode in which a travel speed changeover switch 7 is opened, a solenoid changeover valve 16 is kept at a closing position, so at pilot pipe passages 30, 31, pilot pressure, for example, is not generated, and as a result, a travel motor inclination angle changeover device 24 controls the inclination angle of a hydraulic motor 15 into a large inclination angle. When a travel direction control valve 12 is in a neutral state, pressure generated at a throttle valve 4 is large, and this control pressure signal is led to a regulator 6 through an oil passage 5, and at this time, the pilot pressure of the pilot pipe passage 31 to be given so as to cope with the control pressure signal is not generated, so the regulator 6 conducts control so that the inclination angle of a hydraulic pump 2 may be kept at a specific minimum 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 FIG. 7 is a circuit diagram showing a conventional hydraulic drive system for a hydraulic working machine. This conventional technique is provided, for example, in a hydraulic excavator, and includes a variable displacement hydraulic pump 2
And a plurality of actuators driven by pressure oil discharged from the variable displacement hydraulic pump, for example, the arm cylinder 3 shown in FIG. 7, a boom cylinder, a bucket cylinder, and a traveling variable that are not shown for simplification of description. Actuators such as displacement hydraulic motors and swing motors, and directional control valves for controlling these actuators, for example, for arms that control the flow of pressure oil supplied from the hydraulic pump 2 to the arm cylinder 3 and have a center bypass passage 1a The directional control valve 1 and a pressure generating device for detecting the pressure generated in the downstream of the center bypass passage of each directional control valve, for example, as shown in FIG. 4 and a pump tilt angle control device for controlling the target displacement of the hydraulic pump, for example, the regulator 6 Includes a signal line leading to the regulator 6 to the pressure generated by the throttle valve 4 as a control pressure signal, namely an oil passage 5. The throttle valve 4 and the oil passage 5 described above constitute a driving unit that drives the regulator 6 in accordance with a switching operation of the arm directional control valve 1.

Further, the regulator 6 described above includes a piston 6a and a piston 6a as shown in FIG.
Small-diameter chamber 6b and large-diameter chamber 6c in which the respective ends of the
And a flow rate control spool 6d that operates according to the value of the control pressure signal guided by the oil passage 5. The small diameter chamber 6b described above is connected to the discharge conduit of the hydraulic pump 2, and the large diameter chamber 6c can be selectively connected to the small diameter chamber 6b or the tank according to the operation of the flow rate control spool 6. .

The characteristics of the regulator 6 are as follows. That is, when the arm directional control valve 1 is kept neutral, the pressure generated by the throttle valve 4 is large, and the value of the control pressure signal guided by the oil passage 5 is large accordingly, the flow rate control shown in FIG. The spool 6d moves leftward in FIG. 8, and the small diameter chamber 6b and the large diameter chamber 6c communicate with each other. At this time, the pump pressure is supplied to both the small diameter chamber 6b and the large diameter chamber 6c, and the piston 6a moves leftward in FIG. 8 due to the difference in pressure receiving area between the small diameter chamber 6b and the large diameter chamber 6c. As a result, as shown in FIG.
The hydraulic pump 2 is controlled so that it becomes a.

Further, the arm directional control valve 1 is operated to start closing the center bypass passage 1a, the pressure generated by the throttle valve 4 is reduced, and the control pressure signal is changed to that shown in FIG.
When the value becomes smaller than P _C1 shown in FIG. 8, the flow rate control spool 6d shown in FIG. 8 moves to the right in FIG. 8, and the large diameter chamber 6c communicates with the tank. At this time, the piston 6a moves to the right in FIG. 8 by the pump pressure applied to the small diameter chamber 6b. As a result, as shown in FIG.
The hydraulic pump 2 is controlled so that the capacity 10b becomes gradually larger than 0a.

Further, the directional control valve 1 for the arm is switched to the maximum stroke so that the center bypass passage 1a is provided.
Is completely closed, or this center bypass passage 1
When a becomes the minimum opening area, the pressure generated by the throttle valve 4 becomes small, and the control pressure signal becomes a value of P _C2 or less, the hydraulic pump has a maximum capacity of 10 c at a predetermined pressure shown in FIG. 2 is controlled.

In the prior art thus constructed, for example, when the arm directional control valve 1 is gradually stroked to the right position in FIG. 7 with the intention of extending the arm cylinder 3, the arm is gradually moved. The relationship between the opening area of the center bypass passage 1a of the directional control valve 1 and the opening area of the meter-in passage 1b1 of the arm directional control valve 1 connected to the arm cylinder 3 has the characteristic shown in FIG.
That is, the opening area of the center bypass passage 1a gradually decreases as indicated by the characteristic line 20a, and conversely, the opening area of the meter-in passage 1b1 gradually increases as indicated by the characteristic line 20b. At the start of the stroke of the arm directional control valve 1, that is, at the beginning of closing the center bypass passage 1a, the hydraulic pump 2 is maintained at a predetermined minimum tilt angle, that is, the predetermined small displacement 10a of FIG. The hydraulic pump 2 discharges a standby flow rate which is a small volume corresponding to the volume 10a. Center bypass passage 1
As a is gradually reduced, the pressure of the pressure oil discharged from the hydraulic pump 2, that is, the pump pressure increases. Assuming that the load pressure of the arm cylinder 3 is a relatively low pressure P2 shown in FIG. 11B, the arm cylinder 3 starts to move when the pump pressure rises above the pressure P2. Thus, when the arm cylinder 3 starts to move and the flow rate of the hydraulic pump 2 starts to be supplied to the arm cylinder 3, the passing flow rate of the center bypass passage 1a decreases. When the passing flow rate decreases in this way, the pressure generated in the throttle valve 4 decreases. Along with this, the value of the control pressure signal applied to the regulator 6 via the oil passage 5 also decreases, and the regulator 6 drives the hydraulic pump 2 so as to increase the displacement thereof. As a result, the flow rate of the hydraulic pump 2 is gradually increased, and a predetermined flow rate characteristic, that is, a metering characteristic is obtained.

Conventionally, a relief valve or the like may be provided in place of the above-mentioned throttle valve 4 as a pressure generator arranged downstream of the center bypass passage 1a.

Further, in the case where the electric signal corresponding to the pressure generated by the above-mentioned pressure generator is output to the regulator 6 as a control pressure signal, the regulator 6 shown in FIG. 8 is replaced. As shown in FIG. 10, a first electromagnetic switching valve 6e that is arranged in a first passage that connects the small diameter chamber 6b and the large diameter chamber 6c and that opens and closes the first passage in response to a control pressure signal is provided. A second electromagnetic switching valve 6f which is arranged in the large diameter chamber 6c and the second passage connecting the first passage and the tank and which opens and closes the second passage in response to a control pressure signal.
May be provided with.

In the regulator 6 shown in FIG. 10, the second electromagnetic switching valve 6f is kept closed and the first electromagnetic switching valve 6e is operated in the open state so that the pump pressure is reduced to the small diameter chamber 6b. Is supplied to both the large diameter chamber 6c, and the piston 6a moves leftward in FIG. 10 due to the difference in pressure receiving area between the small diameter chamber 6b and the large diameter chamber 6c, so that the hydraulic pump 2 has a small capacity. Controlled. Further, by keeping the first electromagnetic switching valve 6e closed and operating the second electromagnetic switching valve 6f, the small diameter chamber 6a and the large diameter chamber 6c are shut off, and the large diameter chamber 6c becomes a tank. The piston 6a is moved to the right by the pump pressure applied to the small diameter chamber 6a, which communicates with each other.
The hydraulic pump 2 is controlled to have a large capacity.

[0011]

By the way, the above-mentioned prior art has a problem in the metering characteristic when the load pressure of the actuator is high.

For example, when the load pressure of the arm cylinder 3 shown in FIG. 7 is the relatively low pressure P2 illustrated in FIG. 11B as described above, the pump flow rate is the characteristic of FIG. 11C. As shown by a line 20d, the arm directional control valve 1 relatively gradually increases in accordance with an increase in the spool stroke, and accordingly, the flow rate supplied to the arm cylinder 3 is the characteristic of (d) in FIG. As shown by line 20f,
Similar to the above-mentioned characteristic line 20d, it increases relatively slowly as the spool stroke increases, and good metering characteristics are obtained. However, when the load pressure of the arm cylinder 3 is the high pressure P1 shown in FIG. 11B, the pump pressure is P when the hydraulic pump 2 is at the standby flow rate.
The arm cylinder 3 does not start to move unless the center bypass passage 1a is throttled so as to rise to 1 or more. Therefore, until the pump pressure exceeds P1, the center bypass passage 1
When a is throttled, the center bypass flow rate is sufficiently reduced, and the pump flow rate is rapidly increased as shown by the characteristic line 20e in FIG. Along with this, the flow rate supplied to the arm cylinder 3 is 20 g of the characteristic line of (d) of FIG.
As indicated by, the relationship becomes abruptly increased as the spool stroke of the arm directional control valve 1 is approximated to the above-mentioned characteristic line 20e, and the metering characteristic deteriorates.

The above is the same when the actuator is a traveling variable displacement hydraulic motor (not shown) for driving the traveling body forming the lower portion of the hydraulic shovel.

The variable displacement hydraulic motor for traveling is usually driven by a traveling speed changeover switch to a second speed of a low speed traveling mode and a high speed traveling mode, or a low speed traveling mode, a medium speed traveling mode,
It is designed so that it can be switched to the third speed in the high-speed running mode. The variable displacement hydraulic motor for traveling has its displacement controlled by the traveling motor tilt angle switching device, and the traveling motor tilt angle switching device operates in response to the signal output from the traveling speed changeover switch. There is.

In the case where the traveling speed is controlled by the tilt angle of the hydraulic motor, when the predetermined torque required to rotate the hydraulic motor is to be obtained, the tilt angle of the hydraulic motor is set in the low speed traveling mode. Becomes large and low pressure is sufficient, but in the high speed traveling mode, the tilt angle becomes small and high pressure is required.
Therefore, when a large torque is required, for example, when the traveling body climbs up a slope in the high speed traveling mode or turns left and right, the pump flow rate with respect to the change in the spool stroke of the traveling directional control valve (not shown) is as described above. The characteristics (characteristics in the case of high pressure) are almost the same as the characteristic line 20e in FIG. 11C, and the hydraulic motor supply flow rate for traveling with respect to changes in the spool stroke of the traveling directional control valve (not shown) is shown in the figure. The characteristic (characteristic in the case of high pressure) is almost the same as the characteristic line 20g of (d) 11 and the metering characteristic deteriorates.

As described above, in the prior art having the variable displacement hydraulic motor for traveling, when the vehicle is climbing up a slope in the high speed traveling mode as described above, the metering characteristic deteriorates. There is a risk that the driver may suddenly start even if he / she intends to switch the operation to, the fine operation is difficult, and the operator is apt to feel tired.

The present invention has been made in view of the above-mentioned situation in the prior art, and an object thereof is to require a high pressure in a traveling variable displacement hydraulic motor in an operating state in which a tilt angle is small in a high speed traveling mode. Even in the case, it is an object of the present invention to provide a hydraulic drive system for a hydraulic working machine that can obtain good metering characteristics.

[0018]

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, which comprises a traveling directional control valve and a drive means for driving the pump tilt angle control device according to an operation of the traveling directional control valve, When the motor has a predetermined small tilt angle, a tilt angle change control means is provided for controlling the tilt angle of the variable displacement hydraulic pump to a predetermined tilt angle larger than a predetermined minimum tilt angle. It is configured.

[0019]

Since the present invention is configured as described above, when the traveling variable displacement hydraulic motor is in a small tilt state in the high speed traveling mode, the tilt angle changing control means operates to operate the variable displacement hydraulic pump. The tilt angle is changed to a predetermined tilt angle that is larger than a predetermined minimum tilt angle. As a result, the standby flow rate becomes larger than the standby flow rate in the case of the above-mentioned predetermined minimum tilt angle. As a result, the degree of increase in the pump flow rate with respect to the increase in the spool stroke of the traveling directional control valve becomes gentler than in the case where the standby flow rate is small and the load pressure of the traveling variable displacement hydraulic motor is high, as in the prior art. Therefore, good metering characteristics can be obtained.

[0020]

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. FIG. 1 shows claims 1, 2,
FIG. 3 is a circuit diagram showing a first embodiment of the present invention corresponding to No. 3, showing a hydraulic drive device of a hydraulic excavator, for example. In FIG. 1, for simplification of description, actuators other than those related to traveling, such as a boom cylinder, an arm cylinder, a bucket cylinder, a swing motor, etc., and directional control valves for controlling the drive of these actuators, etc. Are not shown. Also, the same components as those shown in FIG. 7 are designated by the same reference numerals.

That is, even in the first embodiment shown in FIG. 1, the variable displacement hydraulic pump 2 and the pump tilt angle control device for controlling the displacement of the hydraulic pump 2, that is, the tilt angle. A regulator 6 is provided, and the regulator 6 has the same configuration as that shown in FIG. 8 described above, for example. Further, a traveling variable displacement hydraulic motor 15 for driving a traveling body (not shown) and a traveling direction control valve 12 for controlling the flow of pressure oil supplied from the hydraulic pump 2 to the hydraulic motor 15 are provided. Control valve 12
Has a center bypass passage. In the first embodiment shown in FIG. 1 as well, similar to the one shown in FIG. 7, a throttle valve 4 is provided downstream of the center bypass passage and constitutes a pressure generating device for generating pressure, and the throttle valve 4 The oil passage 5 that guides the pressure generated in step 6 to the regulator 6 as a control pressure signal.
It has and. The throttle valve 4 and the oil passage 5 constitute drive means for driving the regulator 6 in response to the switching operation of the traveling direction control valve 12.

Further, the traveling motor inclination angle switching device 24 for controlling the inclination angle of the hydraulic motor 15, the constant pressure source 14 capable of supplying a predetermined pressure, the constant pressure source 14 and the traveling motor inclination angle switching device 24. A pilot line 30 that communicates with each other, an electromagnetic switching valve 16 provided in the middle of the pilot line 30, a low-speed traveling mode or a high-speed traveling mode that is selectable, and a signal corresponding to the corresponding traveling mode. Is output to the electromagnetic switching valve 16, a traveling speed selection switch 7, a constant power source 17 connected to the traveling speed selection switch 7, and a pilot pressure output from the electromagnetic switching valve 16 are control pressure signals guided by the oil passage 5. And another pilot conduit 31 that leads to the regulator 6 so as to oppose the above.

The above-mentioned constant pressure source 14 and the pilot conduit 3
0, the electromagnetic switching valve 16, the traveling speed selection switch 7,
The constant power source 17 constitutes a traveling speed selecting means for outputting a signal for determining the traveling speed of the hydraulic motor 15 to the traveling motor tilt angle switching device 24. Another pilot line 3 mentioned above
1 is linked with the operation of selecting the high-speed traveling mode by the traveling speed selecting means described above so that the tilt angle of the hydraulic pump 2 becomes a predetermined tilt angle larger than the predetermined minimum tilt angle at the normal time. And constitutes an operating means for operating the regulator 6. Further, when the hydraulic motor 15 has a predetermined small tilt angle, the tilt angle of the hydraulic pump 2 is set to a predetermined tilt angle larger than the predetermined minimum tilt angle by the operating means and the speed selecting means. A tilt angle change control means for performing the change control is configured.

In the first embodiment thus constructed, the electromagnetic switching valve 16 is kept in the closed position in the low speed traveling mode in which the traveling speed selector switch 7 is opened as shown in FIG. Therefore, for example, no pilot pressure is generated in the pilot conduits 30 and 31, so that the traveling motor tilt angle switching device 24 controls the tilt angle of the hydraulic motor 15 to a large tilt angle. When the traveling directional control valve 12 is in the neutral state shown in FIG. 1, the pressure generated in the throttle valve 4 is large, and this large control pressure signal is guided to the regurator 6 via the oil passage 5, and at this time. Since the pilot pressure of the pilot line 31 which is given so as to oppose the control pressure signal is not generated, this regulator 6 keeps the tilt angle of the hydraulic pump 2 at a predetermined minimum tilt angle, that is, the pump flow rate. Is controlled so that the standby flow rate is a predetermined minimum flow rate.

When the traveling directional control valve 12 is switched in this state, the pressure generated in the throttle valve 4 gradually decreases,
That is, the value of the control pressure signal becomes smaller, and accordingly, the reguulator 6 operates to increase the tilt angle of the hydraulic pump 2. As a result, the pump flow rate is controlled by the directional control valve 1.
A corresponding increase in the spool stroke of 2 causes the increased flow rate to be supplied to the hydraulic motor 15. In this low speed traveling mode, the hydraulic motor 15 is used even when a relatively large torque is required when the traveling body climbs up a slope.
Since the tilt angle of is a large tilt, such a climbing operation of the running body can be realized at a low pressure.

At this time, the relationship between the spool stroke of the traveling directional control valve 12 and the pump pressure has the same characteristic as that shown by the solid line in FIG. 11 (b). Further, since the pressure is, for example, about P2, the relationship between the spool stroke of the traveling directional control valve 12 and the pump flow rate is the same as that illustrated by the characteristic line 20d in FIG. 11C. Along with this, the relationship between the spool stroke of the traveling directional control valve 12 and the supply flow rate to the hydraulic motor 15 becomes the same as that illustrated by the characteristic line 20f in FIG. The degree of increase in the supply flow rate is moderate, and good metering characteristics are obtained. Therefore, fine operability is excellent, and it is easy to prevent sudden start.

In the high speed traveling mode in which the traveling speed changeover switch 7 is closed, the electromagnetic changeover valve 16 is switched to the communication position which is the lower stage position in FIG. The pilot pressure from the source 14 is guided, and the traveling motor tilt angle switching device 24 controls the tilt angle of the hydraulic motor 15 to a small tilt angle. When the traveling directional control valve 12 is in the neutral state in FIG. 1, the pressure generated in the throttle valve 4 is large as described above, and this large control pressure signal is guided to the regurator 6 via the oil passage 5. At the same time, however, the pilot pressure from the constant pressure source 14 described above is applied to the regulator 6 via the pilot conduit 31 so as to oppose the control pressure signal. As a result, the regulator 6 maintains the tilt angle of the hydraulic pump 2 at a predetermined tilt angle that is larger than the predetermined minimum tilt angle, that is, the pump flow rate is higher than the above-mentioned predetermined minimum flow standby flow rate. Control to change to a large predetermined standby flow rate.

When the traveling directional control valve 12 is switched in this state, the pressure generated by the throttle valve 4 is gradually reduced as described above, that is, the value of the control pressure signal is reduced, and accordingly, the regulator 6 is hydraulically operated. It operates so as to increase the tilt angle of the pump 2. As a result, the pump flow rate increases in accordance with the increase in the spool stroke of the traveling directional control valve 12, and the increased flow rate is supplied to the hydraulic motor 15. In this high-speed traveling mode, when the traveling body requires a relatively large torque such as when climbing a slope, the tilt angle of the hydraulic motor 15 is small. The pressure becomes high during operation.

The relationship between the spool stroke of the traveling directional control valve 12 and the pump pressure at this time is shown by, for example, the characteristic line 20h shown by the one-dot chain line in FIG. 11 (b). As can be seen from the characteristic line 20h, as the standby flow rate of the hydraulic pump 2 is increased, a pressure exceeding the high pressure P1 is obtained with a spool stroke sufficiently before the characteristic line of the related art shown in FIG. 7 described above. be able to. That is, as indicated by a dashed-dotted characteristic line 20i in FIG. 11C, the pump flow rate starts to increase from a smaller spool stroke than in the case of the conventional high pressure (characteristic line 20e) shown in FIG. As a result, as shown by a dashed-dotted characteristic line 20j in FIG. 11D, the spool stroke is reduced from the spool stroke smaller than that of the conventional characteristic line 20g shown in FIG. The supply of the flow rate can be started, the degree of increase of the supply flow rate with respect to the increase of the spool stroke can be made gentle as compared with the characteristic line 20g of the prior art, and good metering characteristics can be obtained. Therefore,
As described above, even in the high-speed traveling mode, excellent fine operability can be secured, sudden start and the like can be easily prevented, and a feeling of fatigue given to the operator can be reduced.

In the first embodiment described above, the traveling speed changeover switch 7 constituting the traveling speed selecting means is constituted by switching between the low speed traveling mode and the high speed traveling mode, which is shown in FIG. As described above, it may be configured by the traveling speed changeover switch 21 that switches to the third speed of the low speed traveling mode, the medium speed traveling mode, and the high speed traveling mode, or may be configured to switch to the fourth speed or more.

In the low-speed traveling mode in which the switching position 21a is switched to the one shown in FIG. 5, the electromagnetic switching valve 16 is in the closed position and does not generate, for example, pilot pressure in the pilot conduits 30 and 31, and is not shown here. The tilt angle of the hydraulic motor 16 is controlled to the maximum tilt angle, the tilt angle of the hydraulic pump 2 is controlled to the minimum tilt angle, and the standby flow rate is controlled to the minimum flow rate accordingly. In the high-speed traveling mode in which the switching position 21c is switched, the electromagnetic switching valve 16 is in the fully open position, and the constant pressure source 1 is provided in the pilot lines 30 and 31.
4 generates the maximum pilot pressure, and the hydraulic motor 16
The tilt angle of the hydraulic pump 2 is controlled to the minimum tilt angle, and the tilt angle of the hydraulic pump 2 is controlled to the first tilt angle which is sufficiently larger than the minimum tilt angle. The first flow rate is controlled to be sufficiently larger than the first flow rate. Further, in the medium speed traveling mode in which the switching position 21b is switched to, the electromagnetic switching valve 16 is in the half-open position, and the pilot pipelines 30, 3 are opened.
1 to generate a pilot pressure smaller than the maximum pilot pressure to control the tilt angle of the hydraulic motor 16 to a tilt angle intermediate between the minimum tilt angle and the above-described maximum tilt angle, and to tilt the hydraulic pump 2. The angle is larger than the minimum tilt angle
The second tilt angle is controlled to be smaller than the tilt angle, and accordingly, the standby flow rate is controlled to the second flow rate which is larger than the minimum flow rate and smaller than the above-described first flow rate.

In the case of switching to the fourth speed or more, the standby flow rate according to each traveling mode of the fourth speed can be obtained in the same manner as described above, and the characteristic line of FIG. It is possible to obtain a plurality of characteristics similar to those exemplified in 20j.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention corresponding to claims 1, 2, and 4. The second embodiment also shows a hydraulic drive system for a hydraulic excavator, for example, as in the first embodiment.

Also in the second embodiment, the traveling directional control valve 12 for controlling the flow of the pressure oil supplied from the variable displacement hydraulic pump 2 to the traveling variable hydraulic motor 15 has the center bypass passage.

Driving means for driving the regulator 6 in response to the operation of the traveling directional control valve 12 is provided downstream of the center bypass passage of the traveling directional control valve 12, and the operation amount of the traveling directional control valve 12 is controlled. A throttle valve 4 for generating a pressure corresponding to the pressure in the downstream of the center bypass passage, a pilot pipe 5a for guiding the pressure generated by the throttle valve 4, and a pressure guided by the pilot pipe 5a are detected to detect an electric signal. Pressure sensor 9, a signal line 5b for guiding a signal detected by the pressure sensor 9, and a constant pressure source 14
According to the detection signal of the pressure sensor 9 guided via the signal line 5b, the pilot line 33 connecting the constant pressure source 14 and the regulator 6, the proportional solenoid valve 13 provided in the pilot line 33. And a controller 11 having a first output means for calculating a first target value for driving the proportional solenoid valve 13 and outputting a drive signal corresponding to the first target value, and an output from this controller 11. And a signal line 34 for supplying the drive signal to the proportional solenoid valve 13.

Further, the traveling speed selecting means for outputting a signal for determining the traveling speed of the hydraulic motor 15 to the traveling motor tilt angle switching device 24 is the above-mentioned constant pressure source 14 and this constant pressure source 14
And a traveling motor tilt angle switching device 24, a pilot line 30, a solenoid switching valve 25 provided in the pilot line 30, and one of two traveling modes, a low-speed traveling mode and a high-speed traveling mode. A traveling speed changeover switch 7 that is selectable and outputs a signal according to the selected traveling mode, a constant power source 17 connected to this traveling speed changeover switch 7, and a traveling speed changeover switch built in the controller 11 described above. The second output means for discriminating the signal outputted from the No. 7 and outputting the drive signal corresponding to the discrimination result to the electromagnetic switching valve 25 through the signal line 32.

Further, the tilt angle changing control means is constituted, and the tilt angle of the hydraulic pump 2 is larger than a predetermined minimum tilt angle in cooperation with the operation of selecting the high speed running mode by the running speed selecting means described above. The interlocking means for actuating the regulator 6 to have a predetermined tilt angle is the controller 11 described above.
It is determined whether or not the high speed traveling mode is selected based on the signal output from the traveling speed changeover switch 7 built in, and when the result of the determination is the high speed traveling mode, the signal output from the pressure sensor 9 is corrected. The hydraulic pump 2 is constituted by a third output means for outputting to the proportional solenoid valve 13 a drive signal in which the tilt angle of the hydraulic pump 2 becomes a predetermined tilt angle larger than the above-mentioned predetermined minimum tilt angle.

In the second embodiment, when the traveling speed changeover switch 7 is opened as shown in FIG. 2 in the low speed traveling mode, the second speed of the controller 11 is changed according to the signal from the traveling speed changeover switch 7. When it is determined that the output means is in the low speed traveling mode, a signal for keeping the electromagnetic switching valve 25 in the non-excited state is output. As a result, the electromagnetic switching valve 25 is kept in the closed position shown in FIG. 2, and, for example, no pilot pressure is generated in the pilot conduit 30, so that the traveling motor tilt angle switching device 24 causes the tilt angle of the hydraulic motor 15 to rise. Is controlled to a large tilt angle. When the traveling directional control valve 12 is in the neutral state shown in FIG. 2, the pressure generated by the throttle valve 4 is large, and this large pressure is detected by the pressure sensor 9, and its detection signal is sent via the signal line 5b to the controller. 11 is input. The first output means of the controller 11 is a first target value for driving the proportional solenoid valve 13 in response to the input detection signal of the pressure sensor 9 (in this case, the first target value corresponding to the neutral state).
Target value) and outputs a drive signal corresponding to the first target value to the proportional solenoid valve 13 via the signal line 34.
As a result, the proportional solenoid valve 13 is driven so as to increase the secondary pressure which is the control pressure, and the secondary pressure is guided to the reguulator 6, and this regulator 6 changes the tilt angle of the hydraulic pump 2 to a predetermined minimum tilt angle. It is controlled so as to keep the angle, that is, the pump flow rate becomes a standby flow rate which is a predetermined minimum flow rate.

When the traveling directional control valve 12 is switched in this state, the pressure generated in the throttle valve 4 gradually decreases,
That is, the value of the detection signal of the pressure sensor 9 becomes smaller, and the first target value calculated by the first output means of the controller 11 becomes smaller accordingly, and the drive output from the first output means becomes smaller. The proportional solenoid valve 13 is driven by the signal so that the secondary pressure becomes small, and the small secondary pressure causes the reguulator 6 to increase the tilt angle of the hydraulic pump 2. As a result, the pump flow rate increases in accordance with the increase in the spool stroke of the traveling directional control valve 12,
The increased flow rate is supplied to the hydraulic motor 15.

Therefore, also in the second embodiment, as in the first embodiment described above, in the low speed traveling mode,
Since the tilt angle of the hydraulic motor 15 is a large tilt even when a relatively large torque is required when the traveling body climbs up a slope, such a climbing operation of the traveling body can be realized at a low pressure. Therefore, the increase in the supply flow rate of the hydraulic motor 15 with respect to the increase in the spool stroke of the traveling directional control valve 12 is moderate, and good metering characteristics can be obtained.

When the traveling speed changeover switch 7 is closed in the high speed traveling mode, the second output means of the controller 11 is determined to be in the high speed traveling mode in response to the signal from the traveling speed changeover switch 7. A signal for switching the electromagnetic switching valve 25 to the left position in FIG. 2 is output. As a result, the electromagnetic switching valve 25 is switched to the communicating position, and the pilot pressure supplied by the constant pressure source 14 is generated in the pilot conduit 30. The pilot pressure causes the traveling motor tilt angle switching device 24 to tilt the hydraulic motor 15. Drive to make the angle a small tilt angle. When the traveling directional control valve 12 is in the neutral state shown in FIG. 2, the pressure generated by the throttle valve 4 is large as described above, and this large pressure is detected by the pressure sensor 9, and the detected signal is the signal line 5b. Is input to the controller 11 via. Since the vehicle is currently in the high-speed traveling mode, the third output means of the controller 11 then corrects the first target value corresponding to the neutral state described above by a predetermined correction coefficient (0 <correction coefficient <1). Then, a drive signal corresponding to the corrected target value is output to the proportional solenoid valve 13 via the signal line 34. As a result, the proportional solenoid valve 13 is driven so as to output a secondary pressure smaller than the neutral secondary pressure in the low speed traveling mode, and a relatively small secondary pressure in consideration of the correction coefficient is guided to the regulator 6. Then, the regulator 6 changes the tilt angle of the hydraulic pump 2 to a predetermined tilt angle that is larger than the above-mentioned predetermined minimum tilt angle, that is, the standby flow rate in which the pump flow rate is the predetermined minimum flow rate. It is controlled so that the standby flow rate is larger than that of.

When the traveling directional control valve 12 is switched in this state, the pressure generated in the throttle valve 4 becomes small as described above, that is, the value of the detection signal of the pressure sensor 9 becomes small, and the controller 11 is accompanied by this. Is the first in response to the detection signal of the pressure sensor 9 reduced by the first output means.
Is calculated, and the third output means multiplies the first target value by a correction coefficient to calculate a corrected target value, and the drive signal corresponding to the corrected target value is proportional. Output to the solenoid valve 13. As a result, the proportional solenoid valve 13 is driven so that its secondary pressure becomes smaller, and the reguulator 6 operates so as to increase the tilt angle of the hydraulic pump 2. Along with this, the pump flow rate increases corresponding to the increase of the spool stroke of the directional control valve 12, and the increased flow rate is supplied to the hydraulic motor 15. In the second embodiment as well, in the high speed traveling mode as in the first embodiment, when the traveling body requires a relatively large torque such as when climbing a slope, the tilt angle of the hydraulic motor 15 is small. Since it is rolling, a high pressure is generated during such a climbing operation of the traveling body. However, the dashed-dotted characteristic line 20j in FIG.
Similarly to the above, the characteristic line of the prior art shown in FIG.
The spool stroke is smaller than that of the hydraulic motor 15
It is possible to start the flow rate supply to, and to moderate the increase of the supply flow rate with respect to the increase of the spool stroke, as compared with the characteristic line 20g of the prior art, and to obtain good metering characteristics. An effect equivalent to that of the embodiment is obtained.

In the second embodiment described above, the traveling speed changeover switch 7 constituting the traveling speed selecting means is constituted by switching between the low speed traveling mode and the high speed traveling mode, which is shown in FIG. As described above, the switching position 40a may be a low speed traveling mode, the switching position 40b may be a medium speed traveling mode, and the switching position 40c may be a high speed traveling mode. It may be configured by switching to.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention, and FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention. These third embodiment and fourth embodiment are This corresponds to claim 5.

FIG. 3 is drawn corresponding to FIG. 1 described above. The third embodiment shown in FIG. 3 is provided with a shuttle valve 18 for taking out pilot pressure for driving the traveling directional control valve 12 as a detecting means for detecting that the traveling directional control valve 12 has been operated. . In addition, the pressure switch 1 for connecting and disconnecting the traveling speed changeover switch 7 and the electromagnetic changeover valve 16
9 and a pilot line 35 connecting the shuttle valve 18 and the pressure switch 19. Other configurations are
This is equivalent to the above-described first embodiment shown in FIG.

The above-mentioned pressure switch 19 and pilot line 35 are controlled by the tilt angle changing control means only when the shuttle valve 18 detects that the traveling directional control valve 12 has been operated. Of the hydraulic pump 2 to a predetermined tilt angle larger than the minimum tilt angle by generating a pilot pressure in the pilot conduit 31 to operate the regulator 6. The selective execution means that enables execution of the control to be changed is configured.

In the third embodiment shown in FIG. 3, when the traveling directional control valve 12 is operated, the pilot pressure for operating the traveling directional control valve 12 is immediately transferred via the shuttle valve 18 to the pilot line. 35, pressure switch 19
Is activated to connect the traveling speed changeover switch 7 and the electromagnetic changeover valve 16. Therefore, when the traveling speed changeover switch 7 is closed and the high speed traveling mode is selected, the electromagnetic changeover valve 16 is changed over to the communicating position, and the pilot conduit 3
A pilot pressure is generated at 1, and the standby flow rate is controlled to be large as in the first embodiment, and good metering characteristics are obtained. When the traveling directional control valve 12 is not operated, the electromagnetic switch valve 16 is held in the closed position because the pressure switch 19 is opened, so that the pilot pressure is not generated in the pilot conduit 31 and the hydraulic pump The standby flow rate of 2 is kept at the normal minimum flow rate.

Depending on the type of work performed by the hydraulic excavator and the type of actuator, the standby flow rate may not necessarily be increased in advance.
The third embodiment is suitable for such a case.

Further, FIG. 4 is drawn corresponding to FIG. 2 described above. In the fourth embodiment shown in FIG. 4, as the detecting means for detecting the operation of the traveling directional control valve 12, the traveling directional control valve 12 is driven as in the third embodiment. Shuttle valve 18 for extracting pilot pressure
Is equipped with.

Further, the pressure sensor 20 which outputs a detection signal corresponding to the pressure detected by the shuttle valve 18, and the detection signal output from the pressure sensor 20 are supplied to the controller 11
The signal line 20a leading to the
It is determined whether or not the detection signal indicating that the traveling directional control valve 12 has been operated is input from the pressure sensor 20, and when it is determined that the corresponding detection signal is input, it is described in the second embodiment described above. When it is determined that the operation of the third output means is valid and it is determined that the corresponding detection signal is not input, the operation of the third output means of the second embodiment is invalidated, and the first output means is disabled. And a traveling operation determination means for making a decision to output a drive signal according to the first target value by the output means. Other configurations are the same as those of the second embodiment shown in FIG. 2 described above.

The pressure sensor 20 described above and the signal line 20a
And the traveling operation determination means of the controller 11 can execute the tilt angle changing control by the tilt angle changing control means only when the shuttle valve 18 detects that the traveling directional control valve 12 has been operated. , The proportional solenoid valve 13 is operated to operate the regulator 6,
It constitutes a selective execution means that enables execution of control for changing the tilt angle of the hydraulic pump 2 to a predetermined tilt angle larger than the minimum tilt angle.

In the fourth embodiment shown in FIG. 4, when the traveling directional control valve 12 is operated, the pilot pressure for operating the traveling directional control valve 12 is immediately taken out via the shuttle valve 18, The pressure sensor 20 operates and the detection signal is input to the controller 11 via the signal line 20a. When the detection signal from the pressure sensor 20 is input, the traveling operation determination means built in the controller 11
As described above, it is determined that the operation of the third output means described in the second embodiment is valid. Therefore, when the traveling speed changeover switch 7 is closed and the high speed traveling mode is selected, the drive signal corresponding to the correction target value obtained by the third output means is output to the proportional solenoid valve 13, and the proportional solenoid valve 13 is output. Is controlled so that the standby flow rate is increased in the same manner as in the first embodiment, and good metering characteristics are obtained. In addition, the traveling directional control valve 12
Is not operated, the traveling determination means makes the operation of the third output means of the second embodiment invalid, and the first output means makes a decision to output the drive signal according to the first target value. The standby flow rate of the hydraulic pump 2 is kept at the normal minimum flow rate.

Even in the fourth embodiment constructed as described above, as in the case of the third embodiment described above, when the standby flow rate does not necessarily have to be increased in advance depending on the type of work or the type of actuator. Is preferred.

[0054]

As described above, the present invention has the above-described structure, and therefore, even when the traveling variable displacement hydraulic motor is in a high-speed traveling mode in an operating state with a small tilt angle and a high pressure is required, good metering characteristics are obtained. Therefore, as compared with the prior art, the fine operability is excellent, the sudden start and the like can be easily prevented, and the feeling of fatigue given to the operator can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of a hydraulic drive system for a hydraulic working machine according to the present invention.

FIG. 5 is a diagram showing another example of the traveling speed switching switch provided in the first embodiment shown in FIG.

FIG. 6 is a diagram showing another example of the traveling speed changeover switch provided in the second embodiment shown in FIG.

FIG. 7 is a circuit diagram showing a conventional hydraulic drive system for a hydraulic working machine.

8 is a diagram showing a configuration of a regulator provided in the hydraulic drive system shown in FIG.

9 is a characteristic diagram showing the relationship between the control pressure applied to the regulator provided in the hydraulic drive system shown in FIG. 7 and the displacement of the variable displacement hydraulic pump.

FIG. 10 is a diagram showing another example of a regulator.

11 is a diagram showing characteristics obtained by the hydraulic drive system shown in FIG.

[Explanation of symbols]

2 Variable Capacity Hydraulic Pump 4 Throttle Valve (Pressure Generating Device) [Drive Means] 5 Oil Passage (Drive Means) 5a Oil Passage (Drive Means) 5b Signal Line (Drive Means) 6 Regulator (Pump Tilt Angle Control Device) 7 Travel speed selector switch (travel speed selection means) 9 Pressure sensor (drive means) 11 Controller (drive means, travel speed selection means, interlocking means, selective execution means) 12 Travel direction control valve 13 Proportional solenoid valve (drive means) 14 constant pressure source (travel speed selection means, drive means) 15 variable displacement hydraulic motor for travel (actuator) 16 electromagnetic switching valve (travel speed selection means) 17 constant power source (travel speed selection means) 18 shuttle valve (detection means) 19 pressure Switch (selective execution means) 20 Pressure sensor (selective execution means) 20a Signal line (selective execution means) 21 Travel speed Change switch (travel speed selection means) 24 Travel motor tilt angle switching device 25 Electromagnetic switching valve (travel speed selection means) 30 Pilot line (travel speed selection means) 31 Another pilot line (interlocking means) 32 Signal line ( Travel speed selection means) 33 Pilot pipeline (driving means) 34 Signal line (drive means) 35 Pilot pipeline (selective execution means) 40 Travel speed changeover switch (travel speed selection means)

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Claims (5)

[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 A hydraulic drive system for a hydraulic working machine, comprising: a traveling directional control valve for driving; and a drive means for driving the pump tilting angle control device according to an operation of the traveling directional control valve. When the motor has a predetermined small tilt angle, a tilt angle change control means is provided for controlling the tilt angle of the variable displacement hydraulic pump to a predetermined tilt angle larger than a predetermined minimum tilt angle. A hydraulic drive system for a hydraulic working machine characterized by the above. 2. A travel motor tilt angle switching device for controlling a tilt angle of the travel variable displacement hydraulic motor, and a signal for determining a travel speed of the travel variable displacement hydraulic motor, the travel motor tilt angle switching device being a signal for determining a travel speed of the travel variable displacement hydraulic motor. And a tilt speed change control means for interlocking with the selection operation of the high speed travel mode by the travel speed selection means so that the tilt angle of the variable displacement hydraulic pump is set to the predetermined value. 2. The hydraulic drive system for a hydraulic working machine according to claim 1, wherein the hydraulic drive system is interlocking means for operating the pump tilt angle control device so that the tilt angle becomes equal to 2. 3. The traveling directional control valve has a center bypass passage, the drive means is provided downstream of the center bypass passage of the traveling directional control valve, and the operation amount of the traveling directional control valve is set. A pressure generating device for generating a pressure corresponding to the downstream side, and an oil passage for guiding the pressure generated by the pressure generating device to the pump tilt angle control device, and the traveling speed selecting means sets a predetermined pressure. A constant pressure source that can be supplied, and a pilot line that connects the constant pressure source to the traveling motor tilt angle switching device,
It is possible to select at least one of two driving modes, a low speed running mode and a high speed running mode, and an electromagnetic switching valve provided in the pilot conduit, and a signal according to the selected running mode is sent to the electromagnetic switching valve. It includes a traveling speed changeover switch for output and a power supply connected to this traveling speed changeover switch, and outputs the pilot pressure output from the electromagnetic changeover valve as a pilot signal for determining the traveling speed through the pilot pipe line. When the high speed traveling mode is selected by the traveling speed changeover switch, the means controls the pilot pressure introduced to the pilot pipe so that the tilt angle of the variable displacement hydraulic pump becomes the predetermined tilt angle. 3. A hydraulic drive system for a hydraulic working machine according to claim 2, which is another pilot line leading to the pump tilt angle control device. Apparatus. 4. The traveling directional control valve has a center bypass passage, the drive means is provided downstream of the center bypass passage of the traveling directional control valve, and an operation amount of the traveling directional control valve is set. A pressure generator for generating a pressure corresponding to the above in the downstream, a pressure sensor for detecting the pressure generated by the pressure generator,
A constant pressure source, a pilot line connecting the constant pressure source and the pump tilt angle control device, a proportional solenoid valve provided in the pilot line, and the proportional according to the signal output from the pressure sensor. And a controller incorporating first output means for calculating a first target value for driving the solenoid valve and outputting a drive signal corresponding to the first target value to the proportional solenoid valve, The traveling speed selection means, a constant pressure source capable of supplying a predetermined pressure, and a pilot line connecting the constant pressure source and the traveling motor tilt angle switching device,
An electromagnetic switching valve provided in the pilot line and at least one of two traveling modes, a low-speed traveling mode and a high-speed traveling mode, can be selected, and a traveling speed switching that outputs a signal according to the selected traveling mode. A switch, a power supply connected to the traveling speed changeover switch, and a signal output from the traveling speed changeover switch built in the controller are discriminated, and a drive signal corresponding to the discrimination result is output to the electromagnetic switching valve. And a second output means for outputting the pilot pressure output from the electromagnetic switching valve as a pilot signal for determining a traveling speed via a pilot conduit, and the interlocking means is incorporated in the controller to drive the traveling. Based on the signal output from the speed selector switch, determine whether the high-speed driving mode has been selected, and the determination result is high. In the traveling mode, the third embodiment outputs a drive signal to the proportional solenoid valve, which corrects the signal output from the pressure sensor and outputs a drive signal that makes the tilt angle of the variable displacement hydraulic pump equal to the predetermined tilt angle. The hydraulic drive system for a hydraulic working machine according to claim 2, wherein the hydraulic drive system is output means. 5. The tilting device is provided with a detecting means for detecting that the traveling directional control valve is operated, and only when the detecting means detects that the traveling directional control valve is operated. The hydraulic drive system for a hydraulic working machine according to any one of claims 1 to 4, further comprising: selective execution means that enables execution of tilt angle change control by the angle change control means.