JPH11210023A - Hydraulic driving device for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the pulsation of pressure oil without separately installing a tail hose used only for lowering pulsation. SOLUTION: A changeover valve 21 for turning is disposed on their midways to pipelines 27A, 27B for connecting a hydraulic pump 14 and a turning motor 13 while a make-up valve 28 and a brake valve 31 are connected in parallel between the changeover valve 21 for turning and the turning motor 13. A make-up hose 33 joining the make-up valve 28 and a tank 15 is used normally as a tail hose reducing the pulsation of pressure oil propagated in a drain pipeline 18, a pump pipeline 17 and a center bypass pipeline 16, and employed as an oil passage supplying the input port side of the turning motor 13 with a hydraulic fluid from the tank 15 when the input port side of the turning motor 13 is brought to the state of negative pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a construction machine such as a hydraulic shovel or a hydraulic crane, and is suitable for use in reducing pulsation of pressure oil generated in a hydraulic pipeline of the construction machine. Related to a hydraulic drive device.

[0002]

2. Description of the Related Art In general, construction machines such as hydraulic shovels and hydraulic cranes are provided with an upper revolving structure rotatably mounted on a lower traveling structure. A revolving device is provided between the upper revolving structure and the lower traveling structure to rotatably support the upper revolving structure. The revolving device is provided on the upper revolving structure and driven by a revolving motor to revolve the upper revolving structure. Let me.

In such a conventional construction machine, a swing motor is connected to a hydraulic pump as a hydraulic pressure source by a pair of oil passages, and a supply of pressure oil to the swing motor is provided in the middle of the oil passage. A directional control valve for controlling discharge is provided, and between the directional control valve and the slewing motor, hydraulic fluid is supplied from the tank when the input port side of the slewing motor is in a negative pressure state due to the inertial rotation of the upper slewing body. There is a known makeup valve provided with a makeup valve.

In such a conventional construction machine, the directional control valve is switched and controlled, and hydraulic oil is supplied from a hydraulic pump to the slewing motor, whereby the slewing motor is driven to rotate and the slewing motor rotates. The device is driven to swing the upper swing body.

Further, when the turning of the upper swing body is stopped, the inertial rotation of the upper swing body causes the swing motor to rotate forcibly, and the input port side of the swing motor tends to be in a negative pressure state. At this time, the makeup circuit replenishes the working oil in the tank to the input port side of the swing motor to prevent cavitation from occurring on the input port side of the swing motor.

[0006]

By the way, in the construction machine according to the prior art described above, the pressure oil discharged from the hydraulic pump due to the reciprocating motion of the piston of the hydraulic pump, etc., has a pulsation of the pressure oil whose pressure fluctuates. Is easy to occur. Such pulsation of the pressure oil propagates in the oil passage connecting the hydraulic pump and the swing motor, and also propagates to the directional control valve, thereby causing noise by vibrating the oil passage or the structure supporting the directional control valve. There is a problem of causing it.

In order to reduce such pulsation of the pressure oil, there is known a hydraulic pump in which a tail hose branched from an oil passage is connected to the discharge side of the hydraulic pump. in this case,
Since the base end of the tail hose opens into the oil passage and the distal end is closed, when the pulsation of the pressure oil propagating in the oil passage enters the tail hose, the pressure oil that has entered the tail hose The pulsation is reflected on the tip side of the tail hose and merges again into the oil passage.

At this time, the length of the tail hose is set so that the phase of the pulsation of the pressure oil propagating in the oil passage and the pulsation of the pressure oil reflected from the tail hose are reversed by 180 degrees in the oil passage. By doing so, these two pulsations interfere with each other, and the pulsation of the pressure oil in the oil passage is reduced.

However, the length of the tail hose is determined by the speed of sound and the frequency of pulsation in oil.
In the case of a construction machine such as a hydraulic shovel, for example, the speed of sound in oil is 1500 m / s, and the frequency of pulsation is about 230 Hz. Therefore, the length of the tail hose tends to be a relatively long dimension of about 1.6 m. There is. For this reason, there is a problem that an extra space is required to accommodate such a relatively long tail hose.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a hydraulic drive device for a construction machine capable of reducing pulsation of pressurized oil without separately providing a tail hose. To provide.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a lower traveling body, an upper revolving body rotatably mounted on the lower traveling body, the upper revolving body and the lower traveling body. A swing device that is provided between the swing body and the swing body to swingably support the upper swing body, a swing motor that swings the swing device, and is provided in the middle of a pair of oil passages that connect the swing motor and a hydraulic pressure source. A direction control valve for controlling the supply and discharge of pressure oil to and from the rotation motor; and a directional control valve provided between the direction control valve and the rotation motor, and operated from the tank when the input port side of the rotation motor is in a negative pressure state. The present invention is applied to a hydraulic drive of a construction machine including a makeup valve for supplying oil.

A feature of the structure adopted by the first aspect of the invention is that the makeup hose connecting between the makeup valve and the tank is a tail hose which normally reduces pulsation of pressure oil due to a hydraulic pressure source. It is configured to be used as an oil passage for replenishing hydraulic oil when the input port side of the swing motor is in a negative pressure state.

With this configuration, the make-up hose can always reduce the pulsation of the pressure oil due to the hydraulic source, and when the input port side of the swing motor is in a negative pressure state, the swing motor can be used by the makeup hose. Hydraulic oil can be supplied to the input port side.

According to a second aspect of the present invention, the makeup valve includes a pair of check valves provided between the pair of oil passages and opened only when the input port side of the swing motor is in a negative pressure state. One end of the makeup hose is connected between the check valves, and the other end is connected to a drain pipe between the direction control valve and the tank.

In this case, since each check valve is normally closed, the pulsation of the pressure oil which has entered the makeup hose from the oil passage can be reflected, and the makeup hose can be reduced by the tail hose which reduces the pulsation. Can be used as Also, when the input port side of the swing motor is in a negative pressure state, the check valve opens, so the hydraulic oil in the tank is replenished to the input port side of the swing motor through the make-up hose, and is supplied to the input port side of the swing motor. Cavitation can be prevented from occurring.

In the invention according to claim 3, the length dimension of the makeup hose is set according to the frequency of the pulsation of the pressure oil to be reduced.

Thus, when the make-up hose is used as a tail hose, the pulsation of the pressure oil according to the length of the hose can be reduced, and the hose according to the frequency of the pulsation of the pressure oil generated by the hydraulic pressure source can be reduced. By setting the length dimension, the pulsation of the pressure oil propagating from the hydraulic source toward the direction control valve and the swing motor can be reduced.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a construction machine according to an embodiment of the present invention;

FIGS. 1 to 5 show an example in which the hydraulic drive device for a construction machine according to the first embodiment is applied to a hydraulic excavator.

In the figure, 1 is a lower traveling body of a hydraulic shovel, 2
Denotes an upper revolving structure that is rotatably mounted on the lower traveling structure 1, and a revolving device 3 including an outer wheel, an inner wheel, and the like is provided between the upper revolving structure 2 and the lower traveling structure 1. The upper revolving unit 2 is supported by the revolving device 3 so as to be revolvable on the lower traveling unit 1, and the upper revolving unit 2 is provided with a driver's cab 4, a machine room 5, a later-described revolving motor 13, and the like. I have. The upper revolving unit 2 is revolved on the lower traveling unit 1 by revolvingly driving the revolving device 3 by the revolving motor 13.

Reference numeral 6 denotes a working device mounted on the front part of the upper revolving unit 2 so as to be able to move up and down. The working device 6 comprises a boom 7, an arm 8, a bucket 9, and the like. The arm 8 is rotated by the arm cylinder 11 and the bucket 9 is moved downward.
Is rotated by a bucket cylinder 12. When excavating earth and sand, the bucket 9 is rotated while the boom 7 and the arm 8 are raised and lowered, thereby excavating earth and sand at the tip end side of the bucket 9.

Next, a hydraulic drive device according to the present embodiment will be described with reference to FIGS. 2 to 5. Reference numeral 13 denotes a swing motor provided on the upper swing body 2, and the swing motor 13 is, for example, an oblique motor. It is constituted by a plate-type hydraulic motor, an oblique-axis-type hydraulic motor, or the like, and drives the entire upper revolving unit 2 to turn via a turning device 3.

A hydraulic pump 14 constitutes a hydraulic power source together with a tank 15. The hydraulic pump 14 is provided in a machine room 5 of the upper swing body 2 together with a prime mover (not shown) such as a diesel engine. The discharge side of the hydraulic pump 14 is connected to the center bypass line 16 and the hydraulic pump 14
Is driven by a motor to rotate the tank 15.
The hydraulic fluid in the center is used as high pressure
Boom cylinder 10, arm cylinder 11,
The bucket cylinder 12, the swing motor 13 and the like are discharged. The center bypass pipe 16 is provided with a pump pipe 17 connected to the input ports of the switching valves 21 to 25 described later.

Reference numeral 18 denotes a drain pipe which is located on the downstream side of the center bypass pipe 16 and connects the control valve 20 and the tank 15. An oil cooler 19 is provided in the drain pipe 18. . Then, the pressure oil discharged from the hydraulic pump 14 is supplied to the boom cylinder 10 and the like by the control valve 20, and the hydraulic oil discharged from the boom cylinder 10 and the like passes through the drain pipe 18 and is cooled by the oil cooler 19. It returns to the tank 15.

A control valve 20 is connected to the center bypass line 16, the pump line 17, and the drain line 18. The control valve 20 is, for example, a turning switching valve 21 connected to the turning motor 13. , A boom switching valve 22 connected to the boom cylinder 10, an arm switching valve 23 connected to the arm cylinder 11, a bucket switching valve 24 connected to the bucket cylinder 12, and a hydraulic motor 26 for traveling. The switching valve 25 includes a switching valve 25 for traveling.
25 constitute a parallel circuit.

Each of the switching valves 21 to 25 is controlled to switch between them so that the swing motor 13, the boom cylinder 10, the arm cylinder 11, the bucket cylinder 1
2. It controls the supply and discharge of pressure oil to and from the hydraulic motor 26.

Reference numerals 27A and 27B denote a pair of oil passages connecting the swing switching valve 21 and the swing motor 13, and the pipelines 27A and 27B are connected to the pump pipelines 17 and 27 via the swing switching valve 21. It is connected to a drain line 18.

Reference numeral 28 denotes a make-up valve provided integrally with the casing 13C of the swing motor 13, for example. The make-up valve 28 includes a pair of check valves 2 as shown in FIG.
8A, 28B, and the check valves 28A, 28
8B is provided in the middle of the oil path 29 connecting between the pipelines 27A and 27B, and is reversely connected to each other. Further, a makeup hose 33 described later is connected to a connection position 30 of the oil passage 29 located between the check valves 28A and 28B.

As shown in FIG. 4, the check valves 28A and 28B are made up of valve bodies 28A1 and 28B1 and springs 28A2.
, 28B2, the springs 28A2, 28B2 constantly urge the valve bodies 28A1, 28B1 in the direction in which the check valves 28A, 28B close. For this reason, the check valves 28A and 28B are normally closed, and are opened only when the input port side of the swing motor 13 is in a negative pressure state.
From 5, hydraulic oil is supplied to the input port side of the swing motor 13.

That is, when the port 13A of the swing motor 13 is connected to the pipeline 27A as an input side, when the port 13A of the swing motor 13 is in a negative pressure state, the check valve 28A is opened. Then, the hydraulic oil from the tank 15 is supplied to the port 13A side of the turning motor 13 through the makeup hose 33 and the pipeline 27A. In the case where the port 13B of the swing motor 13 is connected to the pipeline 27B as the input side,
When the side B is in a negative pressure state, the check valve 28B is opened, and the operating oil from the tank 15 is supplied to the makeup hose 3
3. Port 13B of the turning motor 13 through the pipe 27A
Replenish to the side.

Numeral 31 is provided integrally with the swing motor 13,
A brake valve connected in parallel to the pipelines 27A and 27B together with the make-up valve 28. The brake valve 31 is composed of a pair of overload relief valves 31A and 31B.
The overload relief valves 31A and 31B are connected to the line 27A,
The oil passages 32 are connected to each other in the middle of an oil passage 32 connecting the oil passages 27B and 27B. Also, the overload relief valves 31A, 3A
The middle of the oil path 32 located between 1B communicates with the connection position 30 of the oil path 29.

Then, the overload relief valve 31A,
Reference numeral 31B denotes an overload relief valve 3 when an excessive pressure equal to or greater than a predetermined relief set pressure is generated in the pipelines 27A and 27B during inertial rotation (slip) of the swing motor 13 or the like.
By opening the valves 1A and 31B and relieving this pressure (excess pressure) to the tank 15 side, the pipelines 27A and 2B are opened.
The pressure in 7B is controlled to be equal to or lower than the relief set pressure.

A make-up hose 33 connects between the make-up valve 28 and the tank 15. The make-up hose 33 has one end connected to the turning motor 13 by a connector 34 as shown in FIG. The other end is connected to the control valve 20 by a connector 35.

One end of the make-up hose 33 is connected to a connection position 30 between the check valves 28A and 28B as shown in FIG. 2, and is connected to the overload relief valves 31A and 31B through the connection position 30. Also connected between. The other end of the makeup hose 33 is located between the control valve 20 and the oil cooler 19 and is connected to a connection position 36 located in the middle of the drain pipe 18.

The length L of the make-up hose 33 is set based on the following equation (1) based on the speed of sound C in the oil and the frequency F of the pulsation to be reduced.

[0036]

(Equation 1)

For this reason, for example, when the sound speed C in oil is 150
0 m / s, the pulsation frequency F of the hydraulic pump 14 is 23
When the frequency is about 0 Hz, the length L of the makeup hose 33 is about 1.6 m. However, the length L of the make-up hose 33 is not limited to the length L of Formula 1, and the lengths of the connectors 34 and 35 and the valve bodies 28A1 and 2 of the check valves 28A and 28B are determined from the connection position 30.
8B1, the length of the oil passage 29 from the connection position 30 to the valve body of the overload relief valves 31A and 31B, and the length of the oil passage 32 from the connector 34 to the connection position 36 in the control valve 20. Considering the length of the pipeline, etc., it is slightly larger (for example, about 10 cm) than the length L shown in Equation 1.
It may be set short.

The make-up valve 28, which is one end of the make-up hose 33, is always connected to the check valve 28.
A, 28B and overload relief valves 31A, 31
Since B is closed, it is a closed end. On the other hand, the control valve 20 side, which is the other end side of the makeup hose 33,
It is always open in the drain pipe 18. For this reason, the make-up hose 33 is always used as a tail hose that reduces the pulsation of the pressure oil propagating in the drain pipe 18.

On the other hand, when the inside of the pipelines 27A and 27B on the input port side of the swing motor 13 is in a negative pressure state due to idling of the swing motor 13, the check valves 28A and 28B are opened. Swing motor 1
3 is used as an oil passage for supplying hydraulic oil.

The pipes 27A, 27 of the swing motor 13
When an excess pressure equal to or higher than the set relief pressure is generated in B, the overload relief valves 31A and 31B are opened, so that the makeup hose 33 discharges the pressure oil in the pipe lines 27A and 27B to the tank 15 side. Used as a passage.

The hydraulic drive system for a hydraulic shovel according to the present embodiment has the above-described configuration. Next, the operation of the hydraulic drive system will be described.

First, when the hydraulic excavator is moved at the work site, the driver operates an operation lever (not shown) or the like to switch the traveling switching valve 25 from the neutral position to the switching position, thereby obtaining the traveling hydraulic excavator. Hydraulic pump 1 for motor 26
4, the lower traveling body 1 is driven to travel. Further, when performing excavation work such as earth and sand at the work site, the driver uses the operation lever to switch the boom switching valve 22,
The switching valve 23 for the arm and the switching valve 24 for the bucket are switched to supply and discharge pressure oil to the boom cylinder 10 and the like, and the working device 6 is raised and lowered.

Further, when the upper revolving unit 2 is turned, the driver switches the turning switching valve 21 with the operation lever, supplies pressure oil to the turning motor 13, and turns the turning device 3.
Is operated, and the upper swing body 2 is swung.

Here, the pressure oil discharged from the hydraulic pump 14 fluctuates due to the reciprocation of the piston of the hydraulic pump 14 and the like, and pulsation of the pressure oil occurs. Such pulsation of the pressure oil passes through the center bypass line 16 and propagates to the control valve 20. When all the switching valves 21 to 25 are in the neutral position, the pulsation of the pressure oil
, And propagates to the drain pipe 18 and to the tank 15 via the oil cooler 19.

When the swing switching valve 21 is switched to the switching position and the swing motor 13 is driven to rotate, the hydraulic oil from the hydraulic pump 14 is supplied to the swing motor 13.
The piston of the turning motor 13 is reciprocated. For this reason,
The pressure oil discharged from the turning motor 13 is
With the reciprocating motion of the piston, for example, a pulsation of substantially the same cycle as the pulsation of the pressure oil by the hydraulic pump 14 is generated, and the pulsation of the pressure oil by the swing motor 13 is generated by the drain pipe 18.
Propagate into

When the traveling switching valve 25 is operated to the switching position, the pulsation of the pressure oil is generated by the piston of the traveling hydraulic motor 26 in the same manner as when the turning switching valve 21 is operated. This pulsation propagates to the drain pipe 18 and the like.

When the boom switching valve 22 is switched to the switching position and the hydraulic oil from the hydraulic pump 14 is supplied to the boom cylinder 10, the pulsation of the hydraulic oil by the hydraulic pump 14 is transmitted from the center bypass line 16 to the boom. Cylinder 10
And vibrates the piston of the boom cylinder 10. For this reason, the pulsation of the hydraulic oil discharged from the boom cylinder 10 due to the vibration of the piston of the boom cylinder 10 also generates a pulsation having substantially the same cycle as the pulsation of the hydraulic oil discharged from the hydraulic pump 14. It propagates through the drain pipe 18 to the oil cooler 19 and the tank 15.

When the arm switching valve 23 and the bucket switching valve 24 are operated to the switching positions, the pulsation of the hydraulic oil by the hydraulic pump 14 is substantially the same as when the boom switching valve 22 is operated. Periodic pulsation is drain line 18
Propagate inside.

As described above, the pulsation of the pressure oil that has propagated to the drain line 18 enters the makeup hose 33. Here, since the check valves 28A and 28B and the overload relief valves 31A and 31B are always closed, the pulsation of the pressure oil which has entered the makeup hose 33 is caused by the valve bodies 28A1 and 28B1 of the check valves 28A and 28B. And reflected by the valve bodies of the overload relief valves 31A and 31B and merge into the drain pipe 18.

At this time, since the length dimension L of the makeup hose 33 is set so as to satisfy the relationship of Equation 1, the pulsation of the pressure oil reflected by the check valves 28A and 28B and the like and the hydraulic pump 14 side The phase with the pulsation of the propagating oil will differ by 180 degrees. For this reason, in the drain line 18, the pulsation of the pressure oil reflected by the check valves 28A and 28B and the pulsation of the pressure oil propagating from the hydraulic pump 14 side interfere with each other, canceling each other's pulsation. Oil pulsations are damped.

When the boom cylinder 10, the arm cylinder 11, and the bucket cylinder 12 are operated, the pulsation of the pressure oil reflected by the check valves 28A, 28B and the like is caused by the drain pipe 18, the piston of the bucket cylinder 12, and the center. Since the light propagates in the opposite direction toward the hydraulic pump 14 via the bypass pipe 16 and the like, the pulsation of the pressure oil is reduced also on the upstream side of the center bypass pipe 16.

Further, when the swing motor 13 and the traveling hydraulic motor 26 are operated, the check valve 28
The pulsation of the pressure oil reflected by A, 28B and the like propagates toward the hydraulic pump 14 via the drain line 18, the piston of the swing motor 13, the center bypass line 16, and the like. The pulsation of the pressure oil is also reduced on the upstream side of the path 16.

On the other hand, when the swing switching valve 21 is returned from the switching position to the neutral position while the swing motor 13 is rotating, the swing motor 13 cannot be stopped suddenly and continues to rotate by inertia. At this time, for example, the pipe 27A side becomes high pressure as the output port side of the swing motor 13 and
The pipeline 27B side as the input port side of the swing motor 13 is in a negative pressure state. Therefore, the overload relief valve 3
1A is opened, the pressure oil in the pipe 27A is discharged to the tank 15 through the make-up hose 33, and the valve body 28B1 of the check valve 28B is switched to the open position against the spring 28B2. The hydraulic oil on the tank 15 side is supplied to the pipe 27B side of the turning motor 13 via the makeup hose 33.

When the pressure on the pipe 27B as the output port of the swing motor 13 becomes high, the pressure on the pipe 27A as the input port of the swing motor 13 becomes negative. The load relief valve 31B is opened, and the pressure oil in the pipeline 27B is discharged to the tank 15 via the makeup hose 33, and
The valve body 28A1 of the check valve 28A is switched to the valve open position against the spring 28A2, and the hydraulic oil on the tank 15 side is supplied via the make-up hose 33 to the line 27A of the swing motor 13.
Supply to the side.

As a result, the overload relief valve 31
A and 31B suppress the output port side of the swing motor 13 from being in an excessive pressure state, and check the check valves 28A and 28B.
B suppresses a negative pressure state on the input port side of the swing motor 13 to prevent the cavitation from occurring on the input port side of the swing motor 13 and quickly stops the swing motor 13.

Here, when the check valves 28A, 28B and the overload relief valves 31A, 31B are open, the pulsation of the pressure oil propagating in the drain line 18 enters the makeup hose 33 even if it enters. , Check valve 28A,
Reflection by the valve bodies 28A1, 28B1 of 28B and the valve bodies of the overload relief valves 31A, 31B is eliminated. Therefore, when the check valves 28A and 28B and the overload relief valves 31A and 31B are opened, the pulsation of the pressure oil propagating in the center bypass pipe 16 is not reduced.

However, when the check valves 28A and 28B and the overload relief valves 31A and 31B are opened, the turning motor 13 is rotating by inertia without receiving the supply of the pressure oil. 28
B, the fluctuation width of the pressure generated in the center bypass line 16 and the drain line 18 when the overload relief valves 31A and 31B are open is relatively small. Therefore, even if the pulsation of the pressure oil at this time is not reduced, noise and vibration due to the pulsation of the pressure oil are relatively small.

On the other hand, when a large load is applied to the swing motor 13 or when a large load is applied to the traveling hydraulic motor 26, the boom cylinder 10, the arm cylinder 11, and the bucket cylinder 12, the check valve 28A,
28B, since the overload relief valves 31A and 31B are closed, the pulsation of the pressure oil that has entered the makeup hose 33 is checked by the valve bodies 28A1 and 28A of the check valves 28A and 28B.
28B1 and the valve body of the overload relief valves 31A and 31B can surely reflect the light.
8. The pulsation of the pressure oil propagating in the center bypass pipe 16 can be reduced.

Thus, when the fluctuation range of the pressure is large and the noise and vibration increase due to the pulsation of the pressure oil, the pulsation of the pressure oil propagating in the drain line 18 and the center bypass line 16 can be reduced. The noise and vibration based on the pulsation can be attenuated.

Thus, according to the present embodiment, the make-up hose 33 that connects the make-up valve 28 and the tank 15 always causes the pulsation of the pressure oil propagating in the drain pipe 18 and the center bypass pipe 16. Since it is used as a tail hose to reduce the pressure and when the input port side of the swing motor 13 is in a negative pressure state, it is used as an oil passage for replenishing hydraulic oil from the tank 15 toward the input port side of the swing motor 13. When the fluctuation range of the pressure is large and the noise and vibration increase due to the pulsation of the pressure oil, the drain line 18
The pulsation of the pressure oil propagating in the center bypass pipe line 16 can be reduced, and noise and vibration due to the pulsation of the pressure oil can be attenuated.

On the other hand, when the input port side of the swing motor 13 is in a negative pressure state, the fluctuation range of the pressure is small and the noise and vibration due to the pulsation of the pressure oil are small. Therefore, the pulsation of the pressure oil is not reduced. The up hose 33 is used as an oil passage for supplying hydraulic oil in the tank 15 to the input port side of the swing motor 13. This can prevent cavitation from occurring on the input port side of the swing motor 13.

Since the makeup hose 33 is always used as a tail hose and used as an oil passage when the input port side of the swing motor 13 is in a negative pressure state,
There is no need to connect a separate tail hose to the center bypass line 16 located on the discharge side of the hydraulic pump 14, so that production costs can be reduced and it is necessary to secure a space for accommodating the separately provided tail hose. Therefore, the size of the hydraulic shovel can be reduced.

One end of the make-up hose 33 is connected between the check valves 28A and 28B, and the other end is located between the switching valve 21 and the tank 15 downstream of the center bypass line 16. Check valve 28
When the valves A and 28B are closed, the check valve 28
The pulsation of the pressure oil that has entered the make-up hose 33 can be reflected by the valve bodies 28A1 and 28B1 of the valves A and 28B, and the pulsation of the pressure oil that propagates in the center bypass line 16 can be reduced. Is open, the working oil in the tank 15 can be supplied to the input port side of the turning motor 13 using the makeup hose 33.

Further, since the length L of the makeup hose 33 is set based on the equation (1) using the frequency F of the pulsation of the pressure oil by the hydraulic pump 14, the makeup hose 33 enters the makeup hose 33, and The pulsation reflected on the 28 side and the pulsation of the pressure oil by the hydraulic pump 14 interfere with each other, so that the pulsation of the pressure oil in the drain line 18 and the center bypass line 16 can be reduced.

Next, FIG. 6 shows a second embodiment of the present invention. The feature of the hydraulic drive device according to the present embodiment is that when excessive pressure is generated in one of the pipes 27A and 27B, the other is driven. The configuration is such that pressure oil is discharged to the pipelines 27B and 27A. Note that, in the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 41 denotes a make-up valve provided integrally with the turning motor 13, and the make-up valve 41 is provided by check valves 41A and 41B similar to the check valves 28A and 28B according to the first embodiment. The check valves 41A and 41B are provided in the middle of an oil path 42 connecting the pipes 27A and 27B, and are connected in reverse. One end of the makeup hose 33 is connected to a connection position 43 of the oil passage 42 located between the check valves 41A and 41B.

The numeral 44 is provided integrally with the turning motor 13,
A brake valve connected in parallel to the lines 27A and 27B together with the make-up valve 41. The brake valve 44 is composed of a pair of overload relief valves 44A and 44B, and the overload relief valves 44A and 44B are connected to the lines 27A and 27B. 2
It is connected in the middle of each of oil paths 45A and 45B connecting between 7B.

When the pressure in the line 27A becomes excessive pressure equal to or higher than the set relief pressure, the overload relief valve 44A opens, and the pressure oil in the line 27A
It is discharged to the B side. On the other hand, when the pressure in the pipe 27B becomes excessive pressure equal to or higher than the relief set pressure, the overload relief valve 44B is opened, and the pressure oil in the pipe 27B is discharged to the pipe 27A side.

Thus, in the present embodiment configured as described above, the same operation and effect as those of the first embodiment can be obtained. In particular, in the present embodiment, the makeup hose 33 and the brake valve are provided. 44, and when the brake valve 44 generates excessive pressure in one of the lines 27A, 27B by the brake valve 44, the hydraulic oil is discharged to the other lines 27B, 27A, so that the overload relief valves 44A, 4
Check valve 41A, 41B regardless of opening and closing of 4B
While the valve is closed, the pulsation of the pressure oil propagating in the drain line 18 can be reduced.

For this reason, since the check valves 41A and 41B are opened only when the input port side of the swing motor 13 is in a negative pressure state, for example, the discharge pressure from the hydraulic pump 14 changes, and the pipes 27A and 27B Even when excessive pressure is generated, pulsation can be reduced by the makeup hose 33, and the frequency of using the makeup hose 33 as a tail hose can be increased.

In each of the above embodiments, the case where the hydraulic drive device is applied to a hydraulic excavator has been described as an example. However, the present invention is not limited to this, and the present invention is applied to a swing type construction machine such as a hydraulic crane. Is also widely applicable.

[0072]

As described above in detail, according to the first aspect of the present invention, the make-up hose connecting the make-up valve and the tank is always used as a tail hose for reducing the pulsation of the pressure oil by the hydraulic pressure source. When the input port side of the swing motor is in a negative pressure state, it is used as an oil passage for replenishing hydraulic oil from the tank, so that the pressure fluctuation width is large and noise and vibration increase due to pulsation of the pressure oil. In addition, the pulsation of the pressure oil due to the hydraulic source can be reduced, and noise and vibration due to the pulsation of the pressure oil can be attenuated.

On the other hand, when the input port side of the swing motor is in a negative pressure state, the fluctuation range of the pressure is small and the noise and vibration due to the pulsation of the pressure oil are small. The up hose is used as an oil passage for supplying hydraulic oil from the tank to the input port side of the swing motor. This can prevent cavitation from occurring on the input port side of the swing motor.

Since the makeup hose is always used as a tail hose and used as an oil passage when the input port side of the swing motor is in a negative pressure state, it is necessary to connect a tail hose separately to the discharge side of the hydraulic power source. Therefore, the production cost can be reduced, and it is not necessary to secure a space for accommodating a separately provided tail hose, so that the construction machine can be downsized.

According to the second aspect of the present invention, one end of the makeup hose is connected between a pair of check valves,
The other end is connected to the drain line between the directional control valve and the tank, so when the check valve is closed, the check valve reflects the pulsation of pressure oil that has entered the makeup hose, The pulsation of the pressure oil by the hydraulic pressure source can be reduced through the passage, and when the check valve is open, the hydraulic oil in the tank can be supplied to the turning motor using the hose.

According to the third aspect of the present invention, since the length of the makeup hose is set in accordance with the frequency of the pulsation of the pressure oil by the hydraulic pressure source, the makeup hose enters the makeup hose and is closed on the makeup valve side. Interference between the reflected pulsation and the pulsation of the pressure oil by the hydraulic pressure source can attenuate the pulsation of the pressure oil in the drain pipe, thereby reducing the vibration and noise due to the pulsation of the pressure oil.

[Brief description of the drawings]

FIG. 1 is an external view showing a hydraulic shovel to which a hydraulic drive device according to a first embodiment of the present invention is applied.

FIG. 2 is a hydraulic circuit diagram showing the hydraulic drive device according to the first embodiment.

FIG. 3 is a hydraulic circuit diagram showing a swing motor, a makeup valve, a brake valve, and the like in FIG. 2;

FIG. 4 is a sectional view showing a check valve according to the first embodiment.

FIG. 5 illustrates a swing motor, a control valve, and a control valve according to the first embodiment.
FIG. 3 is an exploded perspective view showing a makeup hose and the like.

FIG. 6 is a hydraulic circuit diagram showing a swing motor, a makeup valve, a brake valve, and the like according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper revolving superstructure 13 Swing motor 14 Hydraulic pump 15 Tank 18 Drain pipe 20 Control valve 21 Swivel switching valve (Direction control valve) 27A, 27B Pipe (oil path) 28, 41 Make-up valve 28A, 28B, 41A, 41B Check valve 31, 44 Brake valve 31A, 31B, 44A, 44B Overload relief valve 33 Makeup hose

Claims (3)

[Claims] 1. A lower traveling structure, an upper revolving structure pivotally mounted on the lower traveling structure, and a pivotably supported upper revolving structure provided between the upper revolving structure and the lower traveling structure. A swing device, a swing motor that swings and drives the swing device,
A directional control valve provided in the middle of a pair of oil passages connecting the slewing motor and a hydraulic pressure source, for controlling supply and discharge of pressure oil to the slewing motor; and a directional control valve provided between the directional control valve and the slewing motor. ,
A hydraulic drive device for a construction machine comprising a make-up valve for replenishing hydraulic oil from a tank when an input port side of the swing motor is in a negative pressure state, wherein a make-up hose for connecting between the make-up valve and the tank. Is always used as a tail hose to reduce the pulsation of pressure oil by the hydraulic source, and is used as an oil passage to replenish hydraulic oil when the input port side of the swing motor is in a negative pressure state. Hydraulic drive for construction machinery. 2. The makeup valve includes a pair of check valves provided between the pair of oil passages and opened only when the input port side of the swing motor is in a negative pressure state. The hydraulic drive device for a construction machine according to claim 1, wherein one end of the hose is connected between the check valves, and the other end is connected to a drain line between the directional control valve and the tank. 3. The hydraulic drive device for a construction machine according to claim 1, wherein a length dimension of the makeup hose is set according to a frequency of pulsation of the pressure oil to be reduced.