JPH10195933A - Hydraulic driving device of construction machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure straight forwarding efficiency of traveling in case of composite controls of traveling with boom and enhance the traveling stability or controllability. SOLUTION: Part of pressure oil supplied to a right traveling selector valve 32 side from a hydraulic pump 25 and part of pressure oil supplied to a left traveling selector valve 47 side are combined in a bypass passage 55 and are supplied to an input port 33A of a boom selector valve 33, and flow of pressure oil flowing in the bypass passage 55 is controlled with throttle sections 56, 57 and 58. By the constitution, for example, even in the case composite operation such as an elevation motion of a boom is made while causing a miniaturized hydraulic shovel to travel, the flow of the pressure oil supplied to a right side traveling motor 22 and a left side traveling motor 23 from the hydraulic pumps 25 and 26 can be made approximately equal to pressure, and straight forwarding efficiency in case of composite controls can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive for a construction machine which is suitably used for driving various hydraulic actuators mounted on a construction machine such as a hydraulic shovel.

[0002]

2. Description of the Related Art Generally, a small hydraulic excavator used for excavation work at a relatively narrow work site has crawler tracks on both the left and right sides as disclosed in, for example, Japanese Utility Model Laid-Open No. 3-9989. A lower traveling body and an upper revolving body that is pivotally mounted on the lower traveling body. A working device including a boom, an arm, a bucket, and the like is provided at the front of the upper revolving body so as to be capable of elevating. A blade (discharge plate) is provided on the front side of the traveling body so as to be able to move up and down. Then, the hydraulic excavator performs excavation work such as earth and sand by raising and lowering the working device, and also performs earth removal work such as discharge of excavated earth and sand and leveling by moving forward and backward while raising and lowering the blade. Has become.

Here, the above-mentioned conventional hydraulic shovel includes left and right traveling motors for driving left and right crawler belts provided on a lower traveling body, a rotating motor for rotating an upper rotating body, and a boom for driving a boom. Hydraulic actuators such as a cylinder, an arm cylinder that drives an arm, a bucket cylinder that drives a bucket, and a blade cylinder that drives a blade up and down, and serves as a hydraulic source for each of these hydraulic actuators to discharge hydraulic oil in the tank as pressure oil. A hydraulic drive device including first and second hydraulic pumps and a plurality of switching valves for controlling supply and discharge of hydraulic oil discharged from each hydraulic pump to each hydraulic actuator is provided.

In this type of hydraulic drive device, for example, the right traveling motor, a boom cylinder, a bucket cylinder, and the like are driven by the hydraulic oil discharged from the first hydraulic pump, and the second hydraulic pump is driven. The first and second hydraulic circuits are configured to drive, for example, a left traveling motor, a turning motor, an arm cylinder, and the like by the hydraulic oil discharged from the hydraulic cylinder.

In the above-described hydraulic drive device, a part of the pressure oil supplied to the right traveling motor from the first hydraulic pump and a portion of the pressure oil supplied to the left traveling motor from the second hydraulic pump are used. The blade is moved up and down by joining a part thereof and supplying the combined pressure oil to the blade cylinder. Even when the hydraulic excavator performs a composite operation of raising and lowering the blade while moving the hydraulic excavator forward or backward during the discharging operation, the hydraulic oil can be supplied to the left and right traveling motors almost uniformly, and the discharging operation is performed. The straightness of the hydraulic excavator (vehicle) during operation is ensured.

[0006]

In the prior art described above, for example, when a small hydraulic excavator is loaded on a trailer or the like and transported to a work site, a strong tread plate is provided between the trailer carrier and the ground. In some cases, a hydraulic excavator may be loaded on a bed of a trailer by running the hydraulic excavator on the footboard diagonally and running the hydraulic excavator on the tread plate. In such a case, in order to prevent the working device of the excavator from colliding or interfering with an obstacle such as a tread plate, for example, a combined operation of elevating the boom while running the excavator on the tread plate is performed. To do.

However, in the conventional hydraulic drive device, since the right traveling motor and the boom cylinder are connected in parallel to the first hydraulic pump, the boom is raised while the hydraulic shovel is traveling. When the combined operation is performed such that the pressure oil is supplied from the first hydraulic pump to the boom cylinder, the amount of pressure oil supplied to the right traveling motor is reduced by the amount of pressure oil supplied to the boom cylinder. The pressure difference between the driving oil supplied to the traveling motor and the driving oil supplied to the left traveling motor causes a pressure difference, which makes it difficult to secure the straightness of the excavator. is there.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to ensure the straight traveling performance even in a combined operation in which the traveling operation of the construction machine and the raising operation of the boom are simultaneously performed, It is an object of the present invention to provide a hydraulic drive device for a construction machine capable of improving operability and stability during traveling.

[0009]

In order to solve the above-mentioned problems, the present invention has at least first and second hydraulic pumps, and at least a first hydraulic pump is provided at a discharge side of the first hydraulic pump. A first hydraulic circuit including a traveling switching valve and a boom switching valve is provided, and a second hydraulic circuit including at least a second traveling switching valve is provided on the discharge side of the second hydraulic pump. It is applied to a hydraulic drive device of a construction machine provided.

The first aspect of the present invention is characterized in that, on the first hydraulic circuit side, the boom switching valve is tandemly connected to a position downstream of the first traveling switching valve. The input port of the boom switching valve is connected to the discharge side of the first hydraulic pump at a position upstream of the first travel switching valve, and is connected to the second hydraulic pump. A bypass passage connected to the discharge side is provided, and the bypass passage compensates for the pressure of hydraulic oil supplied from the first and second hydraulic pumps to the first and second travel switching valves. Therefore, a flow rate restricting means for restricting the flow rate of the pressure oil flowing in the bypass passage is provided.

According to the above configuration, for example, even when performing a combined operation of raising and lowering the boom while running the construction machine, the first and second hydraulic pumps are switched from the first and second hydraulic pumps. A part of the pressure oil supplied to the valve side can be almost equally divided and supplied from the bypass passage to the input port of the boom switching valve, and the boom actuator can be reliably driven by the pressure oil from inside the bypass passage. Pressurized oil from the first and second hydraulic pumps can be supplied to the first and second travel actuators at substantially equal flow rates, and travel straightness during combined operation can be ensured.

The flow rate of the pressure oil flowing in the bypass passage is restricted by the flow rate restricting means.
, The hydraulic oil from the first and second hydraulic pumps can be supplied with priority over the boom switching valve, for example, to compensate for the driving pressure for traveling to the left and right traveling motors. In addition, it is possible to maintain good running performance during combined operation.

[0013] Further, by connecting the boom switching valve to a position downstream of the first traveling switching valve in tandem,
For example, when operating the boom alone, the pressure oil discharged from the first hydraulic pump can be supplied from the boom switching valve to the boom actuator without passing through the bypass passage, and the operability and operability of the boom can be improved. Can be kept good.

Further, in the invention of claim 2, the bypass passage has a first bypass passage portion connected at one end to a discharge side of the first hydraulic pump, and a discharge passage formed at one end of the second hydraulic pump. Side, and one end is connected to the other end of the first and second bypass passages so that the pressure oils from the first and second bypass passages merge with each other. And a third bypass passage connected to the input port of the boom switching valve.

According to the above configuration, at the time of the combined operation of the traveling and the boom, a part of the hydraulic oil from the first hydraulic pump and a part of the hydraulic oil from the second hydraulic pump are supplied to the first and second hydraulic pumps. While being joined at the other end of the bypass passage section, the supply port can be supplied to the input port of the boom switching valve via the third bypass passage, and the first and second hydraulic actuators are supplied to the first and second travel actuators. The pressure oil from the pump can be continuously supplied at a substantially equal flow rate.

Further, in the invention according to claim 3, the flow rate restricting means is provided in the first bypass passage portion, and
First restricts the flow rate of the pressure oil flowing in the bypass passage section
A second throttle portion provided in the second bypass passage portion for limiting a flow rate of the pressure oil flowing in the second bypass passage portion; and a second throttle portion provided in the third bypass passage portion. And a third restrictor for restricting the flow rate of the hydraulic oil flowing in the bypass passage of No. 3 which is connected to the input port side of the boom switching valve via the third bypass passage. The flow rate of the supplied pressure oil is limited to be larger than that of the first and second throttle portions.

According to the above configuration, for example, the first bypass passage portion and the second bypass passage portion have different lengths (pipe lengths), so that the first bypass portion is limited by the first throttle portion.
Even if a difference occurs between the flow rate of the pressure oil in the bypass passage portion and the flow rate of the pressure oil in the second bypass passage portion limited by the second throttle portion, the third oil passage provided in the third bypass passage portion The pressure difference generated between the first and second bypass passages can be reliably reduced by greatly restricting the flow rate of the pressure oil at the third throttle portion. By the first and second throttle portions, the driving pressure for traveling can be supplied to the first and second traveling switching valves at substantially the same pressure, and the left and right traveling can be performed during the combined operation of traveling and boom. The motor can be driven with priority.

Further, in the invention of claim 4, the first bypass passage allows pressure oil to flow from the first hydraulic pump toward the second and third bypass passages, and reverses the flow. A first check valve for preventing a flow in the direction is provided, and pressure oil flows from the second hydraulic pump toward the first and third bypass passages in the second bypass passage. And a second check valve for preventing reverse flow is provided.

According to the above configuration, the pressure oil from the first hydraulic pump flowing to the second and third bypass passages through the first bypass passage flows back through the first bypass passage. This can be prevented by the first check valve, and the actuator driven by the pressure oil from the first hydraulic pump can be operated properly. Also, the second reverse flow of the hydraulic oil from the second hydraulic pump flowing to the first and third bypass passages through the second bypass passage is performed in a second reverse direction. This can be prevented by the stop valve, and the actuator driven by the pressure oil from the second hydraulic pump can be operated properly.

On the other hand, a feature of the configuration adopted by the invention of claim 5 is that, on the first hydraulic circuit side, the boom switching valve is connected in tandem to a position downstream of the first traveling switching valve. An input port of the boom switching valve, a first bypass passage connected to a discharge side of the first hydraulic pump at a position upstream of the first travel switching valve;
A second bypass passage connected to a discharge side of the second hydraulic pump, wherein the first and second bypass passages are provided with the first and second hydraulic pumps from the first and second hydraulic pumps; In order to compensate for the pressure of the pressure oil supplied to the traveling switching valve side, first and second flow rate limiting means for respectively limiting the flow rate of the pressure oil flowing in each of the bypass passages are provided.

According to the above configuration, for example, even when performing a combined operation such as raising and lowering the boom while running the construction machine, the first and second hydraulic pumps are switched from the first and second hydraulic pumps. A part of the pressure oil supplied to the valve side can be almost equally divided and supplied from the first and second bypass passages to the input port of the boom switching valve. The boom actuator can be reliably driven by the pressurized oil, and the pressurized oil from the first and second hydraulic pumps can be supplied to the first and second travel actuators at substantially the same flow rate. Straightness can be ensured.

The flow rate of the pressure oil flowing in the first and second bypass passages is limited by the first and second flow rate limiting means. , The hydraulic oil from the first and second hydraulic pumps can be supplied with a higher priority than the boom switching valve. For example, the traveling drive pressure for the left and right traveling motors is compensated, and the traveling performance during combined operation is improved. Can be kept good.

Further, according to the invention of claim 6, the first bypass passage allows the pressure oil to flow from the first hydraulic pump toward the input port side of the boom switching valve, and allows the oil to flow in the opposite direction. A first check valve for preventing flow is provided, and the second bypass passage is configured to allow pressure oil to flow from the second hydraulic pump toward an input port side of the boom switching valve, and to be in the reverse direction. In that a second check valve for preventing the flow of air is provided.

According to the above configuration, the pressure oil from the first hydraulic pump, which has flowed to the second bypass passage via the first bypass passage, flows backward through the first bypass passage. Of the second hydraulic pump that flows toward the first bypass passage via the second bypass passage and flows back through the second bypass passage. Can be prevented by the check valve. Thereby, the actuator driven by the pressure oil from the first hydraulic pump and the actuator driven by the pressure oil from the second hydraulic pump can be operated properly.

[0025]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. In this embodiment, a small hydraulic excavator is shown as an example of a construction machine.

In the drawing, reference numeral 1 denotes a lower traveling body, and the lower traveling body 1 has crawler tracks 1A, 1A on both the left and right sides. Numeral 2 denotes an upper revolving structure mounted on the lower traveling structure 1 so as to be revolvable. The upper revolving structure 2 has a revolving frame 3, and a hydraulic pump 2 described later is provided on the rear side of the revolving frame 3.
There is provided a machine room 4 in which the motors 5, 26 and the prime mover 27 are stored. A driver's seat 5 on which a driver of the hydraulic shovel sits is provided on the upper side of the machine room 4, and a lever stand 6 is provided upright from the revolving frame 3 in front of the driver's seat 5.

As shown in FIG. 2, a pair of left and right operation levers 7, 7 are provided on the lever stand 6, and the driver tilts each operation lever 7 forward, rearward, left, and right. Then, the boom 13, the arm 14 and the bucket 15, which will be described later, are operated, and the upper swing body 2 is moved to the lower traveling body 1.
It is turned on. In addition, between each operation lever 7, the left,
A pair of right and left traveling levers 8 and 8 are provided. Each of the traveling levers 8 is linked with a pair of left and right traveling pedals (not shown), and the driver tilts each traveling lever 8 forward and backward. When operated or when each travel pedal is depressed, each crawler belt 1A of the lower traveling body 1 is driven to rotate, and the traveling operation is performed so that the hydraulic shovel moves forward or backward.

Reference numeral 9 denotes a support bracket integrally formed on the front portion of the revolving frame 3, and reference numeral 10 denotes a working device attached to the upper revolving unit 2 via the supporting bracket 9.
0 is the vertical axis 1 on the support bracket 9 on the revolving frame 3 side.
A swing bracket 12 is attached to the swing bracket 12 so as to be rotatable in the left and right directions, a boom 13 is attached to the swing bracket 12 so as to be able to move up and down, and a swing bracket is attached to the tip end of the boom 13. An arm 14 and a bucket 15 rotatably attached to the distal end of the arm 14 are provided.

Here, in the working device 10, the swing bracket 12 is horizontally rotated in the left and right direction by the swing cylinder 16, and the boom 13 is raised and lowered with respect to the swing bracket 12 by the boom cylinder 17. The arm 14 is rotated by an arm cylinder 18, and the bucket 15 is rotated by a bucket cylinder 19. During excavation work such as earth and sand, the boom 13 and the arm 14 are raised and lowered while the bucket 15 is moved.
Is rotated to excavate earth and sand on the tip side of the bucket 15.

Reference numeral 20 denotes a blade (discharge plate) provided on the lower traveling body 1 so as to be movable up and down. The blade 20 is formed as a plate-like body extending in the width direction of the lower traveling body 1. The hydraulic excavator is moved up and down by a blade cylinder 21 provided between the excavator 1 and the ground excavator to perform earth discharging work such as earth and sand during traveling of the hydraulic excavator.

Next, FIGS. 3 and 4 show a hydraulic drive device according to this embodiment.

In the drawing, reference numerals 22 and 23 denote right and left traveling motors provided on the lower traveling body 1, respectively. The traveling motors 22 and 23 are supplied with hydraulic oil from hydraulic pumps 25 and 26, respectively. , Each track 1A of the undercarriage 1
To drive the hydraulic shovel. Reference numeral 24 denotes a swing motor provided between the lower running body 1 and the upper swing body 2. The swing motor 24 moves the upper swing body 2 above the lower running body 1 by supplying and discharging pressure oil from a hydraulic pump 26. To turn.

Reference numerals 25 and 26 denote first and second hydraulic pumps connected to the output shaft of the prime mover 27, respectively.
5 and 26 are driven by the prime mover 27 to discharge the hydraulic oil in the tank 28 to the first center bypass line 29 and the second center bypass line 30 as pressure oil, respectively.

Reference numeral 31 denotes a first hydraulic circuit provided on the discharge side of the hydraulic pump 25. The hydraulic circuit 31 is connected to a center bypass line 29 and a first traveling line connected through the center bypass line 29. Running switching valve 32, boom switching valve 33, bucket switching valve 3 as switching valves for
4. The switching valve 35 for swing, the preliminary switching valve 36, and the most downstream side of the center bypass line 29
The switching valves 32 to 36 are directional switching valves having 6 ports and 3 positions, respectively. A high-pressure relief valve 38 for setting the pressure in the first hydraulic circuit 31 and a pressure gauge 39 are connected to the most upstream side of the center bypass line 29.

Here, on the hydraulic circuit 31 side, the boom switching valve 33 is tandem-connected to the downstream side of the right traveling switching valve 32 via the center bypass line 29, and the boom switching valve 33 is connected to the input port 33A side. Is provided with a check valve 40 that allows the flow of pressure oil from the hydraulic pump 25 to the input port 33A side and prevents the flow in the opposite direction.
The boom switching valve 33 and the bucket switching valve 34, the swing switching valve 35, and the preliminary switching valve 36 located downstream thereof are branched off from the center bypass line 29 on the upstream side of the boom switching valve 33. They are connected in parallel via a branch passage 41. Further, the right traveling switching valve 32, the boom switching valve 33, the bucket switching valve 34, the swing switching valve 35, and the preliminary switching valve 36 are connected to the tank 28 via a tank passage 37 and the like. .

The right traveling switching valve 32 is connected to the right traveling motor 22 via a pair of main conduits 22A and 22B, and the boom switching valve 33 is connected to the pair of main conduits 17A and 17A.
7B is connected to the boom cylinder 17 and the main pipeline 1
An overload relief valve 42 is provided in the middle of 7B between the tank passage 37 side. The bucket switching valve 34 is connected to the bucket cylinder 19 via a pair of main pipelines 19A and 19B, and the swing switching valve 35 is connected to the swing cylinder 1 via a pair of main pipelines 16A and 16B.
6 and a tank passage 37 in the middle of the main line 16A.
A check valve 43 for preventing backflow is provided between the check valve 43 and the side. In addition, the preliminary switching valve 36 is provided, for example, with a rock drill (breaker) in the working device 10 of the hydraulic shovel instead of the bucket 15.
When an attachment such as the above is attached, it controls the supply and discharge of pressure oil to and from a hydraulic actuator (neither is shown) for driving the attachment.

Reference numeral 44 denotes a second hydraulic circuit provided on the discharge side of the hydraulic pump 26. The hydraulic circuit 44 includes a center bypass line 30 and a switching valve for turning connected via the center bypass line 30. 45, arm switching valve 4
6, a left traveling switching valve 47 as a second traveling switching valve,
It is configured to include a blade switching valve 48, a tank passage 37 connected to the most downstream side of the center bypass line 30, and the like. Each of the switching valves 45 to 48 is a directional switching valve having 6 ports and 3 positions. . A high pressure relief valve 49 for setting the pressure in the hydraulic circuit 44 and a pressure gauge 50 are connected to the most upstream side of the center bypass line 30.

Here, on the hydraulic circuit 44 side, the turning switching valve 45, the arm switching valve 46, the left traveling switching valve 47, and the blade switching valve 48 are provided with a center bypass line upstream of the turning switching valve 45. The connection is made in parallel through a branch passage 51 branched from 30 and connected to the tank 28 through the tank passage 37 and the like.

The turning switching valve 45 is connected to the turning motor 24 via a pair of main lines 24A and 24B. An overload relief valve 52 and a check valve 53 are provided in the main lines 24A and 24B, respectively. It is connected.
The arm switching valve 46 is connected to the pair of main conduits 18A, 18A.
B is connected to the arm cylinder 18 through the main pipeline 18
An overload relief valve 54 is provided in the middle of A. Further, the left traveling switching valve 47 is connected to the pair of main pipelines 23.
A, 23B is connected to the left traveling motor 23,
The blade switching valve 48 is connected to the blade cylinder 21 via a pair of main pipelines 21A and 21B.

Reference numeral 55 denotes a center bypass line 2 which is upstream of the right traveling switching valve 32 and is on the discharge side of the hydraulic pump 25.
9 shows a bypass passage connected to the discharge side of the hydraulic pump 26 at a position of a connection point 59 described later,
One end of the bypass passage 55 is connected to the first bypass passage portion 55 </ b> A connected to the center bypass line 29 on the upstream side of the right travel switching valve 32, and one end is connected to the center bypass line 30 via the branch passage 51. A second bypass passage portion 55C having the other end connected to the other end of the bypass passage portion 55A via a connection point 55B, one end connected to the connection point 55B, and the other end downstream from the check valve 40. And a third bypass passage 55D connected to the input port 33A of the boom switching valve 33 on the side.
In this embodiment, the branch passage 51 is connected to the bypass passage 5.
5C.

Reference numerals 56, 57, 58 denote respective bypass passage portions 55.
A, 55C, and 55D show first, second, and third throttle sections as flow rate limiting means provided in the middle of each of the sections. Then, the throttle section 56 restricts the flow rate of the pressure oil flowing in the bypass passage section 55A, so that the hydraulic pump 2
5 through the right travel switching valve 32 to the right travel motor 2
2 is to compensate for the pressure of the pressure oil supplied to the pump.

The throttle 57 is provided with a bypass passage 55.
It is provided at a position upstream of a connection point 59 between C and the branch passage 51. The throttle portion 57 restricts the flow rate of the pressure oil flowing in the bypass passage portion 55 </ b> C so that the pressure oil supplied from the hydraulic pump 26 to the left traveling motor 23 via the left traveling switching valve 47 is reduced. It compensates for pressure.

Further, the throttle 58 is provided with the bypass passage 5.
The flow rate of the pressure oil supplied to the input port 33A of the boom switching valve 33 through the 5D is restricted to be larger than that of the throttle portions 56 and 57. Accordingly, due to the difference between the passage length of the bypass passage portion 55A and the passage length of the bypass passage portion 55C, the flow rate of the pressure oil in the bypass passage portion 55A limited by the throttle portion 56 Even if there is a difference between the flow rate of the pressurized oil in the restricted bypass passage 55C and the flow rate of the pressurized oil flowing in the bypass passage 55D, the flow restriction of the pressurized oil flowing in the bypass passage 55D is greatly restricted by the restrictor 58, so that the restrictors 56 and 57 are restricted. A pressure difference can be prevented from occurring between the hydraulic pump 25 and the pressure of the hydraulic oil supplied from the hydraulic pump 25 to the right traveling motor 22.
And the pressure of the pressure oil supplied to the traveling motor 23 on the left side of the vehicle can be kept substantially equal.

Reference numeral 60 denotes a check valve as a first check valve provided in the bypass passage portion 55A located in the vicinity of the throttle portion 56. The check valve 60 is connected to the bypass passage portions 55C, 55C from the hydraulic pump 25. This allows the pressure oil to flow to the 55D side and prevents the flow in the opposite direction.

Reference numeral 61 denotes a check valve as a second check valve provided in the bypass passage 55C in the vicinity of the throttle 57, and the check valve 61 is
This allows the pressure oil to flow to the bypass passage portions 55A, 55D side, and prevents the flow in the opposite direction.

The hydraulic drive system of the 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 excavating work such as earth and sand at a work site, the boom cylinder 17 and the arm cylinder 1
8 is expanded and contracted, so that the boom 13 and the arm 1
4 is raised and lowered, the bucket cylinder 19 is expanded and contracted, and the bucket 15 is rotated.
Excavation work such as earth and sand is performed on the tip side of 5.

When performing the trench excavation work, the upper revolving unit 2 is pivoted to the revolving position 2A or 2A shown by a virtual line in FIG.
While turning to B, the entire working device 10 is turned left and right to the horizontal turning position 10A or 10B by the swing cylinder 16 via the swing bracket 12.
Then, the bucket 15 is rotated while raising and lowering the boom 13 and the arm 14 up and down at one of the horizontal rotation positions 10A and 10B, so that a side groove or the like is formed at the tip end side of the bucket 15. Perform excavation work.

Next, when running the hydraulic excavator, the driver tilts each of the traveling levers 8 forward and backward, and
Alternatively, by depressing each traveling pedal, the right traveling switching valve 32 and the left traveling switching valve 47 are switched from the neutral position. Thereby, the pressure oil from the hydraulic pump 25 is supplied to the center bypass line 29 and the right traveling switching valve 3.
2 and the like, and the hydraulic oil from the hydraulic pump 26 is supplied to the left traveling motor 23 via the center bypass line 30, the branch passage 51, the left traveling switching valve 47 and the like. Supplied. Then, the traveling motors 22 and 23 drive each crawler belt 1A of the lower traveling body 1 to perform a traveling operation such that the hydraulic shovel moves forward or backward.

At this time, part of the pressure oil discharged from the hydraulic pump 25 is introduced into the bypass passage 55A, and part of the pressure oil discharged from the hydraulic motor 26 is introduced into the bypass passage 55C. It merges between the check valves 60 and 61. Then, in order to perform a combined operation of raising and lowering the blade 20 while running the hydraulic excavator, when the driver depresses each traveling pedal and tilts the operating lever for the blade forward and backward, the switching valve 48 for the blade is operated. Is switched from the neutral position.

Thus, the pressure oil in the bypass passage 55 is supplied to the blade cylinder 21 via the blade switching valve 48 connected to the bypass passage portion 55C at the connection point 59, and the blade oil is simultaneously driven by the hydraulic shovel. 20
Perform the lifting operation. In this case, the hydraulic pump 2
A part of the pressure oil discharged from the hydraulic pump 26 and a part of the pressure oil discharged from the hydraulic pump 26 form the bypass passage 55 and the branch passage 51.
Is supplied to the blade cylinder 21 while flowing through the hydraulic pump 25 and the hydraulic oil is supplied to the right traveling motor 22 from the hydraulic pump 25 and supplied to the left traveling motor 23 from the hydraulic pump 26. The flow rate of the pressurized oil can be made substantially equal, and the traveling straightness of the hydraulic shovel during earth removal work can be ensured.

At this time, the bypass passage portions 55A, 55C
By restricting the flow rate of the hydraulic oil flowing through the bypass passages 55A and 55C by the throttle portions 56 and 57 provided in the middle of the hydraulic pump 25, the hydraulic pump 25 is provided to the right traveling motor 22 and the left traveling motor 23. , 26 can be supplied with priority over the blade cylinder 21. This makes it possible to compensate for the driving pressure for traveling with respect to the traveling motors 22 and 23. Even when, for example, the hydraulic excavator performs an earth removal operation while traveling on a slope, the climbing performance of the hydraulic excavator is preferably maintained. can do.

Next, when performing a combined operation of raising and lowering the boom 13 while running the hydraulic excavator, the driver tilts the operation lever 7 while depressing each of the traveling pedals. The switching valve 33 is switched from the neutral position. Thereby, the pressure oil in the bypass passage 55
The hydraulic shovel is supplied to the boom cylinder 17 through the bypass passage 55D and the boom switching valve 33, and the boom 13 performs the raising operation at the same time as the traveling operation of the hydraulic shovel.

Also in this case, a part of the pressure oil from the hydraulic pumps 25 and 26 that have joined through the bypass passage 55 and the branch passage 51 is almost equally divided and is distributed to the boom cylinder 1.
7, the flow rate of the hydraulic oil supplied from the hydraulic pump 25 to the right traveling motor 22 is substantially equal to the flow rate of the hydraulic oil supplied from the hydraulic pump 26 to the left traveling motor 23. And the traveling straightness of the excavator can be ensured.

That is, by restricting the flow rate of the hydraulic oil flowing in each of the bypass passages 55A, 55C by the throttles 56, 57 provided in the middle of the bypass passages 55A, 55C, the right traveling motor 22, Traveling motor 2 on the left
3, the pressure oil from the hydraulic pumps 25 and 26 can be supplied with priority over the boom cylinder 17. As a result, the driving pressure for traveling on the traveling motors 22 and 23 can be compensated, and, for example, the hydraulic excavator can move on a tread plate spanned between the bed of the trailer and the ground to avoid obstacles. Even if you want to move the boom 13 up and down,
The hill climbing performance of the hydraulic shovel can be favorably maintained.

At this time, due to the difference between the passage length of the bypass passage portion 55A and the passage length of the bypass passage portion 55C, the flow rate of the pressure oil in the bypass passage portion 55A limited by the throttle portion 56 Even when there is a difference between the flow rate of the pressure oil in the bypass passage portion 55C limited by the portion 57 and the throttle portion 58 provided in the bypass passage portion 55D, the flow amount of the pressure oil flowing in the bypass passage portion 55D is reduced. Since the restriction is largely made, it is possible to reliably prevent a pressure difference from occurring between the throttle portions 56 and 57. Thereby, the pressure of the hydraulic oil supplied from the hydraulic pump 25 to the right traveling motor 22 and the pressure of the hydraulic oil supplied from the hydraulic pump 26 to the left traveling motor 23 can be kept substantially equal,
The straight traveling performance of the hydraulic shovel can be further improved.

It should be noted that even when a combined operation of raising and lowering the boom 13 and moving the blade 20 up and down while running the hydraulic excavator is performed, the bypass passage 55
Hydraulic pumps 25 and 2 that have joined through the
6 is supplied to the boom cylinder 17 and the blade cylinder 21 by being diverted almost uniformly to the boom cylinder 17 and the blade cylinder 21. The flow rate of the pressure oil supplied from the pump 26 to the left traveling motor 23 can be made substantially equal, and the traveling straightness of the excavator can be ensured.

Further, by restricting the flow rate of the pressure oil flowing through each of the bypass passages 55A, 55C by the throttles 56, 57 provided in the middle of the bypass passages 55A, 55C, the right traveling motor 22, The hydraulic oil from the hydraulic pumps 25 and 26 can be supplied to the left traveling motor 23 with higher priority than the boom cylinder 17 and the blade cylinder 21. This makes it possible to reliably compensate for the driving pressure for traveling with respect to the traveling motors 22 and 23, and to maintain the traveling performance of the hydraulic excavator in a good condition.

On the other hand, when excavation work is performed with the hydraulic excavator stopped, for example, when the boom 13 is raised and lowered independently, the driver switches the operation lever 7 to switch the boom. Only the valve 33 is switched from the neutral position. In this case, the pressure oil from the hydraulic pump 25 is directly supplied to the boom cylinder 17 from the center bypass line 29 via the boom switching valve 33 without flowing to the bypass passage portion 55A side. Thereby, the operability and operating performance of the boom 13 during excavation work can be kept good.

Next, FIG. 5 shows a second embodiment of the present invention. The feature of this embodiment is that the first port connected to the input port of the boom switching valve and the discharge side of the first hydraulic pump is provided. In addition to providing a bypass passage, a second bypass passage connected to the discharge side of the second hydraulic pump is provided. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 5, one end 71 is connected to the center bypass line 29 on the upstream side of the right traveling switching valve 32 and the other end thereof is downstream of the check valve 40 on the input port 33A of the boom switching valve 33. 1 shows a first bypass passage connected to the first bypass passage.

Reference numeral 72 denotes one end connected to the center bypass line 30 via the branch passage 51, and the other end downstream from the check valve 40 at the input port 3 of the boom switching valve 33.
In the present embodiment, the branch passage 51 forms a part of the bypass passage 72 in the second bypass passage connected to 3A.

Reference numeral 73 denotes a restrictor provided in the middle of the bypass passage 71 as first flow restricting means, and 74 denotes a restrictor provided in the middle of the bypass passage 72 as second flow restricting means. I have.

Here, the throttle portion 73 is connected to the bypass passage 71.
By limiting the flow rate of the hydraulic oil flowing through the inside, the pressure of the hydraulic oil supplied from the hydraulic pump 25 to the right traveling motor 22 via the right traveling switching valve 32 is compensated.

The throttle portion 74 is provided at a position upstream of the connection point 59 between the bypass passage 72 and the branch passage 51, and restricts the flow rate of the hydraulic oil flowing in the bypass passage 72, so that the hydraulic pump 26 to left traveling switching valve 47
This compensates for the pressure of the pressure oil supplied to the left traveling motor 23 via the.

Reference numeral 75 denotes a check valve as a first check valve provided in the bypass passage 71 in the vicinity of the throttle portion 73. The check valve 75 moves from the hydraulic pump 25 to the bypass passage 71 side. It allows the pressurized oil to flow and blocks the reverse flow.

Reference numeral 76 denotes a check valve as a second check valve provided in the bypass passage 72 in the vicinity of the throttle portion 74. The check valve 76 is provided from the hydraulic pump 26 to the bypass passage 72 side. It allows the pressurized oil to flow and blocks the reverse flow.

This embodiment has the above-described configuration. For example, when performing a combined operation of raising and lowering the boom 13 while running a hydraulic shovel, the driver operates the operating lever while depressing each traveling pedal. By operating the front and rear wheels 7 forward and backward, the switching valve 32 for right traveling, the switching valve 47 for left traveling, and the switching valve 33 for boom are switched from the neutral position.

Thus, the pressure oil from the hydraulic pump 25 is supplied to the center bypass line 29 and the right traveling switching valve 3.
2 and the like, and the hydraulic oil from the hydraulic pump 26 is supplied to the left traveling motor 23 via the center bypass line 30, the branch passage 51, the left traveling switching valve 47 and the like. The hydraulic shovel is supplied and performs a traveling operation such that the hydraulic shovel moves forward or backward.

At this time, a part of the pressure oil discharged from the hydraulic pump 25 is introduced into the input port 33A side of the boom switching valve 33 via the bypass passage 71, and the pressure oil discharged from the hydraulic pump 26 is discharged. A part is introduced into the input port 33A side of the boom switching valve 33 through the bypass passage 72, and after being joined at the input port 33A side, supplied to the boom cylinder 17 through the boom switching valve 33, and It is compensated that the raising operation of the boom 13 is properly performed at the same time as the traveling operation of the vehicle.

Thus, after a part of the pressure oil from the hydraulic pumps 25 and 26 merges in the bypass passages 71 and 72,
By being almost equally diverted and supplied to the boom cylinder 17, the right traveling motor 22 is
And the flow rate of the pressure oil supplied from the hydraulic pump 26 to the left traveling motor 23 can be made substantially equal, and the traveling straightness of the hydraulic shovel can be improved.

The bypass passages 71 and 72 are provided in the middle of the bypass passages 71 and 72, respectively.
By restricting the flow rate of the pressure oil flowing inside 1,72,
The pressure of the pressure oil supplied to the right traveling motor 22 from the hydraulic pump 25 and the left traveling motor 2 from the hydraulic pump 26
3, the pressure of the hydraulic oil supplied to the hydraulic shovel can be compensated so that the hydraulic shovel can always exhibit proper traveling performance regardless of the combined operation.

In the first embodiment, each of the bypass passage portions 55A, 55C, 55
Although the case where the throttle portions 56, 57 and 58 are provided in the 5D has been described as an example, the present invention is not limited to this. For example, the throttle portion 58 may be provided only in the bypass passage portion 55D.

[0075]

As described above in detail, according to the first aspect of the present invention, a part of the hydraulic oil supplied from the first hydraulic pump to the first traveling switching valve side and the second hydraulic pump And a part of the pressure oil supplied to the second traveling switching valve from the boom switching valve is provided to the input port side of the boom switching valve via the bypass passage. When performing a combined operation such as raising and lowering the boom, a part of the pressure oil from the first and second hydraulic pumps that have joined in the bypass passage is almost equally divided and supplied to the actuator for the boom. it can. Thereby, the boom actuator can be reliably provided, and the flow rates of the pressure oil supplied from the first and second hydraulic pumps to the first and second traveling actuators can be substantially equalized. , The traveling straightness of the vehicle can be ensured, and the operability and stability can be improved.

Further, since the flow rate of the hydraulic oil flowing in the bypass passage is restricted by the flow restriction means provided in the bypass passage, the first and second traveling switching valves are provided with:
The pressure oil supplied from the first and second hydraulic pumps can be supplied with priority over the boom actuator.
The driving pressure for traveling with respect to the right traveling motor can be compensated, and the traveling performance during the combined operation can be kept good.

Further, since the boom switching valve is connected in tandem to a position downstream of the first traveling switching valve, for example, when the boom is operated alone, the boom is discharged from the first hydraulic pump. The pressurized oil can be supplied to the boom actuator through the boom switching valve without passing through the bypass passage, and the operability and operability of the boom can be kept good.

According to the second aspect of the present invention, the bypass passage is connected to the first bypass passage connected to the discharge side of the first hydraulic pump and to the discharge side of the second hydraulic pump. Since the second bypass passage portion and the third bypass passage portion for allowing the hydraulic oil from the first and second bypass passage portions to merge with each other, the first bypass passage portion is connected to the first hydraulic pump. And the pressure oil introduced from the second hydraulic pump into the second bypass passage section,
Can be surely merged in the bypass passage section of the first embodiment.

Further, according to the third aspect of the present invention, the first,
First, second, and third throttle portions are provided in the second and third bypass passage portions, and the third throttle portion is supplied to the input port side of the boom switching valve via the third bypass passage portion. The flow rate of the pressurized oil in the first bypass passage limited by the first throttle is set to be smaller than that of the first and second throttles. Pressure oil is supplied to the input port of the boom switching valve via the third bypass passage even when there is a difference between the flow rate of the pressure oil in the second bypass passage limited by the throttle portion. At times, the flow rate of the pressure oil is greatly limited by the third throttle portion, so that a pressure difference between the first and second bypass passage portions can be prevented from occurring. Thereby, the first,
The driving pressure for traveling supplied from the second hydraulic pump to the first and second traveling switching valves can be made substantially equal, and traveling straightness during combined operation can be further improved.

According to the fourth aspect of the present invention, the pressure oil flowing to the second and third bypass passages through the first bypass passage flows back to the first hydraulic pump. First
The pressure oil, which is blocked by the check valve, flows through the second bypass passage to the first and third bypass passages,
Is prevented by the second check valve from flowing back to the hydraulic pump side, the actuator is driven by pressure oil from the first hydraulic pump, and driven by pressure oil from the second hydraulic pump. The operated actuator can be operated properly.

According to the fifth aspect of the present invention, a part of the pressure oil supplied from the first hydraulic pump to the first travel switching valve side and the second travel pump from the second hydraulic pump are provided. Since a part of the pressure oil supplied to the switching valve side is supplied to the input port of the boom switching valve via the first and second bypass passages, for example, the construction machine is run. When performing a composite operation such as raising and lowering the boom, the first and second merging in the first and second bypass passages are performed.
A part of the pressure oil from the hydraulic pump can be almost equally divided and supplied to the boom actuator. This gives 1,
The flow rates of the pressure oil supplied from the second hydraulic pump to the first and second traveling actuators can be made substantially equal, and the traveling straightness of the construction machine during the combined operation can be ensured.

Further, since the flow rate of the pressure oil flowing through each of the bypass passages is restricted by the first and second flow rate restricting means provided in the first and second bypass passages, for example, the left and right sides are provided. The hydraulic oil supplied from the first and second hydraulic pumps can be supplied to the traveling motor with priority over the boom actuator, and the traveling performance during the combined operation can be kept good.

Further, according to the invention of claim 6, the first check valve provided in the first bypass passage allows the pressure oil flowing to the input port side of the boom switching valve to flow to the first hydraulic pump side. The second check valve provided in the second bypass passage prevents the pressure oil flowing to the input port side of the boom switching valve from flowing back to the second hydraulic pump side. With this configuration, the actuator driven by the pressure oil from the first hydraulic pump and the actuator driven by the pressure oil from the second hydraulic pump can be operated properly.

[Brief description of the drawings]

FIG. 1 is a front view showing a hydraulic excavator equipped with a hydraulic drive device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing the excavator in FIG.

FIG. 3 is a circuit diagram showing a hydraulic drive device according to a first embodiment of the present invention.

FIG. 4 is a circuit configuration diagram showing an enlarged main part in FIG. 3;

FIG. 5 is an enlarged circuit configuration diagram showing a main part of a hydraulic drive device according to a second embodiment of the present invention.

[Explanation of symbols]

 17 Boom cylinder 22 Right traveling motor 23 Left traveling motor 25 First hydraulic pump 26 Second hydraulic pump 31 First hydraulic circuit 32 Right traveling switching valve (first traveling switching valve) 33 Boom switching Valve 33A Input port 44 Second hydraulic circuit 47 Left traveling switching valve (second traveling switching valve) 55 Bypass passage 55A First bypass passage 55C Second bypass passage 55D Third bypass passage 56 1st throttle section (flow rate limiting means) 57 2nd throttle section (flow rate limiting means) 58 3rd throttle section (flow rate limiting means) 60 1st check valve (1st check valve) 61 2nd Check valve (second check valve) 71 First bypass passage 72 Second bypass passage 73 First throttle unit (first flow limiting unit) 74 Second throttle unit (second flow limiting unit) 75 First check valve (first check valve) 76 Second check valve (second check valve)

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Shinichi Sato 650, Kandate-cho, Tsuchiura-shi, Ibaraki Prefecture Within the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. Engineering Co., Ltd. (72) Inventor Hiroshi Iwashita 1828-12-105 Oji, Chiyoda-cho, Niigata-gun, Ibaraki Pref.

Claims (6)

[Claims] 1. A first hydraulic pump having at least a first hydraulic pump and a second hydraulic pump, and a discharge side of the first hydraulic pump including at least a first travel switching valve and a boom switching valve. A circuit is provided, and on the discharge side of the second hydraulic pump,
In a hydraulic drive system for a construction machine provided with a second hydraulic circuit including at least a second traveling switching valve, the boom switching valve is connected to the first traveling circuit on the first hydraulic circuit side. A tandem connection is provided at a position downstream of the valve, and an input port of the boom switching valve is connected to a discharge side of the first hydraulic pump at a position upstream of the first travel switching valve. And a bypass passage connected to the discharge side of the second hydraulic pump is provided in the bypass passage from the first and second hydraulic pumps to the first and second travel switching valves. A hydraulic drive system for a construction machine, comprising flow rate limiting means for limiting the flow rate of pressure oil flowing through the bypass passage in order to compensate for the pressure of the supplied pressure oil. 2. The bypass passage has an end on the first side.
A first bypass passage connected to the discharge side of the hydraulic pump, a second bypass passage having one end connected to the discharge side of the second hydraulic pump, and the first and second bypass passages A third end connected to the other end of each of the first and second bypass passages so that the pressure oils from the first and second passages merge with each other;
The hydraulic drive device for a construction machine according to claim 1, wherein the third bypass passage portion has the other end connected to an input port of the boom switching valve. 3. A flow control device according to claim 1, wherein said flow restricting means is provided in said first bypass passage, and restricts a flow rate of pressure oil flowing through said first bypass passage, and said second bypass passage. A second throttle portion provided in the portion to restrict the flow rate of the pressure oil flowing in the second bypass passage portion; and a flow rate of the pressure oil flowing in the third bypass passage portion provided in the third bypass passage portion And a third throttle unit for controlling the flow rate of the pressure oil supplied to the input port side of the boom switching valve via the third bypass passage. 3. The hydraulic drive device for a construction machine according to claim 2, wherein the hydraulic pressure control device is configured to limit the pressure to be larger than the first throttle portion. 4. The first bypass passage portion allows a pressure oil to flow from the first hydraulic pump toward the second and third bypass passages and prevents a reverse flow. A first check valve is provided, and in the second bypass passage portion, pressure oil is allowed to flow from the second hydraulic pump toward the first and third bypass passages, and a reverse flow is provided. 4. The hydraulic drive device for a construction machine according to claim 2, wherein a second check valve for blocking is provided. 5. A first hydraulic pump having at least a first hydraulic pump and a second hydraulic pump, and having a discharge side of the first hydraulic pump including at least a first travel switching valve and a boom switching valve. A circuit is provided, and on the discharge side of the second hydraulic pump,
In a hydraulic drive system for a construction machine provided with a second hydraulic circuit including at least a second traveling switching valve, the boom switching valve is connected to the first traveling circuit on the first hydraulic circuit side. A tandem connection is provided at a position downstream of the valve, and an input port of the boom switching valve is connected to a discharge side of the first hydraulic pump at a position upstream of the first travel switching valve. A first bypass passage connected to a discharge side of the second hydraulic pump, and a first bypass passage connected to a discharge side of the second hydraulic pump. The first and second hydraulic passages are provided in the first and second bypass passages, respectively. First and second flow rate limiting means for limiting the flow rate of the pressure oil flowing through each of the bypass passages in order to compensate the pressure of the pressure oil supplied from the pump to the first and second travel switching valves. A hydraulic drive device for a construction machine, characterized by comprising means. 6. The first bypass passage includes a first bypass passage.
A first check valve for allowing pressure oil to flow from the hydraulic pump toward the input port side of the boom switching valve and preventing reverse flow, and the second bypass passage includes the first check valve. 6. The construction machine according to claim 5, wherein a second check valve is provided for allowing the pressure oil to flow from the second hydraulic pump toward the input port side of the boom switching valve and for preventing the reverse flow. Hydraulic drive.