JP2005299376A - Hydraulic control circuit for hydraulic shovel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control circuit for a hydraulic shovel capable of improving the efficiency of ground leveling work with simple constitution by increasing the speed of an arm cylinder when only arm pulling is independently operated. <P>SOLUTION: A travel straight advancing valve 17 switching oil pressure supply to traveling motors 11, 14 from hydraulic pumps 2, 3 is used as a confluence switching valve. When only the arm out of a boom and the arm is independently operated, the travel straight advancing valve 17 is switched into a confluence stop position to connect the hydraulic pump 2 to a boom control valve 7 and to open a cutoff valve 18 on the tank return side. When the boom and arm are simultaneously operated, the travel straight advancing valve 17 is switched into a confluence position, and the cutoff valve 18 is closed so that discharge oil of the hydraulic pump 2 joins discharge oil of the hydraulic pump 3 and is led to an arm control valve 10. The supply quantity of oil to the arm control valve 10 is thereby increased. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic control circuit that controls a hydraulic actuator of a hydraulic excavator.

  Conventionally, when leveling work is performed with a hydraulic excavator, an operation is performed in which the tip of the bucket is grounded with the boom and the arm extended to the maximum, and the bucket is pulled forward by simultaneously operating the boom raising and the arm pulling.

  When the arm pulls close to a vertical position by pulling the arm, it is not necessary to raise the boom. After that, the arm pull is operated with the full lever, while the boom is raised by gradually returning the operation lever. It becomes.

  In such leveling work, when the arm posture is substantially vertical, the peripheral speed at the bucket tip becomes slower than the cylinder speed of the arm cylinder. Therefore, when trying to increase the leveling efficiency, the cylinder speed of the arm cylinder May be insufficient.

  A hydraulic excavator is known that eliminates the delay in boom speed when boom raising and arm pulling are simultaneously performed (see, for example, Patent Document 1).

This hydraulic excavator is configured to increase the cylinder speed of the boom cylinder set for fine operation in consideration of the load work so that it can be operated at a speed corresponding to the high speed of the arm during leveling work. ing.
Japanese Patent Laid-Open No. 10-102547

  However, the conventional hydraulic excavator described above can be driven by matching the boom, which is originally set for speed with fine adjustment, during the leveling work, but the arm posture approaches almost vertical. It is not configured to increase the speed of the arm cylinder when only the arm pulling is performed.

  The present invention has been made in consideration of the problems in the conventional hydraulic excavator as described above, and has a simple configuration, and in the case of leveling work, when the boom raising and the arm pulling are simultaneously operated, the boom cylinder And a hydraulic control circuit for a hydraulic excavator that can operate each arm cylinder independently and increase the speed of the arm cylinder and increase the efficiency of leveling work when only arm pulling is operated alone It is.

  The present invention provides a boom control valve that guides pressure oil supplied from a first hydraulic pump to a boom cylinder in response to an operation of the boom operating means, and pressure oil supplied from a second hydraulic pump to operate an arm operating means. In response, the arm control valve that leads to the arm cylinder, the merging stop position where the first hydraulic pump is disconnected from the arm control valve and connected to the boom control valve, and the pressure oil from the first hydraulic pump is supplied to the first hydraulic pump. A merging position that can be switched to a merging position where a part of the pressure oil discharged from the second hydraulic pump is led to the boom control valve side while being joined with the pressure oil from the two hydraulic pumps and led to the arm control valve. Only the switching valve, the cut valve provided in the return oil passage connecting the boom control valve and the tank, and the boom operating means and the arm operating means of the arm operating means are operated alone. The merging switching valve is set to the merging position and the cut valve is closed. When the boom operating means and the arm operating means are operated simultaneously, the merging switching valve is set to the merging stop position and the Control means for opening the cut valve, a first traveling motor is provided in the same oil passage as the boom control valve and the cut valve, and the first oil passage is provided in the same oil passage as the arm control valve. Two traveling motors are provided, and the merging switching valve is configured such that the pressure oil from the first hydraulic pump and the second hydraulic pump is independent of the first traveling motor and the second traveling motor, respectively, at the merging stop position. The pressure oil is guided by introducing a part of the pressure oil discharged from the first hydraulic pump to the first travel motor at the merging position. Also serves as the straight traveling valve to the condition to be distributed to the above-described first traveling motor and said second traveling motor.

  According to this configuration, when the boom raising and the arm pulling are operated simultaneously, the merging switching valve is switched to the merging stop position and the cut valve on the arm control valve side is opened, so that the boom cylinder and the arm cylinder are Each can be operated independently. On the other hand, when only the arm pulling is operated, the merging switching valve is switched to the merging position, the cut valve is closed, and the pressure oil from the first hydraulic pump and the second hydraulic pump is merged and supplied to the arm cylinder. As a result, the speed of the arm cylinder can be increased. This makes it possible to increase the flow rate supplied to the arm cylinder in situations where, for example, the arm posture is substantially vertical and the arm speed is insufficient during leveling work, the peripheral speed at the front attachment tip is reduced. It can be eliminated to improve the work efficiency of leveling.

  In addition, the merging switching valve supplies pressure oil from the first hydraulic pump and the second hydraulic pump to the first oil passage with respect to the travel motor provided in the first oil passage and the travel motor provided in the second oil passage. And a position for supplying each of the oil passages independently (the merging stop position), and a position for distributing and supplying one of the first and second hydraulic pumps to each traveling motor (the aforementioned Therefore, the common switching valve can be used as both the merging switching valve and the traveling straight valve, and the existing circuit can be used without any significant design change. The effect of can be realized.

  As a specific switching method of the merging switching valve, for example, a detecting means for detecting a boom raising operation amount by the boom operating means is provided, and the control means has a boom raising operation amount detected by the detecting means. It is preferable to set the merging switching valve to the merging position and close the cut valve when it is below a certain level.

  The control means further includes a detecting means for detecting a boom raising operation amount by the boom operation means, and the control means is provided for the arm from the first hydraulic pump as the boom raising operation amount by the boom operation means decreases. If the opening degree of the merging switching valve and the cut valve is changed so as to increase the merging flow rate of the pressure oil supplied to the control valve, the merging switching valve and the cut valve are gradually switched during the arm pulling operation. , You can get a shock-free operation. Also, when boom raising and arm pulling are operated simultaneously, the merging switching valve is switched to the diversion side and the cut valve is opened as the amount of operation of the boom operating means increases, so operation without shock can be obtained. It is done.

  As described above, according to the present invention, when the boom raising and the arm pulling are simultaneously operated by the automatic switching of the merging switching valve and the cut valve, each cylinder can be operated independently, When only pulling is operated alone, the speed of the arm cylinder can be increased. This makes it possible to increase the flow rate supplied to the arm cylinder in situations where, for example, the arm posture is substantially vertical and the arm speed is insufficient during leveling work, the peripheral speed at the front attachment tip is reduced. There is an effect that can be eliminated and the work efficiency of leveling can be improved. Moreover, since the merging switching valve also serves as a traveling straight valve, the above-described effects can be realized with a simple configuration using an existing circuit.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 shows a hydraulic control circuit when the present invention is applied to a hydraulic excavator as a first embodiment.

  Although the hydraulic excavator is not shown in the figure, an upper swinging body is mounted on the lower traveling body so as to be freely rotatable, and a front attachment is provided at the front of the upper swinging body. This front attachment is composed of a boom, an arm, and a bucket. It is what has been.

  In the figure, the first hydraulic pump 2, the second hydraulic pump 3, and the pilot pump 4 that generates the pilot pressure Pa are operated by driving the engine 1, respectively.

  The first hydraulic pump 2 and the second hydraulic pump 3 are variable displacement pumps, and the discharge flow rate changes based on the inclination angle of the swash plate.

  The hydraulic oil discharged from these hydraulic pumps 2 and 3 is a right travel motor control valve 5, a bucket cylinder control valve 6, and a boom cylinder control arranged in a left center bypass line (first oil passage) LCB. The left travel motor control valve 8, the swing motor control valve 9, and the arm cylinder control valve that are supplied to the valve (boom control valve) 7 and arranged in the right center bypass line (second oil passage) RCB (Arm control valve) 10 is supplied.

  A left cut valve (corresponding to the “cut valve” of the present invention) 18 is provided on the downstream side (return oil passage) of the boom cylinder control valve 7 in the left center bypass line LCB, and the arm in the right center bypass line RCB. A right cut valve 19 is provided downstream of the cylinder control valve 10.

  A right travel motor 11 is connected to the right travel motor control valve 5, a bucket cylinder 12 is connected to the bucket cylinder control valve 6, and a boom cylinder 13 is connected to the boom cylinder control valve 7.

  The left travel motor control valve 8 includes a left travel motor 14, the swing motor control valve 9 includes a swing motor 15 that rotates the upper swing body, and the arm cylinder control valve 10 includes an arm cylinder 16. It is connected.

Right traveling upstream oil passage L ₁ of the motor control valve 5 is provided with the straight traveling valve (confluence switching valve) 17, the straight traveling valve 17, when not performing ground leveling work to be described later, the conventional It is switched to ensure straight running stability, which is a function of

Specifically, the straight travel valve 17 has a switching position between a divergence position a and a merging position b, which are merging stop positions, and is normally held at the divergence position a. In shunt position a hydraulic fluid delivered from the first hydraulic pump 2 is supplied to the left center bypass line LCB side through the oil path L _1. Meanwhile, the pressure oil discharged from the second hydraulic pump 3 is supplied to the right center bypass line RCB through an oil passage L _2.

  In this case, the right travel motor control valve 5 and the left travel motor control valve 8 are independently supplied with pressure oil from the first hydraulic pump 2 and the second hydraulic pump 3, respectively.

Next, when the straight traveling valve 17 is switched from the flow dividing position a to the confluence position b, pressure oil from the first hydraulic pump 2 flows through the oil passage L _3. The oil passage L ₃ is connected to an oil passage L ₄ branched from the downstream side of the left travel motor control valve 8 in the right center bypass line RCB at a junction P, and the oil extending from the junction P Pressure oil is supplied to the swing motor control valve 9 and the arm cylinder control valve 10 through the path L ₅ . A part of the pressure oil flowing through the oil passage L ₃ can be supplied to the bucket cylinder control valve 6 and the boom cylinder control valve 7.

On the other hand, the pressure oil from the second hydraulic pump 3 is distributed in parallel to the oil passages L ₁ and L ₂ and distributed and supplied to the left and right traveling motor control valves 8 and 5. Thereby, for example, even when performing a complex operation that raises and lowers the boom while driving the left and right traveling motors 11 and 14, the pressure oil from the second hydraulic pump 3 is equal to the left and right traveling motors 11 and 14. Supplied so that the straight running performance can be maintained.

  Next, switching control of the traveling straight valve 17 and the cut valve 18 will be described.

  The illustrated circuit includes a bucket operation remote control valve 20 having a bucket operation lever 20a, a boom operation remote control valve (boom operation means) 22 having a boom operation lever 22a, and an arm operation remote control valve having an arm operation lever 25. (Arm operation means) 25 is connected. These remote control valves 20, 22, 25 output pilot pressures corresponding to the operation directions and operation amounts of the operation levers 20a, 22a, 25a.

First, pilot pressures P ₁ and P ₂ derived from the bucket operation remote control valve 20 are applied to each pilot port of the bucket cylinder control valve 6, and either _{one of} the pilot pressures P ₁ and P ₂ is provided by the shuttle valve 21. Is selected, and the selected pilot pressure P ₁ (or P ₂ ) and the boom raising pilot pressure P ₃ derived from the boom operation remote control valve 22 are further shuttle valves (detection means for detecting the boom raising operation pressure). 23 is selected higher. That is, the shuttle valves 21 and 23 detect a composite operation.

  The pilot pressure selected by the shuttle valve 23 is given to the pilot port of the flow control valve 24. The flow control valve 24 can be switched between a blocking position c and a communication position d, and is normally held at the communication position d.

A part of the arm pulling pilot pressure P ₄ derived from the arm operation remote control valve 25 is given to the flow control valve 24, and the arm pulling pilot pressure P ₄ sent from the flow control valve 24 is the oil path L _6. , And is supplied to the pilot port of the traveling straight valve 17 via the shuttle valve 26. The shuttle valve 26 performs high-order selection between the pilot pressure and the arm pulling pilot pressure P ₄ based on the simultaneous operation of the traveling operation and the attachment operation.

The oil passage L ₇ branched from the oil passage L ₆ is connected to the pilot port of the left cut valve 18 described above via the shuttle valve 27. Incidentally, the shuttle valve 27 is a arm pulling pilot pressure or outside the operating pressure (e.g. arm pushing pilot pressure) to perform the high-level selection of arm pulling pilot pressure P _4. In the figure, 28 is a tank to which return oil is returned.

  The flow control valve 24 and the shuttle valve 26 described above constitute control means for switching the position of the traveling straight valve 17 in accordance with the status of arm operation and boom operation. 3 also serves as a merging switching valve for switching the supply state of pressure oil from the boom cylinder control valve 7 to the arm cylinder control valve 10.

  Next, the operation of the hydraulic control circuit will be described.

When arm pulling is independently operated in leveling work or the like, or when the arm pulling single operation is performed by stopping the boom raising operation during simultaneous operation of boom raising and arm pulling, the bucket is connected to the pilot port of the flow control valve 24. since the operating lever 20a or the boom operating lever 22a no pilot pressure is applied, some of the pilot pressure P ₄ flows through the oil passage L ₆ and L ₇ through the communicating position d of the flow control valve 24.

The pilot pressure P ₄ is applied to the pilot port of the straight travel valve 17 through the oil passage L _{6 and} is applied to the pilot port of the left cut valve 18 through the oil passage L ₇ . Thereby, the traveling straight valve 17 is switched from the diversion position a to the merge position b, and the left cut valve 18 is switched from the communication position e to the cutoff position f.

When the traveling straight valve 17 is switched to the merge position b, the pressure oil from the first hydraulic pump 2 is supplied to the arm cylinder control valve 10 through the oil passage L ₃ → L ₅ , and the pressure oil from the second hydraulic pump 3 is supplied. Since the left cut valve 18 of the left center bypass line LCB is closed, it flows through the oil passage L ₂ → L ₄ and joins with the pressure oil from the first hydraulic pump 2 in the oil passage L ₅ .

  Thereby, when the arm pulling single operation is performed, the flow rate supplied to the arm cylinder control valve 10 is increased, and the cylinder speed of the arm cylinder 16 can be increased.

On the other hand, when the boom raising and the arm pulling are operated simultaneously, the boom raising pilot pressure P ₃ is applied to the pilot port of the flow control valve 24 via the shuttle valve 23, and the flow control valve 24 is shut off from the communication position d. Switch to position c.

Similarly, when the bucket excavation / bucket discharge is operated in the leveling work, the flow control valve 24 receives the pilot pressure P ₁ (or P ₂ ) and switches from the communication position d to the cutoff position c.

When the arm operation remote control valve 25 and the oil path L ₆ are shut off, no pilot pressure is established in the oil paths L ₆ and L ₇ , and the traveling straight valve 17 is switched from the merge position b to the diversion position a, and the left cut valve 18 switches from the blocking position f to the communication position e.

  Therefore, in this case, the pressure oil from the first hydraulic pump 2 and the pressure oil from the second hydraulic pump 3 are not merged, and the pressure oil from the first hydraulic pump 2 is supplied to the boom cylinder control valve 7. Then, the pressure oil from the second hydraulic pump 3 is supplied to the arm cylinder control valve 10, and the respective operation pressures can be secured.

  The straight travel valve 17 and the left cut valve 18 described above may simply be turned on / off (that is, opened / closed), but gradually switch in proportion to the operation amount of the boom operation lever 22a. If it comprises, it will become possible to perform the switching with the joining of a hydraulic oil from both the hydraulic pumps 2 and 3, and a shunt, without a shock.

  In that case, if the pump flow rate on the merging side is a negative control machine, closing the left cut valve 18 lowers the negative control pressure and increases the flow rate. In the case of a positive control machine, when the hydraulic control is performed, the pump flow rate of the first hydraulic pump 2 can be increased by a pilot pressure that switches the traveling straight valve 17 and the left cut valve 18.

  FIG. 2 shows a second embodiment of the present invention, in which the above-described merging / dividing control is electrically controlled by a controller.

  In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

In FIG. 2, bucket pilot pressure sensors 30 and 31 are provided on the secondary side of the bucket operation remote control valve 20, and bucket excavation pilot pressure S ₁ and bucket discharge pilot pressure S ₂ are electrically supplied from the sensors 30 and 31, respectively. Output as a signal.

The secondary side of the boom operating remote control valve 22 is in (boom-up) (detecting means for detecting a boom raising operation pressure) the boom pilot pressure sensor 32 is provided, is output boom raising pilot pressure S _3.

  Each of the sensors 30 to 32 detects a composite operation.

The arm pilot pressure sensor 33 to the secondary side of the arm operating remote control valve 25 (arm pulling) has provided, arm pulling pilot pressure S ₄ is outputted.

The pilot pressures S _{1 to} S ₄ are given to the controller 34, and based on the pilot pressures S _{1 to} S ₄ , the controller 34 controls the proportional valve 35 connected to the pilot port of the traveling straight valve 17. The left cut valve 18 is controlled via the proportional valve 36. The controller 34 and the proportional valve 36 function as control means.

  Hereinafter, the control contents of the controller 34 will be described with reference to the flowchart shown in FIG.

In the figure, the controller 34 of the boom raising pilot pressure S ₃ and the bucket excavation pilot pressure S ₁ and the bucket release pilot pressure S _2, performs high-level selection (step S1).

Within controller 34, as shown in FIG. 3, the high-level selected pilot pressure f ₀ is maintaining the pressure f ₁ to the lowest pressure is constant below a region, it said the pilot pressure f ₀ is equal to or greater than the certain that A map having a characteristic C1 that increases the pressure f ₁ as the pilot pressure f ₀ increases is stored in advance, and the pressure f ₁ corresponding to the pilot pressure selected at a higher level is obtained (step S2).

Next, when determining the command f ₂ for the straight travel valve 17 and the left cut valve 18,
f ₂ = arm pulling pilot pressure S _4- f ₁
Is obtained (step S3).

The purpose of performing the above calculation is to cancel the merging command for the traveling straight valve 17 while suppressing f ₂ when arm pulling and boom raising (or bucket excavation / bucket discharge) are simultaneously performed.

Then calculated confluence command I ₁ for proportional valve 35 based on the map of the confluence command I ₁ having a characteristic C2 so as to increase with increasing the f ₂ (step S4).

Next, the closing command I ₂ for the proportional valve 36 is calculated based on the map of the switching command I ₂ having the characteristic C3 that increases as f ₂ increases (step S5).

Next, by outputting the determined merge command I ₁ to the proportional valve 35 and the close command I ₂ to the proportional valve 36 (step S6), the straight travel valve 17 and the left cut valve 18 are respectively controlled.

That is, when f ₂ is increased, in other words, when f ₁ corresponding to the boom raising operation amount is decreased, the values of the merging command I ₁ and the closing command I ₂ are increased, whereby the traveling straight valve 17 is gradually moved from the branch position a. The merging position b is switched, and the left cut valve 18 is gradually switched from the communication position e to the blocking position f. Thereby, the pressure oil of the first hydraulic pump 2 and the second hydraulic pump 3 is merged and supplied to the arm cylinder control valve 10.

On the other hand, when the value of f ₂ is small due to boom raising or bucket excavation / bucket discharge, the merging command I ₁ does not increase in the characteristic C2, and the closing command I ₂ does not increase in the characteristic C3. The proportional valve 36 does not operate and the first hydraulic pump 2 and the second hydraulic pump 3 are not merged.

  In this case, the operation pressures of the boom cylinder 13 and the arm cylinder 10 can be ensured.

1 is a hydraulic circuit diagram showing a first embodiment of the present invention. It is a hydraulic circuit diagram which shows 2nd embodiment of this invention. It is a flowchart which shows the control content of the controller shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 1st hydraulic pump 3 2nd hydraulic pump 4 Pilot pump 6 Bucket cylinder control valve 7 Boom cylinder control valve 10 Arm cylinder control valve 11 Right travel motor 12 Bucket cylinder 13 Boom cylinder 14 Left travel motor 16 Arm cylinder 17 Traveling straight valve (Joint switching valve)
18 Left cut valve (cut valve)
19 Right cut valve 20 Remote control valve for bucket operation 21 Shuttle valve 22 Remote control valve for boom operation (boom operation means)
23 Shuttle valve 24 Flow control valve (control means)
25 Remote control valve for arm operation (arm operation means)
30 Boom pilot pressure sensor (detection means)
34 Controller (control means)

Claims (3)

A boom control valve that guides the pressure oil supplied from the first hydraulic pump to the boom cylinder according to the operation of the boom operating means;
An arm control valve for guiding the pressure oil supplied from the second hydraulic pump to the arm cylinder according to the operation of the arm operating means;
The first hydraulic pump is separated from the arm control valve and connected to the boom control valve, and the pressure oil from the first hydraulic pump is merged with the pressure oil from the first hydraulic pump and the pressure oil from the second hydraulic pump. A merging switching valve that can be switched to a merging position that leads to the arm control valve and leads part of the pressure oil discharged from the second hydraulic pump to the boom control valve side;
A cut valve provided in a return oil passage connecting the boom control valve and the tank;
When only the arm operating means among the boom operating means and the arm operating means is operated alone, the merging switching valve is set to the merging position, the cut valve is closed, and the boom operating means and the arm operating means are And a control means for opening the cut valve and setting the merging switching valve to the merging stop position when simultaneously operated, and
A first traveling motor is provided in the same oil passage as the boom control valve and the cut valve;
A second traveling motor is provided in the same oil passage as the oil passage in which the arm control valve is provided;
The merging switching valve is in a state in which pressure oil from the first hydraulic pump and the second hydraulic pump is independently supplied to the first traveling motor and the second traveling motor, respectively, at the merging stop position, By introducing a part of the pressure oil discharged from the first hydraulic pump to the first traveling motor at the joining position, the pressure oil is distributed and supplied to the first traveling motor and the second traveling motor. A hydraulic control circuit for a hydraulic excavator, which also serves as a traveling straight valve.   In addition to detecting means for detecting a boom raising operation amount by the boom operating means, the control means sets the merging switching valve to a merging position when the boom raising operation amount detected by the detecting means is equal to or less than a predetermined value. 2. The hydraulic control circuit for a hydraulic excavator according to claim 1, wherein the cut valve is closed.   Detection means for detecting a boom raising operation amount by the boom operation means, and the control means from the first hydraulic pump to the arm control valve as the boom raising operation amount by the boom operation means decreases. The hydraulic control circuit for a hydraulic excavator according to claim 1, wherein the opening degree of the merging switching valve and the cut valve is changed so as to increase the merging flow rate of the pressure oil supplied to the hydraulic excavator.

Images