JPS6378930A - Oil-pressure traveling circuit for oil-pressure shovel - Google Patents

Abstract

PURPOSE:To prevent the occurrence of undesirable confined pressure by a method in which the spool of a counter balance value is divided into two, the third pilot chamber is formed in a faced manner, the higher pressure side of the pressure of the main circuit is selectively supplied to the chamber, and a control valve is specifically led to the spool of open center. CONSTITUTION:The first and second pilot chambers 9a and 9b introducing the pressure of the main circuit are provided between a traveling motor 2 and a drive control valve 30. The spools 8a and 8b of a counter balance valve 7 are operated by pressure oil in the chambers 9a and 9b. The third pilot chamber 20 is provided in the face of the counter ends of the spools 8a and 8b. A throttle 22 is provided between a shuttle valve 21 provided between the inlet pots 10a and 10b and the chamber 20, and the higher pressure of the ports 10a and 10b is selected by the valve 21 and transmitted to the chamber 20. The open center spool is provided for the control valve 30, and the entrance ports 30d and 30f are led to the outlet port 30c through the throttles 25a and 25b by the valve 30.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a traveling hydraulic circuit for a hydraulic excavator having a counterbalance valve.

<Prior Art> FIG. 4 is a circuit diagram showing a traveling hydraulic circuit of a conventional hydraulic excavator of this type. In this figure, ■ is a hydraulic pump,
2 is a travel motor of the hydraulic excavator, 3 is a control valve that controls the drive of the travel motor 2, and 4 is a relief valve that defines the maximum pressure of the hydraulic circuit. 5.6 is a cross relief valve provided between the pipes 16a and 16b on both sides of the traveling motor 2, and allows the oil in the pipes to flow from the high pressure side to the low pressure side I\. Reference numeral 7 denotes a counterbalance valve, which is installed between the conduits 15a, 15b from the control valve 3 and the conduits 16a, 16b of the travel motor 2. Reference numeral 8 denotes a spool of a counterbalance valve, which can be switched to a neutral position and a left/right position. 9
A and 9b are pilot rooms provided facing both sides of the spool 8, 10a and 10b are inlet boats of the counterbalance valve 7, and 11a and llb are outlet boats. 12a,
12b is the pilot room 9a, 9b and the entrance bow I to 10a
, 10b, and a diaphragm 13a, 1
3b is the inlet boat 10a, 10b and the outlet port 11a,
This is a check valve provided between the

When the control valve 3 is switched to the left position, for example, in order to run the hydraulic excavator, pressure oil from the hydraulic pump 1 is supplied to the travel motor 2 via the pipe 15a, the check valve 13a, and the pipe 16a. At this time, the pressure in the conduit 15a increases, and this pressure is transmitted to the pilot chamber 9a via the throttle 12a, so the spool 8 is moved to the right and switched to the left position. The pressure oil supplied to the travel motor 2 is returned to the tank through the pipe line 16b, the outlet boat 11b, the switched spool 8, the inlet boat 1-10b, the pipe line 15b, and the control valve 3. As a result, the traveling motor 2 is driven, and the hydraulic excavator travels in the direction corresponding to the switching of the control valve 3.

In this bad condition, when the road becomes downhill and the hydraulic excavator starts traveling on this downhill slope, the travel motor 2 performs a pumping action. Therefore, the pressure in the pipe line 16a decreases, and the pressure in the pipe line 16b decreases.
, the spool 8 of the counterbalance valve 7 moves to the left by an amount corresponding to the pressure drop in the lines 16a, 15a, thereby throttling the return path from line 16b to the tank. As a result, the pressure in the conduit 16b further increases and acts as a brake on the travel motor 2. When the pressure in the conduit 16b reaches the set value, the cross relief valve 5 opens and the conduit 16
The oil b flows into the pipe 16a and absorbs the inertial energy of the travel motor 2.

When traveling downhill, if the throttle 12a is not provided, the pressure in the conduit 15a will be immediately transmitted to the pilot chamber 9a, and the spool 8 will constantly move left and right in response to changes in the pressure in the conduit 15a. It moves and causes oscillation, and it is impossible to keep it stopped at a proper position. Aperture 12a (
12b) is provided for this purpose, and provides damping to the spool 8 to prevent the above-mentioned oscillation. As described above, the throttle 12a (12b) effectively performs its function when traveling downhill, etc., but when the hydraulic excavator is moving at other times (f%), the throttle 12a (12b) gives excessive damping to the spool 8. , which can lead to extremely inconvenient $ situations. An example of such a case will be described below.

When running a hydraulic excavator, there are times when a sudden reverse operation is performed, from forward to reverse, or from reverse to forward. In addition, if mud, pebbles, etc. are attached to the tracks, in order to remove the mud or pebbles, etc., place a packet on the ground, support the hydraulic excavator at an angle between the front track and one of the tracks, and remove the floating one. Work is sometimes performed to drive the crawler tracks in forward and reverse rotation.

In order to perform these operations, first, as described above, the control valve 3 is switched to the left position to drive the travel motor 2 in one direction, and then, in order to reverse the travel motor 2,
The control valve 3 in the left position is switched to the right position. Then, the supply of pressure oil to the pipe line 15a is cut off, the pressure decreases, and this is transmitted to the pilot I chamber 9a via the throttle 12a. Therefore, the spool 8, which had reached the stroke end in the right direction, returns to the neutral direction while moving the inlet ports h10a, 10b and the outlet boats lla, 11.
Close the circuit between b. As a result, the traveling motor 2 performs a pumping action due to its inertia, and the pipe line 1 on the discharge side
The pressure at 6b is increased and the brake is applied to the travel motor 2. The inertial energy of the travel motor 2 is absorbed by the cross relief valve 5 that allows oil to flow from the pipe line 16b to the pipe line 16a. - On the other hand, when the control valve 3 is switched to the right position, the pressure in the pipe line 15b increases, and the pressure in the pilot chamber 9b increases.
pressure also increases. Then, when the absorption of inertial energy of the travel motor 2 is completed and the pressure at the outlet port llb decreases and the pressure at the inlet boat 10b becomes higher, the pressure oil of the hydraulic pump 1 is transferred to the control valve 3, the pipe line 15b, and the check valve. It is supplied to the travel motor 2 via the valve 13b and the pipe 16b, and causes the travel motor 2 to rotate in reverse. During this time, the spool 8 is actively moved to the left due to the pressure increase in the pilot chamber 9b as described above.

<Problems to be Solved by the Invention> However, in the conventional travel hydraulic circuit described above, the shift of the spool 8 to the left causes the oil in the pilot chamber 9a to be transferred to the inlet port by the pressure in the pilot chamber 9b. 10
The flow rate of this oil discharged is subjected to great resistance due to the presence of the throttle 12a, and the pressure in the pilot chamber 9a rises to almost the same pressure as the pressure in the pilot chamber 9b. The leftward movement of the spool 8 results in a uniform movement. On the other hand, in the case of idle rotation of the crawler track or rapid forward/reverse switching, the reverse rotation of the traveling motor 2 is performed at a time after the control valve 3 is switched to the right position. This time is shorter than the time during which the spool 8 is switched to the right position while receiving resistance from the throttle 12a. Therefore, when the travel motor 2 is reversed, the space between the outlet port lla and the inlet port 10a is closed, and the pressure in the conduit 16a becomes approximately equal to the pressure in the conduit 16a due to the reverse rotation of the travel motor 2, and , a pressure as high as the inertial force absorbed in the reverse direction of the traveling motor 2 is trapped in the pipe line 16a. In this case, the cross-relief valve 5.6 is normally
61], so when high pressure (supply pressure from the hydraulic pump 1) is acting on the pipe line 16b as described above, the relief operating pressure of the pipe line 16a is
The sum of the pressure b and the set pressure of the cross relief valve 6 becomes an extremely high confining pressure.

As mentioned above, if the aperture 12a exists, the spool 8
If the moving speed of the travel motor 2 becomes slow and the inertia of the travel motor 2 is small, there is a risk that abnormally high pressure will occur in the conduit 16a on the discharge side of the travel motor 2 when it is reversed, which may shorten the life of the travel motor 2. have a negative impact. The generation of such abnormal high pressure may occur not only when the crawler tracks are idling in forward and reverse directions or when rapidly moving forward and backward, but also during other operations.

The present invention has been made in view of the above-mentioned actual state of the prior art, and its purpose is to provide a travel hydraulic circuit for a hydraulic excavator that can prevent the generation of undesired confinement pressure in the travel motor and counterbalance valve. It is about providing.

Means for Solving the Problems In order to achieve this object, the present invention provides a traveling motor,
A control valve that controls the drive of this travel motor, a hydraulic pump that supplies driving pressure oil to the travel motor via this control valve, and a hydraulic pump that is provided between the travel motor and the control valve and The first where the circuit pressure is led
and a second pilot chamber, and a counterbalance valve having a spool operated by pressure oil in both of these pilot chambers, the spool of the counterbalance valve described above is divided into two, and the spool is opposed to both of these spools. A third pilot chamber formed as shown in FIG. It has a configuration including a spool, a motor boat and a tank boat 1 that communicate with each other through a throttle when in neutral.

<Function> The traveling hydraulic circuit of the hydraulic excavator of the present invention has a configuration in which the spool of the counterbalance valve is divided into two as described above, and a third pilot chamber is provided between these two spools. When the motor starts to drive in reverse, that is, when the control valve is switched, the oil discharged from the hydraulic pump is
One of the spools located on the side to which the discharge oil of the travel motor is guided is instantly switched, and the outlet of the counterbalance valve on the side to which the discharge oil of the travel motor is guided via the spool. The boat and the inlet boat are electrically connected, and it is possible to prevent the generation of undesirable confinement pressure in the oil discharged from the travel motor.

In addition, as mentioned above, the control valve is set to the open center position, and the motor boat is configured to communicate with the tank port through the throttle when in neutral, so the control valve is set to the neutral position when the travel motor is stopped. When the control valve is returned to its original position, the control valve can be throttled to generate brake pressure to stop the travel motor. In other words, both the control valve and the counterbalance valve can generate brake pressure, and the control valve can generate brake pressure to stop the travel motor. can be generated before the brake pressure is generated by the counterbalance valve, thereby ensuring a longer brake pressure generation time and alleviating the shock when the traveling motor stops.

<Example> Hereinafter, a traveling hydraulic circuit of a hydraulic excavator according to the present invention will be explained based on the drawings.

Figures 1 to 3 are explanatory diagrams showing one embodiment of the present invention. Figure 1 is an overall circuit diagram, Figure 2 is an enlarged view of a control valve, and Figure 3 is shown in Figure 2. FIG. 3 is a characteristic diagram showing the relationship between the position A of the spool of the control valve and the opening area B. FIG.

In FIG. 1, 8a and 8b are spools of the counterbalance valve 7, which can be switched to the left and right positions, respectively. 2
0 is the third pilot chamber provided facing the opposite ends of both spools 8a and 8b, 21 is both robot 1□ 10 a
, 10b, and 22 is a throttle provided between the shuttle valve 21 and the third pilot room 20.
, 10b is selected, and the pressure is transmitted to the third pilot chamber 20 via the throttle 22.

Reference numeral 30 is a control valve for controlling the drive of the travel motor 2, which has an open center spool and, as shown in FIG.
The outlet boat 30d, the inlet, the outlet boat 30f, and the tank boat, that is, the outlet port 30c are constricted 25a, 25.
It is set to communicate via b.

The operation of the embodiment configured as described above will be explained below.

When the control valve 30 is switched to the left position, the pressure oil of the hydraulic pump 1 flows through the pipe 15a, the check valve 13a, and the pipe 16.
It is supplied to the traveling motor 2 via a. At this time, the shuttle valve 21 selects the pressure oil on the high-pressure side inlet boat 10a of the two-man robots 10a and 10b, and selects the pressure oil on the high-pressure side inlet boat 10a.
The pressure oil of 0a is guided to the third pilot chamber 20 via the shuttle valve 21 and the throttle 22, and the pressure oil of the inlet boat 10a is also guided to the pilot chamber 9a via the throttle 12a, and finally the spool 8a does not move because it receives the same pressure from opposite directions. On the other hand, the pilot chamber 9b has an aperture 12b.
It communicates with the low-pressure large-mouth boat 10b through the third
When the pressure in the pilot chamber 20 increases to a pressure that overcomes the force of the spring 24b, that is, a cracking pressure or higher,
The spool 8b is pushed to the right by the pressure oil in the third pilot chamber 20, and this causes the exit bow to move upward. -1lb and the inlet bow) 10b are electrically connected. That is, the pressure oil discharged from the traveling motor 2 is transferred to the pipe line 16b and the outlet boat 11.
b, inlet boat 10b, pipe line 15b, control valve 3
Pass through 0 and return to the tank.

Here, the operation of the control valve 30 among the above operations will be described in detail using FIGS. 2 and 3. In addition,
In Fig. 2, AO indicates the neutral position, A4 indicates the left side position, and the spool positions A in Fig. 3, Aol, to, are the positions shown in Fig. 2, and A1, A2, and A3 are the neutral positions. The spool position between position Ao and left side position A4 is
indicates the minimum opening area, and B1 indicates the maximum opening area.

In addition, in FIG. 3, C represents boat 30c and boat 30.
d shows the characteristic line of the opening area of the communication path, D is the boat 30
A characteristic line of the opening area of the communication path between b and boat 30e is shown,
E indicates a characteristic line of the opening area of the communication passage between the boat 30a and the boat 30d, and F indicates a characteristic line of the opening area of the communication passage between the boat 30c and the boat 30f.

Then, the control valve 30 is at the neutral position A as described above.
When the spool is switched from position AO to left position A4, looking at the process from the start to the end of switching in the characteristic diagram of Fig. 3, as the spool moves from position AO to position A4, boat 3
It closes at position A1 as shown by characteristic line C representing the communication state between 0c and boat 30d. Then, the spool begins to open from position A2 as shown by the characteristic line representing the communication state between the boats 30a and 30d. As a result, the oil discharged from the hydraulic pump 1 is supplied to the pipe line 15a shown in FIG.

Furthermore, as shown by the characteristic line representing the communication state between the boats 30b and 30e, the communication path between the boats 1 to 30b and the boat 30e is at position A. Therefore, the hydraulic pump 1 and the tank were in communication with each other, and the oil discharged from the hydraulic pump 1 was released into the tank. When the spool moves to the vicinity of position A2, the area of the communication path between the boat 30b and the boat 30e decreases as shown by the characteristic line, that is, the communication path is narrowed. As a result, pressure is built up in the discharge pipe of the hydraulic pump 1, and the pressure oil is transferred to the pipe 15a communicating with the travel motor 2.
It starts to flow.

Furthermore, as shown by the characteristic line F representing the communication state between the boat 30f and the boat 30c, from the position Ao to the vicinity of the position A2, F
1, that is, the boat 30f and the boat 30C communicate through the aperture 25b shown in FIG.
The area of the aperture 25b portion begins to expand after passing 2, and the communication path between the boat 30f and the boat f-30c is completely opened near the positions A3 and A41. As a result, the conduit 15b communicates with the tank as described above, and the travel motor 2 is activated. Further, the communication path between the boat 30b and the boat 30e is also completely closed at position A3 as shown by the characteristic line, so that all of the pressure oil from the hydraulic pump 1 is sent to the travel motor 2 through the conduit 15a.

Further, in this embodiment, for example, when the travel motor 2 is driven as described above and the hydraulic excavator is traveling, when the road becomes downhill and the hydraulic excavator starts traveling down the downhill slope, The travel motor 2 performs a pumping action.

Due to this, the pressure in the conduit 16a decreases, the pressure in the conduit 16b increases, and the spool 8b is moved to the left by the pressure decrease in the third pilot chamber 20, which changes in accordance with the pressure decrease in the conduits 16a and 15a. The vehicle moves in this direction, and the return path from the pipe 16b to the tank is narrowed, and the vehicle travels while applying hydraulic brakes.

In this way, when there is a load fluctuation such as a change in the condition of the road surface on a slope, the throttles 12b and 22 are used for supplying and discharging pressure oil to the pilot chambers 9b and 20 at both ends of the spool 8b.
2a, 22 are pilot chambers 9a at both ends of the spool 8a,
Each provides resistance to the supply and discharge of pressure oil to and from the spools 8a and 8b, thereby preventing oscillation of the spools 8a and 8b.

In addition, in this embodiment, when the control valve 30 from the left side position A4 is switched to the right side position A5 while driving or when the crawler track is idling, the oil discharged from the hydraulic pump 1 is transferred from the pipe 15a by the control valve 3o. The oil line is switched to the pipe line 15b, pressure oil is supplied to this pipe line 15b, and the shuttle valve 21 selects the high pressure side inlet port l-10b of the two robots 10a and 10b, and selects the high pressure side inlet port l-10b of the inlet boat 10b. Pressure oil is transmitted to the third pilot chamber 20 via a shuttle valve 21 and a throttle 22. Also, pressure oil from the inlet boat 10b is similarly guided to the pilot chamber 9b via the throttle 12b, so that the pilot chambers 9b, 20 at both ends of the spool 8b
The pressures become the same, and the spool 8b continues to return only by the force of the spring 24b.

On the other hand, when the pressure in the pipe line 15b increases and reaches the pressure in the third pilot chamber 20 or the cranking pressure of the spring 24a, the spool 8a is pushed leftward by the pressure oil in the third pilot chamber 20. Electrical continuity is established between the exit boat 11a and the entrance boat 10a.

When the pressure in the pipe 15b further increases and becomes higher than that in the pipe 16b, the check valve 13b opens, and the pressure oil from the hydraulic pump 1 is supplied to the travel motor 2 via the pipe 15b, the check valve 13b, and the pipe 16b. Then, the traveling motor 2 is rotated in the reverse direction.

When the traveling motor 2 starts to drive in reverse, the outlet boat 1'' 11a and the inlet boat 10a are in a conductive state as described above, so the oil discharged from the traveling motor 2 is trapped in the pipe 16a. It is returned to the tank without being
There is no risk of abnormally high pressure occurring at 6a. Since the operation from reverse rotation to forward rotation is performed in the same manner, the explanation thereof will be omitted.

In addition, in this embodiment, when the control valve 30, which was at the left position A4 in FIG. The opening area of the passage changes from position A4 to position Ar3 shown in FIG. Masu,
Characteristic line F representing the communication path between boat 30f and boat 30c
As shown in , the communication path was opened to its maximum at position A4 at position iA. As it moves in the direction, its opening area is gradually reduced, and as a result, the conduit 15b shown in FIG.
Brake pressure is generated.

This brake pressure is then transferred from the pipe line 10b to the shuttle valve 2.
1 through the throttle 22 and the third pilot chamber 20
guided by. On the other hand, it passes through the constrictor 12b from the conduit 10b and is also guided to the pilot chamber 9b. Therefore, the pressures in the pilot chambers 9b and 20 at both ends of the spool 8b are the same, and the spool 8b is at the neutral position A only by the force of the spring 24b.

move in the direction. At this time, the speed at which the spool 8b moves is determined by the flow rate of oil sucking and discharging through the throttle 22.12b. When the spool 8b begins to move to the neutral position Aa, brake pressure is generated in the conduit 16b by narrowing the return passage from the conduit 16b to the tank. That is,
The brake force acting on the travel motor 2 is controlled by the control valve 3.
By moving the spool 0 in the neutral direction, the spool 1
By constricting the return passage from 5b to the tank, conduit 1
Brake pressure transmitted from 5b and generated in conduit 16b;
There are two levels of brake pressure and brake pressure generated when the spool 8b of the counterbalance valve 7 moves in the neutral direction. Therefore, the throttle 2 of the spool of the control valve 30
5b and the throttles 22.12b of the pilot chamber 20.9b at both ends of the spool 8b of the counterbalance valve 7 are selected to optimal conditions, the shock when the traveling motor 2 stops can be suppressed by the two-stage brake pressure. Can be done.

Also, the spool of the control valve 30 is at position A in FIG.
On the way from position KA 3 to position K A 2, the hydraulic pump 1 moves between boat 30b and boat 30 as shown in the characteristic line.
Since the communicating path e is restricted, pressure oil is still being sent to the pipe 15a, and therefore the pressure is being transferred to the shuttle valve 21.
It has even been reported. From this, in reality, pipe line 15
When the brake pressure generated in b becomes higher than the pump pressure generated in conduit 15a, spool 8b of counterbalance valve 7 starts moving in the neutral direction. That is, the timing at which the brake pressure is generated by the spool of the control valve 30 and the counterbalance valve 7 are determined.
This causes a shift in the timing of the rise of the brake pressure generated by the spool 8b, and as a result, the brake pressure that stops the travel motor 2 can be generated for a long time, and from a different point of view, the shock when the travel motor 2 stops can be suppressed.

The operation of stopping the drive of the travel motor 2 as described above is performed in the same way even when the control valve 30 is switched from the right position A5 in FIG. 2 to the neutral position Ao.

In the embodiment configured as described above, even if one spool of the counterbalance valve 7 is returning to the neutral direction when the travel motor 2 is operated in reverse, the other spool of the counterbalance valve 7 is activated to prevent the rise of reverse drive pressure. Since cracking occurs midway, generation of high confinement pressure in the pipe lines 16a and 16b between the travel motor 2 and the counterbalance valve 7 can be prevented. This effect can be applied, for example, to a sudden reversal operation of the control valve 30, in which the timing of the rise of the reversal pressure in the conduit 15b is earlier than the return of the spool 8b to neutral, or a crawler slipping, in which the timing of the sudden reversal of the traveling motor 2 is earlier than the neutral return of the spool 8b. It will be noticeable.

Further, in this embodiment, as described above, when the traveling motor 2 is stopped, two levels of brake pressure can be obtained: the brake pressure by the spool of the control valve 30 and the brake pressure by the spool of the counterbalance valve 7. Since the timings at which these brake pressures are generated are shifted, a shock when the travel motor 2 is stopped can be suppressed.

Further, in this embodiment, meter-out control is possible, and metering during deceleration can be expanded.

Furthermore, in this embodiment, when the travel motor 2 is stopped, the brake is first applied by the spool of the control valve 30, so cavitation does not occur even if the spool of the counterbalance valve 7 is slowly returned to the neutral position.

In the above embodiment, the shuttle valve 21 is used as an example of the pressure selection means, but a check valve may be used in place of the shuttle valve 21.

<Effects of the Invention> Since the travel hydraulic circuit of the hydraulic excavator of the present invention is configured as described above, it is possible to prevent undesired confinement pressure from occurring in the conduit between the counterbalance valve and the travel motor. It can be prevented. Moreover, since the brake pressure can be generated by both the control valve and the counterbalance valve with different timings, it is possible to suppress shock when the traveling motor stops.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams showing one embodiment of the travel hydraulic circuit of a hydraulic excavator according to the present invention, in which FIG. 1 is an overall circuit diagram, FIG. 2 is an enlarged view showing a control valve, and FIG. The figure is the second
FIG. 4 is a characteristic diagram showing the relationship between the position A of the spool of the control valve and the opening area B, and FIG. 4 is a circuit diagram showing a traveling hydraulic circuit of a conventional hydraulic excavator. 1...Hydraulic pump, 2...Travel motor, 7...Counter balance valve, 8a, 8b...
...Spool, 9a, 9b...Pilot room, 10a, 10b...Entrance boat, lla,
llb...Exit boat, 12a, 12b, 22
．． 25a, 25 b ------- Diaphragm, 13a, 13
b--Check valve, 16a, 16b...
Conduit, 20...Third pilot room, 21...
...Shuttle valve (pressure selection means), 24a, 24b
... Spring, 30 ... Control valve. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) A travel motor, a control valve that controls the drive of this travel motor, a hydraulic pump that supplies drive pressure oil to the travel motor via this control valve, and a space between the travel motor and the control valve. first and second pilot chambers provided with the main circuit pressure guided through the throttle;
In addition, in the traveling hydraulic circuit of a hydraulic excavator equipped with a counterbalance valve having spools operated by pressure oil in both pilot chambers, the spool of the counterbalance valve is divided into two and formed to face both spools. A third pilot chamber and pressure selection means for selecting the high pressure side of the main circuit pressure and supplying the pressure to the third pilot chamber as pilot pressure are provided, and the control valve is connected to an open center spool. A traveling hydraulic circuit for a hydraulic excavator, characterized in that it has a motor port and a tank port that communicate through a throttle when in neutral.