JP3662676B2 - Hydraulic circuit of excavator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic circuit of a hydraulic excavator, and in particular, a hydraulic circuit that compensates for straightness of a hydraulic excavator (vehicle body) during simultaneous operation of a traveling and working switching valve (when a traveling motor and a working actuator are simultaneously driven). About.
[0002]
[Prior art]
In general, as shown in FIG. 4, for example, the hydraulic circuit of a hydraulic excavator has center bypass type switching of left and right traveling motors 20 and 22 on discharge lines 10a and 12a of a first pump 10 and a second pump 12, respectively. The valves 32 and 42 are directly connected, and the center bypass type switching valves 34 and 44 of the working actuator 24 (for example, the turning motor 24A, the boom cylinder 24B, the arm cylinder 24C, and the bucket cylinder 24D) are connected to the downstream side thereof. (34A to 34D, 44A to 44C) are connected between the first hydraulic system 30 and the second hydraulic system 40 connected in parallel via the parallel lines 35 and 45, respectively, and between the two hydraulic systems 30 and 40. The travel straight-advancing valve 52 is configured. In this case, the hydraulic excavator is configured to ensure straightness during simultaneous operation of the travel switching valve and the work switching valve.
[0003]
Reference numerals 36 and 46 in both hydraulic systems 30 and 40 indicate center bypass lines, respectively. In the merging block 50, a check valve 54 and an orifice 56 are interposed between the parallel line 35 and the first pump discharge line 10a. In the illustrated neutral position, the traveling straight valve 52 connects the first pump discharge line 10a and the parallel line 35 of the first hydraulic system, and also connects the second pump discharge line 12a and the center of the second hydraulic system. The configuration is such that the bypass line 46 is connected. On the other hand, when switching to the left side, the first pump discharge line 10a and the center bypass line 46 of the second hydraulic system are connected, and the second pump discharge line 12a and the parallel line 35 of the first hydraulic system are connected. It consists of the structure which connected. These operations will be described later.
[0004]
Therefore, according to such a configuration, when the travel switching valves 32 and 42 are first operated, the oil discharged from the first pump 10 and the second pump 12 is directly supplied to the left and right travel switching valves 32 and 42, respectively. Is done. That is, when the switching valves 32 and 42 are respectively switched to their operating positions (A), (B), (C) or (D), the pilot line 14d is blocked, but the pilot pump 14 in the line 14d Since the pilot pressure 14c upstream of the line 14d is connected to the tank 16, the pilot pressure does not rise, and the traveling straight valve 52 is held at the neutral position shown in the figure. Therefore, as described above, the discharge oil from the first pump 10 and the second pump 12 is directly supplied to the left and right travel switching valves 32 and 42 via the discharge lines 10a and 12a. That is, in this case, it is clear that the straight excavation of the hydraulic excavator is ensured if the discharge amounts of both pumps 10 and 12 are the same.
[0005]
Next, when the traveling switching valves 32 and 42 and the working switching valves 34 and 44 (one of them) are operated simultaneously, the oil discharged from the first pump 10 is supplied to the left and right traveling switching valves 32 and 42. Then, the discharge oil of the second pump 12 is supplied to the work switching valves 34 and 44 (any one), and at the same time, the surplus oil further joins the discharge oil of the first pump 10. . That is, if the operation switching valves 34 and 44 (one of them) are operated simultaneously during traveling (when the traveling switching valves 32 and 42 are operated), the pilot line 14c is blocked. Since the pilot pressure acts on the traveling straight valve 52 via the orifices 14a and 14b and the pilot line 14d, and this is switched to the position on the left side of the drawing, as described above, the discharge oil of the first pump 10 While being supplied directly from the discharge line 10 a to the left travel switching valve 32, it is also supplied to the right travel switching valve 42 via the travel straight valve 52 and the center bypass line 46.
[0006]
On the other hand, the discharge oil of the second pump 12 is supplied directly from the discharge line 10a to the parallel line 45, and at the same time, supplied to the parallel line 35 of the first hydraulic system via the travel straight valve 52. . That is, the discharge oil is supplied to the operation switching valves 34 and 44, and the surplus oil is further supplied to the pump discharge line 10a via the check valve 54 and the orifice 56. That is, the surplus oil merges into the discharged oil of the first pump 10. Thereby, the straightness of the hydraulic excavator is secured, and in this case, the surplus oil of the second pump 12 joins the discharged oil of the first pump 10, so that the traveling speed of the hydraulic excavator is also possible. Maintained at high speed. The merging block 50 is actually provided to form speed increase control communication lines 58a, 58b, and 58c of the arm cylinder 24C and the boom cylinder 24B.
[0007]
Incidentally, when the operation switching valves 34 and 44 (only) are operated, the oil discharged from the first pump 10 and the second pump 12 is supplied only to the operation switching valves 34 and 44. That is, it is clear that the discharged oil is not involved in the traveling of the hydraulic excavator.
[0008]
Thus, according to this type of hydraulic circuit, the straightness of the hydraulic excavator is ensured not only when the traveling switching valve alone is operated alone, but also when the working switching valve is operated simultaneously. The In addition, during the simultaneous operation, the oil discharged from the first pump and the second pump merges, so that the straight traveling speed can be set as high as possible. In addition, in this case, the deceleration shock to the driver can be mitigated from the decrease in the traveling speed reduction degree at the time of the simultaneous operation.
[0009]
[Problems to be solved by the invention]
However, the hydraulic circuit of the conventional hydraulic excavator still has the following problems.
[0010]
That is, in the conventional hydraulic circuit, as described above, the straight excavation of the hydraulic excavator is not only during the single operation of only the travel switching valve, but also during the simultaneous operation of this and the switching valve for work. Secured. However, the straight traveling speed during the simultaneous operation is set as high as possible because the discharge oils of the first pump and the second pump merge, but varies depending on the operation of the work switching valve. It was.
[0011]
That is, in the conventional hydraulic circuit, when the working actuator is driven while the hydraulic excavator is traveling, the traveling speed of the hydraulic excavator fluctuates between increasing and decreasing in accordance with the start and stop of the working actuator and the driving load therebetween. It was. For this reason, not only the acceleration / deceleration shock to the driver occurs but also the workability of the actuator is lowered.
[0012]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to drive straight ahead without changing the traveling speed of the hydraulic excavator when simultaneously operating the traveling switching valve and the working switching valve, for example, when driving the working actuator during traveling of the hydraulic excavator. An object of the present invention is to provide a hydraulic circuit of a hydraulic excavator that can be kept constant without impairing the performance.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the hydraulic circuit of the hydraulic excavator according to the present invention directly connects the center bypass type switching valve of the left and right traveling motors to the discharge lines of the first pump and the second pump, respectively. A first hydraulic system and a second hydraulic system in which a center bypass type switching valve of a working actuator is connected in parallel on the downstream side, and a hydraulic circuit in which a traveling straight valve is interposed between the two hydraulic systems. When the operation switching valve is operated, the oil discharged from the first pump and the second pump is supplied to the left and right traveling switching valve, respectively, and when the operation switching valve is operated, the oil discharged from the first pump and the second pump is supplied. The first pump discharge oil is supplied to the left / right travel switching valve and the second pump discharge oil is supplied to the work switching valve. And simultaneously feeding, in a hydraulic circuit of a hydraulic excavator that is configured to join the oil discharged surplus oil further said first pump,
A traveling independent valve that operates in the traveling independent mode of the hydraulic excavator is provided, while each of the first hydraulic system and the second hydraulic system has a first selector that operates in the traveling independent mode on the most downstream side of the center bypass line. A valve and a second selector valve are provided, and their upstream sides are connected to the travel independent valve via a first side bypass line and a second side bypass line, respectively, for traveling and working in the travel independent mode. When the switching valve is operated, the discharge oil of the first pump is supplied to the left / right travel switching valve, and the discharge oil of the second pump is supplied to the work switching valve.
[0014]
In this case, the selector valve of the first hydraulic system is switched by the maximum operation signal pressure of the travel switching valve in the travel independent mode to close the center bypass line, and the selector valve of the second hydraulic system is travel independent. In the mode, the center bypass line is closed by switching with the maximum operation signal pressure of the work switching valve, and the traveling independent valve is switched by the traveling independent signal pressure in the traveling independent mode to switch the first pump discharge line to the first In addition to being connected to the side bypass line, the parallel line of the first hydraulic system can be connected to the second side bypass line.
[0015]
Further, when the travel straight valve is neutral, the discharge line of the first pump is connected to the parallel line of the first hydraulic system, and the discharge line of the second pump is switched for travel of the second hydraulic system. Connected to the valve supply line and the center bypass line, and at the time of switching, the discharge line of the first pump is connected to the travel switching valve supply line of the second hydraulic system and the discharge line of the second pump is connected to the second pump line. It is configured to connect to the parallel line of the first hydraulic system and further block the center bypass line of the second hydraulic system, and to switch from the neutral position to the switching position by the travel independent signal. Can be configured.
[0016]
Further, the travel switching valve supply line and the center bypass line of the second hydraulic system are connected via a check valve, and when the travel straight valve is neutral, the discharge line of the first pump is connected to the first pump line. The second pump discharge line is connected to the second hydraulic system center bypass line, and the first pump discharge line is connected to the second hydraulic system parallel line. Connected to the travel switching valve supply line, the discharge line of the second pump is connected to the parallel line of the first hydraulic system, and the center bypass line of the second hydraulic system is further blocked. be able to.
[0017]
In the present invention, when the driver sets the traveling independent mode of the hydraulic excavator and operates the switching valve, the discharge oil of the first pump is supplied to the left and right traveling switching valve by the same amount, while the second pump The pump discharge oil is supplied only to the work switching valve.
[0018]
That is, according to the present invention, even when the working actuator is driven during traveling of the hydraulic excavator, the traveling speed of the hydraulic excavator can be kept constant as desired by the driver. In other words, it is possible to prevent acceleration / deceleration shocks to the driver, a decrease in actuator workability, and the like.
[0019]
【Example】
Next, embodiments of a hydraulic circuit of a hydraulic excavator according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional configuration shown in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0020]
In FIG. 1, the hydraulic circuit of the hydraulic excavator according to the present invention is basically the same as the conventional configuration (FIG. 4). Therefore, although it overlaps, in order to make an understanding easy, it demonstrates briefly again. The hydraulic circuit of the present invention basically includes center bypass type switching valves 32 and 42 of left and right traveling motors 20 and 22 on the discharge lines 10a and 12a of the first pump 10 and the second pump 12, respectively. Configure by connecting directly. On the downstream side, the center bypass type switching valves 34 and 44 (34A to 34D and 44A to 44C) of the working actuator 24 (24A,... 24D) are connected in parallel via the parallel lines 35 and 45, respectively. The first hydraulic system 30 and the second hydraulic system 40, and a hydraulic circuit in which a traveling straight valve 52 is interposed between the hydraulic systems 30 and 40.
[0021]
The traveling straight valve 52 is connected to the first pump discharge line 10a and the parallel line 35 of the first hydraulic system at the illustrated neutral position (in this case, the illustrated neutral position of the traveling independent valve 60 described later). And the second pump discharge line 12a and the center bypass line 46 of the second hydraulic system are connected. On the other hand, at the time of switching to the left position, the first pump discharge line 10a and the center bypass line 46 of the second hydraulic system are connected, and the second pump discharge line 12a and the parallel line 35 of the first hydraulic system are connected. It consists of the structure which connects.
[0022]
Therefore, according to such a configuration, in the operation, as in the conventional case described above, first, when the travel switching valves 32 and 42 (only) are operated, the first pump 10 and the second pump 12 are operated. The discharged oil is directly supplied to the left and right traveling switching valves 32 and 42 (only), respectively. Further, when the operation switching valves 34 and 44 (only) are operated, the discharge oil of the first pump 10 and the second pump 12 is supplied to the operation switching valves 34 and 44 (only).
[0023]
On the other hand, when the travel switching valves 32, 42 and the work switching valves 34, 44 are operated simultaneously, the oil discharged from the first pump 10 is supplied to the left and right travel switching valves 32, 42, and The discharged oil is supplied to the work switching valves 34 and 44, and at the same time, the surplus oil further merges with the discharged oil of the first pump 10. That is, according to this type of hydraulic circuit, the straightness of the hydraulic excavator is ensured not only when the travel switching valve is operated alone but also when the travel switching valve is operated simultaneously. In addition, during this simultaneous operation, there is also an advantage that the straight traveling speed can be set as high as possible.
[0024]
However, although this conventional hydraulic circuit has the characteristics as described above, on the other hand, when the working actuator is driven while the hydraulic excavator is traveling, the traveling speed fluctuates corresponding to the load variation of the actuator. Have the disadvantages. Therefore, as described above, the object of the present invention is intended to overcome this difficulty.
[0025]
That is, in the present invention, in the above configuration, the merging block 50 is further provided with a traveling independent valve 60 that operates in a traveling independent mode that defines the traveling of the hydraulic excavator. On the other hand, in the first hydraulic system 30 and the second hydraulic system 40, the first selector valve 37 and the second selector valve that operate in the travel independent mode are provided on the most downstream side of the center bypass lines 36 and 46, respectively. 47, and upstream sides 36a and 46a thereof are connected to the traveling independent valve 60 via the first side bypass line 38 and the second side bypass line 48, respectively. Thus, when the travel switching valves 32 and 42 and the work switching valves 34 and 44 are operated in the travel independent mode, the discharge oil of the first pump 10 is supplied to the left and right travel switching valves 32 and 42, and the second The oil discharged from the pump 12 is supplied to the work switching valves 34 and 44.
[0026]
That is, the traveling independent valve 60 is connected to the illustrated neutral position via the solenoid valve 62 and the pilot line 62a (in this neutral position, the parallel line 35 of the first hydraulic system via the check valve 60a and the orifice 60b). It is possible to switch from the first pump discharge line 10a) to the left operation position (set to the traveling independent mode). At the time of this switching, the straight travel valve 52 is also switched from the neutral position shown in the drawing to the left operating position via the shuttle valve 64 and the pilot line 62b. Further, the first selector valve 37 and the second selector valve 47 are also connected via means 38 and 48 for outputting the maximum signal pressure of the travel switching valves 32 and 42 and the maximum signal pressure of the work switching valves 34 and 44, respectively. Thus, the illustrated opening position is switched to the left closing position.
[0027]
Accordingly, when the travel switching valves 32 and 42 are operated in the travel independent mode, the first pump discharge line 10a and the second center bypass line are operated regardless of the positions of the work switching valves 34 and 44. 46, and the center bypass line 36 of the first hydraulic system and the center bypass line 46 of the second hydraulic system are blocked together, so that the discharged oil of the first pump 10 can be Directly supplied to the travel switching valves 32, 42 in half.
[0028]
On the other hand, the discharge oil of the second pump 12 is supplied to the work switching valves 34 and 44 and does not join the discharge line 10 a of the first pump 10.
[0029]
As described above, in the hydraulic circuit of the present invention, even when the traveling switching valve and the working switching valve are operated simultaneously (by setting the circuit in the traveling independent mode) as desired by the driver (during traveling of the hydraulic excavator). Even when the working actuator is driven), the traveling speed of the hydraulic excavator can be kept constant without changing (of course, without impairing the straight traveling performance).
[0030]
In such a configuration, if it is attempted to steer the hydraulic excavator by operating only the travel switching valve 32 (left travel motor 20) of the first hydraulic system 30 in the travel independent mode, In this case, the travel switching valve 42 of the second hydraulic system 40 is in the neutral position, and therefore, the discharge oil from the first pump 10 is discharged from the first pump discharge line 10a, the travel straight valve 52, the second Are discharged to the tank 16 through the center bypass line 46a and the tank line 59. Therefore, the left traveling motor 20 is not driven. For this reason, the following means are added in the present invention.
[0031]
That is, in FIG. 2, the traveling straight valve 52 connects the discharge line 10 a of the first pump 10 to the parallel line 35 of the first hydraulic system 30 at the neutral time (position shown in the figure). The discharge line 12 a of the second pump 12 is connected to the travel switching valve supply line 49 and the center bypass line 46 of the second hydraulic system 40. On the other hand, when switching to the left position, the discharge line 10a of the first pump 10 is connected to the travel switching valve supply line 49 of the second hydraulic system 40, and the discharge line 12a of the second pump 12 is connected. , Connected to the parallel line 35 of the first hydraulic system 30, and further configured to block the center bypass line 46 of the second hydraulic system 40.
[0032]
According to such a configuration, even when only the left travel switching valve 32 is operated in the travel independent mode and when the travel straight travel valve 52 is switched to the left, the first pump discharge line 10a can be connected to the second center bypass line. Since it is not connected to 46, it is obvious that the oil discharged from the first pump 10 is supplied to the left traveling motor 20 (travel switching valve 32).
[0033]
In the embodiment shown in FIG. 3, the travel switching valve supply line 49 of the second hydraulic system 40 and the center bypass line 46 are connected via a check valve 49a. As a result, when the traveling straight valve 52 is neutral, the discharge line 10a of the first pump 10 is connected to the parallel line 35 of the first hydraulic system 30, and the discharge line 12a of the second pump 12 is Connected to the center bypass line 46 of the second hydraulic system 40. On the other hand, at the time of switching, the discharge line 10a of the first pump 10 is connected to the travel switching valve supply line 49 of the second hydraulic system 40, and the discharge line 12a of the second pump 12 is connected to the first It is connected to the parallel line 35 of the hydraulic system 30 and further configured to block the center bypass line 46 of the second hydraulic system 40. That is, in this embodiment, it is obvious that substantially the same operation as in the above embodiment (FIG. 2) is exhibited.
[0034]
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention.
[0035]
【The invention's effect】
As described above, the hydraulic circuit of the hydraulic excavator according to the present invention includes the first hydraulic system and the second hydraulic system, and the hydraulic circuit in which the traveling straight valve is interposed between the two hydraulic systems. A travel independent valve that operates in the travel independent mode is provided, while the first hydraulic system and the second hydraulic system have a first selector valve and a second hydraulic system that operate in the travel independent mode on the most downstream side of the center bypass line, respectively. 2 selector valves are connected to the travel independent valve via the first side bypass line and the second side bypass line, respectively, and the travel and work switching valve in the travel independent mode is provided. During operation, the oil discharged from the first pump is supplied to the left / right travel switching valve, and the oil discharged from the second pump is supplied to the work switching valve. Thus, if the hydraulic excavator is set to the travel independent mode, the discharge oil of the first pump can be supplied only to the left and right travel switching valve, while the discharge oil of the second pump can be supplied only to the work switching valve. .
[0036]
That is, according to the present invention, the traveling speed of the hydraulic excavator can be kept constant even if the working actuator is driven while the hydraulic excavator is traveling. In other words, an acceleration / deceleration shock to the driver, a decrease in actuator workability, and the like can be reliably prevented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a hydraulic circuit of a hydraulic excavator according to the present invention.
FIG. 2 is a circuit diagram showing another embodiment of the hydraulic circuit of the hydraulic excavator according to the present invention.
FIG. 3 is a circuit diagram showing still another embodiment of the hydraulic circuit of the excavator according to the present invention.
FIG. 4 is a circuit diagram showing a hydraulic circuit of a conventional excavator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 1st pump 10a 1st pump discharge line 12 2nd pump 12a 2nd pump discharge line 14 Pilot pump 16 Tank 20, 22 Traveling motors 24A-24D Work actuator 30 1st hydraulic system 32 1st Switching valve for travel 34A to 34D Switching valve for operation 35 Parallel line 36 of first hydraulic system Center bypass line 37 of first hydraulic system First selector valve 38 First side bypass line 40 Second hydraulic system 42 1st switching valve 44A-44D Working switching valve 45 Parallel line 46 of 2nd hydraulic system Center bypass line 47 of 2nd hydraulic system 2nd selector valve 48 2nd side bypass line 49 Switching valve supply line 49a Check valve 50 Junction block 52 Travel straight valve 60 Travel independent valve 62 Electromagnetic Valve 64 Shuttle valve

Claims (4)

A center bypass type switching valve of the left and right traveling motor is directly connected to the discharge lines of the first pump and the second pump, respectively, and a center bypass type switching valve of the working actuator is connected in parallel downstream thereof. 1 hydraulic system and a second hydraulic system, and a hydraulic circuit in which a traveling straight valve is interposed between the two hydraulic systems, and discharge oil of the first pump and the second pump when the traveling switching valve is operated. Are respectively supplied to the left and right traveling switching valves, and when the working switching valve is operated, the discharge oil of the first pump and the second pump is supplied to the working switching valve, while the traveling and working switching valves are operated simultaneously. Sometimes the discharge oil of the first pump is supplied to the left / right travel switching valve, the discharge oil of the second pump is supplied to the work switching valve, and at the same time, the excess oil is further combined with the discharge oil of the first pump. In the hydraulic circuit of a hydraulic excavator that is configured to,
A traveling independent valve that operates in the traveling independent mode of the hydraulic excavator is provided, while each of the first hydraulic system and the second hydraulic system has a first selector that operates in the traveling independent mode on the most downstream side of the center bypass line. A valve and a second selector valve are provided, and their upstream sides are connected to the travel independent valve via a first side bypass line and a second side bypass line, respectively, for traveling and working in the travel independent mode. The hydraulic excavator is configured so that when the switching valve is operated, the discharge oil of the first pump is supplied to the switching valve for left and right traveling, and the discharge oil of the second pump is supplied to the switching valve for work. Hydraulic circuit. The selector valve of the first hydraulic system is switched by the maximum operation signal pressure of the travel switching valve in the travel independent mode to close the center bypass line, and the selector valve of the second hydraulic system is used for work in the travel independent mode. The center bypass line is closed by switching with the maximum operation signal pressure of the switching valve, and the traveling independent valve is switched with the traveling independent signal pressure in the traveling independent mode to change the discharge line of the first pump to the first side bypass line. 2. The hydraulic circuit for a hydraulic excavator according to claim 1, wherein the hydraulic circuit is connected and the parallel line of the first hydraulic system is connected to the second side bypass line. When the traveling straight valve is neutral, the discharge line of the first pump is connected to the parallel line of the first hydraulic system, and the discharge line of the second pump is connected to the switching valve supply line for traveling of the second hydraulic system. And the center bypass line, at the time of switching, the discharge line of the first pump is connected to the travel switching valve supply line of the second hydraulic system, and the discharge line of the second pump is connected to the first hydraulic pressure line. It is configured to connect to the parallel line of the system and further block the center bypass line of the second hydraulic system, and to switch from the neutral position to the switching position by the travel independent signal. The hydraulic circuit of the hydraulic excavator according to claim 1 formed. The travel switching valve supply line of the second hydraulic system and the center bypass line are connected via a check valve, and when the travel straight valve is neutral, the discharge line of the first pump is connected to the first hydraulic pressure line. The second pump discharge line is connected to the parallel line of the system and the center bypass line of the second hydraulic system, and at the time of switching, the discharge line of the first pump is used for the traveling of the second hydraulic system. It is configured to connect to the switching valve supply line, connect the discharge line of the second pump to the parallel line of the first hydraulic system, and further block the center bypass line of the second hydraulic system. The hydraulic circuit of the hydraulic excavator according to Item 1.

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