JP6873726B2 - Hydraulic system - Google Patents

Description

The present invention relates to a hydraulic system including a traveling motor and an actuator for driving a dozer.

As a hydraulic system including a traveling motor and a dozer cylinder for raising and lowering a dozer, for example, a device disclosed in Patent Document 1 is known. This device includes two main pumps that supply pressure oil (that is, hydraulic oil) to a pair of traveling hydraulic motors, and a dozer pump that supplies pressure oil to a dozer cylinder.

Japanese Unexamined Patent Publication No. 2001-262630

By providing the pump used for driving the dozer cylinder separately from the pump used for driving the traveling motor as in the device of Patent Document 1, the driving of the dozer cylinder does not affect the driving of the traveling motor. However, since it is necessary to provide a dedicated pump for driving the dozer cylinder, the cost increases.

On the other hand, as a method of using a common pump for driving the traveling motor and driving the dozer, two pumps are used, and the hydraulic oil from one pump is supplied to one traveling motor while the hydraulic oil from the other pump is supplied. Is conceivable as a method of supplying the oil to the other traveling motor and the dozer cylinder. However, in this method, when the dozer cylinder is driven, there is a difference in the supply amount of hydraulic oil between the left and right traveling motors, which makes it difficult to travel straight and the operability is poor.

As another method of using a common pump for driving the traveling motor and driving the dozer, a method using a traveling switching valve can be considered. The traveling switching valve is a valve that switches the supply destination of hydraulic oil from each pump according to the drive mode. For example, when the dozer is not driven and only the traveling motor is driven, the hydraulic oil is supplied from the first pump to one traveling motor while the hydraulic oil is supplied from the second pump to the other traveling motor. The traveling switching valve switches the hydraulic circuit. On the other hand, when the traveling motor is driven and the dozer is driven at the same time, the hydraulic oil is supplied from the first pump to both traveling motors and from the second pump to the actuator for driving the dozer. , The traveling switching valve switches the hydraulic circuit.

By using such a traveling switching valve, a dedicated pump for driving the dozer becomes unnecessary, but there are a state in which two traveling motors are driven by two pumps and a state in which two traveling motors are driven by one pump. It is necessary to switch the hydraulic circuit between. When switching the hydraulic circuit in this way, an impact (that is, switching shock) associated with the change in the state of pump assignment to the traveling motor acts on the operator, and each time the hydraulic circuit is switched, the operator feels uncomfortable. Brought to you. In particular, when it is necessary to switch the hydraulic circuit by the traveling switching valve each time the ascending drive and the descending drive of the dozer are switched, the traveling speed changes and the switching shock occurs due to the switching of the hydraulic circuit, so that the operability is improved. Very bad.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic system capable of realizing comfortable operability while suppressing costs.

One aspect of the present invention is a first hydraulic pump and a second hydraulic pump that supply hydraulic oil, a first traveling motor and a second traveling motor that are driven according to the supplied hydraulic oil, and a hydraulic oil that is supplied. The circuit switching unit includes a first actuator that drives the dozer according to the situation, and a circuit switching unit that changes the hydraulic circuit to switch the supply destination of hydraulic oil from the first hydraulic pump and the second hydraulic pump. The first circuit state in which the hydraulic oil is supplied from the first hydraulic pump to the first traveling motor and the first actuator, and the hydraulic oil is supplied from the second hydraulic pump to the second traveling motor and the first actuator, and from the first hydraulic pump. A second circuit state in which hydraulic oil is supplied to the first traveling motor, hydraulic oil is supplied from the second hydraulic pump to the second traveling motor, and hydraulic oil is not supplied from the first hydraulic pump and the second hydraulic pump to the first actuator. And, regarding the hydraulic system that changes the hydraulic circuit.

The circuit switching unit is a hydraulic circuit so that the flow rate of the hydraulic oil supplied to the first traveling motor becomes equal to the flow rate of the hydraulic oil supplied to the second traveling motor in each of the first circuit state and the second circuit state. May be changed.

The hydraulic system further includes an instruction receiving unit that receives operation instructions, and the circuit switching unit is a mode in which the operation instructions received by the instruction receiving unit drive the first actuator while driving the first traveling motor and the second traveling motor. When the hydraulic circuit is set to the first circuit state and the operation instruction received by the instruction receiving unit corresponds to a mode in which the first traveling motor and the second traveling motor are driven but the first actuator is not driven. The hydraulic circuit may be in the second circuit state.

The hydraulic system is a second actuator different from the first actuator, further including a second actuator driven according to the supplied hydraulic oil, the circuit switching unit includes a traveling switching valve, and the traveling switching valve is a traveling switching valve. The first switching state in which the hydraulic oil is supplied from the first hydraulic pump to at least the first traveling motor and the hydraulic oil is supplied from the second hydraulic pump to at least the second traveling motor, and the first traveling motor and the first traveling motor from the second hydraulic pump. 2 The hydraulic circuit is set to the second switching state in which the hydraulic oil is supplied from the first hydraulic pump to at least the second actuator while supplying the hydraulic oil to the traveling motor, and the hydraulic circuit is in either the first circuit state or the second circuit state. In this case, the traveling switching valve is put into the first switching state, the hydraulic circuit is supplied with hydraulic oil from the second hydraulic pump to the first traveling motor and the second traveling motor, and the hydraulic oil is supplied to the first actuator. Instead, the traveling switching valve may be put into the second switching state when the third circuit state in which the hydraulic oil is supplied from the first hydraulic pump to the second actuator is set.

The hydraulic system further includes an instruction receiving unit that receives an operation instruction, and in the circuit switching unit, the operation instruction received by the instruction receiving unit drives the first traveling motor and the second traveling motor, and drives the first actuator. When corresponding to the first drive mode in which the second actuator is driven or not driven, the hydraulic circuit is set to the first circuit state, and the operation instruction received by the instruction receiving unit drives the first traveling motor and the second traveling motor. However, in the case of corresponding to the second drive mode in which the first actuator and the second actuator are not driven, the hydraulic circuit is set to the second circuit state, and the operation instruction received by the instruction receiving unit is the first traveling motor and the second traveling. When the third drive mode in which the motor is driven, the first actuator is not driven, and the second actuator is driven is supported, the hydraulic circuit may be changed so that the hydraulic circuit is in the third circuit state. ..

The hydraulic system is a logic system for switching the traveling switching valve between the first switching state and the second switching state according to the driving states of the first traveling motor, the second traveling motor, the first actuator, and the second actuator. May be further provided.

The logic system has a hydraulic logic circuit, and the pressure of the pressure oil in the hydraulic logic circuit changes according to the driving state of the first traveling motor, the second traveling motor, the first actuator, and the second actuator, and the logic system. May switch the traveling switching valve between the first switching state and the second switching state based on the pressure oil in the hydraulic logic circuit.

The logic system has an electric signal logic circuit, and the signal flowing through the electric signal logic circuit changes according to the driving state of the first traveling motor, the second traveling motor, the first actuator and the second actuator, and the logic system is , The traveling switching valve may be switched between the first switching state and the second switching state based on the signal flowing through the electric signal logic circuit.

The circuit switching unit includes a direction switching valve for the first traveling motor that switches the supply / absence of hydraulic oil to the first traveling motor and the supply direction of the hydraulic oil, and the presence / absence of supply of the hydraulic oil to the second traveling motor and the supply of the hydraulic oil. A direction switching valve for the second traveling motor that switches the direction, and a direction switching valve for the first actuator that switches the supply / absence of hydraulic oil to the first actuator and the supply direction of the hydraulic oil may be included.

According to the present invention, it is possible to provide a hydraulic system capable of realizing comfortable operability while suppressing costs.

FIG. 1 is a schematic view showing a circuit configuration of a typical flood control system using a traveling switching valve, and shows a state before supplying hydraulic oil to a first actuator composed of a dozer cylinder for driving a dozer. Shown. FIG. 2 is a schematic view showing a circuit configuration of a typical flood control system using a traveling switching valve, and shows a state in which hydraulic oil is supplied to the first actuator. FIG. 3 is a schematic view showing a circuit configuration of a hydraulic system according to an embodiment of the present invention, and shows a state in which the first actuator is not driven. FIG. 4 is a schematic view showing a circuit configuration of a hydraulic system according to an embodiment of the present invention, and shows a state in which the first actuator is driven. FIG. 5 is a schematic view showing a circuit configuration of a hydraulic system according to an embodiment of the present invention, in which a first traveling motor and a second traveling motor are driven, a first actuator is not driven, and another actuator is driven. Indicates the state to be done. FIG. 6 is a block diagram showing the relationship between the instruction receiving unit, the direction switching valve, and various actuators. FIG. 7 is a flowchart showing an outline of the determination flow of the first circuit state (see FIG. 4) and the second circuit state (see FIG. 3). FIG. 8 is a flowchart showing an outline of a flow for determining a switching state of the traveling switching valve. FIG. 9 is a table showing the drive states of various actuators, the state of the traveling switching valve, and the state of the hydraulic circuit in the first drive mode, the second drive mode, and the third drive mode. FIG. 10 is a block diagram showing the relationship between the logic system and the traveling switching valve. FIG. 11 is a diagram showing an example of a hydraulic logic circuit of a logic system using hydraulic logic. FIG. 12 is a diagram showing an example of an electric signal logic circuit of a logic system using electric signal logic. FIG. 13 is a circuit diagram showing an example in which the hydraulic system according to the embodiment of the present invention is applied to a hydraulic excavator including a dozer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The hydraulic system described below is a system for driving two traveling motors and a dozer cylinder (that is, a first actuator) by two hydraulic pumps, and while keeping costs down, discomfort during operation such as switching shocks. Can be reduced to achieve comfortable operability.

First, a "typical hydraulic system using a traveling switching valve" to be compared with the embodiment of the present invention will be described.

FIG. 1 is a schematic view showing a circuit configuration of a typical hydraulic system 10 using a traveling switching valve 42, before supplying hydraulic oil to a first actuator 31 composed of a dozer cylinder for driving a dozer. Indicates the state of. FIG. 2 is a schematic view showing a circuit configuration of a typical flood control system 10 using a traveling switching valve 42, and shows a state in which hydraulic oil is supplied to the first actuator 31.

The hydraulic system 10 shown in FIGS. 1 and 2 includes a first hydraulic pump 11 and a second hydraulic pump 12. The oil passage from the first hydraulic pump 11 is branched into two oil passages, and one oil passage is connected to the second tandem passage 25. Further, the oil passage from the second hydraulic pump 12 is branched into two oil passages, and one oil passage is connected to the first parallel passage 26.

The other oil passage extending from the first hydraulic pump 11 and the other oil passage extending from the second hydraulic pump 12 are connected to the traveling switching valve 42, and the connected oil passage is changed according to the switching state of the traveling switching valve 42. Will be done. That is, the traveling switching valve 42 can be switched to either the first switching state 42a or the second switching state 42b, and changes the hydraulic circuit 13. When the traveling switching valve 42 is placed in the second switching state 42b, the other oil passage extending from the first hydraulic pump 11 is connected to the first tandem passage 24 via the traveling switching valve 42, and is connected to the first tandem passage 24 from the second hydraulic pump 12. The other oil passage extending is connected to the second parallel passage 27 via the traveling switching valve 42. On the other hand, when the traveling switching valve 42 is placed in the first switching state 42a, the other oil passage extending from the first hydraulic pump 11 is connected to the second parallel passage 27 via the traveling switching valve 42, and the second hydraulic pump The other oil passage extending from 12 is connected to the first tandem passage 24 via the traveling switching valve 42.

At least one of the first actuator 31 and other actuators in which the first traveling motor 21 and the second traveling motor 22 are driven and connected to the first hydraulic pump 11 and the second hydraulic pump 12 via the hydraulic circuit 13. When the pump is driven, the traveling switching valve 42 is placed in the second switching state 42b. In this case, the hydraulic oil from the first hydraulic pump 11 is supplied to the first traveling motor 21 via the first tandem passage 24, and the hydraulic oil from the first hydraulic pump 11 is supplied to the first traveling motor 21 through the second tandem passage 25. It is supplied to the traveling motor 22. Further, the hydraulic oil from the second hydraulic pump 12 is supplied to the first actuator 31 via the second parallel passage 27, and the hydraulic oil from the second hydraulic pump 12 is supplied to the first parallel passage 26 and / or the second parallel passage 27. It is supplied to other actuators via.

On the other hand, the first actuator 31 and other actuators in which the first traveling motor 21 and the second traveling motor 22 are driven and are connected to the first hydraulic pump 11 and the second hydraulic pump 12 via the hydraulic circuit 13 When neither is driven, the traveling switching valve 42 is placed in the first switching state 42a. In this case, the hydraulic oil from the second hydraulic pump 12 is supplied to the first traveling motor 21 via the first tandem passage 24, and the hydraulic oil from the first hydraulic pump 11 is supplied to the first traveling motor 21 via the second tandem passage 25. It is supplied to the traveling motor 22.

Further, the direction switching valves 41a, 41b, and 41c are assigned to each of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the other actuators. Each direction switching valve 41a, 41b, 41c is supplied with hydraulic oil to the assigned actuators (that is, the first traveling motor 21, the second traveling motor 22, the first actuator 31, or another actuator) and the supply of hydraulic oil. The direction can be switched, and the hydraulic oil supply path can be narrowed to adjust the hydraulic oil supply amount.

Each of the directional control valves 41a, 41b, 41c shown in FIGS. 1 and 2 is configured as an 8-port 3-position hydraulic pilot actuating valve having 8 ports and capable of taking 3 positions, and the center position is the hydraulic oil. The neutral position (that is, the non-driving position) at which the supply of the hydraulic oil is stopped is indicated, and the positions at both ends indicate the driving position at which the hydraulic oil is supplied. In FIGS. 1 and 2, the right end position indicates the forward drive position, and the left end position indicates the reverse drive position. Therefore, in FIG. 1, the directional switching valve 41a assigned to the first traveling motor 21 and the directional switching valve 41b assigned to the second traveling motor 22 are placed at the forward drive positions and assigned to the first actuator 31. The state in which 41c is placed in the neutral position is shown. On the other hand, in FIG. 2, the directional switching valve 41a assigned to the first traveling motor 21, the directional switching valve 41b assigned to the second traveling motor 22, and the directional switching valve 41c assigned to the first actuator 31 are in the forward drive positions. The state of being placed in is shown. Note that in FIGS. 1 and 2, the illustration of the directional control valve assigned to the other actuator is omitted.

The hydraulic oil discharged from the first traveling motor 21, the second traveling motor 22, the first actuator 31, and other actuators flows into the tank passage 29 via the direction switching valves 41a, 41b, and 41c, and flows from the tank passage 29. It is discharged to the discharge tank 30. Further, each of the first tandem passage 24, the second tandem passage 25, the first parallel passage 26, and the second parallel passage 27 is connected to the tank passage 29 at the most downstream position.

As described above, in the typical hydraulic system 10 using the traveling switching valve 42 described above, one hydraulic pump (the first hydraulic pump 11 in FIGS. 1 and 2) is used to drive the dozer up and down while traveling. The hydraulic oil is supplied to the first traveling motor 21 and the second traveling motor 22. On the other hand, when driving only the first traveling motor 21 and the second traveling motor 22 without driving the first actuator 31 and other actuators, the two hydraulic pumps are transferred from the two hydraulic pumps to the first traveling motor 21 and the second traveling motor 22. Hydraulic oil is supplied. Therefore, when the drive and non-drive of the dozer are finely switched, the state of the traveling switching valve 42 is also finely switched, and a switching shock is generated each time the drive and non-drive of the dozer are switched, resulting in very poor operability.

On the other hand, according to the following hydraulic system 10 according to the embodiment of the present invention, two traveling motors and a dozer cylinder are driven by two hydraulic pumps, and the occurrence of such a switching shock is reduced, resulting in low cost. It is possible to achieve both the realization of comfortable operability and the realization of comfortable operability.

FIG. 3 is a schematic view showing the circuit configuration of the hydraulic system 10 according to the embodiment of the present invention, and shows a state in which the first actuator 31 configured by the dozer cylinder is not driven. FIG. 4 is a schematic view showing the circuit configuration of the hydraulic system 10 according to the embodiment of the present invention, and shows a state in which the first actuator 31 configured by the dozer cylinder is driven. 3 and 4 are diagrams showing a circuit configuration when an actuator other than the first traveling motor 21, the second traveling motor 22, and the first actuator 31 (that is, the “second actuator” described later) is not driven. is there. A case where an actuator other than the first traveling motor 21, the second traveling motor 22, and the first actuator 31 is driven will be described later (see FIG. 5 and the like).

The hydraulic system 10 shown in FIGS. 3 and 4 also has a first hydraulic pump 11 and a second hydraulic pump 12 for supplying hydraulic oil, and a first traveling motor 21 and a second traveling motor driven according to the supplied hydraulic oil. A circuit that switches the supply destination of the hydraulic oil from the first hydraulic pump 11 and the second hydraulic pump 12 by changing the hydraulic circuit, the motor 22, the first actuator 31 that drives the dozer according to the supplied hydraulic oil. A switching unit 40 is provided. The first hydraulic pump 11 and the second hydraulic pump 12 have the same output, and the hydraulic oil of the same flow rate is supplied to the oil passage from the first hydraulic pump 11 and the second hydraulic pump 12. The circuit switching unit 40 is assigned to each actuator (that is, each of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the other actuator), and the direction switching valves 41a, 41b, and 41c (8-port 3-position hydraulic pressure). It has a pilot actuating valve) and a traveling switching valve 42.

Although not shown in FIGS. 3 and 4, other actuators are shown in the first tandem passage 24, the second tandem passage 25, the first parallel passage 26, and the second actuator on the downstream side of the first actuator 31. It is provided so as to be communicative with the parallel passage 27, and is composed of one or a plurality of actuators (for example, a hydraulic motor or a hydraulic cylinder). Hereinafter, other actuators (that is, one or a plurality of actuators) are also collectively referred to as a "second actuator". That is, the second actuator is one or a plurality of actuators different from the first traveling motor 21, the second traveling motor 22, and the first actuator 31, and is driven according to the supplied hydraulic oil.

The directional control valve 41a is a directional control valve for the first traveling motor 21, and switches whether or not hydraulic oil is supplied to the first traveling motor 21 and the direction in which the hydraulic oil is supplied. The directional control valve 41b is a directional control valve for the second traveling motor 22, and switches whether or not hydraulic oil is supplied to the second traveling motor 22 and the direction in which the hydraulic oil is supplied. The directional control valve 41c is a directional control valve for the first actuator 31, and switches whether or not hydraulic oil is supplied to the first actuator 31 and the direction in which hydraulic oil is supplied. A dedicated directional control valve is also provided for the second actuator (that is, another actuator). The directional control valve can not only switch the presence / absence of hydraulic oil supply to the assigned actuator and the hydraulic oil supply direction, but also adjust the supply amount of hydraulic oil to the assigned actuator by narrowing the oil passage. You can also.

The hydraulic system 10 includes a first tandem passage 24, a second tandem passage 25, a first parallel passage 26, and a second parallel passage 27. Direction switching valves 41a, 41b, and 41c are provided in series in each of the first tandem passage 24 and the second tandem passage 25. As a result, the hydraulic oil flowing through each of the first tandem passage 24 and the second tandem passage 25 is moved to the upstream side (that is, the side closer to the first hydraulic pump 11 and the second hydraulic pump 12) by the direction switching valves 41a, 41b, 41c. ) Can be preferentially supplied to the actuator.

For example, in the hydraulic system 10 shown in FIGS. 3 and 4, when the direction switching valve 41a is placed in the drive position (that is, the forward drive position on the right side of FIG. 3 or the reverse drive position on the left side of FIG. 3), the first The hydraulic oil is supplied to the first traveling motor 21 from the 1 tandem passage 24. Therefore, the hydraulic oil flowing through the first tandem passage 24 is not supplied to the actuators (that is, the second traveling motor 22, the first actuator 31, and other actuators) provided on the downstream side of the first traveling motor 21. When the direction switching valve 41b is placed in the drive position (that is, the forward drive position on the right side of FIG. 3 or the reverse drive position on the left side of FIG. 3), the hydraulic oil is supplied from the second tandem passage 25 to the second traveling motor 22. Is supplied. Therefore, the hydraulic oil flowing through the second tandem passage 25 is not supplied to the actuator (that is, the first actuator 31 and other actuators) provided on the downstream side of the second traveling motor 22.

Between the direction switching valve 41b and the direction switching valve 41c, a branch path is formed in the middle of each of the first tandem passage 24 and the second tandem passage 25. The branch path is provided with a check valve for preventing backflow of hydraulic oil from the downstream side to the upstream side, and is provided so as to be able to communicate with the first actuator 31 via the direction switching valve 41c. Further, a branch path is formed in each of the first parallel passage 26 and the second parallel passage 27 in the middle, and the branch path is provided with a throttle and a check valve, and the first actuator is provided via the direction switching valve 41c. It is provided so as to be able to communicate with 31. These branch paths provided in each of the first tandem passage 24, the second tandem passage 25, the first parallel passage 26, and the second parallel passage 27 are connected to the directional control valve 41c after merging with each other.

The first tandem passage 24, the second tandem passage 25, the first parallel passage 26, and the second parallel passage 27 are connected to the tank passage 29 at the most downstream portion. The hydraulic oil that has not been supplied to any of the actuators connected to the hydraulic circuit 13 finally flows into the tank passage 29 from these passages and is discharged from the tank passage 29 to the discharge tank 30. Further, the direction switching valves 41a, 41b, and 41c are also connected to the tank passage 29. The hydraulic oil discharged from the actuators connected to the hydraulic circuit 13 (that is, the first traveling motor 21, the second traveling motor 22, the first actuator 31 and the second actuator) is passed through the direction switching valves 41a, 41b and 41c. It flows into the tank passage 29 and is discharged from the tank passage 29 to the discharge tank 30.

The traveling switching valve 42 is configured as a hydraulic pilot operating valve whose state is switched by the pilot pressure (flood control). When the pilot pressure is not acting on the traveling switching valve 42, the traveling switching valve 42 is placed in the first switching state 42a, and when the pilot pressure is acting on the traveling switching valve 42, the traveling switching valve 42 is placed in the first switching state 42a. 2 It is placed in the switching state 42b.

When the traveling switching valve 42 is placed in the first switching state 42a, the traveling switching valve 42 connects the oil passage connected from the first hydraulic pump 11 to the traveling switching valve 42 to the first tandem passage 24 and the second The oil passage connected from the hydraulic pump 12 to the traveling switching valve 42 is connected to the second parallel passage 27. Therefore, when the traveling switching valve 42 is placed in the first switching state 42a, the first hydraulic pump 11 supplies hydraulic oil to the first tandem passage 24 and the first parallel passage 26, and the second hydraulic pump 12 supplies the second tandem passage. Hydraulic oil is supplied to the 25 and the second parallel passage 27. As a result, the hydraulic oil can be supplied from the first hydraulic pump 11 to at least the first traveling motor 21, and the hydraulic oil can be supplied from the second hydraulic pump 12 to at least the second traveling motor 22. ..

On the other hand, when the traveling switching valve 42 is placed in the second switching state 42b, the traveling switching valve 42 connects the oil passage connected from the first hydraulic pump 11 to the traveling switching valve 42 to the second parallel passage 27, and also connects the traveling switching valve 42 to the second parallel passage 27. The oil passage connected from the second hydraulic pump 12 to the traveling switching valve 42 is connected to the first tandem passage 24. The "oil passage to the second parallel passage 27" and the "oil passage to the first tandem passage 24" of the traveling switching valve 42 in the second switching state 42b are connected to each other via a connecting oil passage. There is. A throttle and a check valve are provided in the connecting oil passage to allow hydraulic oil to flow from the "oil passage to the second parallel passage 27" to the "oil passage to the first tandem passage 24". .. Therefore, when the traveling switching valve 42 is placed in the second switching state 42b, the first hydraulic pump 11 mainly supplies hydraulic oil to the first parallel passage 26 and the second parallel passage 27, and the second hydraulic pump 12 is in the first tandem. Hydraulic oil is supplied to the passage 24 and the second tandem passage 25. As a result, while supplying hydraulic oil from the second hydraulic pump 12 to the first traveling motor 21 and the second traveling motor 22, at least the second actuator (that is, downstream of the first actuator 31) is provided from the first hydraulic pump 11. It becomes possible to supply hydraulic oil to other actuators).

The circuit switching unit 40 (that is, the direction switching valves 41a, 41b, 41c and the traveling switching valve 42) of the present embodiment changes the hydraulic circuit 13 of the hydraulic system 10 into the following first circuit state and second circuit state. .. The first circuit state and the second circuit state described below describe "when the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, and other actuators are driven. It is realized in cases other than ".

That is, when the hydraulic circuit 13 is in either the first circuit state (see FIG. 4) or the second circuit state (see FIG. 3), the traveling switching valve 42 is placed in the first switching state 42a. As a result, the oil passage from the first hydraulic pump 11 is connected to each of the first tandem passage 24 and the first parallel passage 26, and the oil passage from the second hydraulic pump 12 is connected to the second tandem passage 25 and the second parallel passage 27. It leads to each of. However, the direction switching valve 41c assigned to the first actuator 31 is placed in the drive position (forward drive position on the right end side in the example shown in FIG. 4) in the first circuit state, and is in the neutral position (in the second circuit state). In the example shown in FIG. 3, it is placed in the center position).

Therefore, in the first circuit state, the first hydraulic pump 11 supplies the hydraulic oil to the first traveling motor 21 and the first actuator 31, and the second hydraulic pump 12 supplies the hydraulic oil to the second traveling motor 22 and the first actuator 31. Supply (see FIG. 4). Further, in the second circuit state, the hydraulic oil is supplied from the first hydraulic pump 11 to the first traveling motor 21, the hydraulic oil is supplied from the second hydraulic pump 12 to the second traveling motor 22, and the first hydraulic pump 11 and the second traveling motor 22 are supplied. 2 No hydraulic oil is supplied from the hydraulic pump 12 to the first actuator 31 (see FIG. 3).

The circuit switching unit 40 has the flow rate of the hydraulic oil supplied to the first traveling motor 21 as the flow rate of the hydraulic oil supplied to the second traveling motor 22 in each of the above-mentioned first circuit state and the second circuit state. The hydraulic circuits can be modified to be equal.

Further, when the actuators other than the first traveling motor 21, the second traveling motor 22 and the first actuator 31 (that is, the second actuator) are not connected to the hydraulic circuit 13, the traveling switching valve 42 may not be provided. In this case, the oil passage extending from the first hydraulic pump 11 and the second hydraulic pump 12 can be configured in the same manner as the oil passage in the case of the first switching state 42a of the traveling switching valve 42. That is, the oil passage from the first hydraulic pump 11 is connected to the first tandem passage 24 and the first parallel passage 26, and the oil passage from the second hydraulic pump 12 is connected to the second tandem passage 25 and the second parallel passage 27. can do.

FIG. 5 is a schematic view showing a circuit configuration of the hydraulic system 10 according to the embodiment of the present invention, in which the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, and the like. Indicates a state in which the actuator of is driven.

When the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, and another actuator (that is, the second actuator) connected to the hydraulic circuit 13 is driven, the traveling switching valve 42 Is placed in the second switching state 42b. As a result, the hydraulic oil from the second hydraulic pump 12 is supplied to the first traveling motor 21 via the first tandem passage 24, and the hydraulic oil from the second hydraulic pump 12 is supplied to the second traveling motor 22 through the first tandem passage 24. It is supplied via the tandem passage 25, and the hydraulic oil from the first hydraulic pump is supplied to the second actuator via the first parallel passage 26 and / or the second parallel passage 27. When the traveling switching valve 42 is placed in the second switching state 42b in this way, the hydraulic circuit 13 is placed in the third circuit state, and hydraulic oil is supplied from the second hydraulic pump 12 to the first traveling motor 21 and the second traveling motor 22. It is supplied, hydraulic oil is not supplied to the first actuator 31, and hydraulic oil is supplied from the first hydraulic pump 11 to the second actuator (that is, another actuator provided on the downstream side of the first actuator 31).

FIG. 6 is a block diagram showing the relationship between the instruction receiving unit 50, the direction switching valve 41a, and various actuators.

The hydraulic system 10 includes an instruction receiving unit 50 that receives an operation instruction from the operator. The instruction receiving unit 50 is provided in association with each actuator (that is, each of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the second actuator 32). The specific form of the instruction receiving unit 50 is not particularly limited, but typically, the instruction receiving unit 50 can be configured by a lever, a button, a pedal, or the like that can be operated by the operator. The instruction receiving unit 50 of the present embodiment is associated with the first traveling pedal 51 associated with the first traveling motor 21, the second traveling pedal 52 associated with the second traveling motor 22, and the first actuator 31. It includes a first operating lever 53 and a second operating lever 54 associated with the second actuator 32. Since the second actuator 32 collectively represents one or a plurality of actuators as described above, the second operating lever 54 also collectively represents one or a plurality of levers and the like.

For example, the operator can control the direction switching valve 41a by operating the first traveling pedal 51 to switch between driving and non-driving of the first traveling motor 21 and to control the driving state of the first traveling motor 21. Similarly, the operator controls the direction switching valve 41b by operating the second traveling pedal 52, controls the direction switching valve 41c by operating the first operating lever 53, and operates the second operating lever 54. By doing so, the direction switching valve 41d can be controlled, and the driving and non-driving switching and the driving state of the second traveling motor 22, the first actuator 31, and the second actuator 32 can be controlled. Therefore, when moving the dozer 33 up and down, the operator may operate the first operation lever 53.

FIG. 7 is a flowchart showing an outline of the determination flow of the first circuit state (see FIG. 4) and the second circuit state (see FIG. 3). For ease of understanding, FIG. 7 shows a flow of determining the circuit state based on the presence / absence of traveling drive and the presence / absence of dozer drive. Therefore, the flowchart shown in FIG. 7 is based on the premise that the second actuator 32 (that is, another actuator provided on the downstream side of the first actuator 31) is not driven. The flow of determining the circuit state in consideration of whether or not the second actuator 32 is driven will be described later with reference to FIGS. 8 and 9.

When the drive mode of the hydraulic system 10 is a mode for traveling drive (Y in S11 in FIG. 7), the subsequent steps (S12 to S14) shown in FIG. 7 are performed. On the other hand, when the drive mode of the hydraulic system 10 is not the mode in which the traveling drive is performed (N in S11), the subsequent step shown in FIG. 7 is not performed.

When the drive mode of the hydraulic system 10 is a mode for driving driving and a mode for driving the dozer by the first actuator 31 (Y in S12), the circuit switching unit 40 puts the hydraulic circuit 13 in the first circuit state. (S13). On the other hand, when the drive mode of the hydraulic system 10 is a mode for driving the running drive but not a mode for driving the dozer by the first actuator 31 (N in S12), the circuit switching unit 40 sets the hydraulic circuit 13 as the second circuit. The state is set (S14).

Specifically, the circuit switching unit 40 changes the hydraulic circuit 13 based on the operation instruction received by the instruction receiving unit 50 (see FIG. 6) to realize the first circuit state and the second circuit state. For example, when the operation instruction received by the instruction receiving unit 50 (see FIG. 6) corresponds to a mode in which the first actuator 31 is driven while driving the first traveling motor 21 and the second traveling motor 22, the circuit switching unit 40 puts the hydraulic circuit 13 in the first circuit state. On the other hand, when the operation instruction received by the instruction receiving unit 50 corresponds to a mode in which the first traveling motor 21 and the second traveling motor 22 are driven but the first actuator 31 is not driven, the circuit switching unit 40 is a hydraulic circuit. Let 13 be the second circuit state.

FIG. 8 is a flowchart showing an outline of a flow for determining a switching state of the traveling switching valve 42.

When the drive mode of the hydraulic system 10 is a mode for traveling drive (Y in S21 in FIG. 8), the subsequent step S22 is performed. On the other hand, when the drive mode of the hydraulic system 10 is not the mode for driving the traveling drive (N in S21), the traveling switching valve 42 is placed in the first switching state 42a (S25).

When the drive mode of the hydraulic system 10 is a mode for driving the running drive and a mode for driving the dozer by the first actuator 31 (Y in S22), the driving mode is driven regardless of whether or not the second actuator 32 is driven. The switching valve 42 is placed in the first switching state 42a (S25). On the other hand, when the drive mode of the hydraulic system 10 is a mode for driving the running drive but not a mode for driving the dozer by the first actuator 31 (N in S22), the following depends on whether or not the second actuator 32 is driven. The switching state of the traveling switching valve 42 is determined as described above. That is, when the drive mode of the hydraulic system 10 is not the mode for driving the second actuator 32 (N in S23), the traveling switching valve 42 is placed in the first switching state 42a (S25). On the other hand, when the drive mode of the hydraulic system 10 is a mode for driving the second actuator 32 (Y in S23), the traveling switching valve 42 is placed in the second switching state 42b (S24).

Specifically, the switching state of the traveling switching valve 42 is determined, the states of the direction switching valves 41a, 41b, and 41c are determined based on the operation instruction received by the instruction receiving unit 50 (see FIG. 6), and the flood control The circuit 13 is modified to realize the first circuit state, the second circuit state, and the third circuit state. For example, the operation instruction received by the instruction receiving unit 50 drives the first traveling motor 21 and the second traveling motor 22, drives the first actuator 31, and drives or does not drive the second actuator 32. When corresponding, the traveling switching valve 42 is placed in the first switching state 42a, and the circuit switching unit 40 puts the hydraulic circuit 13 in the first circuit state. When the operation instruction received by the instruction receiving unit 50 corresponds to the second drive mode in which the first traveling motor 21 and the second traveling motor 22 are driven and the first actuator 31 and the second actuator 32 are not driven, the operation instruction is supported. The traveling switching valve 42 is placed in the first switching state 42a, and the circuit switching unit 40 puts the hydraulic circuit 13 in the second circuit state. Further, the operation instruction received by the instruction receiving unit 50 corresponds to a third drive mode in which the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, and the second actuator 32 is driven. In this case, the traveling switching valve 42 is placed in the second switching state 42b, and the circuit switching unit 40 puts the hydraulic circuit 13 in the third circuit state.

FIG. 9 is a table showing the drive states of various actuators, the state of the traveling switching valve, and the state of the hydraulic circuit in the first drive mode, the second drive mode, and the third drive mode.

As described above, in the first drive mode, the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 (that is, the dozer cylinder) is driven, and the second actuator 32 (that is, another actuator) is driven. The traveling switching valve 42 is placed in the first switching state 42a, and the hydraulic circuit 13 is placed in the first circuit state. Further, in the second drive mode, the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, the second actuator 32 is not driven, and the traveling switching valve 42 is in the first switching state 42a. The hydraulic circuit 13 is placed in the second circuit state. Further, in the third drive mode, the first traveling motor 21 and the second traveling motor 22 are driven, the first actuator 31 is not driven, the second actuator 32 is driven, and the traveling switching valve 42 is brought into the second switching state 42b. It is placed and the hydraulic circuit 13 is placed in the third circuit state.

Next, a logic system for switching the traveling switching valve 42 will be described.

FIG. 10 is a block diagram showing the relationship between the logic system 60 and the traveling switching valve 42. The traveling switching valve 42 is switched to the first switching state 42a or the second switching state 42b by the logic system 60. The logic system 60 controls switching of the traveling switching valve 42 in response to an operation instruction received by the instruction receiving unit 50 (see FIG. 6).

As described above, the logic system 60 included in the hydraulic system 10 switches the traveling switching valve 42 to the first switching state according to the driving states of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the second actuator 32. It is possible to switch between the 42a and the second switching state 42b. However, the specific configuration of the logic system 60 is not particularly limited. Typically, the logic system 60 can be configured by a system using hydraulic logic or a system using electrical signal logic.

FIG. 11 is a diagram showing an example of a hydraulic logic circuit 61 of a logic system 60 using hydraulic logic.

The hydraulic logic circuit 61 of FIG. 11 includes a hydraulic source 64 (that is, a pilot hydraulic source) for the hydraulic logic circuit 61. The oil passage extending from the hydraulic source 64 is connected to the logic valve 66 for the first traveling motor, the logic valve 67 for the second traveling motor, the logic valve 68 for the second actuator, and the logic valve 69 for the dozer via a throttle. The logic valve 66 for the first traveling motor, the logic valve 67 for the second traveling motor, the logic valve 68 for the second actuator, and the logic valve 69 for the dozer are provided in parallel with the oil passage from the hydraulic source 64. Each has a mode of shutting off the oil passage and a mode of communicating the oil passage with the discharge tank 70.

The logic valve 66 for the first traveling motor is linked to the drive mode of the first traveling motor 21, the logic valve 67 for the second traveling motor is linked to the drive mode of the second traveling motor 22, and the logic valve 68 for the second actuator is linked. The dozer logic valve 69 is interlocked with the drive mode of the second actuator 32, and is interlocked with the drive mode of the first actuator 31. The signatures "66a", "67a", "68a" and "69a" in FIG. 11 represent the states when the corresponding actuators are driven in the forward direction, and the signatures "66c", "67c", "68c" and "69c". "Represents the state when the corresponding actuator is driven in the reverse direction, and the codes" 66b "," 67b "," 68b "and" 69b "represent the state when the corresponding actuator is in the neutral position (that is, when not driven). Represent.

Therefore, when any of the first traveling motor 21, the second traveling motor 22, and the second actuator 32 is not driven, or when the logic valve 69 for the dozer is driven, the oil is supplied from the hydraulic source 64 to the oil passage. The pressure oil is discharged to the discharge tank 70, and no pilot pressure is generated in the oil passage at the position indicated by the symbol “A” in FIG. Therefore, the pilot pressure does not act on the traveling switching valve 42, and the traveling switching valve 42 is placed in the first switching state 42a.

On the other hand, when the first traveling motor 21, the second traveling motor 22 and the second actuator 32 are driven and the first actuator 31 is not driven, the oil passage from the hydraulic source 64 is the logic valve 66 for the first traveling motor. It is closed by the logic valve 67 for the second traveling motor, the logic valve 68 for the second actuator, and the logic valve 69 for the dozer. Therefore, a pilot pressure is generated in the oil passage at the position indicated by the symbol "A" in FIG. 11, the pilot pressure acts on the traveling switching valve 42, and the traveling switching valve 42 is placed in the second switching state 42b. Be taken.

As described above, the pressure of the pressure oil in the hydraulic logic circuit 61 changes according to the driving state of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the second actuator 32. The logic system 60 switches the traveling switching valve 42 between the first switching state 42a and the second switching state 42b based on the pressure of the pressure oil (that is, the oil pressure) in the hydraulic logic circuit 61.

FIG. 12 is a diagram showing an example of the electric signal logic circuit 62 of the logic system 60 using the electric signal logic.

The electric signal logic circuit 62 included in the logic system 60 of FIG. 12 is connected to the first traveling pedal 51, the second traveling pedal 52, the first operating lever 53, and the second operating lever 54 of the instruction receiving unit 50. Each of the first traveling pedal 51, the second traveling pedal 52, the first operating lever 53, and the second operating lever 54 sends an electric signal according to the operating state of the operator to the electric signal logic circuit 62. Each of the first traveling pedal 51, the second traveling pedal 52, the first operating lever 53, and the second operating lever 54 is not only an operating portion directly operated by the operator, but also the operating portion. It also includes a signal generation unit that sends an electric signal corresponding to the operation of the above to the electric signal logic circuit 62.

The electric signal logic circuit 62 sets the traveling switching valve 42 as described above in response to the electrical signals sent from the first traveling pedal 51, the second traveling pedal 52, the first operating lever 53, and the second operating lever 54. It switches to either the first switching state 42a or the second switching state 42b.

In this way, the signal flowing through the electric signal logic circuit 62 changes according to the driving states of the first traveling motor 21, the second traveling motor 22, the first actuator 31, and the second actuator 32. The logic system 60 switches the traveling switching valve 42 between the first switching state 42a and the second switching state 42b based on these signals sent through the electric signal logic circuit 62.

FIG. 13 is a circuit diagram showing an example in which the hydraulic system 10 according to the above-described embodiment of the present invention is applied to a hydraulic excavator including a dozer. A hydraulic excavator generally includes a lower frame provided with a crawler, an upper frame rotatably provided with respect to the lower frame, a boom attached to the upper frame, an arm attached to the boom, and a bucket attached to the arm. Be prepared. The hydraulic excavator according to the present embodiment further includes a dozer for extruding sediments such as earth and sand and snow.

The structure of the hydraulic system 10 shown in FIG. 13 is strictly different from that of the hydraulic system 10 shown in FIGS. 3 to 5 described above, but the first hydraulic pump 11 is similar to the hydraulic system 10 shown in FIGS. 3 to 5. , 2nd hydraulic pump 12, 1st tandem passage 24, 2nd tandem passage 25, 1st parallel passage 26, 2nd parallel passage 27, tank passage 29, traveling switching valve 42, direction switching valve 41a, 41b, 41c, 41d , The first traveling motor 21, the second traveling motor 22, and the first actuator 31 are provided. Further, in FIG. 13, a hydraulic motor for turning the upper frame with respect to the lower frame is exemplified as the second actuator 32. Although omitted in FIG. 13, an actuator (for example, a hydraulic cylinder) for driving the boom, arm, and bucket is provided as a second actuator 32 on the downstream side of the swivel hydraulic motor. Further, an actuator for boom swing and an actuator for other services may be provided.

In FIG. 13, the main system hydraulic circuit 13a (see the solid line) for flowing hydraulic oil for driving various actuators and the pressure oil for operating the state operation of the valve and other states are shown. The operation system hydraulic circuit 13b (see dotted line) is shown in the figure.

For example, the symbols “Pa1” and “Pb1” in FIG. 13 connected to the operation system hydraulic circuit 13b are pilot pressures used to change the state (position) of the direction switching valve 41a for the first traveling motor 21. Indicates an inflow / outflow port for the pressure oil applied to the direction switching valve 41a. Similarly, the codes "Pa2" and "Pb2" indicate the inflow / outflow ports of the pilot pressure oil used to change the state of the directional control valve 41b for the second traveling motor 22, and the codes "Pa3" and "Pb3" are used. "Indicates the inflow / outflow port of the pilot pressure oil used to change the state of the directional control valve 41c for the first actuator 31, and the codes" Pa4 "and" Pb4 "are the directional switching valves for the second actuator 32. The inflow / outflow port of the pilot pressure oil used to change the state of 41d is shown.

Further, the code "Pp" in FIG. 13 indicates an inflow port of the pilot pressure oil for supplying the pressure oil (that is, the pilot pressure oil) that brings about the pilot pressure to the operation system hydraulic circuit 13b, and the code "Dr1" is the operation system. The drain port for draining the pilot pressure oil from the hydraulic circuit 13b is shown.

Further, an auto idle system 80, a parking brake system 81 and a logic system 60 (see FIGS. 10 to 12) are connected to the operation system hydraulic circuit 13b. The auto idle system 80 is a system for generating a pilot pressure, and for example, it is possible to bring a pilot pressure in the operation system hydraulic circuit 13b by operating one of the actuators. The parking brake system 81 is a system for controlling on / off of a parking brake (not shown) that brakes a turning operation. For example, when any one of the second actuators 32 including the plurality of actuators or the first actuator 31 is operated, the parking brake system 81 can turn off the parking brake and release the braking of the turning operation. ..

The direction switching valves 41a, 41b, 41c, 41d shown in FIG. 13 are connected not only to the oil passage of the main system hydraulic circuit 13a but also to the oil passage of the operation system hydraulic circuit 13b, and operate to flow through the main system hydraulic circuit 13a. It controls the flow of oil and the pressure oil flowing through the operation system hydraulic circuit 13b, and the supply oil passage for these hydraulic oil and pressure oil. Of the directional control valves 41a, 41b, 41c, and 41d, the portion that controls the hydraulic oil of the main system hydraulic circuit 13a and the portion that controls the pressure oil of the operation system hydraulic circuit 13b are interlocked with each other. Therefore, the state of the operation system hydraulic circuit 13b changes according to the driving state of the first traveling motor 21, the second traveling motor 22, the first actuator 31, the second actuator 32, etc., and is connected to the operation system hydraulic circuit 13b. The control states of various systems such as the auto idle system 80, the parking brake system 81, and the logic system 60 also change.

The directional switching valves 41a, 41b, 41c, 41d can be realized by any valve device, and typically, the directional switching valves 41a, 41b, 41c, 41d can be configured by a spool valve. Further, the traveling switching valve 42 can also be realized by an arbitrary valve device, and typically, the traveling switching valve 42 can be configured by a spool valve. Direction switching valves 41a, 41b, 41c, 41d and traveling switching valves having the functions symbolically shown in FIGS. 3 to 5 and 13 by devising the land portion, notch portion, notch, etc. formed on the spool. 42 can be realized. Therefore, the hydraulic circuit 13 shown in FIG. 13 (that is, the main system hydraulic circuit 13a and the operation system hydraulic circuit 13b) may be made of a monoblock type valve body including, for example, a plurality of spool valves by those skilled in the art having ordinary knowledge. It can be configured.

Also in the hydraulic system 10 shown in FIG. 13 described above, by switching the circuit switching unit 40 (that is, the direction switching valves 41a, 41b, 41c, 41d and the traveling switching valve 42), the hydraulic system 10 shown in FIGS. Similarly, the "circuit state according to the behavior of various actuators" shown in FIG. 9 can be realized.

As described above, according to the hydraulic system 10 of the present embodiment, three or more actuators including two traveling motors and a dozer cylinder (in the above-described embodiment, the first traveling motor 21, the second traveling motor 22, and the first actuator). 31 and the second actuator 32) can be appropriately driven and controlled by only two hydraulic pumps.

Further, when only the first traveling motor 21 and the second traveling motor 22 are driven and only traveling is performed, the traveling switching valve 42 is placed in the first switching state 42a and the hydraulic circuit 13 is put into the first circuit state. It is placed and hydraulic oil is supplied from one hydraulic pump to only one traveling motor. On the other hand, when the first actuator 31 is driven to operate the dozer, the traveling switching valve 42 is placed in the first switching state 42a and the hydraulic circuit 13 is set to the first regardless of whether or not the other actuators are driven. It is placed in a circuit state, and hydraulic oil is supplied from one hydraulic pump to only one traveling motor. In this way, since hydraulic oil is supplied from one hydraulic pump to only one traveling motor regardless of whether the dozer is operated or not during traveling, switching is performed when the dozer is switched between driving and non-driving. No shock occurs and the operability is good.

As described above, according to the hydraulic system 10 of the present embodiment, it is possible to realize comfortable operability while reducing the number of hydraulic pumps to two and reducing the cost.

The present invention is not limited to the above-described embodiments and modifications. For example, various modifications may be added to each element of the above-described embodiment and modification. In addition, a form including a component other than the above-mentioned components is also included in the embodiment of the present invention. In addition, an embodiment of the present invention also includes a form in which some of the above-mentioned components are not included. In addition, an embodiment of the present invention also includes a part of the components included in one embodiment of the present invention and a part of the components included in another embodiment of the present invention. Therefore, the components included in each of the above-described embodiments and modifications and the embodiments of the present invention other than the above may be combined, and the embodiments related to such combinations are also included in the embodiments of the present invention. .. Further, the effect produced by the present invention is not limited to the above-mentioned effect, and a peculiar effect according to the specific configuration of each embodiment can be exhibited. In this way, various additions, changes and partial deletions can be made to each element described in the claims, the specification, the abstract and the drawings without departing from the technical idea and purpose of the present invention. Is.

10 Hydraulic system 11 1st hydraulic pump 12 2nd hydraulic pump 13 Hydraulic circuit 13a Main system hydraulic circuit 13b Operation system hydraulic circuit 21 1st traveling motor 22 2nd traveling motor 24 1st tandem passage 25 2nd tandem passage 26 1st parallel Passage 27 Second parallel passage 29 Tank passage 30 Discharge tank 31 First actuator 32 Second actuator 33 Dozer 40 Circuit switching unit 41a Direction switching valve 41b Direction switching valve 41c Direction switching valve 41d Direction switching valve 42 Travel switching valve 42a First switching State 42b 2nd switching state 50 Instruction receiving part 51 1st traveling pedal 52 2nd traveling pedal 53 1st operating lever 54 2nd operating lever 60 Logic system 61 Hydraulic logic circuit 62 Electric signal logic circuit 64 Hydraulic source 66 1st traveling motor Logic valve 67 Logic valve for the second traveling motor 68 Logic valve for the second actuator 69 Logic valve for the dozer 70 Discharge tank 80 Auto idle system 81 Parking brake system

Claims (7)

The first hydraulic pump and the second hydraulic pump that supply hydraulic oil,
The first traveling motor and the second traveling motor driven according to the supplied hydraulic oil, and
A first actuator that drives the dozer according to the supplied hydraulic oil, and
A circuit switching unit that changes the hydraulic circuit to switch the supply destination of the hydraulic oil from the first hydraulic pump and the second hydraulic pump, and
A second actuator different from the first actuator, which is driven according to the supplied hydraulic oil, is provided.
The circuit switching unit is
A first circuit in which the hydraulic oil is supplied from the first hydraulic pump to the first traveling motor and the first actuator, and the hydraulic oil is supplied from the second hydraulic pump to the second traveling motor and the first actuator. State and
The hydraulic oil is supplied from the first hydraulic pump to the first traveling motor, the hydraulic oil is supplied from the second hydraulic pump to the second traveling motor, and the hydraulic oil is supplied from the first hydraulic pump and the second hydraulic pump. The hydraulic circuit is changed to the second circuit state in which the hydraulic oil is not supplied to the first actuator.
The circuit switching unit includes a traveling switching valve and includes a traveling switching valve.
The traveling switching valve is
A first switching state in which the hydraulic oil is supplied from the first hydraulic pump to at least the first traveling motor and the hydraulic oil is supplied from the second hydraulic pump to at least the second traveling motor.
A second switching state in which the hydraulic oil is supplied from the first hydraulic pump to at least the second actuator while the hydraulic oil is supplied from the second hydraulic pump to the first traveling motor and the second traveling motor. Being
When the hydraulic circuit is put into either the first circuit state or the second circuit state, the traveling switching valve is put into the first switching state.
In the hydraulic circuit, the hydraulic oil is supplied from the second hydraulic pump to the first traveling motor and the second traveling motor, the hydraulic oil is not supplied to the first actuator, and the hydraulic oil is not supplied from the first hydraulic pump. A hydraulic system in which the traveling switching valve is put into the second switching state when the second actuator is put into the third circuit state in which the hydraulic oil is supplied. In each of the first circuit state and the second circuit state, the circuit switching unit has a flow rate of the hydraulic oil supplied to the first traveling motor and a flow rate of the hydraulic oil supplied to the second traveling motor. The hydraulic system according to claim 1, wherein the hydraulic circuit is modified so as to be equal to. It also has an instruction reception unit that accepts operation instructions.
The circuit switching unit is
The operation instruction received by the instruction receiving unit corresponds to the first drive mode in which the first traveling motor and the second traveling motor are driven, the first actuator is driven, and the second actuator is driven or not driven. If so, the hydraulic circuit is set to the first circuit state.
When the operation instruction received by the instruction receiving unit corresponds to the second drive mode in which the first traveling motor and the second traveling motor are driven and the first actuator and the second actuator are not driven, the operation instruction is described. The hydraulic circuit is set to the second circuit state.
When the operation instruction received by the instruction receiving unit corresponds to a third drive mode in which the first traveling motor and the second traveling motor are driven, the first actuator is not driven, and the second actuator is driven. The hydraulic system according to claim 1 or 2 , wherein the hydraulic circuit is changed so as to bring the hydraulic circuit into the third circuit state. To switch the traveling switching valve between the first switching state and the second switching state according to the driving states of the first traveling motor, the second traveling motor, the first actuator, and the second actuator. The hydraulic system according to any one of claims 1 to 3, further comprising the logic system of the above. The logic system has a hydraulic logic circuit and
The pressure of the pressure oil in the hydraulic logic circuit changes according to the driving states of the first traveling motor, the second traveling motor, the first actuator, and the second actuator.
The logic system, on the basis of the pressure oil in the hydraulic logic circuit, the hydraulic system of claim 4 for switching the traveling switching valve between said second switching state and the first switching state. The logic system has an electrical signal logic circuit and
The signal flowing through the electric signal logic circuit changes according to the driving states of the first traveling motor, the second traveling motor, the first actuator, and the second actuator.
The hydraulic system according to claim 4 , wherein the logic system switches the traveling switching valve between the first switching state and the second switching state based on a signal flowing through the electric signal logic circuit. The circuit switching unit is
A direction switching valve for the first traveling motor that switches the presence / absence of supply of the hydraulic oil to the first traveling motor and the supply direction of the hydraulic oil, and
A direction switching valve for the second traveling motor that switches the presence / absence of supply of the hydraulic oil to the second traveling motor and the supply direction of the hydraulic oil, and
The hydraulic system according to any one of claims 1 to 6 , further comprising a direction switching valve for the first actuator that switches the presence / absence of supply of the hydraulic oil to the first actuator and the supply direction of the hydraulic oil.

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