JPH09165796A - Hydraulic circuit for working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which is capable of ensuring a necessary speed for a special attachment, according to the type of attachment, without requiring controls on the revolution speed of an engine. SOLUTION: A hydraulic circuit for a working machine is equipped with a first oil-hydraulic pump 2 and a second oil-hydraulic pump 3 driven by an engine 1, permanent actuators like a boom cylinder 11, an arm cylinder 7, etc., an auxiliary actuator 8 to be arranged selectively as occasion demands for driving a special attachment like a mowing machine, etc., an auxiliary directional control valve 8a arranged on a center bypass line for the first oil- hydraulic pump 2 for controlling the flow of pressure oil to be supplied to the auxiliary actuator 8, and a converging line 21 connected to a center bypass line connecting to the second oil-hydraulic pump 3 and available for joining pressure oil from the second oil-hydraulic pump 3 with pressure oil from the first oil-hydraulic pump 2 and supplying the joined pressure oil to the auxiliary directional control valve 8a. A selector valve 20 for changing the converging line 21 from the state of opening to the state of shutoff and vice versa is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a boom cylinder,
In addition to a permanent actuator such as an arm cylinder, the present invention relates to a hydraulic circuit of a work machine such as a mini excavator that has a spare actuator that is selectively arranged when necessary and drives a special attachment.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing an example of a hydraulic circuit of a conventional working machine of this type, and FIG. 3 is a side view showing a working machine, that is, a mini excavator provided with the hydraulic circuit shown in FIG. The conventional hydraulic circuit shown in FIG. 2 includes an engine 1 and
Throttle lever 1 for controlling the rotation speed of this engine 1
a, a first hydraulic pump 2 and a second hydraulic pump 3 driven by the engine 1, and a plurality of actuators driven by pressure oil discharged from the hydraulic pumps 2 and 3, for example, a cylinder for a dump plate 4, swing motor 5,
Left traveling motor 6, arm cylinder 7, spare actuator 8, bucket cylinder 9, swing cylinder 10,
The boom cylinder 11 and the right running motor 12 are provided.

The above-mentioned earth-discharging plate cylinder 4 controls the ascending / descending operation of the earth-discharging plate 32 shown in FIG. 3, the left traveling motor 6 and the right traveling motor 12 control the traveling of a pair of crawler tracks, that is, the traveling body 30, The swing motor 5 controls the swing of the main body having the driver's seat arranged on the traveling body 30, that is, the swing body 31, the boom cylinder 11 controls the vertical swing movement of the boom 33, and the arm cylinder 7 is the arm. The bucket cylinder 9 controls the vertical rotation operation of the bucket 35. Further, the boom cylinder 11, the arm cylinder 7, and the bucket cylinder 9 described above constitute a front actuator, and the swing cylinder 10 includes the boom 33 and the arm 3.
4. Control the swinging movement of the front of the bucket 35 in the horizontal direction.

Of the above-mentioned actuators, the earth plate cylinder 4, the turning motor 5, the left traveling motor 6, the arm cylinder 7, the bucket cylinder 9, and the swing cylinder 1
0, the boom cylinder 11, and the right traveling motor 12 are permanent actuators. Spare actuator 8
Is an actuator that is different from the permanently installed actuator and is selectively placed when necessary.
A special attachment is, for example, a motor provided in a mower.

Further, as shown in FIG. 2, on the bypass line communicating with the first hydraulic pump 2, the direction switch valve 4 for the earth discharging plate for controlling the driving of the cylinder 4 for the earth discharging plate described above.
a, a turning direction switching valve 5 for controlling the drive of the turning motor 5
a, a left traveling direction switching valve 6a for controlling the drive of the left traveling motor 6, an arm direction switching valve 7a for controlling the drive of the arm cylinder 7, and a spare direction switching valve 8a for controlling the drive of the spare actuator 8. Are connected. Of these directional control valves, the unloading plate directional control valve 4a, the turning directional control valve 5a, the left traveling directional control valve 6a, and the arm directional control valve 7a are the first via the conduit 22. The auxiliary directional switching valve 8a is connected in parallel to the hydraulic pump 2, and is connected in tandem downstream of the arm directional switching valve 7a.

In the center bypass line of the second hydraulic pump 3, a right traveling direction switching valve 12a for controlling the driving of the right traveling motor 12, a boom direction switching valve 11a for controlling the driving of the boom cylinder 11, and a swing cylinder. 10 is connected to a swing directional control valve 10a for controlling the drive of 10 and a bucket directional control valve 9a for controlling the drive of the bucket cylinder 9, and the drive of the above-mentioned auxiliary actuator 8 is controlled via a merging conduit 21. The spare directional control valve 8a is connected. That is, the first hydraulic pump 2 is connected to the spare actuator 8 via the confluent conduit 21.
And the pressure oil of the second hydraulic pump 3 can be joined and supplied.

Further, there is provided a connecting pipe 16 for connecting the input port of the left traveling directional switching valve 6a and the input port of the right traveling directional switching valve 12a, and in the middle of this connecting pipe 16,
A communication / shut-off switching valve 17 that holds the communication pipe 16 in either a communication state or a shut-off state is provided. The drive portion of the communication / cutoff switching valve 17 is provided with the traveling direction switching valves 6a, 1a.
A signal conduit 19 for detecting a switching operation from the neutral position of each directional switching valve except 2a and guiding a signal pressure for switching the communication / cutoff switching valve 17 to a state in which the communication conduit 16 is communicated is connected. The signal pressure in the signal line 19 is provided by the pilot hydraulic pressure source 18.

Of the operations performed in the conventional hydraulic circuit, for example, in the case of combined arm / bucket operation, the corresponding arm directional control valve 7a and bucket directional control valve 9a are switched to change the second operation. Hydraulic pump 3
3 is supplied to the bucket cylinder 9 via the bucket direction switching valve 9a, and the pressure oil of the first hydraulic pump 2 is supplied to the arm cylinder 7 via the arm direction switching valve 7a, as shown in FIG. The arm 34 and the bucket 35 rotate to perform a desired combined arm / bucket operation, and excavation work of earth and sand can be performed.

When the operation of the spare actuator 8 is required, that is, at the time of mowing work, the bucket 35 shown in FIG. 3 is removed and a mowing machine is attached to the tip of the arm 34 instead. With the mower attached in this manner, the spare directional control valve 8 shown in FIG.
When only a is switched, the pressure oil of the first hydraulic pump 2 is supplied to the preliminary directional switching valve 8a and the merging conduit 21
The pressure oil of the second hydraulic pump 3 is supplied to the preliminary directional control valve 8a via the
The preliminary actuator 8 is driven by the confluence of the pressure oils of No. 3 and the mower is actuated so that the desired mower can be carried out. The flow rate required to drive the mower is usually 1
This is about the discharge flow rate of the pump. Therefore, in such mowing work, the throttle lever 1a is operated to reduce the rotation speed of the engine 1 below the rated rotation speed, and the discharge is performed from each of the hydraulic pumps 2 and 3. Control is performed to reduce the flow rate.

In some cases, a composite operation of the spare actuator 8 and another actuator, for example, a front actuator such as the arm cylinder 7 is carried out during the mowing work. In such a case, the arm directional control valve 7a is used. The pressure oil of the first hydraulic pump is supplied to the arm cylinder 7 by the switching operation of, and the pressure oil of the second hydraulic pump 3 is supplied to the spare actuator 8 via the merging conduit 21 and the spare direction switching valve 8a. To be done.

Unlike the above, when the special attachment is, for example, a crusher and a cylinder of the crusher is provided as the spare actuator 8 instead of the motor of the mowing machine, the cylinder of the crusher is driven. The required flow rate is larger than that in the case of driving the motor of the mower, and the discharge amount of 2 pumps is required. Therefore, the throttle lever 1a is operated to increase the rotational speed of the engine 1 to the rated rotational speed, and the hydraulic pump 2 , 3 are controlled to discharge the maximum flow rate.

[0012]

As described above, the work speed of the crusher is required to be higher than that of the work of the mower. That is, the operating speed of the spare actuator 8 may differ depending on the type of special attachment.

In the prior art, when the working speed of the special attachment is relatively slow as described above, the throttle lever 1a is operated to operate the engine 1
Of the hydraulic pump 2,
Control is performed to reduce the flow rate discharged from each of the three. Therefore, in particular, by reducing the discharge flow rate of the hydraulic pumps 2 and 3 in this way, the spare actuator 8
When other actuators are operated in combination with the spare actuator 8 while the control is performed to match the required flow rate of the other actuator, the operating speed of the other actuator also slows down. There is a problem that the efficiency of the work performed through the combined operation of the No. 8 and other actuators decreases.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to prepare a spare according to the type of special attachment without requiring engine speed control for reducing the discharge flow rate of the hydraulic pump. An object of the present invention is to provide a hydraulic circuit for a work machine capable of ensuring an operating speed of a vehicle actuator.

[0015]

To achieve the above object, the present invention provides an engine, a throttle lever for controlling the rotational speed of the engine, and at least first and second hydraulic pumps driven by the engine. And a plurality of permanent actuators driven by the pressure oil discharged from the first and second hydraulic pumps, and an actuator different from these permanent actuators, which is selectively arranged when necessary and has a special attachment. A spare actuator for driving the auxiliary hydraulic actuator, a spare bypass directional control valve arranged on a center bypass line connected to the first hydraulic pump for controlling the flow of pressure oil supplied to the spare actuator, and the second It is connected to a center bypass line connected to the hydraulic pump, and the pressure oil of the second hydraulic pump is transferred to the first hydraulic pump. In joins the pressure oil hydraulic circuit for a working machine equipped with a confluent pipe that can be supplied to the preliminary directional control valve, in the confluence pipe, communicating state the confluent pipe,
The configuration is provided with a switching valve that switches to any of the shut-off states.

According to the present invention, when the special attachment driven by the spare actuator requires a relatively high working speed, the switching valve can be operated so as to connect the merging pipes. Good. This allows
The pressure oil of the second hydraulic pump is supplied to the spare actuator together with the pressure oil of the first hydraulic pump via the confluent conduit, and the spare actuator is configured to supply the pressure oil of the first and second hydraulic pumps.
It can be driven by the combined flow rate of the hydraulic pump, and a high operating speed matching the relatively high working speed required by the special attachment can be secured.

If the special attachment driven by the spare actuator has a relatively low operating speed, the switching valve may be operated to switch off the merging conduit. As a result, only the pressure oil of the first hydraulic pump is supplied to the spare actuator, and it is possible to secure a slow operating speed that matches the relatively slow working speed required by the special attachment.

Further, when the special actuator driven by the spare actuator requires a relatively slow work speed and the composite drive of the spare actuator and another actuator is performed, the corresponding other actuator is used. When the directional control valve according to (1) is located on the center bypass line of the first hydraulic pump in which the preliminary actuator is arranged, and upstream of the preliminary directional control valve, the switching valve is connected to the merging pipe line. It may be switched so that they are communicated. As a result, the pressure oil of the first hydraulic pump is supplied to the other actuator, and the pressure oil of the second hydraulic pump is supplied to the spare actuator via the merging conduit.

Further, when the directional control valve relating to the other applicable actuator is located on the center bypass line of the second hydraulic pump, the directional control valve is switched so as to shut off the merging pipe line. Good. Thereby, the first
The pressure oil of the hydraulic pump is supplied to the spare actuator, and the pressure oil of the second hydraulic pump is supplied to the other actuator. With these, it is possible to carry out a combined drive of a desired spare actuator and another actuator.

As described above, the working speed according to the type of the special actuator can be obtained by the switching operation of the switching valve, and the discharge flow rate of the hydraulic pump can be controlled even if the special attachment has a relatively slow working speed. It is not necessary to control the engine speed in order to reduce it, and therefore, when the auxiliary directional control valve related to the special attachment that requires a relatively low working speed and the other actuator are combined, it is sufficient for the other actuator. A flow rate can be provided, which allows the desired combined drive to be implemented.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hydraulic circuit for a working machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a hydraulic circuit of a working machine of the present invention.

FIG. 1 is drawn corresponding to the hydraulic circuit shown in FIG. That is, the first shown in FIG.
This embodiment is also provided in, for example, a mini excavator, and includes an engine 1, a throttle lever 1a for controlling the rotation speed of the engine 1, a hydraulic pump driven by the engine 1, for example, a first hydraulic pump 2, and A second hydraulic pump 3 and a plurality of actuators driven by the pressure oil discharged from these hydraulic pumps 2, 3, such as an earth plate cylinder 4, a swing motor 5, a left traveling motor 6,
Arm cylinder 7, spare actuator 8, bucket cylinder 9, swing cylinder 10, boom cylinder 1
1, a right traveling motor 12 is provided.

Among the above-mentioned actuators, the earth plate cylinder 4, the turning motor 5, the left traveling motor 6, the arm cylinder 7, the bucket cylinder 9, and the swing cylinder 1
0, the boom cylinder 11, and the right traveling motor 12 are permanent actuators as described above. The spare actuator 8 is an actuator different from the permanently installed actuator and is selectively arranged when the special attachment needs to be driven, and is, for example, a motor provided in a mower.

Further, in the center bypass line of the first hydraulic pump 2, an earth-discharging-plate directional switching valve 4a for controlling the drive of the above-mentioned earth-discharging-plate cylinder 4 and a turning for controlling the driving of the turning motor 5 are provided. Direction switching valve 5a, left traveling direction switching valve 6a for controlling driving of left traveling motor 6, arm cylinder 7
Directional control valve 7a for controlling the drive of the actuator, and a directional control valve 8 for the backup controlling the drive of the actuator 8 for the backup.
a is connected.

In the center bypass line of the second hydraulic pump 3, a right traveling direction switching valve 12a for controlling the driving of the right traveling motor 12, a boom direction switching valve 11a for controlling the driving of the boom cylinder 11, and a swing cylinder. 10 is connected to a swing directional control valve 10a for controlling the drive of 10 and a bucket directional control valve 9a for controlling the drive of the bucket cylinder 9, and the drive of the above-mentioned auxiliary actuator 8 is controlled via a merging conduit 21. The spare directional control valve 8a is connected. That is, the first hydraulic pump 2 is connected to the spare actuator 8 via the confluent conduit 21.
And the pressure oil of the second hydraulic pump 3 can be joined and supplied.

Further, a connecting pipe 16 for connecting the input port of the left traveling directional control valve 6a and the input port of the right traveling directional control valve 12a is provided, and in the middle of this connecting pipe 16,
A communication / shut-off switching valve 17 that holds the communication pipe 16 in either a communication state or a shut-off state is provided. The drive portion of the communication / shutoff switching valve 17 detects a switching operation from a neutral position such as the directional switching valves 11a and 7a of the boom cylinder 11 and the arm cylinder 7 and the standby directional switching valve 8, and connects the communication conduit 16 A signal line 19 that guides the signal pressure for switching the communication / cutoff switching valve 17 to the communication / cutoff switching valve 17 to the communication / cutoff switching valve 17 is connected. The signal pressure in the signal line 19 is provided by the pilot hydraulic pressure source 18. The above configuration is equivalent to that shown in FIG.

In particular, in this embodiment, the pressure oil of the second hydraulic pump 3 is merged with the pressure oil of the first hydraulic pump 2 and is supplied to the merging conduit 21 which can be supplied to the spare directional control valve 8a. The switching valve 20 is provided for switching the merging pipe line 21 between a communication state and a cutoff state. Now equipped with a mower that has a relatively slow working speed as a special attachment,
Since the required flow rate of the spare actuator 8 for driving the mower is a relatively small flow rate such as one pump flow rate, when the mower is independently driven, the switching valve 20 shown in FIG. 1 is switched to the lower position. Be done. As a result, the merging conduit 21 is shut off, and the center bypass line of the second hydraulic pump 3 communicates with the tank. Therefore, as the engine 1 is driven at the rated speed, only the pressure oil of the first hydraulic pump 2 is supplied to the spare actuator 8 via the spare directional switching valve 8a, and the required flow rate of the spare actuator 8 is reduced. It matches the supplied flow rate, which allows the mower to be driven and the desired mowing operation to be performed.

Further, in the mowing operation thus performed, for example, in order to perform combined driving of the spare actuator 8 and the arm cylinder 7, the switching valve 20 may be switched to the upper position as shown in FIG. . As a result, the merging conduit 21 is brought into communication with the second hydraulic pump 3
It becomes possible to supply the pressure oil of the above to the spare directional control valve 8a.
Here, while switching the spare directional control valve 8a,
When the arm directional control valve 7a located upstream of the center bypass of the same first hydraulic pump 2 is switched, the pressure oil of the first hydraulic pump 2 is supplied to the arm cylinder 7 via the arm directional control valve 7a. The pressure oil of the second hydraulic pump 3 is transferred to the switching valve 20, the merging pipe line 21, and the spare directional switching valve 8
It is supplied to the spare actuator 8 via a. As a result, a desired mower / arm combined operation can be performed.

Further, for example, in the case of mowing work, in order to perform the combined drive of the spare actuator 8 and the boom cylinder 11, the switching valve 20 may be switched to the lower position of FIG. As a result, the merging conduit 21 is shut off, and the supply of the second hydraulic pump 3 to the preliminary directional control valve 8a is blocked. Here, when the spare directional switching valve 8a is switched and the boom directional switching valve 11a located on the center bypass of the second hydraulic pump 2 is switched, the pressure oil of the first hydraulic pump 2 is switched to the preliminary directional switching valve. The second hydraulic pump 3 is supplied to the spare actuator 8 via the valve 8a.
Pressure oil is supplied to the boom cylinder 11 via the boom direction switching valve 11a. This will give you the desired mower
Boom combined operation can be performed.

When a crusher is provided as a special attachment instead of the mower, the spare actuator 8 serves as a cylinder of the crusher. In such a case, it is necessary to drive the cylinder of this crusher. The flow rate is
The discharge amount of two pumps is required more than when the motor of the mower is driven. Therefore, in such a case, the switching valve 20 is switched to the upper position shown in FIG. 1, and the merging pipe line 21 is brought into a communicating state. As a result, the pressure oils of the first and second hydraulic pumps 2 and 3 are merged and supplied to the spare actuator 8 via the spare direction switching valve 8a, and the crusher can be driven at a high working speed.

As described above, in the present embodiment, the working speed corresponding to the type of the special actuator can be obtained by the switching operation of the switching valve 20, and even if the special attachment has a relatively slow working speed, It is not necessary to control the engine speed in order to reduce the discharge flow rate of the hydraulic pump, and therefore the auxiliary directional control valve 8a for the special attachment which requires a relatively low working speed.
When performing combined drive with the other actuator, a sufficient flow rate can be supplied to the other actuator, so that the desired combined drive can be performed, and the combined operation of the spare actuator 8 and the other actuator is performed. It is possible to improve the efficiency of the work performed as a result.

[0032]

According to the present invention, the operating speed of the spare actuator according to the type of the special attachment can be ensured without the need for controlling the engine speed to reduce the discharge flow rate of the hydraulic pump. When combining a spare actuator that drives a special attachment and another actuator, it is possible to supply a sufficient flow rate to another actuator, and this is performed through a combined operation of this spare actuator and another actuator. The work efficiency can be improved as compared with the conventional one.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic circuit of a working machine of the present invention.

FIG. 2 is a circuit diagram showing an example of a hydraulic circuit of a conventional working machine of this type.

FIG. 3 is a side view showing a work machine, that is, a mini excavator provided with the hydraulic circuit shown in FIG.

[Explanation of symbols]

 1 Engine 2 1st hydraulic pump 3 2nd hydraulic pump 7 Arm cylinder (permanent actuator) 7a Arm directional valve 8 Spare actuator 8a Spare directional valve 11 Boom cylinder (permanent actuator) 11a Boom direction Switching valve 20 Switching valve 21 Confluence line

Claims (1)

[Claims] 1. An engine, a throttle lever for controlling the number of revolutions of the engine, at least first and second hydraulic pumps driven by the engine, and discharges from these first and second hydraulic pumps. A plurality of permanent actuators driven by pressure oil, an actuator different from these permanent actuators, which is selectively arranged when necessary, and a spare actuator for driving a special attachment, and the first hydraulic pump. A secondary directional control valve, which is disposed on the center bypass line and controls the flow of the pressure oil supplied to the preliminary actuator, and a center bypass line connected to the second hydraulic pump, are connected to the second hydraulic pressure. The pressure oil of the pump can be merged with the pressure oil of the first hydraulic pump and supplied to the spare directional control valve. A hydraulic circuit for a working machine provided with a flow conduit, in the confluence pipe, the hydraulic circuit of the working machine, characterized in that it comprises a switching valve for switching the confluence conduit communicating state, to any of the cut-off state.