JPH0633616B2 - Hydraulic circuit - Google Patents

Description

The present invention relates to a hydraulic circuit provided in a hydraulic machine such as a hydraulic shovel.

<Prior Art> FIGS. 4 and 5 are explanatory views showing a hydraulic shovel that also serves as a crane, as an example of a hydraulic machine to which the present invention is applied, and FIG. 4 shows a form at the time of normal excavation work. A side view and FIG. 5 are side views showing a form at the time of crane work.

In FIG. 4, 1 is a running body, 2 is a revolving structure arranged on the traveling structure 1, 3 is a boom rotatably mounted on the revolving structure 2, and 4 is a boom cylinder for rotating the boom 3. Reference numeral 5 denotes an arm rotatably mounted on the boom 3, 6 is an arm cylinder for rotating the arm 5, 7 is a bucket rotatably mounted on the arm 5, and 8 is a bucket for rotating the bucket 7. It is a bucket cylinder. The boom 3, the arm 5, the bucket 7 and the like constitute a working machine, that is, a load body. For this hydraulic shovel,
By appropriately expanding and contracting the boom cylinder 4, the arm cylinder 6, and the bucket cylinder 8, the boom 3, the arm 5, and the bucket 7 can be rotated, and desired excavation work or the like can be performed.

Further, by removing the bucket 7 and the bucket cylinder 8 from the state shown in FIG. 4 and attaching the lifting tool 9 to the tip of the arm 5 as shown in FIG. You can do it.

FIG. 6 is a circuit diagram showing a schematic configuration of a conventional hydraulic circuit provided in such a hydraulic shovel that also serves as a crane.

In FIG. 6, reference numeral 4 is the boom cylinder described above as an example of the hydraulic cylinder, 11 is a variable displacement hydraulic pump for supplying pressure oil for driving the boom cylinder 4, and 12
Is a prime mover for driving the variable displacement hydraulic pump 11, 13
Is a relief valve for setting the discharge pressure of the variable displacement hydraulic pump 11. 14 is a boom cylinder 4 and a hydraulic pump 11.
Is a directional control valve which is arranged between the directional control valve and the directional control valve and which controls the drive of the boom cylinder 4, and a check valve 15 which prevents the backflow of the pressure oil supplied to the directional control valve. Reference numerals 16 and 17 denote pipe lines that connect the directional control valve 14 and the boom cylinder 4, and the pipe line 17 communicates with the bottom side chamber 4 a of the boom cylinder 4.
The conduit 16 is connected to the rod side chamber 4b of the boom cylinder 4. Reference numeral 18 denotes a holding valve disposed between the boom cylinder 4 and the direction control valve 14 and in the middle of the pipe line 17. The holding valve 18 flows the pressure oil in the direction from the bottom side chamber 4a of the boom cylinder 4 to the direction control valve 14. And a pilot check valve 19 that can regulate the
9, an overload prevention valve 20 for releasing the high pressure generated in the bottom side chamber 4a of the boom cylinder 4 due to the overload applied to the boom 3 described above. In addition, 21
Is a pilot line which is connected to the line 16 and guides the pilot pressure to the pilot check valve 19, and 22 is a tank.

The operation of the hydraulic circuit configured in this way is as follows.

That is, by switching the directional control valve 14 from the neutral position N in FIG. 6 to the position A, the pressure oil of the hydraulic pump 11 causes the check valve 15, the directional control valve 14, the pipe line 23, and the pilot check check of the holding valve 18. Valve 19, line 1
7 is supplied to the bottom side chamber 4a of the boom cylinder 4 and the pressure oil in the rod side chamber 4b of the boom cylinder 4 is returned to the tank 22 via the pipe line 16 and the direction control valve 14, and thereby the boom The cylinder 4 extends in the direction of arrow 24.

Further, by switching the directional control valve 14 to the position B,
The pressure oil of the hydraulic pump 11 is the check valve 15 and the direction control valve 1.
4, the rod-side chamber 4 of the boom cylinder 4 via the pipe 16.
While being supplied to b, the pressure oil in the conduit 16 is guided to the pilot check valve 19 via the pilot conduit 21.
As a result, the pilot check valve 19 is opened, and the pressure oil in the bottom side chamber 4a of the boom cylinder 4 is transferred to the pipeline 1.
7, open pilot check valve 19, line 2
3. Returned to the tank 22 via the directional control valve 14, whereby the boom cylinder 4 contracts in the direction of arrow 25.

Further, when a high pressure is generated in the bottom chamber 4 a of the boom cylinder 4 due to the overload applied to the boom 3, the high pressure is released to the tank 22 via the conduit 17 and the overload prevention valve 20. , Equipment in the circuit due to this overload,
Damage to the pipeline is prevented.

Then, as described above, when the directional control valve 14 is switched to the position A and the boom cylinder 4 is extended in the direction of the arrow 24, for example, during the crane work, if the pipeline 23 is damaged, the boom cylinder 4 is not loaded. The boom cylinder 4 tries to contract in the direction of the arrow 25 due to the weight of the body and the suspended load.
The pressure oil flowing from the bottom-side chamber 4a of
The flow is blocked by the pilot check valve 19 in the closed state due to the fact that the pressure is not applied to the valve 6, thereby preventing the load and the suspended load from falling.

<Problems to be Solved by the Invention> By the way, the conventional hydraulic circuit described above requires the holding valve 18 in order to also perform the crane work, which increases the manufacturing cost. Further, since pressure oil flows through the holding valve 18, pressure loss increases, which causes a decrease in operating speed of actuators such as the boom cylinder 4, noise, and deterioration of heat balance. Further, since the holding valve 18 is provided, the circuit becomes complicated and the circuit design tends to be complicated.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to provide a hydraulic circuit that can obtain a holding function without requiring a holding valve.

<Means for Solving the Problems> In order to achieve this object, the present invention is directed to a neutral block type directional control valve for controlling the flow direction of pressure oil supplied from a variable displacement hydraulic pump to an actuator. The directional control valve and the actuator are provided as an integral structure, that is, the two are connected without an ordinary rubber hose being interposed.

<Operation> With the present invention configured as described above, the variable displacement hydraulic pump and the directional switching valve can be operated while the actuator is being driven, that is, when the directional switching valve is switched from the neutral position to the operating position. When the pipe line connecting the valve is damaged, the directional switching valve may be returned to the neutral position.Since this directional switching valve is a neutral block type, this directional switching valve allows the directional switching valve to operate from the actuator side. The pressure oil is prevented from flowing out, and the actuator is kept in a stopped state.
That is, the neutral block type directional control valve has a holding function, and therefore can be used for crane work or the like in a hydraulic shovel, and does not require a holding valve. Further, since the direction switching valve and the actuator are provided as an integrated structure, it is possible to suppress the pressure loss until the pressure oil is supplied to the actuator.

<Example> Hereinafter, the hydraulic circuit of the present invention will be described with reference to the drawings. First
1 to 3 are explanatory views showing an embodiment of the present invention, FIG. 1 is a circuit diagram showing a basic configuration of a hydraulic circuit provided in a hydraulic shovel capable of crane work, and FIG. 2 is FIG. Explanatory diagram illustrating the configuration of the control means provided in the hydraulic circuit shown in,
FIG. 3 is an explanatory view illustrating the configuration of the switching valve control device provided in the control means shown in FIG.

In FIG. 1, 11 is a variable displacement hydraulic pump, 13 is a relief valve that sets the discharge pressure of the variable displacement hydraulic pump 11, 22 is a tank, 4 is a boom cylinder, 4a is the bottom chamber of the boom cylinder 4, and 4b is Rod side room, 8
Are bucket cylinders, which are equivalent to those shown in FIG. 6 described above. Further, reference numeral 30 is a main conduit communicating with the variable displacement hydraulic pump 11, 31 is a main conduit communicating with the tank 22, and the ends thereof are closed. 32
Is a valve provided as an integral structure with the boom cylinder 4 without interposing a rubber hose. In this case, the valve 32 may be connected to a metal pipe normally provided as an accessory to the boom cylinder 4,
Alternatively, the metal pipe described above may be removed and the boom cylinder 4 may be directly connected to the main body. The valve 32 is a directional control valve 33 that is a neutral block type spool valve that controls the flow direction of the pressure oil supplied to the boom cylinder 4.
A check valve 34 for preventing backflow and an overload relief valve 35 are provided. This valve 32 has a conduit 36
The main conduit 30 is communicated with via the main conduit 31 and the main conduit 31 is communicated with via the conduit 37. Reference numeral 38 is a valve provided as an integral structure with the bucket cylinder 8 and is configured in the same manner as the valve 32 described above. These valves 32 and 38 are connected in parallel to the main pipelines 30 and 31. Although not shown, actuators such as a traveling motor and an arm cylinder are also provided as a unitary structure with valves equivalent to the valves 32 and 38, whereby these valves are connected in parallel to the main pipelines 30 and 31, for example. ing. Further, 39 is a regulator for controlling the tilt angle of the variable displacement hydraulic pump 11, 40 is operation command means for outputting a command signal for operating a traveling motor (not shown), and 41 is a command signal for operating the boom cylinder 4. The operation command means 42 is an operation command means for outputting a command signal for operating the bucket cylinder 8. Reference numeral 43 is a control means for selecting one of a plurality of metering characteristics that are predetermined according to the command signals output from the operation command means 40, 41, 42 and outputting a control signal corresponding to the selected value.
Reference numeral 44 is a switch for outputting an instruction signal for instructing a corresponding one of a plurality of metering characteristics preset by the control means 43 according to the type of work.

The operation command means 40, 41, 42, the valve 32,
The solenoids such as the directional control valve 33, etc., composing 38, etc., the regulator 39, and the switch 44 are connected to the control means 43, which has the construction illustrated in FIG. That is, the control means 43, as shown in FIG. 2, has a plurality of preset meters related to the traveling motor instructed by the switch 44 according to the command signal _LTR output from the operation command means 40. A metering characteristic table 45 for selecting a corresponding value on one of the ring characteristics and outputting it as a signal x _TR.
a and a command signal L _BO output from the operation command means 41
Boom cylinder 4 instructed by switch 44 according to
According to the metering characteristic table 45b which selects a corresponding value on any one of the metering characteristics according to the above, and outputs it as the signal x _BO , and the command signal LBK output from the operation commanding means 42. A metering characteristic table 45c for selecting a value corresponding to one of the metering characteristics of the bucket cylinder 8 designated by the switch 44 and outputting it as a signal x _BK.
And these metering characteristic tables 45a, 45
signals x _TR , x _BO , and x _BK output from b and 45c
Adding, an adder 47 which outputs as a signal x _1, the maximum value Rimitsuta that in response to the signals x ₁ output from the adder 47, and outputs the signal x ₂ not exceeding a predetermined maximum value Table 48 and this maximum value limiter table 48
So that the tilt angle corresponds to the signal x ₂ output from
A pump tilt command signal Y is sent to the reguulator 39 shown in FIG.
And a pump swash plate operating mechanism 49 for outputting Further, the control means 43 includes operation command means 40, 41, 42.
Command signals L _TR , L _BO , L output from the respective
Traveling by entering the _BK motor, the boom cylinder 4, the signal _A TR corresponding to the bucket preparative cylinder _8, the switching valve control unit 50 which outputs the A _{BO, A BK,} signal _{A TR, A BO,}
Each of the directional switching valve (not shown) related to the traveling motor, the directional switching valve 33 related to the boom cylinder 4, and the directional switching valve (not shown) inside the valve 38 related to the bucket cylinder 8 is controlled so that the operation amount corresponds to A _BK. Switching valve operating mechanism 5 for outputting drive signals B _TR , B _BO , B _BK to the solenoid
1, 52, 53 are provided. The switching valve control device 50 is operated by the operation command means 4 as illustrated in FIG.
1 is a function table 54 showing the correlation between the command signal L _BO for driving the boom cylinder 4 and the coefficient K.
And a function table 55 showing the correlation between the command signal L _TR for driving the traveling motor output from the operation command means 40 and the target operation command signal A _TR ′, and the coefficient K and the function table output from the function table 54. multiplying the target operation command signal a _{TR 'output} from 55, and a multiplier 56 for outputting a signal a _TR to switch valve operating mechanism 51 described above. The function table 54 has a command signal L _BO.
The relationship of the coefficient K is set to be smaller as is increased, and the function table 55 is set to the relationship of the target operation command signal A _TR ′ which is increased as the command signal L _TR is increased.

The operation of the embodiment thus configured is as follows.

For example, the operation of the boom alone, that is, the operation of the boom cylinder 4 when a crane operation or the like is performed will be described.
Now, when the operation command means 41 is operated to output the signal B _BO from the control means 43 to the solenoid of the directional control valve 33 to switch the directional control valve 33 to the A position, the pressure oil of the pump 11 is transferred to the main pipe line 30, the pipe. Path 36, check valve 34, direction switching valve 33
Via the rod side chamber 4b of the boom cylinder 4,
The pressure oil in the bottom side chamber 4a is guided to the tank 22 via the direction switching valve 33, the pipe line 37, and the main pipe line 31, whereby the boom cylinder 4 contracts. Similarly, when the direction switching valve 33 is switched to the B position, the pressure oil is guided to the bottom side chamber 4a, and the pressure oil is returned from the rod side chamber 4b to the tank 22, whereby the boom cylinder 4 extends.

Here, temporarily, during the boom raising operation, that is, the direction switching valve 3
When 3 is switched to the B position and the pipeline 36 is damaged while the boom cylinder 4 is extending, the boom cylinder 4 tries to contract due to its own weight of the front including the boom 3.
At this time, the check valve 34 prevents the pressure oil from flowing out of the bottom side chamber 4a, whereby the boom cylinder 4 or the boom 3 is held in a stopped state without dropping suddenly. Further, at this time, by setting the direction switching valve 33 to the A position, the boom cylinder 4 can be quickly contracted and the boom 3 can be lowered.

Also, during the boom lowering operation, that is, the direction switching valve 33 is set to A
Position and the boom cylinder 4 is contracting, the pipe 3
When the operation command means 41 is returned to the neutral position, the directional control valve 33 becomes the neutral position N, and since the directional control valve 33 is of the neutral block type, the pressure oil in the bottom side chamber 4a can be prevented. Is blocked and the boom cylinder 4, that is, the boom 3 is held in a stopped state.

Although the operation of the boom cylinder 4 has been described above, the same operation is performed for an arm cylinder (not shown).

Further, for example, when the boom commanding operation is performed by operating the operation commanding means 41 as described above, the switch 44 among the plurality of characteristics preset in the metering characteristic table 45b according to the command signal L _BO is used. A corresponding value on the selected one characteristic is selected, and this value is the signal x.
_It is output to the adder 47 as _BO , the adder 47 outputs a signal x ₁ according to the signal x _BO , and further the signal x
A corresponding value on the maximum value limiter table 48 is selected according to ₁ , and this value is output as a signal x ₂ to the pump swash plate operating mechanism 49. From this pump swash plate operating mechanism 49, the tilt command is issued to the regirator 39. A signal Y is output, and the discharge flow rate of the variable displacement hydraulic pump 11 is controlled in accordance with the tilt command signal Y.

When performing a combined operation such as boom / travel, the variable displacement hydraulic pump 11 is operated according to the signal x ₁ obtained by adding the signals x _TR , x _BO, etc. output from the meter rig characteristic tables 45a, 45b, etc. by the adder 47. The discharge flow rate of is controlled. However, in such a case, if the load pressures applied to the boom cylinder 4 and the travel motor are different, the actuator with the larger load may not move. For example, when the boom is raised during traveling, even if the opening degree of the direction switching valve 33 connected to the boom cylinder 4 is operated according to the command signal L _BO , the pump discharge normally required for raising the boom is generated. The boom pressure cannot be raised because the pressure is higher than the pump discharge pressure required for traveling. Therefore, in this embodiment, in such a case,
The third restriction than _{'A TR} obtained by multiplying by the multiplier _56' A _TR output from K and function table 55 that is output from the function table 54 of the switching valve control unit 50 as illustrated in FIG. The directional switching valve (not shown) of the traveling motor is driven according to the signal A _TR that is generated, that is, by squeezing the directional switching valve of the traveling motor, the pressure on the traveling motor side is set to the boom cylinder 4 side. The pressure is higher than the pressure, which allows a combined boom raising and traveling operation.

Although FIG. 3 illustrates the function tables 54 and 55 and the multiplier 56 related to the combined motion of the traveling and the boom, those equivalent to them are the same in accordance with other combined motions such as traveling, turning, and arms. Can be set to.

In the embodiment configured in this way, a holding function can be obtained without the need for a holding valve,
The safety of crane work in the hydraulic shovel can be ensured, and the metering characteristic of the actuator can be obtained by controlling the pump, so that the actuator can be controlled without being affected by the fluctuation of the load pressure.

In the above embodiment, the direction switching valve 33 and the like are constructed by spool valves, but they may be constructed by combining flow control logic valves.

<Effects of the Invention> With the hydraulic circuit of the present invention configured as described above, a holding function can be obtained without the need for a holding valve, and accordingly, it is possible to cope with crane work of a hydraulic shovel, and the like. Compared with the conventional model, the number of components is smaller and the manufacturing cost can be reduced.The directional control valve and the actuator are provided as an integral structure, which requires the flow of pressure oil in the conventional holding valve. Since the pressure loss can be reduced, the circuit efficiency can be improved, the noise can be suppressed, and the heat balance can be improved as compared with the related art. In addition, the holding valve can be removed, and the piping can be simplified due to the neutral block type directional valve provided in the actuator, so that the circuit can be simplified compared to conventional circuits and the circuit design becomes easier. . Further, since the whole can be constructed by only the parallel circuit, in the case of such a construction, it is possible to add a desired actuator very easily.

[Brief description of drawings]

1 to 3 are explanatory views showing an embodiment of a hydraulic circuit of the present invention, and FIG. 1 is a circuit diagram showing a basic configuration of a hydraulic circuit provided in a hydraulic shovel capable of crane work, and FIG. FIG. 4 is an explanatory view illustrating the configuration of the control means included in the hydraulic circuit shown in FIG. 1, FIG. 3 is an explanatory view illustrating the configuration of the switching valve control device included in the control means shown in FIG. 2, and FIG. FIGS. 5 and 5 are explanatory views showing a hydraulic shovel that also serves as a crane, which is an example of a hydraulic machine to which the present invention is applied. FIG. 4 is a side view showing a form during normal excavation work, and FIG. Side view showing the form during crane work, No. 6
FIG. 1 is a circuit diagram showing a schematic configuration of a conventional hydraulic circuit. 4 ... Boom cylinder, 6 ... Arm cylinder, 8 ...
Bucket cylinder, 11 ... Variable displacement hydraulic pump, 32
...... Valve, 33 ...... Direction switching valve, 38 ...... Valve, 4
0, 41, 42 ... Operation command means, 43 ... Control means,
45a, 45b, 45c ... Metering characteristic table, 50 ... Switching valve control device.

Front page continuation (72) Inventor Tomohiko Yasuda 650 Kazunachicho, Tsuchiura City, Ibaraki Prefecture Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. (56) Reference JP-A-50-86802 (JP, A) JP-A-59-126829 (JP, A)

Claims (1)

[Claims] 1. A variable displacement hydraulic pump, a plurality of actuators driven by the variable displacement hydraulic pump, and a direction switching valve for controlling a flow direction of pressure oil supplied from the variable displacement hydraulic pump to the actuator. In the hydraulic circuit including the above, the directional control valve is a neutral block type, and the directional control valve and the actuator are provided as an integral structure.