JP3379371B2 - Hydraulic circuit of work machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic work machine such as a hydraulic wheel crane, and more particularly to a hydraulic circuit adapted to change a relief valve set pressure as required.

[0002]

2. Description of the Related Art The prior art will be described by taking a hydraulic circuit of a hydraulic wheel crane (rough terrain crane) which is a preferred example of the present invention as an example.

In rough terrain cranes, a plurality of hydraulic actuator circuits such as an outrigger circuit for extending and retracting an outrigger cylinder (extension cylinder, jack cylinder), a boom undulation circuit for undulating a boom, and a hoisting circuit for driving a winch are provided. And are usually driven by a common pump.

Here, the maximum pressure of each actuator circuit is determined by the pressure resistance of the actuator, etc., and is set by the relief valve.

In this case, the maximum pressure of the outrigger circuit is
It is set lower than the maximum pressure of other actuator circuits for performing crane work such as boom undulation circuits.

In view of the mechanical structure in which the outrigger is provided on the lower traveling body and the work actuator is provided on the upper revolving body, the outrigger circuit having the lowest maximum pressure set value is provided on the most upstream side (pump side).

[0007] Further, it is necessary to avoid simultaneous operation of the outrigger circuit used for preparatory work before crane work and the work actuator circuit for other crane work in terms of safety.

For this reason, the hydraulic system is divided into an outrigger circuit and a work actuator circuit, and a circuit configuration is adopted in which pressure oil is supplied to the work actuator circuit only when the outrigger is not operating.

However, if the work actuator circuit is used as it is, the maximum pressure thereof is restricted by the set pressure of the outrigger circuit on the upstream side. Therefore, the relief set pressure of the outrigger circuit is limited to the relief set pressure of the work actuator circuit. Need to raise.

Therefore, conventionally, a circuit configuration as shown in FIG. 4 has been adopted.

In the figure, reference numeral 1 is a hydraulic pump as an actuator drive source.
The outrigger circuit A and a work actuator circuit B composed of a plurality of actuator circuits for crane work use pressure oil for the work actuator circuit B only with the outrigger circuit A as the upstream side and in the neutral state of the control valve 3 of the circuit A. Are connected in the state of being supplied.

It should be noted that, for simplification of the description, only one cylinder 4 and 5 and one control valve 3 and 6 are shown as the components of the outrigger circuit A and the work actuator circuit B in the figure.

A relief valve 8 for an outrigger circuit (hereinafter referred to as an outrigger relief valve) 8 is provided in a relief pipe 7 connecting the pump discharge pipe 2 and the tank T, and the maximum pressure P of the outrigger circuit A is provided by the outrigger relief valve 8.
1 (for example, 175 Kg / cm ² ) is set.

On the other hand, a work relief valve 11 is provided in a relief pipe 10 connecting the most upstream point and the most downstream point of the bypass line 9 in the work actuator circuit B, and the maximum pressure P2 of the work actuator circuit B is provided by the relief valve 11. (For example, 250 Kg / cm ² ) is set.

Vent line 1 of outrigger relief valve 8
2, an electromagnetic switching type pressure increasing valve 13 that is operated by switching between the opening position a and the block position b and a pilot relief valve 14 are provided in series, and the pressure increasing valve 13 is in the opening position a. Vent line 1 of outrigger relief valve 8
Since 2 communicates with the tank T, the relief valve 8 is in a normal operating state, and the maximum pressure of the outrigger circuit A becomes the value P1 set by the pilot relief valve 14.

The booster valve 13 is interlocked with the outrigger control valve 3 and is switched to the block position B only when the valve 3 is not operated. In this state, the vent line 12 of the outrigger relief valve 8 is blocked, so that the outrigger is blocked. The relief valve 8 is shut off.

Therefore, in this state, the outrigger relief valve 8 does not act, and the work actuator circuit B operates at the set pressure P2 by the work relief valve 11.

[0018]

However, according to the above-mentioned prior art, since a completely different and expensive electromagnetic switching type booster valve 13 is required outside the outrigger relief valve 8, (i) circuit configuration. Is complicated, (ii) costs are high, (iii) hydraulic piping is increased, and (iv) electric wiring for interlocking with the control valve 3 is required, and contact failure of the connector, corrosion of wiring, disconnection, etc. There were some drawbacks such as the anxiety factor.

Therefore, the present invention provides a hydraulic circuit of a working machine capable of switching the set pressure of the upstream side actuator circuit without using such an electromagnetic switching type external valve, which is a booster valve. Is.

[0020]

According to a first aspect of the present invention, a hydraulic actuator circuit of two systems having different maximum pressure set values driven by a common hydraulic pump has a lower maximum pressure set value on the upstream side. Moreover, the relief valve that sets the maximum pressure of the upstream hydraulic actuator circuit is connected so that pressure oil is not supplied to the downstream actuator circuit when the upstream actuator is operating, and the setting pressure changes according to the pilot pressure. The pressure variable relief valve is configured to guide the pressure of the downstream hydraulic actuator circuit to the upstream relief valve via a pilot line when the upstream hydraulic actuator is not operated, and the set pressure of the relief valve is set to the downstream hydraulic actuator circuit. It is configured to have a value equal to or higher than the pressure of.

According to a second aspect of the present invention, in the structure of the first aspect, the set pressure of the upstream relief valve is set to a value equal to or higher than the maximum pressure set value of the downstream hydraulic actuator circuit when the pilot pressure is introduced. Is.

According to the third aspect of the present invention, two systems of hydraulic actuator circuits having different maximum pressure set values driven by a common hydraulic pump are arranged such that the one having a lower maximum pressure set by each respective relief valve is on the upstream side. ,And,
When operating the upstream actuator, connect it to the downstream actuator circuit without supplying pressure oil, and use a pilot spool that closes the vent line when the external pilot pressure is introduced to the relief valve that sets the maximum pressure of the upstream hydraulic actuator circuit. When the upstream hydraulic actuator is not operated, the upstream relief valve is shut off by guiding the pressure of the downstream hydraulic actuator circuit to the pilot port of the pilot spool through the pilot line.

According to a fourth aspect of the present invention, in any one of the first to third aspects, an outrigger circuit for activating an outrigger of the hydraulic wheel crane is used as an upstream hydraulic actuator circuit, and a boom undulation is used as a downstream hydraulic actuator circuit. This is an application of a work actuator circuit for performing crane work such as hoisting.

According to the structure of claim 1, 2 or 4, the relief valve of the upstream side actuator circuit (outrigger circuit in claim 4) having a low maximum pressure set value is set to a set pressure whose set pressure changes according to the pilot pressure. Since it is configured as a variable relief valve, and the set pressure is increased by introducing the circuit pressure of the downstream side actuator circuit (same working actuator circuit) as the pilot pressure into this relief valve, the electromagnetic pressure used in the conventional circuit is reduced. A switching type external boost valve is not required.

On the other hand, according to the structure of claim 3 or 4,
The structure of the relief valve itself is slightly complicated because the pilot spool of the upstream relief valve is operated by pilot pressure (downstream actuator circuit pressure) to block the vent line of the relief valve and shut off the relief valve. However, compared to the case of using an external booster valve, the circuit configuration becomes simpler, which is advantageous in terms of cost and reliability.

[0026]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

First Embodiment (see FIG. 1) In the following embodiments, a hydraulic circuit of a rough terrain crane is taken as an example in accordance with the conventional description. Further, in the same embodiment, the same parts as those of the conventional circuit shown in FIG.

The outrigger relief valve 15 for setting the maximum pressure of the outrigger circuit A is constructed as a set pressure variable relief valve in which the relief pressure is set by the force of the spring 16 and the pilot pressure introduced into the hydraulic pilot port 17. , The normal relief pressure P1 lower than the set pressure P2 of the work actuator circuit B in the state where only the spring force acts.
(For example, 175 Kg / cm ² ) is set.

A pilot line 19 is branched and connected to a carryover conduit 18 for guiding the pressure oil discharged from the bypass passage of the outrigger control valve 3 to the work actuator circuit B, and this pilot line 19 is a hydraulic pilot for the outrigger relief valve 15. It is connected to port 17.

As a result, the pressure of the work actuator circuit B is introduced into the outrigger relief valve 15 as a pilot pressure, and when the work actuator circuit B operates, the set pressure of the outrigger relief valve 15 becomes higher than the work actuator circuit pressure. And, it rises as the working actuator circuit pressure rises.

Here, the set pressure upper limit value of the outrigger relief valve 15 is the set pressure P2 of the work relief valve 11.
It is set to a value equal to or higher than (for example, 250 Kg / cm ² ).

The specific value of this set pressure upper limit is the spring 1
It can be arbitrarily set by combining the spring constant of 6, the ratio of the piston diameter to the seat diameter of the slave valve, and the stroke of the piston.

Thus, when the work actuator circuit B is operated, the set pressure of the outrigger relief valve 15 is set to the same value as that of the circuit B.
Since it automatically increases to a value higher than the circuit pressure of, the circuit B can be operated at the maximum set pressure P2.

Moreover, since the circuit pressure of the work actuator circuit is introduced as pilot pressure into the outrigger relief valve 15, the set pressure is increased,
The external pressurizing valve 13 of FIG. 4, which is conventionally used, is unnecessary.

Second embodiment (see FIG. 2) Only differences from the first embodiment will be described.

The outrigger relief valve 20 includes a vent relief valve 21 and a pilot spool 2 for pressure switching provided in a vent line 22 of the vent relief valve 21.
3 and a low pressure setting valve 24 and a high pressure setting valve 25 connected in parallel to the outlet side of the pilot spool 23.
A pilot line 19 is connected to 3a.

The set pressure of the low pressure setting valve 24 is the normal relief pressure P1, and the set pressure of the high pressure setting valve 25 is the working relief valve 1.
The pressure is set to a value equal to or higher than the set pressure P2 of 1.

When the pilot pressure is not introduced, the pilot spool 23 is in the low pressure setting position (a) on the left side of the drawing, and the low pressure setting valve 24 (the setting pressure is, for example, 175 Kg / c).
m ² ) is selected. Therefore, in this state, the set pressure of the outrigger relief valve 20 becomes the normal relief pressure P1.

On the other hand, when the pilot pressure is introduced into the pilot spool 23, the spool 23 is switched to the high pressure setting position B, the high pressure setting valve 25 is selected, and the set pressure of the outrigger relief valve 20 becomes the work relief valve 11. Set pressure P
It is set to the same value as 2 or higher.

Third Embodiment (see FIG. 3) The outrigger relief valve 26 in this embodiment comprises a vent relief valve 27 and a pilot spool 29 provided in a vent line 28 of the vent relief valve 27. The pilot line 19 is connected to the hydraulic pilot port 29 a of 29.

The pilot spool 29 switches from the open position a shown in the drawing to the block position b against the spring 30 when the introduced pilot pressure exceeds a certain value, which is usually less than the relief pressure P1, and blocks the vent line 28. .

As a result, the outrigger relief valve 26 is shut off, and the work actuator circuit B operates with the pressure P2 set by the work relief valve 11 as the maximum pressure.

According to the configurations of the second and third embodiments, although the structure of the outrigger relief valves 20 and 26 itself is slightly more complicated than that of the first embodiment, the external booster valve 13 of FIG. 4 is used. Compared with the case, the circuit configuration becomes simpler, which is advantageous in terms of cost, reliability, and the like.

By the way, the set upper limit value of the outrigger relief valve 15 in the first embodiment and the high pressure set value of the outrigger relief valve 20 in the second embodiment are set to the maximum set pressure P2 of the work actuator circuit B, respectively. If so, the outrigger relief valves 15, 20
Since this substantially doubles as a work relief valve, the work relief valve 11 may be omitted.

Further, the present invention is not limited to the rough terrain crane, but can be widely applied to hydraulic working machines having a circuit configuration in which the low-pressure setting side circuit is arranged on the upstream side of the high-voltage setting side circuit, similarly to the rough terrain crane. You can

[0046]

As described above, according to the first, second or fourth aspect of the invention, the relief valve of the upstream side actuator circuit (outrigger circuit in claim 4) having a low maximum pressure set value is set in accordance with the pilot pressure. It is configured as a set pressure variable relief valve in which the set pressure changes, and the set pressure is increased by introducing the circuit pressure of the downstream actuator circuit (same working actuator circuit) as the pilot pressure into this relief valve. No boost valve is required.

Therefore, as compared with the case of using the conventional electromagnetic switching type booster valve, (i) the circuit configuration is simplified,
(Ii) Cost can be reduced, (iii) Less hydraulic piping is required, (iv) Electric wiring for interlocking with the control valve is not required, and anxiety factors such as poor contact of connector, corrosion of wiring, disconnection, etc. Disappears.

On the other hand, according to the invention of claim 3 or 4,
Although the pilot spool of the upstream relief valve is actuated by the downstream actuator circuit pressure to block the vent line of the relief valve and shut off the relief valve, the structure of the relief valve itself becomes a little complicated Compared with the case where the booster valve is used, the circuit configuration becomes simpler, which is advantageous in terms of cost and reliability.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

A Outrigger circuit as low pressure setting side actuator circuit B Working actuator circuit as high pressure setting side actuator circuit 1 Pump 2 Pump discharge line 3 Outrigger circuit control valve 4 Outrigger circuit cylinder 5 Working actuator circuit cylinder 6 Same control valve 11 Work actuator circuit relief valve 15 Outrigger circuit relief valve 16 Same relief valve spring 17 Same hydraulic pilot port 19 Pilot line 20 Outrigger circuit relief valve 21 Vent relief valve 22 same vent line 23 Same vent line 23 Same pilot spool 23a Pilot spool hydraulic pilot port 24 Low pressure setting valve 25 High pressure setting valve 26 Outrigger relief valve 27 Bent relief valve that constitutes an outrigger relief valve 28 same vent line 29 same pilot spool 30 same spring

─────────────────────────────────────────────────── ─── Continued Front Page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B66C 13/12 B66C 23/80 B66C 23/82 F15B 11/028

Claims (4)

(57) [Claims] 1. In a hydraulic actuator circuit of two systems having different maximum pressure set values driven by a common hydraulic pump, the one having a lower maximum pressure set value is on the upstream side, and the downstream side actuator when the upstream side actuator is operating. The relief valve that is connected to the circuit in the state where pressure oil is not supplied and that sets the maximum pressure of the upstream hydraulic actuator circuit is configured as a variable set pressure relief valve that changes the preset pressure according to the pilot pressure. The pressure of the downstream hydraulic actuator circuit is guided to the upstream relief valve via a pilot line when the actuator is not operated, and the set pressure of the relief valve is set to a value equal to or higher than the pressure of the downstream hydraulic actuator circuit. A hydraulic circuit of a working machine characterized by the above. 2. The hydraulic circuit for a working machine according to claim 1, wherein the set relief pressure of the upstream side relief valve is set to a value equal to or higher than the maximum pressure set value of the downstream side hydraulic actuator circuit when pilot pressure is introduced. A hydraulic circuit of a working machine characterized by the above. 3. In the hydraulic actuator circuits of two systems having different maximum pressure set values driven by a common hydraulic pump, the one having a lower maximum pressure set by each of the relief valves is on the upstream side, and the upstream side is on the other side. When operating the actuator, connect the downstream side actuator circuit in a state where pressure oil is not supplied, and provide a relief spool that sets the maximum pressure of the upstream side hydraulic actuator circuit with a pilot spool that closes the vent line when the external pilot pressure is introduced. A working machine configured to shut off the upstream relief valve by guiding the pressure of the downstream hydraulic actuator circuit to a pilot port of the pilot spool through a pilot line when the upstream hydraulic actuator is not operating. Hydraulic circuit. 4. The hydraulic circuit for a working machine according to claim 1, wherein an outrigger circuit for activating an outrigger of a hydraulic wheel crane is used as an upstream hydraulic actuator circuit, and a boom undulation is used as a downstream hydraulic actuator circuit. A hydraulic circuit for a working machine, to which a working actuator circuit for performing crane work such as hoisting is applied.