JPH09329106A - Hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize both a function to prevent fall of a load when piping is damaged and a regeneration function for energy-saving operation. SOLUTION: A flow control valve 21 is directly attached to a head side 11h to which a weight load is applied in a boom cylinder 11 of a hydraulic shovel. A fall-preventing circuit 31 and a regeneration circuit 41 provided close to the boom cylinder 11 side from this fall-preventing circuit 31 are integrally stored in the flow control valve 21. The fall-preventing circuit 31 discharges a return oil from the head side 11h of the boom cylinder 11 to a tank 13 through a fall-preventing valve element 34 interlockingly operated by a pilot pressure for boom lowering operation and gives sealing when there is no pilot pressure for boom lowering operation. The regeneration circuit 41 supplies a part of the return oil flowing out from the head side 11h of the boom cylinder 11 to the tank 13 through the fall-preventing circuit 31 to a rod side 11r of the boom cylinder 11 through a regeneration valve element 44 interlockingly operated by the pilot pressure for boom lowering operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit such as a hydraulic circuit having a fall prevention function in hydraulic excavators, hydraulic cranes and the like.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional hydraulic circuit of a hydraulic cylinder (hereinafter, referred to as a boom cylinder 11) that drives a boom in a hydraulic excavator using a load. The hydraulic source 12 and the tank 13 are a control valve 14 of a boom control valve. It is connected to the oil supply port and oil discharge port of the body (spool) 15, and the two output ports of the boom control valve body 15 are connected to the rod side 11r and the head side 11h of the boom cylinder 11 via the rod side line 16 and the head side line 17. It is in communication.

In the control valve 14 of this hydraulic excavator, a regeneration line 18a provided between the rod side line 16 and the head side line 17 for the purpose of energy saving operation,
A regeneration circuit 18 including a check valve body 18b and a pilot operated regeneration valve body 18c provided in the regeneration line 18a is provided.

During boom raising operation, pilot pressure is supplied to the boom raising pilot line 15up,
By moving the boom control valve body 15 to the left, the pressure oil supplied from the hydraulic power source 12 to the boom control valve body 15 is supplied to the head side 11h of the boom cylinder 11 via the head side line 17, and the boom cylinder Return oil from the rod side 11r of 11 enters the control valve 14 through the rod side line 16, is discharged to the tank 13 via the boom control valve body 15.

On the other hand, during the boom lowering operation, the pilot pressure is supplied to the boom lowering pilot line 15dn to move the boom control valve body 15 to the right, thereby the hydraulic power source is supplied.
The pressure oil supplied from 12 to the boom control valve body 15 is supplied to the rod side 11r of the boom cylinder 11 via the rod side line 16, and the return oil from the head side 11h of the boom cylinder 11 passes through the head side line 17. Then, it enters the control valve 14 through the boom control valve body 15 and is discharged to the tank 13.

During this boom lowering operation, the regeneration valve body 18c
Is switched to the communication state by the pilot pressure supplied via the pilot line 18d branched from the boom lowering pilot line 15dn, and the return oil that has flowed out from the head side 11h of the boom cylinder 11 to the head side line 17 is A part of it flows into the rod side line 16 on the pressure oil supply side through the check valve body 18b and the regeneration valve body 18c, and the boom cylinder 11
It is regenerated and supplied to the rod side 11r. Regeneration valve body 18c
Is switched to the shut-off state by the return spring 18e when there is no boom lowering pilot pressure from the pilot line 18d.

A regeneration circuit is provided in the control valve 14 as described above.
In addition to the hydraulic circuit equipped with 18, for the purpose of preventing the boom from dropping when the piping is damaged in a crane specification vehicle, etc.,
The fall prevention attachment 19 shown in may be directly attached to the oil port on the head side 11h of the boom cylinder 11.

The fall prevention attachment 19 includes a check valve body 19a provided in the head side line 17 and a head side line at a position closer to the boom cylinder than the check valve body 19a.
A tank line 19b that branches from 17 to tank 13;
This tank line 19b is composed of a pilot operated fall prevention valve body 19c.

The fall prevention valve body 19c is a pilot line 19d branched from a boom lowering pilot line 15dn.
It is switched to the communication state by the pilot pressure for boom lowering operation that is supplied via, and is switched to the shutoff state by the return spring 19e when there is no pilot pressure for boom lowering operation.

When the boom cylinder 11 is not operating, since the pilot pressure is not supplied to the boom lowering pilot line 15dn of the boom control valve body 15, the fall prevention valve body 19c is operated by the return spring 19e. It has been switched to the shut-off state shown in FIG. 3, and the return oil from the head side 11h of the boom cylinder 11 is sealed by the check valve body 19a and the fall prevention valve body 19c, and is kept below the check valve body 19a. Even if the pipe line is damaged in the head side line 17 on the side,
The rod 11R of the boom cylinder 11 does not contract and there is no danger of the boom descending.

The hydraulic circuit of the boom section shown in FIG. 3, which includes the control valve 14 having the regeneration circuit 18 built-in and the boom cylinder direct-connection type fall prevention attachment 19, operates as follows.

When the pilot pressure is supplied to the boom lowering pilot line 15dn of the boom control valve body 15 of the control valve 14, the boom control valve body 15 is switched to the right direction, and the pressure oil from the hydraulic pressure source 12 is transferred to the rod side. It is supplied to the rod side 11r of the boom cylinder 11 through the line 16.

At this time, the fall prevention valve body 19c in the fall prevention attachment 19 directly attached to the boom cylinder 11
On the other hand, the pilot pressure that has passed through the pilot line 19d acts and the fall prevention valve body 19c is switched to the communication state, so that all the return oil from the head side 11h of the boom cylinder 11 is in the communication state of the tank line 19b. Fall prevention valve body
It is discharged to tank 13 through 19c. Therefore, the rod 11R of the boom cylinder 11 contracts and the boom of the hydraulic excavator descends.

As described above, during the boom lowering operation, all the return oil from the head side 11h of the boom cylinder 11 flows directly to the tank line 19b through the fall prevention valve body 19c in the fall prevention attachment 19. Control valve
Returning to 14 and oil does not enter, regeneration circuit in control valve 14 18
No return oil is supplied.

[0015]

As described above, when the fall prevention attachment shown in FIG. 2 is not attached, the boom cylinder 11 is discharged from the head side 11h to the tank 13 via the head side line 17. A part of the return oil flows into the rod side line 16 on the pressure oil supply side through the check valve body 18b and the regeneration valve body 18c of the regeneration circuit 18 and is regenerated and supplied to the rod side 11r of the boom cylinder 11. , It is not possible to prevent the boom from falling when the pipe is damaged.

On the other hand, as shown in FIG. 3, when a boom cylinder direct attachment type fall prevention attachment 19 is used in combination with the control valve 14 having the regeneration circuit 18 shown in FIG. Return oil from the head side 11h of the boom cylinder 11 returns directly to the tank 13 via the fall prevention valve body 19c, so the return oil does not enter the control valve 14 and the regeneration circuit 18 such as the regeneration valve body 18c in the control valve 14 There is a problem that the oil does not flow back to and the regeneration function of the regeneration circuit 18 does not work.

The present invention has been made in view of the above points, and an object thereof is to achieve both a load drop prevention function at the time of pipe breakage and a regeneration function for energy saving operation.

[0018]

According to a first aspect of the invention, the load is reduced by supplying the pressure liquid to the rod side of the hydraulic cylinder and discharging the return liquid from the head side to the tank, and the head side. In the hydraulic circuit that raises the load by supplying the pressure liquid to the tank and discharging the return liquid from the rod side to the tank, an operation signal for lowering the load of the return liquid from the head side of the hydraulic cylinder is provided near the hydraulic cylinder. A drop prevention circuit that discharges it to the tank and seals it with other signals, and a part of the return liquid from the head side of the hydraulic cylinder to the tank that lowers the load. It is a hydraulic circuit provided with a regeneration circuit which supplies to the rod side by a signal.

The fall prevention circuit provided near the hydraulic cylinder exerts a fall prevention function when the pipe is damaged, and the regeneration circuit provided closer to the hydraulic cylinder than the fall prevention circuit saves energy. To exert the playback function for.

According to a second aspect of the present invention, in the hydraulic circuit according to the first aspect, the fall prevention circuit and the regeneration circuit are:
It is built in a flow control valve directly attached to the head side of the hydraulic cylinder.

By directly attaching the flow control valve to the head side of the hydraulic cylinder, the drop prevention circuit and the regeneration circuit are simultaneously set.

According to a third aspect of the present invention, the drop prevention circuit in the hydraulic circuit according to the first or second aspect is provided in a head side line connected to the head side of the hydraulic cylinder, and a return from the head side is provided. The check valve body that stops the liquid, the tank line that branches from the head side line to the tank at a position closer to the hydraulic cylinder than the check valve body, and the tank line that is connected in this tank line by the load lowering operation signal And a fall prevention valve body which is switched to a shutoff state by another signal.

When the return liquid is returned from the head side of the hydraulic cylinder to the tank by the load lowering operation signal, the fall prevention valve element in the tank line is switched to the communicating state. When there is no load lowering operation signal, the check valve body and the fall prevention valve body switched to the shut-off state seal the return fluid from the head side of the hydraulic cylinder to prevent the flow control valve from operating. Corresponds to the damage of the connected pipeline.

According to a fourth aspect of the present invention, the regeneration circuit in the hydraulic circuit according to the first or second aspect has a head side line connected to the head side and a rod side connected to the rod side of the hydraulic cylinder. A regeneration line provided between the line and a check valve body which is interposed in the regeneration line and enables the liquid flow from the head side to the rod side and stops the liquid flow in the opposite direction; and this check valve. A regeneration valve body is provided in the regeneration line together with the body and is switched to a communication state by a load lowering operation signal and is switched to a cutoff state by another signal.

When the return liquid is discharged from the head side of the hydraulic cylinder to the tank by the load lowering operation signal,
In the hydraulic cylinder, the head side where a heavy load acts may be higher in pressure than the rod side which receives the pressure liquid supply, so the regeneration valve element in the regeneration line is switched to the communicating state, and one of the return liquids discharged to the tank is Part is recycled to the rod side. At this time, the check valve body prevents the reverse flow from the rod side of the hydraulic cylinder to the head side. Further, when there is no load lowering operation signal, the regenerative valve body is switched to the shut-off state to seal the return liquid from the head side of the hydraulic cylinder together with the drop prevention circuit.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The same parts as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and the description thereof may be omitted.

FIG. 1 shows a hydraulic cylinder as a hydraulic cylinder (hereinafter referred to as a boom cylinder 11) which is driven by a boom constituting a front linkage of a hydraulic excavator as a load.
The hydraulic circuit of the
And the tank 13 are connected to the oil supply port and the oil discharge port of the boom control valve body (spool) 15 of the control valve 14, and the two output ports of the boom control valve body 15 are one rod side line 16 and the other head side line. It is communicated with the rod side 11r and the head side 11h of the boom cylinder 11 via 17.

The boom control valve body 15 of the control valve 14 is
When it receives pilot pressure from the boom lowering pilot line 15dn, it moves to the right to connect the hydraulic power source 12 to the rod side line 16 and the head side line 17 to the tank.
Pilot line 15 for communicating with 13 and raising the boom
When it receives pilot pressure from up, it moves to the left and the hydraulic pressure source
12 is connected to the head side line 17, and the rod side line 16 is connected to the tank 13.

The flow control valve 21 is directly attached to the oil port on the head side 11h of the boom cylinder 11. A drop prevention circuit 31 and a regeneration circuit 41 are integrally incorporated in the flow control valve 21.

The fall prevention circuit 31 is provided in the vicinity of the boom cylinder 11 and discharges the return oil from the head side 11h of the boom cylinder 11 to the tank 13 by a boom lowering operation signal, and a no signal state for boom stop is provided. The return oil from the head side 11h is sealed by other signals including the above.

The structure of this fall prevention circuit 31 is such that a check valve body (ball) for stopping return oil from the head side 11h is connected to the head side line 17a in the flow control valve 21 connected to the head side 11h of the boom cylinder 11. ) 32 is provided, and a tank line 33 from the head side line 17a to the tank 13 is branched at a position closer to the boom cylinder 11 than the check valve body 32, and a fall prevention valve body (spool) 34 is provided in the tank line 33. Is provided.

The fall prevention valve element 34 supplies the pilot pressure for boom lowering operation supplied on the pilot line 21a branched from the boom lowering pilot line 15dn on one side 34.
When the boom lowering pilot pressure is not received, the return spring 34b receives the biasing force from the opposite side and switches to the cutoff state.

The fall prevention circuit 31 switches the boom control valve body 15 by the pilot pressure for boom lowering operation supplied from the pilot line 15dn to cause the rod 11R of the boom cylinder 11 to contract while the head of the head is being retracted. When returning the return oil from side 11h to tank 13, the pilot pressure from pilot line 21a causes the tank line 33
The fall prevention valve body 34 inside is switched to a communication state.

On the other hand, when there is no pilot pressure for boom lowering operation, the check valve body 32 and the fall prevention valve body 34 switched to the shut-off state seal the return oil from the head side 11h of the boom cylinder 11. Boom cylinder 11 by stopping
Corresponding to the breakage of the external conduit (head side line 17) after the flow control valve 21 directly attached to.

Further, the reproducing circuit 41 includes a fall prevention circuit 31.
Further, it is provided on the side of the boom cylinder 11 and from the head side 11h of the boom cylinder 11 through the fall prevention valve body 34 to the tank.
A part of the return oil discharged to 13 is supplied to the rod side 11r by a boom lowering operation signal.

The structure of this reproducing circuit 41 is a boom cylinder.
A regeneration line 42 is provided between the head side line 17a in the flow control valve 21 connected to the head side 11h of 11 and the rod side line 16 connected to the rod side 11r of the boom cylinder 11. A check valve body (ball) 43 that allows oil flow from the head side 11h to the rod side 11r and stops the oil flow in the opposite direction is interposed in the 42, and along with this check valve body 43, in the regeneration line 42. Regeneration valve body (spool) 44
Is provided.

The regeneration valve element 44 receives the pilot pressure for boom lowering operation supplied from the pilot line 21a branched from the boom lowering pilot line 15dn on one side 44a and switches to the communicating state, and When there is no pilot pressure for lowering operation, return spring 44b
It receives the urging force from the other side and switches to the cutoff state.

Then, the regeneration circuit 41 switches the boom control valve element 15 by the boom lowering pilot pressure supplied from the pilot line 15dn to change the boom cylinder.
When the rod 11R of 11 is contracted and the return oil from the head side 11h of the boom cylinder 11 is discharged to the tank 13 through the narrowed internal flow passage of the fall prevention valve body 34, the boom load on the boom cylinder 11 Working head side 11
Since h may be higher than that on the rod side 11r that receives pressure oil supply, the pilot pressure from the pilot line 21a is used to switch the regeneration valve element 44 in the regeneration line 42 to the communicating state, so that the fall prevention valve element A part of the return oil discharged to the tank 13 via 34 is regenerated and supplied to the rod side 11r via the regeneration valve body 44. At this time, the check valve body 43 prevents the reverse flow from the rod side 11r of the boom cylinder 11 to the head side 11h.

On the other hand, when the pilot pressure for boom lowering operation is not present in the pilot line 21a, the regenerative valve element 44 is switched to the shut-off state by the return spring 44b, and the fall prevention circuit 31 and the head side 11h of the boom cylinder 11 are operated together. Seal the return oil.

Since internal oil leakage occurs in the drop prevention valve element 34 of the fall prevention circuit 31, this internal leakage oil is used as the tank line 33.
An oil drain passage 35 for discharging the oil is provided. Further, internal oil leakage also occurs in the regeneration valve element 44 of the regeneration circuit 41.
An oil drain passage 45 for discharging the oil is provided.

Next, the overall operation of the embodiment shown in FIG. 1 will be described.

By directly attaching the flow control valve 21 to the head side 11h of the boom cylinder 11, the fall prevention circuit 31 and the regeneration circuit 41 are set at the same time.

The drop prevention circuit 31 provided in the vicinity of the boom cylinder 11 has a boom fall prevention function for preventing the boom from dropping by its own weight in a hydraulic excavator or the like even if the head side line 17 is damaged thereafter. In addition to being exerted, the regeneration function for energy saving operation is exerted by the regeneration circuit 41 provided further to the boom cylinder 11 side than the fall prevention circuit 31.

That is, since the check valve body 32 and the fall prevention valve body 34 are built in the flow control valve 21 directly connected to the boom cylinder 11, the pilot pressure is supplied to the pilot line 15dn during the boom lowering operation. Then, the boom control valve body 15 is switched to the boom lowering side by the pilot pressure, and at the same time, the fall prevention valve body 34 is also switched to the communication state by the pilot pressure passing through the pilot line 21a, and the head side 11h of the boom cylinder 11h. The return oil that has flowed out of the oil is discharged to the drain line 33 through the drop prevention valve body 34.

At this time, since the common pilot pressure is also supplied to the regenerative valve body 44 through the pilot line 21a, the regenerative valve body 15 and the fall prevention valve body 34 are simultaneously regenerated.
44 also switches to the communication state, and the head side of the boom cylinder 11
Part of the return oil discharged to the tank line 33 from 11h
Regeneration is supplied to the rod side 11r of the boom cylinder 11 via the regeneration valve element 44 of the regeneration line 42.

During this boom lowering operation, the regeneration valve body 44
Even if the pressure on the rod side 11r of the boom cylinder 11 becomes higher than the pressure on the head side 11h in the state in which is switched, the check valve body 43 prevents the reverse flow.

On the other hand, when the pilot pressure is supplied from the pilot line 15up on the opposite side to the boom control valve body 15,
The boom control valve body 15 is switched to the boom raising side, but the pilot pressure for switching is not supplied to the fall prevention valve body 34 and the regeneration valve body 44, and the fall prevention valve body 34 and the regeneration valve body 44 are returned to the return spring 34b. , 44b are in the cutoff state.

Therefore, the pressure oil discharged from the hydraulic pressure source 12 such as a hydraulic pump is supplied from the boom control valve body 15 to the head side 11h of the boom cylinder 11 via the head side line 17 and from the rod side 11r to the rod side. The return oil pushed out to the line 16 is discharged to the tank 13 via the boom control valve body 15.

Further, when the boom control valve body 15 is in the neutral state, even if the head side line 17 of the boom cylinder 11 is damaged due to an increase in the load applied to the boom or the like, the boom lowering pilot pressure is reduced. Since the drop prevention valve body 34 and the regeneration valve body 44 of the flow control valve 21 without a signal are in the shutoff state, the return oil from the head side 11h of the boom cylinder 11 is shut off by the check valve body 32 and the shutoff valve body 32 of the flow control valve 21. The fall prevention valve element 34 and the regeneration valve element 44 in the state are sealed to prevent the boom from falling.

As described above, in the method of providing the regeneration circuit 18 in the control valve 14 of the prior art (FIG. 3), the regeneration function of the regeneration circuit 18 is lost when the fall prevention attachment 19 is attached to the boom cylinder 11. However, according to the present invention, the flow control valve 21 includes the fall prevention circuit 31 and the fall prevention circuit.
Since the regeneration circuit 41 is incorporated with priority over 31, the flow control valve 21 may be directly attached to the boom cylinder 11, but a part of the return oil when the boom is lowered is passed through the regeneration circuit 41 to the boom cylinder 11. Since it is supplied to the rod side 11r, the regeneration function is not impaired.

Next, another embodiment (not shown) of the present invention will be described.

The present invention is not limited to the hydraulic circuit, but includes a hydraulic circuit that operates with a hydraulic fluid equivalent to hydraulic fluid.

Furthermore, the present invention is not limited to the application to the boom cylinders of hydraulic excavators and hydraulic cranes, but can also be applied to other hydraulic cylinders to which a large load is applied.

Further, in the illustrated embodiment, the load lowering operation signal is the pilot pressure, but the load lowering operation signal may be an electric signal. In that case, the boom control valve body 15, the fall prevention valve body 34, and the regenerative valve body 44 may be of a solenoid-based excitation operation system.

In addition, the invention according to claim 1 includes a case where the fall prevention circuit 31 and the reproduction circuit 41 are separately installed. That is, there are cases where the fall prevention circuit 31 and the regeneration circuit 41 do not necessarily have to be housed in one flow control valve 21.

[0056]

According to the first aspect of the invention, the fall prevention circuit provided in the vicinity of the hydraulic cylinder can ensure the fall prevention function for preventing the load from dropping when the pipe is broken, and the fall prevention circuit. Further, the regeneration circuit provided on the hydraulic cylinder side can ensure the regeneration function for energy saving operation.

According to the second aspect of the present invention, the drop prevention circuit and the regeneration circuit can be compactly integrated by the flow control valve directly attached to the head side of the hydraulic cylinder, and these can be combined together. Can be set at the same time.

According to the third aspect of the invention, when there is no load lowering operation signal, the check valve body and the fall prevention valve body switched to the shut-off state return from the head side of the hydraulic cylinder. By sealing the liquid, it is possible to deal with breakage of the pipeline connected to the flow control valve.

According to the fourth aspect of the invention, when the return liquid is discharged from the head side of the hydraulic cylinder to the tank in response to the load lowering operation signal, the regeneration valve element in the regeneration line is switched to the communicating state to return the return liquid. By regenerating and supplying a part of the above to the rod side, it is possible to effectively use the high pressure liquid on the head side where a heavy load acts in the hydraulic cylinder, and to save energy.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic circuit according to the present invention.

FIG. 2 is a hydraulic circuit diagram showing an example of a conventional hydraulic circuit.

FIG. 3 is a hydraulic circuit diagram showing another example of a conventional hydraulic circuit.

[Explanation of symbols]

 11 Hydraulic cylinder as hydraulic cylinder 11r Rod side 11h Head side 13 Tank 16 Rod side line 17, 17a Head side line 21 Flow control valve 31 Fall prevention circuit 32 Check valve body 33 Tank line 34 Fall prevention valve body 41 Regeneration circuit 42 Regeneration line 43 Check valve body 44 Regeneration valve body

Claims (4)

[Claims] 1. A load is reduced by supplying the pressure liquid to the rod side of the hydraulic cylinder and discharging the return liquid from the head side to the tank to supply the pressure liquid to the head side and returning from the rod side to the tank. In a hydraulic circuit that increases the load by discharging the liquid, the return liquid from the head side of the hydraulic cylinder, which is provided near the hydraulic cylinder, is discharged to the tank by the load lowering operation signal and sealed by other signals. A prevention circuit and a regeneration circuit provided further on the hydraulic cylinder side than the drop prevention circuit and supplying a part of the return liquid from the head side of the hydraulic cylinder to the tank to the rod side by a load lowering operation signal. A hydraulic circuit characterized by. 2. The hydraulic circuit according to claim 1, wherein the drop prevention circuit and the regeneration circuit are integrally incorporated in a flow rate control valve directly attached to the head side of the hydraulic cylinder. 3. A drop prevention circuit is provided on a head side line connected to the head side of a hydraulic cylinder, and a check valve body for stopping return liquid from the head side; and a check valve body closer to the hydraulic cylinder than the check valve body. The tank line that branches from the head side line to the tank at the position of and the fall prevention valve element that is provided in this tank line and that switches to the communication state by the load lowering operation signal and switches to the cutoff state by another signal. The hydraulic circuit according to claim 1 or 2, further comprising: 4. The regeneration circuit includes a regeneration line provided between a head side line connected to the head side of the hydraulic cylinder and a rod side line connected to the rod side, and a regeneration line interposed in the regeneration line. A non-return valve body that enables the liquid flow from the head side to the rod side and stops the liquid flow in the opposite direction, and a check valve body that is provided together with this non-return valve body in the regeneration line to switch the communication state by a load lowering operation signal 3. The hydraulic circuit according to claim 1, further comprising a regenerative valve body that is switched to a shutoff state by another signal.