JP3065460B2 - Hydraulic circuit for cylinder operation - 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 circuit for operating a cylinder in a high-pressure casting machine, an injection molding machine, a press machine or the like.

[0002]

2. Description of the Related Art A schematic structure of a vertical high-pressure casting machine which is an example of this type of apparatus is shown in FIG. The slide 41 to which the upper mold is attached is guided by the four columns 42, and is moved up and down by the two right and left hydraulic cylinders 16A and 16B. The upper mold is lowered, pressed against a lower mold (not shown) fixed below, the half nut 43 is engaged with the column 42, and the four mold clamping cylinders 44 are connected to the half nut 43.
After applying a hydraulic pressure by contacting the mold, the injection cylinder 45 provided below after obtaining a predetermined mold clamping force injects the molten aluminum into both molds. Hydraulic cylinder 16
Lifting of A and 16B is performed by a hydraulic circuit shown in FIG. When ascending, the flow rate is controlled by an elevating control valve 9 comprising an electromagnetic proportional directional flow control valve, and the positions of the hydraulic cylinders 16A, 16B are measured by position sensors or limit switches, and acceleration, steady state,
Control of deceleration and control of a stop position are performed.

[0003] In addition to the above-described methods, the above-described flow control or speed control methods include a flow control method using a variable pump,
There is also a flow control method for sequentially controlling the on-load of a plurality of pumps, or a method using both an electromagnetic switching valve and a flow control valve as in the prior art disclosed in Japanese Patent Publication No. 3-35019. In addition, in order to increase the elevating speed, a method of joining return oil from a cylinder to a feed side by using a regenerating circuit system has been implemented. On the lower side of the lifting cylinder, in addition to the flow rate control described above, in order to prevent the slide 41 and the upper mold from self-running due to its own weight load, as shown in FIG. It descends at a flow rate commensurate with the supply flow rate. In addition, the pilot pressure of the electromagnetic hydraulic switching valve can be divided into a method having a pump dedicated to the pilot pressure and a method using the self pressure as the pilot pressure. This is advantageous in terms of equipment cost.

[0004]

However, in the case of this type of elevating device, the lowering speed of the elevating cylinder cannot be made faster than a value corresponding to the pump flow rate. Therefore, as a countermeasure, if the counterbalance valve 38 is omitted and the oil on the head side of the lift cylinder is caused to flow out by its own weight load, and the speed is made higher than the pump flow rate, the supply flow rate to the rod side becomes insufficient. Cavitation occurs on the rod side. As a result, at the lower limit, the upper mold and the lower mold come into contact with each other, and the elevating cylinder stops, so it takes time for the pressure on the rod side to rise. The pump pressure decreases due to an undesired shortage of the supply flow rate to the rod side, lowering than the required pilot pressure of the electromagnetic hydraulic switching valve, and the valve cannot be switched.
In particular, for an electromagnetic proportional flow control valve, the pilot pressure is 30
Since a pressure of about Kg / cm ² is necessary, there are various problems such as a decrease in pump pressure which is troublesome in terms of control.

On the other hand, in the hydraulic circuit shown in FIG.
When increasing the lifting speed of the lifting cylinder, the pressure oil in the rod-side oil chamber is switched by switching the lifting / lowering control valve 9 to the rising side and switching the regeneration (differential) control valve 10 from the illustrated operation position. The speed can be increased by returning to the head side oil chamber through the line 104, but the regeneration control valve 10
Means that three ports conduct during this switching,
Some of the three ports are blocked,
In the former conduction type, the oil flowing from the pipe 101 to the head side flows from the pipe 104 to the pipe 103 via the regeneration control valve 10 to be connected to the tank, and the speed of the lifting / lowering cylinder stops or decelerates instantaneously. Cause a shock. In the latter block type, line 102 → regeneration control valve 10 → line 103 → elevating control valve 9 → oil flowing to the tank is momentarily shut off during switching, and the movement of the elevating cylinder stops. And cause a great shock. Such a shock similarly occurs when switching in the deceleration direction. Such a shock generally occurs not only with the hydraulic cylinder for lifting and lowering but also with the expansion and contraction operation of the hydraulic cylinder.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object of the present invention is to eliminate mechanical shocks at the time of increasing / decreasing speed control in a hydraulic circuit for operating a cylinder. It is an object of the present invention to secure control reliability by preventing cavitation in a hydraulic cylinder for lifting and to improve productivity by realizing high-speed lifting and lowering.

[0007]

The present invention has the following configuration to achieve the above object. That is, the present invention provides a hydraulic cylinder that performs an operation of raising and lowering a load of its own weight in an elevating device, an elevating control valve that maintains a pilot pressure at a predetermined value, and supplies hydraulic oil to the hydraulic cylinder to perform an ascending and descending operation, A flow control valve for reducing the flow rate of hydraulic oil from the hydraulic cylinder to the tank line when the weight load is lowered, and a head-side oil chamber and a rod-side oil chamber of the hydraulic cylinder on the load side of the lift control valve when the weight is lowered. And a control valve for restricting the flow of pressurized oil from the hydraulic pump to the hydraulic cylinder when descending.

Further, according to the present invention, the hydraulic cylinder is connected to an elevating device so as to increase the volume of the rod-side oil chamber when the self-weight load decreases, and the hydraulic pump controls the discharge pressure when the self-weight load decreases. A hydraulic circuit for operating a cylinder, which is driven so as to be maintained at a higher pressure than the pilot pressure, and wherein the elevation control valve is formed as a self-pressure control valve. Further, according to the present invention, the discharge pressure of the hydraulic pump is set to a value lower than the maximum set pressure of the relief valve provided in the hydraulic circuit while the self-weight load is decreasing, and after the completion of the decrease, the set pressure maximum is set. This is a hydraulic circuit for operating a cylinder, which is set to a value.

[0009] The present invention includes a hydraulic double-acting circuit to extend or reduce the connected piston rod switched pressure source and a tank to the hydraulic cylinder, the pressure source containers product increased side oil chamber that put the hydraulic cylinder A differential circuit for connecting and allowing only the flow of the pressurized oil from the volume-decrease-side oil chamber to the volume-increase-side oil chamber, and a switching device for switching between the hydraulic double-acting circuit and the differential circuit. During switching between the hydraulic double-acting circuit and the differential circuit, the switching device connects the three pipelines of the volume decreasing oil chamber, the volume increasing oil chamber, and the tank, and then switches from the volume decreasing oil chamber to the tank. A switching control means for interrupting the flow of the pressure oil while restricting the flow of the pressure oil.

[0010]

According to the present invention, when the self-weight load of the lifting device is lowered, the flow rate flowing out of the volume reduction side oil chamber of the hydraulic cylinder to the tank is reduced by the flow control valve, so that the lowering speed can be controlled. In this case, since the oil chamber on the volume decreasing side and the oil chamber on the volume increasing side are connected, the pressure becomes statically the same, and high-pressure oil flows into the oil chamber on the volume increasing side from the oil chamber on the volume decreasing side. , No cavitation occurs. Also,
The pump discharge oil is restricted from flowing into the oil chamber on the volume increasing side by the control valve, and is maintained at a pressure higher than the pilot pressure of the elevation control valve. Therefore, the direction switching and the opening degree control are reliably performed by the elevation control valve. I can do it. As a result, it is possible to descend at a speed higher than the speed corresponding to the pump flow rate.

Further, according to the present invention, the discharge pressure of the hydraulic pump is set to a value lower than the maximum set pressure of the relief valve provided in the hydraulic circuit while the self-weight load is falling, and By changing the setting to the maximum set pressure, the clamping force by the hydraulic cylinder after machining is stopped can be easily increased by increasing the pump pressure.

Further, according to the present invention, during the switching of the hydraulic circuit, after connecting the three-system pipes of the hydraulic cylinder, the oil chamber on the volume decreasing side, the oil chamber on the volume increasing side, and the tank, the oil chamber is switched from the oil chamber on the volume decreasing side. By shutting down the flow of the pressure oil to the tank while restricting the flow, the pressure oil flowing from the pressure source always flows stably to the volume increase side oil chamber, while the return oil from the volume decrease side oil chamber is Since the flow to the tank and the circulation to the oil chamber on the volume increasing side are smoothly switched, a smooth shift without any shock is possible.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a hydraulic circuit diagram of a vertical aluminum high-pressure caster according to one embodiment of the present invention. The illustrated hydraulic circuit includes two variable displacement hydraulic pumps 1A,
1B, a hydraulic power source device 3 including an oil tank 2, a filter 21, and a cooler 22, and an electromagnetic pilot type unload relief valve 4A, 4B, a check valve 5, and a merge control valve device 6. A hydraulic control unit 7, a check valve 8, an elevation control valve 9 realized by an electromagnetic proportional directional flow control valve, a regeneration control valve 10 realized by an electromagnetic switching valve, a check valve 11, a check valve 12, a relief valve 13, A load-side control unit 15 including a pilot check valve 14 and a lift / lower operation of an upper mold which is a load of its own weight 2
And two hydraulic cylinders 16A and 16B connected in parallel.

The hydraulic pump 1A has a discharge capacity of, for example, up to 80
1 / min, used as a 210K (Kgf / cm ² ) system pressure source, and the hydraulic pump 1B has a discharge capacity of, for example, a maximum of 130 l / min.
And is used as a pressure source of a 150K (Kgf / cm ² ) system.
The hydraulic control unit 7 is configured as a control device for controlling the pressure, the flow rate, and the merging between the two systems having two circuit pressures of 150 K (B) and 210 K (A). The 150K (B) system mainly forms an injection circuit and a mold clamp circuit, accumulates pressurized oil in an accumulator (not shown), and is used as a pressure source. On the other hand, 21
The 0K (A) system forms a circuit for raising and lowering the mold, clamping the mold, knocking out the product, and the like. In the direct pressure type or half nut type mold clamping, the capacity of the elevating cylinder and the mold clamping cylinder becomes large.
A alone cannot cope with it, and the flow rate is increased by merging from the 150K hydraulic pump 1B to adapt to the load.

In the hydraulic control unit 3, the unload relief valve 4A, which is pilot operated by the electromagnetic switching valves 17 and 18, holds the pipeline A at a pressure of 210 Kgf / cm ^{2 in} a steady state and a relief state in a standby state. Valve 20
And the unload relief valve 4B, which is pilot operated by the electromagnetic switching valve 19, operates at a pressure of 35 Kgf / cm ^2.
It operates to maintain the pipe line B at a pressure of 0 Kgf / cm ² . On the other hand, the check valve 5 is interposed in the middle of the 150K-system feed-side hydraulic piping so as to prevent backflow to the pressure source side. control valve device connection location (confluence line connection locations) as close as possible to the feed pipe passage part B ₂ of the 6 are preferred.

In the present embodiment, the merge control valve device 6 includes a pilot-operated poppet valve 23, an electromagnetic switching valve 24 for pilot operation, and a shuttle valve 25. In the poppet valve 23, the port P1 on the inlet side is the hydraulic pump 1
A pipe A connected to the discharge side of the hydraulic pump 1A has a port P2 on the outlet side connected to the pipe B connected to the discharge side of the hydraulic pump 1A.
Are respectively branched and connected. The electromagnetic switching valve 24 has a P port connected to the port P1 of the poppet valve 23, a T port connected to the tank line, one switching port A connected to one inflow port of the shuttle valve 25, and the other switching port. Port B is blocked. The shuttle valve 25 has the other inflow-side port connected to the port P <b> 2 of the poppet valve 23, and a common outflow-side port connected to a spring chamber serving as a pilot operation part of the poppet valve 23.

In the load-side control unit 15, the lift control valve 9 has a tank port connected to the tank line and a pressure source port connected to the terminal of the pipe A via the check valve 8 in series. One switching port is connected to both hydraulic cylinders 16 via a pilot check valve 14 in series.
A, 16B are connected to the head-side oil chambers, and the other switching ports are connected via the regeneration control valve 10 to both hydraulic cylinders 16A, 16B.
16B is connected to the rod side oil chamber. Check valve 8
It is provided so as to allow the pressure oil to flow from the hydraulic pump 1 </ b> A toward the elevation control valve 9.

As described above, the regeneration control valve 10 has one port on the pressure source side connected to the other switching port of the elevation control valve 9, and the other port ascends and descends via the check valve 11 in series. It is connected to one switching port of the control valve 9. As described above, one port on the load side is connected to the rod-side oil chambers of both hydraulic cylinders 16A and 16B, and the other port is connected to one of the lift control valves 9 via the check valve 12 in series. Connected to switching port. In addition, the check valve 11 is configured such that the hydraulic oil is
The check valve 12 is provided to allow flow from the rod-side oil chambers 6A and 16B to the head-side oil chambers of the hydraulic cylinders 16A and 16B for lifting and lowering via the regeneration control valve 10 side. Oil is provided so as to allow oil to flow from the head sides of the two hydraulic cylinders 16A and 16B toward the rod-side oil chamber via the pilot check valve 14 and the regeneration control valve 10.

Each of the pilot control valve 14, which is pilot operated by the elevation control valve 9, the regeneration control valve 10, and the electromagnetic switching valve 27, is provided so as to operate using its own pressure, which is the pressure of the pipe A, as a pilot pressure. The pilot check valve 14 is interposed in a pipe connecting the elevation control valve 9 and the head-side oil chambers of the hydraulic cylinders 16A and 16B. The overload relief valve 13 is
It is branched and connected to a pipe line connecting the head side oil chambers of both hydraulic cylinders 16A and 16B and the pilot check valve 14.

The mode of operation of raising and lowering the own weight load by the hydraulic circuit shown in FIG. 1 will be described below. Here, the area ratio between the cylinder head side oil chamber and the cylinder rod side oil chamber of both hydraulic cylinders 16A and 16B is 2: 1, and the load pressure is 50 kgf /.
cm ² (100 kgf / cm ² at the time of regeneration operation). (1) At the time of elevating stop: The hydraulic pump 1A is connected to the electromagnetic switching valve 18
Is turned on, the electromagnetic switching valve 17 is turned off, and the relief is performed at 35 Kgf / cm ² by the unload relief valve 4A.
On the other hand, when the charging of the accumulator (not shown) is completed, the hydraulic pump 1B is turned off by the unload relief valve 4B.
To the relief state. In the merging control valve device 6, the electromagnetic switching valve 24 is off, and the pipe A has a low pressure of 35 Kgf / c.
m ^{2 is} in a standby state, and pipes B _{1 and} B ₂ are 150 K
gf / cm ² .

(2) When ascending: The elevation control valve 9 is switched to the position (c), and the electromagnetic switching valve 17 is turned on to operate the unload relief valve 4A on-load. When the position is switched from (b) to (c) by the lift control valve 9, current control is performed so that the lift cylinder including the two hydraulic cylinders 16A and 16B rises in a predetermined speed pattern. The set pressure of the unload relief valve 4A is from 35 Kgf / cm ² to 21
0 kgf / cm ² , and the pressure of the hydraulic circuit from the pipe line A and the load side control unit 15 to the hydraulic cylinders 16A and 16B rises to 50 kgf / cm ^2, which is a pressure appropriate for the load, and the pilot check valve Oil flows into the oil chamber on the head side through 14, the oil in the oil chamber on the rod side returns to the tank, and the hydraulic cylinders 16A and 16B start to move to a speed corresponding to the discharge amount of the hydraulic pump 1A. Here, the regeneration control valve 10 is
When the position is switched from (e) to (d), the return oil from the rod-side oil chamber flows into the head-side oil chamber via the check valve 11, and the speed is doubled. The discharge pressure of the hydraulic pump 1A is calculated from 50 Kgf / cm ² by simple calculation, ignoring the pressure loss at each part.
Increase to 00 Kgf / cm ² . In this case, the presence of the check valve 11 prevents the pump discharge oil from flowing into the tank line via the regeneration control valve 10 during the switching of the regeneration control valve 10.

After a short time has elapsed, the electromagnetic switching valve 24 is excited and switched. The oil in the spring chamber of the poppet valve 23 is
It flows through the shuttle valve 25 to the tank and the poppet valve 2
3 is stroked open. The opening of the poppet valve 23 suddenly increases, and the discharge oil of the hydraulic pump 1B joins the hydraulic cylinders 16A and 16B and rises at the highest speed. Meanwhile, when the poppet valve 23 is opened, pressure oil of the pipe line B ₁ represents but merges into the distribution line A side, the pipe path B ₂ side will remain high by inhibiting the action of the check valve 5. Therefore, the high-pressure portion to be confluent part, only a short portion of the pipe path B _1, volume of oil converging portion decreases, small shock when switching, therefore, possible to shorten the switching time, of course, correspondingly cycle Time will be shorter. Note that when decelerating / stopping, the above is reversed. That is, the speed decreases when the poppet valve 23 opens → closes, the speed decreases when the regeneration control valve 10 (d) → (e), and the unload relief valve 4
When A is unloaded, the speed further decreases → stops, and the load-side lifting / lowering control valve 9 returns to the neutral position from (c) → (b) to hold the stop. In the deceleration control, current control of the elevation control valve 9 is performed so that a predetermined speed pattern is obtained. Flow control is
This may be performed by the elevation control valve 9, by controlling the discharge amount of a variable pump, or by controlling the merging order of the pumps as a combination of a plurality of pumps. Further, the order of the reproduction circuit control and the merge control may be reversed.

(3) At the time of descending: the pipe A is at a low pressure of 35 Kgf / cm ²
Is in standby mode. Turn the regeneration control valve 10 to (e)
→ The position is switched to (f), and the electromagnetic switching valve 27 of the pilot check valve 14 is turned on.
Is switched from (b) to (a). In this case, since the pump pressure is 35 Kgf / cm ^2, it is of course possible to switch the pilot check valve 14 by switching the electromagnetic switching valve 27. By switching the regeneration control valve 10, the head side pressure increases from 50 Kgf / cm ² to 100 Kgf / cm ² , while the rod side pressure increases from 0 Kgf / cm ² to 100 Kgf / cm ^2. When 10 comes to the position (a), the pressure oil in the head side oil chamber flows through the valve 10 to the tank line. Oil flows from the head-side oil chamber to the rod-side oil chamber via the check valve 12 and the regeneration control valve 10 by an amount corresponding to the lowering of the hydraulic cylinders 16A and 16B, so that cavitation does not occur in the rod-side oil chamber.

The flow rate of the outflow from the head side oil chamber is controlled by the throttle of the spool of the elevation control valve 9 and flows into the tank.
The descending speed is controlled. When the lift control valve 9 is in the position (a),
The rod-side oil chambers of the hydraulic cylinders 16A, 16B and the hydraulic pump 1A are connected via a check valve 8, but the rod-side oil chamber is 100 kgf / cm ² , and the pump discharge oil is 35 kgf.
/ cm ² , so that the oil in the rod-side oil chamber does not flow back to the pump side, and the pump discharge oil does not flow into the rod-side oil chamber. In this case, the pump pressure is 35 Kgf / cm ² ,
Since it can be sufficiently used as the pilot pressure of the elevation control valve 9 and is relieved at a low pressure, the circuit is an energy saving circuit. In the case of a variable pump, if the amount of displacement of the pump is reduced by reducing the amount of tilting of the pump, more energy can be saved. Further, the electromagnetic switching valve 17 is switched to the ON position, and the set value of the unload relief valve 4A is set to 210 kgf.
At / cm ² , the pump discharge oil flows into the cylinder rod-side oil chamber via the check valve 8, and the lowering speed of the cylinder naturally increases.

As an alternative to the restriction of the elevation control valve 9, a slow return check valve for restricting the oil flowing out of the head side oil chamber may be interposed at the pipe I in FIG. 1 and used. Also, as the elevation control valve 9, an electromagnetic hydraulic switching valve is used instead of the proportional valve, and the flow rate control for acceleration and deceleration is such that the switching speed of the switching valve is controlled by restricting the pilot line of the electromagnetic hydraulic switching valve. It may be something. The lowering speed is determined by the load pressure and the opening of the control throttle, and is not affected by the pump discharge amount. Since the load pressure is substantially constant, the maximum value of the lowering speed is determined by the maximum opening of the control throttle.

(4) At the end of lowering: When the upper die and the lower die are brought into low-speed contact by the current control of the raising / lowering control valve 9 so as not to cause an impact, the lowering of the hydraulic cylinders 16A and 16B stops. , The head pressure decreases. At this time, the relief valve 4A
Is changed to 210 Kgf / cm ² , the pump pressure increases and 1
When the pressure exceeds 00 Kgf / cm ² , the check valve 8 is pushed up to cause the pressure oil to flow into the rod-side oil chamber, and the pressure is increased to 210 Kgf / cm ² to tighten the upper mold and the lower mold. Next, referring to FIG. 5, the operation proceeds to the operation of the mold clamping cylinders 44A and 44B. At this point, the preliminary mold clamping by the hydraulic cylinders 16A and 16B has already been performed, and the next injection step can be started at the same time. Although the pump pressure temporarily drops when the mold clamping cylinders 44A and 44B are moved, the pressure in the rod-side oil chambers of the hydraulic cylinders 16A and 16B is held by the check valve 8 (although there is a slight pressure drop due to valve leak). .

As described above, the discharge pressure of the hydraulic pump 1A is set to a value lower than the maximum set pressure of the relief valve 4A provided in the hydraulic circuit during the lowering of the hydraulic cylinders 16A and 16B, and the lowering is completed. The set pressure is changed to the maximum value of the set pressure from immediately before to the time when the descent is completed. On the other hand, when the check valve 12 is lowered, the head-side oil chamber is connected to the rod-side oil chamber so that the head-side oil chamber is Provision is made to prevent backflow into the chamber, so that the clamping force can be applied by the hydraulic cylinders 16A and 16B immediately after the lowering stop. Further, by providing the check valve 8, the pump pressure is reduced by the hydraulic cylinders 16A, 16A.
Even if the load pressure is lower than the load pressure of B, there is no backflow, and the energy saving effect by the reduction of the pump pressure is high.

The embodiment described above is an example of a control method using self-pressure as the pilot pressure of the elevation control valve, but the hydraulic pump 1 is used as the pilot pressure source.
In the case of an external pressure source using a hydraulic pump separate from A, the control of the lowering of the lift cylinder is performed in the same manner as in the embodiment, and the same operation and effect can be exhibited. Needless to say, such modifications are also included in the scope of the present invention.

Next, FIGS. 2, 3 and 4 are hydraulic circuit diagrams showing main parts according to other embodiments of the present invention. In each of these embodiments, the same reference numerals are given to members corresponding to and corresponding to the embodiment shown in FIG. First, FIG.
Is a control valve device 29 including a poppet valve 23A, an electromagnetic switching valve 24A for pilot operation, and a shuttle valve 25A, that is, a device having the same structure as the merge control valve device 6 is added to the check valve 12. It is noteworthy that the replacement is provided. In this example, by controlling the pressure of the spring chamber of the poppet valve 23A, the check function can be exerted only when the hydraulic cylinder is lowered, and the other parts can be closed, which is substantially the same as the embodiment shown in FIG. Can perform functions.

The point shown in FIG. 3 is a poppet valve 23B and an electromagnetic switching valve 24B for pilot operation.
, A control valve device 30 including a check valve 31 and a check valve 32 is provided in place of the check valve 11 and the check valve 12, and a poppet valve 23C, an electromagnetic switching valve 24C for pilot operation, and a check valve 26 are provided. , 3
The control valve device 33 composed of the throttle valves 4 and 35 and the throttle 36 is provided in place of the regeneration control valve 10. When the electromagnetic switching valve 24B is in the illustrated neutral position (m), the poppet valve 23B is closed, the electromagnetic switching valve 24C is in the off position illustrated, and the poppet valve 23C is open, and the elevating control valve 9 is positioned (c). )
By setting the hydraulic cylinders 16A, 16A
B operates upward.

By setting the electromagnetic switching valve 24B to the position (n), the poppet valve 23B becomes a check valve that allows the flow from the rod side to the head side.
The same function as 1 is performed, and at the same time, the electromagnetic switching valve 24C is switched to the ON position to close the poppet valve 23C, thereby functioning as a regeneration circuit. When descending, position the elevation control valve 9
(a), the electromagnetic switching valve 24C is turned off, the poppet valve 23C is opened, and the electromagnetic switching valve 24B is switched to the position (1) to open the poppet valve 23B. It performs the same function as. Thus, it is clear that the example of FIG. 3 performs the same function as the embodiment shown in FIG.

It should be noted that in the example shown in FIG.
The regeneration control valve 10 and the check valve 1 in the embodiment shown in FIG.
Omitting 1, 12 and replacing pilot check valve 3
7 is connected across the head side pipe and the rod side pipe,
The point is that the pilot check valve 14 and the pilot check valve 37 can be alternately checked and opened by the pilot switching electromagnetic switching valve 38. In this example, when ascending, the pilot check valve 37 is opened by the pilot pressure, and the elevating control valve 9 is set to the position (C ₁ ), so that it can function as a regeneration circuit. At the time of descending, the pilot check valve 37 acts as the check valve 12 from the head side to the rod side. Therefore, the function at the time of descending is the same as that of the embodiment shown in FIG.

FIG. 5 is a hydraulic circuit diagram showing a main part of the load-side control unit 15 according to another embodiment of the present invention. In the other embodiments, the same reference numerals are given to members corresponding to and corresponding to the embodiment shown in FIG. In the example shown in FIG. 5, the hydraulic cylinder 16A for raising and lowering the self-weight load of the lifting device is provided so as to support the self-weight load from below with a piston rod, and the ascending volume increasing side oil on the side receiving the self-weight load. The ratio of the pressure receiving area A _H of the head-side oil chamber, which is the chamber, the pressure receiving area A _R of the rod-side oil chamber, which is the ascending volume decreasing oil chamber, to the cross-sectional area _AD of the piston rod is 2: 1: 1. It is assumed that a structure having the following structure is used. In the hydraulic circuit shown in FIG. 5, a differential control valve 10B is used instead of the regeneration control valve 10 in FIG. As the differential control valve 10B, a three-port indirect-acting pilot-type switching valve is used, and an electromagnetic switching valve 51 is provided.
Check valves with throttles 52 and 53 are provided. Of the three ports X, Y, and Z, the port X is connected to the load-side switching port of the elevation control valve 9 via the line 103, and the port Y is connected to the line 1
Connected to the downstream port of the check valve 11 via 05,
Port Z which switches to those ports X and Y to make them conductive
Is connected to the rod-side oil chamber via a conduit 102.

When the hydraulic cylinder 16A is operated at a normal elevating speed, the differential control valve 10B is switched to the position (g) so that the port X and the port Z conduct, and the port Y
Blocks. On the other hand, when increasing the speed and performing the ascending operation, the position is switched to the position (e), the ports Y and Z are conducted, and the port X is blocked. In this case, during the operation of, for example, 0.4 seconds when the position is switched from the position (g) to the position (e), the position is changed from the position (f ₂ ) where the three ports X, Y, and Z communicate with each other to the position (f ₁ ). In succession, the ports Y and Z are kept conductive, the port X and the port Z are narrowed, and the port is switched to the position (e) when the aperture gradually increases. Conversely, the position where the acceleration increase becomes the normal increase (e)
During the operation of switching from the position (g) to the position (g), the position (f ₁ )
, The ports Y and Z conduct, the throttle gradually becomes gentle between ports X and Z, the flow rate gradually increases from 0, and after the port is switched to the position (f ₂ ) where the three ports X, Y and Z communicate. ,position
(g).

The mode of the lifting operation of the self-weight load by the hydraulic circuit shown in FIG. 5 will be described below. Differential control valve 10
Set B to position (g), and raise / lower control valve 9 to neutral position
When switching from the position (b) to the position (c), the hydraulic circuit related to the hydraulic cylinder 16A becomes a double-acting circuit, and the pressure oil from the pressure source flows into the head side, the oil on the rod side flows out into the tank and the piston The rod extends. If the lift control valve 9 is an electromagnetic proportional directional flow control valve, the amount of oil flowing into and out of the cylinder can be controlled by controlling the spool stroke, that is, the valve opening, with the current value. When the position is completely switched to the position (c), all the pressure oil from the pressure source flows into the head side, and the load is reduced to 50 kgf / cm ^2.
Increase with pressure.

Electromagnetic switching valve 51 for controlling differential control valve 10B
Is turned on, the oil in the pilot chamber flows into the pilot chamber, while the oil in the spring chamber is supplied to the check valve 53 with throttle.
Is slowly discharged through the throttle of the differential control valve 10B.
Switches continuously from position (g) → position (f ₂ ) → position (f ₁ ) → position (e) in 0.4 seconds as described above. In the state of the position (f ₂ ), the port Z communicates with the ports X and Y, but the pipe 104
Is 100 Kgf / cm ² , and the entire amount of oil from the rod side flows into the tank via the line 103 at a low pressure, for example, 5 Kgf / cm ² . In this case, since the check valve 11 is provided, pressure oil does not flow from the pipe 104 to the pipe 105. At the subsequent position (f ₁ ), the passage from the port Z to the port X is narrowed, and the pressure in the pipeline 102 increases. The pressure in the pipe 101 also increases in proportion to the increase in the pressure in the pipe 102. When the restriction of the passage from the port Z to the port X gradually decreases and the pressure in the pipe 102 rises to 100 Kgf / cm ² , the pressure in the pipe 101 at this time also increases to a load pressure of 50 Kgf / c.
100 kgf / cm ² , which is equivalent to the sum of m ² and 100 kgf / cm ² ÷ 2, which is the pressure of the oil chamber on the head side.
Is pushed open, and the pressure oil starts flowing into the line 104 from the line 105 (however, the spring force of the check valve 11 is ignored).

As the throttle from the port Z to the port X becomes smaller, the amount of oil flowing from the line 102 to the line 103 decreases, and conversely, the amount of oil flowing from the line 102 to the line 105 increases. Consequently, as a result, the rising speed of the piston rod of the hydraulic cylinder 16A increases. When the position is completely switched to the position (e), the entire amount of the return oil from the rod-side oil chamber is circulated to the head side, and the rising speed of the piston rod of the hydraulic cylinder 16A is doubled in the case of the double-acting circuit. The pressure becomes 100 kgf / cm ² ignoring the pressure loss of the circuit and operates as a so-called differential circuit. Conversely, the switching from the differential circuit to the double-acting circuit is performed by turning off the electromagnetic switching valve 51 and the differential control valve 10B.
The spool is pushed back by the return spring in the main valve, the oil in the pilot chamber is slowly discharged through the throttle of the check valve with throttle 52, the switching speed of the differential control valve 10B is controlled, and the port Z → The oil amount to the port Y gradually decreases, and the rising speed of the hydraulic cylinder 16A smoothly decreases. As described above, when switching between the rise at the normal speed and the rise at the double speed, the return oil from the rod side is smoothly switched between the flow to the tank and the circulation to the head side, and there is no shock. Smooth shifting is possible.

FIG. 6 is a hydraulic circuit diagram showing a main part of the load side control unit 15 according to another embodiment of the present invention.
In the hydraulic circuit according to the other embodiment, the differential logic valve 23B, the head side meter-out logic valve 54, the head side meter-in logic valve 55, the rod side meter-in logic valve 56, the rod side meter-out logic valve 57
5 poppet valves and three electromagnetic switching valves 24B, 5
8, 59, a counter balance relief valve 60, a shuttle valve 25B, and three check valves 61, 62, 63.
And A control valve device 29 composed of a differential logic valve 23B, an electromagnetic switching valve 24B for pilot operation, and a shuttle valve 25B, that is, a device having the same structure as the merge control valve device 6 shown in FIG. This is provided as a device having both the opening and closing function of the control valve 10B and the check function of the check valve 11 at the time of double speed increase. By controlling the pressure of the spring chamber of the differential logic valve 23B, the double speed of the hydraulic cylinder is controlled. The check function can be exercised only when ascending, and the rest can be closed.

On the other hand, the head side meter-out logic valve 5
4. The four poppet valves, the head-side meter-in logic valve 55, the rod-side meter-in logic valve 56, and the rod-side meter-out logic valve 57, are used to extend the piston rod of the hydraulic cylinder 16A. 55 and rod side meter-out logic valve 5
7, the head side meter-out logic valve 54 and the rod side meter-in logic valve 56 and the rod side meter-in logic valve 56 are closed. The valve 56 is opened and the head side meter-in logic valve 55 and the rod side meter-out logic valve 57 are closed, and the switching operation of the electromagnetic switching valves 58 and 59 is performed. Is possible. A control valve device having the same function as the lift control valve 9 is formed by a structure in which four logic valves 54 to 57 and two electromagnetic switching valves 58 and 59 are combined. In order to provide a flow control function in addition to the above, a structure having a notched throttle mechanism for the logic valve 54 and the logic valve 57 may be used. It goes without saying that the embodiment shown in FIG. 6 described above can fulfill substantially the same function as the embodiment shown in FIG. The embodiment shown in FIGS. 5 and 6 can also be used for hydraulic cylinders for purposes other than lifting and lowering.

[0040]

As described above in detail, according to the present invention, when the weight of the lifting device is lowered, the flow rate flowing out of the cylinder for lifting and lowering into the tank is reduced by the flow control valve. it can. In this case, since the hydraulic cylinder head-side oil chamber and the rod-side oil chamber are connected, the pressure becomes statically the same, and high-pressure oil flows from the volume decreasing side to the volume increasing side of the cylinder, resulting in cavitation. Does not happen.

Further, since the oil flowing out from the oil chamber on the volume decreasing side partially flows into the oil chamber on the volume increasing side, the flow rate flowing to the elevation control valve is reduced, so that the elevation control valve can be downsized. Also, the pump discharge oil is prevented from flowing into the lifting hydraulic cylinder by the control valve, and is maintained at a pressure higher than the pilot pressure of the lifting control valve. Regardless of the pressure source pilot pressure method, the switching of the direction and the control of the opening degree can be reliably performed. As described above, according to the present invention, ascending and descending can be performed at a speed higher than the speed corresponding to the pump flow rate, so that the cycle time of the entire elevating device can be gradually reduced and productivity can be improved with high safety.

Further , in the present invention , when the hydraulic cylinder is operated to increase the speed from a normal speed to a double speed, and vice versa, the pressure oil flowing from the pressure source is always stably supplied to the volume increasing oil chamber. Since the return oil from the oil chamber on the volume decreasing side can be smoothly switched between the flow to the tank and the circulation to the oil chamber on the volume increasing side, it is possible to shift smoothly without shock. .

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a vertical aluminum high-pressure casting machine according to one embodiment of the present invention.

FIG. 2 is a partial view of a hydraulic circuit diagram according to another embodiment of the present invention.

FIG. 3 is a partial view of a hydraulic circuit diagram according to another embodiment of the present invention.

FIG. 4 is a partial view of a hydraulic circuit diagram according to another embodiment of the present invention.

FIG. 5 is a partial view of a hydraulic circuit according to another embodiment of the present invention.

FIG. 6 is a partial view of a hydraulic circuit according to another embodiment of the present invention.

FIG. 7 is a schematic structural view of a vertical high-pressure casting machine.

FIG. 8 is a hydraulic circuit diagram for a prior art vertical aluminum high pressure caster.

[Explanation of symbols]

 1A, 1B ... Hydraulic pump 3 ... Hydraulic power source device 7 ... Hydraulic control unit 8 ... Check valve 9 ... Elevation control valve 10,10A, ... Regeneration control valve 10B ... Differential control valve 11 ... Check valve 12 ... Check valve 15 ... Load Side control unit 16A, 16B ... hydraulic cylinder.

Claims (4)

(57) [Claims] A hydraulic cylinder for raising and lowering a load of its own weight in a lifting device, a lifting and lowering control valve for maintaining a pilot pressure at a predetermined value and supplying hydraulic oil to the hydraulic cylinder to perform raising and lowering operations; A flow control valve for reducing the flow rate of hydraulic oil from the hydraulic cylinder to the tank line when the load of its own weight is lowered, and a head side oil chamber and a rod side oil chamber of the hydraulic cylinder on the load side of the lift control valve when the weight is lowered. A hydraulic circuit for operating a cylinder, comprising: a control valve; and a control valve for restricting a flow of pressurized oil from a hydraulic pump to a hydraulic cylinder when descending. 2. A hydraulic cylinder is connected to an elevating device so as to increase the volume of the rod-side oil chamber when the self-weight load decreases, and a hydraulic pump changes discharge pressure to pilot pressure of the elevating control valve when the self-weight load decreases. The hydraulic circuit for operating a cylinder according to claim 1, wherein the hydraulic circuit is operated so as to be kept relatively high, and the elevation control valve is formed as a self-pressure control valve. 3. The discharge pressure of a hydraulic pump is set to a value lower than a maximum set pressure of a relief valve provided in a hydraulic circuit during the lowering of the self-weight load, and is set to the maximum set pressure after the lowering is completed. 3. The hydraulic circuit for cylinder operation according to claim 2, wherein the setting is changed. A hydraulic double-acting circuit to 4. A connection switching the pressure source and tank to the hydraulic cylinders to be extended or reduced piston rod, connected containers product increased side oil chamber that put the hydraulic cylinder pressure source, And it has a differential circuit that allows only the flow of the pressure oil from the volume-decrease-side oil chamber to the volume-increase-side oil chamber, and a switching device that switches between the double-acting hydraulic circuit and the differential circuit. In the middle of switching between the hydraulic double-acting circuit and the differential circuit, after connecting the three pipelines of the volume decreasing oil chamber, the volume increasing oil chamber, and the tank, pressure oil from the volume decreasing oil chamber to the tank is connected. A switching control means for interrupting the flow of the cylinder while restricting the flow.