JPH0780618A - Hydraulic circuit for driving cylinder - Google Patents

Abstract

PURPOSE:To ensure the control reliability by eliminating the mechanical shock at the time of acceleration/deceleration control in the hydraulic circuit and to improve the productivity by realizing the high speed vertical movement in a hydraulic cylinder for vertical movement. CONSTITUTION:In the hydraulic circuit for driving the cylinder, the hydraulic cylinders 16A, 16B each executing the vertical movement by its dead wt. load in a vertical moving device, a vertical movement control valve 9 by which a pilot pressure is held at a prescribed value and vertical movement is actuated by supplying the pressure oil to the hydraulic cylinders 16A, 16B and a control valve 9 throttling the pressure oil flow rate from the hydraulic cylinders 16A, 16B to a tank line at the time of descending by the dead wt. load, are arranged. Further, control valves 10, 12 for connecting head side oil chambers and rod side oil chambers in the hydraulic cylinders 16A, 16B on the load side than the control valve 9 at the time of descending and a control valve 8 for limiting the flow of the pressure oil from hydraulic pumps 1A, 1B to the hydraulic cylinders 16A, 16B at the time of descending as well are arranged in this hydraulic circuit.

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 FIG. 7 shows a schematic structure of a vertical high pressure casting machine which is an example of this type of apparatus. A slide 41 having an upper mold attached thereto is guided by the four columns 42 and is moved up and down by two hydraulic cylinders 16A and 16B for moving up and down. The upper mold is lowered and pressed against a lower mold (not shown) fixed below, the half nuts 43 are engaged with the column 42, and the four mold clamping cylinders 44 are connected to the half nuts 43.
After a predetermined mold clamping force is obtained by contacting with the above and applying hydraulic pressure, the molten aluminum is injected into both molds by the injection cylinder 45 provided below. Hydraulic cylinder 16
Lifting of A and 16B is performed by the hydraulic circuit shown in FIG. At the time of ascent, the flow rate is controlled by the elevation control valve 9 which is an electromagnetic proportional directional flow control valve, the positions of the hydraulic cylinders 16A and 16B are measured by position sensors or limit switches, and acceleration, steady,
Deceleration control and stop position control are performed.

In addition to the above-mentioned method, the above-mentioned flow control method or speed control method is a flow control method using a variable pump,
There is also a flow rate control method of sequentially controlling the on-load of a plurality of pumps, or a method of using both an electromagnetic switching valve and a flow rate control valve as in the prior art disclosed in Japanese Patent Publication No. 3-35019. Further, in order to increase the ascending / descending speed, a method of joining the return oil from the cylinder to the sending side by using a regeneration circuit method is also implemented. In addition to the above flow rate control, in order to prevent the slide 41 and the upper die from self-propelled due to the self-weight load of the elevating cylinder, pressure control is performed using a counter balance valve 39, as shown in FIG. It is descending at a flow rate that matches the supply flow rate. The pilot pressure of the electromagnetic hydraulic switching valve can be either a method with a pump dedicated to pilot pressure or a method with self-pressure as the pilot pressure.However, the self-pressure method requires a dedicated pilot pump and pilot piping. It is advantageous in terms of equipment cost.

[0004]

By the way, in the case of this type of lifting device, the lowering speed of the lifting cylinder cannot be made higher than a value commensurate with the pump flow rate. Therefore, as a countermeasure, if the counterbalance valve 38 is omitted and the oil on the head side of the lifting cylinder is caused to flow out by its own weight and the speed is equal to or 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, the upper die and the lower die come into contact with each other at the lower limit, the lifting cylinder stops, it takes time for the pressure on the rod side to rise, and the cylinder may be filled with bubbles. The pump pressure is reduced due to insufficient supply flow rate to the rod side, which is lower than the required pilot pressure of the electromagnetic hydraulic switching valve, making it impossible to switch the valve.
Especially in the case of the solenoid proportional flow control valve, the pilot pressure is 30
Since a pressure of about Kg / cm ² is required, there are various problems such as a decrease in pump pressure is difficult for control.

On the other hand, in the hydraulic circuit shown in FIG.
When increasing the raising speed of the raising / lowering cylinder, the raising / lowering control valve 9 is switched to the raising side and the regeneration (differential) control valve 10 is switched from the operation position shown in the drawing, so that the pressure oil in the rod-side oil chamber is removed. Although the speed can be increased by returning to the oil chamber on the head side through the pipe 104, the regeneration control valve 10
Means that the three ports are conducting during this switching,
Some have three ports blocked,
In the former conduction type, the oil flowing to the head side in the pipe line 101 flows from the pipe line 104 through the regeneration control valve 10 to the pipe line 103 and is connected to the tank, and the speed of the lifting cylinder is momentarily stopped or decelerated. Cause a shock. In the latter block type, the oil flowing in the line 102 → regeneration control valve 10 → line 103 → elevation control valve 9 → tank is momentarily interrupted during switching, and the movement of the elevator cylinder stops. And cause a big shock. Such a shock similarly occurs when switching to the deceleration direction. It should be noted that such a shock is not limited to the hydraulic cylinder for lifting and lowering, but generally occurs with the expansion and contraction operation of the hydraulic cylinder.

The present invention has been made in order to solve the above problems, and an object of the present invention is to eliminate the mechanical shock at the time of increasing / decreasing speed control in a hydraulic circuit for cylinder operation, and It is intended to ensure control reliability by preventing cavitation in the lifting hydraulic cylinder and to improve productivity by realizing high-speed lifting.

[0007]

The present invention has the following constitution in order to achieve the above object. That is, the present invention relates to a hydraulic cylinder that performs an elevating operation of a self-weight load in an elevating device, an elevating control valve that holds a pilot pressure at a predetermined value, and supplies pressurized oil to the hydraulic cylinder to perform an elevating / lowering operation. A flow rate control valve that throttles the flow rate of pressure oil from the hydraulic cylinder to the tank line when the self-weight is lowered, and a head side oil chamber and a rod side oil chamber of the hydraulic cylinder are connected on the load side of the lifting control valve when the load is also lowered. And a control valve for restricting the flow of pressure oil from the hydraulic pump to the hydraulic cylinder when the hydraulic cylinder descends, which is also a hydraulic circuit for cylinder operation.

According to the present invention, the hydraulic cylinder is connected to the lifting device so as to increase the volume of the rod-side oil chamber when the own weight load is lowered, and the hydraulic pump controls the discharge pressure of the lifting control valve when the own weight load is lowered. A hydraulic circuit for operating a cylinder, characterized in that it is driven so as to be kept higher than a pilot pressure, and a lift 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 during the lowering of the self-weight load, and the maximum set pressure is reached after the lowering is completed. It is a hydraulic circuit for operating a cylinder characterized by being set to a value.

The present invention also relates to a hydraulic double-acting circuit for switching and connecting a pressure source and a tank to a hydraulic cylinder to extend and contract a piston rod, and to increase and decrease the self-weight load by increasing the self-weight of the hydraulic cylinder. A differential circuit that connects the volume-increasing oil chamber that receives a load to a pressure source and allows only the flow of pressure oil from the volume-decreasing oil chamber to the volume-increasing oil chamber, and a hydraulic double-action circuit and a differential circuit. And a switching device for switching between the circuit and the switching device. During the switching between the hydraulic double-action circuit and the differential circuit, there are three system pipelines of a volume decreasing side oil chamber, a volume increasing side oil chamber and a tank. After the connection, the cylinder operating hydraulic circuit is characterized in that switching control means is provided for interrupting the flow of the pressure oil from the volume reducing side oil chamber to the tank while throttling the flow.

[0010]

According to the present invention, when the self-weight of the lifting device is lowered, the flow rate of the oil flowing out from the volume reducing oil chamber of the hydraulic cylinder to the tank is throttled by the flow control valve, so that the descending speed can be controlled. In that case, since the volume decreasing side oil chamber and the volume increasing side oil chamber are connected, the static pressure is the same and high-pressure oil flows into the volume increasing side oil chamber from the volume decreasing side oil chamber. , Cavitation does not occur. Also,
The flow of pump discharge oil into the oil chamber on the volume increasing side is restricted by the control valve, and is maintained at a pressure higher than the pilot pressure of the lift control valve.Therefore, the lift control valve ensures direction switching and opening control. You can do it. As a result, it is possible to descend at a speed higher than the speed commensurate with 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 during the lowering of the self-weight load, and after the lowering is completed. Then, by changing the setting to the maximum value of the set pressure, the mold clamping force by the hydraulic cylinder after the processing 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 volume decreasing side oil chamber of the hydraulic cylinder, the volume increasing side oil chamber and the three-system pipeline of the tank, from the volume decreasing side oil chamber By shutting off the flow of pressure oil to the tank while throttled, the pressure oil flowing from the pressure source always flows stably into the volume increasing side oil chamber, while the return oil from the volume decreasing side oil chamber is The flow to the tank and the circulation to the oil chamber on the volume increasing side can be smoothly switched, and a smooth gear shift without 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 casting machine according to an embodiment of the present invention. The illustrated hydraulic circuit includes two variable displacement hydraulic pumps 1A,
1B, an oil tank 2, a filter 21, and a hydraulic source device 3 including a cooler 22, electromagnetic pilot type unload relief valves 4A and 4B, a check valve 5, and a confluence control valve device 6. Hydraulic control unit 7, check valve 8, lifting control valve 9 realized by an electromagnetic proportional directional flow control valve, regeneration control valve 10, check valve 11, check valve 12, relief valve 13 realized by an electromagnetic switching valve, The load side control unit 15 including the pilot check valve 14 and the lifting operation of the upper die, which is its own weight, are performed 2
And hydraulic cylinders 16A and 16B connected in parallel.

The hydraulic pump 1A has a maximum discharge capacity of 80, for example.
It is used as a pressure source of 210 K (Kgf / cm ² ) system at l / min, and the hydraulic pump 1B has a maximum discharge capacity of 130 l / min.
And used as a pressure source for the 150 K (Kgf / cm ² ) system.
The hydraulic control unit 7 is configured as a control device for controlling the pressure, the flow rate, and the confluence of both systems of two systems having a circuit pressure of 150K (B) system and 210K (A) system. The 150K (B) system mainly forms an injection circuit and a mold clamp circuit, and stores pressure oil in an accumulator (not shown) to be 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, and knocking out the product. In the direct pressure type and the half nut type mold clamping, the capacity of the lifting cylinder and the mold clamping cylinder becomes large.
It is not possible to deal with only A, and the flow rate is increased by merging from the hydraulic pump 1B of the 150K system to adapt to the load.

In the hydraulic control unit 3, the unload relief valve 4A pilot-operated by the electromagnetic switching valves 17 and 18 keeps the pipeline A in a pressure state of 210 Kgf / cm ^{2 in} a steady state, and in relief in a standby state. Valve 20
The unload relief valve 4B, which is operated by the electromagnetic switching valve 19 as a pilot, operates to maintain the pipe line A in a pressure state of 35 Kgf / cm ² by
Operates to hold line B at a pressure of 0 Kgf / cm ² . On the other hand, the check valve 5 is provided in the middle of the 150K system feed hydraulic line so as to prevent backflow to the pressure source side. The location of the check valve 5 is to join the discharge side of the hydraulic pump 1B. It is preferable to use the feed pipe line B _{2 which} is as close as possible to the connection point with the control valve device 6 (connection point connection point).

The merging control valve device 6 is provided with a pilot operated poppet valve 23, an electromagnetic switching valve 24 for pilot operation, and a shuttle valve 25 in this embodiment. The port P1 on the inlet side of the poppet valve 23 has the hydraulic pump 1
A pipe line B connected to the discharge side of B is connected to a pipe line A whose outlet port P2 is 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 side port of the shuttle valve 25, and the other switching. Port B is blocked. The other inflow side port of the shuttle valve 25 is connected to the port P2 of the poppet valve 23, and the common outflow side port is connected to the spring chamber that is the pilot operating portion 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 end of the pipe A through a check valve 8 in series. Further, one of the switching ports is connected to both hydraulic cylinders 16 via the pilot check valve 14 in series.
A and 16B are connected to the oil chambers on the head side, and the other switching port is connected via the regeneration control valve 10 to both hydraulic cylinders 16A,
It is connected to the rod side oil chamber of 16B. Check valve 8
The pressure oil is interposed so as to allow the pressure oil to flow from the hydraulic pump 1A toward the lift control valve 9.

As described above, one port of the regeneration control valve 10 on the pressure source side is connected to the other switching port of the elevation control valve 9, and the other port is also elevated 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 also on one side of the lift control valve 9 via the check valve 12 in series. Connected to the switching port. It should be noted that the check valve 11 is configured such that pressure oil is applied to both hydraulic cylinders 1.
The check valve 12 is provided so as to allow the fluid to flow from the rod side oil chambers of 6A and 16B toward the head side oil chamber of the lifting hydraulic cylinders 16A and 16B via the regeneration control valve 10 side. The oil is provided so as to allow the oil to flow from the head side of both the 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 lift control valve 9, the regeneration control valve 10, and the pilot check valve 14 pilot-operated by the electromagnetic switching valve 27 is provided so as to operate using the self-pressure, which is the pressure in the pipeline A, as the pilot pressure. However, the pilot check valve 14 is provided in a pipe line that connects the lift control valve 9 and the head-side oil chambers of both hydraulic cylinders 16A and 16B. Further, 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.

A mode of raising and lowering the self-weighted load by the hydraulic circuit shown in FIG. 1 will be described below. Here, the area ratio between the oil chamber on the cylinder head side and the oil chamber on the cylinder rod side of both hydraulic cylinders 16A, 16B is 2: 1 and the load pressure is 50 kgf /.
cm ² (100 Kgf / cm ² when regenerating). (1) When lifting / lowering is stopped: The hydraulic pump 1A has a solenoid switching valve 18
Is turned on, the solenoid operated directional control valve 17 is turned off, and 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 operated by the unload relief valve 4B.
Will be in relief. In the merge control valve device 6, the electromagnetic switching valve 24 is off, and the pipe line A has a low pressure of 35 Kgf / c.
Stand-by condition at m ² , pipes B _{1 and} B ₂ at 150 K
It is gf / cm ² .

(2) At the time of raising: The raising / lowering control valve 9 is switched to the (c) position, and the electromagnetic switching valve 17 is turned on to activate the unload relief valve 4A. When the position (b) → (c) is switched by the lift control valve 9, current control is performed so that the lift cylinder composed of both hydraulic cylinders 16A and 16B moves up in a predetermined speed pattern. The setting pressure of the unload relief valve 4A is 35 Kgf / cm ² to 21
0 Kgf / cm ² to boost rises from the pipe path A and the load-side control unit 15 a hydraulic cylinder 16A, in 50 Kgf / cm ² of pressure the pressure of the hydraulic circuit until 16B is commensurate with the load, the pilot check valve Oil flows through the head-side oil chamber via 14, the oil in the rod-side oil chamber returns to the tank, the hydraulic cylinders 16A and 16B start moving, and the speed is adjusted to the discharge amount of the hydraulic pump 1A. Here, the regeneration control valve 10
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 doubles. The discharge pressure of the hydraulic pump 1A is calculated from 50 Kgf / cm ² to 1 by simple calculation ignoring the pressure loss in each part.
It rises to 00 Kgf / cm ² . In this case, the existence 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 passed, the electromagnetic switching valve 24 is excited and switched. The oil in the spring chamber of the poppet valve 23 is
Flow through the shuttle valve 25 to the tank, poppet valve 2
3 is stroked and opened. The opening of the poppet valve 23 suddenly increases, and the oil discharged from the hydraulic pump 1B joins the hydraulic cylinders 16A and 16B and rises at the highest speed. By the way, when the poppet valve 23 is opened, the pressure oil in the pipe line B ₁ merges with the pipe line A side, but the pipe line B ₂ side remains at a high pressure due to the depressing action of the check valve 5. Therefore, the high-pressure portion that is the merging portion is only the short portion of the pipeline B ₁ , and the volume of the oil in the merging portion is small, and the shock at the time of switching is small. Therefore, the switching time can be shortened, and naturally the cycle is correspondingly reduced. Time will also be shortened. Note that when decelerating and 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) decreases, and the unload relief valve 4
When A is unloaded, the speed further decreases and then stops, and the lifting control valve 9 on the load side returns to the neutral position from (c) to (b), and is held stopped. In the deceleration control, current control of the lift control valve 9 is performed so that a predetermined speed pattern is obtained. Flow control is
The raising / lowering control valve 9 may be used, the discharge rate of the variable pump may be controlled, or the combination order of the pumps may be controlled as a combination of a plurality of pumps. Further, the order of the reproduction circuit control and the merge control may be reversed.

(3) When descending: Pipe line A has a low pressure of 35 Kgf / cm ²
Is in standby mode. Regeneration control valve 10 (e)
The position is switched to (f) and the solenoid switching valve 27 of the pilot check valve 14 is turned on to turn the lifting control valve 9
Switch the position 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 is increased from 50 Kgf / cm ² to 100 Kgf / cm ² , while the rod side pressure is increased from 0 Kgf / cm ² to 100 Kgf / cm ² , and the lift control valve When 10 reaches the position (a), the pressure oil in the head side oil chamber flows through the valve 10 to the tank line. The oil flows from the head side oil chamber to the rod side oil chamber through the check valve 12 and the regeneration control valve 10 by the amount of 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 position (a),
The rod-side oil chambers of the hydraulic cylinders 16A and 16B and the hydraulic pump 1A are connected via a check valve 8. The rod-side oil chamber is 100 Kgf / cm ² , and the pump discharge oil is 35 Kgf.
/ cm remains ^2, therefore, the oil in the rod side oil chamber is not flow back to the pump side, the pump discharge oil does not flow in the rod side oil chamber. In this case, the pump pressure is 35 Kgf / cm ² ,
The circuit is an energy-saving circuit because it can be sufficiently used as the pilot pressure of the lift control valve 9 and is relieved at a low pressure. In the case of a variable pump, energy can be saved more by reducing the pump displacement and the discharge amount. In addition, 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.
When the pressure is set to / cm ² , the pump discharge oil flows into the oil chamber on the cylinder rod side via the check valve 8, and the lowering speed of the cylinder naturally increases.

As an alternative to the throttling of the lift control valve 9, a slow return check valve for throttling the oil flowing out from the oil chamber on the head side may be provided at a position of the pipe I in FIG. 1 and used. Further, as the lift 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 performed by controlling the switching speed of the switching valve by restricting the pilot line of the electromagnetic hydraulic switching valve. Anything is fine. The descending 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 opening of the control throttle determines the maximum value of the descending speed.

(4) At the end of lowering: When the upper mold and the lower mold are brought into contact with each other at a low speed by the current control of the lifting control valve 9 so as not to generate an impact, the lowering of the hydraulic cylinders 16A, 16B is stopped. , The head pressure drops. At this time, relief valve 4A
Switching to 210 Kgf / cm ² will increase the pump pressure and
When the pressure exceeds 00 Kgf / cm ² , the check valve 8 is pushed up and the pressure oil flows into the oil chamber on the rod side, the pressure is increased to 210 Kgf / cm ² , and the upper mold and the lower mold are tightened. Next, referring to FIG. 5, the operation of the mold clamping cylinders 44A and 44B is started. At this point, the pre-clamping by the hydraulic cylinders 16A and 16B has already been performed, and the next injection process can be started at the same time. Although the pump pressure temporarily drops when moving the mold clamping cylinders 44A and 44B, the pressure in the rod side oil chamber of the hydraulic cylinders 16A and 16B is maintained by the check valve 8 (although there is a slight pressure drop due to valve leakage). .

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 while the hydraulic cylinders 16A and 16B are being lowered, and the lowering is completed. Between the time immediately before the end of the descent and the time when the descent is completed, the setting pressure is changed to the maximum value, while the check valve 12 connects the head-side oil chamber and the rod-side oil chamber during the descent, and the rod-side oil chamber moves to the head-side oil chamber. By providing the backflow to the chamber, it is possible to add the mold clamping force by the hydraulic cylinders 16A and 16B immediately after stopping the descending. Further, by providing the check valve 8, the pump pressure is controlled by the hydraulic cylinders 16A, 16A.
Even if the load pressure is lower than B, no reverse flow occurs, and the energy saving effect is high due to the decrease in pump pressure.

The embodiment described above is an example of a control method in which the self pressure is used as the pilot pressure of the lift control valve, but the hydraulic pump 1 is used as the pilot pressure source.
Even in the case of an external pressure source using a hydraulic pump separate from A, the lowering control of the lifting cylinder can be performed in the same manner as in the embodiment, and the same action and effect can be exhibited. It goes without saying that such modifications are also included in the scope of the present invention.

Next, FIGS. 2, 3 and 4 are hydraulic circuit diagrams showing essential parts according to other embodiments of the present invention. In each of those embodiments, the same reference numerals are given to the corresponding members that are similar to the embodiment shown in FIG. First of all,
In the example shown in, the control valve device 29 including the poppet valve 23A, the electromagnetic switching valve 24A for pilot operation, and the shuttle valve 25A, that is, the device having the same structure as the merging control valve device 6 is used as the check valve 12. The point that they are provided instead is being noticed. 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 descends, and the rest can be closed, which is substantially the same as the embodiment shown in FIG. Can perform a function.

Points to be noted in the example shown in FIG. 3 are 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
That is, the regeneration control valve 10 is replaced with a control valve device 33 including 4, 35 and a throttle 36. With the electromagnetic switching valve 24B in the neutral position (m) shown, the poppet valve 23B closed, the electromagnetic switching valve 24C in the OFF position shown, and the poppet valve 23C open, the lift control valve 9 is moved to the position (c). )
The hydraulic cylinders 16A, 16
B moves up.

By setting the electromagnetic switching valve 24B to the position (n), the poppet valve 23B becomes a check valve which allows the flow from the rod side to the head side.
The same function as 1 is exhibited, 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 lift control valve 9
The poppet valve 23B is switched to the check valve 12 by switching to (a), turning the electromagnetic switching valve 24C to the off position to open the poppet valve 23C, and switching the electromagnetic switching valve 24B to the position (l) to open the poppet valve 23B. Exerts the same function as. Therefore, it is clear that the example of FIG. 3 performs the same function as the embodiment shown in FIG.

Note that in the example shown in FIG.
The regeneration control valve 10 and the check valve 1 in the embodiment shown in FIG.
1 and 12 are omitted, and pilot check valve 3 is used instead.
7 is connected across the head side pipe line and the rod side pipe line,
This is a point that the pilot check valve 14 and the pilot check valve 37 can be alternately switched to the check operation and the opening by the electromagnetic switching valve 38 for pilot operation. In this example, when rising, the pilot check valve 37 is opened by the pilot pressure, and the raising / lowering control valve 9 is set to the position (C ₁ ) so that it can function as a regeneration circuit. When descending, the pilot check valve 37 acts as the head-side → rod-side check valve 12, and therefore the function when descending is the same as that of the embodiment shown in FIG.

Next, FIG. 5 is a hydraulic circuit diagram showing a load side control unit 15 of a main part according to another embodiment of the present invention. In the other embodiments, the members similar to the embodiment shown in FIG. 1 and corresponding to each other are designated by the same reference numerals. 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 by the piston rod, and the ascending volume increasing side oil on the side receiving the self-weight load. Ratio of the pressure receiving area A _H of the head side oil chamber which is a chamber, the pressure receiving area A _R of the rod side oil chamber which is a rising volume decreasing side oil chamber, and the cross-sectional area A _D of the piston rod is 2: 1: 1. It is assumed that the structure of 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. This differential control valve 10B uses a 3-port indirect operation pilot type switching valve, and uses an electromagnetic switching valve 51,
And check valves 52 and 53 with throttles. Of the three ports X, Y, Z, the port X is connected to the load side switching port of the lift control valve 9 via the pipe 103, and the port Y is connected to the pipe 1
It is connected to the forward flow side port of the check valve 11 via 05,
Port Z for switching to each of these ports X and Y for conduction
Is connected to the rod-side oil chamber via a pipe line 102.

The differential control valve 10B is switched to the position (g) when the hydraulic cylinder 16A is operated at a normal ascending / descending speed so that the port X and the port Z are electrically connected and the port Y is connected.
Will block. On the other hand, when accelerating and ascending operation, the position is switched to the position (e) so that the ports Y and Z are brought into conduction and the port X is blocked. In this case, during the operation of switching from the position (g) to the position (e) for, for example, 0.4 seconds, the position (f ₂ ) where the three ports X, Y and Z communicate with each other is changed to the position (f ₁ ). The ports Y and Z are sequentially switched to each other, the ports X and Z are throttled while the ports Y and Z are electrically connected, and the port is switched to the position (e) when the aperture is gradually increased. On the contrary, the position (e)
To the position (g) during the operation, the position (f ₁ )
After that, the ports Y and Z become conductive, the throttle between ports X and Z gradually becomes gentle, and the flow rate gradually increases from 0, and after changing to the position (f ₂ ) where the three ports X, Y, and Z communicate with each other. ,position
It will switch to (g).

The mode of raising and lowering the own load by the hydraulic circuit shown in FIG. 5 will be described below. Differential control valve 10
Set B to the position (g) and set the lift control valve 9 to the neutral position.
When switching from (b) to position (c), the hydraulic circuit related to the hydraulic cylinder 16A becomes a double-acting circuit, 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 elevation control valve 9 is an electromagnetic proportional directional flow control valve, the amount of oil flowing into or out of the cylinder can be controlled by controlling the spool stroke, that is, the valve opening, by the current value. When completely switched to position (c), all the pressure oil from the pressure source flows into the head side, and the load is 50 Kgf / cm ²
Increase with pressure.

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

When the throttle from the port Z to the port X is further reduced, the amount of oil flowing from the pipe 102 to the pipe 103 is decreased, and conversely, the amount of oil flowing from the pipe 102 to the pipe 105 is increased. As a result, the rising speed of the piston rod of the hydraulic cylinder 16A increases. When 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 piston rod of the hydraulic cylinder 16A rises twice as fast as in the double-action circuit. When the pressure loss of the circuit is ignored, the pressure becomes 100 Kgf / cm ^2, and it operates as a so-called differential circuit. On the contrary, when switching from the differential circuit to the double-action circuit, the differential control valve 10B can be operated by turning off the electromagnetic switching valve 51.
The spool is pushed back by the return spring in the main valve, the oil in the pilot chamber is gently 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 amount of oil to the port Y gradually decreases, and the rising speed of the hydraulic cylinder 16A smoothly decelerates. In this way, when switching between the increase at the normal speed and the increase 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 the load side control unit 15 of the main part 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, and the rod-side meter-out logic valve 57.
5 poppet valves and 3 electromagnetic switching valves 24B, 5
8, 59, a counterbalance relief valve 60, a shuttle valve 25B, and three check valves 61, 62, 63.
With. A control valve device 29 including 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. It is provided as a device having both the opening / closing function of the control valve 10B and the check function when the speed of the check valve 11 is increased, and the speed of the hydraulic cylinder is doubled by controlling the pressure of the spring chamber of the differential logic valve 23B. The check function can be exerted only when rising, and the others can be closed.

On the other hand, head side meter-out logic valve 5
4, 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, the four poppet valves are used to extend the piston rod of the hydraulic cylinder 16A. 55 and rod side meter-out logic valve 5
7 and the head-side meter-out logic valve 54 and the rod-side meter-in logic valve 56 are closed, and when the piston rod is reduced, the head-side meter-out logic valve 54 and the rod-side meter-in logic valve 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 by. A control valve device having the same function as the lift control valve 9 is formed by a structure in which the four logic valves 54 to 57 and the two electromagnetic switching valves 58 and 59 are combined. In addition to the above, in order to have a flow rate control function, it is sufficient to use the logic valve 54 and the logic valve 57 having a structure having a throttle mechanism with a notch. It goes without saying that the embodiment shown in FIG. 6 described above can perform substantially the same function as the embodiment shown in FIG. The embodiments shown in FIGS. 5 and 6 are also 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 from the lifting cylinder side to the tank is throttled by the flow control valve, so that the descending speed is controlled. it can. In that case, since the oil chamber on the hydraulic cylinder head side and the oil chamber on the rod side are connected, the pressure is statically the same, and high pressure oil flows from the volume decreasing side to the volume increasing side in the cylinder, resulting in cavitation. Does not happen.

Further, since the oil flowing out from the volume decreasing side oil chamber partially flows into the volume increasing side oil chamber, the flow rate flowing to the elevation control valve is reduced, and as a result, the elevation control valve can be downsized. In addition, the pump discharge oil is kept at a pressure higher than the pilot pressure of the lift control valve by restricting the inflow to the lifting hydraulic cylinder side by the control valve. Regardless of the pressure source pilot pressure method, it is possible to reliably switch the direction and control the opening degree. As described above, according to the present invention, ascending / descending can be performed at a speed higher than the speed commensurate with the pump flow rate, the cycle time of the entire lifting device can be gradually reduced, and productivity can be improved with high safety.

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

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a vertical aluminum high pressure casting machine according to an 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 diagram of a vertical high-pressure casting machine.

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

[Explanation of symbols]

 1A, 1B ... Hydraulic pump 3 ... Hydraulic source device 7 ... Hydraulic control unit 8 ... Check valve 9 ... Lift 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.

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[Procedure amendment]

[Submission date] September 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[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 It has a differential circuit that is connected and allows only the flow of pressure oil from the volume decreasing side oil chamber to the volume increasing side oil chamber, and a switching device that switches between the hydraulic double-action circuit and the differential circuit. To the switching device, during the switching between the hydraulic double-action circuit and the differential circuit, after connecting the three lines of the volume decreasing side oil chamber, the volume increasing side oil chamber and the tank, the volume decreasing side oil chamber to the tank Is a hydraulic circuit for operating a cylinder, which is provided with a switching control means for interrupting the flow of the pressure oil while throttled.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

Further , according to the present invention , when the hydraulic cylinder is operated to increase the speed from the normal speed to the double speed or vice versa, the pressure oil flowing from the pressure source is always stabilized in the volume increasing side oil chamber. It is possible to smoothly switch the flow of the return oil from the oil chamber of the volume decreasing side to the tank and the circulation of the oil to the oil chamber of the volume increasing side, so that it is possible to smoothly shift without shock. .

Claims (4)

[Claims] 1. A hydraulic cylinder for raising and lowering its own load in a lifting device, a lifting control valve for holding a pilot pressure at a predetermined value and supplying pressure oil to the hydraulic cylinder to move up and down, A flow rate control valve that throttles the flow rate of pressure oil from the hydraulic cylinder to the tank line when the self-weight is lowered, and a head-side oil chamber and a rod-side oil chamber of the hydraulic cylinder are connected on the load side of the lifting control valve when the descent is also performed. A hydraulic circuit for operating a cylinder, comprising: a control valve; and a control valve which restricts a flow of pressure oil from a hydraulic pump to a hydraulic cylinder when the hydraulic valve descends. 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-load is lowered, and a hydraulic pump uses the discharge pressure as the pilot pressure of the elevating control valve when the self-load is lowered. 2. The cylinder operating hydraulic circuit according to claim 1, wherein the hydraulic control circuit is driven so as to be held relatively high, and the lift control valve is formed as a self-pressure control valve. 3. The discharge pressure of the hydraulic pump is set to a value lower than the maximum set pressure of a relief valve provided in the hydraulic circuit during the lowering of the self-weight load, and reaches the maximum set pressure after completion of the lowering. The hydraulic circuit for cylinder operation according to claim 2, wherein the setting is changed. 4. A hydraulic double-acting circuit for switching and connecting a pressure source and a tank to a hydraulic cylinder and extending / reducing a piston rod, and receiving the self-weight load of the hydraulic cylinder when accelerating / raising the self-weight load. A differential circuit that connects the volume increasing side oil chamber to the pressure source and allows only the flow of pressure oil from the volume decreasing side oil chamber to the volume increasing side oil chamber, and a hydraulic double-action circuit and a differential circuit And a switching device for switching, which is connected to the three lines of the volume decreasing-side oil chamber, the volume increasing-side oil chamber, and the tank during the switching between the hydraulic double-action circuit and the differential circuit. A hydraulic circuit for operating a cylinder, characterized in that switching control means is provided for shutting off the flow of the pressure oil from the oil chamber of the volume reducing side to the tank while throttling.