JPH09296802A - Raising and lowering hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve energy saving and shortening of a cycle time in the operation by facilitating speed control as in the case with a normal hydraulic circuit through a process of preventing high pressure from being applied to the hydraulic circuit at the time of lowering of mass. SOLUTION: In a hydraulic circuit provided with a hydraulic actuator 1, a hydraulic control valve 2, and a check valve 5, the hydraulic control valve 2 has four control positions of the neutral control position (b) in which inflow of fluid from a pressure source to the hydraulic actuator and outflow of fluid from the hydraulic actuator 1 to a tank at elevation stopping time are stopped, a raising control position (c) in which inflow and outflow are controlled in raising, the self-weight lowering control position (a1) in which inflow of fluid from the pressure source to the hydraulic actuator in self-weight lowering is stopped, and outflow of fluid from the hydraulic actuator is controlled, and the power lowering control position (a2) in which outflow and inflow in power lowering are controlled. The check valve 5 is opened by back pressure of a tank line in self-weight lowering, guides inflow fluid to the hydraulic actuator from the tank line, and stops the flow of fluid in power lowering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elevating hydraulic circuit such as a hydraulic circuit used in an elevating device for elevating a heavy object such as a mold opening / closing device such as a vertical press machine or die casting machine.

[0002]

2. Description of the Related Art In a hydraulic circuit used for a device for lifting and lowering a heavy object such as a mold opening / closing device of a vertical press machine, a hydraulic circuit having a structure shown in FIG. 8 has been widely used. ing. In this conventional example, when the mold W is raised in FIG. 8, the electromagnetic proportional direction / flow rate control valve (hereinafter, abbreviated as proportional valve) 17 is switched from the neutral control position (b) to the right position (a) and the pressure from the pressure source is changed. The oil flows from the P port of the proportional valve 17 to the A port to flow into the head side chamber of the cylinder 16, and the pressure oil discharged from the rod side chamber of the cylinder 16 flows from the B port of the proportional valve 17 to the T port to cause the tank. It is designed to be leaked to.

On the contrary, when the mold W is lowered, the solenoid valve 21 is energized to open the pilot check valve 20 and the proportional valve 17 is switched to the left position c so that the pressure oil from the pressure source is fed to the proportional valve 1.
7 flows from the P port to the B port to flow into the rod side chamber of the cylinder 16, and the pressure oil from the head side chamber of the cylinder 16 flows from the A port of the proportional valve 17 to the T port to flow out to the tank. Yes, proportional valve 17
It is possible to control the flow rate of the valve by controlling the current to the control valve, and to control the maximum speed of the cylinder 16 and the acceleration / deceleration. Note that the head and rod of the cylinder 16 are the same in the opposite relationship, and a hydraulic circuit configured by a combination of an electromagnetic switching valve, a throttle valve, and a check valve instead of the proportional valve is also common.

In the above-mentioned conventional example, when the mold is lowered, it is possible to lower the mold by its own weight, but in general, since the flow rate from the pressure source is made to flow into the rod side chamber of the cylinder 16, (1) A pressure source flow rate is required when descending, which consumes extra energy, and (2) In the case of a device that drives multiple lifting devices connected in parallel by the same pressure source, the multiple lifting When it is necessary to drive the device at the same time during the cycle time, the flow rate of the pressure source is insufficient, the speed decreases, or it becomes necessary to wait for the driving of one side, and the cycle time becomes longer. This is especially remarkable in the case of a tire vulcanizing press. (3) In the case of a device in which another device is connected with the same pressure source, when simultaneous operation is required, the same problem as in the case of the above (2) occurs.

[0005]

In order to solve the above problems, the present applicant has previously proposed the prior art disclosed in Japanese Patent Application Laid-Open No. 7-80618 as shown in FIG. . With reference to FIG. 9, a hydraulic circuit for operating a cylinder according to this prior art includes a hydraulic control unit (not shown) including a hydraulic power source device including a hydraulic pump and an oil tank as element members, and a check valve 26. , Solenoid proportional valve 1
7, electromagnetic switching valve 18, check valve 22, relief valve 1
9, a pilot check valve 20 pilot-operated by the electromagnetic switching valve 21, a poppet valve 23A, a load-side control unit including a control valve device 29 including an electromagnetic switching valve 24A for pilot operation and a shuttle valve 25A. , Two hydraulic cylinders 16A, 1 connected in parallel for performing lifting operation of the upper die of a high-pressure casting machine which is a self-load
6B, the solenoid proportional valve 17 is a control valve for raising, lowering, and stopping the hydraulic cylinders 16A, 16B, and the electromagnetic switching valve 18 is a control valve for forming a regeneration circuit when the cylinders are raised. Valve, and control valve device 29
Is a valve device that controls the pressure of the spring chamber of the poppet valve 23A so that the check function is exerted only when the hydraulic cylinder descends, and the rest are closed.

An outline of the mode of the cylinder operating hydraulic circuit when the cylinder is lowered will be described. The electromagnetic switching valve 21 is excited to open the pilot check valve 20.
When the electromagnetic switching valve 24A is excited, the poppet valve 23A becomes a check valve that allows the flow of pressure oil from the cylinder head side to the rod side. When the solenoid proportional valve 17 is switched to the left position among the three control positions in the figure, a regeneration circuit is formed and the descent is performed. That is, part of the oil on the head side is the solenoid proportional valve 17
Through to the tank, and the rest flows into the rod side through the poppet valve 23A. On the other hand, the oil of the pressure source will not flow into the rod side if the pressure source pressure is lower than the rod side pressure,
If it is higher, it will flow into the rod side. When the electromagnetic switching valve 18 is further switched at the time of lowering, oil does not flow from the pressure source to the rod side regardless of the pressure source pressure and the rod side pressure. Due to this, it is possible to solve the above-mentioned problems in the prior art by this hydraulic circuit.

By the way, in the above-mentioned prior art, it is clear that (1) the hydraulic circuit at the time of lowering the cylinder is as shown in FIG. 10 if only the portion exhibiting the dynamic characteristics of the system is abbreviated. Since this abbreviated circuit is, of course, a reproducing circuit, the holding pressure of the cylinder due to its own weight becomes high, and as a result, the spring constant of the system becomes small. Although there is a throttle mechanism in the oil passage from the head side to the tank, there is no throttle in the oil passage on the rod side, and damping of the system is small. From this, it is expected that the hydraulic system will be a system that easily vibrates, and if force is applied during acceleration or deceleration, vibration will occur and speed control will become difficult to perform. (2) With the rod diameter symbol “B” of JISB8354 of a commonly used cylinder, the area ratio between the head side and the rod side is 3: 2. Is three times as large as in the case of a double-acting circuit, so that it becomes necessary to use a high pressure cylinder.

The present invention has been made in view of the problems of the prior art as described above, and therefore the object of the present invention is to provide a hydraulic circuit associated with the decrease of the mass. To provide a lifting hydraulic circuit that can prevent high pressure from being applied, facilitate speed control in the same manner as a normal hydraulic circuit, can save energy, and can shorten the cycle time during operation. Especially.

[0009]

The present invention has the following configuration to achieve the above object. That is, the present invention is a hydraulic circuit for elevating and lowering a mass in an elevating device such as a mold opening and closing device of a vertical press, which includes a hydraulic actuator, a hydraulic control valve, and a check valve. , A neutral control position that stops the fluid flow from the pressure source to the hydraulic actuator and the fluid flow from the hydraulic actuator to the tank when the elevator stops, and the fluid that flows from the pressure source to the hydraulic actuator when rising and the hydraulic actuator to the tank A rising control position that controls the fluid that flows out, a gravity lowering control position that stops the fluid from flowing from the pressure source to the hydraulic actuator when it descends due to its own weight, and controls the fluid that flows out of the hydraulic actuator, and a hydraulic pressure when descending by power. A power down control position for controlling the fluid flowing from the actuator to the tank and the fluid flowing from the pressure source to the hydraulic actuator; It has a fourth control position, the check valve,
When it descends due to its own weight, it opens with the back pressure of the tank line and guides the fluid flowing into the hydraulic actuator from the tank line,
It is an up-and-down hydraulic circuit characterized in that it blocks the flow of fluid when descending by power.

According to the present invention, in the lifting hydraulic circuit as set forth in the preceding paragraph, the hydraulic control valve includes a rising control position, a neutral control position,
The present invention is characterized in that it is an electromagnetic proportional direction / flow control valve having four control positions arranged in the order of description of its own weight lowering control position and power lowering control position. The electromagnetic proportional direction / flow control valve has four control positions which are arranged in the order of the position, the neutral control position, the power lowering control position, and the own weight lowering control position.

The present invention also provides a hydraulic actuator, first
A hydraulic circuit for raising and lowering a mass in an elevating device such as a mold opening and closing device of a vertical press provided with a hydraulic control valve, a second hydraulic control valve and a check valve, wherein the first hydraulic control valve is Neutral control position to stop the fluid inflow from the pressure source to the hydraulic actuator and the fluid outflow from the hydraulic actuator to the tank when the elevator is stopped, and the fluid flowing from the pressure source to the hydraulic actuator and the outflow from the hydraulic actuator to the tank when rising. And a self-weight lowering control position for controlling the fluid flowing out of the hydraulic actuator by stopping the inflow of the fluid from the pressure source to the hydraulic actuator when descending. The hydraulic control valve has a self-weight lowering control position that stops the flow of fluid from the pressure source to the hydraulic actuator when descending due to its own weight, and a hydraulic actuator from the pressure source when descending due to gravity. The check valve has two control positions, a power lowering control position for controlling the fluid flowing into the tank, and the check valve opens at the back pressure of the tank line when descending due to its own weight to guide the fluid flowing into the hydraulic actuator from the tank line, It is an up-and-down hydraulic circuit characterized in that it blocks the flow of fluid when descending by power.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention including the above-mentioned solving means will be described below with reference to the accompanying drawings in which embodiments are shown.

A hydraulic circuit will be used to explain one of the lifting hydraulic circuits according to the present invention. This hydraulic circuit controls a lifting device for lifting a heavy load such as a mold of a tire vulcanizer. A hydraulic cylinder (hydraulic actuator) connected to a heavy load, a control valve (hydraulic pressure control valve) such as a proportional valve, a hydraulic pump (pressure source), and an oil tank. A predetermined oil flow path is opened / closed so that a suction circuit from the tank is formed when the heavy load is lowered and a normal double-action circuit is formed when the heavy load is lowered. And a check valve (see FIG. 1).

The control valve is, for example, an electromagnetic proportional directional / flow rate control valve, and has four control positions of a rising control position, a neutral control position, a self-weight lowering control position, and a power lowering control position.
By setting the control valve to the neutral control position, it is possible to stop the pressure oil from flowing in and out of the hydraulic cylinder and stop the heavy load at a predetermined position. To increase the heavy load, the control valve can be switched to the lift control position, and the oil from the pressure source flows into the rising volume increasing side chamber (falling volume decreasing side chamber) of the hydraulic cylinder through the control valve. On the other hand, the oil flowing out of the rising volume decreasing side chamber (falling volume increasing side chamber) of the hydraulic cylinder flows into the oil tank through the control valve, and thus the normal double-action circuit can perform the rising control.

To lower the heavy load, it is possible to lower the weight by utilizing the high weight of the load itself or by lowering the power using a pressure source. In the case of lowering the weight,
When the control valve is switched to the self-weight lowering control position, the oil from the pressure source is blocked by the control valve and the flow is stopped, while the oil flowing out from the volume reducing side chamber of the hydraulic cylinder when it descends passes through the control valve to the tank line. To generate back pressure. The check valve is opened by this back pressure, and a part of the oil flowing in the tank line flows through the check valve into the volume increasing side chamber when the hydraulic cylinder descends. As a result, the descending volume increasing chamber remains filled with oil regardless of the volume change. The lowering speed can be controlled by adjusting the opening of the control valve.

In this way, in the case of the self-weight lowering control, power can be saved and energy can be saved, and the damping of the circuit is sufficiently large so that vibration is unlikely to occur at the time of shifting and the speed control is easy. Further, when the hydraulic cylinder descends, the volume reduction side chamber does not cause cavitation due to insufficient flow rate.

Next, in the case of power down, the control valve is switched to the power down control position. The oil from the pressure source flows into the lower volume increasing side chamber of the hydraulic cylinder while the flow rate is adjusted by the control valve, while the oil flowing from the lower volume decreasing side chamber of the hydraulic cylinder flows into the tank line via the control valve. Therefore, the high weight load can be lowered by the thrust of the pressure of the pressure source, which is effective when applied to, for example, mold clamping.

The control valve is an electromagnetic proportional directional / flow rate control valve (see FIG. 1) having four control positions arranged in the order of ascending control position, neutral control position, self-weight lowering control position and power lowering control position. Therefore, if the self-weight lowering control position is on the side closer to the neutral control position, basically most of the control can be performed by self-weight lowering, and the effect of saving energy and shortening the cycle time becomes large.

On the other hand, the control valve is an electromagnetic proportional directional / flow control valve having four control positions which are arranged in the order of ascending control position, neutral control position, power lowering control position and own weight lowering control position (see FIG. 4). ) And the power lowering control position is located closer to the neutral control position, it is possible to perform control such that the power flow is lowered in the small flow rate region, that is, the low speed region, and the weight is lowered in the high speed region.
That is, it is a general control to decelerate to a low speed before stopping the descent, and a large descent thrust can be obtained near the descent end where the descent resistance becomes large without any special operation. It is advantageous in that it can be done.

The hydraulic circuit as the lifting hydraulic circuit of the present invention described above is characterized in that one control valve such as a proportional valve having a structure capable of controlling the direction and the flow rate is provided in the circuit. However, in contrast to this, another hydraulic pressure circuit according to the present invention described below is configured so that two control valves having a relatively simple structure can be used in combination to achieve the same function. The hydraulic circuit as a lifting hydraulic circuit has a characteristic that a hydraulic cylinder (a hydraulic actuator) connected to a heavy load, a first control valve (a first hydraulic control valve) such as a switching valve, and a switching circuit. A second control valve such as a valve (second hydraulic pressure control valve),
A hydraulic control unit that includes a hydraulic pump (pressure source) and an oil tank as element members, and a regeneration circuit is formed when a heavy load is lowered, and a normal double-action circuit is formed when it is raised. And a check valve for opening and closing a predetermined oil passage (see FIG. 7).

As the first control valve, for example, a three-position type electromagnetic directional control valve is used and has three control positions of an ascending control position, a neutral control position and a self-weight lowering control position. By setting the first control valve to the neutral control position, it is possible to stop the pressure oil from flowing in and out of the hydraulic cylinder and stop the heavy load at a predetermined position. In order to increase the heavy weight load, the first control valve may be switched to the rising control position, and the oil from the pressure source may flow through the first control valve to the volume increasing side chamber (the volume decreasing side chamber when descending) of the hydraulic cylinder. ), While the oil flowing out of the ascending volume decreasing side chamber (decreasing volume increasing side chamber) of the hydraulic cylinder flows into the oil tank via the first control valve, thus rising by the normal double-action circuit. It can be controlled.

In the case of the self-weight lowering, when the first control valve is switched to the self-weight lowering control position, the oil from the pressure source is blocked by the first control valve and the circulation is stopped, while the volume decrease of the hydraulic cylinder when the hydraulic cylinder descends is reduced. The oil flowing out of the side chamber flows into the tank line via the first control valve to generate back pressure. Due to this back pressure, the check valve is opened, and a part of the oil flowing in the tank line flows through the check valve to the volume increasing side chamber of the hydraulic cylinder when it descends, forming a so-called regeneration circuit. As a result, the descending volume increasing chamber remains filled with oil regardless of the volume change. The lowering speed can be controlled by meter-out control using a separately provided throttle valve.

The second control valve is, for example, a two-position electromagnetic directional control valve, and has two control positions, a self-weight lowering control position and a power lowering control position. This second control valve blocks the oil from the pressure source by the second control valve when it is set to its own weight lowering control position to stop the flow, and when it is switched to the power lowering control position, the oil from the pressure source is switched. Is provided in the hydraulic circuit so as to flow into the volume increasing side chamber when the hydraulic cylinder descends via the second control valve.

When powering down a heavy load, by setting the second control valve to the power-down control position while the first control valve is set to the self-weight-down control position, the oil from the pressure source is controlled by the second control. The oil flowing into the lower volume increasing side chamber of the hydraulic cylinder through the valve, while the oil flowing out of the lower volume decreasing side chamber flows into the tank line through the first control valve,
As a result, the power is lowered with the downward thrust increased.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a hydraulic circuit diagram according to an embodiment of the present invention. The illustrated hydraulic circuit is used to drive an elevating device that elevates and lowers a mold of a tire vulcanizer, and includes a hydraulic pump 11 serving as a pressure source and a hydraulic source device including an oil tank 12. For example, a hydraulic actuator 1 realized by a hydraulic cylinder connected to a high weight load W such as an upper mold of a tire vulcanizer, a hydraulic pressure control valve 2A realized by a proportional valve, a pilot check valve 3, A load side control unit including an electromagnetic switching valve 4 for opening and closing the check valve 3, a check valve 5 and a back pressure valve 6 is provided.

Proportional valve 2A in the load side control unit
Is a pressure source P, tank T, load A, load B 4 ports,
It is an electromagnetic proportional control valve that can change direction and adjust flow rate with its own weight lowering control position (a1), power lowering control position (a2), neutral control position (b), and rising control position (c). The T port is connected to the tank line having the back pressure valve 6 in the pipeline, the P port is connected to the pump line, and the A port is connected to the head side oil chamber of the hydraulic cylinder 1 via the pilot check valve 3. And the B port is connected to the rod-side oil chamber of the hydraulic cylinder 1.

The pilot check valve 3 is provided in the pipeline so as to allow the oil flowing from the A port toward the oil chamber on the head side of the hydraulic cylinder 1 and to prevent the opposite flow. On the other hand, the check valve 5 is provided in a pipe line that connects the tank line and the rod-side oil chamber of the hydraulic cylinder 1, and allows the flow of oil flowing from the tank line to the rod-side oil chamber. Reverse circulation is provided to prevent it.

A mode in which the hydraulic circuit shown in FIG. 1 causes the heavy load W to move up and down will be described below. (1) When lifting / lowering is stopped: As shown in FIG. 1, the proportional valve 2 is in the non-excited state and is in the neutral control position (b), the electromagnetic switching valve 4 is in the non-excited state, and the hydraulic cylinder 1 has the piston rod lowered. Stopped at.

(2) When rising: The proportional valve 2A is excited to switch to the rising control position (c). Oil from the pump line of the pressure source flows from the P port of the proportional valve 2A to the A port, passes through the pilot check valve 3 and flows into the head side oil chamber of the hydraulic cylinder 1. The oil flowing out of the rod-side oil chamber of the hydraulic cylinder 1 flows from the B port of the proportional valve 2A to the T port and flows out to the tank line. In this case, the flow rate is controlled by controlling the opening of the proportional valve 2A by current control. Since this ascending operation is performed by a normal double-action circuit, the flow rate control including acceleration / deceleration can be easily performed.

(3) When descending (descending weight): Solenoid switching valve 4
Is excited to open the pilot check valve 3, and the proportional valve 2A is excited to switch to the own weight lowering control position (a1). The piston rod of the hydraulic cylinder 1 is lowered by the self-weight of the high weight load W, and the oil flowing out of the head side oil chamber passes through the pilot check valve 3 and flows from the A port of the proportional valve 2A to the T port to the tank line. leak. A back pressure is generated in the outflowing oil when passing through the back pressure valve 6,
The check valve 5 is opened by the action of the back pressure, and a part of the oil flowing out to the tank line flows into the rod side oil chamber of the hydraulic cylinder 1. Therefore, the rod-side oil chamber remains filled with oil, and therefore cavitation does not occur.

In this case, the flow rate of the oil flowing out to the tank line due to its own weight lowering is a so-called meter-out control which is performed by controlling the opening degree from the A port to the T port by the current control of the proportional valve 2A. The head-side oil chamber of the hydraulic cylinder 1 is connected to the tank line via the throttle mechanism formed in the proportional valve 2A, and the rod-side oil chamber is connected to the tank line via the check valve 5. Therefore, it is easy to perform speed control including vibration including acceleration / deceleration without generating vibration. Further, unlike the case of the differential circuit, the head-side oil chamber does not have a high pressure when the weight is lowered.

When the weight is lowered to approach the target stop position, the opening of the proportional valve 2A is reduced to decelerate, and when the target position is reached at a low speed, it is stopped. At that time, for example, in the case of die casting, it is necessary to apply a mold clamping force to the upper mold and the lower mold by the hydraulic cylinder 1, or between the upper mold and the lower mold like a tire vulcanizer. Since it is necessary to tighten the tires, the thrust force may be insufficient only by the weight of the lifting device.

(4) Down (power down): When the thrust is insufficient as described above, the resistance to the down increases and the down speed decreases or stops, and then the excitation of the proportional valve 2A is further strengthened to control the down power. Switch to position (a2). By this switching, the oil from the hydraulic pump 11 flows from the P port of the proportional valve 2A to the B port and flows into the rod side chamber, and the thrust of the hydraulic pump 11 causes the piston rod of the hydraulic cylinder 1 to descend. The lowering speed can be controlled to be high or low by the opening control by the current control of the proportional valve 2A, as described above.

In the hydraulic circuit shown in FIG. 1 described above, the proportional valve 2A has the rising control position (c) and the neutral control position.
(b) Since the weight lowering control position (a1) and the power lowering control position (a2) are arranged side by side in the valve axis direction,
Since the self-weight lowering control position (a1) is located on the side closer to the neutral control position (b), basically most of the control can be performed by self-weight lowering, which has a large energy saving effect. Can be lowered at high speed, and the cycle time of the entire lifting device can be shortened.

The structure of the main part and the opening degree characteristic of the proportional valve 2A are as shown in FIGS. 2 and 3, respectively. The proportional valve 2A has T, A, P, B and T in the valve body 13. Each of the five ports is provided in order from the right side to the left side in FIG. 2, these ports face the spool 14 described later, and the T ports at both ends communicate with each other in the valve body 13. On the other hand, the spool 14 slidably accommodated in the valve body 13 has four notches (notches) 15a-15
d is cut in the land. The state of FIG. 2 shows the neutral control position (b), and when the spool 14 slides to the right from this state, the P port and the A port communicate with each other by the notch 15b, and the B port by the notch 15d.
The port and the T port communicate with each other, and the opening degree (cross-sectional area of the notch) increases together with the increase of the spool stroke. This right moving area is the ascending control position (c)
Corresponding to.

When the spool 14 slides to the left from the neutral control position (b), the notch 15a causes A
The port and the T port communicate with each other, and the opening degree increases as the movement amount increases. The P port and the B port communicate with each other by the notch 15c during the movement, and the opening increases as the movement amount increases. Therefore, the self-weight lowering control position is adjusted according to the movement amount of the spool.
The power lowering control position (a2) is switched in order from (a1). Thus, in the proportional valve 2A, the proportional relationship as shown in FIG. 3 is established between the spool stroke and the valve opening degree of each port,
It is possible to control the oil flow direction and flow rate with a single valve.

FIG. 4 shows a hydraulic circuit according to another embodiment of the present invention. The hydraulic circuit shown in FIG. 4 is similar to the hydraulic circuit of the embodiment shown in FIG. 1, and corresponding members are designated by the same reference numerals. Since the basic form of the hydraulic circuit in this embodiment is the same as that of the embodiment shown in FIG. 1, description thereof will be omitted, and the characteristic configuration will be described below. The points of interest in this example are:
The structure and opening characteristic of the proportional valve 2B are different from those of the proportional valve 2A in the above-described embodiment.

That is, referring to FIGS. 5 and 6 showing the main part structure and opening characteristic of the proportional valve 2B, the spool 14 slidably accommodated in the sleeve fitted to the valve body 13 is Has five notches (cutouts) 15e to 15i cut in the land portion. The state of FIG. 5 shows the neutral control position (b), and when the spool 14 slides to the left from this state, the P port and the A port communicate with each other by the notch 15f, and the B port by the notch 15i. The port and the T port communicate with each other, and the opening degree (cross-sectional area of the notch) increases together with the increase of the spool stroke. This leftward moving area corresponds to the ascending control position (c).

When the spool 14 slides to the right from the neutral control position (b), the notch 15e causes A
The port communicates with the T port, the notch 15g communicates with the P port and the B port, and the opening increases together with the increase of the spool stroke, and the P port and the B port are in the middle of the movement. The opening between them is narrowed by the notch 15h and finally closed. The opening degree between the A port and the T port continues to increase. Therefore, the rightward moving region of the preceding stage corresponds to the power down control position (a11).

When the spool 14 further slides to the right from the power down control position (a11), the notch 15e
The opening between the A port and the T port communicating with each other increases as the amount of movement increases, while the P port and the B port remain closed, so that the spool In accordance with the amount of movement, when it comes to the rightward movement region in the subsequent stage, the state of the power lowering control position (a11) is switched to the state of the own weight lowering control position (a12). In this way, the proportional valve 2B establishes the proportional relationship between the spool stroke and the valve opening of each port as shown in FIG. 6, and the flow direction and flow rate of oil can be controlled by a single valve. Is.

A mode in which the hydraulic circuit shown in FIG. 4 causes the heavy load W to descend is described below. When the proportional valve 2B is switched to the power lowering control position (a11), the power lowering control position is set. Since the valve opening is small, it is in the low speed region. When accelerating, the valve is opened to the dead weight control position (a12) by passing through the power down control position (a11), and the dead weight control position is reached.

To stop at the target position, the high speed self-weight lowering of the self-weight lowering control position (a12) is returned to the power lowering control position (a11). This causes the power to drop, but switches to low speed operation. For example, when the upper die and the lower die come into contact with each other and stop, the rod pressure rises due to the fluid flowing from the pressure source into the rod side chamber, and the lowering thrust of the cylinder becomes large, so that the die can be clamped. is there.

In the hydraulic circuit according to the other embodiment, the proportional valve 2B is described in the ascending control position (c), the neutral control position (b), the power lowering control position (a11) and the own weight lowering control position (a12). Since the structures are arranged side by side in the valve axis direction in sequence, the power lowering control position (a11) is located closer to the neutral control position (b), so power lowering operation is always performed at low speeds in the small flow rate range. Although the effect of saving energy and shortening the cycle time is smaller than that of the embodiment shown in FIG. 1, a large descending thrust can be obtained without any special operation near the descending end where the descending resistance becomes large. It is convenient in terms of operation.

FIG. 7 shows a hydraulic circuit according to another embodiment of the present invention. The basic mode of the illustrated hydraulic circuit is similar to the above-described embodiments shown in FIGS. 1 and 4, and among the respective members in this hydraulic circuit, each member in both of the above-mentioned embodiments is Corresponding components are designated by the same reference numerals, and detailed description thereof will be omitted. The points to be noted regarding the configuration of the present embodiment shown in FIG. 7 are two first hydraulic pressure control valves 9 and two second hydraulic pressure control valves 10 realized by, for example, electromagnetic switching valves, and two throttle valves 7. , 8 are provided in the load side control unit in place of the proportional valve 2.

First hydraulic pressure control valve (abbreviated as first switching valve)
9 has a pressure source P, a tank T, four ports of load A and load B, and three control positions of its own weight lowering control position (a21), neutral control position (b), and ascending control position (c). A switchable electromagnetic switching valve, in which a T port is connected to a tank line, a P port is connected to a pump line, and an A port is a throttle valve 8 for raising control and a throttle valve 7 for lowering control. A pipe passage having a pilot check valve 3 in series is connected to the head side oil chamber of the hydraulic cylinder 1, and the B port is connected to the rod side oil chamber of the hydraulic cylinder 1.

Second hydraulic pressure control valve (abbreviated as second switching valve)
Reference numeral 10 is an electromagnetic switching valve that has two ports, a pressure source P and a load A, and two control positions, a self-weight lowering control position (a31) and a power lowering control position (a32), which can be opened and closed. P port is connected to pump line, A port is hydraulic cylinder 1
It is connected to the oil chamber on the rod side.

A mode in which the hydraulic circuit shown in FIG. 7 performs the lifting operation of the high weight load W will be described below. (1) Ascending: The first switching valve 9 is switched to the rising control position (c) and the second switching valve 10 is switched to the closed position of the own weight lowering control position (a31). The maximum speed of the oil flowing through the A port of the first switching valve 9 and flowing into the head side oil chamber of the hydraulic cylinder 1 is controlled by the throttle valve 8. The control at this time is meter-in control.

(2) At the time of lowering: The solenoid valve 4 is excited to open the pilot check valve 3, the first switching valve 9 is switched to its own weight lowering control position (a21), and the second switching valve 10 is set to its own weight lowering control position. By keeping the value as (a31), the operation of lowering its own weight is performed. The maximum speed of the descent at this time is the throttle valve 7
Meter-out control. Oil is sucked into the rod-side oil chamber of the hydraulic cylinder 1 from the tank line via the check valve 5.

When the resistance is increased near the end of the descent of the own weight and the descending speed due to the own weight is reduced or stopped, the second switching valve 10 is switched to the open state of the power down control position (a32). The oil is caused to flow from the pressure source into the rod-side oil chamber of the hydraulic cylinder 1 to perform the power lowering operation in which the lowering thrust is increased. In this way, the switching between the self-weight lowering operation and the power lowering operation can be smoothly performed by the two solenoid valves 9 and 10 having a simple structure.

In each of the embodiments described above, a hydraulic cylinder is used as the hydraulic actuator. However, the present invention may use a hydraulic motor instead of the hydraulic cylinder. It is not limited. The back pressure valve 6 is a member provided for the purpose of complementing the fluid suction performance of the check valve 5,
It goes without saying that the back pressure valve 6 may be omitted if there is originally sufficient back pressure in the tank line.

[0051]

According to the lifting / lowering hydraulic circuit of the present invention having the above-described structure and functioning, speed control can be facilitated by increasing the mass by using a normal double-action circuit. . On the other hand, at the time of descending, both the self-weight lowering by mass and the hydraulic power down can be selectively used according to the purpose, and the self-weight lowering control saves power and saves energy, and the cycle time can be shortened. Since the hydraulic power can be effectively used in the power down control,
A thrust larger than the downward thrust due to its own weight can be taken out as required.

Even when the weight is lowered, the circuit on one side of the hydraulic actuator is connected to the tank via the hydraulic control valve, and the circuit on the other side is connected to the tank via the check valve. The damping of the circuit is sufficiently large, so that vibration is unlikely to occur during gear shifting and speed control can be performed easily and accurately. Further, even if the hydraulic actuator is a cylinder, it does not form a differential circuit, so that the pressure due to the load does not become high.

The present invention also has, as the hydraulic control valve, four control positions which are arranged in the order of the ascending control position, the neutral control position, the own weight lowering control position, and the power lowering control position, and are located closer to neutral. Electromagnetic proportional direction in which the control position for lowering the own weight exists
By using the flow rate control valve, basically all can be controlled by its own weight lowering, and energy saving and cycle time reduction effects can be achieved.

The present invention also has, as a hydraulic pressure control valve, four control positions which are arranged in the order of the ascending control position, the neutral control position, the power lowering control position and the own weight lowering control position. Electromagnetic proportional direction with power down control position
By using a flow control valve, it is easy to operate with a power down in a small flow range, that is, a low speed range, and with a self-weight lowering in a high speed range. Therefore, it can be applied to a press machine or the like that requires mold clamping. There is an effect that convenience can be achieved.

[Brief description of drawings]

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

FIG. 2 is a structural diagram of a main part of a proportional valve 2 in FIG.

3 is an opening characteristic diagram of the proportional valve 2 in FIG.

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

5 is a structural diagram of the main part of the proportional valve 2 in FIG.

6 is an opening characteristic diagram of the proportional valve 2 in FIG.

FIG. 7 is a hydraulic circuit diagram according to another embodiment of the present invention.

FIG. 8 is a hydraulic circuit diagram of a conventional example.

FIG. 9 is a hydraulic circuit diagram of a conventional example.

10 is an explanatory diagram of dynamic characteristics of the hydraulic circuit of FIG.

[Explanation of symbols]

1 ... hydraulic actuator (hydraulic cylinder) 2A ... hydraulic control valve (proportional valve) 2B ... hydraulic control valve (proportional valve) 3 ... pilot check valve 4 ... electromagnetic switching valve 5 ... check valve 6 ... back pressure valve 7 ... throttle Valve 8 ... Throttle valve 9 ... First
Hydraulic pressure control valve (switching valve) 10 ... 1st hydraulic pressure control valve (switching valve) 11 ... Pressure source (hydraulic pump) 12 ... Tank (oil tank) 13 ... Valve body 14 ... Spool 15 ... Notch W ... Heavy load (a1) ... self-weight lowering control position (a2) ... power lowering control position (b) ... neutral control position (c) ... rising control position

Claims (4)

[Claims] 1. A hydraulic circuit for raising and lowering a mass in an elevating device such as a mold opening and closing device of a vertical press including a hydraulic actuator, a hydraulic control valve and a check valve, wherein the hydraulic control valve comprises: Neutral control position to stop the fluid inflow from the pressure source to the hydraulic actuator and the fluid outflow from the hydraulic actuator to the tank when the elevator is stopped, and the fluid flowing from the pressure source to the hydraulic actuator and the outflow from the hydraulic actuator to the tank when rising. Control position to control the fluid to be controlled, a control position to control the fluid flow from the pressure source to the hydraulic actuator when it descends due to its own weight and to control the fluid flowing out of the hydraulic actuator, and a hydraulic actuator to control the fluid when it descends due to power. From the power down control position that controls the fluid flowing out of the tank to the tank and the fluid flowing into the hydraulic actuator from the pressure source. Has a control position and the check valve
When it descends due to its own weight, it opens with the back pressure of the tank line and guides the fluid flowing into the hydraulic actuator from the tank line,
A lifting hydraulic circuit characterized by blocking the flow of fluid when descending by power. 2. The hydraulic pressure control valve is an electromagnetic proportional directional / flow control valve having four control positions which are arranged in the order of an ascending control position, a neutral control position, a self-weight lowering control position, and a power lowering control position. The lifting hydraulic circuit according to Item 1. 3. The hydraulic pressure control valve is an electromagnetic proportional directional / flow control valve having four control positions which are arranged in the order of an ascending control position, a neutral control position, a power lowering control position, and a self-weight lowering control position. The lifting hydraulic circuit according to Item 1. 4. A hydraulic actuator, a first hydraulic control valve,
A hydraulic circuit for elevating and lowering a mass in an elevating device such as a mold opening and closing device of a vertical press provided with a second hydraulic control valve and a check valve, wherein the first hydraulic control valve is a pressure source when stopping elevating. Control position to stop fluid inflow from the hydraulic actuator to the hydraulic actuator and outflow from the hydraulic actuator to the tank, and control the fluid flowing from the pressure source to the hydraulic actuator and the fluid flowing from the hydraulic actuator to the tank when rising The second hydraulic control valve has three control positions, that is, an ascending control position and a self-weight lowering control position that controls the fluid flowing from the hydraulic actuator by stopping the fluid inflow from the pressure source to the hydraulic actuator when descending. , A self-weight lowering control position to stop the fluid from flowing from the pressure source to the hydraulic actuator when descending due to its own weight, and to flow into the hydraulic actuator from the pressure source when descending due to gravity It has two control positions, a power lowering control position for controlling the fluid, and the check valve opens with the back pressure of the tank line when lowering due to its own weight and guides the fluid flowing into the hydraulic actuator from the tank line, and when lowering due to power A lifting hydraulic circuit characterized by blocking the flow of fluid.