JPH01244812A - Hydraulic device for mold clamping - Google Patents

Abstract

PURPOSE:To enable the title device to perform decompression in a short period of time without causing a shock, by a method wherein discharge pressure of an axial pump and holding pressure of a mold clamping cylinder are balanced at the time of the decompression and the mold clamping cylinder is decompressed through negative inclination movement operation of the axial pump from this state. CONSTITUTION:Supply of hydraulic oil to an axial pump 1 of swash plate type capable of moving to a positive or negative inclination is controlled by a main control valve 3 and a mold clamping cylinder 4 actuating with the hydraulic oil to be supplied through the axial pump 1 through changeover of the main control valve 3 and an operating state of the axial pump 1 are controlled by a controller 5. The controller 5 balances discharge pressure of the axial pump 1 with holding pressure for mold clamping of the mold clamping cylinder 4 and makes a command signal for pressure lowering to the axial pump 1 in this balanced state. Negative inclination movement operation of the axial pump 1 is performed based on the command signal for the pressure lowering and decompresses the mold clamping cylinder 4. Since the discharge pressure of the pump 1 is the same pressure as the holding pressure for the mold clamping of the mold clamping cylinder 4 and is under a balanced state of the pressure, generation of a shock at the time of decompression is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a hydraulic system for clamping a mold in an injection molding machine, etc., and is aimed at improving a means for releasing pressure from a clamping cylinder.

(Prior Art) As a conventional mold clamping hydraulic system, one of the form shown in FIG. 5 is generally known. This hydraulic system includes a variable displacement hydraulic pump (25), a main control valve (26), a mold clamping cylinder (27), etc., and includes a pressurizing path (27) during mold clamping.
An electromagnetic pressure relief valve (28) is provided on the a) side. (29
) is a pump control valve for controlling the operating state of the hydraulic pump (25).

The mold clamping cylinder (27) is held under pressure in a mold clamping state until, for example, the molding cycle of the injection molding machine ends and the product is solidified and cooled. This pressurization pressure reaches over 100 kg/cd, and when the main control valve (26) is suddenly switched to the solenoid (26a) side when the mold is opened, the hydraulic oil returns with an impact and flows into the oil passage, causing a shock. occurs. A pressure relief valve (28) is provided to prevent such a shock.

This pressure relief valve (28) is equipped with a throttle passage (30),
Prior to the switching operation of the solenoid (26a) of the main control valve (26), the drain state is switched, and the throttle passage (30)
The pressure is relieved without causing a shock.

(Problem to be solved by the invention) Regarding maintaining pressure in the cylinder (27) during mold clamping,
Although configuring the main control valve (26) such that all ports are blocked in the neutral position as described above is advantageous in terms of reducing the load on the pump (25), the pressure relief valve (28) is essential. , the number of parts increases accordingly, and the cost also increases.

Further, the pressure relief valve (28) needs to shorten the pressure relief time without causing a shock, but it is difficult to achieve this balance, and it is difficult to select an appropriate valve size and throttle amount.

This invention has been proposed in view of the above, and takes advantage of the fact that the hydraulic pump is a swash plate type axial plunger pump and that this pump has reversibility between the suction function and the discharge function. Reducing the manufacturing cost of hydraulic equipment by depressurizing the mold clamping cylinder;
The purpose of the present invention is to shorten the molding cycle by making it possible to perform depressurization in a short time without causing shock.

(Means for Solving the Problems) This invention is based on the premise that the hydraulic pump of the mold clamping hydraulic system is composed of a swash plate type axial plunger pump (hereinafter simply referred to as an axial pump) that can tilt in the positive and negative directions. At the time of pressure relief, the discharge pressure of the axial pump and the holding pressure of the mold clamping cylinder are balanced, and from this state, the axial pump is operated in a negative tilt direction to relieve the pressure of the mold clamping cylinder.

Specifically, as shown in Figure 1, the mold clamping hydraulic system is
A swash plate type axial pump (1) that can tilt in the positive and negative directions, a main control valve (3) that controls the supply of hydraulic oil to the axial pump (1), and a main control valve (3) that controls the axial pump by switching the main control valve (3). It consists of a mold clamping cylinder (4) operated by hydraulic oil supplied from a pump (1), a controller (5) that controls the operating state of the axial pump (1), and the like. Then, the controller (5) is configured to balance the discharge pressure of the axial pump (1) with the mold clamping pressure of the mold clamping cylinder (4), and in this balanced state, issue a pressure drop command signal to the axial pump (1). The axial pump (1) is operated in a negative tilt direction based on the pressure drop command signal to relieve pressure from the mold clamping cylinder (4).

(Function) The hydraulic system configured as described above uses an axial pump (
The control swash plate (9) of 1) is controlled by the controller (5) and its discharge amount changes, so that the discharge pressure of the pump (1) is equal to the mold clamping holding pressure of the mold clamping cylinder (4). Since the pressure is in a state of equilibrium, shocks are prevented from occurring when the pressure is released. From this pressure equilibrium state,
The control swash plate (9) of the axial pump (1) is controlled based on the pressure drop command signal from the controller (5) and tilts negatively, so that the hydraulic fluid in the discharge passage (12) is transferred to the axial pump (1). The mold clamping cylinder (4) is discharged to the suction path (13) side through the mold clamping cylinder (4).

(Embodiment) FIGS. 1 to 4 show an embodiment in which the present invention is applied to an injection molding machine. In Fig. 2, the mold clamping hydraulic system is composed of a pump unit (2) including an axial pump (1), an electromagnetic main control valve (3), a mold clamping cylinder (4), etc. The pump unit (2) and the main control valve (3) are controlled by an operation command signal from the controller (A). The main control valve (3) consists of a 4-point, 3-position switching valve in which all ports are blocked in a non-communicating manner in the neutral position, and can be switched between the mold clamping position and the mold opening position by sandwiching the neutral position. It is configured. Operate this main control valve (3) to the mold clamping position and move the mold clamping cylinder (4)
The pressure in the mold clamping cylinder (4) can be maintained by placing the cylinder in the mold clamping position and returning the main control valve (3) to the neutral position while maintaining the pressurized state.

The pump unit (2) is an axial pump (1)
, a controller (5) that controls the operating state of this pump (1), and a pump control valve (6) that controls and operates the pump (1) in response to an operation command signal from this controller (5).
, a relief valve (7), etc., are configured as one unit. In FIG. 1, the axial pump (1) is equipped with a control swash plate (9) that changes the operating stroke of the plunger (1a).
9) is oscillated by an increase control plunger (10) and a decrease control plunger (11) provided above and below the cylinder block (1b) to increase or decrease the discharge pressure and also to reverse the suction/discharge direction. It is. In other words, in addition to the positive tilting state shown in Figure 1, it can also be operated in the negative tilting state shown in Figure 3, and in the negative tilting state, the plunger (1a) sucks hydraulic oil from the discharge passage (12). It is configured so that it can be sent out to the suction path (13) side.

The control increase plunger (10) is always urged to protrude by a spring (14), and its oil chamber (10a) is communicated with the discharge passage (12) of the axial pump (1). Also,
The oil chamber (11a) of the reduction control plunger (11) is communicated with the discharge passage (12) via the pump control valve (6),
By switching the pump control valve (6), the oil chamber (11a) is brought into communication with either the discharge passage (12) or the drain passage (15). This oil chamber (
11a) is in communication with the drain passage (15), the discharge pressure acts only on the increase control plunger (10).
The control swash plate (9) is tilted upwardly to the left as viewed in the figure, and the discharge amount of the axial pump (1) increases. Conversely, when the discharge pressure is applied to the oil chamber (11a), the reduction control plunger (11) with a large cross-sectional area advances and the control swash plate (
9) is pushed back toward the vertical position to reduce the pump discharge amount.

In FIG. 1, the controller (5) is the control circuit (5a)
and a sensor circuit (5b), and a main engine controller (A
) The pump control valve (6) is electromagnetically operated based on command signals such as discharge pressure and discharge amount from the pump. In addition, the control swash plate (
9) and a pressure sensor (18) that detects the discharge pressure of the discharge passage (12).
), and the output signals of both (17) and (18) can be compared by the sensor circuit (5b) to confirm the control results.

As mentioned above, the controller (5) operates the axial pump (5) according to the operation command signal from the main engine controller (A).
For example, during mold clamping, the control swash plate (9) is tilted to the maximum pressure, and the pump control valve (6) is controlled so that the discharge pressure reaches the maximum value. Further, the control swash plate (9) is tilted so that the discharge pressure reaches the maximum value even when the pressure is released.

The pump control valve (6) consists of a pilot valve (6A) consisting of a three-point/two-position switching valve that is electromagnetically operated by the controller (5), and a safety valve (6B). The pilot valve (6A) is biased in an offset state by a spring (19), and in this state, the pressure in the discharge passage (12) comes to act on the oil chamber (11a) of the reduction control plunger (11). There is.

The controller (5) also controls the pilot valve (6A).
When a driving current is applied to the solenoid (20), it moves against the spool or spring (one) and closes the oil chamber (11).
a) communicates with the drain passage (15).

In order to release pressure from the mold clamping cylinder (4) which is held in a pressurized state during mold clamping, the main control valve (3) and the axial pump (1) are controlled and operated as follows.

First, the controller (
5) is given a pressure increase command signal. This pressure increase command signal is used to position the control element (9) at a predetermined inclination angle in advance to correspond to the mold clamping force of the mold clamping cylinder (4), and to make its discharge pressure equal to the mold clamping force. Therefore, the solenoid (20) of the pilot valve (6A) is energized based on this pressure increase command signal, and the decrease control plunger (1) is energized.
The oil chamber (11a) of No. 1 communicates with the drain passage (15), and as a result, the control swash plate (9) of the axial pump (1)
is pressed by the increase control plunger (10), its inclination angle becomes larger, and as a result, the discharge amount increases and the discharge pressure increases to the same level as the mold clamping pressure of the mold clamping cylinder (4). Pressure.

This discharge pressure can be easily confirmed by a pressure sensor (18). Next, the main control valve (3) is switched to the mold clamping position, and the discharge passage (12) is connected to the mold clamping passage (4) of the mold clamping cylinder (4).
a). At this time, both roads (12), (4a
) is the same. Therefore, even if the main control valve (3) is switched, no shock occurs and the pressure remains balanced.

Following the pressure equilibrium described above, the controller (5) demagnetizes the solenoid (20). Then, the spool of the pilot valve (6A) is moved to the left by the spring (one), and the oil chamber (1l b) and the drain passage (
15) as well as the oil chamber (llb)
is communicated with the discharge path (12). As a result, the high pressure hydraulic oil in the discharge passage (12) acts on the reduction control plunger (11). In this case, the area of action of the pressure-reducing plunger (11) is larger than that of the pressure-increasing plunger (10), and when high-pressure hydraulic oil is applied, the spring of the control-increasing plunger (10) ( 14), the control swash plate (9) is negatively tilted from the positive tilting state shown in FIG. 1 to the maximum negative tilting state (the tilt angle is minus 5 degrees) shown in FIG.

In addition, due to the negative tilting of the control swash plate (9), the discharge path (12)
The pressure within the pilot valve (6A) and oil chamber (
11a), the control swash plate (9) is operated to the maximum negative tilting state. When the control swash plate (9) moves beyond the vertical position and tilts negatively, the plunger (1a), which had been performing suction on the negative half of the cylinder block (1b) and discharging on the other half, no longer performs suction. and discharge are performed on the opposite half circumference side. Therefore, simultaneously with the negative tilting of the control swash plate (9), the hydraulic oil in the discharge passage (12) is sucked into the axial pump (1) and discharged to the suction passage (13), and due to this reverse discharge. The mold clamping cylinder (4) is depressurized via the discharge passage (12).

Figure 4 shows the oscilloscope data when the pressure is released. As is clear from this data diagram, the pressure in the discharge passage (12) rapidly and uniformly drops simultaneously with the negative tilting of the control swash plate (9), dropping to almost zero in about 0.15 seconds. . Further, after the control swash plate (9) has been tilted to the maximum negative extent, it is immediately returned to the positive tilting side to maintain the unloading operation state.

After the pressure release is completed, the discharge pressure of the axial pump (1) is increased and the main control valve (3) is switched to the mold open position to separate the mold and take out the product.

According to the mold clamping hydraulic system configured as described above, pressure can be released from the mold clamping cylinder (4) using the axial pump (1) capable of negative tilting, which is not necessary in conventional equipment. The pressure relief valve and its related members can be omitted. Further, after the discharge pressure of the axial pump (1) is balanced with the pressure of the mold clamping cylinder (4), the pressure is relieved by the reverse discharge action, so that the pressure can be quickly relieved without causing a shock.

In addition, in the above embodiment, each plunger (10) for increase/decrease control uses the discharge pressure of the axial pump (1),
(11) to adjust the inclination of the control swash plate (9) using both plungers (10) and (11), but this is not always necessary. For example, the control swash plate (9) may be tilted using motor power or an electric actuator such as a solenoid.

The controller (5) also includes a control swash plate (
The circuit configuration is not limited at all since it should be configured according to the function and structure of the operating member (9) and the pump control valve (6).

In addition, although the mold clamping cylinder (4) is shown as a double-acting type cylinder in the embodiment, it is not necessarily necessary to do so, and a booth clam may be used. Further, either a direct pressure mold clamping method or a trouble mold clamping method may be used.

(Effects of the Invention) As explained above, according to the mold clamping hydraulic system of the present invention, the axial pump (
By using 1), pressure can be relieved using the axial pump (1), so the pressure relief valve and its surrounding parts, which were necessary in conventional equipment, can be omitted, and the manufacturing of the hydraulic system can be reduced accordingly. This made it possible to reduce costs.

In addition, after balancing the discharge pressure of the axial pump (1) with the mold clamping pressure of the mold clamping cylinder (4), the control swash plate (9)
By tilting the axial pump (1) negatively, the axial pump (1)
3) Since the pressure was released by reversely discharging to the side,
Pressure relief can be performed quickly without any shock, which makes it possible to shorten the molding cycle of injection molding machines, etc.

In particular, when the configuration of the main control valve is such that all ports are blocked in a non-communicating state in the neutral state, the axial pump is activated when the main control valve is switched to the mold clamping position. If the discharge pressure is balanced with the mold clamping holding pressure of the mold clamping cylinder, when applied to a mold clamping hydraulic system in which a large number of actuators are connected in parallel to an axial pump, the pressure can be relieved without shock, and the mold can be clamped. Other actuators can be operated smoothly without interference from the operation of one actuator.

In addition, when using a swash plate that can be tilted in positive and negative directions, if an increase control plunger and a negative control plunger are provided to independently tilt the swash plate to the positive side or the negative side, the swash plate can be tilted in a positive or negative direction. The inclination angle can be controlled with high precision.

Furthermore, if the configuration is such that the pump discharge pressure can be applied to the oil chamber of the reduction control plunger of the axial pump, and the effect of this pump discharge pressure on the oil chamber is controlled by the pump control valve, another pressure source is required. Therefore, the control swash plate can be tilted negatively with a simple configuration.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention, FIG. 1 is an explanatory diagram conceptually showing a pump unit, FIG. 2 is a hydraulic circuit diagram showing a hydraulic system, and FIG. 3 is a negative diagram of an axial pump. An explanatory diagram conceptually showing the tilting operation state, and FIG. 4 is an oscillographic data diagram showing the control operation at the time of pressure relief. FIG. 5 is a hydraulic circuit diagram of a conventional device. (1)...Axial pump, (3)...Main control valve, (4)...Mold clamping cylinder, (5)...Controller, (6)...Pump control valve, (9) ...Control swash plate, (10)...Increase control plunger, (11)...Decrease control plunger, (12)...Discharge path, (13)...
・Suction path. Patent applicant Daikin Industries, Ltd. Agent Patent attorney 1) Hiroshi, 7 Patent attorney Chimei-ko Figure 2 Figure 4

Claims (4)

[Claims] (1) Swash plate type axial pump that can tilt in positive and negative directions (1)
, a main control valve (3) that controls the supply of hydraulic oil to the axial pump (1), and a main control valve (3) that controls the hydraulic oil supplied from the axial pump (1) by switching the main control valve (3). A controller (5) that controls the operating state of the operating mold clamping cylinder (4) and the axial pump (1).
The controller (5) balances the discharge pressure of the axial pump (1) with the mold clamping pressure of the mold clamping cylinder (4), and applies pressure to the axial pump (1) in this pressure balanced state. It is configured to output a lowering command signal, and based on the pressure lowering command signal, the axial pump (1) is operated in a negative tilt direction to relieve pressure from the mold clamping cylinder (4). Hydraulic device for mold clamping. (2) The main control valve (3) is composed of a switching valve in which all ports are blocked in a non-communicating state in the neutral state, and the controller (5) controls the discharge pressure of the axial pump (1) by clamping it. The mold clamping hydraulic system according to claim 1, wherein the timing for balancing the mold clamping holding pressure of the cylinder (4) is set when the main control valve (3) is switched to the mold clamping position. (3) The axial pump (1) has an increasing control plunger (10) that operates the control swash plate (9) in the stroke increasing direction.
The mold clamping hydraulic system according to claim 1, further comprising a control plunger (11) for operating the control swash plate (9) in a stroke reduction direction. (4) A pump control valve (6) for controlling the operating state of the axial pump (1) is installed between the discharge passage (12) of the axial pump (1) and the oil chamber (11a) of the reduction control plunger (11). wherein the pump control valve (6) is configured such that the reduction control plunger (11) operates the control swash plate (9) in a negative tilting manner based on a pressure reduction command signal from the controller (5). The mold clamping hydraulic system described in item (3).