JP3502284B2 - Hydraulic circuit of injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of an injection molding machine having a differential mode in which discharged oil discharged from an injection cylinder during injection is used as working oil.

[0002]

2. Description of the Related Art Conventionally, a normal mode in which all the discharged oil discharged from a front oil chamber of an injection cylinder at the time of injection is returned to an oil tank and a difference in which all or part of the discharged oil is supplied to the rear oil chamber of the injection cylinder. A hydraulic circuit of an injection molding machine in which a dynamic mode can be selected is known (for example, Japanese Patent Laid-Open No. 6-2.
46800 gazette etc.). FIG. 3 shows a principle configuration in which such a hydraulic circuit 50 is simplified.

In the figure, when the mode switching valve 51 is switched to the position shown in the figure, that is, to the right symbol R, the normal mode is set, and the hydraulic oil discharged from the hydraulic drive source 52 at the time of injection is injected through the main circuit 53. The oil discharged from the front oil chamber 61f while being supplied to the rear oil chamber 61r of the injection cylinder 61 in the molding machine 60 passes through the right side symbol R of the mode switching valve 51 and the main circuit 53, and is entirely in the oil tank 5.
Returned to 4.

On the other hand, the mode switching valve 51 is set to the left symbol L.
When the mode is switched to the differential mode, the hydraulic oil discharged from the hydraulic drive source 52 at the time of injection is supplied to the rear oil chamber 61r of the injection cylinder 61 via the main circuit 53 and is discharged from the front oil chamber 61f. The discharged oil joins the hydraulic oil from the main circuit 53 through the left symbol L of the mode switching valve 51,
It is supplied to the rear oil chamber 61r of the injection cylinder 61. Therefore, in the differential mode, the discharged oil discharged from the injection cylinder 61 is used as hydraulic oil without being returned to the oil tank 54, so that the hydraulic oil supply amount from the hydraulic drive source 52 is not increased. It is possible to support drive control with a large flow rate, and it is possible to realize a high injection speed, a small oil distribution pipe diameter, and prevention of impact pressure.

[0005]

However, the hydraulic circuit 50 having the differential mode can enjoy the above-mentioned advantages by selecting the differential mode, but on the other hand, even if the supply of hydraulic oil from the main circuit 53 is stopped, Since the exhaust oil discharged from the front oil chamber 61f directly circulates in the rear oil chamber 61r due to the inertia of the piston in the injection cylinder 61, the braking control at the time of the stop control cannot be accurately and accurately performed. Therefore, in the conventional hydraulic circuit, it is necessary to attach a separate braking circuit, and there is a problem to be solved that the number of parts in the hydraulic circuit increases, the cost increases, and the control becomes complicated and unstable. did.

The present invention solves the problems existing in the prior art as described above. By eliminating or simplifying the braking circuit, the number of parts is reduced, the cost is reduced, the control is facilitated and stable. It is an object of the present invention to provide a hydraulic circuit of an injection molding machine, which can dramatically improve molding quality by achieving accurate and accurate braking control.

[0007]

Means and Embodiments for Solving the Problems In the present invention, a normal mode in which all the discharged oil discharged from the front oil chamber 2f of the injection cylinder 2 at the time of injection is returned to the oil tank 3 and all of the discharged oil or A part of the rear oil chamber 2r of the injection cylinder 2
When configuring the hydraulic circuit 1 of the injection molding machine M capable of selecting the differential mode to be supplied to, a four-port servo valve 4 that drives and controls the injection cylinder 2 is provided, and the A port and the B port of this servo valve 4 are The injection cylinder 2 is connected to the front oil chamber 2f and the rear oil chamber 2r, respectively, the P port of the servo valve 4 is connected to the hydraulic drive source 5, and the T of the servo valve 4 is connected.
The port is connected to the oil tank 3 via an on-off valve 6 that switches between a normal mode and a differential mode, and the T
It is characterized in that the port is connected to the rear oil chamber 2r of the injection cylinder 2 via the logic valve 7. In this case, it is desirable to connect a relief valve 8 between the front oil chamber 2f of the injection cylinder 2 and the oil tank 3. Further, by the hydraulic circuit 1s according to another embodiment of the present invention, the T port of the servo valve 4 is connected to the P port via the logic valve 7 instead of being connected to the rear oil chamber 2r via the logic valve 7. May be.

As a result, when the open / close valve 6 is switched to the open side, the normal mode is set, and the T port of the servo valve 4 communicates with the oil tank 3 via the open / close valve 6. In the normal mode, the hydraulic oil from the hydraulic drive source 5 at the time of injection is the servo valve 4
Through the rear of the injection cylinder 2 in the injection molding machine M
The exhaust oil supplied from the front oil chamber 2f while being supplied to the r is returned to the oil tank 3 through the opening / closing valve 6. On the other hand, if the on-off valve 6 is switched to the closed side, the differential mode is set. In the differential mode, the hydraulic oil from the hydraulic drive source 5 at the time of injection is supplied to the rear oil chamber 2r of the injection cylinder 2 via the servo valve 4, and the exhaust oil discharged from the front oil chamber 2f is a logic oil. After passing through the valve 7, it merges with the hydraulic oil from the hydraulic drive source 5 and is supplied to the rear oil chamber 2r of the injection cylinder 2. Then, at the time of stop control, the original stop control by the servo valve 4 is executed, but the front oil chamber 2 of the injection cylinder 2 is
The discharge oil discharged from f is supplied to the rear oil chamber 2r through the servo valve 4 that constitutes the meter-out circuit, so the servo valve 4 also serves as a braking circuit. Therefore, a separate braking circuit is unnecessary or simplified, and accurate and accurate braking control is performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the structure of the hydraulic circuit 1 of the injection molding machine M according to this embodiment will be described with reference to FIG.

Reference numeral M denotes an injection molding machine, and in particular, an injection device Mi in which the mold clamping device is omitted is shown. The injection device Mi includes an injection cylinder 2, and the heating cylinder 1 is provided at the front end of the injection cylinder 2.
An oil motor 12 for screw rotation is attached to the rear end of the injection cylinder 2 while connecting the rear end of the injection cylinder 1. An injection nozzle 13 is provided at the front end of the heating cylinder 11, and a hopper 14 is provided at the rear part of the heating cylinder 11. Further, the heating cylinder 11 has an injection screw 15 built therein, and the rear end of the injection screw 15 is coupled to the front end of a rod portion 16r of a single rod type piston 16 built in the injection cylinder 2.
The interior of the injection cylinder 2 is partitioned by the piston 16 into a front oil chamber 2f and a rear oil chamber 2r. Further, the drive shaft 12s of the oil motor 12 is spline-coupled to the rear end of the piston 16. As a result, the injection screw 15
It moves forward and backward by the injection cylinder 2 and rotates by the oil motor 12.

On the other hand, the hydraulic circuit 1 includes a four-port servo valve 4
Equipped with. The servo valve 4 drives and controls the injection cylinder 2 based on the applied control signal, and the injection screw 15
Servo control is performed for speed, pressure, and position. The servo valve 4 connects the A port to the front oil chamber 2f of the injection cylinder 2 and the B port to the rear oil chamber 2r of the injection cylinder 2.
Connect to. Further, the P port of the servo valve 4 is connected to the discharge side of the hydraulic drive source 5 via the logic valve 21. The hydraulic drive source 5 includes a hydraulic pump 22, a pump motor 23 that drives the hydraulic pump 22, a filter 24 that is connected to the suction side of the hydraulic pump 22, a check valve 25 that is connected to the discharge side of the hydraulic pump 22, and the check valve. The accumulator 26 is connected to the secondary side of the valve 25, and the above-mentioned logic valve 21 is connected to the secondary side of the check valve 25 via the supply line 27. Further, 28 is a switching valve, and this switching valve 28
The pilot port of the logic valve 21 can be selectively connected to the supply line 27 or the oil tank 3 by switching. The filter 24 is housed inside the oil tank 3. The hydraulic pump 22 may be a variable discharge type pump or a fixed discharge type pump.

On the other hand, the T port of the servo valve 4 is connected to the open / close valve 6
To the oil tank 3 via. This on-off valve 6
If it is switched to the open side, the T port of the servo valve 4 and the oil tank 3 are in communication, and the normal mode is set. It becomes a mode. Further, the T port of the servo valve 4 is connected to the rear oil chamber 2r of the injection cylinder 2 via the logic valve 7.
Connect to. The pilot port of the logic valve 7 is also connected to the rear oil chamber 2r. As a result, the differential circuit 30
Is configured. On the other hand, a relief valve 8 is connected between the front oil chamber 2 f of the injection cylinder 2 and the oil tank 3. As a result, even if a surge pressure is generated in the exhaust oil discharged from the front oil chamber 2f, the discharged oil is returned to the oil tank 3 via the relief valve 8, so the surge pressure is suppressed.

Next, the operation of the hydraulic circuit 1 according to this embodiment will be described. First, the open / close valve 6 is opened, that is, as shown in FIG.
If you switch to the middle and right symbol R, it will be in normal mode,
The T port of the servo valve 4 communicates with the oil tank 3 via the right symbol R of the opening / closing valve 6. In the injection process, first, the switching valve 28 is switched to the left symbol L (same in the differential mode). As a result, the pilot port of the logic valve 21 communicates with the oil tank 3 and the hydraulic drive source 5
The hydraulic oil discharged from the logic valve 21 and the servo valve 4 is
And is supplied to the rear oil chamber 2r of the injection cylinder 2. In the hydraulic drive source 5, the accumulator 26 is in a pressure-accumulated state by driving the hydraulic pump 22. In the injection process, the hydraulic oil is supplied to the rear oil chamber 2r of the injection cylinder 2 and the discharged oil discharged from the front oil chamber 2f is adjusted so that the injection speed of the injection screw 15 is set by the servo valve 4. , The servo valve 4 and the open / close valve 6 are all returned to the oil tank 3 through the right symbol R.

On the other hand, if the on-off valve 6 is closed, that is, if the left symbol L in FIG. Blocked by L. Therefore, in the injection process, the hydraulic oil supplied from the hydraulic drive source 5 is supplied to the rear oil chamber 2r of the injection cylinder 2 via the servo valve 4 and the discharged oil discharged from the front oil chamber 2f is a logic oil. It is supplied to the primary side of the valve 7. Since the primary pressure of the logic valve 7 rises in accordance with the amount of discharged oil, the logic valve 7 is in the open state when the primary pressure reaches or exceeds the added pressure of the secondary pressure and the cracking pressure. The discharged oil that has passed through the logic valve 7 joins the hydraulic oil discharged from the servo valve 4 and is supplied to the rear oil chamber 2r of the injection cylinder 2. Therefore, it is possible to cope with drive control with a large flow rate without increasing the hydraulic oil supply amount from the hydraulic drive source 5.
Higher injection speed, smaller diameter of oil distribution pipe, and prevention of impact pressure can be realized.

Further, during the stop control, the original stop control by the servo valve 4 is executed, but the discharged oil discharged from the front oil chamber 2f of the injection cylinder 2 passes through the servo valve 4 constituting the meter-out circuit. Since it is supplied to the rear oil chamber 2r, the servo valve 4 also serves as a braking circuit. That is, since the discharge oil supplied from the front oil chamber 2f to the rear oil chamber 2r by the differential circuit 30 has a small flow rate throttled by the servo valve 4, sufficient braking is possible.
Therefore, a separate braking circuit can be omitted or simplified, the number of parts in the entire hydraulic circuit 1 can be reduced, cost can be reduced, control can be facilitated and stabilized, and accurate and accurate braking control can be achieved. Can be performed, and the molding quality is dramatically improved. Even if surge pressure is generated during braking control, it is suppressed by the relief valve 8.

On the other hand, when the injection process is completed and the pressure maintaining process is started, the on-off valve 6 is switched to the right symbol R. As a result, the logic valve 7 communicates with the oil tank 3, and the primary side pressure of the logic valve 7 becomes lower than the secondary side pressure, so that the logic valve 7 is closed and the front oil chamber 2f of the injection cylinder 2 is closed. Pressure drops. As a result, a high holding pressure is secured (maintained).

Next, a hydraulic circuit 1s according to a modified embodiment of the present invention will be described with reference to FIG. In the embodiment of FIG. 1, the T port of the servo valve 4 is connected to the rear oil chamber 2r of the injection cylinder 2 via the logic valve 7, but in the modified embodiment, the T port of the servo valve 4 is connected to the logic valve 7 It is connected to the P port of the servo valve 4 via. Therefore, in the modified embodiment, in the differential mode, the oil discharged from the logic valve 7 merges with the hydraulic oil at the P port of the servo valve 4 and then passes through the servo valve 4 to the rear oil chamber 2r of the injection cylinder 2. Supplied. Also in the modified embodiment, the point that the servo valve 4 also serves as the braking circuit is basically the same as the embodiment of FIG. In the modified embodiment, the oil discharged from the logic valve 7 is supplied to the P port of the servo valve 4, and the rear oil chamber 2
Since the flow rate of all the hydraulic oil supplied to r is controlled by the servo valve 4, the braking performance is further improved as compared with the embodiment of FIG. However, in the case of the modified embodiment, since the pressure of the accumulator 26 always acts on the P port of the servo valve 4, the pressure of the accumulator 26 also acts on the secondary side of the logic valve 7 and the pilot port. Therefore, in order to open the logic valve 7 in the injection process, the primary side pressure needs to be equal to or higher than the added pressure of the accumulator 26 and the cracking pressure. The piston moves forward, which is disadvantageous in terms of the durability of the packing and the like as compared with the embodiment of FIG.

Further, in the modified embodiment shown in FIG. 2, an injection manifold 35 in which a part of the hydraulic circuit 1s is surrounded by an imaginary line.
Configured as. With such a configuration, the accumulator 26 can be directly assembled to the injection manifold 35 as shown by the phantom line 26s, and as a result,
It is possible to further reduce the diameter of the oil distribution pipe that connects the hydraulic drive source 5 and the manifold 35.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment (modified embodiment), and the detailed configuration, shape, parts used, etc. can be arbitrarily changed, added, or deleted without departing from the gist of the present invention. For example, the relief valve 8 does not necessarily have to be provided. In the differential mode, the case where all the discharged oil is supplied to the rear oil chamber 2r of the injection cylinder 2 is shown, but the case where a part of the discharged oil is supplied to the rear oil chamber 2r of the injection cylinder 2 is excluded. is not. Furthermore, "connecting" is a concept that includes not only connecting directly to a connection site, but also connecting to an oil distribution pipe connected to the connection site or another site to which this oil distribution pipe is connected. is there.

[0021]

As described above, the hydraulic circuit of the injection molding machine according to the present invention includes the four-port servo valve for driving and controlling the injection cylinder, and the A port and the B port of the servo valve are
Via an on-off valve that connects to the front oil chamber and the rear oil chamber of the injection cylinder, respectively, connects the P port of the servo valve to the hydraulic drive source, and switches the T port of the servo valve to the normal mode or the differential mode. Since it is connected to an oil tank and the T port is connected to the rear oil chamber of the injection cylinder (or the P port of the servo valve) via a logic valve, a separate braking circuit is unnecessary or simplified. It is possible to reduce the number of parts in the entire hydraulic circuit, reduce the cost, facilitate and stabilize the control, and it is possible to dramatically improve the molding quality by performing accurate and accurate braking control. Produce an effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a hydraulic circuit according to a preferred embodiment of the present invention,

FIG. 2 is a configuration diagram of a hydraulic circuit according to a modified embodiment of the present invention,

FIG. 3 is a principle configuration diagram in which a hydraulic circuit according to a conventional technique is simplified,

[Explanation of symbols]

1 hydraulic circuit 1s hydraulic circuit 2 injection cylinder 2f front oil chamber 2r rear oil chamber 3 oil tank 4-port servo valve 5 hydraulic drive source 6 open / close valve 7 logic valve 8 relief valve A servo valve A port B Servo valve B port P Servo valve P port T servo valve T port M injection molding machine

Continuation of the front page (56) Reference JP-A-6-246800 (JP, A) JP-A-5-50483 (JP, A) JP-A-8-150642 (JP, A) JP-A-9-296802 (JP , A) JP-B-41-3214 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) F15B 11/00-11/22 B29C 45/82

Claims (4)

(57) [Claims] 1. A normal mode in which all the exhaust oil discharged from the front oil chamber of the injection cylinder during injection is returned to the oil tank, and a differential mode in which all or part of the exhaust oil is supplied to the rear oil chamber of the injection cylinder. In the hydraulic circuit of the injection molding machine which can select, a four-port servo valve for driving and controlling the injection cylinder is provided, and the A port and the B port of this servo valve are
An on-off valve that connects to the front oil chamber and the rear oil chamber of the injection cylinder, respectively, connects the P port of the servo valve to a hydraulic drive source, and switches the T port of the servo valve to a normal mode or a differential mode. A hydraulic circuit of an injection molding machine, characterized in that the T port is connected to the oil tank via a logic valve and the T port is connected to a rear oil chamber of the injection cylinder via a logic valve. 2. A hydraulic circuit for an injection molding machine according to claim 1, wherein a relief valve is connected between the front oil chamber of the injection cylinder and the oil tank. 3. A normal mode in which all of the discharged oil discharged from the front oil chamber of the injection cylinder during injection is returned to the oil tank, and a differential mode in which all or part of the discharged oil is supplied to the rear oil chamber of the injection cylinder. In the hydraulic circuit of the injection molding machine which can select, a four-port servo valve for driving and controlling the injection cylinder is provided, and the A port and the B port of this servo valve are
An on-off valve that connects to the front oil chamber and the rear oil chamber of the injection cylinder, respectively, connects the P port of the servo valve to a hydraulic drive source, and switches the T port of the servo valve to a normal mode or a differential mode. A hydraulic circuit for an injection molding machine, characterized in that the T port is connected to the oil tank via a logic valve and the T port is connected to the P port via a logic valve. 4. A hydraulic circuit for an injection molding machine according to claim 3, wherein a relief valve is connected between the front oil chamber of the injection cylinder and the oil tank.