JPH1177785A - Hydraulic circuit of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly ensure the stability at the time of the rising of molding by shortening the temp. rise time of operation oil at the time of start of operation and to enhance the production efficiency by providing a heat exchange part between the operation oil of a hydraulic pump and a drive motor. SOLUTION: When operation is started, a power supply is closed and a servo motor 4s is operated to drive a hydraulic pump 3c. When the set temp. of operation oil O is set to 40 deg.C and temp. at the time of start of operation is set to 20 deg.C, an oil cooler 5 is not operated at an operation initial period and, therefore, the operation oil O circulated through the circuit of a hydraulic drive source 2 is heated by the heat generated in the hydraulic pump 3 and also heated by the heat generated by the servo motor 48. That is, the heat generated by the servo motor 4S is transmitted to an oil sending pipe (heat exchange part 6) wound around the servo motor 4S and the operation oil O flowing through the oil sending pipe is heated by heat exchange.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for an injection molding machine having a hydraulic pump as a hydraulic drive source and a drive motor for driving the hydraulic pump.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic circuit of an injection molding machine, a fixed discharge hydraulic pump and a servomotor for driving the hydraulic pump are used as a hydraulic drive source, and the number of rotations of the servomotor is controlled to control the hydraulic pump. There is known a hydraulic circuit which controls a discharge flow rate and a discharge pressure.

In this type of hydraulic circuit, it is important to maintain the temperature of the circulating hydraulic oil at an appropriate temperature in order to secure the optimum viscosity of the hydraulic oil and ensure smooth operation of the hydraulic actuator. Since the optimal temperature of hydraulic oil is usually around 40 ° C, the circulating hydraulic oil is heated at the beginning of operation using heat generated by a hydraulic pump etc., and when the temperature reaches around 40 ° C, an oil cooler Control is performed to cool and maintain the set temperature during operation. on the other hand,
Since the servomotor generates heat due to copper loss of the coil during operation, cooling by an air cooling system is usually performed by a cooling fan attached to the motor shaft.

[0004]

However, the above-mentioned conventional hydraulic circuit has the following problems.

First, in winter or the like, it takes a considerable time from the start of operation to a proper temperature of the hydraulic oil due to a decrease in the temperature of the hydraulic oil. FIG. 3 shows, as an example, the relationship between the operating oil temperature and the servo motor temperature with respect to the operation elapsed time in the conventional hydraulic circuit by using Tor (operating oil temperature) and Tmr (servo motor temperature). in the case of,
It takes about 30 minutes for the hydraulic oil temperature Tor to reach an appropriate temperature. During this time, stable molding cannot be performed and production efficiency is reduced.

Second, the servomotor is cooled by an air cooling method. However, if the power consumption of the servomotor is increased due to an increase in the molding cycle speed, the servomotor cannot be cooled sufficiently, as shown by Tmr in FIG. In addition, heat generation becomes large, and a control error due to a temperature drift is likely to occur. In addition, dust and the like are easily generated by the wind generated by the cooling fan, which is not preferable for an injection molding machine or a molded product.

The present invention has been made to solve the problems existing in the prior art, and shortens the time for raising the temperature of the hydraulic oil at the start of operation to quickly secure the stability at the time of starting the molding. It is an object of the present invention to provide a hydraulic circuit of an injection molding machine that improves production efficiency and simultaneously eliminates a cooling fan in a drive motor (servo motor) and ensures sufficient cooling.

[0008]

The present invention comprises a hydraulic pump 3 as a hydraulic drive source 2 and a drive motor 4 for driving the hydraulic pump 3, and also a hydraulic oil O circulated by the hydraulic pump 3. In configuring the hydraulic circuit 1 of the injection molding machine including the oil cooler 5 for cooling, a heat exchange unit 6 for exchanging heat between the hydraulic oil O and the drive motor 4 is provided between the hydraulic oil O and the drive motor 4. It is characterized by the following.

In this case, according to a preferred embodiment, the heat exchange section 6 can be configured by winding an oil feed pipe 10 through which the hydraulic oil O circulates around the outer surface of the drive motor 4. The temperature of O is detected, and when the detected temperature is equal to or lower than the set value, the hydraulic oil O is caused to flow to the heat exchange unit 6.
A bypass function unit 11 can be provided to bypass and flow. Further, the heat exchange section 6 can be constituted by a heat transfer section 13 between the oil tank 12 containing the hydraulic oil O and the drive motor 4. On the other hand, the hydraulic drive source 2 can be constituted by a fixed discharge hydraulic pump 3c and a servo motor 4s for driving the hydraulic pump 3c.

As a result, since the heat exchanging section 6 is interposed between the hydraulic oil O and the drive motor 4, when the temperature of the hydraulic oil O is low at the start of the operation of the injection molding machine, the hydraulic pump 3 or the like is used. In addition to being heated by the generated heat, it is also heated by the heat generated by the drive motor 4, so that the time required for the hydraulic oil O to reach an appropriate temperature (set temperature) is reduced. On the other hand, after the working oil O reaches an appropriate temperature, the cooling is controlled by the oil cooler 5 so as to reach the set temperature, so that the drive motor 4 is cooled by the oil cooling method using the working oil O.

[0011]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the configuration of the hydraulic circuit 1 according to the first embodiment will be described with reference to FIGS.

In FIG. 1, M is an injection molding machine, which includes an injection device M1 and a mold clamping device M2. On the other hand, in the hydraulic circuit 1, reference numeral 21 denotes a hydraulic panel including various control valves and the like, and various hydraulic actuators of the injection molding machine M are connected to the hydraulic panel 21. In the embodiment, the hydraulic panel 21 is used.
Injection device M1 as a hydraulic actuator connected to
Injection cylinder 22 and mold clamping cylinder 2 of mold clamping device M2
3 is illustrated.

Reference numeral 2 denotes a hydraulic drive source, which includes a fixed discharge hydraulic pump 3c (hydraulic pump 3) and a hydraulic pump 3c.
c is provided with a servomotor 4s (drive motor 4) for driving c. The hydraulic drive source 2 can control the discharge flow rate and discharge pressure of the hydraulic pump 3c by controlling the rotation speed of the servo motor 4s. The discharge port 3o of the hydraulic pump 3c is connected to the supply port 21i of the hydraulic panel 21, and the suction port 3i of the hydraulic pump 3c is connected to the oil tank 24. Thereby, the hydraulic oil O discharged from the hydraulic pump 3c is supplied to the hydraulic actuator of the injection molding machine M through the supply port 21i of the hydraulic panel 21.

On the other hand, the hydraulic panel 21 is provided with a discharge port 21o for discharging the hydraulic oil O returned from the hydraulic actuator of the injection molding machine M. This discharge port 21o is connected to the heat exchange section 6 attached to the servomotor 4s according to the present invention. To the inlet port 5i of the oil cooler 5. In this case, as shown in FIG. 2, the heat exchange unit 6 winds the oil supply pipe 10 connecting the discharge port 21o of the hydraulic panel 21 and the inlet port 5i of the oil cooler 5 so as to be in close contact with the outer surface of the servomotor 4s. It is composed. The outlet port 5o of the oil cooler 5 is connected to the oil tank 24. In addition,
25 is a case drain (external drain) connected between the hydraulic pump 3c and the oil cooler 5, 26 is a servo motor 4
s shows the motor shaft.

Next, the operation of the hydraulic circuit 1 according to the first embodiment will be described with reference to FIGS.

Now, in a relatively cold temperature environment, the injection molding machine M
It is assumed that the operation is started. First, when the power is turned on, the servo motor 4s operates to drive the hydraulic pump 3c. Thus, the hydraulic oil O of the oil tank 24 is sucked into the hydraulic pump 3c from the suction port 3i, and the hydraulic oil O is discharged from the discharge port 3o of the hydraulic pump 3c.
Is supplied to the supply port 21i. On the other hand, the injection molding machine M
Is stopped, the hydraulic oil O supplied to the supply port 21i of the hydraulic panel 21 is discharged (relief) from the discharge port 21o and passes through the oil feed pipe 10 having the heat exchange unit 6 and the oil cooler 5. And returned to the oil tank 24.

At this time, as an example, assuming that the set temperature of the hydraulic oil O is 40 ° C. and the temperature at the start of the operation is 20 ° C., the oil cooler 5 does not operate at the beginning of the operation. The hydraulic oil O circulating in the circuit is supplied to the hydraulic pump 3
And the like, and also heated by the heat generated by the servo motor 4s. That is, the heat generated by the servo motor 4s
Is transmitted to the oil feed pipe 10 (heat exchange section 6) wound around
The hydraulic oil O flowing through the oil pipe 10 is heated by heat exchange. FIG. 3 shows the relationship between the operating oil temperature To and the servo motor temperature Tm with respect to the operation elapsed time. As shown in FIG.
By providing the heat exchange section 6, the time required for the operating oil O to reach a set temperature (40 ° C.) at which the operating oil O reaches an appropriate temperature is reduced. In the case of the hydraulic oil temperature To shown in the embodiment, the heating time is 2
It takes about 0 minutes, and the conventional technology (T
or) about 10 minutes. Therefore, stability at the time of starting the molding is promptly secured, and the production efficiency is improved.

On the other hand, when the operating oil temperature To rises and reaches the set temperature (40 ° C.), the oil cooler 5 operates based on the detection by a temperature sensor (not shown), and the operating oil O is cooled. . That is, feedback control is performed so that the hydraulic oil temperature To maintains the set temperature. Further, the hydraulic oil O maintained at the set temperature is supplied to the oil supply pipe 10 constituting the heat exchange unit 6.
Then, the servomotor 4s is cooled by the oil cooling method using the heat exchange unit 6, and as shown by Tm in FIG. 3, sufficient and stable cooling is ensured, thereby reducing the control error due to temperature drift. Is done. In addition, since a cooling fan is not required, dust and the like are not generated by the cooling fan, and the cost is also advantageous.

FIGS. 4 and 5 show a second embodiment. 4 and FIG. 5 are denoted by the same reference numerals as those in FIG. 1 and FIG. 2 to clarify the configuration of each part and omit detailed description thereof.

In the second embodiment, the heat exchange section 6 is constituted by an oil tank 12 containing hydraulic oil O and a heat transfer portion 13 between the servomotor 4s (drive motor 4). That is, the side portion 12s of the oil tank 12
An accommodation recess 31 for accommodating the servo motor 4s was provided in the housing, and the servo motor 4s was accommodated in the accommodation recess 31. Therefore, the wall surface of the housing recess 31 becomes the heat transfer portion 13.
In the case of the second embodiment, the discharge port 2 of the hydraulic panel 21
The oil cooler 5 is directly connected to the oil cooler 5 by an oil feed pipe 10. The basic operation and operation are the same as in the first embodiment.

FIG. 6 shows a modification of the first embodiment shown in FIG. In this modified example, a bypass function unit 11 is added to the heat exchange unit 6. The bypass function unit 11 detects the temperature of the hydraulic oil O by the temperature sensor 41, and when the detected temperature is equal to or lower than the set value, switches the three-way switching valve 42 to one side to transfer the hydraulic oil O to the heat exchange unit 6. When the detected temperature exceeds the set value, the three-way switching valve 42 is switched to the other side to pass the hydraulic oil O to the bypass pipe 4.
3 and has a function of bypassing the heat exchange unit 6.
In such a modification, the operating oil is heated by the servomotor at the start of operation, but the servomotor is not cooled by the operating oil. Therefore, the present invention can be applied to a case where a servomotor which generates heat but does not require cooling, that is, a servomotor of a natural cooling system is used.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
The configuration, shape, etc. of the details can be arbitrarily changed, added, or deleted without departing from the gist of the present invention.
For example, the case where the hydraulic drive source 2 includes the fixed discharge type hydraulic pump 3c and the servomotor 4s for driving the hydraulic pump 3c has been described, but a variable discharge type hydraulic pump is used for the hydraulic pump 3 and the drive motor 4 is The same applies to the case where a general motor that rotates at a constant speed is used. Further, in the second embodiment, the servo motor 4s may be subjected to oil resistance treatment and may be housed directly in the oil tank 12 so that only the motor shaft 26 is exposed to the outside of the oil tank 12.

[0024]

As described above, the hydraulic circuit of the injection molding machine according to the present invention includes a heat exchange section for exchanging heat between the hydraulic oil and the drive motor between the hydraulic oil circulated by the hydraulic pump and the drive motor. Due to the provision, the following remarkable effects are exhibited.

Since the time for raising the temperature of the hydraulic oil in the initial stage of the operation can be shortened, stability at the time of starting the molding can be promptly secured, and the production efficiency can be improved.

[0026] Sufficient and stable cooling of the drive motor is ensured, control errors due to temperature drift are reduced, and at the same time, a cooling fan can be dispensed with, so that dust and the like are not generated by the cooling fan, and the cost is also advantageous. become.

The operation can be performed easily and at low cost without using any additional components.

[Brief description of the drawings]

FIG. 1 is a block diagram of an injection molding machine including a block diagram of a hydraulic circuit according to a first embodiment of the present invention;

FIG. 2 is a partial cross-sectional configuration diagram of a heat exchange unit provided in the hydraulic circuit,

FIG. 3 is a characteristic diagram showing a relationship between a hydraulic oil temperature and a servo motor temperature with respect to an operation elapsed time in the hydraulic circuit;

FIG. 4 is a block diagram of a hydraulic circuit according to a second embodiment of the present invention,

FIG. 5 is a sectional configuration diagram of a heat exchange unit provided in the hydraulic circuit,

FIG. 6 is a block diagram of a hydraulic circuit according to a modification of the first embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic circuit 2 Hydraulic drive source 3 Hydraulic pump 3c Fixed discharge type hydraulic pump 4 Drive motor 4s Servo motor 5 Oil cooler 6 Heat exchange part 10 Oil supply pipe 11 Bypass function part 12 Oil tank 13 Heat transfer part O Hydraulic oil

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[Procedure amendment]

[Submission date] October 20, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

Claims (5)

[Claims] 1. A hydraulic circuit for an injection molding machine, comprising: a hydraulic pump as a hydraulic drive source; a drive motor for driving the hydraulic pump; and an oil cooler for cooling hydraulic oil circulated by the hydraulic pump. A heat exchange section for exchanging heat between the hydraulic oil and the drive motor is provided between the hydraulic motor and the drive motor. 2. The hydraulic circuit for an injection molding machine according to claim 1, wherein the heat exchange unit is configured by winding an oil feed pipe through which the hydraulic oil circulates around an outer surface of the drive motor. 3. The temperature of the hydraulic oil is detected, and when the detected temperature is equal to or lower than a set value, the hydraulic oil is caused to flow through the heat exchange unit. When the detected temperature exceeds a set value, the hydraulic oil is set. 3. A hydraulic circuit for an injection molding machine according to claim 2, further comprising: a bypass function section for causing the heat to flow by bypassing the heat exchange section. 4. A hydraulic circuit for an injection molding machine according to claim 1, wherein said heat exchange section comprises a heat transfer portion between an oil tank containing said hydraulic oil and said drive motor. 5. The hydraulic circuit for an injection molding machine according to claim 1, wherein said hydraulic drive source comprises a fixed discharge hydraulic pump and a servomotor for driving said hydraulic pump.