JP2003013906A - Electro-hydraulic actuator for forging press, caulking press or the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an electro-hydraulic pump unit which delivers constant rated pressure with the use of one hydraulic pump is inefficient and high in power consumption for use in a caulking press or forging press or the like which requires two hydraulic pressure energy use patterns; one pattern is large delivery rate and low pressure, and the other pattern is small delivery rate and high pressure. SOLUTION: A large delivery rate and low pressure hydraulic pump and a small delivery rate and high pressure hydraulic pump are coupled with one servo-motor by which two hydraulic pumps jointly deliver hydraulic pressure energy in the phase of large delivery rate and low pressure, while the small delivery rate and high pressure hydraulic pump alone delivers the hydraulic energy in the phase of small delivery rate and high pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric / mechanical energy conversion system that uses electricity as an energy source and outputs mechanical energy by an actuator such as a hydraulic cylinder or a hydraulic rotary actuator. More specifically, it is of a hydraulic type. The present invention relates to a hydraulic machine whose main application area is an impact type press that requires a huge force at the moment of processing, such as a caulking press and a cold forging press.

[0002]

2. Description of the Related Art In a conventional hydraulic press, hydraulic energy of a constant pressure is supplied from an electric hydraulic pump unit that uses an induction motor that rotates at a rated speed at a commercial frequency as a prime mover, and a hydraulic energy supply direction is supplied by an electromagnetic valve or the like. The supply flow rate was controlled to control the moving direction, moving speed, generated force, etc. of the actuator.

[0003]

The conventional electric hydraulic pump unit achieves high electric-mechanical energy conversion efficiency (hereinafter referred to as efficiency) near the rated output, but the output flow rate becomes zero when there is no load. Even about 80% of the rated input
Consumes electricity. This power consumed at no load is
It consists of the internal loss of the electric hydraulic pump and the hydraulic energy discharge loss by the relief valve for keeping the pressure of the hydraulic oil at a constant value. Recently, an electric hydraulic pump unit using a hydraulic pump driven by a servo motor has appeared on the market. However, this is also the fate of the electric hydraulic pump unit, and the rated pressure must be maintained so that full power can be output at any time. Therefore, the power consumption at the time of holding pressure when the output flow rate is zero is about 50% of the rated output, and although it has been improved considerably, it is not technically satisfactory.

As described above, if the actuator is used at an output flow rate in a region close to the rated output such as a period during which the actuator is processing a work, this system exhibits high efficiency, but the output flow rate becomes zero. During standby, or during periods before or after machining, when the actuator performs only movement movements and the required force is small, this system can show zero or extremely low efficiency.

For this reason, the electric hydraulic pump unit according to the prior art can achieve high efficiency in applications where the actuator is continuously operated at full load, but most of the period during operation is no load or low load. The application can achieve significantly lower efficiencies.

Examples of such low efficiency applications are:
This is the case with a caulking press, a cold forging press, etc. The electric hydraulic pumps of these machines require high efficiency and maximum output only for a short period of time, which is the moment after the mold comes into contact with the work. The rest of the period consists of moving the machine, including the mold, which has a light load with extremely low efficiency, and picking up, mounting, and waiting for a workpiece at no load, which has no efficiency. Comparing the mechanical energy required for moving the machine and machining the workpiece with the electrical energy consumed by the electric hydraulic pump unit, its efficiency reaches only a few percent. Today, with environmental issues being addressed on a global scale, it is unacceptable to operate machines with such low efficiency. The present invention solves this problem as follows.

[0007]

According to the present invention, one hydraulic motor drives two hydraulic pumps, a large hydraulic pump and a small hydraulic pump.

During the period when the actuator is stopped, the power supply to the servo motor is stopped and the hydraulic pump is stopped. The servo motor consumes no energy, and the control device including the inverter that supplies electric power to the servo motor also needs only a small amount of power such as standby power. The pressure of the hydraulic oil at this time is zero.

Before and after the actuator is machined, the two hydraulic pumps cooperate to send hydraulic oil to move the actuator while the machine including the mold is moving under a light load. At this time, the pressure of the hydraulic oil is low and the flow rate is large. Since the mechanical input required by the hydraulic pump is the product of the pressure and flow rate of the hydraulic oil, the mechanical output or power consumption of the servomotor that drives it is low.

Immediately before or immediately after the die approaches the workpiece and contact is started in the period before processing, the hydraulic pump with a large flow rate is disconnected from the hydraulic circuit on the pushing side of the actuator by an electromagnetic valve or the like to be in an unloading operation state. After that, only the hydraulic pump with a small flow rate is driven by the servo motor. The product of the rotational speed of the servomotor and the output torque is equal to the mechanical input of the hydraulic pump, and is equal to the product of the flow rate V and the pressure P of the hydraulic oil, which is the mechanical output of the hydraulic pump, plus internal loss.
Now, let's assume that the flow rate of the large flow rate hydraulic pump is 3V and the flow rate of the small flow rate hydraulic pump is 1V. The flow rate that the two hydraulic pumps send together is 4V, and the pressure that can be generated at this time is 1P. If the mold processes the work while the two hydraulic pumps are operating in parallel, the available pressure is 1P. However, when the hydraulic pump with a large flow rate is disconnected and no load is applied, and the die processes the work with only the hydraulic pump with a small flow rate, the output torque of the servo motor can be generated because it is centrally supplied to the hydraulic pump with a small flow rate. The pressure rises to 4P.

As described above, according to the hydraulic circuit configuration and the operation mode according to the present invention, the machine including the mold before or after the processing has a slight load, and the period in which the machine should move rapidly is 2 The hydraulic pumps of the units work together to deliver low pressure, high flow hydraulic oil. This period corresponds to a period during which the hydraulic pump unit according to the related art consumes almost 100% of the rated electric power and delivers the hydraulic oil of the rated flow rate. On the other hand, in the system according to the present invention, even if the flow rate of the hydraulic oil is the same during this period, the required pressure is considerably low, so that the power consumption of the servo motor is considerably small.

Further, according to the hydraulic circuit configuration and the operation mode according to the present invention, only one hydraulic pump having a small flow rate delivers the hydraulic oil having a high pressure and a small flow rate during the machining of the work by the die. In this period, the hydraulic pump unit of the related art outputs only a small flow rate required by the actuator, but the power corresponds to a period in which a value close to the rated power is consumed. On the other hand, in the system according to the present invention, the pressure of the hydraulic oil during this period is as high as the rated pressure of the prior art, but the flow rate is as small as required by the actuator. The power is extremely small.

In the above-mentioned application example, the processing time is a short time which should be called an instant, and the pressure generated by the small flow rate hydraulic pump is not only due to the torque supplied from the servo motor, but also at the moment when the die pushes out the work. Is a form in which the hydraulic pump pushes out the hydraulic oil because the actuator stops rapidly, and the servo motor and hydraulic pump are stopped in a short period of time, causing the moment of inertia to generate surge torque, which is driven by this surge torque. Since the hydraulic pump generates a surge pressure in the hydraulic oil, it is possible to supply a high pressure, which cannot be supplied by the hydraulic pump unit of the related art, as a processing force for a short time. This is a point to be careful when using the method according to the present invention. That is, since a momentary high pressure can be used as a processing force, there is an advantage that the shape and size of the die can be copied more accurately than the conventional hydraulic press. A processing field in which this advantage can be effectively utilized is, for example, caulking, and cold forging with a processing stroke of several millimeters. Even with the same cold forging, if the processing stroke is several centimeters, it cannot be processed with a short surge pressure. Despite these advantages, there is also the danger that surge pressure may violently damage the hydraulic circuit or machine body. Therefore, when the method according to the present invention is used, it is required to be familiar with its character and use it in a safe range. It is also conceivable to apply safety valves in order not to exceed dangerous pressure limits much higher than the rated pressure.

In the above description, according to the method of the present invention, the electric hydraulic pump unit of the prior art is used both during the moving operation of the machine including the mold before and after machining and during the machining of the work by the mold. In contrast, the power consumption of the servo motor was considerably small. Naturally, the mechanical output capacity of the servomotor and the electrical output capacity of the control device including the inverter supplying the electric power to the servomotor may be smaller than those of the electric hydraulic pump unit according to the related art. The ratio depends on the operation mode, but is about one half to one third.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Three examples of the embodiment for realizing the above-described operation mode according to the present invention will be described below.

[0016]

1 is an electric circuit / hydraulic circuit diagram showing a first embodiment of the present invention. A large flow hydraulic pump 12 and a small flow hydraulic pump 13 are connected to the servomotor 5.
The hydraulic pump 12 is connected to a 3-port solenoid valve 14, and is connected to the push side hydraulic circuit 8 to send hydraulic oil toward the hydraulic cylinder 1 in the normal position and connected to the pull side hydraulic circuit 7 in the operating position. It becomes unloading operation.

Now, in the period after processing, the 3-port solenoid valve 1
4 is a normal position, the servomotor 5 is rotated in the reverse direction, and the two hydraulic pumps 12 and 13 cooperate to suck the hydraulic oil from the push side hydraulic circuit 8 and send it to the pull side hydraulic circuit 7 for hydraulic pressure. The cylinder 1 pulls at a high moving speed. Next, in the period before processing, the 3-port solenoid valve 14 is in the normal position, the servo motor 5 rotates forward, and the two hydraulic pumps 12 and 13 cooperate to suck the hydraulic oil from the pull-side hydraulic circuit 7. The hydraulic cylinder 1 is sent to the push side hydraulic circuit 8 to perform the pushing operation at a high moving speed. When the position detector 3 installed in the hydraulic cylinder 1 transmits the position information indicating that the position detector 3 has reached a predetermined position, the control device 4 that receives the position information receives the position information.
4, a control voltage is applied to move to the operating position, the large flow rate hydraulic pump 12 is disconnected from the push side hydraulic circuit and the unloading operation is started, and the small flow rate hydraulic pump 13 independently applies the necessary high pressure to the push side hydraulic circuit. 8 to raise the hydraulic pressure to a predetermined pressure. During this time, the pressure detector 9 transmits the pressure information of the push side hydraulic circuit 8, and the control device 4 which receives the pressure information supplies the voltage to the servo motor 5 so that the small flow hydraulic pump 13 can supply the set pressure. Frequency feedback control.

Although the three-port solenoid valve is used in the first embodiment, the function described in the method for solving the problem can be realized by a combination of solenoid valves other than the three-port solenoid valve. These can be easily devised, and the present invention is not limited to the examples given here.
The 2-port manual switching valve shown in FIG. 1 is provided for safety so that the cylinder will not drop when stopped.
It is not an essential element of the present invention.

In the second embodiment shown in FIG. 1, when the machining period is entered from the period before machining, the die comes into contact with the work, the hydraulic cylinder is rapidly decelerated, and the pressure of the hydraulic oil is rapidly increased. Is detected by the control device 4 due to a sudden change in pressure information transmitted by the pressure detector 3, and the 3-port solenoid valve 14 is detected.
A control voltage is applied to the valve to move it to the operating position, the large flow rate hydraulic pump 12 is disconnected from the push side hydraulic circuit 8 and unloading is performed, and the small flow rate hydraulic pump 13 independently sends out high pressure hydraulic oil. .

FIG. 2 shows a third embodiment. In the first and second embodiments, the solenoid valve is operated by the information transmitted from the position detector 3 and the pressure detector 9, but in the third embodiment, the large flow rate hydraulic pump 12 is operated when the predetermined pressure is reached. A hydraulically operated three-port variable throttle valve 17 is used which is separated from the push side hydraulic circuit 8 and enters the unloading operation. The operating pressure of the 3-port variable throttle valve 17 is set low, for example, one third of the rated pressure. If the pressure of the push side hydraulic circuit 8 rises rapidly due to the hydraulic oil that is sent even when the hydraulic cylinder 1 is stopped due to the die coming into contact with the workpiece and entering the processing period, the 3-port variable throttle valve will move to the normal position. To the operating position, the large flow rate hydraulic pump 12 enters the unloading operation, and thereafter, the small flow rate hydraulic pump 13 performs processing.

[0021]

Since the present invention is constructed as described above, it has the following effects.

In the application where the hydraulic energy use pattern has two patterns of large flow rate / low pressure and small flow rate / high pressure, when the hydraulic system according to the present invention is applied, compared with the case of using the hydraulic pump unit of the prior art. Thus, the electrical output of the control device and the mechanical output of the servomotor can be reduced to about 1/2 to 1/3.

Further, according to the present invention, it is possible to reduce the size and weight of the device and reduce the cost.

Further, according to the method of the present invention, by positively utilizing the surge pressure generated at the moment of machining, it is possible to obtain a hydraulic machine having a higher machining force on the same scale.

Further, according to the present invention, it is possible to significantly save energy as compared with the prior art for the same work content.

[Brief description of drawings]

FIG. 1 is an electric circuit / hydraulic circuit diagram of an embodiment corresponding to claim 1 and claim 2 of the present invention.

FIG. 2 is an electric circuit / hydraulic circuit diagram of an embodiment corresponding to claim 3 of the present invention.

[Explanation of symbols]

1 hydraulic cylinder 2 output shaft 3 position detector 4 control device 5 Servo motor 6 hydraulic pump 7 Pulling side hydraulic circuit 8 Push side hydraulic circuit 9 Pressure detector 10 Low pressure priority shuttle valve 11 oil tank 12 Large flow hydraulic pump 13 Small flow hydraulic pump 14 3-port solenoid valve 17 3-port variable throttle valve 20 2-port manual switching valve

Claims (3)

[Claims] 1. A device for use in an application in which the force required only by moving in most of one operation cycle is slight and the maximum force is required to be generated only in a limited short period. The actuator that generates is not supplied with hydraulic energy from the hydraulic pump unit that supplies a constant pressure, but two hydraulic pumps, one with a large flow rate and the other with a small flow rate, are connected to one servomotor. During the period when the required force is small, the two hydraulic pumps cooperate to send hydraulic oil to the actuator, and when the period when the maximum force is required approaches, the position of the actuator operating part is changed. When it is detected by the detection device, the hydraulic circuit is switched by the electromagnetic switching valve and the hydraulic pump with a large flow rate stops the delivery of hydraulic oil to the actuator. An electro-hydraulic actuator that is controlled so that only the hydraulic pump with a small flow rate delivers hydraulic fluid to the actuator during the period in which it is mechanically unloaded and the maximum force is required. 2. The above-mentioned force is used for an application in which the force required only by moving in most of one operation cycle is small and the maximum force is required to be generated only in a limited short period. The actuator that generates is not supplied with hydraulic energy from the hydraulic pump unit that supplies a constant pressure, but two hydraulic pumps, one with a large flow rate and the other with a small flow rate, are connected to one servomotor. During the period when the required force is small, the two hydraulic pumps work together to deliver hydraulic oil to the actuator, and the period when the maximum force is required has arrived and the hydraulic pressure has sharply increased. When the hydraulic pressure is detected by the pressure sensor, the hydraulic circuit is switched by the electromagnetic switching valve, and the hydraulic pump with a large flow rate stops sending hydraulic oil to the actuator and stops The electro-hydraulic actuator is controlled so that only the hydraulic pump with a small flow rate delivers hydraulic oil to the actuator during the period in which the maximum force is required, because it is in a no-load state. 3. The method according to claim 1, wherein the force required only by moving in most of one operation cycle is small and the maximum force is required to be generated only in a limited short period. The actuator that generates is not supplied with hydraulic energy from the hydraulic pump unit that supplies a constant pressure, but two hydraulic pumps, one with a large flow rate and the other with a small flow rate, are connected to one servomotor. During the period when the required force is small, the two hydraulic pumps cooperate to send hydraulic oil to the actuator, and the period when the maximum force is required comes and the hydraulic pressure exceeds the set pressure. When it rises, the hydraulic circuit is switched mechanically by pressure to switch the hydraulic circuit, and the hydraulic pump with a large flow rate stops the delivery of hydraulic oil to the actuator and stops The electro-hydraulic actuator is controlled so that only the hydraulic pump with a small flow rate delivers hydraulic oil to the actuator during the period in which the maximum force is required, because it is in a no-load state.