KR100498597B1 - Energy curtailment type pressure unit - Google Patents

Abstract

The present invention provides an energy saving hydraulic unit including a hydraulic cylinder that generates mechanical energy by a high pressure generated from oil conveyed through a pipe, comprising: an oil tank for storing the oil; A controller configured to generate a hydraulic control signal by receiving power applied from the outside; A variable speed switched redundancy motor operative in response to a hydraulic control signal from said controller; A fixed displacement pump for transferring oil in the oil tank through the pipe in response to an output signal from the variable speed switched reduction motor, wherein the controller is configured to control the variable speed switched reduction motor of the hydraulic cylinder at a compensating pressure of the hydraulic cylinder. It is characterized in that the rotation speed is lowered and the rotation speed of the variable speed switched reduction motor is increased during operation of the hydraulic cylinder.

Description

Energy Saving Hydraulic Unit {ENERGY CURTAILMENT TYPE PRESSURE UNIT}

The present invention relates to a hydraulic unit for saving energy, and more particularly, to a hydraulic unit for reducing energy by lowering the number of motor revolutions in a holding pressure state in which a hydraulic cylinder maintains pressure.

Recently, in response to the global environmental problem, which is a social demand, the war on energy saving of factories is actively being promoted. Among them, the interest in the power consumption of the hydraulic unit widely used in the production site is increasing rapidly.

In general, a hydraulic unit supplies a high pressure through an oil and operates a cylinder at the pressure. The hydraulic unit presses and fixes or moves a work. Specifically, the hydraulic unit is used for various purposes, such as operating a hydraulic cylinder to move a heavy object, lift, or perform a clamping operation of a workpiece by the hydraulic cylinder. However, in most machining plants, 25% to 30% of the power consumed is generated by the hydraulic unit.

Moreover, conventional hydraulic units suffer from the problem that the same power is always wasted, even when the machine is running, even when in standby.

1 is a view schematically showing a conventional hydraulic unit.

As shown in FIG. 1, the conventional hydraulic unit is composed of a hydraulic cylinder 2, a control valve 4, an oil tank 6, a variable displacement piston pump 8 and a constant speed induction motor 10.

The hydraulic cylinder 2 is an actuator that converts fluid energy into mechanical work. The control valve 4 controls the size, speed and direction of work and transfers oil to the hydraulic cylinder 2 through the pipe. The oil tank 6 prevents the temperature rise of the oil in addition to storing the oil which is the working oil of the hydraulic cylinder 2, prevents the temperature rise of the oil by releasing the generated heat, and prevents air bubbles from being sucked into the pump. Play a role. The variable displacement piston pump 8 refers to a pump in which the discharge flow rate of the pump also changes when the pressure by the load changes even if the rotational speed of the motor is constant. When the pressure increases, the flow rate decreases, and when the pressure decreases, the flow rate increases. The constant speed induction motor 10 is a motor that rotates at an almost constant speed according to the torque of the power source frequency and the load.

When electric power is supplied to the hydraulic unit as described above, all the components are in a ready state and the variable displacement piston pump 6 is rotated by the constant speed of the constant speed induction motor 10. The variable displacement piston pump 6 operates at the same speed as the speed of the constant speed induction motor 10 to supply oil into the pipe. The oil in the pipe is controlled by the control valve 4 in the size, speed, direction, etc. of the work, and the controlled oil flows into the hydraulic cylinder 2 and is converted into mechanical energy.

The pressing force generated in the hydraulic cylinder 2 is controlled by adjusting the discharge amount of oil by changing the angle (not shown) of the swash plate installed inside the variable displacement piston pump 8. For example, when the angle of the swash plate is maximum, the discharge amount is 15 cm 3 per revolution, and when the angle is the minimum, the discharge amount is 2 cm 2. In addition, since the constant speed induction motor 10, the rotation speed is always constant at 1800rpm. Therefore, the rotation speed of the constant speed induction motor 10 is the same even when the cylinder is driven by the piston and when the piston is not driven (ie, when pressure remains in the hydraulic cylinder).

However, at the compensating pressure, only the piston in the hydraulic cylinder 2 maintains a substantially constant position, and the discharge amount of oil is reduced to about 2 cm 3, which is the minimum. That is, at the compensating pressure, the angle of the swash plate of the variable displacement piston pump 8 is reduced to reduce the flow rate of the oil. At this time, the efficiency of the variable displacement piston pump 8 is reduced. The reason is that friction and stirring loss in the hydraulic cylinder are not reduced even though the flow rate is not working. As a result, the conventional hydraulic unit is configured to rotate the constant speed induction motor 10 at a high speed even when unnecessary, such as compensation pressure. This means that the swash plate is set in the angular region that reduces efficiency, and is used for holding pressure, which takes up most of the motion. Therefore, there is a problem that the power consumption of the hydraulic unit is increased by these results.

For reference, a number of applications have been made in connection with swash plate variable displacement piston pumps. For example, the publication "Variable displacement mechanism of a swash plate hydraulic pump and a motor" of the publication number 1996-014656 discloses the formation of an installation hole of a fixing pin for preventing the interlocking rotation of the swash plate.

In addition, the designation "control device of a variable displacement hydraulic pump" of the publication number 1993-010389 has a horsepower control pressure piston which is displaced in response to the discharge pressure of the pump and a pressure control piston which is displaced in response to the external command pressure. Disclosed is a configuration in which a set of opposing springs 13a and 13b are displaced by a sum of a horsepower control discharge pressure and a flow control command pressure.

An object of the present invention for solving the above problems is to provide a hydraulic unit in which power consumption is reduced.

Another object of the present invention is to provide a hydraulic unit in which friction or stirring loss is minimized.

It is another object of the present invention to provide a hydraulic unit in which the deterioration of hydraulic fluid is minimized.

 According to the technical idea of the present invention for achieving the above object, in the energy-saving hydraulic unit including a hydraulic cylinder for generating mechanical energy by the high pressure generated from the oil conveyed through the pipe, the oil is stored An oil tank; A controller configured to generate a hydraulic control signal by receiving power applied from the outside; A variable speed switched reluctance motor operating in response to the hydraulic control signal from the controller; And a fixed displacement pump for transferring oil in the oil tank through the pipe in response to an output signal from the variable speed switched reluctance motor, wherein the controller is configured to control the variable speed switched reluctance motor at a compensation pressure of the hydraulic cylinder. A hydraulic unit is provided, wherein the rotation speed is lowered and the rotation speed of the variable speed switched reluctance motor is increased during operation of the hydraulic cylinder.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described.

As shown in FIG. 2, the hydraulic unit according to the present invention includes a hydraulic cylinder 2, a control valve 4, an oil tank 6, a variable speed switched reluctance motor 12, a fixed displacement pump 14, a controller ( 20). That is, according to the core technology of the present invention, the controller 20 determines whether the hydraulic cylinder 2 is in a compensating pressure state in which it does not operate substantially or in an operating state in which it operates substantially such as clamping. Subsequently, the controller 20 lowers the rotation speed of the variable speed switched reluctance motor 12 at the compensating pressure of the hydraulic cylinder 2, and rotates the variable speed switched reluctance motor 12 during the operation of the hydraulic cylinder 2. Increase the number

A more detailed description thereof will be described with reference to FIG. 3. 3 is a more detailed view of FIG. 2 presented herein.

The hydraulic unit according to the present invention largely comprises a hydraulic cylinder 2, a control valve 4, an oil tank 6, a variable speed switched reluctance motor 12, a fixed displacement pump 14, a controller 20. In more detail, the oil tank 6 includes a fin cooler 28 that cools the heat generated by the pump as the temperature controller 24, that is, cools the oil flowing through the drain of the pump. 32), the oil level gauge 34 for checking the amount of oil in the oil tank and the section filter 30 for removing the foreign matter of the oil through a filter of 100 ~ 200 mesh.

The variable speed switched reluctance motor 12 is connected to the power module unit 38 connected to the power supply units 40, 42, and 44, and is integrally formed with the fixed capacity pump 14 to supply the fixed capacity pump 14. Drive it variably. In addition, the variable speed switched reluctance motor 12 is connected to the controller 20 through an encoder 36 for checking the rotation speed of the variable speed switched reluctance motor 12. The encoder 36 provides the controller 20 with the checked rotation speed of the variable speed switched reluctance motor 12.

The controller 20 is connected to a pressure sensor 13 connected to a relief 15 that maintains the maximum pressure in the pipe and receives analog current and pressure feedback from the pressure sensor 13. Here, the pressure sensor 13 not only checks the pressure in the pipe and provides it to the controller 20, but also functions as a pressure switch to cut off the power supply to the equipment when the power failure or the pipe is broken during operation.

In addition, the controller 20 receives pulse and position feedback through the encoder 36. Oil is supplied from the section filter 30 to the hydraulic cylinder 2 via the control valve 4 by the fixed displacement pump 14.

 The operation of the hydraulic unit according to the present invention will now be described.

When power is supplied from the power supplies 40, 42, 44, all components are ready. At the same time, the pressure sensor 13 determines whether the pressure in the pipe is a set pressure, for example, 50KG, and transmits its information to the controller 20. The controller 20 drives the variable speed switched reluctance motor 12 to rotate at a rotational speed capable of maintaining this 50KG if it determines that the pressure in the pipe is, for example, 50KG or less from the information transmitted by the pressure sensor 13. The fixed displacement pump 14 then operates at the same speed as the rotational speed by the variable speed switched reluctance motor 12 to supply oil into the piping. At this time, the oil pressure in the pipe is maintained at 50KG, and at the same time, the controller 20 transmits the information that the pressure sensor 13 is 50KG. The controller 20 then rotates the variable speed switched reluctance motor 12 at low speed.

On the contrary, when the hydraulic cylinder 2 is performing the machining or clamping operation, if the control valve 4 is operated, the pressure in the pipe is lowered. (I.e., oil is supplied to the hydraulic cylinder 2 and the hydraulic cylinder is operated accordingly.) At this time, when the pressure sensor 13 determines that the pressure in the pipe is, for example, 50KG or less, it transmits it to the controller 20. . The controller 20 rotates the variable speed switched reluctance motor 12 at a speed that can be maintained at 50 KG.

At this time, the encoder 36 always reads the rotation speed of the variable speed switched reluctance motor 12 and transmits it to the controller 20. Here, when the signal transmitted from the encoder 36 transmits a signal that the variable speed switched reluctance motor 12 is not rotating at the speed required by the controller 20, the controller 20 again transmits the variable speed switched reluctance motor 12. ) To 50KG. At this time, if the variable speed switched reluctance motor 12 does not rotate at the speed required by the controller 20, the controller 20 executes an alarm mode. At this time, the encoder 36 always checks the rotation speed of the variable speed switched reluctance motor 12 to provide a signal to the controller 20.

4 illustrates the variable speed switched reluctance motor 12 according to the present invention in detail, and summarizes the features of the variable speed switched reluctance motor 12 as follows.

(A) The motor configuration is simple.

The magnetic structure of the motor is simpler than the induction motor, which reduces the manufacturing cost by 20-30%. That is, the variable speed switched reluctance motor 12 of the present invention has a simple winding operation because there is no slot of the stator and a slot of the rotor.

(B) Multifunctionalization is easy.

Since the power supply switch circuit is a power semiconductor element, it can serve as a functional role, thereby enabling the motor to be multifunctional. Permanent magnet type synchronous motors and commutatorless DC motors have been developed for the purpose of multifunction and brassization, and they have been used for about 30 to 40%, but they are complicated by the inverter circuit and the entire system due to the use of permanent magnets. Its price is low, so its versatility is low.

(C) It is a high efficiency electric system.

The efficiency is about 10 to 20% higher than the standard induction motor and about 5% higher than the high efficiency induction motor, which is advantageous in terms of economy rather than developing a high-efficiency high-efficiency motor.

(D) Economic feasibility is high.

There is a need for a drive system for driving a motor, but various methods have been developed, and a simpler, smaller and lower cost drive circuit has been developed and patented. The additional cost for these can be sufficiently replaced by the reduction of manufacturing cost due to the simplification of the motor mechanism, which is more economical than the inverter driven induction machine.

(E) System controllability is strong.

It has the inherent characteristics of the stepper motor with excellent torque characteristics, and has the DC series motor characteristics. In addition, it is possible to operate smoothly from starting to normal variable speed, and can be applied to the output range of the current vector controlled induction motor system and has excellent controllability.

(F) It is advantageous for traction drive.

High torque starting torque is large and is efficient as a driving source requiring traction force in accordance with the demand of load torque proportional to the square or cube of rotation speed.

(G) Vibration noise is high.

Since the torque generating mechanism uses the reluctance torque rather than the continuous method by the rotating magnetic field, there is a fear that the noise is greater than that by the rotating magnetic field. However, research is being conducted to reduce the noise level by applying the appropriate design and control method, which will be filed later.

Comparing the characteristics of the variable speed switched reluctance motor 12 with the conventional induction motor as described above can be summarized as follows.

1) Torque / Stator Volume

The variable speed switched reluctance motor 12 of the present invention has a magnetic flux density of 40% or more higher than that of a standard induction machine, but the stator loss is 1/3, and the torque per unit volume is 50% lower than that of a high efficiency induction motor. Is higher than

2) Torque / Inertia Ratio

This value represents the speed response characteristic of the motor, which is 2.35 times higher on average for a 10 Hz motor than an induction motor. This is because the structure of the rotor is simple and there is no rotor winding, so the diameter of the rotor can be adjusted, so that the low inertia variable speed switched reluctance motor can be up to 8.0 times higher than the induction motor.

3) Torque / field weight

The total electric field weight in the motor is important in terms of price and also relates to the weight reduction of the electric equipment. Torque / unit electric field weight is higher than high efficiency motor.

4) Converter VA

Variable speed switched reluctance motors require a separate converter (Volt-Ampere) compared to induction motors. Thus, the value of KVA / KW is 1.16 times that of standard motors and 1.29 times that of high efficiency motors. However, much lower VA is required compared to inverter drive motors for variable speed drives.

5) Rotor restraint torque

The restraint torque of a variable speed switched reluctance motor depends on the position of the rotor, but due to the series nature of the motor, its magnitude is large enough compared to the induction machine.

6) efficiency

The efficiency characteristics of the load are compared with the high efficiency motor and the variable speed switched reluctance motor for the entire load range.

7) Temperature rise characteristic

The temperature rise characteristics are considerably improved over high efficiency induction motors or standard induction motors because of the absence of rotor windings and simple stator windings.

Induction motors, permanent magnet synchronous motors, variable speed switched reluctance motors, and the like are adopted as driving motors. These motors have their own characteristics. Until now, induction motors have been mainly developed and applied, but permanent magnet synchronous motors show higher efficiency at loads requiring various acceleration and deceleration driving patterns. However, permanent magnet motors have a disadvantage of low economical efficiency compared to induction machines. Variable speed switched reluctance motors have the same performance as permanent magnet synchronous motors and are more economical than inductors. Therefore, power sources adopting variable speed switched reluctance motors are being considered as a viable alternative. Variable speed switched reluctance motors are being studied in academia and industry. In particular, the company has no record of research and development for the Lt. Motor. Table 1 below shows the performance comparison table of induction motor, permanent magnet synchronous motor, and variable speed switched reluctance motor made of NEMA 184 frame. Variable speed switched reluctance motors, induction motors, and permanent magnet synchronous motors have outputs of 9, 5 and 14.5 horsepower, respectively, with the gray part being the best feature. It can be seen that the performance of the permanent magnet synchronous motor, the economical variable speed switched reluctance motor is the best.

{Table 1}

On the other hand, the energy-saving hydraulic unit having the configuration as described above has the following features.

First, the hydraulic unit of the present invention provides the required pressure flow rate at a necessary time according to the load state by monitoring the pressure and the rotational speed.

Secondly, when holding pressure, rotate at low speed while maintaining the required pressure.

Third, it is fully compatible with the conventional unit and can be operated only by connecting the 220V commercial power supply.

Fourth, the pressure and flow rate are displayed digitally for easy viewing. It is equipped with two pressure switch functions for high pressure side and low pressure side for safety.

Fifth, the surge pressure is controlled to be minimized by controlling the pressure rise time even during startup.

Sixth, energy can be drastically reduced because the motor rotation speed in the holding pressure state, which occupies most of the hydraulic pump, can be lowered to the minimum required.

Seventh, the lowest noise of about 57dB-A, 3.5MPa occurs during packing.

Eighth, the weight ratio is reduced by 50% compared to the conventional hydraulic unit.

Ninth, it is possible to use the machine as it is currently used, and there is no need for remodeling or demanding construction on the machine side.

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Typically, in machine tools, most of the operating time is in the holding pressure state in which only the pressure is maintained. In this holding pressure, the amount of hydraulic pressure is very small, but the conventional pump unit was wasting energy by operating at the same motor speed as in operation. The hydraulic unit according to the present invention employs a simple, low-loss small fixed displacement pump, a switch reluctance motor and a controller to minimize the number of revolutions at the compensating pressure to drastically reduce mechanical loss and noise and consume as much energy as necessary. Can operate the mechanism.

This is the result of energy saving measures by analyzing the hydraulic cylinder operation in detail and grasping the state of holding pressure by pressing the workpiece and the time the cylinder is driven.

In other words, when observing the time change of the power consumption of the hydraulic unit, the hydraulic cylinder is operating time is 15% to 20%, the remaining time is the time to compensate the pressure. In the hydraulic unit, overwhelmingly, the compensating pressure occupies many parts. Therefore, it was found that reducing the power consumption at the compensating pressure would have a large energy saving effect. Significant energy savings are possible by lowering the motor speed in the holding pressure state, which determines most of the hydraulic unit operation. In addition, by adopting a simple, low-loss small fixed capacity pump and a high efficiency switched reluctance motor and controller, the working environment due to ultra-low noise is improved when holding pressure, and the compact and lightweight structure saves resources without using magnets. Provide hydraulic units. In addition, the machine currently in use may simply change the hydraulic unit of the present invention without any mechanical modifications or difficult construction. In addition, it is only necessary to connect the power supply, and there is no need for wiring or input signals to the controller only by the demanding NC control. And since the minimum flow required to flow at low speed rotation, the deterioration during operation is improved than before.

1 is a view schematically showing a conventional hydraulic unit.

2 is a view showing a hydraulic unit according to an embodiment of the present invention.

3 is a view showing in more detail the hydraulic unit of FIG.

4 shows a variable speed switched reluctance motor 12 according to the invention.

<Explanation of symbols for main parts of the drawings>

2: hydraulic cylinder 4: control valve

6: oil tank 12: variable speed switched reluctance motor

14: fixed displacement pump 20: controller

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Claims (4)

In the energy-saving hydraulic unit including a hydraulic cylinder that generates mechanical energy by the high pressure generated from the oil conveyed through the pipe, An oil tank for storing the oil; A controller configured to generate a hydraulic control signal by receiving power applied from the outside; A variable speed switched reluctance motor operating in response to the hydraulic control signal from the controller; An encoder for checking a rotation speed of the variable speed switched reluctance motor and sending a corresponding signal to the controller; A pressure sensor connected to a relief installed in the pipe to check a pressure in the pipe and send a signal to the controller; A fixed displacement pump for transferring oil in the oil tank through the pipe in response to an output signal from the variable speed switched reluctance motor, And the controller lowers the rotation speed of the variable speed switched reluctance motor when the pressure of the hydraulic cylinder is compensated, and increases the rotation speed of the variable speed switched reluctance motor when the hydraulic cylinder is operated. The controller of claim 1, wherein the controller controls the rotation speed of the variable speed switched reluctance motor to about 200 rpm or less when the hydraulic pressure is compensated for, and reduces the rotation speed of the variable speed switched reluctance motor when the hydraulic cylinder is operated. Hydraulic unit characterized in that the control at 4800rpm or more. delete delete