Velocity-pressure control apparatus of hydraulic machine

A velocity-pressure control apparatus of a hydraulic machine includes a pressure command generator, a pressure sensor, a pressure controller, a velocity command generator, a velocity limiter, a switch, a comparator, a velocity sensor, and a motor driver. The pressure controller receives a pressure compensation signal composed by the pressure command generator and the pressure sensor. The velocity limiter receives a compensation velocity signal from the pressure controller and a predetermined velocity signal from the velocity command generator and outputs a corresponding limiting velocity command signal to the switch. The comparator controls the velocity-pressure control apparatus to work at a velocity control mode when the pressure compensation signal is a positive signal or a null signal, and controls the velocity-pressure control apparatus to work at a master pressure control and slave velocity control mode when the pressure compensation signal is a negative signal.

BACKGROUND

1. Technical Field

The present disclosure relates to control apparatuses, and particularly to a control apparatus for controlling motor velocity and hydraulic pump pressure of a hydraulic machine.

2. Description of Related Art

Hydraulic machines, such as hydraulic injection molding machines, are operated by hydraulic pumps controlled by motors. Motor velocity and hydraulic pump pressure are controlled by a control apparatus to make moveable elements of the injection molding machine work. Generally, product engineers manually adjust velocity and pressure according to experience, which may not be accurate and is inconvenient.

What is needed is to provide a velocity-pressure control apparatus of a hydraulic machine to overcome the above-described shortcomings.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an exemplary embodiment of a velocity-pressure control apparatus is configured for controlling a motor50to control a hydraulic pump, such as an oil pump60of a hydraulic machine, such as a hydraulic injection molding machine. The velocity-pressure control apparatus includes a velocity-pressure switch module10, a motor driver20, a pressure sensor30, and a velocity sensor40. The velocity-pressure switch module10is connected to the motor50via the motor driver20.

The velocity-pressure switch module10includes a pressure command generator11, a first comparison unit12, a pressure controller13, a velocity limiter14, a velocity command generator15, a switch such as a relay16, a comparator17, and a second comparison unit18. In one embodiment, the relay16includes a single-pole double-throw (SPDT) switch K, and a control terminal to control the SPDT switch K. The SPDT switch K includes a first throw1, a second throw2, and a pole3.

The pressure command generator11is configured for outputting a target pressure signal of the oil pump60, and giving a desired pressure of the oil pump60to a positive terminal A of the first comparison unit12. The pressure sensor30senses current pressure of the oil pump60and transmits a pressure sensing signal relaying the current pressure to a negative terminal B of the first comparison unit12. The first comparison unit12outputs a pressure compensation signal via an output C, by subtracting the pressure sensing signal from the target pressure signal and sending the pressure compensation signal to an input of the pressure controller13and an input of the comparator17.

The pressure controller13receives the pressure compensation signal and obtains a compensation velocity according to the pressure compensation signal, and then correspondingly outputs a compensation velocity signal to an input of the velocity limiter14. The comparator17receives the pressure compensation signal. When the pressure compensation signal is a positive signal or a null signal, namely the current pressure of the oil pump60is less than or equal to the expectation pressure, the comparator17outputs a velocity control signal to the control terminal of the switch K to control the switch K to connect the pole3to the first throw1. When the pressure compensation signal is a negative signal, namely the current pressure of the oil pump60is greater than the desired pressure, the comparator17outputs a pressure control signal to the control terminal of the switch K, to control the switch K to connect the pole3to the second throw2.

The velocity command generator15is configured for outputting a predetermined velocity signal, giving a predetermined velocity, to the velocity limiter14. An output of the velocity limiter14is connected to the second throw2of the switch K. The velocity limiter14compares the compensation velocity signal with the predetermined velocity signal, and outputs the smaller velocity signal as a limiting velocity command signal. The velocity command generator15is also configured for outputting a target velocity signal, giving a desired velocity to the first throw1of the switch K. When the pole3is connected to the second throw2of the switch K, the limiting velocity command signal is output to a positive terminal A of the second comparison unit18. When the pole3is connected to the first throw1of the switch K, the target velocity signal is output to the positive terminal A of the second comparison unit18.

The motor driver20includes a velocity controller22and a current limiter24. The velocity sensor40senses a current velocity of the motor50and transmits a corresponding velocity sensing signal to a negative terminal B of the second comparison unit18. The second comparison unit18outputs a velocity compensation signal via an output C, by subtracting the velocity sensing signal from the target velocity signal and sending the velocity compensation signal to an input of the velocity controller22. The velocity controller22processes the velocity compensation signal and then drives the motor50via the current limiter24.

In use, the velocity-pressure control apparatus works at a velocity control mode at first, wherein the pole3is connected to the first throw1of the switch K. At this time, the motor driver20receives the velocity compensation signal from the second comparison unit18, so as to control acceleration of the motor50such that the pressure of the oil pump60increases. At the same time, the comparator17receives the pressure compensation signal from the first comparison unit12. If the pressure compensation signal is a positive signal or a null signal, the velocity-pressure control apparatus continues to work at the velocity control mode. If the pressure compensation signal is a negative signal, the comparator17outputs the pressure control signal to control the switch K to connect the pole3to the second throw2. The motor driver20receives the velocity compensation signal from the second comparison unit18, so as to control deceleration of the motor50such that the pressure of the oil pump60decreases. Therefore, the velocity-pressure control apparatus works at a master pressure control and slave velocity control mode.

Because the motor50and the oil pump60works at the velocity control mode when the pressure of the oil pump60increases, the motor50is rotated at a very fast velocity in this period, which can reduce time for increasing the pressure of the oil pump60. Because the motor50and the oil pump60works at the master pressure control and slave velocity control mode when the pressure is reduced, the velocity of the rotation of the motor50can be limited, which can avoid shaking of the hydraulic machine.