JPS6140618A - Constant pressure controller using motor - Google Patents

Abstract

PURPOSE:To make the pressure applied to a load reach quickly a pressure command value by providing a current command signal limiting circuit which is controlled with a pressure command signal to set the upper limit of a current command signal in accordance with the magnitude of this pressure command signal. CONSTITUTION:A speed control amplifier 12 is provided with a current command signal limiting circuit 18 additionally. A pressure command signal epi outputted from a pressure command circuit 7 is amplified by an amplifier 19 with a prescribed amplification factor determined in consideration of the rigidity and the viscosity of a load 3 and is outputted as a pressure command signal epi'. A current command signal DELTAen0' from an amplifier 12 and the signal epi' from the amplifier 19 are inputted to an output limiting circuit 20, and the circuit 20 sets the upper limit of the current command value in accordance with the magnitude of the pressure command value. That is, a current command signal DELTAen1' is outputted which is limited with the larger upper limit value in case of the smaller pressure command value and is limited with the smaller upper limit value in case of the larger pressure command value.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a constant pressure control device using an electric motor, in particular, a pressure sensor attached to a transmission mechanism of the motor output to the load. The present invention relates to a device that controls the pressure applied to a load by electric motor output and force to a constant level in accordance with a pressure command while detecting the pressure applied to the load.

[Prior Art] A constant pressure control device that applies a predetermined pressure to a load by controlling the drive of an electric motor to a predetermined I to torque in response to a pressure (or torque) command given from the outside is conventionally known. For example, it is applied to T-making machines, injection molding machines, etc.

FIG. 6 shows an example of a conventional closed-loop constant pressure control device that can always perform highly accurate constant pressure control. In the figure, a transmission mechanism 2 with low rigidity is attached to the output shaft of the electric motor ii, and the driving force of the electric motor 1 is transmitted to a load 3 such as a workpiece through this transmission mechanism 2, and the load 3 is kept constant. It will be pressed by pressure. A pressure sensor 4 is installed between the transmission mechanism 2 and the load 3, and the pressure detection signal output from the pressure sensor 4 is converted by a conversion circuit 5 into a pressure detection signal e consisting of a voltage signal. and is supplied to the summing point 6. Further, the addition point 6 is supplied with a pressure command signal e p i having a voltage level according to the pressure command from the pressure command circuit 7 . As a result, the summing point 6 outputs an error signal e -e = Δe, and the error signal is amplified by the pressure control amplifier 8 and supplied to the summing point 9 as the speed command signal Δe po. .

The electric motor 1 also includes a speed generator 1 as a speed sensor.
The speed detection signal detected by the speed generator 10 is converted into a speed detection signal e consisting of a voltage signal by a conversion circuit 11' and is supplied to the summing point 9. As a result, from addition point 9, Δe −e −Δe
An error signal o is output, and the error signal Δeo is amplified by the speed control amplifier 12 and supplied to the addition point 13 as the current command signal Δeno.

Further, the input current that determines the output torque of the electric motor 1 is detected by a current detector 14, and the current detection signal from the current detector 14 is converted by a conversion circuit 15 into a current detection signal e consisting of a voltage signal, which is then sent to an addition point. 13. As a result, the addition point is 13 or ) 1 is Δeno-ei
An error signal =Δet is output, and the error signal Δei is amplified to Δe· by the current control amplifier 16 and then supplied to the power converter 17.

The power converter 17 is configured with an ignition control circuit using a thyristor or a pulse width control circuit using a transistor, and supplies a predetermined current to the motor 1 based on 〇io in the previous delivery month. is configured to drive.

[Problems to be Solved by the Invention] However, in such a conventional constant pressure control device, the amplification degree of the speed control amplifier 12 is fixed regardless of the pressure command value, so the following problem occurs. There was a problem. Now, as shown in FIG. 7(A), if the pressure command signal e p t having a step-like voltage waveform is output from the pressure command circuit 7 at time To, the pressure applied to the load 3 is During the transition period until the pressure reaches the pressure responsive to the pressure command signal, the pressure applied to the load 3 fluctuates by becoming stronger or weaker than the command pressure. Therefore, the pressure detection signal e changes in a damped oscillatory manner as shown.

In this case, if the amplification degree of the speed control amplifier 12 is constant, the current command signal Δe becomes too large when the pressure command value is large, resulting in the pressure command signal n.

The error signal Δe between e and the pressure detection signal e is positive pI
In the case of p, the transmission mechanism 2 presses the load 3 with more force than necessary (3 to 5 times the rated torque of the electric motor 1), and if the error signal 〇 is negative, the transmission mechanism 2 presses the load 3. 3, it will be pushed back. As a result, the sliding table of the transmission mechanism 2, which has low rigidity, repeatedly moves back and forth, and the pressure that presses the load 3 gradually reaches the pressure command value while repeating large vibrations.

The travel time β and settling time t of the pressure detection signal e are determined by the magnitude of the output signal of the speed control amplifier 12, and the rising angle α of the pressure detection signal e is determined by the pressure control amplifier 8.
However, in conventional devices where the amplification degree of the speed control amplifier 12 is fixed regardless of the pressure command value, if the pressure command value is large, the amplifier If the □ output of 12 becomes too large, it will take a long time for the pressure applied to the load to respond to the pressure command □ value, additional force will be applied to the load 3, and large vibrations will occur in the transmission mechanism 2. As a result, there was a drawback that the life of the gear system of the transmission machine 1M2 was shortened.

The purpose of the present invention is to quickly adjust the pressure applied to the negative pressure to the pressure command value. The object of the present invention is to provide a constant pressure control device using an electric motor that can reach 11.

[Means for solving the problem] In order to solve the above problem, the first invention of the present application uses a pressure detection signal and a pressure command obtained by detecting the pressure on the load due to the output of the electric motor with a pressure sensor. The difference signal from the signal is operationally amplified to obtain a speed command signal, and the rotational speed of the electric motor is set to 3ii.
A difference signal between the speed detection signal detected by the Ff sensor and the speed command signal is operationally amplified to obtain a current command signal, and the current detection signal obtained by detecting the input current of the motor with the current detector and the By driving the motor based on the signal obtained by operationally amplifying the difference signal from the current command signal, the pressure applied to the load exerted on the output of the motor is kept constant.
A constant pressure control device using a controlled electric motor, characterized in that a current command signal limiting circuit is provided that is controlled by the pressure command signal and limits the upper limit of the current command signal according to the magnitude of the pressure command signal. It is said that

In addition, the second invention of the present application provides a pressure detection signal obtained by detecting the pressure on the load due to the output of the electric motor with a pressure sensor, and a difference signal between the pressure detection signal and the location command signal, which is operationally amplified and used as a speed command signal. The difference signal between the speed detection signal obtained by detecting the rotational speed with a speed sensor and the speed command signal is operationally amplified to obtain a current command signal, and the input current of the electric iIJ machine is detected by a current detector. A constant control method using an electric motor that controls pressure on a load due to the output of the electric motor to a constant level by driving the electric motor based on a signal obtained by operationally amplifying a difference signal between a current detection signal and the current command signal. The pressure control device is characterized in that a current detection signal correction circuit is provided which is controlled by the pressure command signal and increases or decreases the current detection signal value according to the magnitude of the pressure command signal.

[Operation of the invention] In the first invention, the current command signal limiting circuit limits the upper limit of the current command value according to the magnitude of the pressure command value, so that when the pressure command value is too large, The magnitude of the current command signal in speed control is limited to a lower value. Furthermore, in the second invention, the current detection signal correction circuit increases or decreases the current detection signal value according to the magnitude of the pressure command value, so when the pressure command value is large,
The value of the current detection signal in speed control is larger than in conventional devices. As described above, in any of the above inventions, the speed command signal can be increased by increasing the amplification degree of the pressure control amplifier, and constant pressure control can be performed such that the pressure applied to the load quickly reaches the pressure command value. Can be done.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows an embodiment of the first invention of the present application, and in the figure, the same parts as those of the above-mentioned conventional device are given the same reference numerals and the explanation thereof will be omitted.

A feature of the present invention is that a current command signal limiting circuit 18 is added to the speed control amplifier 12 to limit the upper limit of the current command value according to the magnitude of the pressure command value. The current command signal limiting circuit 18 has an amplifier 19 and an output limiting circuit 20, as shown in FIG. 2, and has a pressure command signal e p + output from the pressure command circuit 7. is amplified by the amplifier 19 at a predetermined amplification degree determined in consideration of the stiffness and viscosity of the load 3, and is output as a pressure command signal e p , l . The output limiting circuit 20 receives the current command signal Δeno' from the speed control amplifier 12 and the pressure command signal e from the amplifier 19.
, , l are input, and the upper limit of the current command value is limited according to the magnitude of the pressure command value. In other words, when the pressure command value is small, it is large and limited by the limit value, and when the pressure command value is large, the current command value is limited. outputs a current command signal Δeo1' which is limited by a small upper limit value. Note that the pressure command signal e,
Since the i-characteristic of 1' differs depending on the direction of rotation of the electric motor 10, the output limiting circuit 20 performs an output limiting operation according to the absolute values of the pressure command signals e, , and l.

FIG. 3 (A>) shows the relationship between the input signal Δe' and the output signal Δeo1' of the current command signal limiting circuit 18.

FIG. 3 is a characteristic curve diagram showing the magnitude of the pressure command signal e as a parameter. As seen in the figure, as the pressure command signal e,1 becomes larger, the magnitude of the output signal is limited by the low value of the input signal. Saturation value e7 of the output signal in this case
is a value determined by the Zener voltage of the Zener diode 20d in the output limiting circuit 20 of FIG.

In this way, in this embodiment, the current command value is limited according to the magnitude of the pressure command value, so when the pressure command value is large, the magnitude of the current command signal in speed control is smaller than in the device shown in FIG. is limited to a low value. Therefore, it is possible to conversely increase the amplification degree of the pressure control amplifier 8 to increase the speed command signal Δe. As a result, the pressure response characteristic to the load with respect to the pressure command becomes 7. This is improved as shown in Figure (B). In other words, as can be seen by comparing the characteristics of both figures, the rising angle of the pressure detection signal curve indicating the pressure response is α′
>α, and the settling time becomes 1′<t. Therefore, constant pressure control can be performed such that the pressure applied to the load quickly reaches the pressure command value.

Since FIG. 4 shows an embodiment of the second invention of the present application, parts in this figure that are the same as those of the conventional device shown in FIG.

A feature of the present invention is that a current detection signal correction circuit 21 is provided in addition to the above-mentioned conversion circuit 15 for increasing or decreasing the current detection signal value according to the magnitude of the pressure command value. This current detection signal correction circuit 21 has an amplifier 22 and a feedback amount conversion circuit 23, as shown in the concrete configuration in FIG. 5, and the pressure command signal e p H output from the pressure command circuit 7 is The amplifier 22 amplifies the stiffness and viscosity of the load 3 by a predetermined amplification degree, and outputs the signal as a pressure command signal e. The above pressure command signal e
・'' and the current detection signal e from the conversion circuit 15 mentioned above.
'' is input, and outputs a corrected current detection signal e', , II, which decreases the current detection signal value when the pressure command value is small, and increases the current detection signal value when the pressure command value is large. do.

FIG. 3(B) is a characteristic curve diagram showing the relationship between the input signal e. As can be seen in the figure, the larger the pressure command signal e p t is, the larger the output signal becomes for an input signal of the same magnitude.

In this way, in this embodiment, the current detection signal value is increased/decreased according to the magnitude of the pressure command value, so when the pressure command value is large, the current detection signal value in speed control is lower than that in the device shown in Fig. 6. The value of increases. As a result, as in the previous embodiment, the amplification degree of the pressure control amplifier 8 is increased and the speed command signal Δe.

As a result, the response characteristic of the pressure applied to the load to the pressure command is the same as in the previous embodiment.
As shown in Figure (B), it is possible to perform constant pressure control such that the pressure applied to the load quickly reaches the pressure command value.

[Effects of the Invention] As explained above, according to the first invention of the present application, the upper limit of the current command value is limited according to the magnitude of the pressure command value, and the second invention According to the invention, the current detection signal value is increased or decreased in accordance with the magnitude of the pressure command value, so in any case, the speed command signal can be increased by increasing the amplification degree of the pressure III control amplifier. , it is possible to perform constant pressure control such that the pressure applied to the load quickly reaches the pressure command value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a specific configuration example of the current command signal limiting circuit in FIG. 1, and FIG. FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 shows a specific example of the current detection signal correction circuit shown in FIG. 4. The circuit diagram shown in Figure 3 (
B) is a characteristic curve diagram showing an example of the characteristics of the current detection signal correction circuit, FIG. 6 is a block diagram showing an example of a conventional constant pressure control device, and FIG. 7(A) is a characteristic curve diagram showing an example of the characteristics of the current detection signal correction circuit. FIG. 7B is a characteristic curve diagram showing the response characteristic of the pressure applied to the load to the pressure command. FIG. 7(B) is a characteristic curve diagram showing the response characteristic of the pressure applied to the load to the pressure command in the above embodiment. 1... Electric motor, 2... Transmission mechanism, 3... Load, 4
...Pressure control circuit, 7..Pressure command circuit, 8..Pressure control amplifier, 10..speed generator as speed sensor, 12..speed r! ! lIl control amplifier, 14...
Current detector, 16... Current control amplifier, 17... Power converter, 18... Current command signal limiting circuit, 21...
・Current detection signal correction circuit. IIQ-

Claims (2)

[Claims] (1) The pressure on the load due to the output of the electric motor is detected by a pressure sensor, and the difference signal between the pressure detection signal and the pressure command signal is operationally amplified to produce a speed command signal, and the rotational speed of the electric motor is determined by the speed sensor. A difference signal between the speed detection signal obtained by detection and the speed command signal is operationally amplified to obtain a current command signal, and a current detection signal obtained by detecting the input current of the motor with a current detector and the current command signal. In a constant pressure control device using an electric motor, the electric motor is controlled to a constant pressure on a load due to the output of the electric motor by driving the electric motor based on a signal obtained by operationally amplifying a difference signal between the pressure command and 1. A constant pressure control device using an electric motor, comprising a current command signal limiting circuit that is controlled by a signal and limits an upper limit of the current command signal according to the magnitude of the pressure command signal. (2) A difference signal between a pressure detection signal obtained by detecting the pressure on the load due to the output of the electric motor with a pressure sensor and a pressure command signal is operationally amplified to obtain a speed command signal, and the rotational speed of the electric motor is determined using the speed sensor. A difference signal between the speed detection signal obtained by detection and the speed command signal is operationally amplified to obtain a current command signal, and a current detection signal obtained by detecting the input current of the motor with a current detector and the current command signal. In a constant pressure control device using an electric motor, the electric motor is controlled to a constant pressure on a load due to the output of the electric motor by driving the electric motor based on a signal obtained by operationally amplifying a difference signal between the pressure command and A constant pressure control device using an electric motor, characterized in that a current detection signal correction circuit is provided which increases or decreases the current detection signal value under control of a signal and corrects the current detection signal value according to the magnitude of the pressure command signal.