JP5362241B2 - Proportional solenoid valve drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress divergence between a current flowing in a proportional solenoid valve and a target current without increasing heat loss even in a low current area. <P>SOLUTION: The drive unit comprises: current conversion means 10 and 12 which convert a drive instruction value for driving the proportional solenoid valve V to a current instruction value A showing a target current to be supplied to the solenoid valve V; dither instruction means 14 and 16 which determine a dither instruction value B including at least an amplitude instruction of dither current; a current monitoring part 24 which detects a current supplied in the valve V; a PWM signal generation part 18 which generates PWM signal based on the current instruction value A output by the conversion means 10 and 12, the dither instruction value B output by the instruction means 14 and 16, and a monitor current I output by the current monitoring part 24; and a comparison part 26 which compares the monitor current I with the current instruction value A. The dither instruction means 14 and 16 adjust the amplitude instruction value of dither current according to the comparison result by the comparison part 26. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a proportional solenoid valve drive device for flowing a dither superimposed current through a proportional solenoid valve, and more particularly to a proportional solenoid valve drive circuit that suppresses waveform distortion of a dither superimposed current in a low current range.

  Proportional solenoid valves used in various actuators adjust the position of the spool in contact with the plunger and control the hydraulic pressure by controlling the position of the plunger with the electromagnetic force generated by the current flowing through the coil. FIG. 6 shows an example of a proportional solenoid valve.

  Here, the position of the spool is determined by the current flowing through the coil. Accordingly, the drive circuit of the proportional solenoid valve outputs a command value so that the current flowing through the coil becomes a desired current (target current). In addition, in order to improve the response of the spool and suppress the influence of the hysteresis characteristic of the magnetic material, a dither current that vibrates at a constant period is superimposed on the current that actually flows through the coil. FIG. 7 shows an example of the waveform of the dither superimposed current on which the dither current is superimposed. In this case, the spool position is determined by the average current of the dither superimposed current indicated by the broken line in the drawing.

  The proportional solenoid valve drive circuit uses a proportional value obtained by adding a command value for superimposing the dither current to a command value for causing the target current to flow in order to cause the dither superimposed current shown in FIG. Give to the solenoid valve.

Here, in the proportional solenoid valve control device of Patent Document 1, a time constant circuit of the proportional valve coil is made small by adding a resistor in parallel to the proportional valve coil to the time constant circuit of the output stage circuit.
Japanese Patent Laid-Open No. 10-184972

  Incidentally, a PWM (Pulse Width Modulation) circuit shown in FIG. 8 is generally used as a drive circuit for the proportional solenoid valve. In this PWM circuit, when the current is decreased, the semiconductor switch is turned off, and the current is converted into heat by the free wheel diode and the winding resistance and consumed.

Vf：フリーホイールダイオードの順電圧 The voltage relationship of each electrical element when this current is reduced is as shown in Equation (1).

Vf: Freewheeling diode forward voltage

  Here, Vf and L * di / dt are constant regardless of the current i (t), whereas R * i (t) is proportional to the current. Therefore, there is a limit point at which equation (1) is established. Where the formula (1) does not hold, the current gradient becomes gentle and the di / dt becomes small, so that the relation of the formula (1) is maintained. In this case, as shown in FIG. 9, the dither waveform is distorted and the current is not sufficiently reduced.

  From the above, when the dither current is superimposed on the target current, when the target current value is high, the commanded current flows through the proportional solenoid valve, but in the low current range, the current does not fall due to waveform distortion, There was a problem that the average current increased and a larger current than the target current flowed. This is shown in FIG.

  Here, the fact that the average current is deviated from the target current means that the position of the plunger, that is, the position of the spool is deviated, and as a result, the hydraulic control is deviated.

  When the circuit of Patent Document 1 is used, the above-described waveform distortion in the low current region is improved, but another problem arises in that heat loss increases due to the use of current braking by resistance.

  Therefore, an object of the present invention is to suppress the deviation between the current flowing through the proportional solenoid valve and the target current without increasing the heat loss even in the low current region.

  The drive device (1) for the proportional solenoid valve (V) according to one embodiment of the present invention is a target to drive a drive command value for driving the proportional solenoid valve (V) to the proportional solenoid valve (V). Current conversion means (10, 12) for converting into a current command value indicating current, dither command means (14, 16) for determining a dither command value including at least a dither current amplitude command, and the proportional solenoid valve (V) Current detection means (24) for detecting the current flowing in the current, current command values output from the current conversion means (10, 12), dither command values output from the dither command means (14, 16), and the current PWM signal generating means for generating a PWM (Pulse Width Modulation) signal based on the current detected by the detecting means (24) and supplying the generated PWM signal to the proportional solenoid valve (V). (18) and comparison means (26) for comparing the current detected by the current detection means (24) with the current command value output by the current conversion means (10, 12), and the dither command The means (14, 16) adjusts the amplitude command value of the dither current according to the result of the comparison by the comparison means (26).

  In a preferred embodiment, the comparison means (26) includes a smoothing means (30) for smoothing the current detected by the current detection means (24), and the smoothing means (30) obtains the smoothing. The average current may be compared with the target current determined by the current command value.

  In a preferred embodiment, the comparison means (26) is determined by an integral value of a current larger than a target current determined by the current command value and the current command value for the current detected by the current detection means (24). You may compare with the integrated value of the electric current smaller than a target electric current.

  Hereinafter, a drive device for a proportional solenoid valve according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a proportional electromagnetic valve drive device 1 according to the present embodiment. The proportional solenoid valve drive device 1 receives the drive command value from the operation lever 50 to drive the actuator using the proportional solenoid valve, and drives the proportional solenoid valve. In particular, the proportional solenoid valve drive device 1 according to the present embodiment has a dither amplitude in order to accurately control the average current flowing through the proportional solenoid valve in a low current region where the current flowing through the proportional solenoid valve is equal to or less than a predetermined threshold. Make it smaller.

  The proportional electromagnetic valve drive device 1 may be realized by an electric circuit for each component or function described below, or by causing a computer system including a processor and a memory to execute a predetermined computer program. Alternatively, it may be realized by a semi-custom IC. Further, a combination thereof may be used.

  The proportional solenoid valve drive device 1 includes a current conversion unit 10 that converts a drive command value into a target current that flows through the proportional solenoid valve, a current command generation unit 12 that generates a command value through which the target current flows, A dither current command generation unit 14 that generates a dither command value for superimposing the dither current, a dither adjustment unit 16 that adjusts the dither command value generated by the dither current command generation unit 14, and a current that flows in the proportional solenoid valve V Current adder 17 for adding the current command value A generated by the current command generator 12 and the dither command value B adjusted by the dither adjuster 16, The PWM signal generator 18 that generates a PWM signal based on the output of the error amplifier 27 that detects the difference between the output and the monitor current I output from the current monitor 24, and the semiconductor switch according to the PWM signal C Includes a drive circuit 20 for driving, by comparing the current I and the current command value A obtained by monitoring, a comparing unit 26 for outputting a reduced instruction C of dither amplitude to dither adjuster 16 on the basis of the comparison result.

  The current conversion unit 10 converts the drive command value corresponding to the operation amount of the operation lever 50 into a target current value that is a target value of the current flowing through the proportional solenoid valve V.

  The current command generating unit 12 converts the current command value A to flow the target current value in the proportional solenoid valve V. Here, when the current corresponding to the current command value A, that is, the target current flows through the proportional solenoid valve V, the position of the plunger becomes the target.

  The dither command value generated by the dither current command generator 14 is determined according to the type of the proportional solenoid valve V. For example, the amplitude and frequency of the dither current are predetermined according to the characteristics of the spool of the proportional solenoid valve V. That is, the dither current command generation unit 14 outputs a dither command value including a dither current amplitude and frequency command value determined according to the type of the proportional solenoid valve V.

  The dither adjustment unit 16 adjusts the dither command value generated by the dither current command generation unit 14 according to the target current value output from the current conversion unit 10 and the dither amplitude reduction command C output from the comparison unit 26. For example, when the target current output from the current conversion unit 10 is in the low current region, the dither adjustment unit 16 adjusts the dither command value so as to reduce the amplitude of the dither current generated by the dither current command generation unit 14. (Feed forward). Further, when the average value of the monitor current I obtained by monitoring the current flowing through the proportional solenoid valve V is larger than the target current, a dither amplitude reduction command C is output from the comparison unit 26, and the dither adjustment unit 16 further The dither current amplitude is adjusted to be small (feedback). When the dither amplitude reduction command C includes information indicating the magnitude of the deviation width between the average value of the monitor current I and the target current, the dither adjustment unit 16 increases the dither current as the deviation width increases. The width for reducing the amplitude may be increased.

  Note that the dither adjustment unit 16 may perform only one of feed-forward adjustment and feedback adjustment, or may perform both.

  The PWM signal generation unit 18 is based on the output of the error amplifier 27 that detects the difference between the command value obtained by adding the current command value A and the adjusted dither command value B in the adder 17 and the monitor current I. A PWM signal is generated.

  The drive circuit 20 performs voltage conversion (boost) of the PWM signal and operates the semiconductor switch SW so as to follow the PWM signal.

  The comparison unit 26 compares the current command value A generated by the current command generation unit 12 with the monitor current I monitored by the current monitor unit 24 and actually flowing in the proportional solenoid valve V, and the comparison result is obtained. Output to the dither adjustment unit 16.

  Specific examples of the configuration of the comparison unit 26 are shown in FIGS.

  In the first mode illustrated in FIG. 2, the comparison unit 26 includes a smoothing unit 30 and a comparison unit 32.

  The smoothing means 30 smoothes the monitor current I monitored by the current monitor unit 24 to obtain an average current.

  The comparison unit 32 compares the average current generated by the smoothing unit 30 with the target current indicated by the current command value A. Then, the comparison unit 32 determines whether or not the average current value matches the target current value. When the average current value is larger than the target current value, a dither amplitude reduction command C is output to the dither adjustment unit 16. The dither amplitude reduction command C may include information indicating the magnitude of deviation between the average current value of the monitor current I and the target current value.

  In the second mode shown in FIG. 3, the comparison unit 26 includes integration means 34 and 36 and a comparison means 38.

  The integrating means 34 integrates a current larger than the target current value indicated by the current command value A in the monitor current I for a certain period of time.

  The integrating means 36 integrates a current smaller than the target current value indicated by the current command value A in the monitor current I for a fixed time.

  The comparison unit 38 compares the integration result of the integration unit 34 with the integration result of the integration unit 36, and obtains the difference between the average value of the monitor current I and the target current. That is, if the integration result of the integration unit 34 and the integration result of the integration unit 36 match, the average value of the monitor current I matches the target current. When the integration result of the integration unit 34 is larger than the integration result of the integration unit 36, the comparison unit 38 outputs a dither amplitude reduction command C to the dither adjustment unit 16. Similar to the first aspect, the dither amplitude reduction command C may include information indicating the magnitude of the difference between the average current value of the monitor current I and the target current value.

  The time for the integrating means 34 and 36 to perform integration is at least one cycle of the dither current.

  FIG. 4 is a flowchart showing a processing procedure when determining the dither amplitude in the driving apparatus 1 according to the present embodiment described above. Hereinafter, description will be given according to this flowchart.

  First, the dither adjustment unit 16 receives a dither command value output from the dither current command generation unit 14. Further, the dither adjustment unit 16 receives a target current value output from the current conversion unit 10. Then, the value of the dither amplitude included in the dither command value is determined according to the target current value (S10). For example, the dither adjustment unit 16 reduces the dither amplitude if the target current value is a low current region that is equal to or smaller than a certain threshold value. The dither adjustment unit 16 does not change the dither amplitude included in the dither command value when the target current value is not in the low current region.

  The current monitoring unit 24 constantly monitors the current in the proportional solenoid valve V (S12).

  The comparison unit 26 compares the average value of the monitor current I monitored by the current monitor unit 24 with the target current value indicated by the current command value (S14). When the average value of the monitor current I is larger than the target current value (S16: Yes), the comparison unit 26 outputs a dither amplitude reduction command C to the dither adjustment unit 16, and the dither adjustment unit 16 outputs the dither amplitude. The dither amplitude is reduced according to the reduction command C (S18). On the other hand, when the average value of the monitor current I is not larger than the target current value (S16: No), the comparison unit 26 does not output the dither amplitude reduction command C, so step S18 is skipped.

  The dither adjustment unit 16 outputs a dither command value including a dither amplitude instruction (S20), and thereafter repeatedly executes these processes.

  As a result, the waveform of the dither superimposed current in the low current region is as shown in FIG. That is, when the drive device 1 according to this embodiment drives the proportional solenoid valve V, the amplitude of the dither superimposed current waveform in the low current region is suppressed. The dither superimposed current waveform after amplitude suppression has a smaller current fluctuation range than the dither superimposed current waveform before amplitude suppression. As a result, when the proportional solenoid valve V is driven by the driving device 1 according to the present embodiment, it is less susceptible to the waveform distortion in the low current region that occurs when the amplitude is not suppressed. Therefore, the deviation width between the average current and the target current is also reduced, and the accuracy is improved.

  Further, unlike the invention of Patent Document 1, no new resistance is added to the circuit of the proportional solenoid valve, so that heat loss does not increase as compared with the prior art.

  The above-described embodiments of the present invention are examples for explaining the present invention, and are not intended to limit the scope of the present invention only to those embodiments. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

  For example, in the above-described embodiment, a triangular wave is used as the dither current, but a sine wave or a rectangular wave may be used.

It is a lineblock diagram of drive device 1 of a proportional electromagnetic valve concerning one embodiment of the present invention. A specific example of the comparison unit 26 will be shown. A specific example of the comparison unit 26 will be shown. It is a flowchart which shows the process sequence at the time of determining a dither amplitude in the drive device 1 which concerns on this embodiment. The waveform of the dither superposition | current electric current in the low electric current area | region of the proportional solenoid valve driven by the drive device 1 which concerns on this embodiment is shown. An example of the proportional solenoid valve which concerns on a prior art is shown. An example of the waveform of the dither superimposition current with which the dither current which concerns on a prior art was superimposed is shown. An example of the PWM circuit which concerns on a prior art is shown. 6 shows distortion of a dither waveform in a low current region according to the prior art. The deviation of the target current and the average current in the low current region according to the prior art is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive apparatus 10 Current conversion part 12 Current command generation part 14 Dither current command generation part 16 Dither adjustment part 17 Adder 18 PWM signal generation part 20 Drive circuit 24 Current monitor part 26 Comparison part 27 Error amplifier

Claims (3)

A drive device (1) for a proportional solenoid valve (V),
Current conversion means (10, 12) for converting a drive command value for driving the proportional solenoid valve (V) into a current command value indicating a target current to be passed through the proportional solenoid valve (V);
Dither command means (14, 16) for determining a dither command value including at least a dither current amplitude command;
Current detection means (24) for detecting a current flowing in the proportional solenoid valve (V);
PWM (Pulse) based on the current command value output from the current conversion means (10, 12), the dither command value output from the dither command means (14, 16) and the current detected by the current detection means (24). PWM signal generating means (18) for generating a Width Modulation) signal and supplying the generated PWM signal to the proportional solenoid valve (V);
Comparing means (26) for comparing the current detected by the current detecting means (24) with the current command value output by the current converting means (10, 12),
The comparison means (26) includes a smoothing means (30) for smoothing the current detected by the current detection means (24), and the average current obtained by smoothing the smoothing means (30) and the current Compare with the command value,
The dither command means (14, 16) is a proportional solenoid valve drive device that adjusts the amplitude command value of the dither current based on the result of comparison by the comparison means (26). The comparison means (26)
The proportional solenoid valve drive device according to claim 1, wherein the average current obtained by the smoothing means (30) is compared with a target current determined by the current command value. The comparison means (26)
For the current detected by the current detection means (24), an integrated value of a current larger than the target current determined by the current command value is compared with an integrated value of a current smaller than the target current determined by the current command value. The drive device for a proportional solenoid valve according to claim 1.

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