JPS626329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic device having a proportional solenoid that generates a force proportional to a supplied current value, and particularly to an electromagnetic device having a proportional solenoid suitable for controlling the supplied current value. The present invention relates to a control device.

Electromagnetic devices, such as electromagnetic proportional control valves, which have a proportional solenoid and generate a force proportional to the current supplied to it, are used in a large number of fields. An example is shown in FIG.

In FIG. 1, reference numeral 1 indicates an electromagnetic proportional pressure reducing valve, which is one of electromagnetic proportional control valves, and is composed of a proportional solenoid section 2 and a pressure reducing valve section 3. The proportional solenoid section 2 has a proportional solenoid and an iron core (none of which are shown). 2a and 2b are terminals of the proportional solenoid. 4 is a push rod engaged with the iron core of the proportional solenoid section 2; 5 is a spool of the pressure reducing valve section 3;
a and 5b are both end surfaces of the spool 5, and the end surface 5a
A push rod 4 is in contact with. 5c is spool 5
It is a small hole made in the. 6 is a supply port where pressure oil is supplied, 7 is a return port where oil is discharged, 8
is the output port that outputs hydraulic pressure, 9 is the return port 7
10 is a hydraulic power source connected to the supply port 6.

When a current is supplied from the terminals 2a, 2b to the proportional solenoid, a force proportional to this current is applied to the core of the proportional solenoid section 2, and this force is applied to the spool 5 via the push rod 4 engaged with the core. is transmitted to one end surface 5a of the. As a result, the spool 5 moves to the right from the position shown in the drawing and brings the small hole 5c and the supply port 6 into electrical communication, so that the supply port 6 and the output port 8 communicate with each other via the small hole 5c. As a result, the oil pressure at the output port 8 increases, and the pressure applied to the end surface 5b of the spool 5 also increases. When the pressure on the end surface 5b becomes greater than the pushing force of the push rod 4 (that is, the force applied to the iron core of the proportional solenoid section 2), the spool 5 moves to the left, bringing the small hole 5c and the return port 7 into electrical continuity. Therefore, output port 8
and the return port 7 communicate through the small hole 5c, the hydraulic pressure of the output port 8 decreases, and the pressure received by the end surface 5b also decreases. The pressure that the end face 5b receives is the pressure that the push rod 4 receives.
When the pressing force becomes lower than , the spool 5 moves to the right in the figure again.

In this way, the spool 5 of the pressure reducing valve section 2 operates in response to the force applied to the iron core of the proportional solenoid section 2, so the oil pressure generated at the output port 8 is ultimately proportional to the current supplied to the proportional solenoid. It happens.

FIG. 2 is a block diagram showing an example of a conventional control device for the electromagnetic proportional pressure reducing valve 1. As shown in FIG.

In the figure, 11 is a constant voltage source, and 12 is a constant current amplifier that uses the constant voltage source 11 as its voltage source and generates a current value I proportional to the command input signal V _p . Reference numeral 13 designates a proportional solenoid of the proportional solenoid section 2 to which a current I from the constant current amplifier 12 is supplied, and applies a force proportional to the current I to the iron core. Terminals 2a, 2b, supply port 6, return port 7, output port 8, tank 9, and hydraulic power source 10 are the same as those shown in FIG.

When a command input signal V _p corresponding to a command value for the electromagnetic proportional pressure reducing valve 1 is input to the constant current amplifier 12 , the constant current amplifier 12 supplies a current I proportional to this signal V _p to the proportional solenoid 13 . by the way,
The resistance value of proportional solenoid 13 is proportional solenoid 1
3. It changes depending on the temperature; the higher the temperature, the higher the resistance value, and the lower the temperature, the lower the resistance value. Therefore, if current is supplied solely depending on the command input signal V _p , there is a risk that the desired current cannot be supplied. The constant current amplifier 12 is provided to prevent such a situation from occurring and to supply a desired current even if the resistance value of the proportional solenoid changes.

However, this constant current amplifier 12 has the drawbacks of having a complicated configuration, difficult to adjust, and extremely expensive, and is not particularly suitable for devices using a large number of electromagnetic proportional control valves. .

FIG. 3 is a block diagram of a conventional control device for an electromagnetic proportional pressure reducing valve that does not use a constant current amplifier 12.

In the figure, the same parts as in FIG. 2 are given the same reference numerals, and their explanation will be omitted. Reference numeral 14 denotes a drive amplifier, which is composed of a pulse width modulator 15 and a transistor 16. When the command input signal V _p is input, the pulse width modulator 15 changes the pulse width of a reference pulse in response to the command input signal V p, and generates a pulse width modulation signal (hereinafter referred to as a PWM signal) having this modulated pulse width. V
generate _p . The transistor 16 is connected to the terminal 2b of the proportional solenoid 13, and its conduction and non-conduction are controlled by the PWM signal _Vp . Since the terminal 2a of the proportional solenoid 13 is connected to the constant voltage source 11, when the transistor 16 becomes conductive, a current is supplied to the proportional solenoid 13 according to the conduction time. Note that the transistor 16 may be replaced with an element such as a thyristor.

FIG. 4 is a waveform diagram for explaining pulse width modulation by the pulse width modulator 15.

In Figure 4, the horizontal axis shows time t, and the vertical axis shows PWM.
A signal voltage V _p is taken. Here, the reference pulse has a high level voltage V _h and a low level voltage V _l , and its period is T _p . This reference pulse is a command input signal V input to the pulse width modulator 15.
The pulse width is changed by _p . For example, when the command input signal V _p1 is input, the pulse width becomes T ₁ , and when the command input signal V _p2 smaller than this is input, the pulse width becomes T ₂ , which is smaller than T ₁ . The pulse width with respect to the fundamental period T _p is called the modulation degree (this is expressed as D). That is, the modulation degree D when the command input signal V _p1 is D=T ₁ /T _p ×100 (%),
When the command input signal is V _p2 , D=T ₂ /T _p ×100
(%). Therefore, the modulation degree D and the command input signal V _p are proportional.

FIG. 5 is a waveform diagram of the current flowing through the proportional solenoid 13.

The transistor 16 is conductive when the PWM signal V _p is a high level voltage V _h and is non-conductive when the PWM signal V p is a low level voltage V _l . Now, the impedance of the proportional solenoid 13 is an ideal resistance, and the PWM signal V _p
Assuming that the pulse width of is T ₁ , the proportional solenoid is supplied with a current I _p shown by a dotted line in the figure during period T ₁ . In this case, the average current in the fundamental period T _p is I ₁ , and I ₁ is determined by I ₁ =I _p ×T ₁ /T _p . By the way, actually proportional solenoid 1
3 pulsates as shown by the solid line in the figure due to its inductance, but the current I _p during period T ₁
It has been confirmed that the insufficient current -I for the period (T _p -T ₁ ) is approximately equal to the surplus current +I during the period (T p -T 1 ), and therefore, the average current that actually flows and the average current I ₁ are approximately equal.

In this way, since the modulation degree of the reference pulse can be changed in proportion to the command input signal V _p ,
As a result, current can be supplied to the proportional solenoid in proportion to the command input signal V _p . Since this control device does not use a constant current amplifier, the structure of the control device is simple and adjustment is easy. Also, the fundamental period T
Since it has a component of the reciprocal of _p , that is, the fundamental frequency f _p , it also has the advantage that a so-called dither effect can be obtained.

However, in this conventional control device, when the resistance value of the proportional solenoid 13 changes due to temperature etc., the average current supplied to it also changes, and it is difficult to supply a current proportional to the command input signal to the proportional solenoid 13. The disadvantage is that it cannot be done.

An object of the present invention is to eliminate these drawbacks of conventional control devices, to be able to supply a current according to a command value to a proportional solenoid even if the resistance value of the proportional solenoid changes, and to have a simple configuration. The present invention provides a control device for an electromagnetic device having a proportional solenoid.

In order to achieve this object, the present invention takes in a value corresponding to the resistance value of the solenoid of the electromagnetic proportional control valve every predetermined period, extracts a correction value according to the value, and sets a command value for the electromagnetic proportional control valve. is multiplied by this correction value to create a new corrected command value, perform pulse width modulation with this new command value, and supply current to the solenoid of the electromagnetic proportional control valve according to this modulated pulse width. It is characterized by being configured as follows.

The present invention will be explained below based on the embodiment shown in FIG.

The same parts in FIG. 6 as those shown in FIG. 3 are given the same reference numerals, and their explanation will be omitted. 17 is a pulse width modulation amplifier corresponding to the drive amplifier 14 in FIG. A resistor 18 having a resistance value r is connected to the emitter of the transistor 16, and is connected in series with the proportional solenoid 13, through which the same current flows. The resistance value r is selected to be smaller than the resistance value R of the proportional solenoid 13, and a voltage V _r proportional to the passing current I
(V _r =I·r) is generated. Reference numeral 19 denotes a sample and hold circuit that takes in the voltage V _r generated by the resistor 18 and holds it. 20 is a sample and hold command signal generator that generates a signal S at every predetermined period, and its period is synchronized with the fundamental period T _p of the pulse width modulator 15 (see FIG. 4 or FIG. 5); The generated signal S is sent to the sample hold circuit 19
is input to. Signal S has high level H and low level L
The sample and hold command signal generator 20 generates a high level signal S in a certain basic period T _p , becomes a low level signal S after the elapse of the basic period T _p , and returns to the basic period after a predetermined period. T
The operation of generating the high level signal S for only period _p is repeated. The sample-and-hold circuit 19 takes in the voltage V _r from the resistor 18 only when the signal S from the sample-and-hold command signal generator 20 is at a high level H, and when the signal S is at a low level L, it takes in the voltage already taken in. Outputs _Vr1 .

21 is the voltage V from the sample hold circuit 19
This is a function generator that generates a correction coefficient signal K that corrects a change in the resistance R of the proportional solenoid 13 based on the input of _r1 . FIGS. 7a to 7c are characteristic diagrams illustrating the correction coefficient K. Figure a shows the characteristics of the passing current I with respect to changes in the resistance value R of the proportional solenoid 13. For example, the passing current I _p when the resistance value R _p is I
_p =E _p /R _p +r. Here E _p is constant voltage source 1
1 output voltage. On the other hand, Figure b shows the characteristics of the voltage V _r generated in the resistor 18 with respect to changes in the resistance value R of the proportional solenoid 13, and shows the voltage V _r generated in the resistor 18 when the current I _p as shown in Figure A flows.
_p (V _rp =I _p ·r). The characteristics of the voltage V _r with respect to the resistance R are the same as those of the current I in Figure a.
Figure c shows the output voltage V _r1 of the sample and hold circuit 19.
This is a characteristic diagram showing the value of the correction coefficient K for the function generator 21, that is, a characteristic diagram of the function generator 21. When the output voltage from the sample and hold circuit is, for example, a voltage V _rp as shown in Figure b, the output of the function generator 21 It is shown that the correction coefficient, which is a signal, is K _p . If the reference value of the resistance R of the proportional solenoid 13 is determined as R _p shown in Figures a and b, then Figure c
The correction coefficient K _p is 1. Here, we will look at the function of the correction coefficient K and the input voltage V _r1 .

Now, if the resistance value of the proportional solenoid 13 changes from R _p to (R _p +ΔR) due to an increase in temperature, the passing current also changes from I _p to (I _p +ΔI). That is, (I _p +ΔI)=E _p /R _p +ΔR+r……
... (1) As a result, the voltage V _r also changes from V _rp (V _rp + ΔV _r )
Changes to That is, (V _rp +ΔV _r )=E _p・r/R _p +ΔR+r…
…………(2) Here, in order to prevent the passing current I _p from changing even if the resistance value R of the proportional solenoid changes from R _p by ΔR, the correction coefficient K is used to calculate (I _p +ΔI)
must be corrected. That is, (I _p +ΔI)×K=K・E _p /R _p +ΔR+r=E
_p /R _p +r……… (3) From equations (2) and (3), K=R _p +ΔR+r/R _p +r=E _p・r/(R _p +r
) (V _rp + ΔV _r )……… (4) Since the resistance value R _p , r, and the voltage E _p are constants, E _p・r/R _p + r = k………(5
). (k is a constant) From equations (4) and (5), K=k/(V _rp +ΔV _r )…………(6
) becomes. By the way, since (V _rp + ΔV _r ) is nothing but the new output signal V _r1 taken in by the sample-and-hold circuit 19 in response to the changed resistance value of the proportional solenoid 13, equation (6) is expressed as K=k/V _r1 ... ………(7) becomes. That is, the function generator 21 outputs a correction coefficient signal K that satisfies equation (7) with respect to its input voltage V _r1 . The characteristic diagram in FIG. 7c shows this relationship.

Continuing the explanation of the configuration shown in FIG. 6 again, 22
is the command input signal V _p to the electromagnetic proportional pressure reducing valve 1
This is a multiplier that multiplies the correction coefficient signal K from the function generator 21 by the correction coefficient signal K from the function generator 21. Output signal from multiplier 22
KV _p is a command signal obtained by correcting the command input signal V _p with a correction coefficient K for a change in the resistance value R of the proportional solenoid 13. Reference numeral 23 denotes a switching device that performs a switching operation based on the output signal S of the sample and hold command signal generator 20. That is, when the output signal S is at the low level L, the switching device 23 inputs the corrected command signal KV _p to the pulse width modulator 15, and output V modulated to a pulse width corresponding to the command signal KV _p . generate _p . Conversely, the output signal S is at a high level H
, the switching device 23 cuts off the input of the command signal KV _p to the pulse width modulator 15, and during that time the output of the pulse width modulator 15 is set to a high level H (that is, the modulation degree D is set to 100%). ) generate a signal.

Next, the operation of this embodiment will be explained with reference to the time chart shown in FIG.

Now, at time _t1 , when the output signal S of the sample and hold command signal generator 20 becomes high level,
This high level continues until time _t2 , ie, during the fundamental period _Tp . Due to the high level output signal S, the switching device 23 cuts off the output signal KV _p of the multiplier 22 and sets the modulation degree D of the PWM signal V _p of the pulse width modulator 15 to 100%. Therefore, the PWM signal V
_p during one period T _p from time t ₁ to time t ₂ , Fig. 8a
The level becomes high level 24 as shown in . During this period, transistor 16 is conductive and current is supplied to proportional solenoid 13. Since this current is pulsating as shown in FIG. 5, the voltage V _r generated across the resistor 18 also gradually increases from time t ₁ as shown in part 25 of the voltage waveform in FIG. 8 c. Then, after a certain period of time determined by the characteristics of the proportional solenoid itself, it reaches a constant value as shown in section 26.

On the other hand, upon input of the high-level output signal S from the sample-and-hold command signal generator 20, the sample-and-hold circuit 19 changes from a holding state in which it holds the previously captured voltage to a capturing state in which it captures a new voltage. FIG. 8d shows the waveform of the voltage V _r1 taken in by the sample and hold circuit 19 (that is, this voltage V _r1 becomes the output voltage of the sample and hold circuit 19) before time t ₁ . In the holding state, as shown by a portion 27, the voltage taken in last time is held constant. At time _t1 , it is in the capture state, so the voltage value captured by the sample and hold circuit 19 is the voltage V shown in Figure c.
It changes in exactly the same way as _r , gradually increases as shown in section 28, and reaches a constant value in section 29.

At time _t2 , the output signal S of the sample and hold command signal generator 20 changes from a high level to a low level, as shown in Figure b. At this time, the sample and hold circuit 19 also changes from the capture state to the hold state, and holds the constant voltage shown in part ₂₉ of _FIG . to hold this voltage. On the other hand, since the signal S has become low level, the switching device 23 enters a state in which the signal KV _p from the multiplier 22 is input to the pulse width modulator 15.

Here, the new voltage V _r1 taken in by the sample and hold circuit 19 is input to the function generator 21, and the function generator 21 generates a correction coefficient signal corresponding to this voltage V _r1 according to the characteristics shown in FIG. 7c. Output K. Multiplier 22 generates a corrected command input signal KV _p by multiplying command input signal V _p by correction coefficient signal K, and inputs this signal to pulse width modulator 15 via switching device 23 . The pulse width modulator 15 outputs a PWM signal V _p having _a pulse width T ₃ corresponding to the signal KV _p as shown in FIG. The modulation degree D ₂ in this case is D ₂ = T ₃ /T _p
×100%, and as shown in Figure 8a, the modulation degree
The PWM signal V _p which is D ₂ is continuously outputted until time t ₃ . In this way _, from _time t _{2 to} time t ₃ , _the proportional solenoid 1
3 is supplied with the desired current.

At time t ₃ , as at time t ₁ ,
During one period T _p, the amplifier 17 enters the state of taking in the voltage V _r , and after time t ₄ after one period, the command input signal V _p is controlled by the correction coefficient signal K corresponding to the newly taken in voltage V _r1 . The supply current is controlled by driving the transistor 16 with a PWM signal V _p having a modulation degree D ₃ and having a pulse width (T ₄ ) corresponding to the corrected signal KV _p as shown in FIG. 8a. It will be done. Note that D ₁ in Figure 8a is before time t ₁ .
It shows the modulation degree of the PWM signal V _p .

In the above explanation, an electromagnetic proportional pressure reducing valve was exemplified as an electromagnetic proportional control valve to which the control device of this embodiment is applied, but this embodiment is not limited to such a pressure reducing valve. It can be applied to variable throttle valves in which a spring is provided to apply a reaction force to the end surface 5b of the spool 5 and the small hole 5c in the spool 5 is eliminated, and other types of control valves.

In this way, in this embodiment, a signal corresponding to the resistance value of the proportional solenoid is taken in during one cycle of the PWM signal, and the command input signal to the electromagnetic proportional control valve is corrected by a correction coefficient corresponding to this signal.
Since the current value supplied to the proportional solenoid is controlled by a PWM signal corresponding to the corrected signal, it is possible to always supply a current that generates the desired force to the proportional solenoid with a simple configuration.
Therefore, control accuracy can be improved.

In the embodiments described above, an electromagnetic proportional control valve was exemplified as an electromagnetic device having a proportional solenoid, but the present invention is not limited to an electromagnetic proportional control valve.
This can be applied to any electromagnetic device that has a proportional solenoid.

Furthermore, in the sample and hold command signal generator, the period during which the output signal is at a high level can be set by either automatic means or manual means, and the period during which the output signal is at a high level can be set by the proportional solenoid. If the inductance is large and it takes a long time for the voltage value to reach a certain value, it is possible to select an integer multiple of the fundamental period.

Furthermore, by storing correction coefficients corresponding to the input voltage in the function generator in a memory (ROM), the control device of the present invention can be configured with a microcomputer.

Furthermore, the element for controlling conduction or non-conduction of the current in the proportional solenoid is not limited to a transistor, and other elements such as a thyristor may also be used.

As described above, in the present invention, a value corresponding to the resistance value of the proportional solenoid is inputted every predetermined period,
A correction value is obtained from this value, the command value for the electromagnetic device is corrected with this correction value, and the current value supplied to the proportional solenoid is controlled by a PWM signal modulated by this corrected command value, so it is easy to use. With this configuration, a current can always be supplied to the proportional solenoid according to the command value, and the accuracy of control over the electromagnetic device can be improved.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an electromagnetic proportional pressure reducing valve, Fig. 2 is a block diagram of a conventional control device for an electromagnetic proportional pressure reducing valve, Fig. 3 is a block diagram of another conventional control device for an electromagnetic proportional pressure reducing valve, and Fig. 4 is a block diagram of a conventional control device for an electromagnetic proportional pressure reducing valve. The figure is a waveform diagram for explaining the operation of the pulse width modulator shown in Figure 3, Figure 5 is a waveform diagram of the current flowing through the proportional solenoid shown in Figure 3, and Figure 6 is a waveform diagram for explaining the operation of the pulse width modulator shown in Figure 3. A block diagram of the control device for the electromagnetic proportional pressure reducing valve, FIGS. 7a to 7c are characteristic diagrams for explaining the contents of the function generator shown in FIG. 6, and FIGS. 8a to d are the control shown in FIG. 6. This is a time chart for explaining the operation of the device. 13... Proportional solenoid, 15... Pulse width modulator, 16... Transistor, 18... Resistor, 1
9...Sample hold circuit, 20...Sample hold command signal generator, 21...Function generator,
22... Multiplier, 23... Switching device.

Claims (1)

[Claims] 1. Means for inputting a value corresponding to the resistance value of the proportional solenoid of the electromagnetic device every predetermined period, means for calculating a correction value corresponding to the resistance value based on the input value, and a command value for the electromagnetic device. means for multiplying the reference pulse by the correction value, means for modulating the pulse width of the reference pulse according to the new command value obtained by the multiplication means, and controlling the proportional solenoid of the electromagnetic device to adjust the modulated pulse width to and means for supplying a corresponding current.