JPS59228703A - Driving circuit of electromagnetic apparatus equipped with proportional solenoid - Google Patents

Abstract

PURPOSE:To avoid the possibility of a danger of an apparatus controlled by an electromagnetic apparatus equipped with a proportional solenoid even if a failure occurs in a pulse generator by providing a limitter and a failure discriminator. CONSTITUTION:A limitter 18 is provided to a pulse generator (an PWM generator) in order to prevent a modulation degree from being 0% and 100% and an output of the PWM generator 16 is checked by a failure discriminator 19 provided to an output selector 17 to discriminate existence of a failure of the PWM generator and a predetermined current of a proportional solenoid 15 is supplied or interrupted when the failure of the PWM generator 16 occurs. With this constitution, even if a failure occurs in the PWM generator 16, the possibility of a danger of an object being controlled by a proportional electromagnetic valve equipped with the proportional solenoid 15 can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for an electromagnetic device equipped with a proportional solenoid used in various control devices by operating in proportion to an input current value.

As an example of a control device using an electromagnetic device including such a proportional solenoid, a drive circuit for the electromagnetic device will be explained by exemplifying a regulator that controls the drive of a hydraulic pump in a hydraulic system.

FIG. 1 is a system diagram of a drive circuit for a conventional hydraulic pump regulator. In the figure, 1 is the operating lever of the hydraulic pump;
Reference numeral 2 denotes an operation amount detection device that detects the operation amount of the operating lever 1 and outputs a signal X corresponding to the operation amount. Reference numeral 3 denotes a pulse generator (hereinafter referred to as a PWM generator) that generates a pulse having a pulse width modulated according to the output signal X of the manipulated variable detection device 2. 4 is an amplifier that outputs a current t, which is the same as the PWM signal output from the PWM generator 3; Reference numeral 5 denotes a proportional solenoid valve, which is composed of a proportional solenoid section 5α and a pressure reducing section 5b, which operate according to the current i. 6 is an auxiliary hydraulic pump, 7 is a tank, and 8 is a hydraulic cylinder constituting a regulator of a main hydraulic pump (not shown). Hydraulic cylinder 8 has piston 9 and piston rod 1
0 and a spring 11, and the piston rod 10 is connected to a drive mechanism that drives the swash plate and the like of the main hydraulic pump.

Here, the PWM generator 3 will be explained in more detail with reference to FIG.

FIG. 2 is a block diagram of the PWM generator shown in FIG. 1. In the figure, 12 is a triangular wave generator that generates triangular wave 2;
is a comparator that compares the voltage values of the signal X and the triangular wave 2. Comparator 13 outputs a constant voltage when the value of signal X is greater than the value of triangular wave 2, and does not generate an output when the value of triangular wave 2 exceeds the value of signal X. The operation of this comparator 13 will be explained with reference to FIGS. 3(cL) and (&).

FIGS. 3(α) and (b) are input/output waveform diagrams of the comparator shown in FIG. 2, in which the horizontal axis represents time and the vertical axis represents voltage. The triangular wave 2 output from the triangular wave generator 12 is
As shown in the figure (α), it has a waveform that changes linearly from voltage 0 to voltage Eo (o4z4go) during period 'ro. Now, the value of signal X is voltage O and voltage E. Suppose that the value of the signal Then, as is clear from the figure (α), the period T. There is a period in which the value of the voltage E becomes larger than the value of the triangular wave 2 and a period in which it becomes smaller. The comparator 13 outputs the voltage E1 when the voltage E□ is equal to or higher than the value of the triangular wave 2, and does not output when the value of the triangular wave 2 exceeds the voltage E. This is shown in FIG. 3(b). That is, the period T. During all periods, the voltage E1 is output during the period T, and the voltage 0 is output during the period T. When the value of the signal
When n increases and the value of the signal X becomes smaller than the voltage E, the period "011" decreases in proportion to the value of the signal Now, if the ratio of the period "on" to the period To is the pulse width modulation degree (PWM modulation degree) D, then D = Too/71' oX 100 (%). The pulse output signal y modulated in this manner is input to an amplifier 4, which outputs a current t proportional to this pulse width. Here, the configuration of the amplifier 4 will be explained using diagrams.

FIG. 4 is a circuit diagram of the amplifier shown in FIG. 1.

In the figure, reference numeral 14 denotes a power transistor constituting the amplifier 4, whose base is connected to the B &'iP W M generator 3 to which the signal y is input, and whose emitter E is grounded. Further, the collector C is connected to one end of the proportional solenoid 15 of the proportional solenoid section 5α.

A power supply voltage E2 is applied to the other end of the proportional renoid 15. When the input signal y is y=o, the power transistor 14 is in a non-conducting state, and when the input signal y is y=E□, the power transistor 14 is in a conducting state. When the power transistor 14 is in a non-conducting state, no current is supplied to the proportional solenoid 15, so the proportional solenoid valve 5 does not operate, but when the power transistor 14 is in a conducting state, no current is supplied to the proportional solenoid 15. JFE2/R (However,
A current (R is the resistance value of the proportional solenoid 15) flows, and the period is T. The average current amount ■1 at is ■, -■. , Ton/T.

becomes. If this relationship is expressed with the current 11 on the vertical axis and the PWM modulation degree on the horizontal axis, it will be as shown in the graph shown in FIG.

Here, the operation of the conventional drive circuit shown in FIG. 1 will be explained. When the operating lever 1 is operated to drive the main hydraulic pump, the operating amount detection device 2 outputs a signal X corresponding to the operating amount. This signal X is input to the PWM generator 3, which outputs a pulse signal y having a pulse width modulated according to the signal It will be supplied to the proportional solenoid 15. When the proportional solenoid 15 is excited by the current t, the proportional solenoid valve 5 outputs a hydraulic pressure P1 proportional to the current t, and this hydraulic pressure P1 is applied to the head side of the cylinder 8 to spring the piston 9 and the piston rod 10. 11 and move to the right. This movement of the piston rod 10 to the right causes the main hydraulic pump ρ swash plate to tilt, and in response, pressure oil is discharged from the main hydraulic pump. piston rod 10
The amount of movement is proportional to the oil pressure P1, and the tilting of the swash plate is proportional to the amount of movement of the piston rod 1o, so in the end, pressure oil is discharged from the main hydraulic pump in accordance with the amount of operation of the operating lever 1. become.

By the way, if a failure such as breakage occurs in the PWM generator 3 in the drive circuit, the output of the PWM generator 3 will be in a continuous ON state or a continuous OFF state. For example, if the ON state continues, the Bonpregator maintains the tilting amount of the swash plate at the maximum, so the output of the main hydraulic pump will continue to be in the maximum state, and the drive source of the main hydraulic pump will A certain prime mover stops abnormally. In this case, depending on the actuator being driven by the main hydraulic pump, it is easy to predict that an extremely dangerous situation may occur due to the continuation of the maximum output of the hydraulic pump and the abnormal stop of the prime mover. Conversely, if the OFF state continues, pressure oil will not be discharged from the main hydraulic pump, making it impossible to move the actuator driven by the main hydraulic pump, and as in the case above, depending on the condition of the actuator. Creates a hazardous situation. In the above description, the proportional solenoid valve 50 controls the pump regulator, but it is not necessarily limited to the pump regulator, and there are many control objects that are in use. Therefore, it is naturally expected that there are various types of risks that occur when a PWM generator failure causes its output to become continuously ON or continuously OFF, making it impossible to control the controlled object. Ru.

The present invention was made in view of the above circumstances, and its purpose is to prevent the occurrence of danger in a device controlled by an electromagnetic device equipped with a proportional solenoid even if a failure force occurs in a PWM generator. An object of the present invention is to provide a drive circuit for an electromagnetic device with a proportional solenoid.

To achieve this objective, the present invention limits the modulation depth of the PWM generator to a range greater than 0% and less than 100%.
The output of the WM generator is made to change within a predetermined period, and when the output of the PWM generator does not change within the predetermined period, this is detected and the safety maintenance device is activated by the detection signal. It is characterized by

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 6 is a system diagram of a drive circuit for a regulator of a hydraulic pump according to an embodiment of the present invention. In the figure, the same parts as those shown in FIG. 1 are given the same reference numerals. 16 is a PWM generator corresponding to the PWM generator 3 shown in FIG. 1, which inputs the output signal Output.

The configuration of the PWM generator will be explained in detail with reference to FIG.

FIG. 7 is a block diagram of the PWM generator shown in FIG. 6. In the figure, 12 is a triangular wave generator, and 13 is a comparator, which are the same as those shown in FIG. 18 inputs the output signal X of the manipulated variable detection device 2, and outputs a certain predetermined value when the value is 0 or a value close to 0;
That value is voltage E. Alternatively, when the value is close to the voltage Eo, the limiter outputs a predetermined value different from the predetermined value, and otherwise outputs the input signal as is. FIG. 8 shows a characteristic diagram of the limiter 18. In the figure, the horizontal axis shows the value of the input signal X to the limiter 18, and the vertical axis shows the value of the output signal l of the limiter 18. The input signal X is
In the range from the value O to the value E2 near O (o≦x4E-2), the limiter 18 outputs the voltage E2, and the input signal
Value E from value E3 near 0. In the range (E3≦X≦Eo), the limiter 18 outputs the voltage E3. And the value E
In the range exceeding 2 and below the value 83 (E2<-Zi<E3), the value of the input signal X is output as is. Due to the intervention of the rimming 18, the output y from the PWM generator 16
The modulation depth will never be 0% or 100%.

Returning to FIG. 6, 17 is the amplifier 4 and the proportional solenoid section 5α.
This is an output selector interposed between the The output selector 17 supplies current to the proportional solenoid 15 according to the signal from the amplifier 4, and also determines whether or not there is a failure in the PWM generator 16 based on the signal from the PWM generator 16, and performs appropriate processing. It also has functions. The configuration of the output selector 17 will be explained in more detail with reference to FIG.

FIG. 9 is a circuit diagram of the output selector shown in FIG. In the figure, the configurations of the amplifier 4 and the proportional solenoid section 5α are the same as those shown in FIG. Reference numeral 19 denotes a failure discriminator which inputs the output signal y of the PWM generator 16 and determines whether or not the PWM generator 16 is malfunctioning. The failure discriminator 19 is composed of, for example, a retriggerable single shot vibrator.

Here, the function of the fault discriminator 190 is shown in FIGS.
). The retriggerable single-shot high plater has 1
When one pulse 22 is input, the rising portion 228 of the pulse 22 generates an output at a predetermined level (14) as shown in FIG. 10(b). This output is shown at 24. After this output is continuously output for a predetermined period, the output becomes O (level L) when the period elapses. However, if a new pulse is input before the corresponding period has elapsed, the output of the retriggerable single shot-by-break continues to be at level H, and the predetermined value is changed from the time when the new pulse is input. After the period elapses, the output becomes O. That is, assuming that the predetermined period is 1, the output 24 generated by the pulse 22 becomes O (level L) as shown by reference numeral 25 after the period Tw has elapsed, but the output 24 becomes O (level L) as shown by the reference numeral 25 after the elapse of the period Tw. When a flat pulse 23 is input, the output 24 is triggered again at the rising edge 23S of the pulse 23, and the output 24 does not become O but remains at level H and continues as indicated by reference numeral 26. The period Tw is set to be slightly longer than 120 cycles T'' of the triangular wave generator.

Returning to FIG. 9, 20 is a resistor having a predetermined resistance value (this resistance value will be described later), and 21 is a changeover switch operated by the output of the fault discriminator 19. The changeover switch 21 has terminals S1 and S2, and the collector of the power transistor 14 in the amplifier 4 is connected to the terminal S.
Further, a resistor 20 is connected to the terminal S2. When the changeover switch 21 is connected to the terminal S1, the proportional solenoid 15
is connected to the power transistor 14, and the selector switch 2
1 is connected to terminal S2, proportional solenoid 15 is connected to resistor 20. The changeover switch 21 is a failure detector 19
When the output is at level H, it is connected to terminal S1, and when it becomes level L, it is switched to terminal S2.

Next, the operation of this embodiment will be explained. When the PWM generator 16 is in a normal state without any failure, when the operation lever 1 is operated, the operation amount detection device 2 outputs a signal X corresponding to the operation amount. This signal X is input to the limiter 18 to become a signal l according to the characteristics of the limiter shown in FIG. The width modulated pulse will be output as signal y. In this case, even if the input signal X of the PWM generator 16 is less than the voltage E2, the output from the limiter 18 will be the voltage E2, and even if the input signal X is more than the voltage E3, the output from the limiter 18 will be the voltage E2. It becomes E3. Therefore, the modulation of ratios of 0%, 100% and their vicinity is gone, and the signal y from the comparator 13 has a period T. There is always a rising edge of the pulse at the beginning of the pulse. The signal y' is input to the power transistor 14, which is turned ON and OFF according to the signal y, and as mentioned above, a current proportional to this is supplied to the proportional solenoid 15, and eventually the current is proportional to the amount of operation of the operating lever 1. The main hydraulic pump's swash plate is tilted to control its discharge amount. On the other hand, the signal y is also input to the failure discriminator 19. As mentioned above, the period Tw of the IJ) regula pull single shot vibrator constituting the fault discriminator 19 is adjusted to the period T by adjusting the capacitance and resistance values of the pipe rake.

The signal y has a period T.

Since each signal always has a rising edge, the output of the fault discriminator 19 is maintained at level I4. Therefore, the changeover switch 21 remains connected to its terminal S0,
Proportional solenoid 15 and power transistor 14 remain connected to allow normal control.

Next, if a failure occurs in the PWM generator 16, the output of the PWM generator 16 will remain at a high level (continuous ON state) or a low level regardless of the value of the signal It becomes a continuous state (continuous OFF state). Therefore, the signal y does not become a pulse output and has a period T. There is no leading edge of each pulse. As a result, the failure discriminator 19
The output cannot continue to be at a high level H and is at a low level L.
(failure detected), and the changeover switch 21 is switched from terminal S1 to terminal S2. Therefore, the proportional solenoid 15 is connected to the resistor 20, and a current of a value determined by its own resistance R1, the resistance value of the resistor 20, and the voltage E2 is supplied to the proportional solenoid 15, and the swash plate of the main hydraulic pump is also supplied with this. It is tilted accordingly.

Here, the resistance value of the resistor 20 will be described. As mentioned above, if the PWM generator 16 fails, the prime mover will abnormally stop if its output y becomes continuously ON, and the device driven by the main hydraulic pump will stop working if the output y becomes continuously OFF. , a dangerous situation may occur. In such a case, if the output of the main hydraulic pump is set to an intermediate level between the maximum and O, for example around 40%, it will prevent abnormal stoppage of the prime mover and malfunction of the equipment driven by the main hydraulic pump. Avoidable and dangerous or undesirable situations can be prevented. Therefore, if the resistance value of the resistor 20 is set so that the output of the main hydraulic pump is about 40%, even if a failure occurs in the PWM generator 16, the proportional solenoid 15 and the resistor 20 will be switched off by the changeover switch 21. When connected, the swash plate is tilted accordingly, and the output of the main hydraulic pump is reduced to about 40%, thereby avoiding the above-mentioned dangers and non-operation of the device.

It goes without saying that various resistance values are selected depending on the object controlled by the proportional solenoid valve 5 and the system controlled by the object. In other cases, the output oil pressure P1 of the proportional solenoid valve 5 is maximized by directly grounding the contact S2, and in other cases, the resistor 20 is removed and the contact S2 is opened to set the output oil pressure P1 of the proportional solenoid valve 5 to 0. In some cases.

In this way, in this embodiment, a limiter is provided in the PWM generator to prevent the modulation degree from becoming 0% or 100%, and a fault discriminator checks the output of the PWM generator to determine whether there is a fault. When the PWM generator fails, a specified current is supplied to the proportional solenoid or the current is cut off, so even if the PWM generator fails, danger to the object controlled by the proportional solenoid valve can be prevented. can.

As mentioned above, it goes without saying that the control target of an electromagnetic device equipped with a proportional solenoid is not limited to the regirator of a hydraulic pump, and there are many possible control targets.
Due to the absence of modulation degrees near 0% and 100% in the M generator, the range of current supplied to the proportional solenoid may become narrower, which may have some effect on the modulation. The part where there is no degree is O% as much as possible,
If it approaches 100%, the above effect will disappear to a large extent. If such an effect still causes an effect, the above effect can be removed by appropriately changing the spring constant, initial load, etc. of the object to be controlled by the proportional solenoid electromagnetic device. Furthermore, danger can be avoided even more reliably by activating a lamp, a buzzer, etc. to notify of a failure based on the output signal of the failure discriminator at the time of failure. Furthermore, the triangular wave generator and the comparator can be constructed from an analog circuit using an operational amplifier, a digital circuit using a counter, a microconbeater, or the like.

As described above, in the present invention, the degree of variation of the pulse width in the pulse output means is limited to less than 0% and less than 100%, and the output signal of the pulse output means is checked to see if there is a failure in the pulse output means. Since the safety maintenance device is activated in the event of a failure, even if a failure occurs in the pulse output means, danger to the object controlled by the electromagnetic device including the proportional solenoid can be prevented.

[Brief explanation of the drawing]

Figure 1 is a system diagram of the drive circuit of a conventional hydraulic pump regulator, Figure 2 is a block diagram of the PWM generator shown in Figure 1, and Figures 3 (a) and (b) are the comparator shown in Figure 2. Figure 8g4 is a circuit diagram of the amplifier shown in Figure 1, Figure 5 is a characteristic diagram of the current with respect to the modulation degree of the proportional solenoid shown in Figure 4, and Figure 6 is according to the embodiment of the present invention. System diagram of the hydraulic pump regulator drive circuit, Figure 7 is a block diagram of the PWM generator shown in Figure 6, Figure 8 is a characteristic diagram of the limiter shown in Figure 7, Figure 9 is shown in Figure 6. Circuit diagram of the output selector, FIG. 0 (α) and (b) are input/output waveform diagrams of the failure discriminator shown in FIG. 1... Operation lever, 2... Operation amount detection device, 4... Amplifier, 5... Proportional solenoid valve, 5α... Proportional Solenoid part, 8...
・Cylinder, 9...Piston, 10...
... Piston rod, 12 ... Triangular wave generator,
13... Comparator, 14... Power transistor, 15... Proportional solenoid, 1
6...PWM generator, 17...Output selector, 18...Limiter, 19...Failure discriminator, 20...Resistor , 21...changeover switch. Figure 2 Figure 3 Figure 5 Figure 8 Tw 26 1F

Claims (1)

[Claims] 1. Pulse output means for outputting a pulse with a pulse width modulated with a modulation degree according to an input signal, and a current according to the pulse width of the pulse outputted by the pulse output means. In the device comprising a current output means and an electromagnetic device having a proportional solenoid controlled according to the current value outputted by the current output means, the degree of modulation is set to 0% (100%).
%, a detection means for detecting when the output signal of the pulse output means does not change within a predetermined period, and a safety maintenance device activated by the detection signal of the detection means. A drive circuit for an electromagnetic device equipped with a characteristic proportional solenoid. 2. An electromagnetic device equipped with a proportional solenoid according to claim 1, wherein the safety maintaining device is a driving means for driving the proportional solenoid without depending on the output current of the current output means. drive circuit. 3; IP! f. In claim 1, the safety maintaining device is a driving means for driving the proportional solenoid and a notification means operated by an output signal of the detecting means without depending on the output current of the current output means. A drive circuit for an electromagnetic device equipped with a proportional solenoid. 4. In claim 2 or 3, the driving means includes a resistor having a predetermined value and a switching means for switching the proportional solenoid from the current output means to the resistor based on the output signal of the detection means. A drive circuit for an electromagnetic device equipped with a proportional solenoid, characterized by comprising: 5. According to claim 2 or 3, the driving means includes a proportional solenoid, characterized in that the driving means is a switching means that opens an input end of the proportional solenoid in response to an output signal of the detecting means. Drive circuit for electromagnetic devices.