JPH01193486A - Drive circuit for electromagnetic hydraulic controlling valve - Google Patents

Abstract

PURPOSE:To lessen hysteresis while stabilizing the operation of an electromagnetic hydraulic controlling valve by heightening the frequency of dither signal when the opening of said controlling valve is small and lowering that when said opening is large. CONSTITUTION:The drive circuit 22 of an electromagnetic hydraulic controlling valve 20 is constituted from an oscillating circuit 50, adding circuit 2, current amplifying circuit 3 and offset circuits 51, 52. The frequency of dither signal generated by an oscillation circuit 50 is heightened when the opening of the valve is small and lowered when same is large. Thus, in the control pressure property for the input current of said electromagnetic hydraulic controlling valve 20, the hysteresis can be lessened over the whole region, while variation in the control pressure is not caused by the dither even when the opening of the valve is small and the operation of said valve can be stabilized.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a drive circuit for an electrohydraulic control valve that supplies a current to the electrohydraulic control valve according to a voltage that is the sum of a command voltage and a dither signal. It is.

(Prior Art) As a conventional drive circuit of this type, there is one shown in FIG. 7, for example. This circuit is composed of an oscillation circuit 1, an adder circuit 2, and a current amplification circuit 3.

The oscillation circuit 1 includes a differential amplifier 4, resistors 5, 6, 7, and a capacitor 8, and generates a dither signal.

The adder circuit 2 includes a differential amplifier 9, resistors 10, 11 and 12.
Its input terminal is coupled to the drive voltage input terminal p via a resistor 10, and further coupled to the output terminal of the oscillation circuit 1 via a resistor 11. The other input end is grounded through a resistor 12, and the output end is connected to that input end through a resistor 13.

The current amplification circuit 3 includes a differential amplifier 14 and a transistor 15.
and a resistor 16, the input terminal of the differential amplifier 14 is connected to the output terminal of the differential amplifier 9, and the output terminal of the differential amplifier 14 is connected to the base of the transistor 15. Its collector is connected to the coil 16 of the solenoid of the electrohydraulic control valve, and its emitter is grounded via a resistor 17. The other input terminal of the differential amplifier 14 is connected to the junction between the emitter of the transistor and the resistor 17. Coil 16 is also connected to DC power supply 18 . Next, the operation of this drive circuit will be explained.

First, a command voltage V based on the command pressure is applied to the drive voltage input terminal p.
Apply IN. The command voltage VIN is added to the dither signal Vll+, which is output from the oscillation circuit 1 and has a constant amplitude and frequency, in the differential amplifier 9, and is output as a voltage signal v1. The differential amplifier 14 of the current amplification circuit 3 that receives this voltage signal V supplies a current I corresponding to the voltage signal v1 to the solenoid coil 16 of the electrohydraulic control valve via the transistor 15.

Therefore, the solenoid current I corresponds to the command voltage VIN plus the dither signal voltage VDI.

Adding a dither signal to the command voltage in the drive circuit in this way is a method used to adjust the hysteresis in the characteristics of the control pressure with respect to the current of the electrohydraulic control valve. The lower the value, the smaller the hysteresis.

(Problem to be Solved by the Invention) However, in this type of conventional drive circuit, the amplitude and frequency of the dither signal are kept constant, so the pressure gain of the pilot valve has nonlinear characteristics (see Figure 8). In other words, in the region where the valve opening of the control valve is small, the gain of the pilot pressure pp with respect to the poppet displacement Xp is large, and in the region where the valve opening is large, the gain is small. If the frequency of the dither signal is set relatively high so as not to cause pressure fluctuations in the control pressure Pc in response to fluctuations in pp, the frequency of the dither signal is increased on the large side of the valve opening, where fluctuations in the pilot pressure pp due to dither are small. On the other hand, if the frequency of the dither signal is set relatively low so that the hysteresis becomes small on the large side of the valve opening, the fluctuation of the pilot pressure pp due to dither will be large on the small side of the valve opening, and There is a problem in that pressure fluctuations occur in the responsive control pressure Pc (see the current-control pressure characteristics in FIG. 6).

(Means for Solving the Problems) The present invention aims to provide a drive circuit for an electromagnetic hydraulic control valve that does not cause such problems, and includes an oscillation circuit,
Driving an electrohydraulic control valve that has an addition circuit and a current amplification circuit and supplies a current corresponding to the voltage that is the sum of the command voltage and the dither signal to the electrohydraulic control valve that generates control pressure according to the input current. The circuit is characterized in that the frequency of the dither signal output from the oscillation circuit is high when the valve opening of the electrohydraulic control valve is small, and low when the valve opening is large.

(Function) Based on the command pressure (command voltage (VI
When N) is applied, the oscillation circuit generates a dither signal (VB2) with a constant amplitude and a high frequency (VB2) on the small side of the valve opening of the control valve and a low frequency on the large side of the valve opening. , ) and the command voltage (VIN) is input to the current amplifier circuit, the current amplifier circuit calculates the added voltage (VI
An electric current m (Is) corresponding to N + Voz) is supplied to the solenoid coil of the electrohydraulic control valve. In this way, it is possible to reduce the hysteresis over the entire control pressure characteristic with respect to the input current of the control valve, and there is no pressure fluctuation in the control pressure due to dither even when the valve opening is small, and the operation of the control valve is reduced. can be stabilized.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a drive circuit and an electrohydraulic control valve using the drive circuit according to a first embodiment of the present invention. 20 in the diagram
The supply pressure P applied to the supply port 21 by the electromagnetic hydraulic control valve is controlled by the drive circuit 22, and the control pressure Pc is outputted from the output port 23. 24 is a solenoid plunger, 16 is a solenoid coil, and 25 is a pilot valve (poppet valve), which are integrally installed. 26 is an orifice provided between the oil chamber 27 and the pilot chamber 28 and opened and closed by the poppet valve 25.

The oil chamber 27 is connected to the drain port 30 through an oil passage 29, and the pilot chamber 28 is connected to an oil passage 32 through an orifice 31.
It is connected to the supply port 21 by. Drain port 30
A tank 33 is connected to. 34 is a main spool, which stops at a position where the oil pressure in the pilot chamber 28 and the oil pressure in the reaction force chamber 35 are balanced. The reaction force chamber 35 is an orifice 36
Output port (control port) 23 via oil passage 37
connected to.

Next, the drive circuit 22 will be explained in detail. The drive circuit 22 includes an oscillation circuit 50, an adder circuit 2, a current amplification circuit 3, and offset circuits 51 and 52. Here, since the adder circuit 2 and the current amplification circuit 3 are the same circuits as in the conventional example, they are given the same reference numerals as in FIG. 7 and their explanation will be omitted.

The offset circuit 51 includes a differential amplifier 53 and a resistor 54 connected between its negative input terminal and a drive voltage input terminal p.
, a resistor 55 connected between the other input terminal and the output terminal, a series circuit of resistors 56 and 57 coupled to the input terminal, and a junction point of these resistors and an intermediate tap of a variable resistor 58. It consists of a resistor 59 connected between the two. An offset voltage vA is applied to one end of the variable resistor 58, and the other end and the resistor 57 are grounded. This circuit generates a voltage VC adjusted by applying an offset to the command voltage VIM so that the next-stage anti-oscillation circuit 50 can easily generate dither.

The oscillation circuit 50 is a voltage controlled oscillator, and resistors 60 (R,) and 61 are connected to its input terminal. 62 is a differential integrator, the input end of which is connected to the other end of the resistor 60 and the junction of the resistor 61 and the resistor 63 whose one end is grounded; It is connected to the collector of the transistor 66 via the terminal 66 and at the same time to the input terminal of the comparator 67. The other input end of the comparator 67 is connected to a junction between a resistor 68 (R2) and a resistor 69 (R3) whose one end is grounded, and a resistor 70 is connected to its output end. The other end of the resistor 70 is connected to the resistor 68 and the resistor 71, and a voltage V is applied thereto. The other end of the resistor 71 is connected to the base of the transistor 66 and a diode 72 whose one end is grounded. The emitter of transistor 66 is grounded.

52 is an offset circuit, which is the same as the offset circuit 51 except that the polarity of the differential amplifier 53 is inverted, so the same reference numerals are given and the explanation will be omitted. Next, electrohydraulic control valve 2
The effect of 0 will be explained.

When a current (2) is input from the drive circuit 22 to the solenoid coil 16, the plunger 24 generates a thrust force proportional to the current value in the left direction in the drawing. This thrust causes the pilot valve 25 to move in the direction of closing the lance varnish 26. As a result, the flow rate passing through the orifice 26 decreases, and the differential pressure between the supply pressure P3 and the pilot pressure P also decreases, and the pilot pressure PP
will rise. At this time, the pilot valve 25 stops at a position where the force pushed back by the pilot pressure P and the thrust of the solenoid are balanced, so the pilot pressure can be adjusted by the input current I3 of the solenoid.

The main spool 34 moves to the left due to the increase in the pilot pressure Pp, and connects the supply port 21 and the control port 23. As a result, the control pressure Pc also increases, and the pressure in the reaction force chamber 35 also increases through the oil passage 37 via the orifice 36, causing the main spool 34 to move in the opposite direction. As a result, the control port 23 and the drain 30 are connected, and the control pressure PC1 and the pressure in the reaction force chamber decrease. At this time, the main spool 34 stops at a position where the product of the feedback pressure P and the feedback pressure receiving area S2 of the main spool is equal to the product of the pilot pressure PP and the pilot pressure receiving area S1, so the control pressure pc is equal to the pilot pressure PP. controlled to be equal. Therefore, the control pressure Pc can be controlled by the input current I of the solenoid.

Next, a drive circuit 22 that controls the input current I of the solenoid.
Explain the effect of

First, based on the command pressure (command voltage VI
When N is applied, this command voltage VIN is input to the differential amplifier 9 of the adder circuit 2 and simultaneously input to the differential amplifier 53 of the offset circuit 51. In response to this, the offset circuit 51 uses the command voltage v4 based on the offset voltage vA.
The voltage VC adjusted by adding an offset to the oscillation circuit 50
differential integrator 62.

The differential integrator 62 repeats charging and discharging based on this voltage vc, and supplies the comparator 67 with a triangular wave vX such that the amplitude of the output voltage is equal to the hysteresis width VTII of the comparator 67. As a result, the comparator 67 outputs a pulse VOZ which becomes a high potential and a low potential according to the triangular wave vX.
occurs. This pulse, that is, the dither signal V! l! The frequency f is given by the following equation. It is assumed that the duty cycle of the rectangular wave vnz is a constant value (for example, 50%). Therefore, the oscillation frequency f of the dither signal VOZ can be changed according to the command voltage Vl11.

The dither signal is added to the command voltage VIN in the adder circuit 2,
The polarity is inverted and input to the offset circuit 52. Upon receiving this, the offset circuit 52 adjusts the voltage based on the offset voltage vA, and based on the voltage, the current amplifier circuit 52 adjusts the voltage.
supplies the solenoid current I3 to the solenoid coil 16. In addition, the voltage VIN% C% VO2 mentioned above
, (VIN+VDZ) are shown in FIGS. 5(a) to 5(d). As is clear from this figure, the input voltage of the current amplification circuit 30 is dithered so that the frequency decreases when the command voltage VIN and the command voltage are low (valve opening is large), and the frequency increases when the command voltage is high (valve opening is small). This corresponds to the signal VO2, and therefore the input current-control pressure characteristic can be made into a desired one with small hysteresis as shown in FIG.

2 to 4 are the first to fourth embodiments of the present invention, respectively.
FIG. 2 is a diagram showing the configuration of only a different part (electrohydraulic control valve) from the embodiment.

The electrohydraulic control valve of the second embodiment shown in FIG. 2 has a two-stage structure on the left side of the main spool 38, and the valve body 38 has a two-stage structure.
A reaction force chamber 40 and a back pressure chamber 41 are defined within the back pressure chamber 4.
1 to the back pressure port 42. The back pressure chamber 41 is supplied with back pressure from a tank 43 connected to a back pressure boat 42 .

The electrohydraulic control valve of the third embodiment shown in FIG. 3 is obtained by replacing the reaction force chamber 40 and the back pressure chamber 41 of the control valve of the second embodiment with appropriate adjustment of the cross-sectional area.

The electrohydraulic control valve of the fourth embodiment shown in FIG. 4 has a back pressure chamber 41 and a drain boat 30 in the valve body 39 instead of providing the back pressure port 42 and the tank 43 in the control valve of the second embodiment. An oil passage 44 is provided to communicate the two.

With this configuration, in the second to fourth embodiments, the effects described later can be obtained, and the dithering effect of the first embodiment can be further enhanced. That is, since the feedback pressure receiving area S2 is set to be significantly smaller than the pilot pressure receiving area S, the control range of the pilot pressure P is limited while ensuring the same pressure control range of the control pressure P as in the first embodiment. can do. This allows the cross-sectional area of the orifice 26 to be reduced, and also allows the solenoid current to be reduced.

(Effects of the Invention) Thus, as described above, the electrohydraulic control valve drive circuit of the present invention uses a dither signal with a frequency that is high when the valve opening of the control valve is small and becomes low when the valve opening is large to the command voltage. Since the solenoid current is controlled by the applied voltage, the input current of the control valve -
The hysteresis of the control pressure characteristics can be made small over the entire range, and the operation of the control valve can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a drive circuit according to an embodiment of the present invention and an electromagnetic hydraulic control valve using the drive circuit, and FIGS. Diagrams showing the configuration of only the different parts, Figures 5(a) to (d) are waveform diagrams showing voltage waveforms of each part of the drive circuit of the present invention, and Figure 6 is a characteristic showing the relationship between control pressure and input current. 7 is a diagram showing the configuration of a conventional electrohydraulic control valve drive circuit, and FIG. 8 is a characteristic diagram showing the relationship between poppet displacement and pilot pressure. 1...Oscillation circuit 2...Addition circuit 3...Current amplification circuit 16...Solenoid coil 20...
- Electromagnetic hydraulic control valve 21... Supply boat 22... Drive circuit 23... Output boat 24... Plunger 25... Pilot valve (poppet valve) 26... Orifice 28... Pilot chamber 30.・・Drain boat 34.38・・Main spool 35.40・
... Reaction force chamber 39 ... Valve body 41 ... Back pressure chamber
42... Back pressure boat 50... Oscillation circuit
51.52...Offset circuit 53.62...Differential amplifier 60...Resistor (R1) 62...Differential integrator 64...Capacitor (C3) 66...Transistor 67... Comparator 68...Resistance (
R,) 69...Resistance (R3) Patent Applicant: Nissan Motor Co., Ltd. Representative Patent Attorney Akihide Sugimura

Claims (1)

[Claims] 1. It has an oscillation circuit, an addition circuit and a current amplification circuit,
In a drive circuit for an electrohydraulic control valve that supplies a current corresponding to a voltage obtained by adding a command voltage and a dither signal to an electrohydraulic control valve that generates control pressure according to an input current, 1. A drive circuit for an electrohydraulic control valve, characterized in that the frequency of the dither signal is high when the valve opening of the electrohydraulic control valve is small, and becomes low when the valve opening is large.