JPH043904A - Solenoid driving circuit - Google Patents

Abstract

PURPOSE:To surely avoid a collision of a plunger against a magnetic pole by a method wherein a second control voltage corresponding to a difference between a detected voltage and a certain reference voltage is added to a first control voltage, and when a voltage peak detecting signal is accepted, a current supplied to a solenoid coil is intercepted during the time which is inversely proportional to a control voltage for a timer. CONSTITUTION:An electric current is supplied to a solenoid coil 2 from a main power source 12 and a detected voltage V1 generated on both ends of a resistor (voltage detecting means) 13 is divided to be inputted in a peak detector 4 and a second control voltage generator 5 respectively, where a peak detecting signal V3 and a second control voltage V4 are generated respectively. Also, in a first control voltage generator 7, the voltage 5 is inputted in a non-inversion input terminal 18a of a comparator 18 and a first control voltage V6 corresponding to a difference between the voltage V5 and a threshold voltage VT2 inputted in an inversion input terminal 18b is generated. The first and second control voltages V6 and V4 thus obtained are inputted in an adding device 8, where a timer control voltage V7 is generated and is inputted in a delay signal generator V6. Then, an off-timer part 9 outputs a low-level signal, so that a current to the solenoid coil 2 is intercepted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a solenoid drive circuit that eliminates collision with the front magnetic pole when the solenoid is operated, that is, when the plunger is magnetized and attracted, and relates to a solenoid drive circuit that eliminates collision with the front magnetic pole when the solenoid is operated, that is, when the plunger is magnetized and attracted. This invention relates to a solenoid drive circuit that has made it possible for solenoids to be used in the field of high quality equipment.

[Conventional technology]

A solenoid generally has a plunger, which serves as an iron core, placed inside a cylindrical case that also serves as a yoke so that it can move forward and backward in the axial direction of the case, and a coil installed between the iron core and the case. In addition, magnetic poles are provided at the front and rear of the case, and the iron core is drawn toward the rear of the case by a return spring or the like biased toward the rear.

The operation of such a solenoid is performed by turning on and off current to the coil. In other words, when the coil is energized, a magnetization attraction force acts on the iron core and it is attracted to the front magnetic pole, and by continuing to energize the coil for a certain period of time and moving the iron core forward until it contacts the front magnetic pole, no action is exerted on the outside world. You can get power.

Then, when the current to the coil is cut off in order to return the iron core, the magnetic attraction force is canceled and the iron core returns to its original position by the force of the return spring.

Conventionally, in the operation of the solenoid described above, no special control was performed except for turning on and off the current to the coil, and when the iron core completed advancing and returning, the iron core and the front and rear magnetic poles were connected to each other. The collision caused noise. Although the generation of such noise is not desirable, such a solenoid can be used in fields where the operation frequency is low and a certain amount of noise is allowed because the problem is small.

However, in the field of equipment that operates frequently, such as hydraulic pumps and compressors, it is difficult to use solenoids because the above-mentioned noise becomes intense and frequent collisions also cause problems in terms of equipment durability. . Therefore, in these fields, actuating devices such as linear vibration actuators that are mechanically free of collision parts are employed. However, in this case, since the fixed magnetic pole is arranged in a direction perpendicular to the direction of movement of the movable iron core, the thrust is small, and in other words, the device becomes large in size when trying to obtain the desired thrust.

In contrast, solenoids have a simple structure and are inexpensive, and because they utilize magnetization attraction force generated in the same direction as the movable iron core, they have the advantage that the device can be smaller in size, and the structure and control If plunger collisions can be suppressed by devising a new method, we can expect its use to expand in the field of frequently operated equipment.

[Problem to be solved by the invention]

Noise prevention measures for solenoids have been studied for some time; for example,
No. 72 and Special Publication No. 59-19454 have been proposed.

That is, in Japanese Patent Publication No. 56-10772, on both ends of the yoke,
Permanent magnets are attached so that the magnetization directions are opposite to each other, and the plunge is caused to reciprocate by the superposition of the auxiliary magnetic field of the permanent magnets and the main magnetic field generated by the coil current.

Furthermore, Japanese Patent Publication No. 59-19454 discloses that a plunger is controlled by incorporating a variable resistor, a sliding resistor, etc. into the current control circuit of the solenoid coil to control the balanced position of the attraction force of the solenoid coil and the tension of the return spring. This is to control the stopping position of the In this proposal, a series circuit consisting of a resistor and a capacitor is incorporated into a circuit that negatively feeds back the control voltage of the solenoid coil current to the output side of the sliding resistor, thereby quickly damping vibrations when the plunger is stopped.

Furthermore, Japanese Patent Publication No. 60-16089 devises a method in which a recess is provided at the base of the plunger to change the gap between the plunger and the fixed magnetic pole, thereby reducing the suction force during attraction.

Further, Japanese Patent Publication No. 61-22844 discloses that a movable body attracted by an excitation coil is made of a material with a large residual magnetic flux, and a detection body for detecting the proximity of the movable body is provided near the maximum movement part of the movable body. The direction of energization of the excitation coil is switched in response to a signal from the detection body to prevent impact noise from occurring due to movement of the movable body.

As mentioned above, there are various proposals regarding collision prevention means between the plunger and the magnetic pole in the solenoid coil.
Although it has achieved a certain degree of effectiveness in terms of avoiding collisions, it is still not sufficient. In particular, in these proposals, little consideration is given to disturbance factors.

In other words, for plunger type solenoids, as mentioned in the above proposal, some measures have been taken to avoid plunger collisions, and in theory it should be possible to reliably avoid collisions, but in reality, Due to disturbance factors such as fluctuations in the control voltage and fluctuations in the plunger drive load, the device does not operate according to theory, and the collision described above cannot be reliably avoided.

This invention has been made with attention to these circumstances, and aims to reliably avoid collision between the plunger and the magnetic pole in a plunger type solenoid, and to accurately obtain a predetermined stroke necessary for performing external work with the plunger. This is a problem to be solved, and in particular, the object is to provide means that can reliably achieve the above problem even when there are disturbance factors such as fluctuations in control voltage and plunger drive load.

[Means to solve the problem]

The solenoid drive circuit of the present invention, which has achieved the above object, is a plunger-type solenoid drive circuit that includes voltage detection means for obtaining a voltage according to the current supplied to the solenoid coil, and detecting the peak point of the detected voltage. a peak detector that generates a peak detection signal, a first control voltage generator that generates a first control voltage according to the voltage supplied to the solenoid coil, and a first control voltage generator that generates a first control voltage corresponding to the voltage supplied to the solenoid coil; a second control voltage generation section that generates a second control voltage; an addition section that adds the first control voltage and the second control voltage to generate a timer control voltage; a delay signal generation section that generates a delay time whose length is inversely proportional to the magnitude; and an off-timer section that generates a signal that cuts off the supply current to the solenoid coil for a certain period of time in response to the output of the delay signal generation section. The main point lies in the fact that it has the following features.

[Effect]

Figure 3 is a graph showing the relationship between the drive command, the coil current during solenoid operation, and the stroke of the plunger, which is the movable iron core.When a drive command is issued to the solenoid, the coil current increases exponentially due to the inductance of the coil. When it increases functionally and reaches a certain value at time TI, the suction force exceeds the plunger drive load and the plunger starts moving. When the plunger moves, a back electromotive force acts on the coil, so the rate of increase in the coil current begins to decrease significantly, and the coil current reaches its peak at time T2.From then on, the coil current remains constant until time T4 when the plunger stops moving. The current decreases as shown by the solid line.

In the operation of the solenoid F, no measures are taken to prevent plunger collision, so the plunger advances to its full stroke and collides with the front magnetic pole. At this time, as the distance between the plunger and the front magnetic pole becomes smaller, the attractive force increases dramatically, and in addition, inertial force acts, so the collision with the front magnetic pole becomes severe.

As a result of considering changes in the coil current and plunger stroke during the operation of the solenoid, the applicant of the present invention came up with the following idea.

In other words, if the coil current is cut off at a certain point while the plunger is moving forward, the magnetization attraction force due to the coil current disappears at the point of cutoff, and although it may move forward slightly due to inertial force, the force of the return spring acts exclusively. Therefore, the plunger hardly moves forward from the point of shutoff.

As a result, collision between the plunger and the front magnetic pole can be avoided, and the plunger can be returned to the initial stroke position. And not only to avoid collisions;
A predetermined stroke can be obtained to cause the solenoid to perform external work. Since the optimum time T3 at which such coil current should be cut off always exists between the peak time T2 and the collision time T4, the time from the peak time T2 to the optimum cutoff time T3 is defined as the delay time T, and the peak time T2 is By detecting this and properly setting the delay time T according to the characteristics of each solenoid, collisions can be avoided and a predetermined stroke can be ensured.

However, the above-mentioned appropriate delay time T is established under the condition that the power supply voltage supplied to the coil and the load required to drive the plunger are constant, and if these change, the appropriate delay time T will be adjusted accordingly. It is necessary to change T. For example, when a power source with large voltage fluctuations, such as an automobile battery, is used as a power source for a solenoid, the influence is large, and the delay time T in this case is inversely proportional to the magnitude of the power supply voltage. be.

In addition, within a range where the plunger driving load is small, it is possible to obtain a specified stroke even with a certain delay time, but when the load exceeds a certain value, the stroke tends to increase, and the plunger becomes closer to the front magnetic pole. lead to a collision situation.

To avoid this, the delay time T must be shortened in accordance with the load, ie, the magnitude of the coil current, required for driving during the plunge.

The solenoid drive circuit of the present invention avoids collision between the plunger and the magnetic pole in response to the above-mentioned disturbance factors, and by adopting the above configuration, even when there are fluctuations in the power supply voltage or load, The objective is to secure the stroke of the plunger necessary to perform external work without causing a collision.

That is, according to the above configuration, the voltage detection means detects the voltage according to the current supplied to the solenoid coil.

Then, the peak point of the detected voltage is detected by a peak detector, and the peak detector transmits a peak detection signal of a predetermined output to the delay signal generation section in conjunction with the detection of the peak point. On the other hand, a first control voltage is generated based on the power supply voltage, that is, the voltage supplied to the solenoid coil, and this is input to the adder to generate a timer control voltage, which is input to the delay signal generator. The delay signal generating section compares the peak detection signal with the timer control voltage to generate a delay time whose length is inversely proportional to the magnitude of the timer control voltage. That is, when the timer control voltage becomes higher, the delay time until the output of the peak detection signal detects the peak and attenuates to become balanced with the timer control voltage is shortened.

In the off-timer section, the off-timer is activated in response to the delay signal from the delay signal generation section, and a supply current cutoff signal is transmitted to the solenoid coil. Next, when the time set in the off timer has elapsed, the off timer returns, the supply current cutoff signal to the solenoid coil is stopped, and the solenoid coil can be restarted.

As described above, the delay signal is generated by the functions of the peak detector and the delay signal generator, and the coil supply current can be cut off at the optimal time T3 for performing external work without causing the plunger to collide.

Further, since the timer control voltage, which is a comparison voltage in the delay signal generating section, is determined based on the first control voltage that reflects the fluctuations in the power supply voltage, the delay signal reflects the fluctuations in the power supply voltage.

Furthermore, a second control voltage corresponding to the difference between the detected voltage obtained by the voltage detecting means and a certain reference voltage is manually inputted to the addition section that generates the timer control voltage by merging with the first control voltage. , the timer control voltage is corrected by the second control voltage. In other words, since the current supplied to the solenoid coil changes depending on the load applied to the solenoid coil, the second control voltage generation unit grasps the fluctuation of the detected voltage corresponding to the supplied current and uses the timer. By reflecting this in the control voltage, it is possible to generate a delay signal in accordance with fluctuations in the plunger drive load. At this time, the second control voltage generation section generates a second control voltage according to the difference between the detected voltage and a certain reference voltage, and if the detected voltage is lower than the reference voltage, that is, the plunger driving load is The configuration is such that the correction by the second control voltage does not work when the voltage is small.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram showing a solenoid drive circuit according to an embodiment, and FIG. 2 is a signal waveform diagram of each part in the solenoid drive circuit of FIG. 1. In addition, Fig. 2 is a signal waveform diagram when the load increases each time it operates under a certain main power supply voltage, and the first and second waveforms show the case where the current flowing through the load, that is, the coil, is small. , the third waveform is for the large case.

The solenoid drive circuit 1 includes a transistor 3 that controls the current supplied to the solenoid coil 2, a peak detector 4, and a peak detector 4.
and the second control voltage generation section 5 are branched, the peak detector 4 is connected to the delay signal generation section 6, and the second control signal generation section 5 is connected to the delay signal generation section 6.
It merges with a first control voltage generation section 7 consisting of a separate path and is connected to an addition section 8, which is further connected to a delay signal generation section 6. The delay signal generating section 6 is connected to the base of the transistor 3 via an off-timer section 9 and an AND gate 10.

In the above solenoid drive circuit 1, the AND gate 10
When a drive command is given to terminal 11 of
conducts, current is supplied from the main mold -a12 to the solenoid coil 2, and a detection voltage v1 corresponding to the supplied current is generated across the resistor (voltage detection means) 13, as shown in FIG. 2(B). occurs. This detected voltage vl is branched and inputted to the peak detector 4 and the second control voltage generating section 5, respectively.

In the peak detector 4, the detected voltage v1 is amplified and differentiated by an amplifier circuit 14 and a differentiator circuit 15, respectively. As shown in FIG. 2 (C), the obtained differential voltage v2 is a positive voltage from TO at startup to time T1 when the movable iron core starts moving, but decreases after TI. , becomes zero at time T2 when the detected voltage 5 reaches its peak. This differential voltage 2 is input to the non-inverting input terminal 16a of the comparator 16, and the inverting input terminal 16 to which approximately zero volts is input
A comparison is made between the peak detection signal v3 and the peak detection signal v3, which is input to the delay signal generation section 6. Note that the peak detection signal v3 of the comparator 16 is as shown in FIG. 2(D).
It becomes a high level at the moment of startup, and becomes a low level when the peak of the detection voltage νl is detected.

On the other hand, in the second control voltage generation section 5, the branched detection voltage v1 is inputted to the non-inverting input terminal 17a of the comparator 17, and is inputted to the inverting input terminal 17b according to the difference with the threshold voltage VTI. A second control voltage 4 is generated. The second control voltage v4 is expressed by the following equation.

V4=AI・(Si1−VTI) (At is the coefficient) ・・・・・・・・・
-(1) Also, in the first control voltage generation section 7, the main power supply voltage V
The voltage v5 obtained by dividing O is input to the non-inverting input terminal 18a of the comparator 18, and the first control voltage v6 is determined according to the difference between the voltage v5 and the threshold voltage VT2 input to the inverting input terminal 18b.
occurs. The first control voltage ν6 is expressed by the following equation.

V6=A2・(V5−VT2) V5=A3・νO [Row is amplification factor, A3 is voltage division ratio] ・・・・・・・・・
(2) The first control voltage 6 and the second control voltage v4 thus obtained are inputted to the adder 8 and added together to generate a timer control voltage v7, which is inputted to the delay signal generation section 6. This timer control voltage v7 is shown by a broken line in FIG. 2(E).

Next, to explain the operation of the delayed signal generating section 6, when a current flows through the solenoid coil 2 and a high level peak detection signal v3 is inputted from the peak detector 4 to the delayed signal generating section 6, the peak detection signal v3 is input to the delayed signal generating section 6. ν3 is charged to capacitor C1 through resistor R1.

A Zener diode 19 is connected in parallel to the capacitor C1, and the charging voltage of the capacitor C1 is maintained at the Zener voltage VZI. Here, Zener voltage VZ
Since I is set to be larger than the timer control voltage, the comparator 20 of the delay signal generating section 6 selects the non-inverting input terminal from the timer control voltage v7 which is input to the inverting input terminal 20b via the adding section 8. The voltage v8 of the comparator 20a is higher, the output v9 of the comparator 20 becomes high level, the off-timer section 9 becomes inactive, and generates a high level output.

Next, when the peak detector 4 detects the peak of the detection voltage v1, the peak detection signal v3 becomes low level, so the voltage of the capacitor C1 and the voltage v8 of the non-inverting input terminal 20a of the comparator 20 are discharged through the resistor R1. , eventually becomes smaller than the timer control voltage shift, so the output (2)9 of the comparator 20 becomes low level.

The off-timer section 9 operates in response to the fall change of the output v9 of the comparator 20 from high level to low level, and outputs a low level signal for a certain period of time. As a result,
The output of ANDCATE 10 becomes low level, transistor 3 becomes non-conductive for the same period of time, and current to solenoid coil 2 is cut off. During this time, the plunger, which is a movable iron core, is returned to its original position by a return spring.

Then, the off-timer section 9 returns after a certain period of time and sends a high-level output to the AND gate 1o again, so that the same operation is repeated as long as there is a drive command at the terminal 11 of the AND gate 10.

By the way, after the peak detector 4 detects the peak value of the detection voltage v1, the time until the output of the comparator 20 is inverted from high level to low level, that is, the delay time T, mainly depends on the magnitude of the main power supply voltage vO. There is an optimal value. The relationship between T and vO can be determined experimentally.

That is, when the constants in the above equation (2) were set as follows and the relationship values between T and vO were experimentally determined, the values shown in Table 1 were obtained.

When calculated by substituting , the first control voltage v6, that is, the timer control voltage v7, is as shown in Table 2. In the above calculation, it is assumed that the load on the solenoid coil 2 is small and the second control voltage v4 is not generated.

Table 2 A2-3, 83 = 1/7, νT2 = 3 Table 1 By the way, the discharge voltage of capacitor C1, that is, voltage v8, is:
It is shown by the following formula.

VB=VZ1 ・e V℃ ・・・・・・・・・(3) Therefore, in equation (2), use the above setting values and the experimental values in Table 1, and then make sure that the magnitude of voltage v8 matches the timer control voltage v7. Since the time until V is equal to the delay time T shown in Table 1,
By substituting 7=V8 into equation (3) and transforming it, the time constant τ can be expressed by the following equation.

r −-T/ i n (V7/shi Z1)...
...(4) Here, even if the main power supply voltage νO is different, the time constant τ and the Zener voltage VZI are constants, so when calculating by substituting the values in Table 2 using equation (4), τ and VZ
I can be determined as follows.

r-0,35 (ms), VZI =5. 26
(V)・・・・・・・・・(5) Therefore, for example, if the capacitance of capacitor CI is 0.01 (μF)
In this case, the value of the resistor R1 is 35 (kΩ).

As mentioned above, the circuit conditions of the delay signal generator 6 can be determined based on experimental values, and under these circuit conditions, the partial voltage v5 of the main power supply voltage νO input to the first control voltage generator 7 is The fluctuation is reflected in the first control voltage vO and eventually in the timer control voltage v7, so that the delay time T can be appropriately controlled.

Next, regarding the influence of the load on the solenoid coil 2 on the delay time T, as seen in the third voltage fluctuation waveform in FIG. If the threshold voltage VTI is exceeded, (1)
The second control voltage v4 shown in the formula is added to the first control voltage vO to generate a timer control voltage v7, which is input to the inverting input terminal 20b of the comparator 20. As a result, the delay time T
Since is set small, the stroke of the plunger does not become excessive, and an appropriate stroke corresponding to the load on the solenoid coil 2 can be obtained. Here, the threshold voltage VTI and the constant AI in equation (1) are not affected by the magnitude of the main power supply voltage, so they can be easily adjusted in any driving state.

〔Effect of the invention〕

The present invention is configured as described above, and detects the peak of the coil current, that is, the peak of the detection voltage corresponding to the coil current, and from the time of detection, there is a delay that is inversely proportional to the magnitude of the main power supply voltage and the magnitude of the load. Since the coil current is cut off after a certain period of time has elapsed, it is possible to eliminate collisions when the plunger moves forward even when the main power supply voltage or load changes, and it also prevents collisions when the plunger is moving forward. A predetermined stroke can be obtained. Therefore, generation of noise and vibration can be suppressed. In addition, since the coil current is cut off to prevent overstroke, it is possible to save power consumption and suppress heat generation, and the frequency of solenoid switching can be increased, so when applied to a hydraulic pump, for example. A large flow rate can be obtained.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the solenoid drive circuit according to the embodiment, Figures 2 (A) to (I) are signal waveform diagrams for explaining the operation of the circuit in Figure 1', and Figure 3 (A). ~(C) is a change characteristic diagram for explaining the operation of the solenoid. 2... Solenoid coil 4... Peak detector 5... Second control voltage generating section 6... Delay signal generating section 7... First control voltage generating section 8... Adding section 9... Off timer section 13...Resistor (voltage detection means) ν1...Detection voltage v3...Peak detection signal v4...Second control voltage v6...First control voltage v7...Timer control voltage νT1 ...Threshold voltage (reference voltage)

Claims (1)

[Claims] (1) In a drive circuit for a plunger type solenoid, a voltage detection means for obtaining a voltage according to the current supplied to the solenoid coil, a peak detector for detecting the peak point of the detected voltage and generating a peak detection signal, and a solenoid a first control voltage generation section that generates a first control voltage according to the voltage supplied to the coil; and a second control voltage generation section that generates a second control voltage according to the difference between the detected voltage and a certain reference voltage. , an adder that adds the first control voltage and the second control voltage to generate a timer control voltage, and generates a delay time whose length is inversely proportional to the magnitude of the timer control voltage in response to the peak detection signal. What is claimed is: 1. A solenoid drive circuit comprising: a delay signal generating section for generating a solenoid coil; and an off timer section receiving an output from the delay signal generating section and generating a signal for cutting off current supplied to a solenoid coil for a certain period of time.