JP2000002357A - Solenoid valve control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the valve opening control characteristics of a solenoid valve compatibly with achievement of low cost. SOLUTION: A bias current control circuit 46 is the one for feeding a definite bias current to a solenoid coil 40 of a purge control valve (solenoid operated), in which a series circuitry of a switching element 47 such as MOSFET for control of the bias current and a current sensing resistance 48 is installed parallel with a switching element 42 for duty control. The bias current flowing in the solenoid coil 40 is detected by the resistance 48, and the control circuit 46 controls the operation of the switching element 47 so that the bias current becomes identical to the target. The target for the bias current is set so that the valve closing force of a spring at the time of valve closing is canceled substantially by the electromagnetic force in opening direction of the purge control valve based on the bias current. This enables to eliminate substantially a dislocation of the opening timing of the purge control valve even though a variation exists in the source voltage and/or coil temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve control device with improved valve opening characteristics of a solenoid valve.

[0002]

2. Description of the Related Art Conventionally, solenoid valves have been widely used as means for controlling the flow of various fluids. For example, in automobiles, they are used as a purge control valve of a fuel evaporative gas purge system, an idle speed control valve (ISCV), and the like. Solenoid valves are used. Here, the fuel evaporative gas purging system includes a canister for adsorbing the fuel evaporative gas and a purge evaporator in the middle of a purge path for purging the fuel evaporative gas (evaporative gas) generated by evaporating the fuel in the fuel tank into an intake pipe of the internal combustion engine. A control valve is provided, and by controlling the purge control valve, the purge amount of fuel evaporative gas purged from the canister to the intake pipe is controlled.

At present, a purge control valve used is an electromagnetically driven type using an electromagnetic valve and a negative pressure driven type using a pneumatic valve using an intake pipe negative pressure as a pressure source (Japanese Patent Laid-Open No.
However, in the case of the negative pressure drive type, it is necessary to provide a pipe for introducing the negative pressure of the intake pipe, so that there is a disadvantage that the cost is increased.

On the other hand, an electromagnetically driven purge control valve (see Japanese Patent Application Laid-Open No. 10-9909) controls the ratio between the valve opening time (on time) and the valve closing time (off time) of the purge control valve. Thus, the purge amount of the fuel evaporative gas is controlled. However, if the purge control valve is repeatedly opened / closed (purge execution / stop), the fuel evaporative gas purge amount flowing from the canister into the intake pipe pulsates.
The air-fuel ratio of the air-fuel mixture sucked into the cylinder of the internal combustion engine is disturbed, and the emission and drivability deteriorate. To improve this, a purge control valve with a linear solenoid as the drive source is used, and the duty of the voltage applied to the linear solenoid is controlled to control the opening degree of the purge control valve, thereby purging the fuel vapor gas. There is something to control.

[0005]

Incidentally, the purge control valve (electromagnetic valve) has a built-in spring for urging the valve body in the valve closing direction, and the valve closing state is maintained by this spring force. Therefore, in order to open the valve, it is necessary for the solenoid to generate at least an electromagnetic force (valve opening force) that overcomes the valve closing force of the spring.

During operation of a vehicle, the power supply voltage fluctuates and the coil resistance changes due to a change in coil temperature.
As shown in FIG. 4 (b), the value of the current flowing through the solenoid coil changes due to the fluctuation of the power supply voltage and the coil temperature, and the electromagnetic force of the solenoid changes greatly. The duty signal DUTY when starting to open the valve greatly changes.

Immediately after the purge control valve is opened, the purge amount of the fuel evaporative gas rapidly increases and the air-fuel ratio changes rapidly. Therefore, it is preferable that the air-fuel ratio be corrected in accordance with the purge amount simultaneously with the opening of the purge control valve. In the conventional duty control method, as shown in FIG. 4B, the opening timing of the purge control valve is greatly shifted due to a change in the power supply voltage or a change in the coil temperature. Since the opening timing of the control valve is not known, it is not possible to accurately correct a sudden change in the air-fuel ratio due to the opening of the purge control valve.

In order to solve this problem, in recent years, an electromagnetic force (coil current value) is controlled by feedback control of a current flowing through a solenoid coil so as not to be affected by fluctuations in power supply voltage and changes in coil temperature. Some adopt a current control type purge control valve. However, in this current control method, it is necessary to perform feedback control of the coil current in all regions, so that there is a disadvantage that the configuration of the control circuit is complicated and the cost is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, it is an object of the present invention to provide an electromagnetic valve control device capable of achieving both improved valve opening control characteristics of an electromagnetic valve and reduced cost. Is to do.

[0010]

According to a first aspect of the present invention, there is provided a solenoid valve control device according to the first aspect of the present invention, wherein a predetermined bias current is supplied to a solenoid coil by a bias current control means to close the solenoid coil. An electromagnetic force is generated in the valve opening direction that opposes the valve force. As the electromagnetic force in the valve opening direction due to the bias current approaches the valve closing force due to the spring, the shift in the valve opening timing of the electromagnetic valve decreases (see FIG. 4). Therefore, if the duty control is performed while the bias current is flowing, the opening of the solenoid valve can be controlled more accurately than in the conventional duty control. Moreover, unlike the current control method, there is no need to perform feedback control of the coil current in all regions,
A simple circuit configuration can be adopted.

In this case, it is preferable to set the bias current such that the electromagnetic force in the valve opening direction due to the bias current substantially cancels the valve closing force by the spring when the valve is closed. With this configuration, even if there is a change in the power supply voltage or a change in the coil temperature, it is possible to substantially eliminate the shift in the valve opening timing of the solenoid valve.

The bias current may be turned off when the closed state of the solenoid valve continues for a predetermined time or more. That is, when the closed state of the solenoid valve lasts for a long time, there is no need to supply a bias current.If the bias current is turned off, an increase in power consumption and an increase in coil temperature due to the bias current during closing of the solenoid valve can be avoided. Thus, the valve closing force by the spring can be reliably operated to reliably hold the solenoid valve in the closed state.

The solenoid valve control device of the present invention described above
The present invention can be applied to a system in which the flow of various fluids is controlled by an electromagnetic valve. In particular, when the present invention is applied to a fuel evaporative gas purge system, a great effect can be obtained. That is, immediately after the purge control valve is opened, the air-fuel ratio is preferably corrected at the same time as the purge control valve is opened, since the purge amount of the fuel evaporative gas suddenly increases and the air-fuel ratio changes rapidly. The solenoid valve control device of the present invention has a small (or zero) difference in valve opening timing as compared with the conventional duty control method, and therefore accurately corrects a sudden change in the air-fuel ratio due to the opening of the purge control valve. This makes it possible to improve emission and drivability during purge control.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a fuel vapor purge system will be described below with reference to the drawings. First, a schematic configuration of the entire system will be described with reference to FIG. An air cleaner 13 is provided on the upstream side of an intake pipe 12 of the engine 11, and air passing through the air cleaner 13 is passed through a throttle valve 14 to the engine 11.
Is taken into each cylinder. A fuel injection valve 16 is provided at an intake port of each cylinder of the intake pipe 12, and fuel (gasoline) in a fuel tank 17 is supplied to each fuel injection valve 16 by a fuel pump 18 via a fuel pipe 19. Come.

Next, the configuration of the fuel vapor purge system 21 will be described. A canister 23 is connected to the fuel tank 17 via a communication pipe 22, and a fuel evaporative gas is adsorbed by an adsorbent 24 such as activated carbon housed in the canister 23. An air communication pipe 25 communicating with the atmosphere is provided on the bottom surface of the canister 23, and a canister closing valve 26 is attached to the air communication pipe 25.
The canister closing valve 26 is constituted by a normally open solenoid valve, and is maintained in an off state (valve open state) during the purge control, and is maintained in a state where the canister 23 is open to the atmosphere.

On the other hand, between the canister 23 and the intake pipe 12, the fuel evaporative gas adsorbed by the adsorbent 24 is supplied to the intake pipe 1.
Purge passages 30a, 30 for purging (discharging)
b, and a purge control valve 31 for adjusting the purge flow rate is provided between the purge passages 30a and 30b. The purge control valve 31 is constituted by a normally-closed solenoid valve, and is kept closed by a built-in spring (not shown) when it is off. The purge control valve 31 is controlled by a microcomputer (not shown) provided in the engine control circuit 32 and a purge control circuit 33 (see FIG. 1). A microcomputer in the engine control circuit 32 calculates a target opening (target purge rate) of the purge control valve 31 according to the engine operating state, and outputs a duty signal Duty corresponding to the target opening to the purge control circuit 33. I do.

Next, a purge control circuit 33 will be described with reference to FIG.
Will be described. The input interface circuit 34 of the purge control circuit 33 has a built-in comparator 35. A duty signal Duty output from a microcomputer in the engine control circuit 32 is input to a minus input terminal of the comparator 35, and a voltage is divided by a resistance ratio of the voltage dividing circuit 36 to a plus input terminal of the comparator 35. The reference voltage Vth is input. The comparator 35
The duty signal Duty is compared with the reference voltage Vth. As shown in FIG. 2, when the duty signal Duty is at a high level (Duty> Vth), the output of the comparator 35 becomes low level, and At the time of <Vth), the output of the comparator 35 becomes a high level.

An output of the comparator 35 (a signal obtained by inverting the duty signal Duty) is input to a duty control circuit 37, a bias current on / off circuit 38, and a fail-safe circuit 39, respectively. The duty control circuit 37 is a circuit that performs duty control on energization of the solenoid coil 40 of the purge control valve 31.
1 and M driven by the output of the AND circuit 41
And a switching element 42 such as an OSFET. The output of the comparator 35 and the output of the bias current on / off circuit 38 are input to both input terminals of the AND circuit 41, and only when both inputs are at high level,
The output of the circuit 41 is inverted to the high level, and the duty control switching element 42 is turned on. Since the switching element 42 is provided in the energization circuit of the solenoid coil 40, when the switching element 42 is turned on, a current flows through the solenoid coil 40.

The bias current on / off circuit 38 is a circuit for turning off the bias current of the solenoid coil 40 when the closed state of the purge control valve 31 has continued for a predetermined time Td or more. , An edge detection circuit 43 for detecting an edge, a timer 44, a carry signal output circuit 45, and the like. The edge detection circuit 43 clears the timer 44 when detecting either the rising edge or the falling edge of the output of the comparator 35. This timer 44 counts the elapsed time after clearing, and the count value is equal to a predetermined time Td.
(At least several times as long as the cycle of the duty signal Duty), that is, a state where the rising / falling edge of the output of the comparator 35 is not detected (the closed state of the purge control valve 31) reaches a certain time Td. When you do
A carry signal is output from carry signal output circuit 45, and the output of bias current on / off circuit 38 is inverted to a low level by the carry signal. This low-level signal is input to the duty control circuit 37 and a bias current control circuit 46, which will be described later, so that both operations are prohibited. Thereby, the solenoid coil 4
The 0 bias current is turned off.

After the bias current is turned off, the edge detection circuit 4
If the rising edge or the falling edge of the output of the comparator 35 is detected at 3, the output of the bias current on / off circuit 38 is inverted to a high level at that time,
Duty control circuit 37 and bias current control circuit 46
Operation is permitted. Thus, the bias current flows through the solenoid coil 40 again.

The bias current control circuit 46 is a circuit for supplying a constant bias current to the solenoid coil 40. A series circuit of a switching element 47 such as a MOSFET for controlling the bias current and a current detection resistor 48 is used for the duty control for the duty control. Is provided in parallel with the switching element 42. The bias current flowing through the solenoid coil 40 flows to the current detection resistor 48 via the bias current control switching element 47, and a voltage Vbias corresponding to the bias current is generated in the current detection resistor 48. This voltage V
The bias is input to the − input terminal of the comparator 50, and the + input terminal of the comparator 50 has a reference voltage Vref for setting a bias current divided by the resistance ratio of the voltage dividing circuit 51.
Is entered. The comparator 50 compares the bias current detection voltage Vbias with the reference voltage Vref, and switches the output between a high level and a low level according to the comparison result.
The output of the comparator 50 is input to one input terminal of an AND circuit 49, and the output of the bias current on / off circuit 38 is input to the other input terminal of the AND circuit 49. The switching element 47 is driven by the output of the AND circuit 49, and a constant bias current flows through the solenoid coil 40.

During duty control (during purge control), A
Since one input of the ND circuit 49 (the output of the bias current on / off circuit 38) is maintained at a high level, AND
The output level of the circuit 49 is switched according to the output of the comparator 50 input to the other input terminal. Thus, the on / off of the bias current control switching element 47 is controlled so that the bias current flowing through the solenoid coil 40 becomes the target value set by the reference voltage Vref. In this case, the purge control valve 3 using the bias current
The target value (reference voltage Vref) of the bias current is set so that the electromagnetic force in the opening direction of 1 substantially cancels the closing force of the spring when the valve is closed. The bias current control circuit 46 and the bias current on / off circuit 38 described above
Function as a bias current control means referred to in the claims.

On the other hand, the fail-safe circuit 39 includes an abnormality detection circuit 53 for detecting an abnormality of the purge control circuit 33, a charge pump 54 for increasing the power supply voltage (+ B), and a MOSFET or the like driven by the charge pump 54. The switching element 55 is connected to an energizing circuit of the solenoid coil 40. When the purge control circuit 33 is operating normally, a drive signal is output from the abnormality detection circuit 53 to the charge pump 54, so that the charge pump 54 is driven and the switching element 55 is kept in the ON state. And
When the abnormality detection circuit 53 detects an abnormality in the purge control circuit 33, the drive of the charge pump 54 is stopped, the switching element 55 is turned off, and the power supply to the solenoid coil 40 is cut off. The surge absorbing diode 52 is connected in parallel to the solenoid coil 40.

In the embodiment described above, a constant bias current is supplied to the solenoid coil 40 of the purge control valve 31 by the bias current control circuit 46, and the electromagnetic force in the valve opening direction due to the bias current is closed by the spring when the valve is closed. Since the bias current is controlled so as to substantially cancel the valve force, as shown in FIG. 4A, even if the electromagnetic force (valve opening force) changes due to the fluctuation of the power supply voltage or the coil temperature, the purge control is performed. The deviation of the valve opening timing of the valve 31 can be substantially eliminated. Therefore, the duty signal Duty
Even if the valve opening timing of the purge control valve 31 is determined and the fluctuation of the air-fuel ratio due to the purge control is corrected, the air-fuel ratio correction can be performed with higher accuracy than the conventional one (see FIG. 4B). Emission and drivability during purge control can be improved. In addition, unlike the current control method, there is no need to perform feedback control of the coil current in all regions, a simple circuit configuration can be adopted, and the demand for cost reduction can be satisfied.

In the above embodiment, the electromagnetic force in the valve opening direction by the bias current is set so as to substantially cancel the valve closing force by the spring when the valve is closed. For example, it may be set to 90%, 80%, 70%,. As is clear from FIG. 4, as the electromagnetic force in the valve opening direction due to the bias current approaches the valve closing force due to the spring, the shift in the valve opening timing of the electromagnetic valve decreases. Therefore, even when the electromagnetic force in the valve opening direction due to the bias current is smaller than the valve closing force due to the spring at the time of closing the valve, the related art [see FIG.
As compared with, the deviation of the valve opening timing can be reduced, and the valve opening characteristics of the purge control valve 31 can be improved.

In the above embodiment, the purge control valve 3
When the valve closing state of No. 1 continues for a predetermined time Td or more, the solenoid coil 40 is turned on by the bias current on / off circuit 38.
Is turned off, it is possible to avoid an increase in power consumption and a rise in coil temperature due to the bias current during the closing of the purge control valve 31, and to reliably operate the purge control valve 31 by using the valve closing force of the spring. The closed state can be reliably maintained.

In the above embodiment, once the bias current is turned off, the bias current is turned off until a rising / falling edge of the output of the comparator 35 (a signal obtained by inverting the duty signal Duty) is detected. For example, when the bias current is turned off, a pulse for resuming the supply of the bias current is output before the microcomputer in the engine control circuit 32 outputs the duty signal Duty. The bias current on / off circuit 3
The duty signal Duty may be output after the output of No. 8 is inverted to a high level and the application of the bias current is restarted.

In the above-described embodiment, the diode 52 is used as a means for absorbing a surge voltage generated by the solenoid coil 40. However, a surge absorbing circuit using a Zener diode, a CR circuit, or the like may be used instead. . The switching elements 42, 47, 55 are
Bipolar transistor, IGB instead of SFET
Other switching elements such as T and thyristor may be used.

In addition, the present invention is not limited to the control device of the purge control valve, but includes various solenoid valves used for automobiles such as an idle speed control valve (ISCV), and various solenoids used for other than automobiles. The present invention is also applicable to a valve control device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a purge control circuit according to an embodiment in which the present invention is applied to a fuel evaporative gas purge system.

FIG. 2 is a time chart showing voltage waveforms at various parts of a purge control circuit.

FIG. 3 is a diagram schematically showing a configuration of a fuel evaporative gas purge system.

FIG. 4A is a diagram showing the valve opening characteristics of a purge control valve according to an embodiment of the present invention, and FIG. 4B is a diagram showing the valve opening characteristics of a conventional purge control valve.

[Explanation of symbols]

12 ... intake pipe, 17 ... fuel tank, 21 ... fuel evaporative gas purge system, 23 ... canister, 24 ... adsorbent, 2
6: canister closing valve, 30a, 30b: purge passage,
31: Purge control valve (electromagnetic valve), 32: Engine control circuit, 33: Purge control circuit, 37: Duty control circuit, 38: Bias current on / off circuit (bias current control means), 39: Fail safe circuit, 40 ... Solenoid coil, 42 switching element, 46 bias current control circuit (bias current control means), 47 switching element, 48 current detection resistor, 53 abnormality detection circuit, 55 switching element.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G084 BA06 BA27 DA04 DA13 EA07 EC01 EC03 EC06 FA00 3G301 HA01 HA14 JA14 LA04 MA11 NB03 NC02 NE23 PB09Z PG02Z 3H106 EE01 EE48 FA02 FB08 FB43 GA30 KK17

Claims (4)

[Claims] 1. A valve body of an electromagnetic valve is urged in a valve closing direction by a spring, and a current is supplied to a solenoid coil of the electromagnetic valve to drive the valve body in a valve opening direction against the spring. An electromagnetic valve control device for controlling an opening degree of an electromagnetic valve by using a bias current control means for supplying a predetermined bias current to the solenoid coil. 2. The bias current control means sets the bias current such that the electromagnetic force in the valve opening direction by the bias current substantially cancels the valve closing force by the spring when the valve is closed. The solenoid valve control device according to claim 1. 3. The solenoid valve control device according to claim 1, wherein the bias current control unit turns off the bias current when the closed state of the solenoid valve continues for a predetermined time or more. 4. The valve according to claim 1, wherein the solenoid valve is provided as a purge control valve in the middle of a purge path for purging fuel vapor generated in the fuel tank into an intake pipe of the internal combustion engine. 3. The electromagnetic valve control device according to any one of 3.