JP3440668B2 - Correction of coil resistance change due to temperature change - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solenoid valve control device by duty control.

[0002]

2. Description of the Related Art Conventionally, for example, an actual Kaihei 7-15421
As disclosed in Japanese Patent Publication No.
A solenoid valve is used as a purge control valve provided in a purge passage from a canister that adsorbs evaporated fuel from a fuel tank to an intake passage of an engine.

When controlling the opening of such a solenoid valve, a drive switching element that is connected in series with a solenoid valve energizing circuit is ON / OFF controlled by an output duty based on a target duty.

[0004]

However, when the solenoid valve is duty-controlled, the coil resistance changes due to the environment (especially temperature) of the solenoid valve.
There is a problem in that the rise of the current when the duty signal changes from OFF to ON changes, which changes the valve opening delay time and causes flow rate variations even with the same duty.

In particular, as the required flow rate increases, the variation width with respect to the required flow rate also increases. For this reason, the solenoid valve cannot be used, and the expensive step motor type valve must be used. It was The device described in the above publication uses a positive temperature coefficient thermistor,
Although the current when holding the state after opening the valve is reduced, it is a method of monitoring the current during the ON period of the driving switching element, so when performing duty control,
It cannot be adopted.

In view of such conventional problems, it is an object of the present invention to provide a solenoid valve control device capable of meeting the demand for a large flow rate by reducing the flow rate variation.

[0007]

For this reason, in the invention according to claim 1, a solenoid for controlling ON / OFF of a drive switching element which is interposed in series with an energizing circuit of a solenoid valve is controlled by an output duty based on a target duty. In the valve control device, the OF of the drive switching element is connected in parallel with the drive switching element.
Pull-down resistor that flows a small current less than the valve opening current to the solenoid valve during F period and OF of the drive switching element
A structure in which resistance equivalent value detecting means for detecting the coil resistance equivalent value of the solenoid valve by the small current during the period F and duty correction means for correcting the output duty according to the detected coil resistance equivalent value of the solenoid valve are provided. (See FIG. 1).

That is, the drive switching element is turned off.
During the period, a small current that does not open the valve is applied to the solenoid valve through a pull-down resistor provided in parallel with the pull-down resistor to detect the coil resistance equivalent value of the solenoid valve. Then, according to the detected coil resistance equivalent value of the solenoid valve, for example, the larger the coil resistance equivalent value, the longer the valve opening delay time.
Correct the output duty.

In the invention according to claim 2, the resistance equivalent value detecting means detects the potential difference between the both ends of the coil of the solenoid valve during the OFF period of the driving switching element as the coil resistance equivalent value of the solenoid valve. It is characterized by In the invention according to claim 3, the coil resistance equivalent value of the solenoid valve detected by the resistance equivalent value detecting means is averaged between the resistance equivalent value detecting means and the duty correcting means, and the duty correcting means is provided. It is characterized in that an averaging means for inputting to is provided.

The invention according to claim 4 is characterized in that the resistance equivalent value detecting means is provided with prohibiting means for prohibiting detection of the coil resistance equivalent value when the output duty is equal to or more than a predetermined value. When the output duty is equal to or higher than a predetermined value, that is, when the OFF period is short, the small current is not stable and there is a possibility of erroneous detection, so the detection is prohibited. Claim 5
In the invention according to, the solenoid valve is a purge control valve provided in a purge passage from the canister for adsorbing the evaporated fuel from the fuel tank to the intake passage of the engine.

[0011]

According to the first aspect of the present invention, during the OFF period of the drive switching element, a small current is supplied to the solenoid valve so that the valve does not open, and the coil resistance equivalent value of the solenoid valve is detected. By performing the duty correction according to, it is possible to reduce the variation in the flow rate due to the environmental change, and it is possible to meet the demand for a larger flow rate.

According to the second aspect of the invention, the coil resistance equivalent value can be easily detected by detecting the potential difference across the coil as the coil resistance equivalent value of the solenoid valve. According to the invention of claim 3, by averaging the coil resistance equivalent values of the detected solenoid valves and using them, it is possible to obtain an effect that the control accuracy can be improved.

According to the fourth aspect of the present invention, in the situation where the OFF period is short and the small current is not stable, the detection is prohibited to prevent erroneous detection and further improve the control accuracy. To be According to the invention of claim 5, by applying to the purge control valve of the engine, it is possible to obtain the effect that the purge flow rate control by the purge control valve used in an environment with a large temperature difference can be realized more accurately.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to illustrated examples. First, an evaporated fuel processing apparatus for an automobile engine, in which a solenoid valve according to the present invention is used as a purge control valve, will be described with reference to FIG. In FIG. 2, a throttle valve 3 is provided in an intake passage 2 of an engine 1, and an air flow meter 4 for detecting an intake air flow rate Q is provided upstream of the throttle valve 3. Reference numeral 5 is a fuel injection valve provided for each cylinder.

The canister 6 is an airtight container filled with an adsorbent such as activated carbon, and the evaporative fuel introduction passage 8 from the upper space of the fuel tank 7 is connected to one chamber of the space portion on the upper surface side. Has been done. A purge passage 9 is connected to the other chamber of the space on the upper surface side of the canister 6, and the purge passage 9 is connected to a downstream side of the throttle valve 3 (intake air of the intake passage 2 via a purge control valve 10). Manifold). Further, a fresh air introduction port 11 is formed in the space on the lower surface side of the canister 6.

The purge control valve 10 is a solenoid valve that opens when the solenoid coil is energized and closes when the energization is stopped. By being driven by the signal, the opening degree is controlled to substantially correspond to the duty. The operation will be described. The evaporated fuel generated in the fuel tank 7 while the engine 1 is stopped is guided to the cunister 6 through the evaporated fuel introduction pipe 8 and adsorbed there, so that the fuel vapor is released into the atmosphere. It is prevented from being released.

Next, when the engine 1 is started and a predetermined purge permission condition is satisfied during the subsequent operation, the purge control valve
As a result of the suction negative pressure of the engine 1 acting on the canister 6, the evaporated fuel adsorbed on the canister 6 is desorbed by the fresh air introduced from the fresh air introduction port 11, and the desorbed evaporated fuel The purge gas containing R is sucked into the intake passage 2 downstream of the throttle valve 3 through the purge passage 9, and thereafter, combustion processing is performed in the cylinder of the engine 1.

Next, a purge control valve (solenoid valve)
The 10 control devices will be described in detail. FIG. 3 is a hardware configuration diagram of the solenoid valve control device. A transistor 13 as a driving switching element is provided in series on the ground side of the energizing circuit of the solenoid valve 10. The transistor 13 is a microcomputer (CP).
U) ON / OFF is controlled by the duty signal from 14.

Further, a pull-down resistor 15 is connected in parallel to the driving transistor 13, and during the OFF period of the driving transistor 13, a small current smaller than a valve opening current flows through the solenoid valve 10 via the pull-down resistor 15. It is like this. A differential amplifier 16 is provided so as to detect the potential difference (difference between the terminal voltages V ₁ and V ₀ ) across the coils of the solenoid valve 10, and its output V ₂ is input to the CPU 14.

Here, the CPU 14 is shown in FIG.
Also, the solenoid valve 10 is duty-controlled by performing the arithmetic processing shown in the flowchart of FIG. Figure 1 CPU
14 is a functional block diagram showing the contents of arithmetic processing of 14, which includes a target duty calculation means 101, a resistance equivalent value detection means 102, an averaging means 103, a correction value calculation means 104, a duty correction means 105, and a driving means 106. Further, a prohibiting means 107 is provided for the resistance equivalent value detecting means 102.

The target duty calculating means 101 is responsive to the intake air flow rate Q detected by the air flow meter 4,
The target duty A = f (Q) is calculated. The resistance equivalent value detecting means 102 includes a differential amplifier 16 and detects the potential difference (V ₂ ) across the coil of the solenoid valve 10 as the coil resistance equivalent value of the solenoid valve.

The averaging means 103 is a resistance equivalent value detecting means 10
The coil resistance equivalent value V ₂ detected by ₂ is averaged (annealed). The correction value calculation means 104 calculates a correction value (increment of duty) B based on the average value of the coil resistance equivalent value V ₂ averaged by the averaging means 103 such that the larger it is, the larger it becomes. To do.

In principle, as shown in the relationship between the duty signal and the drive current in FIG. 6, when the duty signal changes from OFF to ON, the drive current changes from the valve opening current due to the delay in the rise of the drive current. However, if the coil resistance equivalent value increases, the rise of the drive current will be further delayed, and the valve opening delay time will change depending on the coil resistance equivalent value. Accordingly, the correction value (increment of duty) B is set so that the output duty is increased by the amount that the valve opening delay occurs.

The duty correction means 105 adds the correction value B to the target duty A and outputs the output duty DUTY =
Calculate A + B. The driving means 106 outputs the output duty D
A duty signal corresponding to UTY is output to control the ON / OFF of the transistor 13. The prohibiting means 107 prohibits the resistance equivalent value detecting means 102 from detecting the resistance equivalent value V ₂ when the output duty DUTY is a predetermined value (for example, 90%) or more.

Next, a more specific arithmetic processing content is shown in FIG.
And it demonstrates according to the flowchart of FIG. FIG. 4 shows a sampling routine. In step 1 (denoted as S1 in the drawing; the same applies hereinafter), it is determined whether or not a predetermined sampling timing is reached, and if the sampling timing is reached, the process proceeds to step 2. The sampling timing is set immediately before switching from OFF to ON in each cycle of the duty signal.

At step 2, it is judged whether the prohibition flag F is set (F = 1). If F = 0,
Steps 3 and 4 are executed. In step 3, the output V ₂ of the differential amplifier 16 corresponding to the potential difference (V ₁ −V ₀ ) across the coil is A / D converted and read as the coil resistance equivalent value. This portion corresponds to the coil resistance equivalent value detecting means.

In step 4, the coil resistance equivalent value V₂of
As the averaging process, V ₂Calculate / update average value
To be new. This part corresponds to the averaging means. (V₂Average value) = [(V₂Average value) x (α-1) +
V₂] / Α However, α is an averaging ratio constant, and α> 1. On the other hand,
If the prohibition flag F is set by the judgment at Step 2.
If (F = 1), V₂Reading and averaging
This routine is ended without prompting.

FIG. 5 shows a duty control routine. In step 11, it is determined whether or not a predetermined purge permission condition is satisfied,
If it is a permit condition, the process proceeds to step 12. In step 12, the intake air flow rate Q detected by the air flow meter 4 is read.

In step 13, the target duty A = f (Q) is proportionally calculated according to the intake air flow rate Q. If necessary, altitude correction etc. are also performed. This portion corresponds to the target duty calculation means. In step 14, the coil resistance equivalent value V calculated by the routine of FIG.
Based on the average value of ₂ , the correction value (increment of duty) B is searched by referring to the table. Here, the correction value B is increased as the average value of the coil resistance equivalent value V ₂ increases. This portion corresponds to the correction value calculation means.

In step 15, the correction value B is added to the target duty A to calculate the output duty DUTY = A + B. This portion corresponds to duty correction means. On the other hand, if it is determined in step 11 that the purge permission condition is not satisfied, the output duty DUTY is set to 0 in step 16.
In step 17, the output duty DUTY determined in step 15 or step 16 is set in a predetermined register and a corresponding duty signal is output to the driving transistor 13. This portion corresponds to the driving means.

Finally, in step 18, the output duty DUTY is compared with a predetermined value (for example, 90%), and DUTY <
If it is a predetermined value, the prohibit flag F is reset (F = 0) in step 19, but if DUTY ≧ predetermined value, the prohibit flag F is set (F = 1) in step 20. Accordingly, when the output duty DUTY is a predetermined value (for example, 90%) or more, that is, when the OFF period is short, the small current is not stable and there is a possibility of erroneous detection, so the prohibition flag F is set (F = 1). However, the reading (and averaging process) of V ₂ is prohibited by the determination in step 2 of the routine of FIG. 4 to improve the control accuracy. Of course, even if reading of V ₂ (and averaging processing) is prohibited, appropriate correction is made based on the V ₂ average value up to that point.

If the purge permission condition is not satisfied, the output duty DUTY becomes 0 in step 11 → 16.
At this time, the prohibition flag F = 0 is set in steps 18 → 19, and V ₂ is read and averaged in steps 2 → 3, 4 of the routine of FIG. Therefore, the purge permission condition is satisfied and the purge is started after at least a certain amount of time has passed since the engine was started, but V ₂ is read and the averaging process is performed until the purge is started. Immediately after the purge permission condition is satisfied, appropriate correction can be performed based on the V ₂ average value.

In the present embodiment, the potential difference across the coil is detected as the coil resistance equivalent value. However, if the resistance value of the pull-down resistor 15 is R ₀ , the terminal voltage V ₁ on the + side of the coil is And the negative terminal voltage V ₀ , the coil resistance R can be accurately obtained using the following equation. Therefore, the coil resistance may be detected in this way.

R = [(V ₁ −V ₀ ) / V ₀ ] × R _{0 Further} , although the example applied to the purge control valve of the engine has been described above, the present invention can be applied to solenoid valves in general. However, by applying it to the purge control valve of the engine, the purge flow rate control by the purge control valve used in an environment with a large temperature difference can be realized more accurately.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram of an evaporated fuel processing device.

FIG. 3 is a hardware configuration diagram of a solenoid valve control device.

FIG. 4 is a flowchart of a sampling routine.

FIG. 5 is a flowchart of a duty control routine.

FIG. 6 Principle diagram of duty correction

[Explanation of symbols]

1 engine 2 Intake passage 4 Air flow meter 6 canisters 7 Fuel tank 9 Purge passage 10 Purge control valve (solenoid valve) 12 Control unit 13 Drive transistor 14 CPU 15 pull-down resistor 16 differential amplifier 101 Target duty calculation means 102 Resistance equivalent value detection means 103 Averaging means 104 Correction value calculation means 105 Duty correction means 106 Drive means 107 Prohibition measures

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-118463 (JP, A) JP-A-60-132182 (JP, A) JP-A-7-77271 (JP, A) 14757 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16K 31/06-31/11

Claims (5)

(57) [Claims] 1. A solenoid valve control device for controlling ON / OFF of a drive switching element, which is interposed in series with an energizing circuit of a solenoid valve, according to an output duty based on a target duty, and is connected in parallel to the drive switching element. The pull-down resistor for supplying a small current less than the valve opening current to the solenoid valve during the OFF period of the drive switching element and the coil resistance equivalent value of the solenoid valve is detected by the small current during the OFF period of the drive switching element. A solenoid valve control device comprising: a resistance equivalent value detection means; and a duty correction means for correcting an output duty according to the detected coil resistance equivalent value of the solenoid valve. 2. The resistance equivalent value detecting means detects the potential difference between both ends of the solenoid valve coil during the OFF period of the drive switching element as the coil resistance equivalent value of the solenoid valve. Item 1. A solenoid valve control device according to item 1. 3. The coil resistance equivalent value of the solenoid valve detected by the resistance equivalent value detecting means is averaged between the resistance equivalent value detecting means and the duty correcting means and input to the duty correcting means. The solenoid valve control device according to claim 1 or 2, further comprising an averaging means. 4. The resistance equivalent value detecting means is provided with prohibiting means for prohibiting the detection of the coil resistance equivalent value when the output duty is equal to or more than a predetermined value. The solenoid valve control device according to any one of the above. 5. The solenoid valve is a purge control valve provided in a purge passage from a canister for adsorbing fuel vapor from a fuel tank to an intake passage of an engine. The solenoid valve control device according to any one of claims.