JPH07293363A - Vapor fuel processing device for engine - Google Patents

Abstract

PURPOSE:To eliminate variations in air-fuel ratio between cylinders to improve the operability of an engine by setting a purge-passage opening/closing duty frequency based on the engine intake air pulsation frequency detected by an intake air pulsation frequency detecting means. CONSTITUTION:A control unit 6 judges whether the purge must be applied or not during operation of an engine 1 based on a map of a fuel-purging region and non-fuel-purging region determined from engine speed, throttle negative pressure, etc. In this case, when the control unit judges whether or not the purge must be applied, it reads the output of an air flow meter 33 to perform Fourier transformation, and performs the frequency analysis to detect an intake air pulsation. Then, the control unit sets a duty frequency related to the valve opening operation of an opening and closing valve in a purge-passage 24 so that the duty frequency can be equal to the intake air pulsating frequency. Thus, even when purge-pulsation occurs by opening and closing the opening and closing valve when the purge is performed from an evaporative emission processing device 21, purge-air can be evenly supplied to respective cylinders by performing the purge from the evaporative emission processing device 21 concurrently with the intake air pulsation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine fuel vapor treatment system, and more particularly to a system for supplying fuel vapor produced in a fuel tank to an engine intake system to prevent its emission into the atmosphere.

[0002]

2. Description of the Related Art Conventionally, after the evaporated fuel generated in a fuel tank is once adsorbed and collected by a canister, the evaporated fuel adsorbed and collected by the canister is purged (desorbed), and the purge air is purged by a purge passage. An evaporative fuel processing device has been proposed which is supplied to an intake system of an engine via a fuel cell and prevents the evaporative fuel in a fuel tank from being diffused into the atmosphere (Japanese Patent Laid-Open No. 6-58242).
2-962, etc.).

As described above, in the device for supplying the purge air from the canister to the intake system of the engine, the above-mentioned purge air is added to the normal air-fuel mixture, so that it is irrelevant to the operating conditions of the engine. If a configuration is adopted in which a constant amount of purge air is supplied, there is a possibility that a large air-fuel ratio deviation will occur. Therefore, the amount of purge air is changed according to the operating conditions of the engine.To this end, a stepping valve that is opened and closed by a stepping motor or the like is provided in the purge passage, and the opening degree of the stepping valve is changed from the operating conditions. There is one in which the purge air amount is adjusted by controlling the opening so that the duty ratio corresponds to the required purge flow rate.

However, since the stepping valve is expensive, in response to the demand for cost reduction, a duty control type opening / closing valve for opening / closing the purge passage is provided, and the opening duty of the opening / closing valve depends on the operating conditions of the engine. In some cases, the amount of purge air is adjusted by controlling the amount of purge air.

[0005]

By the way, in an evaporative fuel processing system in which the valve opening duty of an on-off valve is controlled in accordance with the operating conditions of an engine, a purge pulsation occurs due to the opening and closing of a purge passage. The amount of purge air sucked in the cylinders varies, and thus the air-fuel ratio varies among the cylinders.

Therefore, there is a structure in which the opening and closing of the purge passage is performed as high as possible in order to surely avoid the purge pulsation, but since the number of ON / OFF operations per unit time greatly increases, the valve seat portion May cause a problem in durability. There is also one that controls the frequency of the duty control in accordance with, for example, the rotation speed of the engine, but the air in the intake pipe may have a complicated flow, and the distribution of the purge air amount to each cylinder may be incomplete. There is.

The present invention has been made in view of the above problems. By opening and closing the purge passage by means of duty-controlled purge passage opening / closing means, purge air is supplied to the intake system of the engine via the purge passage. An object of the present invention is to ensure that the purge air amount is distributed to each cylinder even in the case where a purge pulsation occurs in the processing apparatus, thereby eliminating the air-fuel ratio variation among the cylinders and improving the drivability.

[0008]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, the evaporated fuel in the fuel tank is adsorbed and collected, and the adsorbed and collected evaporated fuel is purged. An evaporative fuel treatment system for an engine, comprising a canister for supplying purge air to an intake system of an engine through a purge passage, wherein a duty control type purge passage opening / closing means for opening / closing the purge passage and an intake pulsation frequency of the engine are provided. The intake pulsation frequency detecting means for detecting, and the duty frequency setting means for setting the opening / closing duty frequency of the purge passage opening / closing means based on the intake pulsation frequency of the engine detected by the intake pulsation frequency detecting means are configured. .

Further, according to the invention of claim 2, the intake pulsation frequency detecting means detects the intake pulsation frequency based on the frequency of the output signal of the intake air flow rate detected by the intake air flow rate detecting means. You may
Fuel generation processing device. Further, as the configuration according to the invention described in claim 3, the intake pulsation frequency detecting means may detect the intake pulsation frequency based on the frequency of the output signal of the intake pressure detected by the intake pressure detecting means.

Further, as a structure according to the invention described in claim 4, the duty frequency setting means may set the opening / closing duty frequency to be equal to the intake pulsation frequency. Further, as a configuration according to the invention of claim 5, the duty frequency setting means may set the opening / closing duty frequency to a value obtained by dividing the intake pulsation frequency by an integer multiple of the number of cylinders.

[0011]

According to the first aspect of the present invention, the opening / closing duty frequency of the purge passage opening / closing means is set by the duty frequency setting means in order to obtain a predetermined amount of purge air corresponding to the intake pulsation frequency of the engine. Therefore, the purge passage is also opened / closed based on the intake air pulsation of the engine, and the purge air supplied through the purge passage is also supplied based on the intake air pulsation of the engine. Will be distributed to.

Further, when the intake pulsation occurs, the frequency of the output signal of the intake air flow rate also pulsates, so that the intake pulsation frequency detecting means detects the intake air flow rate detecting means. The intake pulsation frequency can be detected based on the frequency of the output signal of the intake air flow rate. Further, when the intake pulsation occurs, the frequency of the output signal of the intake pressure also pulsates, so that the intake pulsation frequency detecting means has the effect that the intake pulsation frequency detecting means detects the intake pressure of the intake pressure detected by the intake pressure detecting means. The intake pulsation frequency can be detected based on the frequency of the output signal.

As an operation of the invention according to claim 4, the duty frequency setting means sets the opening / closing duty frequency equal to the intake pulsation frequency,
Purge air is evenly supplied to each cylinder, and thus the amount of purge air is reliably distributed to each cylinder. Further, according to the invention of claim 5, the duty frequency setting means sets the opening / closing duty frequency to a value obtained by dividing the intake pulsation frequency by an integer multiple of the number of cylinders, so that all cylinders burn for a predetermined cycle. During this period, a predetermined amount of purge air is continuously supplied, and the purge air is not supplied only to a specific cylinder, so that the purge air amount is reliably distributed to each cylinder.

[0014]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is drawn into the engine 1 through a throttle chamber 2 and an intake manifold 3. The throttle chamber 2 is provided with a throttle valve 4 interlocking with an accelerator pedal (not shown) to control the intake air amount of the engine 1.

An electromagnetic fuel injection valve 5 is provided for each cylinder at a branch portion of the intake manifold 3, and fuel which is pressure-fed from a fuel pump (not shown) and is controlled to a predetermined pressure by a pressure regulator is introduced into the intake manifold 3.
Inject and supply. The fuel injection valve 5 is intermittently driven to open according to an injection pulse signal sent from a control unit 6 having a built-in microcomputer, and the fuel is injected according to the pulse width of the injection pulse signal calculated by the control unit 6. The injection amount is controlled.

A spark plug 7 is provided in each cylinder of the engine 1, and a high voltage generated in an ignition coil 8 is sequentially applied to these cylinders through a distributor 9, whereby spark ignition is performed. Ignite and burn the air-fuel mixture. Here, the ignition coil 8 is configured such that the generation timing of the high voltage is controlled via the attached power transistor 10.

The throttle valve 4 has an opening TVO.
Sensor that detects the pressure with a potentiometer
11 are attached. The crank angle sensor 12 built in the distributor 9 outputs a detection signal for each predetermined crank angle, and the engine rotation speed Ne can be calculated based on the detection signal.

Further, a water temperature sensor 13 for detecting a cooling water temperature Tw is provided in the cooling water jacket of the engine 1, and an exhaust manifold 14 has exhaust gas closely related to the air-fuel ratio of the intake air-fuel mixture of the engine 1. An oxygen sensor 15 for detecting the oxygen concentration therein is provided, and further, an air flow meter 33 for detecting the intake air amount Qa of the engine 1 is provided in the intake duct portion on the upstream side of the throttle chamber 2.

Further, in the throttle chamber 2 downstream of the throttle valve 4, there is a throttle negative pressure (boost negative pressure) PB.
A pressure sensor 35 for detecting is provided. On the other hand, the engine 1 is provided with an evaporative gas treatment device 21 for preventing the evaporative fuel generated in the fuel tank 20 from being diffused into the atmosphere. The evaporative gas treatment device 21 temporarily adsorbs and collects the evaporative gas of the fuel generated in the fuel tank 20 on an adsorbent 23 such as activated carbon filled in a canister 22, and then adsorbs the adsorbent 23 on the adsorbent 23. The fuel is purged and the purge air is supplied to the intake passage downstream of the throttle valve 4 via the purge passage 24.

Evaporative fuel in the fuel tank 20 is introduced into the canister 22 through an evaporative gas passage 26 provided with a check valve 25 that opens when the positive pressure in the fuel tank 20 exceeds a predetermined value. In addition, an ON / OFF type on-off valve 28 is provided in the purge passage 24. The opening / closing valve 28 is intermittently driven to open in response to a valve opening pulse signal sent from the control unit 6, and the amount of evaporated fuel introduced varies depending on the pulse width of the valve opening pulse signal calculated by the control unit 6. It is controlled.

Therefore, by controlling the ON / OFF of the opening / closing valve 28 by duty, it is possible to variably control the introduction amount of the evaporated fuel. That is, the on-off valve 28 functions as a duty-controlled purge passage opening / closing means. Here, the on-off valve by the control unit 6
The state of the opening / closing control of 28 will be described with reference to the flowchart of FIG.

In the present embodiment, the functions as the intake pulsation frequency detecting means and the duty frequency setting means according to the first aspect are provided by software in the control unit 6 as shown in the flow chart of FIG. The air pulsation frequency detecting means corresponds to the air flow meter 33. The flowchart shown in FIG.
1 shows a first embodiment according to the present invention. First, in step 1 (indicated as S1 in the figure; the same applies hereinafter), it is determined whether or not the evaporative gas treatment device 21 should be purged.
That is, the control unit 6 is provided with a map of the fuel purge area and the non-fuel purge area determined by the engine speed Ne and the throttle negative pressure (boost negative pressure) PB downstream of the throttle valve 4, for example. Based on the map, it is possible to determine whether or not the evaporative gas processing device 21 should be purged.

When it is determined that the area is to be purged, the process proceeds to step 2. In step 2, the output AF of the air flow meter 33 that detects the intake air amount Qa
Read M. In step 3, the Fourier transform of the output AFM is performed, the frequency analysis of the output AFM is performed, and the pulsation of the output AFM is detected. Here, when the intake pulsation occurs, the frequency of the output AFM of the air flow meter 33 that detects the intake air amount Qa also pulsates. Therefore, by detecting the pulsation of the output AFM in step 3, the intake pulsation frequency f can be detected.

That is, the step 3 constitutes the intake pulsation frequency detecting means according to claim 2. In step 3, instead of performing the Fourier transform of the output AFM, the point at which the first-order differential value of the output AFM becomes 0 (that is, the point at which the output AFM is inverted due to the intake pulsation) per unit time. It is also possible to measure the number of times and detect the intake pulsation frequency f.

In step 4, the duty frequency X for opening the on-off valve 28 is set equal to the intake pulsation frequency f (X = f) detected in step 3. That is, the step 4 constitutes duty frequency setting means according to claim 4. Then, in step 5, the drive frequency of the on-off valve 28 is changed.

Therefore, in the first embodiment, even if the pulsation of the purge occurs due to the opening / closing of the opening / closing valve 28 when purging from the evaporative gas treatment apparatus 21, the evaporative gas treatment apparatus 21 simultaneously with the intake pulsation. Therefore, the purge air is evenly supplied to each cylinder, and the purge air amount is reliably distributed to each cylinder.Therefore, the air-fuel ratio variation between the cylinders is eliminated, and the drivability is improved. It will be improved.

Here, in the first embodiment described above, in step 4, the duty frequency X relating to the opening of the on-off valve 28 is set equal to the intake pulsation frequency f detected in step 3, but As a second embodiment according to the invention, in step 4, the duty frequency X for opening the on-off valve 28 is set to a value obtained by dividing the intake pulsation frequency f detected in step 3 by an integer multiple of the number of cylinders. (X = f / (K × v); where v is the number of cylinders of the engine 1 and K is an integer).

That is, step 4 according to the second embodiment is
The duty frequency setting means according to claim 5 is configured. Then, in step 5, the drive frequency of the on-off valve 28 is changed as in the first embodiment. So,
In the second embodiment, even if the pulsation occurs in the purge due to the opening / closing of the opening / closing valve 28 when purging from the evaporative gas treatment device 21, the opening / closing valve 28 is in the open state while all cylinders burn for a predetermined cycle. Since a predetermined amount of purge air is continuously supplied, the pulsation is prevented from affecting only a specific cylinder, the purge air is uniformly supplied to each cylinder, and thus the purge air amount is distributed to each cylinder. Is reliably performed, the air-fuel ratio variation between the cylinders is eliminated, and the drivability is improved.

Next, the control content of the third embodiment according to the third aspect of the invention will be described with reference to the flow chart shown in FIG. The steps having the same functions as those of the flowchart shown in FIG. 3 are designated by the same step numbers and the description thereof will be omitted. In the third embodiment, in step 12, the output PBM of the pressure sensor 35 that detects the throttle negative pressure (boost negative pressure) PB is read.

In step 13, the Fourier transform of the output PBM is performed, the frequency analysis of the output PBM is performed, and the pulsation of the output PBM is detected. Here, when the intake pulsation occurs, the frequency of the output PBM of the pressure sensor 35 for detecting the throttle negative pressure PB also pulsates, so by detecting the pulsation of the output PBM in the step 13,
The intake pulsation frequency f can be detected.

That is, the step 13 constitutes the intake pulsation frequency detecting means according to claim 3. In step 13, instead of performing the Fourier transform of the output PBM, the point at which the first-order differential value of the output PBM becomes 0 (that is, the point at which the output PBM is inverted by the intake pulsation) per unit time. It is also possible to measure the number of times and detect the intake pulsation frequency f.

Also in the third embodiment, step 4 is performed.
Then, it goes without saying that the duty frequency X may be set equal to the intake pulsation frequency f, or may be set to a value obtained by dividing the intake pulsation frequency f by an integral multiple of the number of cylinders. Therefore, in the third embodiment as well, the purge air amount is reliably distributed to the cylinders, the air-fuel ratio variation among the cylinders is eliminated, and the drivability is improved.

[0033]

As described above, the evaporated fuel in the fuel tank is adsorbed and collected, the adsorbed and collected evaporated fuel is purged, and the purge air is supplied to the intake system of the engine through the purge passage. In the evaporated fuel processing apparatus for an engine provided with a canister, as an effect of the invention of claim 1, the purge air supplied through the purge passage is also supplied based on the intake pulsation of the engine.
The purge air is distributed to each cylinder together with the intake air, and even if the duty control type purge passage opening / closing means for opening / closing the purge passage is used, the purge air amount is surely distributed to each cylinder. The air-fuel ratio variation in the is eliminated, and the drivability is improved accordingly.

Further, as an effect of the invention described in claim 2, it becomes possible to detect the intake pulsation frequency based on the frequency of the output signal of the intake air flow rate, and by detecting the pulsation of the output signal of the intake air flow rate, Since the purge air amount is reliably distributed to each cylinder, there is an effect that it is possible to eliminate variations in the air-fuel ratio among the cylinders.

Further, as an effect of the invention described in claim 3, it becomes possible to detect the intake pulsation frequency based on the frequency of the intake pressure output signal, and by detecting the pulsation of the intake pressure output signal, the purge air amount can be detected. That is, the distribution to the respective cylinders is surely performed, and there is an effect that it is possible to eliminate the variation in the air-fuel ratio between the cylinders. Further, as an effect of the invention described in claim 4, since the opening / closing duty frequency is set to be equal to the intake pulsation frequency, the purge is performed from the evaporated fuel processing device at the same time as the intake pulsation. Since the purge air is supplied, it is possible to reliably distribute the purge air amount to each cylinder.

Further, as an effect of the invention described in claim 5, since the opening / closing duty frequency is set to a value obtained by dividing the intake pulsation frequency by an integral multiple of the number of cylinders, while all the cylinders burn in a predetermined cycle, Since a fixed amount of purge air is continuously supplied, it is possible to prevent the pulsation from affecting only a specific cylinder, and thus it is possible to reliably distribute the purge air amount to each cylinder.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flow chart showing opening / closing control of the opening / closing valve according to the first and second embodiments of the present invention.

FIG. 4 is a flowchart showing opening / closing control of an opening / closing valve according to a third embodiment of the present invention.

[Explanation of symbols]

 1 engine 6 control unit 12 crank angle sensor 20 fuel tank 21 evaporative gas treatment device 22 canister 23 adsorbent 24 purge passage 28 open / close valve 33 air flow meter 35 pressure sensor

Claims (5)

[Claims] 1. An engine having a canister that adsorbs and collects evaporated fuel in a fuel tank, purges the adsorbed and collected evaporated fuel, and supplies the purge air to an intake system of the engine through a purge passage. An evaporative fuel processing system, wherein a duty control type purge passage opening / closing means for opening / closing the purge passage, an intake pulsation frequency detecting means for detecting an intake pulsation frequency of the engine, and an engine detected by the intake pulsation frequency detecting means And a duty frequency setting means for setting the opening / closing duty frequency of the purge passage opening / closing means on the basis of the intake pulsation frequency of the fuel vapor treatment apparatus for an engine. 2. The engine according to claim 1, wherein the intake pulsation frequency detecting means detects the intake pulsation frequency based on the frequency of the output signal of the intake air flow rate detected by the intake air flow rate detecting means. Evaporative fuel processor. 3. The engine evaporation according to claim 1, wherein the intake pulsation frequency detecting means detects the intake pulsation frequency based on the frequency of the output signal of the intake pressure detected by the intake pressure detecting means. Fuel processor. 4. The evaporated fuel processing apparatus for an engine according to claim 1, wherein the duty frequency setting means sets the opening / closing duty frequency equal to the intake pulsation frequency. 5. The duty frequency setting means sets the opening / closing duty frequency to a value obtained by dividing the intake pulsation frequency by an integer multiple of the number of cylinders. Evaporative fuel processor for engine.