JP2003278590A - Evaporative fuel processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporative fuel processing device for specifying the relationship between the output of an evaporative emission concentration sensor disposed on the intake side and the evaporative emission concentration at a non-atmospheric point. <P>SOLUTION: This device is provided with a purge mechanism for purging evaporative fuel to an intake passage. The device is provided with an evaporative emission concentration sensor for detecting the evaporative emission concentration in gas flowing through the intake passage and an exhaust side sensor for generating output depending on the exhaust air-fuel ratio. According to the output of the exhaust side sensor, the fuel injection quantity is feedback controlled so that the exhaust air-fuel ratio reaches a stoichiometric air-fuel ratio. Under the execution of feedback control, the evaporative emission concentration is estimated depending on the loss proportion of the fuel injection quantity due to correction (step 106, 108). The non-atmospheric point is specified by making the estimated value of the evaporative emission concentration correspond to the output of the evaporative emission concentration sensor (step 112). The output of the evaporative emission concentration sensor is composed of the atmospheric point and the non-atmospheric point (step 116). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor processing apparatus, and more particularly to a fuel vapor processing apparatus that processes fuel vapor generated in an internal combustion engine by purging it into an intake passage of the engine.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-10-212992.
As disclosed in the publication, there is known a device for capturing evaporated fuel generated in a fuel tank of an internal combustion engine with a canister. This device is equipped with a mechanism for purging the vaporized fuel captured by the canister into the intake passage during operation of the internal combustion engine. Therefore, according to the above-mentioned conventional device, the evaporated fuel generated in the fuel tank can be treated as the fuel without being discharged to the outside air.

The above-mentioned conventional apparatus is also provided with an oxygen concentration sensor for detecting the oxygen concentration in the gas flowing inside the intake passage of the internal combustion engine, and the inside of the intake passage is detected based on the output of the oxygen concentration sensor. The evaporative concentration of can be detected. Then, the above-mentioned conventional device is based on the evaporation concentration detected in this way during the purge of the evaporated fuel,
In order to reduce the amount of purged fuel from the fuel injection amount,
The feed-forward reduction correction of the fuel injection amount is performed.
Therefore, according to the conventional device, the evaporated fuel can be purged without causing the air-fuel ratio to be rough.

[0004]

FIG. 8 shows the output of the oxygen concentration sensor (vertical axis) and the evaporation concentration in the intake passage (horizontal axis).
It is a characteristic view which shows the relationship with. As shown in this figure, the output characteristics of the oxygen concentration sensor cannot always be treated as constant due to variations due to individual differences of the sensor and deterioration of durability of the sensor. In the type of device that corrects the fuel injection amount in a feedforward manner using the output of the oxygen concentration sensor placed in the intake passage, the output error of the sensor directly affects the exhaust air-fuel ratio, so the above variations and durability It is desirable that the effects of changes be eliminated by calibrating the output characteristics.

In correcting the output characteristics of the oxygen concentration sensor, at least one point (hereinafter, referred to as "non-existence point") in addition to the point where the evaporative concentration is zero (detection gas is the atmosphere) It is preferable that the relationship between the output of the sensor and the oxygen concentration (evaporation concentration) can be specified by "atmosphere point". However, with the conventional technology, it was not possible to specify the sensor output and the evaporation concentration at such a non-atmospheric point. Therefore, in the above-mentioned conventional device, it is difficult to accurately correct the output characteristics of the oxygen concentration sensor.

The present invention has been made in order to solve the above problems, and can specify the relationship between the output of the evaporation concentration sensor disposed on the intake side and the evaporation concentration at a non-atmospheric point. An object is to provide an evaporated fuel processing device.

[0007]

The invention according to claim 1 is
An evaporative fuel treatment device for treating evaporative fuel generated in an internal combustion engine, comprising: a purge means for purging the evaporative fuel into an intake passage, and an evaporative concentration for producing an output having a correlation with an evaporative concentration in gas flowing through the intake passage A sensor,
An exhaust side sensor that emits an output according to the exhaust air-fuel ratio, a fuel injection valve that injects fuel to an internal combustion engine, and a feedback for setting the exhaust air-fuel ratio to a desired air-fuel ratio based on the output of the exhaust side sensor Feedback control means for executing control, evaporation concentration estimation means for estimating the evaporation concentration in the gas flowing through the intake passage based on a fuel injection control amount during execution of the feedback control, and an estimated value of the evaporation concentration. And an associating unit that associates the output of the evaporation concentration sensor with each other.

According to a second aspect of the present invention, there is provided the evaporated fuel processing apparatus according to the first aspect, further comprising basic fuel injection amount calculation means for calculating a basic fuel injection amount for realizing the desired air-fuel ratio, The feedback control means includes a reduction correction means for performing a reduction correction on the basic fuel injection amount so that the purged amount of the evaporated fuel is offset, and the evaporation concentration estimation means changes the basic fuel injection amount to the basic fuel injection amount by the reduction correction means. The evaporation concentration is estimated based on the applied reduction correction ratio.

According to a third aspect of the present invention, there is provided an evaporative fuel treatment apparatus for treating evaporative fuel produced in an internal combustion engine, which comprises purging means for purging the evaporative fuel into the intake passage.
An evaporation concentration sensor that outputs an output having a correlation with an evaporation concentration in the gas flowing through the intake passage, an exhaust side sensor that outputs an output according to an exhaust air-fuel ratio, and a fuel injection valve that injects fuel to an internal combustion engine, Based on the output of the exhaust side sensor, a stoichiometric state forming means for creating a stoichiometric state in which a desired air-fuel ratio is realized only by the evaporated fuel without using the injected fuel, and the evaporation state when the stoichiometric state is formed. It is characterized by comprising an evaporation concentration estimating means for estimating the concentration as a value corresponding to the desired air-fuel ratio, and an associating means for associating the estimated value of the evaporation concentration with the output of the evaporation concentration sensor.

According to a fourth aspect of the present invention, there is provided the evaporated fuel processing apparatus according to the third aspect, wherein the internal combustion engine is mounted on a hybrid vehicle and a drive state detecting means for detecting a drive state of the hybrid vehicle, and the internal combustion engine. The zero injection amount permission means for permitting execution of the feedback control with the fuel injection amount set to 0 only in a situation where the output of is not required as the driving force of the vehicle.

The invention according to claim 5 is the invention according to claim 3 or 4.
In the evaporative fuel treatment apparatus described above, so that the exhaust air-fuel ratio becomes a desired air-fuel ratio, a feedback control means for feedback controlling the fuel injection amount based on the output of the exhaust side sensor is provided, and the stoichiometric state forming means is During execution of the feedback control, a purge control amount changing means for increasing the purge amount of the evaporated fuel until the fuel injection amount becomes 0 is included.

The invention according to claim 6 is the evaporated fuel processing apparatus according to any one of claims 1 to 5, wherein the desired air-fuel ratio is a stoichiometric air-fuel ratio.

According to a seventh aspect of the present invention, there is provided the evaporated fuel processing apparatus according to the sixth aspect, wherein the exhaust side sensor determines whether the exhaust air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio. It is an oxygen concentration sensor that emits a different output.

The invention according to claim 8 is the fuel vapor processing apparatus according to any one of claims 1 to 7, further comprising an engine state detecting means for detecting an operating state of the internal combustion engine, wherein the evaporation concentration estimation is performed. Means, stability condition determining means for determining whether the operating state of the internal combustion engine is stable over a predetermined period,
An estimation permission unit that permits estimation of the evaporation concentration when it is determined that the operating state of the internal combustion engine is stable over a predetermined period.

According to a ninth aspect of the invention, there is provided the evaporated fuel processing apparatus according to any one of the first to eighth aspects, wherein the output of the evaporation concentration sensor and the estimation of the evaporation concentration which are associated by the associating means. A non-atmosphere point grasping means for grasping a combination with a value as a non-atmosphere point, an output emitted from the evaporation concentration sensor to the atmosphere, and an atmosphere point grasping means for grasping a combination of zero evaporation concentration as an atmosphere point, Output characteristic grasping means for grasping the output characteristic of the evaporation concentration sensor based on the non-atmospheric point and the atmospheric point.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. It should be noted that elements common to each drawing are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1. FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a canister 10. A fuel tank (not shown) is connected to the canister 10 via a vapor passage 12. Canister 10
Is capable of adsorbing and holding the vaporized fuel (vapor) generated inside the fuel tank and flowing in through the vapor passage 12.

The canister 10 is provided with an atmosphere introducing hole 14 and a purge passage 16 is in communication therewith.
The purge passage 16 communicates with the intake passage 18 of the internal combustion engine at the other end. Hereinafter, the communicating portion between the purge passage 16 and the intake passage 18 will be referred to as the purge port 20.

In the middle of the purge passage 16, the purge VSV (Va
A cuum Switching Valve) 22 is arranged. Purge V
The SV 22 is a control valve that is opened and closed at an arbitrary duty ratio by being driven by duty, and as a result, realizes a substantially arbitrary opening degree.

The intake passage 18 is provided with a throttle valve 24 upstream of the purge port 20. A surge tank 26 is provided downstream of the purge port 20. The surge tank 26 is fitted with an evaporation concentration sensor 28 for detecting the concentration of evaporated fuel in the gas flowing therein.

The evaporation concentration sensor 28 is used in the surge tank 2
This can be realized by an oxygen concentration sensor that detects the oxygen concentration in the gas flowing through the inside of the cylinder 6. This oxygen concentration sensor includes a sensor element that pumps oxygen in the detection gas and emits an output according to the concentration, and a heater that heats the sensor element. When the gas containing the fuel is introduced around the oxygen concentration sensor, the fuel burns due to the heat of the heater, and oxygen in the gas is consumed at that time. As a result, the output emitted from the sensor element is the concentration of the fuel in the gas,
That is, it corresponds to the evaporation concentration. Therefore,
The oxygen concentration sensor described above can detect the evaporation concentration in the gas flowing through the surge tank 26.

The evaporation concentration sensor 28 can also be realized by an HC sensor that detects the HC concentration in the gas flowing through the surge tank 26. The HC sensor includes an ultrasonic signal transmitter and a receiver, and can measure the speed at which the ultrasonic signal propagates in the detection gas. The propagation velocity of the ultrasonic signal corresponds to the concentration of HC contained in the gas. Therefore, according to the HC sensor, the surge tank 2
It is possible to detect the HC concentration in the gas flowing through 6, that is, the evaporative concentration.

The output of the evaporation concentration sensor 28 generally has pressure dependency. Therefore, the system of the present embodiment has a mechanism for measuring the pressure in the surge tank 26 and a function of correcting the output of the evaporation concentration sensor 28 based on the measured value of the pressure. However, since those mechanisms and functions are not related to the essence of the present invention, detailed description thereof will be omitted here.

The intake passage 18 communicates with an intake port 34 of the internal combustion engine 32 further downstream of the surge tank 26. A fuel injection valve 36 that injects fuel into the internal combustion engine 32 is arranged in the intake port 34. An exhaust gas O ₂ sensor 39 is arranged in the exhaust passage 38 of the internal combustion engine 32.

As shown in FIG. 1, the system of this embodiment includes an ECU (Electronic Control Unit) 40.
The purge VSV 22, the fuel injection valve 36, the evaporation concentration sensor 28, the exhaust O ₂ sensor 39, and the like described above are all E
It is electrically connected to the CU 40.

In this embodiment, the ECU 40 performs, as basic control, feedback control of the fuel injection amount using the output of the exhaust O ₂ sensor 39, control of the opening degree of the purge VSV 22 (purge control), and evaporation concentration sensor 28. The reduction correction of the fuel injection amount using the output of is executed. Hereinafter, the contents of these basic controls executed by the ECU 40 will be described in order.

[0027] In the exhaust O ₂ fuel injection quantity feedback control using the output of the sensor 39] exhaust O ₂ fuel injection quantity feedback control using the output of the sensor 39,
The feedback correction coefficient FAF is calculated. This feedback correction coefficient FAF is a correction coefficient used when calculating the fuel injection amount, and when the exhaust air-fuel ratio is rich, it is gradually updated to a small value to reduce the fuel injection amount, while the exhaust air-fuel ratio is reduced. Is lean, the value is gradually updated to a large value to increase the fuel injection amount.

When the feedback correction coefficient FAF is updated as described above and the fuel injection amount is corrected by the FAF, the fuel supply amount is gradually reduced while the exhaust air-fuel ratio is rich. As a result, the air-fuel ratio eventually reverses from rich to lean. On the other hand, while the fuel supply amount is insufficient and the exhaust air-fuel ratio is lean, the fuel supply amount is gradually increased, and as a result, the air-fuel ratio eventually reverses from lean to rich. As described above, according to the above feedback control, by appropriately increasing / decreasing the feedback correction coefficient FAF, the exhaust air-fuel ratio, that is, the internal combustion engine 3
The air-fuel ratio of the air-fuel mixture supplied to 2 can be maintained near the stoichiometric air-fuel ratio.

[Opening Control of Purge VSV 22 (Purge Control)] As described above, the purge VSV 22 is a control valve that is driven by duty to realize a substantially arbitrary opening. In the system shown in FIG. 1, when the purge VSV 22 opens during operation of the internal combustion engine 32, the purge passage 16
And intake negative pressure via purge VSV22 to canister 1
Can be brought to zero. When the intake negative pressure is introduced into the canister 10, the evaporated fuel adsorbed in the canister 10 is purged into the intake passage 18 together with the air sucked from the atmosphere introduction port 14. Therefore, according to the system shown in FIG. 1, the intake passage 18 can be purged with the amount of evaporated fuel according to the opening degree of the purge VSV 22.

The purge amount of the evaporated fuel becomes larger as the intake negative pressure generated in the intake passage 18 becomes larger and the purge VSV2 becomes larger.
The larger the opening of 2, the larger the amount. On the other hand, the internal combustion engine 32
In the above, the larger the purge amount, the more easily the air-fuel ratio becomes rough and the combustibility is more likely to deteriorate. ECU 40
According to the operating state of the internal combustion engine 32, the opening degree control of the purge VSV 22 is performed more concretely so that unacceptable air-fuel ratio roughening and deterioration of combustibility do not occur and sufficient purging capability is realized. The drive duty (below,
"VSV-Duty") control (purge control) is executed.

[Reduction Correction of Fuel Injection Amount Utilizing Output of Evaporation Density Sensor 28] When the evaporated fuel is purged into the intake passage 18, the internal combustion engine 32 is injected with the purged fuel and the fuel injection valve 36. Fuel is supplied. For this reason, during the purge of the evaporated fuel, a reduction correction is performed to reduce the amount of the purged fuel from the fuel injection amount. In the reduction correction process, first, the evaporation concentration in the gas flowing through the surge tank 26 is detected based on the output of the evaporation concentration sensor 28. And, based on the evaporative concentration,
A reduction ratio to be applied to the fuel injection amount in order to offset the purged amount of fuel is calculated, and the final fuel injection amount is calculated based on the reduction ratio.

According to the reduction correction of the fuel injection amount described above,
The fuel injection amount can be corrected in a feedforward manner based on the evaporation concentration in the gas flowing into the internal combustion engine 32. According to such a method, when the evaporative concentration in the gas changes, the change can be promptly reflected in the fuel injection amount, so that the air-fuel ratio roughness with respect to the change in the evaporative concentration can be sufficiently reduced. it can. Therefore, according to the above-described reduction correction, the purge amount can be quickly increased, and a high purge capacity can be realized.

The output characteristics of the evaporation concentration sensor 28 arranged in the intake passage 18 are not always constant due to variations caused by individual differences of sensors and deterioration of durability of the sensors. The evaporated fuel processing apparatus of the present embodiment can accurately correct the output characteristic of the evaporation concentration sensor 28 by the method described below. The updating method will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows a combination of the fuel vapor treatment apparatus of this embodiment in which the feedback control () for the fuel injection amount, the purge control (), and the fuel injection amount reduction correction () are simultaneously executed. 6 is a timing chart for explaining the operation. Specifically, FIG.
(A) is VSV-D, which is the drive duty of the purge VSV 22.
Shows changes in uty. FIG. 2B shows the evaporation concentration sensor 2
8 shows the output (here, the higher the concentration, the lower the output). Further, FIG. 2C shows a waveform of the fuel injection amount after the reduction correction. Further, FIG. 2D shows the waveform of the feedback correction coefficient FAF.

FIG. 2A shows a state in which the purge of the evaporated fuel is started at time t0 and VSV-Duty is stabilized at a constant value at time t1. When the evaporative fuel purge is started in this way, the output of the evaporation concentration sensor is
As shown in FIG. 2 (B), it starts to change after time t0, and at time t1
Then converges to a constant value β (at this time, the actual evaporation concentration is D0).

Due to the function of the feedback control () and the function of correcting the reduction of the fuel injection amount (), the corrected fuel injection amount starts to decrease after the time t0, as shown in FIG. Converges to a constant value Q0 after. In this example,
Since the reduction correction using the output of the evaporation concentration sensor 28 worked with high precision, the case where the air-fuel ratio was accurately maintained near the stoichiometric air-fuel ratio before and after the start of purging is shown. In this case, as shown in FIG. 2 (D), the feedback correction coefficient FAF maintains a stable inversion period immediately after the start of the purge, as before the start of the purge.

When VSV-Duty has a non-zero value and the feedback correction coefficient FAF repeats inversion in a stable cycle, the correction of the fuel injection amount catches up with the change of the purge amount, and the air-fuel ratio becomes It can be determined that the control is performed in the vicinity of the stoichiometric air-fuel ratio. In this case, the decrease rate of the output of the evaporation concentration sensor 28 (α shown in FIG. 2B)
%) Can be estimated to be in agreement with the corrected fuel injection amount reduction rate (α% shown in FIG. 2C). Then, in this case, it can be estimated that the changed sensor output value β corresponds to the decrease rate α of the fuel injection amount due to the correction. However,
The "decrease rate of output" is the decrease range (Vm
It means the ratio of ax−β). The "reduction rate of the fuel injection amount" means the ratio of the reduction range (QB-Q0) to the basic fuel injection amount QB calculated when the correction is not performed.

In the system of the present embodiment, the fuel injection amount is reduced at a higher rate as the evaporation concentration in the gas flowing through the intake passage 18 is higher due to the feedback control function and the fuel injection amount reduction correction function. It will be.
Therefore, there is a correlation between the evaporation concentration and the reduction rate α of the fuel injection amount, and according to the correlation, the actual evaporation concentration D0 can be estimated based on the reduction rate α of the fuel injection amount. It is possible.

As described above, according to the system of this embodiment, under the condition that VSV-Duty has a value other than 0 and the feedback correction coefficient FAF is stable, on the other hand, the evaporation concentration sensor The output β of 28 can be captured as a value corresponding to the decrease rate α of the fuel injection amount. On the other hand, the actual evaporation concentration D0 can be estimated from the reduction rate α of the fuel injection amount. For this reason,
According to the system of the present embodiment, waiting for the FAF to stabilize,
The output β of the evaporation concentration sensor 28 and the actual evaporation concentration D0
Can be associated with. Hereinafter, the point specified by the sensor output β and the evaporation concentration D0 associated in this way is referred to as a “non-atmospheric point”.

In the system of this embodiment, the atmosphere is circulated in the intake passage 18 by not purging the evaporated fuel, that is, the evaporation concentration in the intake passage 18 can be made zero. Then, by reading the output generated from the evaporation concentration sensor 28 at that time, the evaporation concentration sensor 28 can detect the output Vmax generated when the evaporation concentration is zero. Hereinafter, the point specified by the output Vmax thus detected and the evaporation concentration of zero is referred to as an "atmospheric point".

FIG. 3 shows the output characteristics of the evaporation concentration sensor specified by the atmospheric point and the non-atmospheric point. The output characteristics shown in FIG. 3 are obtained by plotting the atmospheric point 50 and the non-atmospheric point 52 specified by the above-mentioned method on a two-dimensional coordinate with the sensor output as the vertical axis and the evaporation concentration as the horizontal axis, It is created by drawing a line that intersects with 50 and 52. As shown in this figure, the output characteristic of the evaporation concentration sensor 28 is
Once the atmospheric point 50 and at least one non-atmospheric point 52 are determined, they can be identified based on them. Therefore, according to the system of this embodiment, the output characteristic of the evaporation concentration sensor 28 can be corrected easily and accurately.

FIG. 4 is a flow chart of a control routine executed by the ECU 40 in this embodiment for realizing the above functions. In the routine shown in FIG. 4, first, it is determined whether or not the evaporated fuel is being purged (step 100).

As a result, when it is determined that the purge is not executed, the skip counter for counting the number of skips of the feedback correction coefficient FAF is cleared (step 101), and then this routine is immediately ended. To be done.

On the other hand, if it is determined in step 100 that the evaporated fuel is being purged, then it is determined whether the internal combustion engine 32 is in steady operation (step 102). Whether the internal combustion engine 32 is in steady operation is specifically determined by the intake air amount Ga and the engine speed N.
It is determined based on whether E, throttle opening TA, etc. are stable, and whether VSV-Duty is stable.
Further, whether or not those judgment factors are stable is judged based on the comparison between the state at the time of the previous processing cycle and the state at the time of this processing cycle.

In step 102, the internal combustion engine 3
2 is not in steady operation, the intake passage 1
It can be judged that the state and flow rate of the gas flowing through 8 are not stable, and the relationship between the fuel injection amount and the evaporation concentration may deviate from the relationship that should be realized in the steady state. In this case, since the non-atmospheric point cannot be correctly specified, the current routine is immediately ended after the skip counter is cleared in step 102.

On the other hand, if it is determined in step 102 that the internal combustion engine 32 is in steady operation, the state and flow rate of the gas flowing through the intake passage 18 are stable, and the fuel injection amount and the evaporation concentration are It can be judged that the relationship is converging. In this case, next, it is determined whether or not the count value of the skip counter is equal to or greater than the predetermined value n0 (step 104).

The skip counter is a counter that is incremented only when purging is being executed and the internal combustion engine 32 is in steady operation (see steps 100 and 101 above). Therefore, the count value is the predetermined value n0.
In the case of the above, it can be determined that stable purging is being continued for a predetermined period. The predetermined value n0 is a period during which the predetermined period is required for the feedback correction coefficient FAF to stabilize, and more specifically, until the relationship between the fuel injection amount and the evaporation concentration converges to a relationship that should be realized in a steady state. It is set to take the required period. Therefore, when the condition of step 104 is satisfied, it can be determined that the relationship between the fuel injection amount and the evaporation concentration has converged to the relationship that should be realized in the steady state.

In the routine shown in FIG. 4, the above step 1
When it is determined that the condition of 04 is not established, it is determined that the situation for specifying the non-atmospheric point has not yet been formed, and thereafter, this processing cycle is promptly ended.
On the other hand, when it is determined that the condition of step 104 is satisfied, the reduction rate currently applied to the fuel injection amount is detected (step 106).

The ECU 40 calculates the fuel injection amount in another routine. In the process of the calculation process, first,
The amount of air taken into the intake passage 18, that is, the fuel injection amount for realizing the stoichiometric air-fuel ratio with respect to the intake air amount Ga is calculated by betting the basic fuel injection amount. Then, the feedback correction coefficient FAF and the purge correction coefficient for reducing the purge amount of the evaporated fuel are calculated, and the basic fuel injection amount is reduced using these correction factors to calculate the final fuel injection amount. To do. In step 106, the reduction rate applied to the basic fuel injection amount is detected in order to calculate the final fuel injection amount.

In the routine shown in FIG. 4, next, the evaporation concentration is estimated based on the reduction rate (step 10).
8). The ECU 40 stores a map that defines the relationship between the reduction correction ratio applied to the fuel injection amount and the evaporation concentration in the gas flowing through the intake passage 18. This step 10
In 8, the evaporative emission concentration is estimated by referring to the map.

Next, the output of the evaporation concentration sensor 28 at present is detected (step 110).

Then, the non-atmospheric point is specified by the combination of the evaporation concentration estimated in step 108 and the output detected in step 110 (step 112).

In this embodiment, the ECU 40 detects the output of the evaporation concentration sensor 28 with respect to the atmosphere before the purge of the evaporated fuel is started, and the combination of the output and the evaporation concentration of zero is set as the atmospheric point. I remember.
In the routine shown in FIG. 4, the atmospheric point thus stored is read out after the processing of step 112 (step 114).

Then, based on the non-atmospheric point and the atmospheric point specified in this processing cycle, the evaporation concentration sensor 28
Is corrected (step 116).

As described above, according to the routine shown in FIG. 4, when the stable purging is continuously performed, the non-atmospheric point is specified, that is, the evaporation concentration (actually realized) ( It is possible to specify the relationship between the non-zero concentration) and the output of the evaporation concentration sensor 28 with respect to the concentration. Then, based on the non-atmospheric point specified in this way and the atmospheric point specified by another routine, the output characteristic of the evaporation concentration sensor can be corrected accurately. For this reason, according to the fuel vapor processing apparatus of the present embodiment, it is possible to always accurately and accurately based on the output of the evaporation concentration sensor 28, without being affected by variations due to individual differences of sensors, deterioration of durability of the sensors, and the like. Evaporative concentration can be detected.

By the way, in the above-described first embodiment, the exhaust passage 38 is provided in order to realize the feedback control.
The sensor to be placed on the exhaust O ₂ sensor 39, that is,
The sensor emits an output depending on whether the exhaust air-fuel ratio is rich or lean. Since the exhaust O ₂ sensor is inexpensive, such a configuration can reduce the cost of the system.

However, the sensor for realizing the feedback control is not limited to the exhaust O ₂ sensor 39, and an exhaust air-fuel ratio sensor that emits an output indicating the exhaust air-fuel ratio may be used as the sensor. Further, in the first embodiment described above, when the non-atmosphere point is specified, the exhaust air-fuel ratio is feedback-controlled with respect to the theoretical air-fuel ratio, but when the exhaust air-fuel ratio sensor is used, the exhaust air-fuel ratio is The non-atmospheric point may be specified while performing feedback control to an air-fuel ratio different from the stoichiometric air-fuel ratio.

In the first embodiment described above, the exhaust O ₂ sensor 39 is the “exhaust side sensor” described in claim 1, and the reduction rate of the fuel injection amount is the “fuel injection control” described in claim 1. The theoretical air-fuel ratio corresponds to the desired air-fuel ratio according to claim 1. In addition, ECU4
0 executes the purge control described above, and the "purge means" described in claim 1 executes the feedback control of the fuel injection amount described above.
The described "feedback control means" is the same as in step 1 above.
By executing the processing of 08, the "evaporation concentration estimating means" of claim 1 is realized, and by executing the processing of step 112, the "associating means" of claim 1 is realized. .

Further, in the above-described first embodiment,
When the ECU 40 calculates the basic fuel injection amount, the "basic fuel injection amount calculation means" according to claim 2 calculates the corrected fuel injection amount by feedback control and / or correction correction of the fuel injection amount. Thus, the "weight reduction correction means" described in claim 2 is realized.

Further, in the above-described first embodiment,
When the ECU 40 executes the process of step 102, the "engine state detecting means" according to claim 8 executes the process of step 104, and the "stability condition determining means" according to claim 8 and "Estimation permission means" are realized respectively.

Further, in the above described first embodiment,
The ECU 40 executes the process of step 112, whereby the "non-atmospheric point grasping means" according to claim 9 specifies the atmospheric point prior to the process of step 114, and the "non-atmospheric point determining means" according to claim 9 above. The "atmospheric point grasping means" executes the processing of the step 116, whereby the "output characteristic grasping means" of claim 9 is realized.

Embodiment 2. Next, a second embodiment of the present invention will be described with reference to FIGS. Figure 5
FIG. 3 is a diagram for explaining the configuration of the evaporated fuel processing device of the present embodiment. In FIG. 5, the same components as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted or simplified.

In this embodiment, the internal combustion engine 32 is mounted on a hybrid vehicle. In addition to the internal combustion engine 32, the hybrid vehicle is equipped with an electric motor (not shown) as a drive source of the vehicle. The hybrid vehicle can use either or both of the internal combustion engine 32 and the electric motor as a drive source according to a predetermined rule. In addition, the hybrid vehicle may be operated as needed even when the output of the internal combustion engine 32 is not required as the driving force, specifically, when the vehicle is stopped or running by the electric motor (in the EV mode). 32 can be activated.

As shown in FIG. 5, the system of this embodiment includes a state detection unit 42 for detecting the drive state of the hybrid vehicle. The state detection unit 42 indicates that the vehicle is stopped, that the vehicle is in EV mode,
It is possible to detect that the output of the internal combustion engine 32 is required as the driving force. State detection unit 4
The detection result of 2 is supplied to the ECU 40.

In the present embodiment, the ECU 40 is further electrically connected to the rotation speed sensor 44. The rotation speed sensor 44 is a sensor that outputs an output according to the rotation speed NE of the internal combustion engine 32. The ECU 44 can detect the engine speed NE based on the output.

In the system of this embodiment, the fuel injection valve 3
If the fuel injection by 6 is cut and the evaporated fuel is purged, the evaporative concentration of the gas flowing in the intake passage 18 and the evaporative concentration of the gas sucked into the internal combustion engine 32 can be made equal. Therefore, purge VSV2 so that the exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio with the fuel injection cut off.
By controlling the opening degree (VSV-Duty) of 2, the evaporation concentration in the gas flowing through the intake passage 18 can be made the concentration corresponding to the theoretical air-fuel ratio. Then, if the output of the evaporation concentration sensor 28 is detected in that state, the output generated by the evaporation concentration sensor 28 with respect to the stoichiometric air-fuel ratio can be specified.

FIG. 6 shows the output characteristic of the evaporation concentration sensor 28 specified by the system of this embodiment. In FIG. 6, a point indicated by reference numeral 50 is an atmospheric point specified by the same method as in the first embodiment. Further, a point indicated by reference numeral 54 indicates a non-atmosphere point specified by a combination of the theoretical air-fuel ratio and the sensor output with respect to the theoretical air-fuel ratio. According to the system of the present embodiment, it is possible to identify the atmospheric point 50 and the non-atmospheric point 54 shown in FIG. 6 and correct the output characteristic of the evaporation concentration sensor 28 based on them.

In the system of the first embodiment described above, the evaporative emission concentration is estimated based on the reduction rate of the fuel injection amount during execution of the purge. This estimation is based on the premise that the difference between the basic fuel injection amount and the actual fuel injection amount, that is, the reduced amount of the fuel injection amount corresponds to the purged amount of the evaporated fuel. However, the fuel injection amount is subjected to various corrections in addition to the correction for offsetting the purge amount. Therefore, in order to accurately identify the non-atmospheric point by the method of the first embodiment, it is necessary to eliminate the influence of these various corrections.

On the other hand, in the system of the present embodiment, the non-atmosphere point identification processing is performed with the fuel injection cut. In this case, since there is no external factor that hinders the accuracy of specifying the non-atmospheric point, the non-atmospheric point can be specified with extremely high accuracy.

In the system for purging the evaporated fuel into the intake passage 18, if the air-fuel ratio of the gas flowing through the intake passage 18 exceeds the theoretical air-fuel ratio, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 32 is inevitable. It will be rich. Therefore, it is necessary to limit the air-fuel ratio of the gas flowing through the intake passage 18 to the lean side of the stoichiometric air-fuel ratio. Under such a limitation, the output range of the evaporation concentration sensor 28 is a range from the output corresponding to the atmosphere to the output corresponding to the stoichiometric air-fuel ratio.

As shown in FIG. 6, the atmospheric point 50 and the non-atmospheric point 54 specified in this embodiment are points corresponding to both ends of the output range. On the other hand, the non-atmospheric point 52 specified in the device of the first embodiment is the midpoint of the output range of the evaporation concentration sensor 28 (see FIG. 3). When the relationship between the sensor output and the evaporation concentration is specified at two points and the output characteristics are corrected based on those points, the accuracy of the correction can be increased as the two points are separated.
Therefore, according to the system of the present embodiment, it is possible to further improve the accuracy of sensor output correction, as compared with the case of the first embodiment.

For the reason described above, the method used in this embodiment, that is, the method of specifying the non-atmospheric point after making the air-fuel ratio in the intake passage 18 the stoichiometric air-fuel ratio is used in the first embodiment. Compared with the method, it is advantageous in ensuring the calibration accuracy of the evaporation concentration sensor 28.

By the way, in the system of the present embodiment, when the non-atmospheric point is specified, it is required to cut off the fuel injection so that the inside of the intake passage 18 becomes the stoichiometric air-fuel ratio only with the evaporated fuel. When the internal combustion engine 32 is in a state of satisfying this request, it is difficult to freely change the output of the internal combustion engine 32 in response to the driver's request. Therefore, if the non-atmospheric point identification process is executed under the condition where the output of the internal combustion engine 32 is required as the driving force of the vehicle, the drivability of the vehicle is likely to deteriorate during the execution of the process.

Therefore, it is desirable that the correction process of the sensor output by the method used in this embodiment is executed under the condition that the output of the internal combustion engine 32 is not required as the driving force. Therefore, in the system of the present embodiment, the sensor characteristic correction process is executed only when the output of the internal combustion engine 32 is not required as the driving force, such as when the hybrid vehicle is stopped or in the EV mode.

FIG. 7 shows a flow chart of a control routine executed by the ECU 40 in this embodiment in order to realize the above functions. According to the routine shown in FIG. 7, first, based on the detection result of the state detection unit 42, it is determined whether the vehicle is stopped or the vehicle is in the EV mode (step 120).

As a result, when it is determined that none of the above conditions is satisfied, the sensor output correction process is prohibited in order to avoid deterioration of drivability. in this case,
After that, this processing cycle is promptly ended.

On the other hand, if it is determined that the condition of step 120 is satisfied, then a process for operating the internal combustion engine 32 at a constant speed is performed (step 12).
2). In order to identify the non-atmospheric point in the present embodiment, it is necessary to operate the internal combustion engine 32 with the intake passage 18 at the stoichiometric air-fuel ratio. In step 122, the operation of the internal combustion engine 32 is commanded as a preparation. Further, if the fuel injection is cut off because the intake air passage 18 has a ratio air-fuel ratio, the operating state of the internal combustion engine 32 may become unstable. Assuming such a case, the process of this step 122 is executed so that the rotation speed NE of the internal combustion engine 32 becomes a constant rotation speed (for example, 1000 rpm) capable of maintaining stable operation.

In the routine shown in FIG. 7, next, the purge of the evaporated fuel is started while feedback controlling the fuel injection amount based on the output of the exhaust O2 sensor 39 so that the exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio. (Step 124).

Next, while continuing the feedback control of the fuel injection amount, VSV-Duty supplied to the purge VSV 22 is increased (step 126). When VSV-Duty increases, the purged amount of evaporated fuel increases and the air-fuel mixture supplied to the internal combustion engine 32 becomes rich. As a result, the fuel injection amount is reduced by the function of feedback control so as to maintain the exhaust air-fuel ratio at the stoichiometric air-fuel ratio.

Next, it is judged whether or not the purge VSV 22 is fully opened before the fuel injection amount becomes zero. In other words, it is judged whether or not the purge VSV 22 is in the fully open state before the stoichiometric air-fuel ratio is realized only by the evaporated fuel (step 128).

When a large amount of fuel is adsorbed in the canister 10, a large amount of evaporated fuel can be purged, so that the exhaust air-fuel ratio can be maintained at the stoichiometric air-fuel ratio only with the evaporated fuel. However, when the amount of fuel adsorbed on the canister 10 is small, even if the purge VSV 22 is fully opened, it may not be possible to obtain a purge that achieves the stoichiometric air-fuel ratio with only the evaporated fuel.

In the system of this embodiment, the non-atmospheric point cannot be specified unless the stoichiometric air-fuel ratio is realized only by the evaporated fuel. Therefore, in step 128 above,
When it is determined that the purge VSV 22 is fully open, it is determined that the sensor output cannot be updated at this time point, and the process of this time is immediately terminated thereafter.

On the other hand, if it is determined in step 128 that the purge VSV 22 has not yet reached the fully open state, then it is next determined whether the stoichiometric air-fuel ratio is achieved only by the evaporated fuel, that is, the fuel injection amount is already zero. Is determined (step 130).

As a result, when it is determined that the stoichiometric air-fuel ratio is not yet realized only by the evaporated fuel, the processing of the above step 126 is repeated again. On the other hand, when it is determined that the stoichiometric air-fuel ratio has already been realized only with the evaporated fuel, the output emitted from the evaporation concentration sensor 28 at that time is learned as a point (stoichi point) corresponding to the stoichiometric air-fuel ratio. (Step 132).

Thereafter, the ECU 40 corrects the output characteristic of the evaporation concentration sensor 28 in the same manner as in the first embodiment, using the combination of the stoichiometric point and the stoichiometric air-fuel ratio specified as described above as the non-atmospheric point. (See steps 112-116 above in FIG. 4).

As described above, according to the routine shown in FIG. 7, it is possible to specify the non-atmospheric point while realizing the stoichiometric air-fuel ratio with only the evaporated fuel. Further, according to this routine, the process for realizing the stoichiometric air-fuel ratio only with the evaporated fuel is performed only when the hybrid vehicle is stopped or in the EV mode, that is, when the output of the internal combustion engine 32 is not required as the driving force. As long as you can permit. Therefore, according to the system of the present embodiment, the output of the evaporation concentration sensor can be corrected with extremely high accuracy without deteriorating the drivability of the vehicle.

By the way, in the above-described second embodiment, the exhaust passage 38 is provided in order to realize the feedback control.
The exhaust O ₂ sensor 39 is used as the sensor arranged in the above, but the sensor may be an exhaust air-fuel ratio sensor as in the case of the first embodiment. Further, when the exhaust air-fuel ratio sensor is used, the non-atmosphere point may be specified while feedback controlling the exhaust air-fuel ratio to an air-fuel ratio different from the stoichiometric air-fuel ratio.

Further, in the second embodiment described above,
In order to avoid deterioration of the drivability of the vehicle, the method of specifying the non-atmospheric point while realizing the stoichiometric air-fuel ratio only with the evaporated fuel is used in combination with the hybrid vehicle, but the present invention is not limited to this. Not something.
That is, when the deterioration of drivability is not a problem, the method may be applied to an ordinary vehicle.

In the second embodiment described above, the exhaust O ₂ sensor 39 is the “exhaust side sensor” in claim 3, and the VSV-Duty is the “purge control amount” in claim 3. The stoichiometric air-fuel ratio corresponds to the desired air-fuel ratio described in claim 1, respectively. Further, the ECU 40 executes the purge control described above, whereby the "purge means" described in claim 3 executes the processing of steps 124 to 130, and the "stoichiometric state formation means" described in claim 3 is executed. However, the "evaporation concentration estimating means" according to claim 3 is executed by executing the process of step 132.
However, by executing the processing of step 112 shown in FIG. 4, the "associating means" described in claim 3 is realized.

Further, in the second embodiment described above,
In the ECU 40, the state detection unit 42 corresponds to the “driving state detection means” in claim 4, and the processing in step 120 is executed to execute the processing in step 4.
The described "zero injection amount permission means" is realized.

Further, in the second embodiment described above,
The ECU 40 executes the above-mentioned feedback control of the fuel injection amount, and the "feedback control means" described in claim 5 executes the processing of the steps 126 to 130. The "purge control" described in claim 5. The "quantity changing means" is realized.

[0092]

Since the present invention is constructed as described above, it has the following effects. Claim 1
According to the described invention, during execution of the feedback control,
The total amount of fuel supplied to the internal combustion engine is adjusted to an amount that achieves the desired air-fuel ratio. According to the present invention, under such circumstances, the evaporation concentration in the gas flowing through the intake passage can be estimated based on the fuel injection amount. Then, by correlating the evaporation concentration thus estimated and the output of the evaporation concentration sensor, at the non-atmospheric point,
The relationship between the two can be specified.

According to the second aspect of the present invention, the basic fuel injection amount can be reduced by the feedback control so that the purged amount of the evaporated fuel is offset. In this case, there is a correlation between the rate of reduction correction applied to the basic fuel injection amount and the evaporation concentration in the intake passage. Therefore, according to the present invention, it is possible to accurately estimate the evaporation concentration based on the ratio of the above weight reduction correction.

According to the third aspect of the present invention, the purge control amount is feedback-controlled while the fuel injection amount is 0, so that the desired air-fuel ratio can be realized only by the evaporated fuel to be purged. . That is, according to the present invention, by performing the above feedback control, the air-fuel ratio of the gas flowing through the intake passage can be made the desired air-fuel ratio. Then, according to the present invention, in such a situation, the evaporation concentration can be estimated as a value corresponding to the desired air-fuel ratio.

According to the fourth aspect of the invention, in the hybrid vehicle, the feedback control for setting the fuel injection amount to 0 is permitted only under the condition that the output of the internal combustion engine is not required as the driving force of the vehicle. During execution of the feedback control in which the fuel injection amount is 0, the output of the internal combustion engine cannot be changed with good responsiveness. Therefore, if the fuel injection amount is set to 0 under the situation where the output is required as the driving force, the drivability of the vehicle deteriorates. According to the present invention, such deterioration of drivability can be effectively prevented.

According to the fifth aspect of the invention, the fuel injection is performed by gradually increasing the purge amount of the evaporated fuel under the condition that the fuel injection amount is feedback-controlled so that the desired air-fuel ratio is realized. The amount can approach zero. Therefore, according to the present invention, it is possible to smoothly perform the transition from the state where the fuel is injected from the fuel injection valve to the state where the fuel injection amount is set to 0 and the purge control amount is feedback-controlled. It is possible to effectively prevent the combustibility of the internal combustion engine from deteriorating in the process.

According to the sixth aspect of the invention, the feedback control can be performed with the desired air-fuel ratio to be realized as the theoretical air-fuel ratio. Feedback control for achieving the stoichiometric air-fuel ratio is already well established. Therefore, according to the present invention, the relationship at the non-atmospheric point can be accurately specified by using the established technique.

According to the seventh aspect of the invention, since the desired air-fuel ratio to be realized by the feedback control is the stoichiometric air-fuel ratio, the exhaust side sensor can be realized with an inexpensive oxygen concentration sensor. Therefore, according to the present invention, it is possible to reduce the cost of the system.

According to the eighth aspect of the invention, estimation of the evaporation concentration based on the fuel injection amount can be permitted only when the operating state of the internal combustion engine is stable. During the execution of the feedback control, the predetermined correlation between the fuel injection amount and the evaporative emission concentration is recognized only when the both are stable. According to the present invention, it is possible to effectively prevent erroneous estimation by allowing estimation of the evaporation concentration only in such a stable time.

According to the ninth aspect of the present invention, the atmospheric point can be grasped together with the non-atmosphere point, and the output characteristic of the evaporation concentration sensor can be grasped accurately based on these two points.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the configuration of an evaporated fuel processing device according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the device according to the first embodiment.

FIG. 3 is a diagram showing output characteristics of an evaporation concentration sensor specified by the device according to the first embodiment.

FIG. 4 is a flowchart of a control routine executed in the device according to the first embodiment.

FIG. 5 is a diagram for explaining a configuration of an evaporated fuel processing device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the output characteristic of the evaporation concentration sensor specified by the device of the second embodiment.

FIG. 7 is a flowchart of a control routine executed in the device according to the second embodiment.

FIG. 8 is a diagram showing how the output characteristic of the evaporation concentration sensor changes.

[Explanation of symbols]

10 canister 16 purge passage 18 intake passage 22 purge VSV 26 surge tank 28 evaporation concentration sensor 36 fuel injection valve 39 exhaust O ₂ sensor 40 ECU (Electronic Control Unit) 42 state detection unit 44 rotation speed sensor 50 atmospheric point 52; 54 non-atmosphere point

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/14 310 F02D 41/14 310P F02M 25/08 F02M 25/08 J 301 301S (72) Inventor soldier Yoshihiko Michi 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Katsuya Hirai 2-88, Hoei-cho, Toyota-shi, Aichi F-term in Toyota Techno Service Co., Ltd. (reference) 3G044 AA10 BA08 BA22 CA12 DA02 EA12 EA13 EA23 EA43 FA10 FA27 GA02 3G084 BA09 BA13 BA27 DA04 EB12 EC06 FA29 3G093 AA01 BA14 DA11 EA04 EA05 3G301 HA01 HA14 MA01 MA11 NA08 NE06 PB09A PD02Z

Claims (9)

[Claims] 1. An evaporative fuel treatment apparatus for treating evaporative fuel generated in an internal combustion engine, wherein the evaporative fuel has a purging means for purging the evaporative fuel into an intake passage, and an evaporative concentration in a gas flowing through the intake passage has a correlation. Based on the output of the exhaust concentration sensor, which outputs an output, the exhaust side sensor which outputs an output according to the exhaust air-fuel ratio, the fuel injection valve which injects fuel to the internal combustion engine, the exhaust side air-fuel ratio, Feedback control means for performing feedback control for achieving a desired air-fuel ratio, and evaporation concentration estimation means for estimating the evaporation concentration in the gas flowing through the intake passage based on the fuel injection control amount during execution of the feedback control. And a correlating unit that correlates the estimated value of the evaporation concentration with the output of the evaporation concentration sensor. The fuel processing system. 2. A basic fuel injection amount calculation means for calculating a basic fuel injection quantity for realizing the desired air-fuel ratio, wherein the feedback control means is arranged to cancel the purged amount of evaporated fuel. A reduction correction unit that performs a reduction correction on the injection amount, wherein the evaporation concentration estimation unit estimates the evaporation concentration based on a reduction correction ratio applied to the basic fuel injection amount by the reduction correction unit. The evaporated fuel processing device according to claim 1. 3. An evaporative fuel treatment apparatus for treating evaporative fuel generated in an internal combustion engine, which has a purging means for purging the evaporative fuel into an intake passage, and an evaporative concentration in a gas flowing through the intake passage. An evaporation concentration sensor that outputs an output, an exhaust side sensor that outputs an output according to an exhaust air-fuel ratio, a fuel injection valve that injects fuel to an internal combustion engine, and an injection fuel is used based on the output of the exhaust side sensor. And a stoichiometric state forming means for creating a stoichiometric state in which the desired air-fuel ratio is realized only by the evaporated fuel, and an evaporation that estimates the evaporation concentration as a value corresponding to the desired air-fuel ratio when the stoichiometric state is formed. Concentration evaporation means, and an associating means for associating the estimated value of the evaporation concentration with the output of the evaporation concentration sensor. Processing apparatus. 4. The internal combustion engine is mounted on a hybrid vehicle, and a drive state detecting means for detecting a drive state of the hybrid vehicle; and a fuel injection amount only when the output of the internal combustion engine is not required as the drive force of the vehicle. 4. The evaporated fuel processing apparatus according to claim 3, further comprising: a zero injection amount permission unit that permits execution of the feedback control after setting to 0. 5. The exhaust air-fuel ratio is set to a desired air-fuel ratio,
Feedback control means for feedback controlling the fuel injection amount based on the output of the exhaust side sensor is provided, and the stoichiometric state forming means purges the evaporated fuel until the fuel injection amount becomes 0 during execution of the feedback control. 5. The evaporated fuel processing device according to claim 3, further comprising a purge control amount changing means for increasing the amount. 6. The evaporated fuel processing apparatus according to claim 1, wherein the desired air-fuel ratio is a stoichiometric air-fuel ratio. 7. The oxygen concentration sensor according to claim 6, wherein the exhaust side sensor is an oxygen concentration sensor that outputs an output according to whether the exhaust air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio. Evaporative fuel processor. 8. An engine state detecting means for detecting an operating state of the internal combustion engine, wherein the evaporation concentration estimating means determines a stable condition determining means for determining whether or not the operating state of the internal combustion engine is stable over a predetermined period. 8. An estimation permission unit that permits estimation of the evaporation concentration when it is determined that the operating state of the internal combustion engine has been stable over a predetermined period of time. The evaporated fuel processing device according to the item. 9. A non-atmosphere point grasping means for grasping a combination of the output of the evaporation concentration sensor and the estimated value of the evaporation concentration correlated by the associating means, as a non-atmosphere point, and the evaporation concentration sensor to the atmosphere. Atmospheric point grasping means for grasping the combination of the output generated in response to zero and the evaporation concentration of zero as an atmospheric point, and grasping the output characteristic of grasping the output characteristic of the evaporation concentration sensor based on the non-atmospheric point and the atmospheric point. 9. The evaporated fuel processing apparatus according to claim 1, further comprising: