JPH10331720A - Intake device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an intake manifold made of resin from heat deterioration through reflux of high temperature exhaust gas. SOLUTION: An auxiliary air passage bypassing a throttle valve is confluent to a position right before a position where an exhaust reflux flow passage is confluent to an intake manifold. When exhaust reflux is effected at S11, the temperature of reflux exhaust gas is detected in a position situated downstream from the confluence of the auxiliary air passage at S12, and a detecting temperature forms the temperature Te of a detecting reflux exhaust gas, which is compared with a target temperature range of approximate 120-150 deg.C at S14. When the temperature Te of reflux exhaust gas is higher than 150 deg.C being a heat resisting limit, the opening θ of an auxiliary air amount control valve located in an auxiliary air passage is corrected for increase at S16. Further, when the temperature Te of reflux exhaust gas is below 120 deg.C at which adhesion of deposit is eminent, the opening θ is corrected for decrease at S15. This constitution controls an amount of fresh air mixed in reflux exhaust gas through the auxiliary passage so that a target temperature range of approximate 120-150 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake device for an internal combustion engine, and more particularly, to a technique for controlling the temperature of exhaust gas recirculated in an intake device for recirculating exhaust gas.

[0002]

2. Description of the Related Art Conventionally, a part of exhaust gas is recirculated to an intake system in order to reduce the generation amount of nitrogen oxide NOx.
An internal combustion engine provided with a GR system (exhaust gas recirculation system) is known. Also, Japanese Patent Laid-Open No. 6-81
Japanese Patent No. 719 discloses a configuration in which an auxiliary intake passage is provided separately from the main intake passage, and an exhaust recirculation passage is joined to the auxiliary intake passage so as to be opened to a branch portion of the intake manifold.

Further, Japanese Utility Model Laid-Open No. 1-146565 discloses a structure for preventing the thermal deformation of a synthetic resin intake manifold by introducing fresh air into an exhaust gas recirculation passage.

[0004]

In the structure disclosed in Japanese Patent Application Laid-Open No. Hei 6-81719, the auxiliary intake passage is closed when exhaust gas recirculation is performed. If it rises, the temperature of the recirculation exhaust gas when introducing the intake manifold becomes high,
In an engine using an intake manifold made of resin, there is a possibility of causing thermal deterioration.

On the other hand, if fresh air is fed into the exhaust gas recirculation passage as disclosed in Japanese Utility Model Laid-Open No. 1-146565, the temperature of the recirculated exhaust gas can be lowered, and the heat of the resin intake manifold can be reduced. Deterioration can be prevented. However, since the above-described conventional apparatus is not configured to control the amount of fresh air, the temperature of the recirculated exhaust gas becomes too low due to the introduction of fresh air at low load when the exhaust gas temperature is low, and unburned exhaust gas There is a possibility that the components may accumulate in the exhaust gas recirculation passage as a devoid.

The present invention has been made in view of the above problems, and maintains the temperature of exhaust gas recirculated to an intake system at an appropriate temperature that can prevent thermal deterioration of a resin intake manifold and avoid generation of deposits. It is an object of the present invention to provide a suction device capable of performing the above-described operations.

[0007]

The invention according to claim 1 is configured as shown in FIG. In FIG.
The exhaust gas recirculation passage is a passage for recirculating a part of the exhaust gas to the intake system, and the auxiliary air passage is a passage for introducing fresh air to the exhaust gas recirculation passage. A control valve for controlling the amount of fresh air introduced into the exhaust gas recirculation passage is provided in the auxiliary air passage.

[0008] On the other hand, the recirculated exhaust gas temperature detecting means detects the temperature of the recirculated exhaust gas downstream of a portion where fresh air is introduced via the auxiliary air passage. The fresh air introduction amount control means controls the opening of the control valve based on the temperature of the recirculated exhaust gas detected by the recirculated exhaust gas temperature detecting means. According to this configuration, the amount of fresh air controlled by the control valve is introduced into the exhaust gas recirculation passage, and the temperature of the recirculated exhaust gas is reduced by mixing the fresh air. Here, the temperature of the recirculated exhaust gas is detected downstream of the portion where the fresh air is introduced, and the opening degree of the control valve is controlled based on the detected temperature. The control prevents the temperature of the recirculated exhaust gas introduced into the intake system from being lowered below an appropriate temperature due to excessive introduction of fresh air, and the intake system due to insufficient introduction of fresh air. To prevent the temperature of the recirculated exhaust gas introduced into the device from rising above an appropriate temperature.

[0009] In the second aspect of the present invention, the exhaust gas recirculation passage is a resin intake manifold portion for recirculating exhaust gas, and the fresh air introduction amount control means detects the recirculated exhaust gas temperature by the recirculated exhaust gas temperature detecting means. The opening degree of the control valve is controlled so as to maintain the temperature of the recirculated exhaust gas at about 120 to 150 ° C. According to this configuration, the temperature of the exhaust gas recirculated to the resin intake manifold is approximately 120 to 150.
The degree of opening of the control valve is controlled so as to be maintained at ° C., and the amount of fresh air introduced into the exhaust gas recirculation passage is controlled. That is, when the temperature of the exhaust gas that is actually recirculated is higher than the temperature range of approximately 120 to 150 ° C., the opening of the control valve (the amount of fresh air introduced) is increased to avoid thermal deterioration of the intake manifold. When the temperature of the exhaust gas that is actually recirculated is lower than the temperature range of approximately 120 to 150 ° C., the opening of the control valve (the amount of fresh air introduced) is reduced in order to avoid generation of dehodget.

According to a third aspect of the present invention, the recirculated exhaust gas temperature detecting means detects the temperature of the recirculated exhaust gas from a temperature sensor provided in an exhaust gas recirculation passage downstream of a portion where fresh air is introduced via the auxiliary air passage. The configuration is such that the temperature of the recirculated exhaust gas is detected based on the signal. According to this configuration, the temperature sensor for detecting the temperature of the recirculation exhaust gas is installed in the recirculation exhaust passage downstream of the portion where the auxiliary air passage merges, and the recirculation exhaust gas after the fresh air is mixed by the temperature sensor. Is detected directly.

According to a fourth aspect of the present invention, the recirculated exhaust gas temperature detecting means estimates and calculates an exhaust gas temperature, the recirculated exhaust gas flow rate estimating means estimates and calculates a recirculated exhaust gas flow rate, and the auxiliary air flow. And a fresh air flow rate estimating means for estimating and calculating the flow rate of fresh air introduced into the exhaust gas recirculation passage through the passage, based on the estimated and calculated exhaust gas temperature, recirculated exhaust gas flow rate, and fresh air flow rate. Thus, the configuration is such that the temperature of the recirculated exhaust gas is estimated and calculated downstream of the portion where fresh air is introduced via the auxiliary air passage.

With this configuration, the exhaust gas temperature, the recirculated exhaust gas flow rate, and the fresh air flow rate introduced into the exhaust recirculation passage via the auxiliary air passage are estimated and calculated based on the operating conditions of the engine, the opening of the control valve, and the like. You. Then, the temperature of the recirculated exhaust gas after being mixed with the introduced fresh air is estimated based on the estimated exhaust gas temperature, the recirculated exhaust gas flow rate, and the fresh air flow rate. According to a fifth aspect of the present invention, a volume chamber is provided immediately before the exhaust gas recirculation passage merges with the intake system, and the auxiliary air passage merges with the volume chamber.

According to this structure, the recirculated exhaust gas is maintained at a high temperature until it reaches the volume chamber, and the recirculated exhaust gas and fresh air introduced through the auxiliary air passage immediately before being introduced into the intake system. They are mixed and returned to the intake system (intake manifold).

[0014]

According to the first aspect of the present invention, the amount of fresh air mixed with the recirculated exhaust gas can be controlled so that the temperature of the recirculated exhaust gas after mixing becomes an appropriate temperature. There is an effect that it is possible to prevent the occurrence of thermal deterioration of the intake system due to the recirculation of the high-temperature exhaust gas, and to prevent the occurrence of a deposit due to a decrease in the temperature of the recirculated exhaust gas.

According to the second aspect of the present invention, the exhaust gas having a temperature exceeding an appropriate temperature (about 120 to 150 ° C.) is recirculated to the resin intake manifold, and the resin intake manifold may be thermally degraded. While avoiding this, there is an effect that the temperature of the recirculated exhaust gas becomes lower than the appropriate temperature (about 120 to 150 ° C.) and the deposits can be prevented from accumulating in the intake manifold.

According to the third aspect of the present invention, since the temperature of the exhaust gas recirculated to the intake system is directly detected by the temperature sensor, the temperature of the recirculated exhaust gas can be controlled to an appropriate temperature with high accuracy. According to the fourth aspect of the present invention, the temperature of the exhaust gas recirculated to the intake system can be estimated based on the operating conditions and the like, so that the amount of fresh air mixed with the recirculated exhaust gas can be controlled with a simple configuration. There is an effect that can be.

According to the fifth aspect of the present invention, the fresh air for controlling the temperature can be satisfactorily mixed with the exhaust gas recirculated to the intake system so that the exhaust gas can be recirculated at a uniform temperature. There is.

[0018]

Embodiments of the present invention will be described below. FIG. 2 is a diagram showing a system configuration of the internal combustion engine according to the first embodiment.
After the flow rate of the intake air is adjusted by the throttle valve 3, the intake air is distributed and supplied to each cylinder by the intake manifold 4. In the present embodiment, a resin-made intake manifold 4 is used.

The combustion exhaust gas of the engine 2 is discharged through an exhaust manifold 5 and an exhaust passage 6. Here, an exhaust gas recirculation passage 7 for recirculating a part of the exhaust gas from the exhaust manifold 5 near the inlet of the intake manifold 4 is provided, and an exhaust gas recirculation control valve 8 interposed in the exhaust gas recirculation passage 7 is provided. The exhaust gas recirculation amount is controlled.

An auxiliary air passage 9 which bypasses the throttle valve 3 and joins the exhaust gas recirculation passage 7 is provided. The auxiliary air passage 9 has an auxiliary air amount for controlling an auxiliary air amount. A control valve 10 is interposed. The auxiliary air passage 9 merges with the exhaust gas recirculation passage 7 near the intake manifold 4, and the exhaust air recirculation passage 7 between a position where the auxiliary air passage 9 merges and a position where the auxiliary air passage 9 merges has: A temperature sensor 11 (recirculation exhaust gas temperature detection means) for detecting the temperature of the recirculation exhaust gas is provided.

The control unit 12 having a built-in microcomputer controls the auxiliary air amount control valve 10 based on the temperature of the recirculated exhaust gas detected by the temperature sensor 11.
Control the opening degree. The flowchart of FIG. 3 shows how the opening degree of the auxiliary air amount control valve 10 is controlled by the control unit 12 as the fresh air introduction amount control means. Step 11 (shown as S11 in the figure. Same)
Then, it is determined whether or not the operation is within an operation range in which the exhaust gas recirculation is executed.

In step 12, the temperature Te (° C.) of the recirculated exhaust gas detected by the temperature sensor 11 is read, and in the next step 13, the current opening degree θ of the auxiliary air amount control valve 10 is read. In step 14, the current temperature Te of the recirculated exhaust gas read in step 12 is compared with a preset target temperature range (120 to 150 ° C.).

If it is determined in step 14 that 120.ltoreq.Te.ltoreq.150, the routine is terminated without changing the opening .theta. Of the auxiliary air amount control valve 10. On the other hand, when it is determined that 120> Te, the step
Proceeding to 15, the target opening of the auxiliary air amount control valve 10 is corrected to be smaller than the current opening θ by a predetermined opening (for example, 10 deg).

If it is determined that Te> 150, the routine proceeds to step 16, where the target opening of the auxiliary air amount control valve 10 is corrected to be larger than the current opening θ by a predetermined opening (for example, 10 deg). . The temperature of the exhaust gas recirculated to the intake system is shown in FIG.
As shown in (1), the temperature fluctuates depending on the engine load. On the high load side, the temperature may exceed 150 ° C., which is the heat resistance limit of the intake manifold 4 made of resin. Therefore, fresh air having a low temperature is mixed with the recirculated exhaust gas before being introduced into the intake manifold 4 made of resin, and the exhaust gas having a lowered temperature is introduced into the intake manifold 4. When the temperature exceeds a certain 150 ° C., the opening degree θ of the auxiliary air amount control valve 10 is gradually increased to increase the amount of fresh air to be mixed, and to lower the temperature to below the heat resistant limit.

On the other hand, since the exhaust gas temperature is low on the low load side,
Further, when the temperature is lowered by mixing fresh air, the temperature becomes lower than 120 ° C., at which the adhesion of deposits becomes remarkable.
Therefore, when the temperature of the recirculated exhaust gas is lower than 120 ° C., the opening degree of the auxiliary air amount control valve 10 is reduced to reduce the amount of fresh air mixed with the recirculated exhaust gas so that a temperature of 120 ° C. or more is obtained.

In this way, the temperature of the exhaust gas recirculated to the intake manifold 4 is adjusted to a suitable temperature of about 120 to 150 ° C.
(See FIG. 5), thereby preventing the generation of the deposit from being promoted while preventing the thermal degradation of the intake manifold 4 made of resin.
If the position where the exhaust gas recirculation passage 7 joins is a position close to the combustion chamber, the pressure of the recirculation exhaust gas introduction position rises due to the return of the combustion gas when the intake valve is opened, and the recirculation exhaust gas flows into the auxiliary air passage 9. However, if the recirculation exhaust gas is introduced near the inlet of the intake manifold 4 as in the present embodiment, the pressure at the introduction portion is always set to a negative pressure. It can be maintained and the backflow of the recirculated exhaust gas can be prevented.

Further, the exhaust gas recirculation passage 7 having no problem with heat resistance.
It is preferable to keep the exhaust gas temperature in the exhaust gas recirculation passage 7 high in order to minimize the deposition of deposits in the exhaust gas. Therefore, in the present embodiment, the auxiliary air passage 9 is joined at a position near the exhaust gas recirculation passage 7 where the exhaust gas recirculation passage 7 merges with the intake manifold 4, so that the high-temperature recirculated exhaust gas flows through the intake manifold 4.
It is made to cool just before it is introduced into

As a method of lowering the temperature of the recirculation exhaust gas, there is a method of cooling the recirculation exhaust water with the cooling water of the engine. However, in the case of the water cooling system, the structure becomes complicated and the cost is increased. If a method of introducing fresh air into the exhaust gas recirculation passage as in the above embodiment is used, the structure is relatively simple, and a rise in cost can be suppressed. Conventionally, an auxiliary air passage has been provided by bypassing a throttle valve, and the amount of air supplied to the engine via the auxiliary air passage has been controlled by an auxiliary air amount control valve to control idling operation stably. Therefore, the auxiliary air passage is merged with the exhaust gas recirculation passage, and the auxiliary air amount control valve is controlled only under a low load condition such as idling as shown in FIG. Is controlled also in a high load region in which exhaust gas recirculation is performed, and the temperature of the recirculated exhaust gas is controlled by mixing fresh air supplied from the auxiliary air passage with the recirculated exhaust gas.

FIG. 7 is a diagram showing the system configuration of an internal combustion engine according to the second embodiment. Instead of using the temperature sensor 11 in FIG. 2 to directly detect the temperature of the recirculated exhaust gas,
The configuration is such that the temperature of the recirculated exhaust gas is estimated and calculated by using an intake air amount sensor (air flow meter) 15 and a crank angle sensor 16 used for normal engine control. In the present embodiment, the opening of the auxiliary air amount control valve 10 is controlled as shown in the flowchart of FIG.

First, at step 21, it is determined whether or not it is in the exhaust gas recirculation region. If it is in the exhaust gas recirculation region, the routine proceeds to steps 22 to 24, where the exhaust gas temperature Th, the recirculated exhaust gas flow Qe, and the A new air flow rate Qs (auxiliary air flow rate) supplied to the exhaust gas recirculation passage 7 via the air passage is calculated. The exhaust gas temperature Th, the recirculated exhaust gas flow Qe, and the fresh air flow Q
The calculation of s estimates these parameters from operating conditions and the like, and will be described later in detail.

In step 25, the estimated exhaust gas temperature Th, the recirculated exhaust gas flow Qe, and the fresh air flow Qs
, The temperature Te of the recirculated exhaust gas after being mixed with fresh air introduced through the auxiliary air passage 9 is calculated. The calculation of the recirculated exhaust gas temperature Te is based on the exhaust gas temperature Th and the recirculated exhaust gas flow rate Q.
e, which estimates the recirculated exhaust gas temperature Te based on the fresh air flow rate Qs, and is performed using the following equation.

Qe (Th−Te) = Qs (Te−Tair) Here, Tair is the temperature of the intake air, and may be detected by an intake air temperature sensor or may be a fixed value (for example, 25 ° C.). In step 26, the current opening degree θ of the auxiliary air amount control valve 10 is read. In step 27, the target temperature range (130
140 ° C.) and the estimated recirculation exhaust gas temperature Te. In the present embodiment, since the exhaust gas temperature immediately before being introduced into the intake manifold 4 is not directly detected by the temperature sensor but is estimated based on the exhaust gas temperature Th, the recirculated exhaust gas flow Qe, and the fresh air flow Qs, the estimation error In view of this, the target temperature range is narrowed as compared with the first embodiment (120 to 150 ° C.).

If it is determined in step 27 that 130 ≦ Te ≦ 140, the routine is terminated without changing the opening θ of the auxiliary air amount control valve 10. On the other hand, when it is determined that 130> Te, the step
Proceeding to 28, the target opening of the auxiliary air amount control valve 10 is corrected to be smaller than the current opening θ by a predetermined opening (for example, 10 deg).

When it is determined that Te> 150, the routine proceeds to step 29, where the target opening of the auxiliary air amount control valve 10 is corrected to be larger than the current opening θ by a predetermined opening (for example, 10 deg). . The flowchart of FIG.
This shows how the exhaust gas temperature Th is calculated in 22 (exhaust gas temperature estimating means). In step 31, the engine speed Ne calculated based on the detection signal from the crank angle sensor 16 is read. In step 32, Intake air amount sensor
The engine intake air flow rate Qa detected at 15 is read.

Then, in step 33, as shown in FIG. 10, a map in which the exhaust gas temperature Th is stored in advance using the engine speed Ne and the intake air flow rate Qa as parameters is referred to.
An exhaust temperature Th corresponding to the current engine speed Ne and the intake air flow rate Qa is searched. The flowchart of FIG. 11 shows how the recirculated exhaust gas flow rate Qe is calculated in the step 23 (recirculated exhaust gas flow rate estimating means). In the step 41, the flow rate is calculated based on the detection signal from the crank angle sensor 16. The engine speed Ne is read
At 42, the intake air flow rate Qa of the engine detected by the intake air amount sensor 15 is read.

In step 43, as shown in FIG. 12, the current engine rotational speed Ne and the intake air flow rate Qe are referred to a map in which the recirculation exhaust flow rate Qe is stored using the engine rotational speed Ne and the intake air flow rate Qa as parameters. A recirculation exhaust flow rate Qe corresponding to the air flow rate Qa is searched. Further, the flowchart of FIG. 13 shows how the new air flow rate Qs (auxiliary air flow rate) is calculated in step 24 (new air flow rate estimation means). In step 51, the flow rate is detected by the intake air amount sensor 15. The engine intake air flow rate Qa
At 52, the current opening degree θ of the auxiliary air amount control valve 10 is read.

In step 53, as shown in FIG. 14, the current intake air flow rate Qa and the opening degree are referred to by referring to a map in which the new air flow rate Qs is stored in advance using the intake air flow rate Qa and the opening degree θ as parameters. A new air flow rate Qs corresponding to θ is searched. According to the second embodiment, the temperature of the exhaust gas recirculated to the intake manifold 4 can be detected using the detection results of various sensors generally used for controlling the engine without installing a temperature sensor. Can be simplified. However, if the temperature sensor is installed as in the first embodiment, the temperature of the recirculated exhaust gas can be accurately detected, and the opening degree of the auxiliary air amount control valve 10 can be more appropriately determined. Can control.

FIG. 15 is a view showing the third embodiment, and is a partially enlarged perspective view showing a portion where the exhaust gas recirculation passage 7 joins the intake manifold 4. In the configuration shown in FIG. 15, a volume chamber 7a is provided immediately before the exhaust gas recirculation passage 7 merges with the intake manifold 4, and the auxiliary air passage 9 is merged with the volume chamber 7a.

In the exhaust gas recirculation passage 7 having no problem in heat resistance, it is desired to keep the exhaust gas temperature as high as possible to suppress the generation of deposits. , Intake manifold 4
It is preferable that the position be close to
There is a possibility that the recirculated exhaust gas and fresh air may be introduced into the intake manifold 4 in a state where they are not sufficiently mixed.

FIG. 16 shows the temperature distribution of exhaust gas in the diameter direction of the exhaust gas near the outlet of the exhaust gas recirculation passage 7 in which the recirculated exhaust gas is introduced into the intake manifold 4.
In the configuration in which the volume chamber is not provided, the mixing of the exhaust gas and the fresh air is insufficient, so that even if the average temperature is appropriate, the average temperature may locally exceed the target temperature range. In contrast,
If the volume chamber 7a is provided, the mixing of the exhaust and fresh air is promoted in the volume chamber 7a, so that the temperature distribution becomes substantially uniform as shown in FIG. The intake manifold 4 can be prevented from being thermally deteriorated by being introduced.

In the configuration in which the volume chamber 7a is provided, the temperature of the recirculated exhaust gas may be directly detected by a temperature sensor, or the temperature of the recirculated exhaust gas may be estimated from operating conditions without a temperature sensor. It is good also as a structure to make it.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an intake device according to the first embodiment.

FIG. 2 is a system configuration diagram of the internal combustion engine according to the first embodiment.

FIG. 3 is a flowchart showing a state of fresh air introduction amount control in the first embodiment.

FIG. 4 shows the change in the recirculation exhaust gas temperature and the thermal deterioration due to the engine load,
FIG. 3 is a diagram showing a correlation with the occurrence of a deposit.

FIG. 5 is a diagram for explaining effects of the first embodiment.

FIG. 6 is a diagram showing a correlation between an exhaust gas recirculation (EGR) region and a conventional auxiliary air control region.

FIG. 7 is a system configuration diagram of an internal combustion engine according to a second embodiment.

FIG. 8 is a flowchart showing a state of fresh air introduction amount control in the second embodiment.

FIG. 9 is a flowchart illustrating a state of estimating an exhaust gas temperature according to the second embodiment.

FIG. 10 is a diagram showing a state of an exhaust gas temperature map according to an intake air flow rate Qa and an engine rotation speed Ne.

FIG. 11 is a flowchart illustrating a state of estimating a recirculated exhaust gas flow rate according to the second embodiment.

FIG. 12 is a diagram illustrating a state of a recirculation exhaust flow rate map according to an intake air flow rate Qa and an engine rotation speed Ne.

FIG. 13 is a flowchart illustrating a state of estimating a fresh air flow rate according to the second embodiment.

FIG. 14 shows the intake air flow rate Qa and the opening degree θ of the auxiliary air amount control valve.
The figure which shows the fresh air flow map according to (a).

FIG. 15 is an enlarged perspective view of a junction between an exhaust gas recirculation passage and an intake manifold according to a third embodiment.

FIG. 16 is a diagram for explaining effects of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main intake passage 2 Internal combustion engine 3 Throttle valve 4 Intake manifold 5 Exhaust manifold 6 Exhaust passage 7 Exhaust recirculation passage 8 Exhaust recirculation control valve 9 Auxiliary air passage 10 Auxiliary air amount control valve 11 Temperature sensor 12 Control unit 15 Intake air amount sensor 16 Crank angle sensor

Claims (5)

[Claims] An exhaust gas recirculation passage for recirculating a part of exhaust gas to an intake system; an auxiliary air passage for introducing fresh air into the exhaust gas recirculation passage; A control valve for controlling the amount of fresh air to be supplied; a recirculation exhaust gas temperature detecting means for detecting a temperature of the recirculation exhaust gas downstream of a portion where the fresh air is introduced via the auxiliary air passage; An intake device for an internal combustion engine, comprising: fresh air introduction amount control means for controlling the opening of the control valve based on the temperature of the recirculated exhaust gas detected by the detection means. 2. An exhaust system in which the exhaust gas recirculation passage recirculates exhaust gas is a resin intake manifold portion, and the fresh air introduction amount control means detects the temperature of the recirculated exhaust gas detected by the recirculated exhaust gas temperature detection means. 2. The intake system for an internal combustion engine according to claim 1, wherein the opening degree of the control valve is controlled so as to maintain the temperature at approximately 120 to 150.degree. 3. The recirculated exhaust gas temperature detecting means detects recirculated exhaust gas based on a detection signal from a temperature sensor provided in an exhaust gas recirculation passage downstream of a portion where fresh air is introduced via the auxiliary air passage. 3. The intake device for an internal combustion engine according to claim 1, wherein a temperature of the internal combustion engine is detected. 4. The exhaust gas temperature estimating means for estimating and calculating the temperature of exhaust gas, the recirculating exhaust gas temperature estimating means for estimating and calculating the flow rate of recirculated exhaust gas, and the exhaust gas through the auxiliary air passage. And a fresh air flow rate estimating means for estimating and calculating a flow rate of fresh air introduced into the recirculation passage. The auxiliary air flow is estimated based on the estimated and calculated exhaust gas temperature, recirculated exhaust gas flow rate, and fresh air flow rate. 3. The intake device for an internal combustion engine according to claim 1, wherein a temperature of the recirculated exhaust gas downstream of a portion where fresh air is introduced via the air passage is estimated and calculated. 5. A volume chamber is provided immediately before the exhaust gas recirculation passage merges with an intake system, and the auxiliary air passage is merged with the volume chamber.
An intake device for an internal combustion engine according to any one of the preceding claims.