EP1431553B1

EP1431553B1 - Intake air flow control system for internal combustion engine

Info

Publication number: EP1431553B1
Application number: EP20030104340
Authority: EP
Inventors: Makoto Tsuyuguchi; Yoshiaki Hirakata
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2002-12-02
Filing date: 2003-11-24
Publication date: 2013-07-10
Anticipated expiration: 2023-11-24
Also published as: CN1508414A; BR0305302A; BR0305302B1; CN1306158C; JP2004183541A; MXPA03011038A; CA2449147A1; EP1431553A3; ES2430822T3; EP1431553A2; TWI231839B; TW200417683A; CA2449147C

Description

Technical Field to which the Invention Pertains

The present invention relates to an intake air flow control system for an internal combustion engine, particularly to an intake air flow control system for an internal combustion engine with which it is both possible to prevent a rise in cost and to prevent adverse effects on starting characteristics. Such an intake air flow control system is known from DE 3739805 A1 .

Prior Art

As this type of intake air flow control system for an internal combustion engine, there has generally been known one which comprises an auxiliary intake passage bypassing a throttle valve and provided with an intake control valve. According to the intake air flow control system, at the time of idling, the opening of the intake control valve is controlled, to regulate the flow rate of auxiliary intake air flowing through the auxiliary intake passage, whereby the engine speed can be adjusted to a target idling engine speed.
For driving for opening and closing the intake control valve, for example, a stepping motor is used. The valve opening at the time when the stepping motor is adjusted to a reference position is preliminarily stored in a memory of an electronic control unit (ECU), and a command value for the reference position is regulated, whereby an arbitrary valve opening can be obtained.
In the ECU, a target valve opening of the intake control valve (in other words, a target auxiliary intake flow rate) is determined by detecting the engine speed or the like, and a command value to be supplied to the stepping motor is calculated according to the target valve opening. However, due to secular change of the stepping motor or the like causes, the valve opening may drift.
In order to dissolve such a drift, it is necessary to periodically perform a reference position adjustment, namely, an adjustment in which the valve opening on an intake valve control basis recognized by the ECU and the actual valve opening are forcibly made to coincide with each other.
For this purpose, Patent Reference 1 set forth below proposes a method in which immediately after an ignition switch is turned OFF, an electric current is passed to the stepping motor to thereby move the intake control valve to a fully closed position or a fully open position, and this valve position is made to be a reference position for use in valve control.
On the other hand, Patent Reference 2 set forth below proposes a method in which after the engine is stopped, the intake control valve is moved to a half-open position, and this valve position is made to be a reference position for use in valve control.

Patent Reference 1 : Japanese Patent Publication No. Sho 63-42106
Patent Reference 2 : Japanese Patent Laid-open No. Hei 6-307267

Problems to be Solved by the Invention

In each of Patent References 1 and 2, however, it is necessary to operate the stepping motor when the engine is stopped, and, therefore, it is necessary to provide a driving circuit for backing up the power source for operating the ECU, and to provide such functions as a timer circuit for preventing the complete discharge of the battery, i.e., the so-called battery's-up condition. This complicates the circuit configuration and leads to an increase in cost.
In order to obviate this problem, it may be contemplated to perform the reference position adjustment for the intake control valve immediately after the engine is started. In that case, however, if the fully closed position, for example, is made to be a reference position, a bad starting (a long starting time, an engine stall after starting, etc.) would arise from an insufficient intake flow rate. On the other hand, if the fully open position is made to be a reference position, the intake flow rate would become excessively large, causing a disordered operation of the engine.
The present invention has been made in consideration of the foregoing. Accordingly, it is an object of the present invention to provide an intake air flow control system for an internal combustion engine with which it is possible both to prevent a rise in cost and to prevent adverse effects on starting characteristics of the internal combustion engine.

Means for Solving the Problems

According to the present invention, the means of claim 1 have been adopted in order to solve the above problems.
According to the intake air flow control system for an internal combustion engine as set forth in claim 1, when the first re-reading condition is established, it is determined that the current idling engine speed has approached the target idling engine speed. In addition, when the second re-reading condition is established, it is determined that the auxiliary intake air flow control valve has undergone a positional drift and needs a correction. When both the first re-reading condition and the second re-reading condition are established, the valve opening corresponding to the reference intake flow rate is adopted as correct, rather than the valve opening corresponding to the calculated intake flow rate. Further, the reference position of the stepping motor is re-read when it is determined that the idling operation is currently performed.
According to the intake valve control system for an internal combustion engine as set forth in claim 2, the reference position of the stepping motor is re-read when the current idling engine speed has approached the target idling engine speed.
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An embodiment of the intake air flow control system for an internal combustion engine according to the present invention will be described below referring to the drawings, but it should naturally be noted here that the embodiment is not construed as limitative of the invention. While the case of applying the present invention to a motorcycle will be described by way of example in this embodiment, the invention is naturally applicable also to other vehicles.

Brief Description of the Drawings

Fig. 1 is a side view showing one embodiment of a motorcycle comprising an intake air flow control system for an internal combustion engine according to the present invention.
Fig. 2 is an enlarged sectional view of part A of Fig. 1, showing an essential part of the motorcycle.
Fig. 3 is an illustration of general constitution of the intake air flow control system in the motorcycle.
Fig. 4 is an illustration of operations of the intake air flow control system.
Fig. 5 shows tables stored in an ECU in the intake air flow control system, in which (a) shows water temperature tables showing an air flow rate for obtaining a predetermined engine speed at a certain water temperature, and (b) shows reference mass flow rate tables showing the correlation between the opening of a bypass valve and the flow rate of auxiliary intake air flowing through the bypass valve at the opening, wherein the solid line indicates the valve characteristic at shipping from factory, and the broken line indicates the valve characteristic as shifted in parallel in relation to that at the shipping from factory.
Fig. 6 is an illustration of the flow of control by the intake air flow control system.
Fig. 7 is a detailed illustration of parts of the flow of control by the intake air flow control system, in which (a) to (c) respectively show subroutines of steps S1 to S3 of Fig. 6.
Fig. 8 is a detailed illustration of parts of the flow of control by the intake air flow control system, in which (a) to (c) respectively show subroutines of steps S4 to S6 of Fig. 6.

Detailed description of the invention

As shown in Figs. 1 and 2, the motorcycle 1 in this embodiment has a motor scooter type structure in which a power unit 4 is disposed directly under a luggage box 3 which is elongate in the front-rear direction and for which a tandem seat type seat 2 is used also as a lid. A power unit 4 comprises an engine (internal combustion engine) 5 having a cylinder block 6 largely inclined toward the front side, and a non-stage transmission 8 having a rearwardly extending transmission case 10 integrally connected in relation to one side of a crankcase 9 of the engine 5. A rear wheel (drive wheel) 11 is shaft-supported on a rear end portion of the transmission case 10.
As shown in Fig. 2, a cylinder head 7 joined to the front end of the cylinder block 6 is provided with an intake port 7a having its upstream end opening toward the rear side of the vehicle body, and a fuel injection valve 7b for injecting a fuel toward the downstream end of the intake port 7a. Further, an intake air flow control system 21 for controlling the flow rate of intake air supplied to the engine 5 is connected to the upstream end of the intake port 7a. As shown in Fig. 3, the intake air flow control system 21 comprises a throttle valve 31 having a main intake passage 32a communicated to the intake port 7a, and an idle valve 41 comprising an auxiliary intake passage 42a bypassing the throttle valve 31.
As shown in Figs. 2 and 3, the throttle valve 31 comprises a tubular throttle body 32 provided therein with the main intake passage 32a, a throttle valve element 33 provided inside the throttle body 32 so as to open and close the main intake passage 32a, and a drive force transmission mechanism (not shown) for transmitting a drive force to the throttle valve element 33. An air cleaner 23 is connected to the upstream end of the throttle body 32 through an intake duct 22. On the other hand, the downstream end of the throttle body 32 is connected to the cylinder head 7 through a connecting tube 24. In addition, a side wall of the throttle body 32 is provided with a bypass inlet 32b communicated to the main intake passage 32a on the upstream side of the throttle valve element 33, and a bypass outlet 32c communicated with the main intake passage 32a on the downstream side of the throttle valve element 33.
The idle valve 41 comprises a casing 46 integrally fixed to the throttle body 32, the auxiliary intake passage 42 formed inside the casing 46 and bypassing the throttle valve element 33 by communicating the bypass inlet 32b and the bypass outlet 32c to each other in the exterior of the throttle body 32, a bypass valve (auxiliary intake air flow control valve) 43 for controlling the flow rate of auxiliary intake air flowing through the auxiliary intake passage 42, a stepping motor 44 for driving the bypass valve 43, a power transmission portion 45 for converting a rotational drive force of the stepping motor 44 into an advancing and retracting drive force for the bypass valve 43, and an electronic control unit (not shown; hereinafter referred to as ECU) for controlling the stepping motor 44.
The casing 46 is provided with an auxiliary intake air inlet 46a communicated to the bypass inlet 32b, an auxiliary intake air outlet 46b communicated to the bypass outlet 32c, and a valve hole 46c which communicates the auxiliary intake air inlet 46a and the auxiliary intake air outlet 46b to each other and into which the bypass valve 43 is inserted.
The bypass valve 43 is roughly hollow cylindrical in shape, and comprises a first valve hole 43a formed at the tip end thereof, and a second valve hole 43b and a third valve hole 43c formed in a side wall thereof and communicated with the first valve hole 43a. When the bypass valve 43 is advanced and retracted inside the valve hole 46c, the auxiliary intake flow rate is controlled according to the largeness of the sectional area of a communication passage formed by overlapping of the second valve hole 43b and the third valve hole 43c with the auxiliary intake air outlet 46b. Therefore, the auxiliary intake flow rate supplied to the engine 5 can be controlled according to the advanced/retracted position of the bypass valve 43 inside the valve hole 46c.
To be more specific, as shown in the left lower illustration of Fig. 4, when the engine 5 is in a starting condition, all the opening areas of the second valve hole 43b and the third valve hole 43c overlap with the opening area of the auxiliary intake air outlet 46b so as to maximize the flow rate of intake air to the engine 5. This makes it possible to maximize the opening of the idle valve 41 (IACV opening) and to raise the engine speed (ENG speed), as shown in the graph above the illustration.
During a warm-up operation after the starting, as shown in the central lower illustration of Fig. 4, the third valve hole 43c and a part of the second valve hole 43b are communicated with the auxiliary intake air outlet 46b. This makes it possible to adjust the opening of the idle valve 41 (IACV opening) to a valve opening at the time of the warm-up operation, as shown in the graph above the illustration.
Further, during idling after the warm-up operation, as shown in the right lower illustration of Fig. 4, the second valve hole 43b is completely closed and only the third valve hole 43c is communicated with the auxiliary intake air outlet 46b. This makes it possible to adjust the opening of the idle valve 41 (IACV opening) to a valve opening at the time of idling, as shown in the graph above the illustration.
As shown in Fig. 3, the stepping motor 44 is fixed inside the casing 41 coaxially with the valve hole 46c, and a rotary shaft 44a thereof is formed with a male screw 44a1. Incidentally, symbol 47 denotes a seal member, which prevents intake air in the auxiliary intake passage 42 from leaking from the inside of the valve hole 46c toward the outside.
The power transmission portion 45 comprises a drive member 45a provided with a female screw hole 45a1 screwe-engaged with the rotary shaft 44a, and a spring 45b for fixing the drive member 45a to the bypass valve 43. An Oldham's coupling 45c is interposed between the drive member 45a and the bypass valve 43, so that these members can be relatively displaced in the radial direction with the axes thereof as a center. The spring 45b is a biasing member for biasing the bypass valve 43 against a flange portion 45a2 formed in the drive member 45a, so that the bypass valve 43 is chatterlessly fixed onto the drive member 45a.
The above-mentioned ECU is provided for controlling the number of steps of the stepping motor 44, and stores therein an atmospheric pressure table for obtaining an atmospheric pressure correction factor, water temperature tables (see Fig. 5(a); provided respectively for each of a starting operation mode and a running operation mode) for determining an auxiliary intake flow rate based on the temperature of cooling water for cooling the engine 5, a reference mass flow rate table (see the thick line in Fig. 5(b); the "IACV opening" on the axis of abscissas indicates the valve opening) designating the reference characteristic between the valve opening of the bypass valve 43 and the auxiliary intake flow rate (in other words, the characteristic between the step position and the mass flow rate when the stepping motor 44 is adjusted to the reference position), and a volume flow rate table indicating the step position of the stepping motor 44 which is required for obtaining a certain volume flow rate.
The ECU can be supplied with an atmospheric pressure value measured by an atmospheric pressure sensor (not shown) and the water temperature of cooling water.
The flow of control by the above-described intake air flow control system 21 (hereinafter referred to as IACV) will be described referring to Figs. 6 to 8. Fig. 6 shows an outline of the control flow, and Figs. 7 and 8 show subroutines attendant on the control flow shown in Fig. 6. In the following description, the idling engine speed will be referred to as INE, and the target engine speed will be referred to as target NE. Of the idling engine speeds, the idling engine speed to be obtained now will be referred to as this-time INE, the idling engine speed obtained one step earlier than this time will be referred to as last-time INE, the current idling engine speed obtained by actual measurement will be referred to as current NE, and the idling engine speed actually measured one step earlier than this time will be referred to as last-time NE.

(1) Flow of Step S1

When control of IACV is started by turning the ignition ON, an atmospheric pressure correction factor is first obtained in step S1. Specifically, as shown in the subroutine of Fig. 7(a), in step S1-1, the atmospheric pressure table recorded in the ECU is referred to, and an atmospheric pressure correction factor corresponding to the atmospheric pressure value measured by the atmospheric pressure sensor is calculated. After the atmospheric pressure correction factor is thus obtained, if the current engine operation is at starting or in running, step S2 in Fig. 6 is entered. On the other hand, if the current engine operation is at idling, step S3 in Fig. 6 is entered.

(2) Flow of Step S2

When step S2 is entered, the mass flow rate of intake air at starting or in running is obtained. Specifically, as shown in Fig. 7(b), if the current engine operation is at starting, step S2-1 is entered, in which the water temperature table for use at starting, of the water temperature tables stored in the ECU, is referred to and a starting mass flow rate corresponding the water temperature measured by the water temperature sensor is calculated. On the other hand, if the current engine operation is in running, step S2-2 is entered, in which the water temperature table for use in running, of the water temperature tables in the ECU, is referred to and a running mass flow rate corresponding to the water temperature measured by the water temperature sensor is calculated. After the mass flow rate of intake air at starting or in running is obtained, step S3 in Fig. 6 is skipped and step S4 in Fig. 6 is entered.

(3) Flow of Step S3

When step S3 is entered, a mass flow rate required for idling is obtained. Specifically, as shown in Fig. 7(c), in step S3-1, an error is calculated as the absolute value of the difference between a current NE measured and a target NE. In the subsequent step S3-2, a difference ΔNE is calculated as the absolute value of the difference between the current NE and a last-time NE. Further, in the subsequent step S3-3, a PID mass flow rate is calculated based on the error and the difference ΔNE obtained respectively in steps S3-1 and S3-2. Furthermore, in the subsequent step S3-4, the PID mass flow rate calculated in step S3-3 is added to a mass flow rate corresponding to a last-time INE, whereby an INE mass flow rate corresponding to a this-time INE is calculated. After the current INE mass flow rate is thus obtained, step S4 in Fig. 6 is entered.

(4) Flow of Step S4

In step S4, a step position of the motor corresponding to the mass flow rate at starting or in running obtained in step S2 or to the mass flow rate at idling (INE mass flow rate) obtained in step S3 is obtained. Specifically, as shown in Fig. 8(a), first, it is determined in step S4-1 whether the current engine operation is at starting or not. If the current engine operation is at starting, step S4-2 is entered, in which the mass flow rate at starting is subjected to atmospheric pressure correction by use of the atmospheric pressure correction factor obtained in step S1-1, whereby a volume flow rate at starting is calculated. In the subsequent step S4-3, the volume flow rate table recorded in the ECU is referred to, and a target step position corresponding to the volume flow rate at starting obtained in step S4-2 is calculated. After the target step position is thus obtained, step S5 in Fig. 6 is skipped and step S6 in Fig. 6 is entered.
On the other hand, if it is determined in step S4-1 that the current engine operation is not at starting, step S4-4 is entered to determine whether the current engine operation is in running or not. Then, if the current engine running is determined as in running, step S4-5 is entered; on the other hand, if the current engine operation is determined as not in running, step S4-7 is entered.
When step S4-5 is entered, the mass flow rate in running is subjected to atmospheric pressure correction by use of the atmospheric pressure correction factor obtained in step S1-1, whereby a volume flow rate in running is calculated. In the subsequent step S4-6, the volume flow rate table recorded in the ECU is referred to, and a target step position corresponding to the volume flow rate in running obtained in step S4-5 is calculated. After the target step position is thus obtained, step S5 in Fig. 6 is skipped and step S6 in Fig. 6 is entered.
On the other hand, when it is determined in step S4-4 that the current engine operation is not in running, the current engine operation is determined as in idling and step S4-7 is entered. In step S4-7, the idling mass flow rate (INE mass flow rate) is subjected to atmospheric pressure correction by use of the atmospheric pressure correction factor obtained in step S1-1, whereby an idling volume flow rate (INE volume flow rate) is calculated. In the subsequent step S4-8, the volume flow rate table recorded in the ECU is referred to, and a target step position corresponding to the idling volume flow rate obtained in step S4-7 is calculated. After the target step position is thus obtained, step S5 in Fig. 6 is entered.

(5) Flow of Step S5

In step S5, when both of the following first and second re-reading conditions are satisfied, re-reading of the reference position of the stepping motor 44 is performed. In other words, when the current idling engine speed has approached the target idling engine speed, re-reading of the reference position of the stepping motor 44 is performed. (When it is determined by the ECU, which is means for determining whether or not the current engine operation is in idling, that the current engine operation is in idling, re-reading of the reference position of the stepping motor 44 is performed.)
To be more specific, as shown in Fig. 8(b), first, if it is determined in step S5-1 that the error (the absolute value of the difference between the target idling engine speed and the current idling engine speed detected by a pulse sensor) obtained in step S3-1 is smaller than a predetermined threshold (first threshold), a first re-reading condition is regarded as established and step S5-2 is entered. If the first re-reading condition is not established, re-reading is not performed but step S6 in Fig. 6 is entered.
When step S5-2 is entered, the reference mass flow rate table in the ECU is subjected to atmospheric pressure correction by use of the atmospheric pressure correction factor obtained in step S1-1, whereby a reference volume flow rate is calculated. In the subsequent step S5-3, the volume flow rate table in the ECU is referred to, and a target step position a corresponding to the reference volume flow rate obtained in step S5-2 is calculated. In the subsequent step S5-3a, a target step position b corresponding to an INE volume flow rate is calculated from the volume flow rate table.
In the subsequent step S5-4, the absolute value of the difference between the target step position a obtained in step S5-3 and the target step position b obtained in step S5-3a is calculated, and when this absolute value is determined as greater than a predetermined threshold (second threshold), step S5-5 is entered, whereas when the absolute value is determined as smaller than the predetermined threshold (second threshold), step S6 in Fig. 6 is entered. That is, in step S5-4, in regard of the auxiliary intake flow rate for obtaining the target idling engine speed, when the absolute value of the difference between the calculated intake flow rate obtained by calculation and the reference intake flow rate obtained based on the reference mass flow rate table (reference characteristic) is greater than the second threshold value, the second re-reading condition is regarded as established and step S6 is entered.
When step S5-5 is entered, the target step position obtained in step S5-3a is re-read as the target step position obtained in step S5-3.
Specifically, the target step position b (the valve opening corresponding to the calculated intake flow rate) obtained by calculation is re-read as the reference step position a (the valve opening corresponding to the reference intake flow rate on a reference characteristic basis) obtained based on the reference mass flow rate table. To be more specific, as shown in Fig. 5(b), when the IACV opening is shifted in parallel from a valve characteristic at shipping from factory indicated by the solid line to a valve characteristic indicated by the broken line due to secular change or the like, in regard of the IACV opening (step position) for obtaining the same air flow rate, the IACV opening obtained from the valve characteristic at shipping from factory is adopted in place of the IACV opening obtained by calculation. For example, in the example shown, while the IACV opening obtained by calculation is ST2, this IACV opening is replaced with ST1, before being read. This makes it possible to correct a valve characteristic drift, if any, on a software basis. After the re-reading of the target step position is thus performed, step S6 in Fig. 6 is entered.

(6) Flow of Step S6

In step S6, the stepping motor 44 is driven to the step position according to the target step position obtained. Specifically, as shown in Fig. 8(c), in step S6-1, the target step position obtained in any one of steps S4-3, S4-6, and S4-8 or the target step value re-read in step S5-5 is referred to, and the stepping motor 44 is rotated accordingly, whereby a target valve opening is obtained (namely, a target auxiliary intake flow rate is secured).
As has been described above, according to the intake air flow control system 21 in this embodiment, when it is determined that the current idling engine speed has approached the target idling engine speed and that the bypass valve 43 has come to have a positional drift and needs a reference position adjustment, the re-reading is performed in which the valve opening corresponding to the reference intake flow rate is adopted as correct, rather than the valve opening corresponding to the calculated intake flow rate.
According to this configuration, since the reference position adjustment is not conducted when the engine 5 is stopped, it is unnecessary to provide a drive circuit for backing up the operating power source when the engine 5 is stopped and it is unnecessary to provide a timer circuit or the like for preventing a battery's-up condition. This makes it possible to prevent a complication of circuit configuration and, hence, a rise in cost. In addition, since it is unnecessary to forcibly bring the bypass valve 43 to a fully closed condition or a fully open condition at the time of the reference position adjustment, it is possible to prevent a bad starting or an abrupt vehicle motion.
Therefore, it is possible both to prevent a rise in cost and to prevent adverse effects on the starting characteristics.

Effects of the Invention

According to the intake air flow control system for an internal combustion engine as set forth in claim 1 of the present invention, at the time of performing a reference position adjustment of the auxiliary intake air flow control valve, when the first re-reading condition where the absolute value of the difference between the target idling engine speed and the current idling engine speed is smaller than the first threshold and the second re-reading condition where the absolute value of the difference between the calculated intake flow rate and the reference intake flow rate is greater than the second threshold are established, the re-reading step is performed in which the valve opening position corresponding to the reference intake flow rate on a reference characteristic basis is used in place of the valve opening corresponding to the calculated intake flow rate.
According to this configuration, since the reference position adjustment is not conducted when the internal combustion engine is stopped, it is unnecessary to provide a drive circuit for backing up the operating power source when the internal combustion engine is stopped, and it is unnecessary to provide a timer circuit or the like for preventing a battery's-up condition. This makes it possible to prevent a complication of circuit configuration and, hence, a rise in cost. In addition, since it is unnecessary to forcibly bring the auxiliary intake air flow control valve to a fully closed condition or a fully open condition at the time of performing the reference position adjustment, it is possible also to prevent a bad starting.
Thus, according to the present invention, it is possible both to prevent a rise in cost and to prevent adverse effects on the starting characteristics.

Description of Reference Numerals

32a: main intake passage
33: throttle valve element
42: auxiliary intake passage
43: bypass valve (auxiliary air flow control valve)
44: stepping motor

Claims

An intake valve control system for an internal combustion engine (5), comprising an auxiliary intake passage (42a) provided in an intake system (21) of said internal combustion engine (5) so as to bypass a throttle valve (31), and an auxiliary intake air flow control valve (43) connected to a stepping motor (44) so as to open and close said auxiliary intake passage (42a), characterized in that
said intake valve control system comprises a means for determining whether or not an idling operation is currently performed, and a means for performing re-reading of a reference position of said stepping motor (44) when it is determined that the idling operation is currently performed, and in that
a reference characteristic between the valve opening of said auxiliary intake air flow control valve (43) and said auxiliary intake flow rate being preliminarily stored,
at the time of idling,
a first re-reading condition where the absolute value of the difference between a target idling engine speed and a current idling engine speed is smaller than a first threshold, and
a second re-reading condition where, in regard of said auxiliary intake flow rate for obtaining said target idling engine speed, the absolute value of the difference between a calculated intake flow rate obtained by calculation and a reference intake flow rate obtained based on said reference characteristic is greater than a second threshold value,
are obtained, and
when both of said first re-reading condition and said second re-reading condition are established, a re-reading step is conducted in which a valve opening corresponding to said reference intake flow rate based on said reference characteristic is used in place of a valve opening corresponding to said calculated intake flow rate.
An intake valve control system according to claim 1, wherein
a reference position of said stepping motor (44) is re-read when a current idling engine speed has approached a target idling engine speed.