System and method for controlling an engine idling speed for an internal combustion engine

• US 4,875,446 A
• Filed: 03/31/1988
• Issued: 10/24/1989
• Est. Priority Date: 04/09/1987
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Nemoto, Toshikazu, Nakazawa, Shinsuke
• Primary Examiner(s): Nelli, R. A.
• Application Number:
  US07/177,913
• Time in Patent Office: 572 Days
• Field of Search: 123/339, 123/340, 123/349, 123/378, 123/402, 123/403, 123/587, 123/588
• US Class Current: 123/41.31
• CPC Class Codes: F02D 2011/102 at least one throttle being moved only by an electric actuator
• CPC Class Codes: F02D 2400/18 Packaging of the electronic circuit in a casing
• CPC Class Codes: F02D 31/005 by controlling a throttle by-pass
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: F02D 41/3005 Details not otherwise provided for
• CPC Class Codes: F02M 3/075 the valve altering the fuel conduit cross-section being a slidable valve

Abstract

An improved system and method for controlling an engine idling speed for an internal combustion engine are disclosed in which an electromagnetic valve for controlling fluid flow quantity passing through a bypass passage of an engine throttle valve is provided, a water jaket for circulating an engine cooling water is provided so as to surround a coil portion of the electromagnetic valve. The change characteristic of the fluid flow quantity for the electromagnetic valve is varied according to the engine cooling water temperature, and both an optimum target idling speed and feedback control coefficients in a control variable of an opening angle of the electromagnetic valve, i.e., a voltage duty ratio applied to the electromagnetic valve are varied according to the engine cooling water temperature.

Claims

1. A system for controlling an engine idling speed for an internal combustion engine, comprising:

(a) first means for detecting an engine operating condition, the first means including a first sensor for detecting an engine speed and a second sensor for detecting an engine coolant temperature;

(b) second means for determining whether the engine falls in an engine idling condition on the basis of the engine operating condition;

(c) third means for controlling a fluid flow quantity passing through a bypass passage installed in an intake passage of the engine when the engine falls in the engine idling state on the basis of an input signal having a controlled duty ratio, the duty ratio having a feedback control proportional coefficient and a feedback control integration coefficient and being varied according to the engine coolant temperature, so that the engine speed detected by the sensor coincides with a target engine speed determined according to the engine operating condition;

the third means having an electromagnetic valve installed in the bypass passage for opening and closing the bypass according to the input signal having the duty ratio determined according to the engine operating condition; and

(d) fourth means for varying the fluid flow quantity characteristic of the third means according to the engine operating condition, the fourth means having fifth means for heating a coil portion of the electromagnetic valve to a temperature which coincides with the engine coolant temperature so that the fluid flow quantity characteristic of the electromagnetic valve is varied according to the engine cooling water temperature representing the engine operating condition.

2. A system for controlling an engine idling speed for an internal combustion engine, comprising:

(a) first means for detecting an engine operating condition, the first means including a sensor for detecting an engine idling speed;

(b) second means for determining whether the engine falls in an engine idling condition on the basis of the engine operating condition;

(c) third means for setting a target engine idling speed according to the engine operating condition;

(d) fourth means for controlling the engine speed according to the engine operating condition so that the engine speed coincides with the target engine idling speed when the second means determines that the engine falls in the engine idling condition, a control variable of the fourth means including a proportional control coefficient and integration control coefficient, at least one of both control coefficients being varied according to the engine operating condition said fourth means further including valve means for controlling airflow quantity passed through a bypass passage installed so as to enable intake air to pass therethrough toward internal engine cylinders during the engine idling on the basis of an input signal having a duty ratio, the duty ratio determining an opening angle of the valve means and being derived on the basis of the control variable, and fifth means for varying a change characteristic in the airflow quantity characteristic of the valve means according to the engine operating condition, said, valve means including an electromagnetic valve installed in the bypass passage and normally closing the bypass passage for opening and closing the bypass passage according to the input signal having the duty ratio;

said fifth means comprising a water jacket installed so as to enclose a coil portion of the electromagnetic valve, the water jacket passing an engine cooling water so as to heat the coil portion of the electromagnetic valve so that the change characteristic of the airflow quantity of the electromagnetic valve is varied according to the engine cooling water temperature; and

wherein a valve portion of the electromagnetic valve is formed with a gradually inclined portion and steeply inclined portion, and a wire forming the coil portion thereof has a positive temperature resistance coefficient so that the maximum airflow quantity of the electromagnetic valve is reduced to a required airflow quantity after the engine has warmed up.

3. A system as set forth in claim 2, wherein the fourth means includes valve means for controlling airflow quantity passed through a bypass passage installed so as to enable intake air to pass therethrough toward internal engine cylinders during the engine idling on the basis of an input signal having a duty ratio, the duty ratio determining an opening angle of the valve means and being derived on the basis of the control variable, and fifth means for varying a change characteristic in the airflow quantity characteristic of the valve means according to the engine operating condition.

4. A system as set forth in claim 3, wherein the valve means includes an electromagnetic valve installed in the bypass passage and normally closing the bypass passage for opening and closing the bypass passage according to the input signal having the duty ratio and fifth means comprises a water jacket installed so as to enclose a coil portion of the electromagnetic valve, the water jacket passing an engine cooling water so as to heat the coil portion of the electromagnetic valve so that the change characteristic of the airflow quantity of the electromagnetic valve is varied according to the engine cooling water temperature.

5. A system as set forth in claim 4, wherein a valve portion of the electromagnetic valve is formed with a gradually inclined portion and steeply inclined portion and a wire forming the coil portion thereof has a positive temperature resistance coefficient so that the maximum airflow quantity of the electromagnetic valve is reduced to a required airflow quantity after the engine has warmed up.

6. A system as set forth in claim 2, wherein the fourth means varies both of the feedback control proportional and integration coefficients according to the engine operating condition.

7. A system as set forth in claim 6, wherein the fourth means determines the feedback control proportional coefficient according to a first difference between the target engine idling speed and actual engine speed and a first variable determined according to the engine operating condition in the way expressed as follows:

(Δ

D_P =Δ

Nxα

).

8. A system as set forth in claim 7, wherein the fourth means determines the feedback control coefficient according to a second difference between the present first difference and previous first difference and according to a second variable determined according to the engine operating condition in the way expressed as follows:

(Δ

D_I =(Δ

N-Δ

No)xβ

).

9. A system as set forth in claim 7, wherein the duty ratio of the input signal is determined in the following equation:

D=D_o +Δ

D, wherein D_o is the previous duty ratio and Δ

D=Δ

D_P +Δ

D_I.

10. A system as set forth in claim 9, wherein the engine operating condition is an engine cooling water temperature.

11. A system as set forth in claim 10, wherein the first and second variables are increased as the engine cooling water temperature is increased.

12. A system as set forth in claim 11, wherein the increase of the first variable is large as compared with the increase of the second variable.

13. A system as set forth in claim 5, wherein the characteristic of the airflow quantity is such that as the engine cooling water temperature increases the airflow quantity is decreased.

14. A method for controlling an engine idling speed for an internal combustion engine, comprising the steps of:

(a) detecting an engine operating condition including the engine idling speed by detecting engine speed and engine coolant temperature;

(b) determining whether the engine falls in the engine idling condition on the basis of the engine operating condition detected in the step (a);

(c) setting a target engine idling speed according to the engine operating condition; and

(d) controlling the engine idling speed according to the detected engine operating condition by controlling a fluid flow quantity passing through a bypass passage installed in an intake passage of the engine when the engine falls in the engine idling state on the basis of an input signal having a controlled duty ratio, the duty ratio having a feedback control proportional coefficient and a feedback control integration coefficient and being varied according to the engine coolant temperature, so that the engine speed detected coincides with a target engine speed determined according to the engine operating condition; and

opening and closing the bypass passage according to the input signal having the duty ratio determined according to the engine operating condition;

varying the fluid flow quantity characteristic according to the engine operating condition, so that the fluid flow quantity characteristic is varied according to the engine cooling water temperature so as to represent the engine operating condition;

so that when the engine falls in the engine operating condition, the engine idling speed coincides with the target engine idling speed, a control variable thereof including a proportional control coefficient and integration control coefficient, both of which are varied according to the engine operating condition.

15. A method as set forth in claim 14, wherein the step (d) includes the step of controlling a change characteristic of electromagnetic valve means provided for controlling the airflow quantity according to the engine operating condition, the electromagnetic valve means installed so as to enable a bypass passage of an engine throttle valve to pass the controlled airflow to engine cylinders during the engine idling.

16. A system for controlling an engine idling speed for an internal combustion engine, comprising:

(a) a bypass passage bypassing an engine driving force adjusting mechanism of the engine;

(b) an electromagnetic valve installed in the bypass passage for controlling an intake air quantity flowing through the bypass passage;

(c) heating means for heating a coil portion of the electromagnetic valve to a temperature which accords with a temperature of an engine coolant temperature so that the airflow quantity passing through the bypass passage and electromagnetic valve is varied so as to correspond to the engine coolant temperature;

(d) first control means for detecting an engine operating condition including an engine speed and engine coolant temperature and controlling in a feedback mode a controlled variable of the electromagnetic valve so that an engine idling speed coincides with a target engine idling speed determined according to the engine operating condition; and

(e) second control means for varying the target engine idling speed so as to correspond to the engine coolant temperature and varying coefficients of the feedback control to correct a controlled variable of an opening angle of the electromagnetic valve.