GB2221254A

GB2221254A - I.C. engine ingnition timing control system

Info

Publication number: GB2221254A
Application number: GB8916662A
Authority: GB
Inventors: Kunihiro Abe
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1988-07-25
Filing date: 1989-07-21
Publication date: 1990-01-31
Also published as: JP2682651B2; GB8916662D0; DE3924575A1; JPH0237170A

Description

IGNITION TIMING CONTROL SYSTEM FOR AN ENGINE 2 2 2 1 r25 4 The present

invention relates to an ignition timing control system for an engine in dependency on an engine temperature and a timing for shifting the ignition timing.

For ignition timing control systems of this kind, there has been provided an angular control system to detect projections or slits provided on a crank rotor for measuring an ignition timing as disclosed in Japanese Patent Application Laid-Open No. 61-96181. In addition, there is also a timing control system to detect the elapsed time between the projections or slits provided on is the crank rotor at predetermined intervals for measuring the ianition timing as disclosed in Japanese Patent LaidOoen No. 60-47877.

Meanwhile, as the engine speed is unstable when cranking, many systems adopt to set the ignition timing at BTDC (Before Top Dead Center) 101 at a time of cranking, and then to advance an ignition angle after starting the engine so as to shift to an ordinary ignition timing. A timing for shifting to such ordinary ignition timing control is uniformly switched to predetermined position in dependency on the engine speed, when a start-er switch is switched from an ON to an OFF state.

1 is In the ordinary operating state where the engine speed is stable, the time control system is more advantageous than the timing angle control system because of fast computing speed and simplified structure, etc. However, for an unstable initial or start-up time period immediately after starting, it is difficult to precisely detect a change of the engine speed.

Namely, as shown in FIG. 1 (a fixed ignition timing period when cranking the engine), where projections la and lb are formed at an outer periphery of a crank rotor 1, e.g., at positions of BTDC 100 and BTDC 1000 when starting the engine, an ignition signal is output to an ignition drive means (not shown) to spark an ignition plug when a crank pulse produced in response to detection of the projection la is output.

On the other hand, as shown in FIG. 2 (ignition timing control immediately after starting), when the starter switch is turned OFF after complete firing, or when the engine speed rises to a predetermined value, the ignition timing control is switched to ordinary timing control. First, an angular velocity is calculated by a time period a between the time when the projection la is detected and the time when the projection lb is detected. Then, the angular velocity is converted to an ignition angle in dependency on the operating state to an ignition time in accordance with the calculated angular velocity. An ignition timing is therefore measured with reference 2 to the time when the projection lb is detected as a reference time point. When the timing reaches a predetermined ignition time (BTDC 201 in FIG. 2), an ignition signal is output.

However, the burning characteristics generally vary in dependency on a combustion engine temperature.For example, when an engine temperature is high at the starting, combustion is relatively stable. Accordingly, to shift to a relatively fast ignition timing from the fixed side to a timing control side which permits a L smooth start-up characteristic. On the other hand, where the engine temperature is low such as in a cold starting, combustlon is unstable even after complete firing.

Particularly, in the case of very low engine speed immediately after starting the engine, the interval of the time period a is prolonged. When the engine speed for this time period varies to a great degree, an actual ignition timing angle may be excessively advanced to a position far from BTDC 300, even if an ignition timing is set at BTDC 200 as shown in FIG. 2.

As a result, when the ignition timing is suddenly advanced from the fixed ignition timing when starting the engine In a cold state, the engine speed does not increase smoothly Consequently, engine stalling may occur, making it difficult to obtain a satisfactory starting performance.

3 In addition, when the switching timing of such an ignition timing is set for the state where the engine is cold, an ignition timing control at the time of the slow engine speed in the case where the engine temperature is relatively high such as in restarting an engine at high temperature is not suitably conducted, resulting in the problem that a satisfactory starting performance cannot be obtained.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an ignition timing control system for an engine, having a timing control system, wherein the system is capable of switching the ignition timing from fixed ignition timing to ordinary ignition timing control in dependency on an engine temperature.

An ignition timing control system for an engine according to the present invention comprises ignition timing setting means for setting the ignition timing from an ignition timing map using an engine load and an engine speed as parameters, respectively, and ignition timing switching means for setting the engine speed to switch the ignition timing between a fixed ignition timing set in advance and the ignition timing set at the ignition timing setting means in dependency on the engine temperature. Accordingly, the engine speed for shifting from the fixed ignition timing to an ordinary ignition 4 timing control is adjustably set at an optimum value. Thus, the starting performance is satisfactorily improved.

FIGS. 1 and 2 are f ront views of crank rotors of a prior art;

FIG. 3 is a block diagram of an ignition timing control unit according to the present invention; FIG. 4 is a schematic view of an engine control system according to the present invention; FIG. 5 is a front view of a crank rotor according to the present invention; FIG. 6 is a diagram showing an engine speed to switch ignition timing in dependency on a coolant temperature; and FIG. 7 is a flowchart showing an ignition timing control procedure immediately after starting.

A preferred embodiment according to the present invention will be described with reference to the attached drawings.

In FIG. 4, reference numeral 11 denotes an engine with four horizontallyopposed cylinders in this embodiment. An intake manifold 13 and an exhaust manifold 14 are connected to an intake port 12a and an exhaust port. 12b formed in a cylinder head 12 of the engine 11, respectively. Furthermore, an ignition plug exposed to a combustion chamber lla is secured on the cylinder head 12.

A throttle chamber 17 communicates with the intake manifold 13 on an upstream side thereof through an air chamber 16. The upstream side of the throttle chamber 17 communicates with an air cleaner 19 through an intake pipe 18.

Furthermore, an intake air flow sensor (a hot wire type air flow meter in the figure) 20 is inserted into the intake pipe 18 on a downstream side thereof toward the air cleaner 19. A coolant temperature sensor 21 is mounted on a coolant passage (not shown) constituting a riser formed in the intake manifold 13.

Furthermore, a crank rotor 22 is fixed on a crank is shaf t llb of the engine 11, and a crank angle sensor 23 such as an electromagnetic pick-up is provided on an outer periphery of the crank rotor 22.

As shown in FIG. 5, projections 22a as reference point for calculating angular velocity, and projections 22b indicating reference crank angles of respective cylinders (No. 1, No. 2, No. 3 and No. 4) are arranged at diametrically opposed positions on the outer periphery of the crank rotor 22.

For example, in this figure, setting is made such that a set angle 01 from the projections 22a and a set angle e2 from the projections 22b are equal to BTDC 100 and BTDC 1000, respectively.

6 is The crank angle sensor 23 takes out an alternating current (AC) voltage produced by cutting the magnetic Lflux when respective projections 22a and 22b of the crank rotor 22 pass through the head of the crank angle sensor 23 to output a rotational angle signal Ne (engine speed) and an angular velocity and a reference crank angle signal G for detecting a reference crank angle for each cylinder.

A circuit of the control system will now be described.

As best shown in FIG. 4, an ignition timing control unit designated by reference numeral 24 includes a central processing unit (CPU) 25, a read only memory (ROM) 26, a random access memory (RAM) 27, and an input/output (I/0) interface 28. These components are interconnected via a bus line 29. Moreover, operating state parameter detection means 30 (FIG. 3) including the above-mentioned sensors 20, 21 and 23 is connected to an input port of the I/0 interface 28. Furthermore, a drive circuit 31 is connected to an output port of the I/0 interface 28. The ignition plug 15 is connected to the drive circuit 31 through a distributor 32 and an ignition coil 33.

In a ROM 26, fixed data such as control programs and an ignition timing map MPIG are stored. Af ter output signals from respective sensors of the operating state parameter sensor means 30 are subjected to data 7 processing, they are stored in RAM 27. In addition, the CPU 25 computes an ignition timing by using various data stored in a RAM 27 in accordance with a control program stored in a ROM 26.

The control system functions as follows. As shown in FIG. 3, the ignition timing 24 comprises crank pulse discrimination means velocity calculation means 35, engine speed means 36, intake air flow calculation means temperature calculation means 38, engine load means 39, ignition timing correction quantity control unit 34, angular calculation 37, coolant calculation calculation means 40, ignition timing setting means 41, ignition timing map MPIG, engine speed setting means 44, ignition timing calculation means 45, timer means 46, and ignition drive means 47.

The crank pulse discrimination means 34 discriminates that an output signal from the crank angle sensor 23 is a G signal produced in response to detection of the projection 22b of the crank rotor 22 or an Ne signal produced in response to detection of the projection 22a by a signal produced in response to detection of a projection of the cam rotor rotating synchronously with a cam shaft (not shown).

Namely, the cam rotor rotating synchronously with the cam shaft makes onehalf of a revolution during one r evolution of the crank rotor 22. By detecting projections formed equiangularly every 90 degrees on the 8 outer periphery of the cam rotor, it is possible to predict what signal is output from the crank angle sensor 23 after detection of the projection.

The angular velocity calculation means 35 calculates a time Te from the time when the rotational angle signa.1 Ne discriminated by the crank pulse discrimination means 34 is detected to the time when the next reference crank angle signal G is detected. Then, the calculation means 35 calculates an angular velocity w of the crank shaft llb from angular data between projections 22a and 22b of the crank rotor 22 stored in advance in the ROM 26.

The engine speed calculation means 36 calculates an engine speed N (r.p.m. ) from the angular velocity w calculated by the angular velocity calculation means 35.

is The intake air flow calculation means 37 calculates a volume of an intake air, i.e., an intake air quantity Q passing through the intake pipe 18 in dependency on an output signal from the intake air flow sensor 20.

The coolant temperature calculation means 38 calculates a coolant temperature Tw from an output signal from the coolant temperature sensor 21.

The engine load calculation means 39 calculates a fundamental fuel injection quantity Tp (Tp = 1 x Q/1, K... constant) from the number of engine revolutions N calculated at the engine speed calculator means 36 and the intake air auantity Q calculated at the intake air 9 quantity calculation means 37. The fundamental fuel injection quantity Tp corresponds to an engine load.

The ignition timing correction calculation means 40 calculates an ignition timing correction quantity X corresponding to data such as the coolant temperature Tw calculated at the coolant temperature calculation means 38.

The ignition timing setting means 41 specifies an area of the ignition timing map MPIC stored in the ROM 26 by using the engine speed N calculated by the engine speed calculation means 36 and a fundamental fuel injection quantity Tp calculated at the engIne load calculation means 39. The ignition timing setting means 41 retrieves or searches an ignition timing (ignition angle) OIG stored in the area and corrects the ignition timing eIG by using the ignition timing correction quantity X calculated at the ignition timing correction quantity calculator means 40 to set a new ignition timing eIG (e!G - OIG + X).

The engine speed setting means 44 takes the coolant temperature Tw calculated at the coolant temperature calculation means 38. Then, the setting means 44 sets the engine speed for switching a fixed ignition timing SPKE to an ignition timing eIG for effecting an ordinary time control, i.e., an ignition timing switching engine speed Nsw.

For example, in this embodiment, as shown in FIG. 6, the range of the coolant temperature Tw is classified into five stages described below:

(1) Tw:5 -200C (2) -200C < Tw 5 OOC (3) OOC < Tw 5 300C (4) 300C < Tw:5 600C (5) 600C:5 Tw The ignition timing switching engine speed Nsw is set to the following values in dependency on the coolant temperature Tw:

(1) 1000 r.p.m. 800 (3) 600 (4) 500 (5) the after It is to be noted that the ignition timing switching engine speed Nsw is set by calculating the engine speed Ne where combustion after complete firing in dependency upon a coolant temperature Tw is stable. The number Nsw is set in advance by an experiment. When the coolant temperature Tw is below 6.OOC, the engine is in a warmingup operating state. The ignition timing switching engine speed Nsw is stored in advance in the ROM 26 as a table of the ignition timing switching revolution number Nsw using the coolant temperature Tw as a parameter.

r.p.m. r.p.m. r. p. m., or ignition timing complete firing is switched immediately 11 When the engine speed N after complete firing is below the ignition timing switching revolution number Nsw set in dependency upon the coolant temperature Tw, the ignition timing switching revolution number setting means 44 outputs a fixed ignition signal SPKH in synchronism with a signal Nc produced in response to detection of the projection 22a (BTDc el) of the crank rotor 22 output from the crank pulse discrimination means 34.

On. the other hand, when the engine speed N exceeds above an ignition timing switching revolution number Nsw set in dependency on the sensed coolant temperature Tw (N > Nsw), the engine speed setting means 44 outputs the ignition timing eIG set at the ignition timing setting means 41 The to the ignition time calculation means 45. ignition time calculation means 45 divides the ignition timing eIG output from the engine speed setting means 44 by the angular velocity w calculated at the angular velocity calculation means 35 to calculate an ignition timing TIG (TIG = OIG/co).

The timer means 46 starts counting of the ignition time TIG calculated at the ignition time calculation means 45 by using the signal G output from the crank pulse discrimination means 34 as a trigger signal. When the count value reaches the ignition time TIG, the timer means 46 outputs an ignition signal SPK to the ignition drive means 47.

12 When the fixed ignition signal SPKH from the engine speed setting means 44 or the ignition signal SPK from the timer means 46 is input to the ignition drive means 47, a current flowing in the primary line of the ignition coil 33 is cut off. Thus, the ignition plug 15 of corresponding cylinder is sparked.

The operation of the embodiment will be described in accordance with the flowchart shown in FIG. 7. This program is executed for each cycle.

At starting of the engine, when a key switch is turned ON, the program is initialized. As a result, a starting control flag FLGST is forcedly set to "1". Initially, at a step S101, the engine speed is calculated in dependency on the output signal from the crank angle sensor 23, and a coolant temperature Tw is calculated in dependency on the output signal from the coolant temperature sensor 21. Then, the program proceeds to a step S102. At step S102, a judgment is made for whether or not the starting control flag FLGST is set to "1". As a result, when the starting control flag set "1", the program proceeds to a step S103.

FLGST is To the contrary, when the starting control flag PLGST is set "0" (zero), the program jumps to a step S108.

It is noted that since the starting control flag FLGST is set to "1" when the program is first executed, the program proceeds from step S102 to step S103.

13 At step S103, an ignition timing switching engine speed Nsw is set by using the ignition timing switching engine speed Nsw calculated at the step S101 as a parameter (see FIG. 6). Then, the program proceeds to step S104. At step S104, a judgment is made as to whether or not the number of engine revolutions N calculated at the step S101 is equal to or above the ignition timing switching revolution number Nsw k Nsw). As a result, when the engine speed N is below the ignition timing switching engine speed Nsw (E < Nsw), the program proceeds to step S105. Thus, the starting control flag FLGST is set to "I" (is maintained at "1").

At step S106, the fixed ignition signal SPKH is output in synchronization with the signal Ne produced in response is to detection of the BTDC el (e.g., el = 1011) output from the crank pulse discrimination means 34. At a step S112, a current flowing in the primary winding of the ignition coil 33 is cut off through the ignition drive means 47 to spark the ignition plug 15 of the corresponding cylinder.

The program of one cycle is thus completed. The program returns to the step S101.

Namely, until the engine speed N exceeds the ignition timing switching engine speed Nsw set in dependency on a coolant temperature Tw, the routine including steps S101 to S106 and S112 is repeatedly executed. Ignition timing control is carried out at the fixed ignition timing.

14 On the other hand, at the step S104, when it is judged that the engine speed -N is above the ignition timing switching engine speed Nsw, the program proceeds to a step S107. At step S107, the starting control flag FLGST is set to "0". The program then proceeds to a step S108. At step S108, the fundamental fuel injection quantity (load data) Tp is calculated from the intake air air flow sensor 20 and the engine speed N calculated at the step S101. Then, the program proceeds to step S109. At this step S109, an ignition timing (ignition angle) eIG is calculated directly or by calculating from the ignition timing map MPIG using the load data Tp and the engine speed N as parameters, respectively. The corrective operation (6IG - OIG + X) is applied to the ignition timing eIG thus calculated by using the ignition timing correction quantity X based on the coolant tem-oerature Tw calculated at the step S101.

Then, at step S110, the ignition time TIG suitable for the present operating state is calculated from an angular velocity co in dependency on the output signal from the crank angle sensor 23 and the ignition timing eIG derived at the step S109 (TIG = GIG/co). At step Slil, the ignition time TIG calculated at the step S110 is set at the timer means 46. Counting is initiated using the signal G indicating the reference crank angle as the trigger signal. When the count value reaches the quantity Q based on the output signal from the intake ignition time TIG, an ignition signal SpR is output. The current in the primary winding of the ignition coil is cut off through the ignition drive means 47. The ignition plug 15 of a corresponding cylinder is sparked through the distributor 32 (step S112). One cycle of the program of is thus completed and returns to the step S101.

Namely, when the engine speed N exceeds the ignition timing switching engine speed Nsw in dependency on a coolant temperature Tw and the starting flag FLGST is set to "0" at the step S107, the ignition timing control is switched from the fixed ignition timing to an ordinary ignition timing control. Then the routine including steps S101, S102, and S108 to S112 is repeatedly executed. Ignition timing control based on the time control system is carried out.

As described above, the present invention provides the ignition timing control system to adjustably set the engine speed for switching the ignitCion timing from the fixed ignition timing to an ordinary ignition timing in dependency on a coolant temperature control. Accordingly, this results in no possibility that the ignition timing is switched to the ordinary ignition timing control in an unstable combustion state. Thus, the engine speed is smoothly increased, resulting in an improved starting performance.

16 I A It is to be noted that while the engine temperature including the coolant temperature is sensed by a thermosensor secured at a cylinder block, it may be sensed directly by a temperature sensor within the cylinder.

It is further to be noted that while the fundamental fuel injection quantity Tp is used as the load data in this embodiment, an intake pipe pressure, a throttle opening degree of the throttle valve may be used as load data in place of the fundamental fuel injection quantity.

As seen from the foregoing description, the ignition timing control system for the engine according to this invention comprises the ignition timing setting means for setting the ignition timing from the ignition timing map is using engine load and the engine speed as parameters, respect-iively, and the engine speed setting means for adjustably setting the engine speed at which switching between the fixed ignition timing set in advance and the ignition timIng set at the ignition timing setting means in dependency on the engine temperature, takes place.

Even in ignition timing control having the time control system, timing for switching an ignition timing from the fixed ignition timing to the ordinary timing control can be adjustably set in dependency on the engine temperature. Thus, not only a satisfactory starting performance can be provided, but also an excellent 17 advantage can be obtained such that the engine speed immediately after starting can be increased.

While the presently preferred embodiments of the present invention have been shown and described, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

is 1 18

Claims

CLAIMS:

1 An ignition timing control system for an engine having a crank rotor mounted on a crank shaft of said engine for indicating a revolutional angle of said crank shaft, a crank angle sensor placed against said crank rotor for detecting said angle to indicate an engine speed, an intake air flow sensor inserted in an intake pipe to said engine for detecting an amount of intake ai-- and a coolant temperature sensor for detecting a temperature of said engine, comprising:

angular velocity responsive to said crank angle sensor for calculating an angular velocity of said crank shaft and for providing an angular velocity signal; calculation means engine load calculation means responsive to said engine speed and said intake ai-r flow sensor for determining a fundamental fuel injection quantity; ignition timing correction means responsive to said coolant temperature for outputting a correction signal to said fundamental fuel injection quantity; ignition timing setting means responsive to said engine speed, said fundamental fuel injection quantity and said correction signal for producing an ignition timing signal from an ignition timing map; and engine speed setting means responsive to said engine speed, said angular velocity, said coolant 19 temperature and said ignition timing signal for setting a switching speed to change said ignition timing signal' to a predetermined ignition timing in dependency on driving conditions of said engine.

2. The ignition timing control system for the engine as set forth in claim 1, wherein said ignition timing setting means sets the ignition timing by the engine speed, the fundamental fuel injection quantity and the ignition timing correction quantity respectively calculated in dependency on the crank angle, the intake air quantity, and a coolant temperature.

3. The ignition timing control system for the engine as set forth in claim 2, wherein said crank pulse is output from a crank pulse discrimination means connected to said crank angle sensor and said engine speed is engine speed calculation means in angular velocity calculated by the calculation means connected to discrimination means.

calculated by an dependency on the angular velocity said crank pulse

4. The ignition timing control system for the engine as set forth in claim 2, wherein said fundamental fuel injection quantity calculated by the engine load calculation means is in 1 1 1 dependency on the intake air quantity calculated by the intake air quantity calculation means in dependency on a sensed value of said intake air flow sensor.

5. The ignition timing control system for the engine as set forth in claim 2, wherein said ignition timing correction quantity is calculated by the ignition timing correction quantity calculation means in dependency on the coolant temperature calculated by coolant temperature calculation means in dependency on a sensed value of said coolant temperature sensor.

6. The ignition timing control system for the engine as set forth in claim 1, which further comprises:

ignition timing calculation means for calculating an ignition timing in dependency on an ignition timing signal or an initial timing signal output f rom said engine speed setting means pulse sensed by the crank angle sensor discriminated by crank pulse discrimination means and a crank and

7. An ignition timing control system for an engine substantially as hereinbefore described with reference to Figures 3 to 7 of the accompanying drawings.

21 Published 1990 at The Patent Office. State House. 66 71 High Holborn. LondonWC1R4TP,Purtherec)pies maybe obtainedfrom The Patent Office. sales Branch. St Mary Cray. Orpington. Kent BR5 3RI' Printed bY MultPlex techniques ltd. St Mary Cray. Kent. Con. l.87