US3626455A

US3626455A - Ignition timing responsive to transmission setting

Info

Publication number: US3626455A
Application number: US882532A
Authority: US
Inventors: Yoshio Toda; Mitsutaka Konno; Masao Nakajima; Toshitake Kikuchi
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1968-12-10
Filing date: 1969-12-05
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07
Also published as: DE1961964A1; GB1298961A

Abstract

An ignition system of which the ignition distributor has two interruptors, one for providing an ignition timing suited to provide a maximum engine power output at full engine load and a minimum fuel consumption at light engine loads and the other providing an ignition timing retarded from the timing dictated by the former interruptor, the latter interruptor being connected with the ignition coil through a control switch operating in accordance with the transmission setting, vehicle speed, engine speed vacuum in the throttle chamber of the carburetor or in the intake manifold of the engine, angular position of the throttle valve in the carburetor or combination of two or more of these factors.

Description

United States a Patent [72] Inventors Appl. No.

Filed Patented Assignee Priorities IGNITION TIMING RESPONSIVE TO TRANSMISSION SETTING I Claim, 19 Drawing Figs.

U.S. Cl 74/860, 123/117 R, l23/146.5 A

Int. Cl 1500K 21/00, F02p 5/00, B60k 33/00 Field of Search 74/860;

Primary E.taminerCarlton R. Croyle Assistant Examiner-Thomas C. Perry A!mrneyJohn Lezdey ABSTRACT: An ignition system of which the ignition distributor has two interruptors, one for providing an ignition timing suited to provide a maximum engine power output at full engine load and a minimum fuel consumption at light engine loads and the other providing an ignition timing retarded from the timing dictated by the former interruptor, the latter interruptor being connected with the ignition coil through a control switch operating in accordance with the transmission setting, vehicle speed, engine speed vacuum in the throttle chamber of the carburetor or in the intake manifold of the engine, angular position of the throttle valve in the carburetor or combination of two or more of these factors.

PATENTEU mm. 7 l97l 3525455 SHEET 1 or 5 'INVENTOR PAIENTEDBEB nan 3525455 SHEET 3 [IF 5 REF. SIGNAL COMPARATOR- SOURCE I I RELAY 49 SWITCH 5O I I I I ENGINE OUTPUT ENGINE OUTPUT I VAC- VEHICLE SPEED INVENTOR; M4 m, mun/r, mm w y M MW ATTO mEY;

PATENTEDDEB nan $526,455

VEHICLE SPEED INVENTORS MA, m, mi'l'sufak mm, mm m MM M 2 ATTogEY IGNITION TIMING RESPONSIVE T TRANSMISSION SETTING This invention relates to an ignition system of an automotive internal combustion engine and, more particularly, to an ignition timing system of the nature adapted to retard the ignition timing when the motor vehicle is driven under predetermined conditions. The ignition timing system proposed by this invention is specifically intended tominimize the percentage of an unburned content of an air-fuel mixture in the exhaust gas from the engine.

The instants at which the ignition is timed are usually so determined as to provide a maximum of power output of the engine operating at a full load and a minimum of power consumption at light engine loads. The ignition timing determined in this manner, however, is known to be inappropriate from the view point of reducing the unburned residues (mostly of hydrocarbons) in the exhaust gas to a minimum.

The presence of unburned or partially burned content in the exhaust gas emitted from the engine is, as is well known, ascribed to the fact that the air-fuel mixture ignited in the combustion chamber of the engine is brought into contact with the less hot wall surfaces of the cylinder head, piston, gasket and cylinder block of the combustion chamber and accordingly that the temperature of the portion of the air-fuel mixture in contact with such wall surfaces is momentarily lowered. This particular portion of the air-fuel mixture, thus cooled down in the combustion chamber,.remains unburned as it leaves the combustion chamber and, as a result, is exhausted to the open air as unburned toxic pollutants. In order to have the air-fuel mixture fully burned before the exhaust gas is discharged out of the engine, it will prove advantageous to have the ignition timing retarded for a suitable period of time in each combustion cycle. The thus retarded ignition timing will, however, be reflected by reduction in the maximum power output of the engine at full load and increase in the fuel consumption at light engine loads.

Whereas, the seriousness of the influence of air pollution problems varies according to geographical areas and it is particularly in urban districts with concentrated population that the emission of unburned toxic pollutants should be minimized. In recognition of this fact, we have found a tendency that a motor vehicle is usually driven at lower speeds on city roads and at higher speeds on expressways and suburban streets. This will imply that, if the ignition timing is retarded while in the city-road driving of the motor vehicle, the percentage of unburned hydrocarbons contained in the exhaust gas could be reduced without sacrifice to the engine power output and fuel economy throughout the varying driving conditions of the vehicle. In this instance, it should be remembcred that the amount of unburned air-fuel mixture in the exhaust gas increases as the vehicle speed decreases.

Thus, the invention contemplates provision of an ignition timing system whereby the ignition timing is retarded under predetermined driving conditions of the vehicle while, in the remaining driving conditions, the ignition is timed in a usual manner to provide for a maximum power output at full engine load and a minimum fuel consumption at light engine loads.

It is therefore an object of the invention to provide an ignition timing system adapted to reduce the emission of unburned toxic pollutants of hydrocarbons without impairing the engine power output and fuel economy throughout the varying driving conditions of the vehicle.

It is another object of the invention to provide an ignition timing system whereby the ignition is timed, under predetermined driving conditions of the motor vehicle, with a certain period of delay from an ignition timing which is so determined as to provide a maximum power output of the engine at full load and a minimum fuel consumption at light engine loads.

It is still another object of the invention to provide an ignition timing system whereby a normal ignition timing is retarded in accordance with suitable control factors representing certain driving conditions of the motor vehicle while in the city-road driving.

A usual ignition system has a battery, switch, ignition distributor, ignition coil, spark plugs, and wiring. The ignition distributor has dual functions. First, it closes and opens a circuit between the battery and ignition coil. When the circuit closes, current flows in the ignition coil and builds up a magnetic field. When the circuit opens, the magnetic field in the coil collapses and a high-voltage surge of current is produced by the coil. The second function of the ignition distributor is to distribute each high-voltage to the correct spark plug at the correct instant by means of a distributor rotor and secondary winding of the ignition coil.

According to the invention, the ignition distributor has a first and second interruptors connected in parallel to the ignition coil, the first interruptor being arranged to provide a normal ignition timing and the second interruptor to provide a retarded ignition timing. Between the second interruptor and primary winding of the ignition coil is connected a control switch which, when closed, control the second interruptor to have .the ignition timing retarded under predetermined driving conditions of the motor vehicle.

The control factors governing the actuation of the control switch may be any of the vehicle speed, engine speed, vacuum level at the intake manifold of the engine, angular position of the throttle valve in the carburetor, and combination of two or more of these factors. Where the vehicle speed, in particular, is to be utilized, it may be represented by a selected gear ratio or, more specifically, by the position of the speed selector lever if the timing system is used together with a manually controlled transmission system and by the hydraulic pressures applied to the front and rear clutches if the timing system is used with an automatic transmission system.

FIG. I shows schematically the overall electrical arrangements of the ignition system incorporating the ignition timing system according to the invention;

FIG. 2 is a sectional view showing essential parts of a manually controlled transmission system with an ignition timing control switch of the invention mounted thereon;

FIG. 3 is a sectional view showing, on an enlarged scale, the control switch mounted on the transmission system shown in FIG. 2;

FIGS. 4-(a) and (b) are sectional views showing front and rear clutch piston switches, respectively, of an ignition timing system used in a motor vehicle having an automatic transmission system;

FIG. 5 shows schematic arrangements of another form of the ignition timing control switch used together with an automatic transmission system;

FIG. 6 is a graphical representation of a relationship between the engine power output and vehicle speed attained where the ignition timing system previously shown is used;

FIGS. 7 and 8 are schematic views illustrating further modified forms of the control switch used in the device according to the invention;

FIG. 9 shows a relationship between the engine power output and vehicle speed attained where the system shown in FIG. 8 is used;

FIG. 10 is a schematic view showing a further modified form of the ignition timing control switch;

FIG. 11 shows a relationship between the engine power output and vehicle speed attained where the system shown in FIG. 10 is used;

FIG. l2-(a) and (b) are sectional views of a further modified form of the ignition timing control switch;

FIG. 13 shows a relationship between the engine power output and vehicle speed attained where the control switch shown in FIG. 12 is used; and

FIGS. 14 to I7 show relationships between the engine power output and vehicle speed attained where still further modified forms of the control switches are used.

Referring to FIG. I, the ignition system as shown by way of example has a battery II, ignition switch 12, ignition coil I3, ignition distributor l4, distributor rotor 15, electric contacts 16a to 16d, spark plugs 17a to 17d, and wiring connecting these elements with each other. The ignition coil 13 has a primary

andsecondary windings

13a and 13b. The primary winding 13a is connected at one terminal with the battery 11 through the ignition switch 12. The ignition distributor 14 has an interruptor 14a which is connected with the other terminal of the primary winding 13a of the ignition coil 13 and which is so arranged as to actuate the ignition coil 13 at an instant to provide a usual ignition timing. The second winding 13b of the ignition coil 13 is grounded at one terminal and is connected at the other with the distributor rotor 15. The rotor 15 is selectively operatively connected to the contacts 160 to 16d disposed therearound. The contacts 16a to 16d, in turn, are connected with the spark plugs 17a to H711, respectively, as shown.

According to the invention, the interruptor i4 is shunted by a second interruptor 14b through a control switch means 18. The interruptor 14b is arranged in a manner to actuate the ignition coil 13 only when the switch means 18 is kept closed so as to provide an ignition timing retarded from the timing to be otherwise determined by the first interruptor Me. More specifically, when the switch means 18 is closed, then the first interruptor 14a first opens with the second interruptor 14h kept closed. The primary winding 13a of the ignition coil 13 thus remains excited to induce no voltage in the secondary winding 13h. As soon as the second interruptor 14b opens, then a voltage is induced in the secondary winding 13!) to of feet an ignition. it is thus the second interruptor 14b which determines the ignition timing in this instance.

The control switch means may be constructed and arranged in different manners depending upon the control factors selected to govern the ignition timing during the city-road driving of the motor vehicle.

Although a variety of control factors may be conceivable, the invention proposes to use, as preferable any of the vehicle speed, engine speed, vacuum level at the intake manifold of the engine, angular position of the throttle valve in the carburetor, and combination of one or two of these factors.

Where the vehicle speed, in particular, is to be utilized, it may be preferable to have the control switch means 18 kept closed at lower vehicle speeds (such as the first, second and third speeds in a four-shift transmission, for instance) and open at higher vehicle speeds (such as the top or fourth speed). in this instance, the vehicle speed may be indexed as the position of the speed selector lever or as the position of the fork rod in the power train, if the ignition system is to be used together with a manually controlled transmission system. if, on the other hand, the transmission system is of automatically controlled type, the control switch may be controlled by the fluid pressures in the hydraulic control circuits in the transmission system.

in consideration of the fact that a motor vehicle is usually driven at the first and second speeds for only limited periods of time and accordingly that the aggregate amount of unburned pollutants emitted while the vehicle is running at these particular speeds can be deemed practically negligible, the control switch herein described and shown is exemplified as being closed only when the third speed is selected.

Now, FlGS. 2 and 3 illustrate an example in which the position of the fork rod in the transmission system is utilized to actuate the control switch.

in FIG. 2, the transmission system, which is shown to be in its neutral position, has a fork rod 19 which is operatively connected through a striking rod 20 to a speed selector lever 21, as customary. The fork rod 20 is also connected rigidly to a shifting rod 22 to selectively couple and uncouple the transmission gears (not numbered) through a coupling sleeve 23 as the striking rod 20 is moved back and forth by the selector lever 21.

A recess 19a is provided in the peripheral wall of the fork rod 19 at a position suited to detect the third speed selected by the movement of the fork rod 19.

As best seen in FlG. 3, a control switch means which is generally designated by l8a is provided to work in association with the fork rod I) having such recess 1911. The control switch i8a as shown has

stationary contacts

24 and 24 connected respectively with the primary winding ll3a of the ignition coil 13 and the second intcrruptor Mb of the ignition distributor i4 (FlG. l). The switch 18b also has a moving contact 25 which is rigidly interposed between an insulating member 26 and moving member 27 extending toward the fork rod 19. The moving member 27 is usually forced against the peripheral wall of the fork rod 19 by the action of a spring 28 mounted behind the insulating member 26.

The control switch I being thus constructed, the moving contact 25 remains isolated from the stationary contacts 24 and 24' when the moving member 27 is held in its retracted position, i.e., in the abutting engagement with the peripheral wall of the fork rod l9. When, however, the fork rod i9 is moved by the lever 21 to select the third speed gear ratio (FIG. 2), the moving member 27 is captured at its leading end by the recess l9a due to the action of the spring 28. Thus, the moving member 27 protrudes into the recess 19a to permit the moving contact 25 to abut against the stationary contacts 24 and 24', connecting the interruptor 14h with the primary winding 13a of the ignition coil 13(FiG. i).

if it is desired to have the control switch closed at two or more vehicle speeds, there may be provided two or more recesses in the peripheral wall of the fork rod 19.

Where, now, the ignition timing system according to the invention is to be installed in a motor using an automatic transmission system, the control switch may be actuated in accordance with changes in the fluid pressures in the hydraulic control circuit of the transmission system.

The fluid pressures occurring at the actuating elements of the brakes and clutches of an automatic transmission system are known to vary with the speed ranges as indicated, as typical, in table I, in which the sign X" refers to a fluid pressure lower than 0.5 kgjcm.

TABLE I Hydraulic control circuit Fluid elements pressures occurring at Speed range I II III IV V 0" in kgJcmJ Parking X X X X 0 3-10 0 X X 0 0 4-12 X X X X X t t t O O O O X 340 X 0 O X X 3-10 X 0 X X X 310 N01'E.-I=Front clutch piston; ll=Rear clutch piston; lil=i irake band. applying; lV= Brake hand, releasing; V Low-reverse brake pistonv l" Front clutch piston Rear clutch piston Brake band, applying lV Brake band, releasing V" Low-reverse brake piston If, therefore, it is desired to have the ignition timing retarded in the first and second drive ranges of the vehicle speed, the control switch means shown by 18 in HO. 1 may be a combination of two hydraulically operative switches to respond to changes in the fluid pressures applied to the front and rear clutch pistons, one of the switches opening responsive to a rise in the fluid pressure at the front clutch piston and the other opening responsive to a rise in the fluid pressure at the rear clutch piston. With the two switches combined in series with each other, ON" and OFF" signals are made available as shown in table ll,

Remarks:

TABLE II Front clutch Rear clutch Combination piston piston two Speed range switch switch switches Parking ()n min t on. Reverse t QUIT... ()If. t Ofi.

TABLE II -(onlinucd Front clutch Rear clutch Combination piston piston two Speed range switch switch switches Preferred constructions of the front and rear clutch piston switches are illustrated in FIGS. 4(a) and -(b). First referring to FIG. 4-(a), the front clutch piston switch 18b, which is shown as closed, has a housing 29. The housing 29 is divided into two

chambers

30 and 31 by a diaphragm member 32. The chamber 30 is an atmospheric chamber which is opened to the air through an aperture 33 and the chamber 3] is a fluid chamber communicating with the piston chamber (not shown) of the front clutch piston through a conduit 34. The diaphragm member 32 is usually forced away from the atmospheric chamber 30 by the action of a spring 35 mounted in the chamber 30 and having a tension strength to overcome a predetermined pressure applied to the diaphragm member 32 through the conduit 34. With the diaphragm member 32 is integrally mounted a moving member 36 extending into the atmospheric chamber 30. The moving member 36 may be made of an insulating material. A moving contact 37 is rigidly mounted on the moving member 36 and the moving contact 37 is, in turn, connected to an insulating member 38 on its side remote from the moving member 36.

Stationary contacts

39 and 40 are mounted on the housing 29 in a manner to usually contact the moving contact 37 when the diaphragm member 32 is held in a position remotest from the

stationary contacts

39 and 40, as shown. These

stationary contacts

39 and 40 are respectively connected to the primary winding 13a of the ignition coil 13 and the second interruptor 14b of the ignition distributor 14. Thus, the front clutch piston switch 18!; is kept closed when the fluid pressure applied to the diaphragm member 32 yields to the tension strength in the spring 35.

When, however, the fluid pressure applied to the front clutch piston is increased to a predetermined level thereby to couple the front clutch (not shown), then the diaphragm member 32 is forced toward the atmospheric chamber 30 against the action of the spring 35 until the moving contact 37 leaves the

stationary contacts

39 and 40. The switch 18b is opened in this manner as a higher fluid pressure is applied to the front clutch piston.

The rear clutch piston switch, which is denoted generally as 180 in FIG. 4(b), is essentially similar in construction to the front clutch piston switch 18b and, as such, the elements corresponding to those appearing in FIG. 4-(a) are numbered similarly with primes suffixed to the reference numerals used in FIG. 4-(a).

The rear clutch piston switch 180 differs from the switch 18b only in that the stationary contacts 39' and 40 are located in a manner to usually contact the insulating member 38 when the diaphragm member 32' is held in a position remotest from the stationary contacts 39 and 40'. Thus, the rear clutch piston switch 18c is kept opened when the fluid pressure applied to the diaphragm member 32' yields to the tension strength in the spring 35'. When, however, the fluid pressure in the conduit 34' increases to a predetermined level thereby to couple the rear clutch (not shown), then the tension strength in the spring 35' is overcome by the pressure applied to the diaphragm member 32 so that the moving contact 37 is moved complete with the moving member 36' and contacts the stationary contacts 39' and 40.

It will be understood that, as the fluid pressure is kept under a predetermined level at the front clutch piston and is increased to a predetermined level at the rear clutch piston, both of the switches 18!; and 18c are closed to actuate the coil 13. The ignition at the first or second speed in the drive range is thus timed by the second interruptor 14b through the switches 18!; and 181: at an instant retarded from the usual timing dictated by the first interruptor 14a (FIG. 1).

As an alternative to the combination of the front and rear clutch piston switches 18b and 18c, the control switch means 18 may be constituted as a switch responsive to the vehicle speed detected at the' output shaft (not shown) of the transmission system. If, in this instance, it is desired to have the ignition timing retarded while the vehicle is driven at an intermediate speed, the control switch means may be constructed as to detect a predetermined limited range of the vehicle speeds and to be closed only in this particular range. An example of such switch means is illustrated in FIG. 5.

In FIG. 5, the switch generally designated as 18d is connected with a speed detector 41 detecting the vehicle speed selected by the transmission system 42 through a speed meter cable 43. Indicated by 44 as connected to the speed detector 41 is a speed meter 44 to visually display the selected speed.

The switch "it! per so may be constructed in some suitable manners andthe electrical arrangement as shown is presented solely for illustrative purpose.

As illustrated, the switch 18d has two

relay switches

45 and 45 connected in series with each other. The relay switches 45 and 45 have

contacts

46 and 46, respectively, which also are connected in series with each other.

The relay switch 45 is a normally-open relay switch, which is arranged to close the contact 46 when energized with a voltage in excess of a predetermined lower limit. The relay switch 45', on the other hand, is a normally-closed relay switch, which opens the contact 46' when energized with a voltage exceeding a predetermined upper limit. The control switch 18d so constructed is kept closed only when the vehicle is driven at a speed within a range corresponding with the range between the upper and lower limits of the voltage applied to the relay switches 45 and 45'. Thus, if these upper and lower limits are determined in a manner to correspond with the upper and lower limits, respectively, of the intermediate speed range, then the ignition coil 13 (FIG. I) will be excited only when the vehicle is driven at a speed falling within this particular range.

The ignition timing retarded in this manner will provide a relationship between the vehicle speed and engine power output as shown in FIG. 6. The plot r" in FIG. 6 indicates the variation of the power output of an engine at full load with respect to the vehicle speed and the area defined by the curve and abscissa includes all the operating conditions of the motor vehicle. The hatched area intervening between the lines 11" and "b" stands for the intermediate speed range of the vehicle.

When the vehicle is driven in the conditions falling within the hatched area, the interrupter 14b is initiated into action to have the ignition timing retarded, thus achieving the purpose of reducing the emission of unburned air-fuel mixture without critically affecting the engine performance. When, on the other hand, the vehicle is driven under conditions falling without the hatched area of FIG. 6, then the ignition is timed at usual instants determined by the first interruptor 14a (FIG. 1) so that a maximum power output at full engine load and a minimum fuel consumption at light engine loads can be assured.

Now, if preferred, the ignition timing in the ignition timing system according to the invention may be controlled in accordance with the engine speed.

As the primary winding 13a of the ignition coil 13 is deenergized with either of the interruptors I40 and 14b actuated, a pulse voltage corresponding to the engine speed is induced across the primary winding 130. This pulse voltage may advantageously be utilized to control the ignition timing control switch, electrical arrangement of an example being illustrated in FIG. 7. i

As shown in FIG. 7, the control switch which is represented generally by l8e has an averaging circuit 47 connected with the primary winding 13a of the ignition coil 13. The averaging circuit 47 is adapted to average the pulse voltage derived from the primary winding 13a. A comparator 48 is connected with the averaging circuit 47 to compare the voltage from the averaging circuit with a reference voltage supplied from a reference signal source 49 connected to the comparator. The

comparator 48 is connected to a relay switch 50 and delivers a control signal to the relay switch S0. The relay switch 50 has two output terminals connected with the first and second interruptors 14a and 14b.

The voltage delivered from the averaging circuit 47 is a DC voltage substantially proportional to the engine speed so that the signal voltage appearing at the output of the comparator 48 represents a specific range of the revolution speed of the engine (not shown). Thus, if the reference signal voltage supplied from the reference signal voltage 50 is determined in a manner to permit the comparator 48 to deliver a signal voltage only when the engine is operating at a speed substantially corresponding to the intermediate speed of the vehicle, the second interruptor 14b of the distributor 14 can be closed when the vehicle is driven at a speed within the intermediate speed range.

It will be understood that the circuit arrangement shown in FIG. 7 is for illustration only and that different modifications will be carried out to selectively actuate the first and second interruptors 14a and 14b.

FIG. 8 shows a further modified example of the ignition control switch which can be used in the ignition system according to the invention. The control switch generally indicated by 18f is so arranged as to be actuated by the vacuum at the throttle chamber of the carburetor which varies in dependence upon the vehicle speed.

As shown, the control switch 18f if constituted as a diaphragm switch and has a vacuum chamber 51 and atmospheric chamber 52 separated from the former by a diaphragm member 53. The atmospheric chamber 52 is opened to the air and the vacuum chamber 51 communicates with the throttle chamber 54 of the carburetor 55 through a conduit 56. The conduit 56 may preferably debouch into the carburetor at a position close t the peripheral edge of the throttle valve 57 fully closed. A connecting member 58 is mounted on the diaphragm member 53, extending outwardly through the atmospheric chamber 52. A set of moving and

stationary contacts

59 and 60 respectively is positioned relative to the leading end of the connecting member 58. The diaphragm member 53 is usually forced away from the vacuum chamber 51 by the action of a spring 61. The moving contact 59 is consequently forced away from the stationary contact 60. The control switch 18f is, in this manner, kept open in a normal state, that is, when the vacuum in the vacuum chamber 51 is not high enough to overcome the compression by the spring 61.

If, therefore, the spring 61 is so selected as to yield to a predetermine force exerted to the diaphragm member 53 by the vacuum in the vacuum chamber 51, then the control switch ll8f will be closed when the vacuum in the throttle chamber 54 is maintained within a predetermined range.

The conditions in which the vehicle is driven with the vacuum in the throttle chamber maintained in such range is illustrated by way of example in FIG. 9. In FIG. 9, curvesp and q stand for the relationship between the engine power output and vehicle speed to maintain at a constant level the vacuum in the throttle chamber. These two curves are dictated by the angular position of the throttle valve 57 and vehicle speed. The curve r shows the power output at full engine load.

Thus, if the control switch 18f is arranged in a manner to close when the vacuum in the throttle chamber falls within the hatched area defined by the curves p and q and abscissa, then the ignition timing will be retarded only when the vehicle is driven under the driving conditions falling within the range corresponding to the hatched area, thereby achieving the purpose of reducing the amount of unburned content in the exhaust gas discharged from the engine. When, on the other hand, the vehicle is driven under conditions outside the hatched area, then the engine will be driven with maximum power output at full load and with minimum fuel consumption at light loads.

If desired, the vacuum may be delivered from the intake manifold of the engine, an example being illustrated in FIG. l0.

The modified control switch l8g as shown in FIG. l0 is also constructed as a diaphragm switch which is essentially similar to the control switch l8f shown in FIG. 8 and, as such, corresponding elements are designated by like numerals. In the control switch 18g, however, the vacuum chamber 51 is arranged to communicate with the intake manifold 62 through a conduit 63 and the moving contact 59 is moved by means of a cam 64 operatively connected with the connecting member 58, as shown. The control switch 18g so constructed is closed when the intake manifold vacuum is maintained at a level falling within a predetermined range. This range of the vacuum in the intake manifold may be determined in numerous manners as will be observed from FIG. I1. In FIG. ll, the hatched area represents the conditions in which the vehicle is driven with the intake manifold vacuum maintained between predetermined upper and lower limits shown respectively by curves s and t. Thus, if the control switch 18g is constructed to close only when the vehicle is driven under the conditions represented by the hatched area, the ignition timing will be retarded under the particular driving conditions of the vehicle.

The ignition control switch used in the ignition system according to the invention may be actuated, if preferred, in accordance with the angular position of the throttle valve, i.e., the aperture at the throttle chamber of the carburetor as illustrated in FIG. 12.

As shown in FIG. 12, the ignition timing control switch 18/: has a cam 65 having an enlarged peripheral edge portion 65a. The cam 65 is connected to and rotated by the shaft 66 of the throttle valve 67 through a connecting member 68. A switch arm 69 is mounted pivotally at one end 69a thereof and is held in abutting engagement with the peripheral edge of the cam 65. Near the other end of the switch arm 69 is located a stationary contact 70. The switch arm 69 is connected to the primary winding 13a of the ignition coil 13 and the contact 70 is connected to the second interruptor 14b (FIG. I). The switch arm 69 is usually forced away from the contact 70 by the action of a spring 71 and held in contact with a stop 72.

When, now, the throttle valve shaft 66 is rotated, then the cam 65 connected therewith is accordingly rotated to force the switch arm 69 away from the stop 71 until it contacts the contact 70, thereby connecting the second interruptor 14b of the distributor 14 to the primary winding 13a of the ignition coil 13. As the throttle valve 67 is further opened, the arm 69 is released from the contact 70 when the enlarged peripheral edge portion 65a leaves the arm 69 so that the primary winding 13a is disconnected from the second interruptor 14b.

The cam 65 may be so shaped that the switch arm 69 is held in engagement with the contact 70 when the throttle valve 67 is in a predetermined range of angular position and is released therefrom when the throttle valve is further opened to provide an increased aperture at the throttle chamber. The control switch 18h can be thus kept closed when the vehicle is driven under the conditions shown by the hatched area in FIG. 13. In FIG. 13, the curves u and v stand for the conditions in which the vehicle is driven with the throttle valve in fixed positions to close and open, respectively, the control switch I811.

It will now be understood that the ignition timing control switch to be used in the ignition system according to the invention can be controlled in accordance with the variation in the speed of either the vehicle or engine or in the vacuum in either the throttle chamber of the carburetor or intake manifold of the engine. These control factors representing the varying driving conditions of the motor vehicle may be, if desired, utilized in combination as has previously been noted.

For instance, the vehicle speed and the vacuum in the throttle chamber may be used together to control the control switch. For this purpose, the control switch may be constituted as a combination of the control switches I8d and 18f shown in FIGS. 5 and 8, respectively, connected in series with each other. Such combination switch will be closed only when both of the

switches

18d and 18f are closed and will be opened when either of the switches 18d and l8fis opened.

FIG. 14 illustrates the conditions in which the vehicle is driven with the ignition timing retarded by the motion of the above-mentioned combination switch. As shown, the curves p and q are identical with those plotted in FIG. 9 and the lines a and b with those in FIG. 6.

Thus, when the vehicle speed exceeds a speed indicated by the line a then the control switch 18d is closed and when the vacuum in the throttle chamber exceeds a predetermined lower limit then the switch 18f is closed. The combination switch is opened as the vehicle speed-is further increased in excess of a speed indicated by the line a or as the vacuum in the throttle chamber further increases in excess of a predetermined upper limit.

l-Iere, it will be appreciated that the control switch 18d to be combined with the switch 18f may be, if preferred, replaced with the control switch 180 (FIGS. 2 and 3) or with the combination of the control switches 18b and 180 (FIG. 4).

Also, the ignition timing in the ignition system according to the invention may be controlled in accordance with the combination of the vacuum in the intake manifold of the engine and the angular position of the throttle valve in the carburetor. In this instance, the ignition timing will be controlled by the combination of the switches 18g (FIG. and 18h (FIG. 12). The range of the driving conditions of the motor vehicle in which the ignition timing is controlled in this manner is indicated by the hatched area in the graph of FIG. 15. In FIG. 5, the curves t and v correspond with the counterparts shown in FIGS. 11 and 13, respectively.

FIG. 16 shows the driving conditions of the motor vehicle in which the ignition is timed in relation to the engine speed and vacuum in the intake manifold of the engine, in which instance the control switches l8e (FIG. 7) and 18g (FIG. 10) may be connected in series with each other to comprise a single combination switch. The lines a and b and the curves 5 and t correspond with the counterparts shown in FIGS. 6 and 11, respectively. In this example, the ignition is timed only when the motor vehicle is driven with the engine speed and intake manifold vacuum maintained within predetermined ranges defined by the lines a and b and curves s and t.

Furthermore, the ignition timing may be controlled in accordance with the combination of the vehicle speed, intake manifold vacuum and angular position of the throttle valve. In this instance, the combination switch to control the ignition timing may be constituted as a combination of the control switches 18a (or 18b and 18g and 1811 connected in series with each other. Thus, the ignition timing is retarded when and only when the vehicle speed is lower than a predetermined level, the-vacuum in the intake manifold of the engine is higher than a predetermined level and the throttle valve of the carburetor is opened to provide a predetermined range of aperture, as indicated by the hatched area defined by the line b and curves t and v in FIG. 7.

What is claimed is:

1. In an ignition system for an automotive internal combustion engine combined with a manually controlled transmission system having a fork rod operatively connected with a speed selector lever through a striking rod and a shifting rod rigidly connected with said fork rod, said fork rod being provided in its peripheral wall with a recess located suitably to detect a predetermined speed range selected by the movement of said fork rod, which ignition system includes a battery, an ignition coil having a primary and secondary windings, said primary winding being connected at one terminal thereof with said battery through an ignition switch and said secondary winding being connected selectively to ignition plugs, and an ignition distributor having a first and second interruptors means, said first interruptor means being connected with the other terminal of said primary winding so as to provide normal ignition timings, said second interruptor means being connected in parallel with said first interruptor means to said primary winding through an ignition timing control switch means which is normally kept open and arranged to provide ignition timings retarded from the timings determined by said first interruptor means, said ignition timing control switch means comprising two stationary contacts connected respectively with said primary winding and said second interruptor means, a moving contact which is rigidly connected with an insulating moving member extending toward said fork rod and usually forced against the peripheral wall of said fork rod by a spring action whereby said moving contact is moved beyond said stationary contacts, said moving member being forced to protrude into said recess by a spring action as said fork rod is moved axially by said speed selector lever to permit said moving contact to abut to said stationary contacts for connecting said second interruptor means with said primary winding, said ignition timing control switch means being closed when the motor vehicle is driven under predetermined conditions, whereby the ignition timing is retarded under said conditions.

* a: a a: