Ignition timing controller for a gasoline engine

Abstract

An ignition timing controller for a gasoline engine on an automobile or the like. The apparatus comprises a thermo sensor actuated in response to variation in an engine cooling water temperature and a negative pressure delay valve. The thermo sensor has a first port connected to an advancer port opening to a carburetor and located near a throttle valve, a second port connected to an advance control port opening into the carburetor and located above the advancer port and a third port connected to a negative pressure chamber of a vacuum advancer. When the water temperature is at a predetermined value or lower, the first and third ports of the thermo sensor are connected with each other through the interior of the thermo sensor. When the water temperature becomes higher than the predetermined value, the first and second ports of the thermo sensor are connected with each other through the thermo sensor. The negative pressure delay valve is divided by a partition into two chambers, one of which is connected to a passage which connects the advancer port of the carburetor and the thermo sensor and the other of which is connected to a passage which connects the thermo sensor and the negative pressure chamber of the vacuum advancer. The partition is provided with an orifice and a check valve adapted to permit fluid flow only in a direction from the one to the other chamber of the negative pressure delay valve. A throat is provided in the second port of the thermo sensor. Thus, when the water temperature is at or lower than a predetermined value, ignition timing is advanced, whereby good performance of the engine is maintained. When the water temperature is higher than the predetermined value, the distributor advance angle is determined according to the opening of the throttle valve and a deep press-down and instant release of the accelerator pedal will not cause advance of ignition timing.

Description

BACKGROUND OF THE INVENTION

This invention relates to an ignition timing controller for a gasoline engine on an automobile and the like.

In a known gasoline engine for an automobile or the like, when a throttle valve in a carburetor is opened to such an extent that its upper edge is rotated slightly above an advancer port opening to the carburetor, the negative pressure prevailing behind the throttle valve is transmitted through the advancer port into a negative pressure chamber of a vacuum advancer which controls the timing for distribution of igniting voltage by a distributor, and ignition timing is advanced, whereby combustion of a fuel-air mixture in engine cylinders is improved and consequently good engine performance is maintained. The improvement of combustion, however, results in rise of combustion temperature, causing in some cases generation of NOx (nitrogen oxides) as the result of a reaction between N.sub.2 and O.sub.2 in fuel gas. Emission of NOx must be controlled in order to purify exhaust gas; therefore, in some operation range of an engine, it is necessary to retard ignition timing or decrease the distributor advance angle in order to reduce NOx or HC (hydrocarbons).

SUMMARY OF THE INVENTION

An object of this invention is to provide an ignition timing controller which maintains good engine performance when the engine temperature is at a predetermined value or lower.

Another object of this invention is to provide an ignition timing controller which maintains a small distributor advance angle to reduce emission of NOx, when the engine temperature is higher than the predetermined value and a throttle valve is not so widely open.

Still another object of this invention is to provide an ignition timing controller which advances ignition timing to thereby allow the engine to maintain good performance when the engine temperature is higher than the predetermined value and the driving speed is increased.

A further object of this invention is to provide an ignition timing controller in which when the engine temperature is higher than the predetermined value, momentary wide opening of a throttle valve does not allow the ignition timing to be advanced, resulting in decrease of NOx and HC emissions.

BRIEF DESCRIPTION OF THE DRAWING

A preferred embodiment of this invention is schematically shown partly in section in the accompanying drawing.

DETAILED DESCRIPTION OF THE EMBODIMENT

In the drawing numeral 1 indicates a carburetor and numeral 2 indicates a throttle valve in its closed or idling position. An advancer port 3 opens to the carburetor 1 at a position slightly above the leading edge of the throttle valve in that position as shown in the drawing. Ignition timing or timing for igniting voltage distribution by a distributor 4 is controlled by a vacuum advancer 5 in which a diaphragm defines a negative pressure chamber 5a. A thermosensor 6 is mounted, for example, on an engine cooling jacket not shown and detects the water temperature. The thermosensor 6 includes an outer cylinder 6a constricted to form an elongate, radially inwardly projecting flange 6b approximately in the middle part thereof. An intermediate cylinder 6c is slidably inserted in the outer cylinder 6a so that its upper end 6d is engageable with the lower edge of the flange 6b. The intermediate cylinder 6c has a lower edge projecting radially inwardly to form a flange 6e. An axially extending air channel 6f is cut on the outer surface of the intermediate cylinder 6c. A rod 6g extends through the flange 6b with a clearance 6h therebetween, and is attached to the upper end 6d of the intermediate cylinder 6c. An inner cylinder 6i which is slidable along the inner surface of the intermediate cylinder 6c projects downwardly from the intermediate cylinder 6c. The upper edge of the inner cylinder 6i projects radially outwardly to form a flange 6t which engages with the flange 6e of the intermediate cylinder 6c. A valve element 6j is carried on the projecting end of the inner cylinder 6i. A thermo wax 6k which expands or controls in response to variation in the engine cooling water temperature is carried on a support 6u located in the upper end portion of the outer cylinder 6a, and faces the rod 6g. When the thermowax 6k expands, it applies downward pressure onto the upper end of the rod 6g and causes it to push down the intermediate cylinder 6c. A compression spring 6l is provided between the intermediate cylinder 6c and the inner cylinder 6i in order to normally ensure engagement between the flange 6t of the inner cylinder 6i and the flange 6e of the intermediate cylinder 6c. The intermediate cylinder 6c is normally pressed against the flange 6b of the outer cylinder 6a by a compression spring 6m provided between the lower end of the outer cylinder 6a and the flange 6e of the intermediate cylinder 6c. A port 6p opens in the lower end 6n of the outer cylinder 6a, in a position facing the valve element 6j carried on the inner cylinder 6i. There are provided a port 6r opening to a clearance 6q between the inner cylinder 6i and the outer cylinder 6a and a port 6s opening to the clearance 6h. A throat 14 is provided in the port 6s.

The port 6r of the thermosensor 6 is connected through a passage 7 to the advancer port 3 of the carburetor 1 and the port 6s is connected through a passage 9 to an advance control port 8 opening slightly above the advancer port 3 to the carburetor 1 as shown in the drawing. The port 6p is connected through a passage 10 to the negative pressure chamber 5a of the vacuum advancer 5. The throat 14 may be provided in the passage 9 instead of the port 6s.

A negative pressure delay valve 11 has a casing 11a in which a partition 11b having an orifice 11c and a check valve 11d defines a negative pressure chamber 11e on one side and a negative pressure delay chamber 11f on the other side. The check valve 11d is adapted to permit fluid flow only in a direction from the negative pressure chamber 11e to the negative pressure delay chamber 11f, so that the check valve 11d remains closed when the negative pressure in the negative pressure chamber 11e is higher than that in the negative pressure delay chamber 11f (or the pressure in the negative pressure chamber 11e is more below the atmospheric pressure than that in the negative pressure delay chamber 11f), and the negative pressure in the negative pressure chamber 11e is gradually transmitted to the negative pressure delay chamber 11f through the orifice 11c. The negative pressure chamber 11e is connected to the passage 7 through a passage 12 and the negative pressure delay chamber 11f is connected to the passage 10 through a passage 13.

In the above embodiment, when the engine cooling water temperature is at a predetermined value or lower, the thermowax 6k remains in its contracted state and is apart from the upper edge of the rod 6g. The upper end 6d of the intermediate cylinder 6c remains in sealing contact with the flange 6b of the outer cylinder 6a under the action of the compression spring 6m, whereby fluid tightness is maintained therebetween. The flange 6t of the inner cylinder 6i is maintained in engagement with the flange 6e of the intermediate cylinder 6c under the action of the compression spring 6l. Accordingly, when the engine cooling water is at a predetermined valve or lower, the valve element 6j stays above the bottom 6n of the outer cylinder 6a, so that the port 6p remains open in communication with the port 6r through the clearance 6q around the inner cylinder 6i. Thus, the negative pressure at the advancer port 3 from behind the throttle valve 2, when it is rotated from its closed or idling position to a position in which its leading edge is between the advancer port 3 and the advance control port 8, is transmitted to the negative pressure chamber 5a of the vacuum advancer 5 through the passage 7, the ports 6r and 6p and the passage 10, to actuate the distributor 4, whereby ignition timing is advanced to maintain good performance of the engine.

When the water temperature rises, the thermowax 6k expands and makes pressure contact with the upper end of the rod 6g to cause it to press down the intermediate cylinder 6c against the action of the compression spring 6m. The valve element 6j is lowered under the action of the compression spring 6l to close the port 6p. At the same time, a clearance is formed between the upper end 6d of the intermediate cylinder 6c and the flange 6b of the outer cylinder 6a, and establishes a fluid communication between the ports 6s and 6r through the air channel 6f on the intermediate cylinder 6c. When the upwardly turned edge of the throttle valve 2 is between the advancer port 3 and the advance control port 8, the fluid having a high negative pressure drawn through the advancer port 3 into the passage 7 is diluted there by fluid having a low negative pressure reaching through the advance control port 8, the throat 14 and the ports 6s and 6r, and the resultant fluid having a reduced negative pressure is drawn into the negative pressure delay valve 11 and transmitted therefrom through the passages 13 and 10 to the negative pressure chamber 5a of the vacuum advancer 5. As this fluid has a considerably reduced negative pressure, the distributor 4 permits only a small advance in ignition timing as compared with what is accomplished by a device known in the art. It will, thus, be noted that the magnitude of advance in ignition timing is controlled according to the size in cross section of a fluid passage through the throat 14.

If the automobile speed is increased and consequently the throttle valve 2 is further opened to locate its upper edge above the advance control port 8 when the port 6p is closed by the valve element 6j, the fluid having a relatively high negative pressure is drawn through the advancer port 3 and the advance control port 8 into the negative pressure delay valve 11, and is, after a brief delay, transmitted to the negative pressure chamber 5a of the vacuum advancer 5. Thus, ignition timing is advanced by the distributor 4 as done in the prior art, whereby good performance of the engine may be maintained.

If the throttle valve 2 is opened only briefly to the position in which its upper edge is rotated above the advance control port 8, a certain time lag obtainable by the negative pressure delay valve 11 is useful to prevent any sudden advance in ignition timing, though fluid having a high negative pressure is introduced through the advance control port 8 as well as the advancer port 3. Therefore, according to this invention, momentary press-down and instant release of the accelerator pedal does not cause any appreciable advance in ignition timing, so that considerable reduction in NOx and HC emissions can be attained over any prior art devices of this sort.

Claims

1. An ignition timing controller for a gasoline engine comprising:

a thermosensor having a first port connected through a first passage to an advancer port opening to a carburetor, said advancer port opening being located at a portion above the upper edge of a throttle valve when in closed position, a second port connected through a second passage to an advance control port opening to said carburetor and located above said advancer port and a third port connected through a third passage to a vacuum advancer of a distributor, said first port being adapted for communication with said third port through said thermosensor over a first engine temperature range no higher than a predetermined value, and with said second port through said thermosensor over a second engine temperature range higher than said predetermined value, said communication of said first and second ports being cut off over said first temperature range and said communication of said first and third ports being cut off over said second temperature range;

a negative pressure delay valve, connected to said first passage and said third passage, for delaying transmission of negative pressure from said carburetor to said vacuum advancer when negative pressure is increased from a predetermined level and for transmitting negative pressure from said carburetor to said vacuum advancer without delay when negative pressure is decreased; and

a throat in said second passage.

2. An ignition timing controller for a gasoline engine as defined in claim 1, wherein said thermosensor comprises an outer cylinder having said first, second and third ports, an intermediate cylinder inserted in said outer cylinder slidably on the inner surface of said outer cylinder, an inner cylinder inserted in said intermediate cylinder slidably on the inner surface of said intermediate cylinder and carrying at one end a valve element adapted to open and close said third port, a thermowax carried on one end of said outer cylinder and adapted for expansion in response to elevation of engine temperature to bring itself into operational engagement with one end of said intermediate cylinder and first and second compression springs provided between said intermediate and outer cylinders and between said inner and intermediate cylinders, respectively.

3. An ignition timing controller for a gasoline engine as defined in claim 1, wherein said negative pressure delay valve comprises a substantially totally closed casing, a partition defining two negative pressure chambers in said casing, an orifice and a check valve formed through said partition, and a port formed through said casing and opening into each of said negative pressure chambers.