JPS6235899Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to an ignition timing control device used in automobile gasoline engines and the like.

(b) Prior art As this type of ignition timing control device,
As shown in Publication No. 22038, the sub-advance control is activated by the negative pressure downstream of the throttle valve of the carburetor and controls the ignition timing in the medium and low load range of the engine so that the ignition delay timing is minimized. Some engines are equipped with a main advance mechanism, which is operated by negative pressure introduced through the advance port of the carburetor, and controls the ignition timing to the optimum ignition timing in a high load range. However, such a structure causes problems when used in a gasoline engine having a dual intake structure. That is, in recent automobile gasoline engines, etc., the carburetor is of a dual-tube type having a primary system and a secondary system in order to improve output and reduce fuel consumption. Adopt a dual intake structure in which a low-load intake passage communicating with the primary carburetor system and a high-load intake passage communicating with the secondary carburetor system are provided independently from each other at least up to the vicinity of the intake valve. There is. When the above-described ignition timing control device is applied to an engine having such an intake structure, the carburetor 1
Normally, the sub-advance mechanism is actuated by negative pressure downstream of the throttle valve of the secondary system, and the main advance mechanism is actuated by the negative pressure of an advance port provided in the primary system. . However, in engines with a dual intake structure, the opening time area of the low-load intake passage or low-load intake valve is set to be small in order to strengthen the swirl or increase the air-fuel mixture flow rate. If a large amount is required, the intake resistance downstream of the throttle valve in the primary system of the carburetor will be greater than in a general engine. Therefore, the negative pressure near the throttle valve and downstream of the throttle valve becomes closer to atmospheric pressure than in a general engine due to the increased pressure loss. Therefore, there is an inconvenience that it becomes impossible to obtain enough negative pressure to operate the advance mechanism normally in a region where the average effective pressure of the cylinder is a medium value with respect to the full load. In this case, a problem arises in that the ignition timing is delayed from an appropriate value.

(c) Purpose The present invention was developed with attention to the above-mentioned circumstances, and even when applied to an engine with a dual intake structure, there is no risk of malfunction in the medium load range, and the ignition timing is always required. An object of the present invention is to provide an ignition timing control device for a gasoline engine that can control the ignition timing to an appropriate value.

(d) Configuration In order to achieve the above object, the present invention provides a negative pressure type ignition timing control device having a sub-advance mechanism and a main advance mechanism in a gasoline engine having a dual intake structure. The present invention is characterized in that the sub-advance mechanism is configured to be actuated by pressure downstream of the throttle valve of the secondary system of the carburetor.

(E) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 1, a cylinder head 1 of a gasoline engine is provided with a low-load intake port 4 and a high-load intake port 5, which communicate with a combustion chamber 3 via a common intake valve 2, respectively. The low-load intake port 4 is narrowly constricted and is provided substantially tangentially to the combustion chamber 3 so as to generate a strong swirl within the combustion chamber 3. On the other hand, the high load intake port 5 is the low load intake port 4.
It has a larger open area than that of the combustion chamber, and a check valve 6 is provided at its starting end to allow only the flow of intake air in the direction of the combustion chamber 3 to pass therethrough. Further, a diaphragm double-tube carburetor 7 is disposed on the side of the cylinder head 1, and the primary system 8 of this carburetor 7 is connected to a first
The secondary system 11 is communicated with the high-load intake port 5 via the second intake pipe 12. The primary system 8 of the carburetor 7 is for supplying air-fuel mixture to the low-load intake passage 13 composed of the first intake pipe 9 and the intake port 4, and is located downstream of the ventilate section 14. is provided with a throttle valve 15 that opens and closes in response to an accelerator pedal (not shown). On the other hand, the secondary system 11 of the carburetor 7 is for supplying air-fuel mixture to the high-load intake passage 16 which is composed of the second intake pipe 12 and the intake port 5, and its ventilary section 17. A throttle valve 19 that is opened and closed by a diaphragm mechanism 18 is provided downstream of the throttle valve 19 . The diaphragm mechanism 18 is configured such that the diaphragm 18c is deflected in the thickness direction due to a balance between the pressure within the diaphragm chamber 18a and the biasing force of the spring 18b, thereby moving the actuating rod 18d connected to the throttle valve 19 forward and backward. The ventilate negative pressure of the primary system 8 is introduced into the diaphragm chamber 18a. That is, as the engine speed increases, the amount of intake air passing through the primary system 8 of the carburetor 7 increases, and the ventilary negative pressure of the primary system 8 shifts toward vacuum, the diaphragm mechanism 18 The actuating rod 18d of the secondary system 11 is moved back, and the throttle valve 19 of the secondary system 11 is gradually opened.

An ignition timing control device 22 according to the present invention is attached to a distributor 21 of a gasoline engine having such a dual intake structure. The ignition timing control device 22 includes a sub-advance mechanism 23 for controlling the ignition timing in the medium and low load range of the engine so as to minimize the ignition delay period, and a sub-advance mechanism 23 for controlling the ignition timing in the high load range to the optimum ignition timing. a main advance mechanism 24 for
can be operated by the pressure downstream of the throttle valve 19 of the secondary carburetor system 11. To be more specific, the sub-advance mechanism 23 is
a diaphragm 27 in which a connecting rod 25 connected to a breaker plate (not shown) of the distributor 21 is disposed within a sub-diaphragm case 26;
A diaphragm chamber 28 formed on the back side of the diaphragm 27 is communicated with the inside of the second intake pipe 12 via a negative pressure introduction pipe 29. The main advance mechanism 24 also includes a diaphragm 3 in a main diaphragm case 31 that is connected to the back of the sub-diaphragm case 26.
2, and a flange 34 provided at the extending end of the connecting rod 25 on the connecting piece 33 fixed to the diaphragm 32.
are engaged so as to be freely movable in the axial direction. A sub-spring 35 is interposed between the connecting piece 33 and the diaphragm 27 to form a free movement of a predetermined distance S ₁ between the collar 34 and the inner part of the connecting piece 33. There is. Further, the diaphragm 3
A main spring 37 that urges the diaphragm 32 in the retard direction and a stopper piece 38 that faces the back surface of the diaphragm 32 at a predetermined distance S ₂ are provided in the diaphragm chamber 36 formed on the back side of the diaphragm 32. It is set up. This diaphragm chamber 36 is communicated with an advance port 41 of the primary carburetor system 8 via a negative pressure introduction pipe 39. Note that the spacing S ₁ between the connecting piece 33 and the flange 34 is
The value is set so that the ignition timing when _S1 becomes 0 is the ignition timing that minimizes the ignition delay period. The distance S ₂ between the main diaphragm 32 and the stopper piece 36 is determined by subtracting the ignition timing that minimizes the ignition delay period from the optimal ignition timing (MBT) when the distance S ₂ becomes 0. The ignition timing is set so that the ignition timing is as follows.

With such a configuration, only the throttle valve 15 of the primary system 8 of the carburetor 7 is open when the load is low, but as the load increases, the ventilary negative pressure of the primary system 8 decreases. moves toward vacuum, the actuating rod 18d of the diaphragm mechanism 18 gradually retreats, and the throttle valve 19 of the secondary system 11 also gradually opens (see the middle row of FIG. 2). in this case,
The low-load intake passage 13 is relatively narrow and its intake resistance increases as the amount of intake air increases, so the negative pressure downstream of the throttle valve 15 of the primary carburetor system 8 is , as shown by the solid line a in FIG. 2, shows a value quite close to atmospheric pressure, especially in the medium load range. Therefore, if the diaphragm 27 of the sub-advance mechanism 23 were to be operated using the negative pressure downstream of the throttle valve 15 of the primary system 8, the negative pressure would be as shown by the solid line b in FIG. The advancing angle rapidly decreases as the load increases, and the required characteristics deviate from the required characteristics shown by diagonal lines in FIG. 2. On the other hand, since the throttle valve 19 of the secondary carburetor system 11 is closed or only slightly open in the medium load range, the negative pressure downstream of the throttle valve 19 is indicated by the broken line c in FIG. As shown, it is maintained closer to vacuum than that on the primary system 8 side. Therefore, as in the present invention, the sub-advance mechanism 23 is connected to the throttle valve 19 of the secondary carburetor system 11.
If it is constructed so that it can be activated by downstream negative pressure, there will be no problem that the ignition timing will be delayed in the medium load range, and as shown by the broken line d in Fig. 2, negative pressure advance characteristics that meet the required characteristics can be obtained. becomes possible.

In the above embodiment, a case was explained in which the low-load intake passage and the high-load intake passage were merged near the intake valve, but the present invention is not limited to such a case. The present invention can be similarly applied to an engine in which a high-load intake passage and a high-load intake passage are communicated with the combustion chamber separately through dedicated intake valves.

(F) Effects Since the present invention has the above-described configuration, there is no risk of malfunction in the medium load range even when applied to an engine with a dual intake structure, and the ignition timing can be adjusted to an appropriate level that is always required. Therefore, it is possible to provide an ignition timing control device for a gasoline engine that can control the ignition timing to a specific value.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a system explanatory diagram and FIG. 2 being a characteristic diagram. 2... Intake valve, 7... Carburetor, 8... Primary system,
11...Secondary system, 13...Low load intake passage, 1
6...Intake passage for high load, 19...Throttle valve, 22...Ignition timing control device, 23...Sub advance angle mechanism, 24...Main advance angle mechanism.

Claims (1)

[Scope of utility model registration request] A low-load intake passage communicating with the primary carburetor system,
In a gasoline engine that has a dual intake structure in which the high-load intake passage that communicates with the secondary carburetor system is separated from the other up to at least the vicinity of the intake valve, the ignition timing is minimized during the ignition delay period in the medium and low load range of the engine. A negative pressure sub-advance mechanism is provided to control the ignition timing to the optimum ignition timing in a high load range, and a main advance mechanism is provided to control the ignition timing to the optimum ignition timing in a high load range. An ignition timing control device for a gasoline engine, characterized in that it is configured to be actuated by pressure downstream of a throttle valve in the system.