JPH0242145A - Valve timing control method for engine - Google Patents

Abstract

PURPOSE:To prevent knocking as well as to improve the input in the title engine by performing the switching of a valve timing in at least one of an intake valve and exhaust valve, in a specific engine speed range, according to the octane number of a fuel. CONSTITUTION:In an engine 1, there are arranged an air cleaner 4, throttle valve 5 and injector 6 in order. An fuel quantity injected from the injector 6 is controlled with an electronic control circuit 7 based on respective detection signals from various type of sensors 20 and 24 to 28 for detecting the operating state of the engine 1. In this case, the electronic control circuit 7 receives the detection signal from a knock sensor 29 for detecting the octane number of the fuel. With the relatively lower octane number, the switching of the valve timing of at least one of an intake valve and exhaust valve in the relatively higher engine speed range.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to a method of controlling valve timing of an engine mounted on a vehicle.

(Prior Art) Japanese Patent Application Laid-Open No. 60-202360 discloses a technique in which a fuel octane number sensor is provided and the ignition timing is changed based on a detection signal from the sensor.

(Problem to be solved by the invention) By the way, if a fuel with a relatively low octane number is used,
When operating with high valve timing compared to low valve timing, high-speed knocking is more likely to occur in a relatively low rotation speed range, making it impossible to set the ignition timing to the advanced side.

On the other hand, if the ignition timing is set to the advanced side, the engine output will be
High-speed valve timing tends to be higher than low-speed valve timing, but when using low-octane fuel, the ignition timing cannot be advanced, so the engine output that can be obtained with high-speed valve timing is the output that can be obtained with low-speed valve timing. As a result, the upper rotational speed range becomes relatively high, and the valve switching rotational speed range needs to be set relatively high accordingly.

However, if the valve timing switching speed range is set as high as above, even though there is sufficient anti-knock performance when using high-octane fuel, there are many speed ranges where the valve timing is operated at low speeds. As a result, it is not possible to expect much increase in output, and fuel efficiency may deteriorate.

An object of the present invention is to provide a valve timing control method that can sufficiently increase power and improve fuel efficiency when using high-octane fuel.

(Means for Solving the Problems) In order to achieve the above object, in the invention of claim 1, the valve timing of at least one of the intake valve and the exhaust valve is changed to a low speed valve timing suitable for a low speed range and a low speed valve timing suitable for a high speed range. An octane number sensor that detects the fuel octane number is installed in an engine that can freely switch between high-speed valve timing and a detection signal from the octane number sensor. At the same time, when the octane number is relatively high, the valve timing is changed in a relatively low rotation speed range.

Further, it is preferable to use a knock sensor as the fuel octane number sensor.

Note that switching the valve timing refers to switching at least one of the valve opening period and the valve lift amount.

(Function) When low octane fuel is used, valve timing is switched in a relatively high rotation speed range, but when high octane fuel is used, valve timing is switched in a relatively low rotation speed range. This increases the operating range with high-speed valve timing and increases power. In this case, the engine is operated in a relatively low rotational speed range with high valve timing, but knocking does not occur because the fuel has high anti-knock properties.

Furthermore, when using fuel with a low octane number, Pezking is more likely to occur when using fuel with a high octane number, so the octane number of the fuel can be determined by detecting engine knocking with a knock sensor.

(Example) Referring to FIG. 1, (1) is an engine body, (2) is an intake passage, and (3) is an exhaust passage.In the intake passage (2), from the upstream end, an air cleaner (4), Throttle valve (5)
An electronically controlled fuel injection type engine was constructed in which an injector (6) was provided and the amount of fuel injected from the injector (6) was variably controlled by an electronic control circuit (7).

In this embodiment, a DOI (C inline four-cylinder engine) is used, in which each cylinder is provided with a pair of intake valves and an exhaust valve, and as shown in FIG. 2, the valve operating mechanism (81) on the intake valve side and a valve operating mechanism (8e) on the exhaust valve side are provided to open and close these intake and exhaust valves.

The two valve mechanisms (81) and (8e) basically have the same configuration, and the intake valve side valve mechanism (81) will be explained below, and the exhaust valve side valve mechanism (8e) will have the same configuration. The description thereof will be omitted.

The intake valve side valve operating mechanism (8I) is provided with a rocker shaft (9) for the intake valve, each of which drives a pair of intake valves of each cylinder.
A pair of driving rocker arms no ('+1) and a free rocker arm ■ in between are supported, and both driving rocker arms (I
O(It) is linked to a low-speed cam formed on the camshaft for the intake valve, and a free rocker arm 0z is linked to a high-speed cam formed on the camshaft, and both drive rocker arms ([) (111 are linked to the switching mechanism a3 When the drive rocker arm (IG (It) and the free rocker arm (It) are not connected, the valve opening period and lift amount are controlled by a low-speed cam. The intake valve is opened and closed at a relatively small low-speed valve timing, and in the connected state, the intake valve is opened and closed at a high-speed valve timing with a relatively large valve opening period and lift amount.

The switching mechanism 03 has one first drive port/lock arm (
A first connecting pin (13a) that can be freely engaged and detached from the free rocker arm 0 inserted in the IG, and a second connecting pin (13b) that can be freely engaged and detached from the free rocker arm (the other second drive rocker arm C11 inserted in the free rocker arm 13). ), and the second driving rocker arm (1
1) with the spring (13c) inserted in the free rocker arm aD.
It is equipped with a regulating bin (13d) that is biased toward the side, and a first connecting bin (13a) is attached to the first driving rocker arm (IQ).
) to the free rocker arm 02) side.
c), and the hydraulic chamber (13e) is communicated with the oil supply passage ('I/D) formed in the rocker shaft (9), and pressurized oil is supplied to the oil pressure chamber (13e) via the oil supply passage (141). When supplied, the first connecting bin (13a) is connected to the free rocker arm ■
At the same time, the second connecting pin (13b) is pushed by the first connecting pin (13a) and the second driving rocker arm (1
1, the double drive rocker arm (4GGT) and the free rocker arm (L?l) are connected to switch the valve timing to high-speed valve timing, and the hydraulic chamber (13e)
When the oil pressure of the spring (13c) decreases, the second connecting pin (13b)
and the first connecting bottle (13a) are pushed back into the free opening/locker arm (LD) and the first driving rocker arm (lG), respectively, and the connection between both the driving rocker arms (IO ('11) and the free rocker arm 0 is released). He made it possible to switch the valve timing to low-speed valve timing.

Then, the oil supply path (+41) is connected to the oil path a9 that supplies oil from an oil pump (not shown) via a switching valve (IG) attached to the end of the cylinder head, and the switching valve (IO's spool valve body ( When IGa) is in the upper closed position, an inflow boat (
IGb) and the outflow port (16c) connected to the oil supply path qΦ communicate only through the orifice hole (IGd), and the outflow port (16c) communicates with the drain port (16e) that opens into the upper space of the cylinder head. Therefore, the oil pressure in the oil supply path aΦ becomes low, but when the spool valve body (16a) is switched to the downward open position, the inflow boat (16b
) and the outflow port (16e) are connected to the spool valve body (IGa).
The outflow port (IGc
) and the drain port (IGe) are cut off, so that the oil pressure in the oil supply path qΦ becomes high.

The spool valve body (IGa) is switched to the open position against the spring (101') by pilot pressure input through the pilot oil passage ('le) branched from the inflow boat (16b). A normally closed solenoid valve (+9) is installed in the pyro-soto oil path (18), and the solenoid valve (191
The energization of the solenoid (19a) of No. 1 is controlled by the output signal VTS from the electronic control circuit (7) as shown in FIG. At this time, the spool valve body (IGa) is switched to the open position, the valve timing is switched to high-speed valve timing as described above, the energization to the solenoid (19a) is stopped, and the solenoid valve l''19 is closed. When this happens, the spool valve body (16a) is switched to the closed position, and the valve timing is switched to low speed knob timing.

Also, to check the switching operation of the spool valve body (IGa),
Outflow port (16g) to switching valve (1G/%Using (16g)
An oil pressure switch (2) was installed that detects the oil pressure of 1 (ic) and turns on when the pressure is low and turns off when the pressure is high.

In Fig. 2, 0 indicates the lubricating oil path for the valve train, and ■ indicates the oil supply path (I/
A high-speed valve train lubricating oil passage connected to the downstream end of D, ■ indicates a cam holder.

The valve timing switching means and oil passage configuration described above are as follows:
This is not particularly different from the patent application filed by the applicant on June 220, 1988, and further detailed explanation will be omitted.

The electronic control circuit (7) includes a rotational speed (Ne) signal from an engine rotation sensor and a throttle sensor C! The throttle opening (θlh) signal from Φ, the intake negative pressure (PB) signal and the intake air temperature (T) from the pressure sensor ■ and temperature sensor ■ connected to the intake passage (2) downstream of the throttle valve (5).
A) Signal, water temperature (TV) signal from the water temperature sensor ■, vehicle speed (V) signal from the vehicle speed sensor, signal from the oil pressure switch ■, 02 signal from the oxygen 4 degree sensor ■ installed in the exhaust passage (3) In automatic vehicles, the parking (P) and neutral (N) signals from the position switch of the shift lever are manually operated, and these signals are used to determine the driving state and calculate the fuel injection amount and change the valve timing.

Here, a knock sensor (2), which is a fuel octane number sensor, is provided in the cylinder block of the engine, and a signal from the knock sensor (2) is input to the electronic control circuit (7).

By the way, as shown in Fig. 3, when we plot the ignition timing advance angle θ2 on the vertical axis and the engine speed Ne on the horizontal axis, and express the high-speed knocking characteristics, the characteristic YH of high octane number is the same as that of low octane number. It increases to the advance side compared to the characteristic Yt. As the octane number of the fuel increases, knocking becomes less likely to occur, allowing the engine to operate at a relatively advanced angle.

On the other hand, the lower limit rotational speed below which the engine output obtained with high-speed valve timing is lower than the output obtained with low-speed valve timing is lower when the engine is operated on the advanced side than when the engine is operated on the retarded side. Therefore, when setting the valve timing switching range to a range equal to or higher than this lower limit rotational speed range, it is possible to increase the engine output by changing the valve timing switching characteristics according to the octane number.

Low octane map θ15 as ignition timing control map
．． and high octane map θ1. The low octane map YL and the high octane map YH as H1 and valve switching characteristic maps are stored in the electronic control circuit (7), and the ignition timing control map θ, 1L1θ+tH and valve timing are set according to the program shown in FIG. Select between switching characteristics YLS and YH.

Regarding θ11L1 θ+tH, θIg+( is set relatively to the advanced angle side, and YL and YH are relatively set to the low rotation side.

This program installs the knock sensor ■ in step ■.
It is determined whether the fuel is low octane fuel or high octane fuel based on the knocking frequency based on the signal from the ignition timing control map. Map θ, 1. At the same time, the above YL is selected as the valve timing switching characteristic, and θIgL and Y are selected in the ignition timing control routine and the valve timing control routine.
Control is performed based on .

On the other hand, when it is determined that the fuel is high octane fuel, proceed from step ■ to step ■ and step ■, select the high octane map θ1□ as the ignition timing control map, and select the above YH as the valve timing switching characteristic. Ignition timing control routine and valve timing control routine θ
1. )l and YH.

(Effects of the Invention) According to the invention of claim 1, the valve timing is switched in a relatively high rotation speed range when using low octane fuel, and in a relatively low rotation speed range when using high octane fuel. Since the detection is performed in several ranges, it is possible to prevent the occurrence of knocking and increase the power, thereby improving the durability and fuel efficiency of the engine. By using a knock sensor as the sensor, the structure of the sensor is simple and relatively inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an engine to which the method of the present invention is applied;
FIG. 2 is a diagram showing the switching device 1h of the valve mechanism, FIG. 3 is a diagram showing knocking occurrence characteristics, and FIG. 4 is a flowchart showing a selection routine for valve timing switching characteristics and ignition timing characteristics. (7)...Electronic control circuit (171...Valve switching mechanism■...Knock sensor (Fuel octane (convex sensor) Ne→ Procedural official book)

Claims (1)

[Claims] 1. In an engine in which the valve timing of at least one of an intake valve and an exhaust valve can be freely switched between a low-speed valve timing suitable for a low-speed range and a high-speed valve timing suitable for a high-speed range, the fuel octane number is changed. An octane number sensor is provided to detect the octane number, and based on the detection signal from the octane number sensor, when the octane number is relatively low, the valve timing is switched in a relatively high rotation speed range, and when the octane number is relatively high, the valve timing is switched in a relatively low rotation speed range. A valve timing control method for an engine, characterized in that the valve timing is changed over at the following times. 2. The engine valve timing control method according to claim 1, wherein a knock sensor is used as the fuel octane sensor.