JPS584185B2 - Electronically controlled fuel injection engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an internal combustion engine in which the amount of intake air is controlled by varying the valve timing of the intake valve. Concerning controlled fuel injection engines.

In general, the opening and closing timing of the intake valve of an internal combustion engine is normally set fixedly regardless of the engine operating state, for example, before the intake top dead center, at a crank angle of 10 degrees or more.
It starts opening at 20 degrees and finishes closing at 50 to 60 degrees after bottom dead center.

The valve timing is set with emphasis on securing maximum output in a high-load operating range where the intake throttle valve is fully open.

Incidentally, in a spark-ignition internal combustion engine, an intake throttle valve is provided to control the amount of intake air (in other words, the engine output), but the intake negative pressure generated downstream of the throttle valve changes depending on the opening degree of the throttle valve. This results in negative work on the piston during the suction stroke, that is, pumping loss, and a considerable portion of the generated thermal energy is consumed as heat loss.

This pumping loss increases as the suction negative pressure becomes stronger.
Therefore, in internal combustion engines for automobiles that are frequently used under low load conditions, this has been a major obstacle to improving fuel efficiency.

By the way, one possible way to control the amount of intake air is to vary the opening period of the intake valve that opens during the intake stroke depending on the driving condition (accelerator opening), thereby substantially increasing or decreasing the effective volume of the cylinder. According to this method, the intake throttle valve can be omitted, and it is possible to reduce pumping noise when the intake valve is opened.

To explain this in detail with reference to Figure 1, the intake valve opening timing is, in principle, revised to 10 to 20 minutes before top dead center, but the valve closing timing is changed in accordance with the accelerator opening. The closer the valve is, the faster it closes, and at the same time the valve lift is smaller (it has to be smaller to reduce the impact).

), and as the load increases, the closing timing is delayed and the lift is increased, and in the high load range, the valve timing is set to the same level as a normal fixed valve timing type.

During the suction stroke, the air-fuel mixture is sucked into the cylinder through the intake valve as the piston descends, but if the intake valve is closed before reaching bottom dead center, the suction action ends at that point, and as a result, the cylinder's The effective volume is determined by the piston position when the intake valve is closed, so the earlier the intake valve is closed, the lower the amount of intake air.

If the amount of intake air is controlled by varying the opening period of the intake valve in this way, unlike installing an intake throttle valve, almost no intake negative pressure will be generated, so pumping loss can be significantly reduced. It becomes possible.

Note that even if the closing timing of the intake valve is variable during the compression stroke, similar control is possible by pushing a portion of the air-fuel mixture once sucked into the cylinder back into the intake system.

By the way, an electronically controlled fuel injection system has been developed for spark ignition internal combustion engines that supplies fuel in synchronization with the engine speed using a fuel injection valve installed in the intake passage. For example, there is a system in which the amount of fuel injection is determined based on engine suction negative pressure and throttle valve opening.

However, with the variable valve timing type of the intake valve as described above, the correlation between the intake negative pressure and the intake air amount becomes weak, making it difficult to accurately detect the intake air amount.

For this reason, installing an air flow make in the intake passage to measure the amount of intake air inevitably increases the cost compared to an intake negative pressure sensor, and the inclined plate type air flow meter in particular causes a slight increase in intake resistance. Due to the increase in suction negative pressure, the effect of reducing bomb pink dust decreases.

The present invention measures the amount of intake air in such a variable valve timing engine by directly or indirectly detecting the valve opening period (in theory, the intake air amount is determined by the valve opening period and the lift amount). However, since the lift amount is large enough that the amount of intake air during the valve opening period does not significantly affect the flow rate, it can be considered that the valve opening period is actually approximately proportional to the amount of intake air.

), and an object thereof is to provide an electronically controlled fuel injection engine that determines the fuel injection amount based on this.

Embodiments of the present invention will be described below based on the drawings.

First, the intake valve mechanism will be explained based on FIG. , the profile changes with the axial displacement of the camshaft 3, and the intake valve opening period and lift (here, as mentioned above, the lift amount is not used to control the air amount, but is mainly used for shock prevention. This is for the sake of

) is formed as a three-dimensional cam (three-dimensional cam) 5 that is variable as shown in FIG.

That is, in the state shown in the figure, as the camshaft 3 moves to the left, the opening period and lift of the intake valve 4 increase, and the amount of intake air increases.

A sprocket wheel 7 is connected to one end of the camshaft 3 via a spline portion 6, and rotates the camshaft 3 in synchronization with engine rotation.

A piston 9 slidably housed in a hydraulic cylinder 8 is connected to the other end of the camshaft 3 so as to be relatively rotatable.
The camshaft 3 is displaced in the axial direction against the return spring 12 by the controlled hydraulic pressure supplied to the camshaft 3 via the hydraulic control device 11 .

The hydraulic control device 11 is operated via a throttle lever 14 that is linked to an accelerator pedal (not shown). Two pistons 16 and 17 are housed in series in the valve housing 15, and a rod is attached to the inner piston 16. A valve body 19 connected via a valve 18 connects a pump passage 21 to which pressure oil from a hydraulic pump 20 is supplied, and the above-mentioned hydraulic cylinder 8.
A communication port 2 with a pressure regulating chamber 25 to which a supply passage 22 communicating with the hydraulic chamber 10 and a return passage 24 communicating with a tank 23 are connected.
Open and close 6.

Reference numerals 27 and 28 are return springs for the pistons 16 and 17, respectively, and the hydraulic pressure in the pressure regulation chamber 25 is transmitted to a pressure compensation chamber 29 defined by the piston 16 via a passage 30.

Therefore, as the amount of leftward displacement of the piston 16 increases, the degree of opening of the port 26 increases, and the oil pressure in the pressure regulating chamber 25 increases.

In addition, since the pressure regulation chamber 25 is connected to the reflux passage 24 with an orifice, the surplus flow is returned to the tank side.
Since the recirculation passage 24 is sufficiently narrowed, the oil pressure in the pressure regulating chamber 25 is approximately proportional to the opening degree of the pump passage 21, that is, the opening area of the passage 26.

Furthermore, since the oil pressure in the pressure adjustment chamber 25 is also transmitted to the pressure correction chamber 29, when the oil pressure changes regardless of the valve opening degree, the piston 16 is displaced in accordance with the oil pressure to automatically correct this.

As a result, the control hydraulic pressure of the hydraulic control device 11 increases in accordance with the amount of depression of the accelerator pedal, and accordingly, the operating amount of the hydraulic cylinder 8 that drives the camshaft 3 in the axial direction increases, and the intake valve of the cam 5 increases. The intake air amount is increased by changing the profile for 4.

In other words, as the accelerator opening increases, the cam position becomes a higher load side, the opening period of the intake valve 4 increases, and the intake air amount increases approximately in proportion to this.

Therefore, the control hydraulic pressure supplied from the hydraulic control device 11 has a close correlation as a function of the intake air amount.

Therefore, in the present invention, the electronically controlled fuel injection system as shown in FIG. It is used as an input signal.

In FIG. 3, 37 is the engine body, 38 is an intake passage, and the fuel injection valve 39 is connected to the intake passage (
The fuel sucked from the tank 41 by the fuel pump 40 is guided to the fuel injection valve 39 via the filter 42 and the pressure regulator 43, and the pulse from the fuel injection control circuit 36 is supplied to the fuel injection valve 39. When the injection valve 39 opens in response to a signal, the air is injected and supplied in accordance with the amount of intake air during intake.

The control circuit 36 receives signals representative of various operating conditions so that an optimum air-fuel ratio can be obtained depending on the engine operating condition.

For example, 45 is a sensor that detects the intake air temperature, 46 is a sensor that detects the engine speed, and the output of the oil pressure sensor 35 described above is also input, and the control circuit 36 determines the optimal injection amount based on these. Determine the fuel injection valve 39
Outputs a pulse signal that controls the valve opening time.

In the figure, 47 is a starter relay switch, 48 is an engine key switch, 49 is a cold start valve that supplies fuel during cold start, and 50 is a cold start valve 4.
9 is a thermo-time switch that controls the operation; 51 is a battery; and 52 is a fuel pump drive relay.

In the above configuration, the control hydraulic pressure of the hydraulic control device 11 is set according to the accelerator opening degree, and the camshaft 3 is displaced in the axial direction in proportion to this, thereby controlling the opening period of the intake valve 4. .

The lift is reduced as the valve opening period decreases so that the shock can be absorbed, but reducing the valve opening period reduces the engine speed, so the effect of the lift amount on the intake inertia is Therefore, the lift amount does not have a large effect on the intake air amount.

The amount of intake air is controlled in accordance with the valve timing of the intake valve 4, and the oil pressure sensor 3 is used to increase or decrease the flow rate of fuel supplied from the fuel injection valve 39 based on this amount of intake air.
5, a signal representative of the intake air amount is sent to the fuel injection control circuit 3.
6, and thereby a pulse signal is set to control the operation of the injection valve 39 so that an appropriate air-fuel ratio is obtained.

Therefore, the amount of intake air can be measured with high accuracy even without an intake negative pressure sensor, and the oil pressure sensor 35 itself has a simpler structure than an air flow meter or the like and does not cause an increase in intake resistance.

As described above, according to the present invention, the amount of intake air can be measured based on the control oil pressure that is a function of the opening period of the intake valve, and the amount of fuel injection can be appropriately controlled in accordance with the amount of intake air. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the opening and closing timing of an intake valve, FIG. 2 is a sectional view of the valve operating mechanism of the present invention, and FIG. 3 is an overall schematic plan view. 3...Camshaft, 4...Intake valve, 5...
...Cam, 8...Hydraulic cylinder, 9...
... Piston, 11 ... Hydraulic control device, 16
, 17... Piston, 19... Valve body,
21... Pump passage, 22... Supply passage, 24... Return passage, 25... Pressure regulation chamber, 35... Oil pressure sensor , 36... fuel injection control circuit, 39... fuel injection valve.

Claims (1)

[Scope of Claims] 1. A valve operating mechanism that varies the closing timing of the intake valve according to the operating condition so as to control the amount of intake air according to the closing period of the intake valve, and An electronically controlled fuel injection engine, comprising: a detection means; and a fuel supply means, which controls a fuel injection amount according to a valve opening period. 2. The electronically controlled fuel injection engine according to claim 1, wherein the valve opening period detection means is a hydraulic pressure sensor of a hydraulic actuator that drives the valve mechanism. 3. Claim 1, wherein the fuel supply means is a fuel injection valve provided in the engine intake passage and a fuel injection control circuit that supplies an injection pulse signal to the injection valve according to the intake valve opening period. The electronically controlled fuel injection engine according to item 1 or 2. 4. Claims 1 to 3, in which the valve mechanism is composed of a camshaft that is displaced in the axial direction in conjunction with a hydraulic cylinder, and a three-dimensional cam whose profile changes in accordance with the displacement in the axial direction of the cam. The electronically controlled fuel injection engine according to any one of paragraphs.