JPS6176723A - Valve timing control device of engine - Google Patents

Abstract

PURPOSE:To prevent abnormal combustion such as knocking by hastening closing timing of an intake valve when an intake temperature is over a set value in an engine with a supercharger. CONSTITUTION:Air is supplied to a combustion chamber 9 of an engine 1 through a compressor 50a of a supercharger 50, a throttle valve 48, an intake pipe 45 and an intake valve 15. An intake pressure sensor 51 and an intake temperature sensor 52 are provided on the intake pipe 45, and especially a control device which is not shown in the figure outputs to a motor 41 by the output of the intake temperature sensor 52 when the intake temperature is over a set value, and a supporting shaft of a cam 23 for driving the intake valve 15 is moved by driving of a motor 1 to hasten closing timing of the intake valve. Then, abnormal combustion at the time of supercharging can be prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a device for controlling valve timing of an engine equipped with a supercharger, particularly when the intake air temperature exceeds a predetermined value.
The present invention relates to a valve timing control device that changes valve timing.

(Conventional technology) A supercharger forcibly pressurizes intake air in addition to naturally intake air.
Although this ensures high charging efficiency in the combustion chamber and achieves high output from the engine, the intake air temperature increases because the intake air is adiabatically compressed, causing abnormal combustion such as knocking. In the fuel injection engine disclosed in Japanese Patent Application Laid-Open No. 58-2177'40, the air-fuel ratio is reduced in the region where the boost pressure becomes high, that is, the amount of fuel injection is increased, thereby increasing the cooling effect of the fuel. This is used to suppress the rise in intake air temperature, thereby preventing abnormal combustion in the high supercharging region.

(Problems to be Solved) Abnormal combustion can also be prevented by the method of increasing fuel debt as described above, but this method is disadvantageous in terms of fuel efficiency.

(Means for solving the above problems) The present invention is configured as follows in order to effectively prevent abnormal combustion such as knocking while solving the problem of fuel consumption.

That is, in the valve timing control device of the present invention, when the intake air temperature detected by the temperature detection means exceeds a set value, the timing change means for changing the valve timing of the intake valve adjusts the timing before the piston reaches the bottom dead center. The present invention is characterized in that the intake valve is configured to at least advance the closing timing of the intake valve so that the intake valve is closed at the same time. In order to detect the intake air temperature, for example, a temperature sensor may be installed in the intake passage downstream of the supercharger, and the temperature may be detected using this.

Further, as the valve timing changing device of the present invention, any conventionally known timing changing device can be used.

Intake valves are normally closed after the bottom dead center of the piston during the intake stroke to ensure high filling efficiency, but in supercharged engines, the intake air temperature rises and there is a risk of knocking. .

If the closing timing of the intake valve is advanced, the inflow of intake air will be restricted, and the temperature rise due to adiabatic compression can be suppressed to that extent. In the present invention, the intake valve is further controlled to close before the piston reaches the bottom dead center during the intake stroke, so that the intake air undergoes a slight adiabatic expansion, thereby increasing the temperature of the intake air. In addition to suppressing the increase in temperature, it is possible to further provide a cooling effect.

(Example) In FIGS. 1 and 2, an engine 1 has a cylinder block 3 and a cylinder head 5 attached to the upper part of the cylinder block 3. The cylinder block 3 has four cylinder bores 3a.

3b, 3c, and 3d are formed in series, and a piston 7 is arranged in each cylinder bore so as to be able to reciprocate. Cylinder bores 3a, 3b, 3c,
Combustion chamber recesses 9 are formed at positions corresponding to each of 3d,
Opening in each combustion chamber recess 9.

An intake port 11 and an exhaust port 13 are formed so as to be. An intake valve 15 is combined with the intake port 11, and an exhaust valve 17 is combined with the exhaust port 13, respectively. The intake valve 15 has a valve stem 15a extending above the cylinder head 5, and is pushed in the valve opening direction by a spring 19 that engages with the valve stem 15a. Similarly, the exhaust valve 17 has a valve stem 17a, and is pushed in the valve closing direction by a spring 21 that engages with the valve stem 17a.

A camshaft 23 is arranged parallel to the row direction of the cylinder bores 3a, 3b, 3c, and 3d in order to periodically open the intake valves 15, and a camshaft 23 is arranged in parallel to the row direction of the cylinder bores 3a, 3b, 3c, and 3d in order to periodically open the exhaust valves 17. 25 is arranged parallel to the camshaft 23 on the opposite side of the camshaft 23 across the cylinder bore. Pulleys 27.29 are fixed to the ends of the camshafts 23.25, respectively, and the camshafts 23.25 are driven in synchronization with the engine crankshaft by a timing belt 31 that is passed around these pulleys 27.29. Ru. Camshaft '2L3
Cams 23a, 23b, 23c, and 23d are formed at positions corresponding to the cylinder bores 3a, 3b, 3c, and 3a, respectively. Further, the cam shaft 23 includes a cam 23a,
A rotating member 33a is located between the cams 23c and 23b.
Rotating members 33b are located between camshafts 2 and 3d, respectively.
It is rotatably supported around 3. FIG. 1 shows a rotating member 33a, on which a tappet 35a is disposed so as to be slidable in the axial direction at a position corresponding to the intake valve 15 for the cylinder bore 3a. The upper surface of the tappet 35a contacts the cam 23a, and the lower surface contacts the end of the valve stem 15a of the intake valve 15. Therefore, the intake valve 15 is opened and closed by the cam 23a via the tappet 35a. Although not shown in the figure, a similar pet is provided on the rotating member 33a at a position corresponding to the intake valve 15 of the cylinder bore 3b, and this intake valve is opened and closed by the cam 23b via a tappet. . Similarly, in the rotating part O 33a,
Tappets are provided at positions corresponding to the intake valves 15 of the cylinder bores 3C13d, and the intake knobs 15 of these cylinder bores are opened and closed by cams 23c and 23d.

The upper parts of the rotating members 33a and 33b are connected to each other by a connecting rod 37 parallel to the camshaft 23, and the connecting rod 37 has a first
Actuation rod 39 is engaged as shown. Operating rod 39
extends in a direction perpendicular to the camshaft, and by moving in the axial direction, the rotating members 33a, 33b can be rotated around the camshaft 23. A motor 41 is provided to move the actuating rod 39 in the axial direction. It acts on In the illustrated mechanism, the opening and closing timing of the intake valve 15 changes depending on the rotational positions of the rotational members 33a and 33b.

The exhaust side camshaft 25 has cylinder bores 3as3b, 3
Cams 25a and 25b are placed at positions corresponding to c and 3d, respectively.
, 25C125d are provided, and these cams 25a, 25
b, 25c, and 25d open and close their respective exhaust valves 17 via tappets 43. As shown in FIG. 1, an intake passage 45 is connected to the intake port 11, and a fuel injection valve 47 is disposed in the intake passage 45.

A throttle valve 48 is disposed upstream of the fuel injection valve 47, and a compressor 50a of a supercharger 50 is disposed further upstream of the throttle valve 48. Further, a turbine 50b of a supercharger 50 is arranged in the exhaust passage 49. Further, downstream of the throttle valve 48 in the intake passage 45, an intake pressure sensor 51 for detecting intake pressure and a temperature sensor 52 for detecting intake air temperature are provided. As shown in FIG. 3, a controller 71, preferably comprised of a microcomputer, is provided to drive the motor 41. The controller 71 includes a rotation speed sensor 70, an intake pressure sensor 51, and a temperature sensor 5.
Signals from a position sensor 76 that detects the current position of the motor 2 and the motor 41 are respectively input manually. The controller 71 calculates these human input signals and issues a predetermined command signal to the drive circuit 72.

In response, drive circuit 72 receives power from battery power supply 73 and outputs a signal for driving motor 41 . The motor 41 is a reversible motor, and rotates in response to the above-mentioned signal to move the operating rod left and right to close the intake valve 1.
Change the valve timing in step 5.

FIG. 4 shows the control contents in the case where a microcomputer is used as the controller 71 in the form of a flowchart. The engine rotation speed N from the rotation speed sensor 70 is read into the controller 71 . Next, the boost pressure, that is, the intake pressure signal P, from the intake pressure sensor 51 is read and compared with a previously stored set boost pressure signal value Pc. When the detected supercharging pressure P is smaller than the set supercharging pressure Pc, the valve timing is not corrected. Boost pressure P
When the supercharging pressure exceeds the set boost pressure Pc, the signal T from the temperature sensor 52 is read and compared with the set value Tc. If the intake air temperature T is smaller than the set value Tc, the target value of the valve timing is not corrected. Therefore, the 2270 target valve timing positions are given by the basic valve timing expressed as a function of the engine speed N at that time, as shown in FIG.

The basic valve timing f (N) is set so that the valve timing becomes slower as the engine speed N increases, and as the engine speed increases, the filling efficiency is improved by pushing. . When the intake air temperature T exceeds the set value Tc, the target valve timing position θ1 and the target position θ1 of the valve timing are used, at least a valve timing with a relatively earlier closing timing of the intake valve. θec is given.

Next, position θ, which represents the current valve timing,
is read by the position sensor 76, and the target position θT and the current position θ are determined.

The motor 41 is driven according to the deviation between the two. Then, the motor 41 is stopped when the deviation becomes zero.

In this example, the boost pressure P does not exceed the set boost pressure Pc,
In an operating state in which the intake air temperature T does not reach the set temperature Tc, the valve timing of the intake valve 15 is determined according to the basic valve timing f (N). For example, at a certain relatively low rotation speed, the intake valve has the characteristic shown by line a in Figure 6, and as the rotation increases, it is shifted to the lag side, and at a certain relatively high rotation speed, the intake valve has the characteristic shown by line a in Figure 6. be praised for the characteristics shown. Then, the boost pressure P is the set value Pc
If the intake air temperature T exceeds the set temperature Tc,
The valve timing of the intake valve is advanced and changed as shown by the broken line characteristic C in FIG.

Referring to FIG. 7, pressure changes in the combustion chamber from the intake stroke to the compression stroke are shown.

The solid line shows an example when the boost pressure and intake air temperature do not exceed the set values, and the solid line shows the change from point A to point B.
The characteristic that leads to is the pressure change while the piston moves from top dead center to bottom dead center during the intake stroke. In this case, the pressure in the combustion chamber decreases by a certain amount from the supercharging pressure P as shown by the line flll, and then gradually recovers to return to the supercharging pressure P at the bottom dead center, that is, point B. Then, when entering the compression stage, the pressure in the combustion chamber increases as shown by line f12, and rises to the value shown at point C at top dead center. The broken line characteristic shows the pressure change when the boost pressure and intake air temperature exceed set values and the valve timing of the intake valve is advanced. In this case, the intake valve is closed at time T1 before bottom dead center. As a result, the pressure in the combustion chamber is the line βI up to the point.
However, from the dot point to the bottom dead center,
It decreases and reaches point E. That is, from point E to point E, the intake air expands adiabatically. Then, it is compressed from the state at point E, and the pressure increases along the special line β3 parallel to the hollow line f22, and reaches the value at point F at the top dead center. Therefore, the pressure at the top dead center is By advancing the valve timing, it can be kept slightly lower.

In addition, when changing the valve timing of the intake valve,
In the above embodiment, since the valve opening period is not changed, the valve opening timing is similarly changed, but by appropriately changing the valve timing etc., only the valve closing timing may be changed.

(Effect of the invention) According to the invention, when the intake air temperature exceeds the set value,
The closing timing of the intake valve is advanced to before bottom dead center. As a result, a slight adiabatic expansion tendency is obtained at the end of the intake stroke, and an increase in intake air temperature can be effectively suppressed. As a result, abnormal combustion such as knocking can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing one embodiment of the present invention, FIG. 2 is a plan view showing the valve operating mechanism thereof, FIG. 3 is a schematic diagram showing the control system of the present invention, and FIG. 4 is a diagram showing the present invention. 5 is a graph showing the relationship between engine speed and basic valve timing. FIG. 6 is a chart showing an example of valve timing change control.
The figure is a graph showing pressure changes within the combustion chamber. 3a...Cylinder bore, 11...Intake port, 13
...Exhaust port, 15...Intake valve, 17...
Exhaust valve, 23.25...camshaft, 23a, 25
a...Cam, 35a...Tappet, 41...
Motor, 50...Supercharger, 51...Intake pressure sensor, 52...Temperature sensor, 71...Controller. Figure 3 Figure 4

Claims (1)

[Claims] In an engine equipped with a supercharger, a temperature detection means for detecting intake air temperature, and a timing change means for changing the valve timing of an intake valve, the timing change means detects the intake air when the temperature detection means exceeds a set value. A valve timing control device for an engine, characterized in that it is configured to at least advance the closing timing of an intake valve so that the intake valve is closed before the piston reaches bottom dead center during a process.