JPH03185231A - Valve timing control device for engine - Google Patents

Abstract

PURPOSE:To improve the hot starting performance by controlling variable the timing of a suction valve and an exhaust valve responding to the rotation frequency of the engine, and increasing the time area of overlapping the suction and the exhaust valves in a hot starting time. CONSTITUTION:The timing of a suction valve and an exhaust valve in an engine is set variable by using a variable mechanism 30. And the rotation frequency of the engine is detected by a detecting means 22. Furthermore, the variable mechanism 30 is controlled by a control means 81 to make the timing of the suction valve and the exhaust valve into a timing responding to the engine rotation frequency. And in a hot starting of the engine, the control of the variable mechanism 30 by the control means 81 is corrected by a correcting means 82 so as to increase the time area of overlapping the suction and the exhaust valves. As a result, the scavenging efficiency in the overlapping period of the suction and the exhaust valves is improved in a hot starting time so as to suppress a smoking of the ignition plug, and a poor starting can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a valve timing control device for an engine.

(Prior Art) Conventionally, as an engine control device, for example,
As disclosed in Japanese Patent No. 191636, a hydraulically driven variable valve timing mechanism is provided on the camshaft of the engine, and a hydraulic passage for introducing engine lubricating oil to the variable valve timing mechanism is formed in the camshaft bearing, It is known that during a specific operation, hydraulic pressure is applied to the variable valve timing mechanism via the hydraulic passage to operate the mechanism and change the valve timing. In this way, it is possible to set the optimum valve timing according to the driving condition, thereby improving fuel efficiency and output.

(Problems to be Solved by the Invention) Such a variable valve timing mechanism can be used, for example: ■ By making the rotational phase of the intake/exhaust cams relative to the camshaft drive gear variable, the entire opening period of the intake/exhaust valves can be controlled by the crank angle. The type that slides along.

■Assuming the engine uses a rocker arm or swing arm, two types of cams with different profiles are installed on the camshaft for one intake/exhaust valve, and only the rocker arm or swing arm corresponding to the cam to be selected is installed on the camshaft. A type that can be moved.

■A type in which the nose part of the cam is slidable in the radial direction of the camshaft relative to other parts, and the profile of the cam is changed by sliding the nose part.

There is. The functions possessed by each of these types of variable valve timing mechanisms will be collectively understood as the concept of "changing valve timing."

In that case, changing the valve timing changes the time area in which the intake and exhaust valves overlap.

In general, the valve timing is adjusted to reduce the overlap time area in the low engine speed range to prioritize combustion stability, and to increase the overlap time area in the high engine speed range to prioritize ensuring output. It will control the variable mechanism.

By the way, when the engine is warmly started, the spark plug tends to smolder, which tends to cause starting failure or inability to start, and also tends to cause a rough idling state after starting.

The present invention was made with the focus on the fact that increasing the scavenging effect during the overlap period of the intake and exhaust valves during a warm start of the engine improves the starting characteristics. The purpose of this invention is to increase the overlap time area of intake and exhaust valves during warm starting of an engine, thereby improving warm startability.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses a variable valve timing mechanism to increase the time area in which the intake and exhaust valves overlap when the engine is warm-started.

Specifically, the solution taken by the present invention, as shown in FIG. 1, includes a variable valve timing mechanism 30 that variably sets the timing of intake and exhaust valves, and a rotation speed detection means that detects the rotation speed of the engine. 22, a timing control means 81 that receives the output of the rotation speed detection means 22 and controls the variable valve timing mechanism 30 so that the timing of the intake and exhaust valves is in accordance with the engine rotation speed; The timing control means 3 is configured to increase the overlapping time area of the intake and exhaust valves during a start.
This configuration includes a start correction means 82 for correcting the control of the variable valve timing mechanism 30 due to the control of the variable valve timing mechanism 30.

(Function) With the above configuration, in the present invention, the variable valve timing mechanism 30 is controlled by the timing control means 81 based on the engine rotation speed detected by the rotation speed detection means 22, and the timing of the intake and exhaust valves is adjusted according to the engine rotation speed. Since it can be switched depending on the number, fuel efficiency and output can be improved.

In that case, when the engine is warmly started, the start correction means 82
As a result, the control of the variable valve timing mechanism 30 by the timing control means 81 is corrected, and the time area in which the intake and exhaust valves overlap becomes larger. Therefore, during a warm start, the scavenging effect during the overlap period of the intake and exhaust valves increases and the ignition is improved. The smoldering of the plug is suppressed, resulting in poor starting and
It is possible to prevent the occurrence of a failure to start and the occurrence of a rough idle state after starting.

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

FIG. 2 shows a V-type DOHC engine equipped with a valve timing control device according to an embodiment of the present invention.

In the figure, 1 is an engine, and the engine 1 includes a left bank L and a right bank R, and each bank L and R is provided with a cylinder 2. Pistons 3 are slidably inserted into each cylinder 2, and these pistons 3 are connected to a crankshaft 4. A combustion chamber 5 is formed in each cylinder 2 by a piston 3.

An intake hole 6 for introducing fresh air into the combustion chamber 5 and an exhaust hole 7 for leading out exhaust gas from the combustion chamber 5 are provided on the bank open side and the anti-bank side of each bank L and R, respectively. This intake boat 6 and exhaust boat 7
are respectively provided with an intake valve 8 and an exhaust valve 9.

Each bank L and H has a camshaft 11 dedicated to the intake valve.
A camshaft 12 dedicated to the exhaust valve is provided in the direction of the crankshaft, and is driven by the crankshaft 4 via a timing belt. The intake cam 11a is provided with an intake cam 11a, and the exhaust camshaft 12 is provided with an exhaust cam 12a. They are in contact with each other, and are configured to open and close the intake valve 8 and the exhaust valve 9 at predetermined timing as the intake camshaft 11 and the exhaust camshaft 12 rotate.

The branch ends of the intake passages 14 are connected to the intake boats 6 of each of the banks L and H. The intake passages 14 are gathered into one and are opened to the atmosphere via an air cleaner 15. Each intake boat 6 is provided with an injector 16 for injecting and supplying fuel. In addition, the intake passage 14
A supercharger 17 is provided, and a bypass passage 18 that bypasses the supercharger 17 is provided. A bypass valve 19 is provided in this bypass passage 18 .

In addition, an intake passage 14 upstream of the intake passage 18
A throttle valve 20 for adjusting the intake air flow rate is provided at the intake passage 14, and an air flow meter 21 for detecting the intake air flow rate is further provided in the intake passage 14 upstream of the intake air flow rate. Further, the engine 1 is provided with a rotation speed sensor 22 as rotation speed detection means for detecting the engine rotation speed.

The engine 1 is also provided with a temperature sensor 25 that detects the temperature of the cooling water. Furthermore, although not shown, a starter for starting the engine 1 is provided, and this starter is connected to the battery via a starter switch. The bypass valve 19 opens in response to intake pressure downstream of the throttle valve.

That is, when supercharging by the supercharger 17 is insufficient, fresh air is supplied to the cylinder 2 through the bypass passage 18, and when supercharging pressure becomes high, supercharging air is relieved to the intake upstream side. The upper limit of boost pressure is regulated to reduce the driving load.

The exhaust camshafts 12 of each bank L and H include
The exhaust camshaft 12 of each bank L, H is provided with a hydraulic variable valve timing mechanism 30 that variably sets the timing of the exhaust valve 9 in a plurality of modes. That is, this variable valve timing mechanism 30 varies the rotational phase of the exhaust cam 12a with respect to the camshaft drive pulley,
As shown in FIG. 5, the entire opening period of the exhaust valve 9 is made variable along the crank angle. This allows the time area in which the exhaust valve 9 and the intake valve 8 overlap to be variable. Specifically, when hydraulic pressure is applied, the overlap time area increases.

The structure of the variable valve timing mechanism 30 will be explained based on FIG. 3. In the same figure, the exhaust camshaft 12
A cylindrical spacer 31 is fixed to the end of the cylindrical spacer 31, and a drive pulley 32 is attached to the outside of the spacer 31. This driving pulley 32 is in sliding contact with the outer periphery of the tip of the spacer 31 at the tip of the boss portion 33 .
The proximal end side of the exhaust camshaft 12 is fixed to a cylindrical connecting member 34 rotatably attached to the exhaust camshaft 12. A first gear 35 is spline-coupled to the other end of the connecting member 34 and fixed by a lock nut 36. A second gear 37 fixed to the tip of the intake camshaft 11 is meshed with the first gear 35 .

An annular piston 38 is installed inside the boss portion 33 of the drive pulley 32 and between it and the spacer 31 . This piston 38 is divided into two parts in the axial direction,
Both divided parts have a plurality of bins 3 arranged at equal intervals in the circumferential direction.
9 are mutually fixed. Helical splines 4 are provided on the inside and outside of the piston 38 in opposite directions.
0.41 is formed. A helical spline 42 is formed on the outside of the spacer 31 with respect to the spline 40 on the inside of the piston, and a helical spline 43 is formed on the outer periphery of the driving pulley boss portion 33 with respect to the spline 41 on the inside of the piston. piston 38
is biased toward the distal end side by a spring 44 installed between the connecting member 34 and the end surface of the connecting member 34.

The exhaust camshaft 12 has an oil passage 4 along its axis.
5 is formed. The oil passage 45 is located in a portion of the exhaust camshaft 12 that corresponds to the bearing portion 60.
A passageway 45a branching from the passageway 45a is provided. An annular groove 61 is formed in the bearing portion 60 so as to coincide with an opening on the outer circumferential surface of the exhaust camshaft of the passage 45a.
is connected to an oil pump (not shown) via an oil supply passage 71.

In addition, as shown in FIG. 4, an oil passage 45 is provided at the rear end of the exhaust camshaft 12 of the left bank L and the right bank R (the end opposite to the side to which the spacer 31 is fixed). Solenoid valves 72 and 73 are provided for opening and closing, respectively.

When the solenoid valves 72 and 73 are opened, the oil in the oil passage is relieved and collected into the cam chamber.

On the other hand, the cylindrical spacer 31 is fixed to the exhaust camshaft 12 with a fixing bolt 47 via a stopper member 46 . The fixing bolt 47 is provided with an axial through hole 48 that communicates with the oil passage 45. Furthermore, a pressure chamber 49 is provided at the tip of the boss portion of the drive pulley 32, at the head of the piston 38, for introducing the hydraulic pressure from the oil passage 45. Therefore, when the solenoid valves 72 and 73 are closed and hydraulic pressure is introduced from the oil pump to these four pressure chambers via the oil passage 45,
The piston 38 compresses the spring 44 and moves in the axial direction, and the spacer 31 and the driving pulley 32, which are fitted with opposite splines 40° 41 formed on the inner and outer peripheries of the piston 38, are arranged so that one side is connected to the other. Rotate relative to.

As a result, the exhaust camshaft 1 integrated with the spacer 31
2 and the drive pulley 32 change, and as shown by the solid line in FIG. 5, the overlap period of intake and exhaust is OL.
I becomes larger, and the overlap time area of intake and exhaust becomes larger. Also, when the solenoid valves 72 and 73 are opened to relieve the oil in the oil passage 45, the piston 38
extends the spring 44 and moves in the axial direction, and the spacer 31 and the drive pulley 32, which engage with the opposite direction splines 40.41 formed on the inner and outer circumferences of the piston 38, are and rotate relative to each other.

As a result, the rotational phase of the exhaust camshaft 12, which is integrated with the spacer 31, and the drive pulley 32 changes, and as shown by the broken line in FIG. The overlap time area becomes smaller.

The two solenoid valves 72, 73 mentioned above are controlled by a control unit 80. The control unit 80 receives output signals from the air flow meter 21, rotation sensor 22, temperature sensor 25, and starter switch 26.

Solenoid valve 72 by the control unit 80
．． The control of 73 will be explained based on the flow shown in FIG. First, after starting, data is input from sensors in step S1, and it is determined in step S2 whether or not the engine 1 is starting. Then, when it is not time to start, step S
4, the engine rotation speed Ne is set to a predetermined rotation speed No (for example, 40
00 rpm) or less. And Ne≦
If NO, the rotation is in the low rotation range, so in step S5 the solenoid valves 72 and 73 are opened to reduce the overlap time area of intake and exhaust, and the process returns. This prevents exhaust gas from being blown back into the intake passage and being carried into the cylinder, improving combustion stability.

On the other hand, when Ne>No, the engine is in a high rotation range, so in step S6, the solenoid valves 72 and 73 are closed to increase the overlap time area of intake and exhaust, and the process returns.

This reduces the amount of residual exhaust gas remaining in the cylinder and increases power output. Therefore, the variable timing mechanism 30 can improve fuel efficiency, output, and the like.

Next, when it is determined in step S2 that it is time to start, the process proceeds to step S3, where it is determined whether or not the engine 1 is in a warm state. Then, when it is cold time, step S
Proceed to step 5 to reduce the overlap time area of intake and exhaust and return.

On the other hand, when it is determined in step S3 that the engine 1 is at a warm time, the process proceeds to step S6, increases the overlap time area of intake and exhaust, and returns. As a result, during a warm start, the scavenging effect during the overlap period of the intake and exhaust valves is enhanced and smoldering of the spark plug is suppressed, thereby preventing the occurrence of poor starting, failure to start, and rough idling after starting. Realized.

In the above flow, in steps 84 to S6, the variable valve timing mechanism 30 is operated in response to the output of the rotation speed detection means (rotation sensor) 22 so that the timing of the intake and exhaust valves is in accordance with the engine rotation speed. It constitutes timing control means 81 for controlling. Further, steps S2 and S3 constitute a start correction means 82 that corrects the control of the variable valve timing mechanism 30 by the timing control means 81 so as to increase the time area in which the intake and exhaust valves overlap when the engine is warm started. ing.

Further, the control unit 80 performs control during engine deceleration. That is, when the engine is decelerating, the solenoid valve 72.
Close 73 and increase the intake/exhaust o/<- lap time area. This increases the amount of air entering the cylinder during engine deceleration when fuel supply is cut.

Therefore, when the fuel supply is restarted after deceleration, the air-fuel ratio is prevented from becoming overrich, and afterburn can be prevented from occurring.

In the above embodiment, the variable valve timing mechanism is provided on the exhaust camshaft, but it may be provided on the intake camshaft, or may be provided on both the intake and exhaust camshafts.

Further, as a variable valve timing mechanism, as in the above embodiment, the rotational phase of the intake/exhaust cams relative to the camshaft drive gear is made variable, and the entire opening period of the intake/exhaust valves is slid along the crank angle. It is not limited to type. In addition, assuming that the engine uses a rocker arm or swing arm, two types of cams with different profiles are installed on the camshaft for one intake/exhaust valve, and the rocker arm or swing arm corresponding to the cam to be selected is installed on the camshaft. The present invention can also be applied to a type in which only the arm is movable. Further, the present invention is also applicable to a type in which the nose portion of the cam is provided so as to be slidable in the radial direction of the camshaft relative to other portions, and the profile of the cam is changed by sliding the nose portion.

(Effects of the Invention) As explained above, according to the engine valve timing control device of the present invention, the valve timing variable mechanism that variably sets the timing of the intake and exhaust valves is provided, and the timing of the intake and exhaust valves is controlled by the engine. The above-mentioned variable valve timing mechanism is controlled so that the timing corresponds to the engine speed, and in this case, when the engine is warmly started, the overlapping time area of the intake and exhaust valves is increased. In addition to allowing you to set the optimal valve timing during a warm start, the scavenging effect increases during the overlap period of the intake and exhaust valves, suppressing spark plug smoldering, preventing starting problems and inability to start. can prevent the occurrence of rough idle conditions.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figures 2 to 6
The figures illustrate an embodiment of the present invention, FIG. 2 is a general schematic diagram, and FIG. 3 is a cross-sectional view of main parts of a variable valve timing mechanism.
FIG. 4 is a control system diagram, FIG. 5 is an explanatory diagram showing valve timing, and FIG. 6 is a flow chart diagram showing control of the control unit. 1... Engine 12... Exhaust camshaft 22... Rotation sensor (rotation speed detection means) 30... Valve timing variable mechanism 81... Timing control means 82... Start correction means

Claims (1)

[Claims] (1) A variable valve timing mechanism that variably sets the timing of the intake and exhaust valves, a rotation speed detection means that detects the engine rotation speed, and a rotation speed detection means that receives the output of the rotation speed detection means and adjusts the timing of the intake and exhaust valves a timing control means for controlling the variable valve timing mechanism so that the timing corresponds to the engine rotation speed; and a timing control means for controlling the variable valve timing mechanism so as to increase the overlapping time area of the intake and exhaust valves when the engine is warmly started. 1. A valve timing control device for an engine, comprising a start correction means for correcting control of a variable valve timing mechanism.