JPH03185230A - Valve timing control device for engine - Google Patents

Abstract

PURPOSE:To carry out a mode conversion without generating a torque shock by converting a valve timing variable mechanism of a suction valve and an exhaust valve into a mode responding to the engine rotation frequency, and correcting the converting rotation frequency of the mode to the lower rotation frequency side in an abnormal combustion. CONSTITUTION:The valve timing of the suction valve and the exhaust valve in an engine is set in plural modes by using a variable mechanism 30. While the rotation frequency of the engine is detected by a detecting means 22, the variable mechanism 30 is converted depending on the detecting output to a mode responding to the engine rotation frequency by a control means 81. Furthermore, while an abnormal combustion of the engine is detected by a detecting means 24, the converting rotation frequency of the mode in the control means 81 is corrected to the lower rotation frequency side by a converting means 82 depending on the detecting output, in an abnormal combustion. Consequently, the converting rotation frequency of the variable mechanism 30 is reset near the crossing point of the torque property lines obtained in the modes, and a mode conversion can be carried out without generating a torque shock.

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 passageway for introducing engine lubricating oil to the variable valve timing mechanism is provided in the camshaft bearing. It is known that the variable valve timing mechanism is actuated by applying hydraulic pressure to the variable valve timing mechanism through the hydraulic passage during a specific operation to 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. “Changing valve timing” encompasses the functions possessed by each type of variable valve timing mechanism.
Let's take this concept as this.

In that case, instead of changing the valve timing continuously, it is also possible to set a plurality of valve timing modes and switch the mode at a predetermined engine speed, that is, at a switching speed, for example. In this case, the mode is switched at an intersection point where the torque characteristic lines obtained in each mode overlap to prevent the occurrence of torque shock.

By the way, for example, when the temperature of the intake air increases and its density decreases, in the low engine speed range, the knocking limit, that is, the ignition timing at which knocking begins, shifts to the retarded side, and knocking does not occur at the normal set advance angle. It is more likely to occur.

- A so-called pre-ignition is likely to occur where a spark point is formed on the spark plug, etc., and the air-fuel mixture is ignited by using the point as a spark before the spark plug ignites.

Such a phenomenon occurs. When abnormal combustion occurs in this way, the output torque of the engine decreases.

Further, even when the occurrence of abnormal combustion is detected and the ignition timing is corrected to the retarded side in order to suppress this, the output torque of the engine decreases due to this correction. therefore,
As mentioned above, if multiple valve timing modes are set and the mode is switched at a predetermined engine speed, the torque characteristic line obtained in the low speed mode will be lower, so the torque characteristic line obtained in each mode will be lower. The intersection point where the torque characteristic lines overlap does not match the switching rotation speed, and a torque shock occurs when switching modes.

The present invention has been made with attention to these points,
The purpose of this is to reduce the occurrence of torque shock at the time of mode switching by switching the mode at the intersection where the torque characteristic lines overlap in the early stage of the occurrence of abnormal combustion.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, when abnormal combustion occurs, the timing of the intake and exhaust valves is switched at a lower rotation speed than usual.

Specifically, the solution taken by the present invention, as shown in FIG. The detection means 22 and the valve timing variable mechanism 30 receive the output of the rotation speed detection means 22.
control means 8 for switching the mode to a mode according to the engine speed;
1, an abnormal combustion detection means 24 that detects abnormal combustion in the engine, and a correction that receives the output of the abnormal combustion detection means 24 and corrects the mode switching rotation speed in the control means 81 to a lower rotation side when abnormal combustion occurs. The structure is such that a means 82 is provided.

(Function) With the above configuration, in the present invention, the variable valve timing mechanism 30 is controlled by the 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 to the engine rotation speed. Since the mode can be changed according to the situation, fuel efficiency and output can be improved.

In that case, when abnormal combustion occurs, the torque characteristic line obtained in the low rotation mode decreases due to the occurrence of abnormal combustion or the ignition timing delay measures taken to cope with this, but based on the detection by the abnormal combustion detection means 24, Then, the correction means 8
2, the mode switching rotation speed in the control means 81 is corrected to the lower rotation side, so the switching rotation speed of the variable valve timing mechanism 30 is reset to near the intersection where the torque characteristic lines obtained in each mode overlap. . Due to this,
Mode switching can be performed without torque shock.

(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 has a left bank L and a right bank R, and each bank L and H is provided with a cylinder 2. Pistons 3 are slidably fitted into the cylinders 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. Further, on the bank open side and the anti-bank side in each bank L and R, there is an intake boat 6 that introduces fresh air into the combustion chamber 5 and an exhaust port 7 that leads out exhaust gas from the combustion chamber 5.
are provided for each. The intake boat 6 and the exhaust port 7 are provided with an intake valve 8 and an exhaust valve 9, respectively.

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 knock sensor 24 for detecting knocking. This knock sensor 24 functions as abnormal combustion detection means for detecting abnormal combustion in the engine 1. The bypass valve 19 opens in response to intake pressure downstream of the throttle valve. That is, supercharger 1
When the supercharging by 7 is insufficient, fresh air is supplied to the cylinder 2 through the bypass passage 18, and when the supercharging pressure becomes high, the supercharging air is relieved to the upstream side of the intake air to set the upper limit of the supercharging pressure. The structure is designed to regulate and reduce the driving load.

The exhaust camshafts 12 of each bank L and H include
A hydraulic variable valve timing mechanism 30 is provided for changing the timing of the exhaust valve 9 into a plurality of modes. That is, this variable valve timing mechanism 30 switches the rotational phase of the exhaust cam 12a with respect to the camshaft drive pulley, and as shown in FIG. , to switch to a second plurality of modes. This switching changes the overlap period between the exhaust valve 9 and the intake valve 8. Specifically, when hydraulic pressure is applied, the overlap period 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 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 pins 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 correspond to an opening on the outer peripheral 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, four pressure chambers are provided at the tip of the boss portion of the drive pulley 32, facing 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
The rotational phase of the drive pulley 32 and drive pulley 32 changes, and the valve timing changes to the second mode in which the overlapping period of intake and exhaust is long. Also, when the solenoid valves 72 and 73 are opened to relieve the oil in the oil passage 45, the piston 3
8 expands the spring 44 and moves in the axial direction, and the spacer 31 and the drive pulley 32, which engage with the splines 40.41 in opposite directions formed on the inner and outer peripheries of the piston 38, rotates relative to the This changes the rotational phase of the exhaust camshaft 12, which is integrated with the spacer 31, and the drive pulley 32,
The valve timing changes to the first mode in which the overlap period between intake and exhaust is small.

The two solenoid valves 72, 73 mentioned above are controlled by a control unit 80. The control unit 80 receives the output signals of the air flow meter 21, rotation sensor 22, and knock sensor 24 manually.

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 engine rotation speed Ne is compared with switching rotation speed No in step S2.

And when Ne<No, it is in the low rotation region, so
In order to switch the variable valve timing mechanism 30 to the first mode, the solenoid valves 72 and 73 are opened in step S3, and the process proceeds to step S5. When switching to the first mode in this way,
The opening/closing timing of the exhaust valve 9 advances from the position shown by the solid line to the position shown by the broken line in FIG. 6, and the overlap period OL2 between the intake valve 8 and the exhaust valve 9 becomes smaller. Due to this,
The exhaust gas is prevented from being blown back into the intake passage and brought into the cylinder, improving combustion stability. The torque characteristic line in this case is shown in Fig. 7 as a solid line A1.
It becomes what is shown in .

On the other hand, when Ne≧No, the rotation is in the high rotation range, so the solenoid valves 72 and 73 are closed in step S4 to switch the variable valve timing mechanism 30 to the second mode, and the process returns. When switching to the second mode in this way, the opening/closing timing of the exhaust valve 9 is delayed from the position shown by the broken line in FIG. 6 to the position shown by the solid line, and the overlap period OLI between the intake valve 8 and the exhaust valve 9 becomes large. Become. This reduces the amount of residual exhaust gas remaining in the cylinder, lowers the temperature inside the cylinder, and improves knocking resistance. The torque characteristic line in this case is shown by solid line B in FIG. Therefore, the variable timing mechanism 30 can improve fuel efficiency, output, and the like.

Next, when the variable valve timing mechanism 30 is in the first mode in the low rotation region, it is determined in step S5 whether the output signal of the knock sensor 24 is equal to or greater than a predetermined value. If the predetermined value is not exceeded, the process returns directly. On the other hand, when the output signal of the knock sensor 24 is equal to or greater than a predetermined value, it is determined that knocking has occurred, and the process proceeds to step S6. A possible reason for knocking to occur in the low rotation range is, for example, that the temperature of the intake air has increased and its density has decreased, causing the knocking limit to shift to the delayed side.

Then, in step S6, the switching rotation speed No. is corrected to the low rotation side by map change processing and is set to No-.

That is, when knocking occurs, the torque characteristic line obtained in the first mode decreases to that shown by the imaginary line A2 in FIG. 7 due to the occurrence of knocking or the delay of the ignition timing taken to cope with the knocking. As a result, at the normal switching rotation speed No, a torque difference C is created between the torque characteristic line A2 obtained in the first mode and the torque characteristic line B obtained in the second mode. However, since the switching rotation speed No. was corrected to the lower rotation side and became No. -1, the switching rotation speed No. was changed to the torque characteristic line A2. B is reset near the intersection where they overlap. This allows mode switching to be performed without torque shock.

In the above flow, steps 81 to S4 constitute a control means 81 that receives the output of the rotation speed detection means (rotation sensor) 22 and switches the variable valve timing mechanism 30 to a mode according to the engine rotation speed. Further, steps S5 and S6 constitute a correction means 82 which receives the output of the abnormal combustion detection means (knock sensor) 24 and corrects the mode switching rotation speed in the control means 81 to a lower rotation side when abnormal combustion occurs. There is.

Further, the control unit 80 performs control in the event that the variable valve timing mechanism 30 fails. Although not shown in the drawings, this engine 1 has an oil jet connected to a cylinder at one end connected to an oil gear gallery to which oil is supplied from an oil pump, and at the other end opening toward the inside of the piston below the piston via a regulator valve. When the oil pressure of the oil gear reaches the set pressure of the regulator valve, this oil jet sprays oil inside the piston to cool the piston. In that case, as shown by the solid line in Fig. 8, the engine 1 enters the high rotation range during normal operation, and when the first mode is switched to the second mode and the solenoid valves 72 and 73 are closed, the oil pressure in the oil passage 45 increases. Therefore, the oil pressure of the oil gear reaches the set pressure of the regulator valve, and the piston is cooled by the oil jet. However, the solenoid valve 72.7
3 is malfunctioning and engine 1 enters the high rotation range, the number of explosions per unit time increases and the piston temperature rises, but the switch from the first mode to the second mode does not occur normally. When the solenoid valves 72 and 73 are left open, the oil pressure in the oil passage 45 does not rise, as shown by the broken line in FIG. Piston cooling function by jet is not achieved. At that time, knocking becomes more likely to occur due to the rise in piston temperature.

Therefore, even if the engine 1 enters the high rotation range, if the variable valve timing mechanism 30 does not switch from the first mode to the second mode, the ignition advance angle is corrected to a small value to prevent knocking. ing.

In the above embodiment, the switching rotation speed is corrected by detecting the occurrence of knocking, but the switching rotation speed may be corrected by detecting the occurrence of pre-ignition. In that case, for example, the preignition may be detected by using a sensor to capture the light emission phenomenon that occurs when the preignition occurs.

Further, 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.

Furthermore, as in the above embodiment, the variable valve timing mechanism varies the rotational phase of the intake and exhaust cams relative to the camshaft drive gear, and slides the entire opening period of the intake and exhaust valves along the crank angle. It is not limited to type.

In addition, two types of cams with different profiles are installed on the camshaft for one intake/exhaust valve, assuming that the engine uses a rocker arm or swing arm.
The present invention is also applicable to a type in which only the rocker arm or swing arm corresponding to the cam to be selected 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 described above, the engine valve timing control device of the present invention includes a variable valve timing mechanism that switches the timing of the intake and exhaust valves to a plurality of modes.
This variable valve timing mechanism is switched to a mode according to the engine speed, and when abnormal combustion occurs, the switching speed of the mode is corrected to the low speed side, so it is possible to set the optimal valve timing according to the engine speed. When abnormal combustion occurs, the switching rotation speed of the variable valve timing mechanism is reset close to the intersection where the torque characteristic lines obtained in each mode overlap, so that mode switching can be performed without torque shock.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figures 2 to 8
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.
Figure 4 is a control system diagram, Figure 5 is a flowchart diagram showing control unit control, Figure 6 is an explanatory diagram showing valve timing, Figure 7 is a torque characteristic diagram explaining torque shock, and Figure 8 is a failure diagram. FIG. 3 is an explanatory diagram showing ignition advance angle correction at the time. 1... Engine 12... Exhaust camshaft 22... Rotation sensor (rotation speed detection means) 24... Knock sensor (abnormal combustion detection means) 30... Valve timing variable mechanism 81... Control means 82...Correction means Fig. 5 Engine [] Prison Fig. 7

Claims (1)

[Claims] (1) A variable valve timing mechanism that sets the timing of intake and exhaust valves in multiple modes, a rotation speed detection means that detects the rotation speed of the engine, and the variable valve timing mechanism that receives the output of this rotation speed detection means. a control means for switching the mode to a mode according to the engine rotation speed; an abnormal combustion detection means for detecting abnormal combustion of the engine; A valve timing control device for an engine, comprising: a correction means for correcting the rotation speed to a lower rotation side.