JPS60240828A - Valve timing controlling device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the excessive rotation of an engine and excessive car speed by variably controlling valve timing so as to increase an engine output in an ordinary engine operating condition while controlling it so as to reduce said engine output when said engine is in an overly operated condition. CONSTITUTION:In a control unit 24 which controls a step motor 23 which is a valve timing varying device, an engine speed N which is detected by an engine speed detecting means 61 based on the output of a crank angle sensor 25, is compared with a first set engine speed N1. When N<=N1, the valve opening phase of an intake valve is advanced with respect to an exhaust valve while, on the contrary, it is delayed when N>N1, by a valve timing determining means 64. An overly operated region judging means 63 judges that the engine is excessively rotated when the engine speed N is above a second set engine speed N2. And, based on the output of this means 63, a valve timing for providing a low output is determined by a valve timing determining means 64, to control the step motor 23.

Description

Detailed Description of the Invention <Industrial Application Field> - The present invention relates to a control device for opening/closing timing (valve timing) of intake valves and exhaust valves of an internal combustion engine, and particularly relates to a protection means for severe operating ranges.

<Prior art> For example, Japanese Patent Publication No. 52-35811 discloses a device that variably controls the opening and closing timing of intake and exhaust valves by changing the relative phase of the camshafts that open and lift the intake and exhaust valves. known.

As the engine rotational speed increases, this system delays the closing timing of the exhaust valve and advances the opening timing of the intake valve, increasing the amount of overlap between the opening timings of the intake and exhaust valves.

This reduces the amount of overlap between the intake and exhaust valve opening timings when the engine rotates at low speeds, prevents the backflow of air taken into the combustion chamber, prevents a decrease in intake filling efficiency, prevents deterioration of exhaust properties, and improves fuel efficiency. We aim to improve On the other hand, when the engine rotates at high speed, the amount of overlap is increased to prevent the delay in introducing the intake air into the combustion chamber due to the inertia of the intake air.
The inertia effect of the exhaust gas is used to improve charging efficiency, improving fuel efficiency, exhaust properties, and output.

However, since such conventional valve control is configured to always increase the output direction of the engine regardless of the operating state of the engine, the output is increased even in severe engine conditions, and for example, the output is increased in the high-speed rotation region. There is a risk of causing rotation and damaging the engine, its exhaust system, and peripheral equipment.
Furthermore, when driving at high speeds, there is a risk that the vehicle speed will increase too much, which is dangerous.

In order to eliminate this inconvenience, Japanese Patent Application Laid-Open No. 58-214628
No. 1 is also available, but this one cuts off the fuel supply to the engine when the engine rotation speed exceeds the set rotation speed, so the intake air is not allowed to flow into the exhaust manifold or catalyst device, which had been at a high temperature. The cold air that was simply discharged now flows, creating a differential expansion that causes so-called thermal shock, resulting in a new problem: breakage or damage.

<Problems to be Solved by the Invention> In view of the above, an object of the present invention is to prevent the occurrence of danger due to excessive output especially under severe engine conditions.

Means for Solving the Problems> To this end, in the present invention, as shown in the claim correspondence diagram in FIG.
The exhaust valve opening/closing timing (hereinafter referred to as valve timing) is controlled, and when a severe engine condition is detected, the valve timing is controlled to reduce the engine output.

As a result, valve timing is variably controlled to increase engine output under normal engine operating conditions, but once the engine enters a severe condition, valve timing is controlled to reduce engine output, Prevent danger from occurring.

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

In FIG. 2, a crank sprocket 3 is attached to a crankshaft 2, which is the output shaft of a reciprocating internal combustion engine 1.
A first timing heald 6 is hooked between the cam sprocket 5 and a first cam sprocket 5 pivoted on an overhead exhaust valve driving camshaft 4, and a spring 7 supported by the engine 1 is attached to the slack side of the first timing heald 6. The tensioner pulley 8 that has received the elastic force is brought into pressure contact to maintain the tension of the first timing heald 6 at an optimum value.

Here, the ratio of the diameters of the crank sprocket 3 and the first cam sprocket 5 is set to 1:2, and the camshaft 4 is rotated at 1/2 the rotational speed of the crankshaft 2.

The camshaft 4 further includes a first cam sprocket 5.
The second cam sprocket is sufficiently smaller in diameter than the second cam sprocket.

A second timing helper is provided between the second cam sprocket 11 and the third cam sprocket 13 having the same diameter as the cam sprocket 5 which is pivotally connected to the camshaft X2 for driving the intake valve. Turn the number 4.

In this case, both cam sprockets 5 and 13 have the same diameter.

A pair of adjustment boots 5 and 16 are brought into pressure contact with the outer surfaces of the tight side a and the loose side of the second timing check 4.

Adjustment levers 17.1B, which rotatably support respective adjustment pulleys 15.16 at one end, are supported in the engine 1 through pins 17a and 18a, respectively, so as to be freely swingable. A return spring 21 supported by the engine 1 is locked to the other end of one of the adjustment levers 17.
Further, the output end of a step motor 23 is connected to the tip of the arm 17b via a wire 22.

The step motor 23 is manually supplied with a control pulse signal from a control device 24 which inputs a detection signal output from an engine operating state detection means. Here, as the engine operating state detection means, for example, a crank angle sensor 25 for detecting the rotational speed of the crankshaft 2. Intake passage 3 that detects intake air amount
Hot wire air flow meter 35 installed in 6
, a throttle sensor 40 that detects the opening of the intake throttle valve. Vehicle speed sensor 4 provided in vehicle speedometer (speedometer) 41
21 engine cooling water temperature sensor, starter morph support, etc. In this embodiment, the step motor 23 is operated according to the engine rotational speed, and the tension side a of the timing belt 14 is activated based on the action described later. Control length increase/decrease.

The adjustment lever 17 on the loose side is interlocked with the adjustment lever 17 on the tight side via the connector lever 26. That is, the connecting lever 2 is attached to the adjusting lever 18 between the pin 17a and the rotating shaft of the adjusting pulley 15.
A guide pin 28 provided on the adjustment lever 18 is slidably inserted into a slit of a predetermined length provided at the other end of the connecting lever 26. A tension spring 30 is interposed between a pin 29 provided on the lever 26 and a tension spring 30 .

The exhaust gas of the internal combustion engine 1 equipped with such a variable valve timing device rotates a turbine impeller 33 of a supercharger 32 through an exhaust passage 31, and rotates a compressor rotor 34 that is integrally connected to the turbine impeller 33. As a result, the intake air measured by the true wire air flow meter 35 is pressurized and supercharged, and is sucked into the engine under the metering action of the intake throttle valve 37 interposed in the intake passage 36. The injection amount of the fuel injection valve 38 is controlled by the control device 24 which manually receives detection signals from the various engine operating state detection devices.

FIG. 3 shows a functional block diagram of the control device 24 for controlling valve timing.

In the figure, the rotational speed detection means 61 is the crank angle sensor 2.
The engine rotational speed N is detected by inputting the detection signal output from 5.

The valve timing determining means 62 determines the detected engine rotation speed N and a preset first rotation speed N.

As shown in Fig. 4, when N≦N, the intake valve is advanced in opening phase relative to the exhaust valve, and when N>Nl, the valve timing is determined to be delayed. do.

The severe region determining means 63 determines that the detected engine rotation speed N is a preset second rotation speed N (for example, 7.OOOO
rpm>Nl), it is determined that the engine is rotating excessively. When this determination result is output, the severe region valve timing determining means 64 determines the valve timing that provides a low output.

The driving means 65 outputs a pulse signal in response to the output signals received from the valve timing determining means 62 and 64 to rotate the step motor 23 by a predetermined amount.

The control device 24 is constituted by a microcomputer including, for example, an input/output processing device, a central processing unit 1, a storage device, and the like. Also, both valve timing determining means 62
．． 64 can also be shown as a functional block as a single valve timing determining means in FIGS. 1 and 3.

The operation related to the above configuration will be explained using the flowchart of FIG. 5.

When the engine 1 is operated, the crankshaft 2 rotates, and the crank sprocket 3. The exhaust valve camshaft 4 is rotated via the first timing heald 6 and the first cam sprocket 5. Since the diameter of the first cam sprocket 5 is twice that of the crank sprocket 3, the rotational speed of the latter is 1/2 that of the former.

The above rotation of the camshaft 4 for the exhaust valve is caused by the second cam sprocket 11. Second timing belt 14 and third
The intake valve camshaft 12 is rotated via the cam sprocket 13 of the intake valve. The rotational speed of the camshaft 12 is 2
They are equal because the diameters of the two cam sprockets 11 and 13 are the same.

In step (S) 71 of the flowchart shown in FIG. and the second set rotational speed N2.

If N≦N2, the comparison is made with the first set rotational speed N1 at 37g, and as a result N>N.

If so, in S75, the valve timing determining means 62 outputs a signal for retarding the intake valve to the driving means 65. As a result, a control signal is input to the step motor 23 to send out the wire 22. Therefore, the spring force of the return spring 21 causes the adjustment lever 17 to swing counterclockwise around the pin 17a by a predetermined amount, thereby loosening the tension on the tension side a of the second timing belt 14. At this time, since the phase relationship between the crank sprocket 3 and the first cam sprocket 5 is specified for the camshaft 4 for the exhaust valve, the tension on the tension side a can be relaxed by moving the tension side a to the left in the figure. The third cam sprocket 13 is rotated counterclockwise to the retard side by the amount of the feed, thereby retarding the opening/closing timing of the intake valve as shown in FIG. As a result, the over-ramp amount of the opening timing of the intake/exhaust valves is reduced, and the amount of intake air sent into the combustion chamber with a large boost pressure that blows through into the exhaust passage 31 is reduced, or blow-by is prevented.

This makes effective use of fuel, improves supercharging efficiency, increases output, and improves fuel efficiency and exhaust properties.

Since the length of the tension side a of the second timing heald 14 is shortened, the length of the slack side becomes longer, but the adjustment lever 17
As the loosening side is rotated in the counterclockwise direction, the loosening side adjustment lever 18 is also rotated counterclockwise via the connecting lever 26 to move the adjusting pulley upward in the figure to prevent the loosening side heald tension from loosening.

Here, the elastic force of the tension spring 30 balances the tension of the slack side of the timing belt 14 and functions to maintain the tension at a predetermined value.

When the engine rotational speed shifts from high speed to low speed, that is, S7
If it is found in step 3 that N≦N1, then in step 374 the valve timing determining means 62 outputs a signal to switch the intake valve to the advance side, operates the step motor 23 via the driving means 65, and disconnects the wire. Pull 22.

As a result, as shown in FIG. 4, the amount of over-ramp in the opening timing of the intake and exhaust valves is increased. The amount of overlap at this time is matched to an optimum value in order to prevent the backflow of air taken into the combustion chamber, thereby preventing a decrease in intake air filling efficiency, preventing deterioration of exhaust properties, and improving fuel efficiency.

On the other hand, in S72, if the severe region determining means 63 detects that the rotational speed is excessive (N > N z ), the severe region valve timing determining means 64 advances the opening/closing timing of the intake valve (S74).・Increase the amount of exhaust valve opening timing overramp. As a result, supercharged air blows into the exhaust port at the beginning of the intake stroke, reducing charging efficiency and reducing engine output, thereby preventing engine rotation from becoming excessive. At this time, the exhaust energy is also reduced, which prevents the supercharger from overspeeding and prevents the supercharging pressure from becoming excessive, thereby protecting the intake system and the engine.

The above valve timing control characteristics are shown in FIG.

In addition to the rank angle sensor as in the embodiment, the engine rotational speed detection means may be a combination of the vehicle speed and the gear position of the transmission, or may be replaced by the throttle angle or the intake air amount.

Furthermore, in the above embodiments, an example was described in which the present invention was applied to an internal combustion engine with a supercharger. However, when applying the present invention to a normal internal combustion engine without a supercharger, it is necessary to control the overramp amount of the intake and exhaust valves by controlling valve timing, which is the opposite of that for a case with a supercharger. . That is, NUN
In the case of , the intake air filling efficiency is increased by reducing the valve over-ramp amount to prevent intake air backflow and effectively utilizing inertia, and in the case of NZ>N≧N1, the valve over-ramp amount is increased, By preventing the delay due to inertia of intake air introduction, the intake air filling efficiency is increased and the output direction is improved.

If N≧N2, by reducing the valve overlap amount again, that is, by delaying the intake valve opening timing, a delay in introduction due to the inertia of the intake air is caused, which reduces the charging efficiency and output, reducing the engine power. Prevent excessive rotation.

In addition to using the above-mentioned winding transmission device, the variable valve timing device may also include a variable device in the hydraulic tappet or other valve mechanism itself. In this case, the drive mechanism may be a solenoid valve or the like instead of the step motor 23. It is commonly used. The variable valve timing control may not be a two-stage control type as in the embodiment, but may be a continuously variable speed control type. Either of the camshafts 4°12 may be used for the intake valve or the exhaust valve depending on the purpose, and the variable control of the relative phase of both camshafts may be performed by changing the phase of either camshaft or both. It is clear that the phase may be changed.

FIG. 7 shows another embodiment of the invention. In the above embodiment, the severe condition of the engine was taken as an example where the rotational speed was N2 or more, but in this embodiment, the vehicle speed ■ is set to the limit vehicle speed V3, for example, 180
The case of km/h is taken as an example.

That is, in FIG. 7, the severe region determining means 63a compares the vehicle speed signal input from the vehicle speed sensor 42 via the vehicle speed detecting means 67 with a preset vehicle speed. V, the valve timing of the intake valve is advanced by the severe region valve timing determining means 64 at 374 (in the case of a supercharged internal combustion engine). As a result,
Engine output is reduced to prevent the vehicle from increasing too fast when driving at high speeds. The rest is the same as the previous embodiment, so explanations will be omitted.

In order to detect the vehicle speed, in addition to the embodiments, the rotational speed of the transmission output shaft may be detected (or a combination of the engine rotational speed and the gear position of the transmission, etc.) may be used.

In this way, the harsh condition for an engine is the engine rotation speed.

Vehicle speed, intake air amount, boost pressure, intake throttle valve opening,
Needless to say, this can be determined based on overload on the diesel engine and other factors.

<Effects of the Invention> As described above, according to the present invention, the valve timing of the intake and exhaust valves is controlled to ensure output in the normal operating range, but once the engine enters severe conditions, the timing is controlled to reduce the output. Since the valve timing is controlled, under severe conditions, it is possible to prevent dangers such as over-revving the engine, excessively increasing vehicle speed, and excessively increasing boost pressure.

In addition, since fuel is not shut off even under severe conditions, the shock to the engine is not large, and since cold air is not flowed into the exhaust manifold and catalyst, which were previously hot, there is no thermal shock and damage or breakage is prevented. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a block diagram showing a first embodiment of the present invention, FIG. 3 is a block diagram showing a functional configuration of the same control device, and FIG. A graph showing the intake/exhaust valve timing control characteristics of the embodiment, FIG. 5 is a flowchart showing the operation of the control device in FIG. 3, FIG. 6 is a torque characteristic diagram based on the valve timing control of the first embodiment, and FIG. The figure is a block diagram of a control device showing a second embodiment of the present invention, and FIG. 8 is a flowchart showing the same operation. 1... Reciprocating internal combustion engine 11... Second cam sprocket 13... Third cam sprocket 14...
・Second timing held 17.18... Adjustment lever 22... Wire 23... Step motor 24... Control device 25... Crank angle sensor 26... Connecting gear wheel 42... Vehicle speed Sensors 62, 64...Valve timing determining means 63.6
3a... Severe region determination means 65... Drive means patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima

Claims (1)

[Scope of Claims] (1) A variable valve timing device that variably operates the relative phase of the opening/closing timing of intake and exhaust valves, an engine operating state detection means, and a severe operating range of the engine based on the detection signal of the detection means. severe region determining means for determining the relative phase of the opening/closing timing of the intake/exhaust valves based on the detection signal of the detecting means; Severe region valve timing determining means for selecting the relative phase of the opening/closing timing of the exhaust valve to the engine low output side; and a severe region valve timing determining means for selecting the relative phase of the opening/closing timing of the exhaust valve to the engine low output side; a driving means for obtaining the relative phase of the opening/closing timing of the
A valve timing control device for an internal combustion engine, characterized in that it is provided with: (2) The engine operating state detecting means includes an engine rotational speed detecting means, and the valve timing determining means includes a preset first valve timing determining means.
The internal combustion engine according to claim 1, wherein the internal combustion engine is a means for switching the relative phase value of the valve opening/closing timing of the intake valve and the exhaust valve on a high-speed side and a low-speed side with the engine rotational speed as a boundary. Valve timing control device. (3) The severe region valve timing determining means includes the first
The internal combustion engine according to claim 2, which is means for selecting and determining the relative phase of the valve opening/closing timing to the engine low output side when the engine rotation speed exceeds a preset second engine rotation speed on the higher side than the engine rotation speed. Engine valve timing control device. (4) The engine operating state detection means includes a vehicle speed detection means, and the severe region valve timing determination means selects and determines the relative phase of valve opening/closing timing to the engine low output side when the vehicle speed exceeds a preset high speed side. A valve timing control device for an internal combustion engine according to claim 1 or 2, which is a means.