JPH0652051B2 - Valve timing control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control device for opening / closing timing (valve timing) of an intake valve and an exhaust valve of an internal combustion engine, and more particularly to protection means for a severe operating region.

<Prior Art> A device for variably controlling the opening / closing timing of intake / exhaust valves by changing the relative phases of the camshafts that lift the intake / exhaust valves open is disclosed, for example, in JP-B-52-35811. known.

This delays the closing timing of the exhaust valve and advances the opening timing of the intake valve as the engine speed increases, increasing the overlap amount of the opening timing of the intake valve and the exhaust valve.
This reduces the overlap amount of the intake / exhaust valve opening timing when the engine runs at low speed, prevents the backflow of the air taken into the combustion chamber, prevents the intake charging efficiency from decreasing, and prevents the deterioration of the exhaust property. Aim to improve fuel efficiency. On the other hand, when the engine is rotating at high speed, on the contrary, the overlap amount is increased to prevent delay of introduction of the intake air into the combustion chamber due to inertia,
By utilizing the inertial effect of exhaust gas, the filling efficiency is improved, and the fuel consumption, exhaust shape and output are improved.

However, according to the internal combustion engine having such a conventional valve timing control device, as described above, the output is always required to be improved regardless of the operating state of the engine. However, there is a risk that the engine, its exhaust system, and peripheral equipment may be damaged due to over-rotation in a high-speed rotation region, and that the vehicle speed may become too high during high-speed traveling.

In order to eliminate such inconvenience, JP-A-58-214628
There is also the No. No., but this one shuts off the fuel supply to the engine when the engine speed exceeds the set speed, so the intake air is supplied to the exhaust manifold and the catalyst device, which had been hot until then. Cold air that has just been discharged is allowed to flow, and a difference in expansion, which is a so-called heat shock, is generated in these, which causes a new problem of damage or damage.

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

<Means for Solving Problems> Therefore, in the present invention, as shown in the claim correspondence diagram of FIG. 1, a valve timing varying device for variably operating the opening / closing timing relative phase of the intake / exhaust valve, and the engine rotation speed. Engine rotation speed detection means for detecting, a predetermined engine rotation speed upper limit value, or a severe area detection means for detecting a severe area exceeding the vehicle speed upper limit value, and a severe area based on the detection signal of the severe area detection means Severe area determination means for determining, and a valve timing determination means for selectively determining the opening / closing timing relative phase of the intake / exhaust valve based on the engine rotation speed detected by the engine rotation speed detection means at times other than the severe area. Severe region valve timing determining means for selecting the opening / closing timing relative phase of the intake / exhaust valve to the engine low output side when it is determined to be in the severe region, and the valve timing of the two persons. Drive means for acting on the valve timing varying device based on the output of the ringing determination means to obtain a predetermined relative phase of opening / closing timing of the intake / exhaust valve.

<Operation> As a result, in normal engine operating conditions, the valve timing is variably controlled so as to improve the engine output, but once the engine enters a severe condition, the valve timing is controlled so as to decrease the engine output, and Prevents excessive output.

<Examples> Examples of the present invention will be described below with reference to the drawings.

In FIG. 2, a crank sprocket 3 is mounted on a crankshaft 2 which is an output shaft of a reciprocating internal combustion engine 1.
And the first cam sprocket 5 axially mounted on the overhead-type exhaust valve driving cam shaft 4, and the first timing belt 6 is wound around the loosened side of the spring 7 supported by the engine 1. The tensioner pulley 8 that has received the elastic force is pressed into contact with the tensioner pulley 8 to maintain the tension of the first timing belt 6 at an optimum value.

Here, the ratio of the diameters of the crank sprocket 3 and the first cam sprocket 5 is 1: 2, and the camshaft 4 is rotated at a rotation speed half that of the crankshaft 2.

The camshaft 4 further includes a first cam sprocket 5
The second cam sprocket 11 with a diameter sufficiently smaller than
A third cam sprocket 11 and a third sprocket 5 having the same diameter as the cam sprocket 5 axially mounted on a cam shaft 12 for driving an intake valve.
Second timing belt between cam sprocket 13 and
Multiply by 14. Here both cam sprockets 11, 13
Have the same diameter.

A pair of adjusting pulleys 15 and 16 are pressed into contact with the outer surfaces of the tension side a and the slack side b of the second timing belt 14.

The adjusting levers 17 and 18, which rotatably support the adjusting pulleys 15 and 16 at one end, respectively, are provided with a pin 17 on the engine 1.
It is rockably supported via a and 18a. A return spring 21 supported by the engine 1 is locked to the other end of one of the adjusting levers 17, and an arm 17b is also provided.
The output end of the step motor 23 is connected to the tip of the via a wire 22.

To the step motor 23, a control pulse signal of the control device 24 for inputting the detection signal output from the severe area detection means is input. Here, examples of the severe area detecting means include a crank angle sensor 25 for detecting the rotation speed of the crankshaft 2, a vehicle speed sensor 42 provided in a vehicle speedometer (speedometer) 41, and the like. In this embodiment, the step motor 23 is operated according to the engine speed, and the length of the tension side a of the timing belt 14 is controlled to increase or decrease based on the operation described later.

The adjusting lever 17 on the tension side is the connecting lever 26.
Through the adjustment lever 18 on the loose side. That is, one end of the connecting lever 26 is rotatably connected to the adjusting lever 17 between the pin 17a and the rotating shaft of the adjusting pulley 15, and the adjusting lever 18 is provided in the slit of a predetermined length provided at the other end of the connecting lever 26. The provided guide pin 28 is slidably inserted, and the tension spring 30 is interposed between the pin 28 and the pin 29 provided on the connecting lever 26.

The exhaust gas of the internal combustion engine 1 equipped with such a valve timing varying device is passed through the exhaust passage 31 and the turbine impeller of the supercharger 32.
33 is rotationally driven, and the compressor rotor 34, which is integrally coupled with this, is rotated. As a result, the intake air measured by the hot wire type air flow meter 35 is pressure-fed and supercharged, and is sucked into the engine by the metering action of the intake throttle valve 37 provided in the intake passage 36. The fuel injection valve 38 is controlled based on detection signals from various sensors such as the air flow meter 35 (or the throttle sensor 40 that detects the opening of the intake throttle valve), the crank angle sensor 25, the engine cooling water temperature sensor, and the starter switch. The device 24 controls the injection amount.

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

In the figure, the rotational speed detecting means 61 inputs the detection signal output from the crank angle sensor 25 to detect the engine rotational speed N.

The valve timing determination means 62 compares the detected engine rotation speed N with a preset first rotation speed N ₁ ,
As shown in FIG. 4, when N ≦ N ₁ , the valve timing is determined such that the intake valve advances the valve opening phase with respect to the exhaust valve, and when N> N ₁ , the valve opening timing is delayed.

The severe area determination means 63 uses the detected engine rotation speed N as a preset second rotation speed N ₂ (for example, 7,000 rpm> N).
If the value exceeds ₁ ), it is determined that the engine is over rotating. When this determination result is output, the severe area valve timing determination means 64 determines the valve timing that gives a low output.

The drive means 65 outputs a pulse signal in response to the output signals received from the two valve timing determination means 62, 64 to rotate the step motor 23 by a predetermined amount.

The control unit 24 is composed of a microcomputer including, for example, an input / output processing unit, a central processing unit, a storage unit and the like. Both valve timing determining means 62,
It is also possible to display 64 as a functional block as a single valve timing determining means in FIGS. 1 and 3.

The operation of the above configuration will be described with reference to the flowchart of FIG.

When the engine 1 is operated, the crankshaft 2 rotates, and the camshaft 4 for the exhaust valve rotates via the crank sprocket 3, the first timing belt 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 rotation speed of the latter is 1/2 that of the former.

The above rotation of the exhaust valve camshaft 4 causes the intake valve camshaft 12 to rotate via the second cam sprocket 11, the second timing belt 14, and the third cam sprocket 13. The rotation speeds of the camshafts 12 are equal because the two cam sprockets 11 and 13 have the same diameter.

Now, in step (S) 71 of the flowchart of FIG. 5, the engine speed N is read by the engine speed detection means 61 in response to the output signal from the crank angle sensor 25, and in step S72, the detected engine speed N is detected by the severe area determination means 63. And the second set rotation speed N ₂ are compared.

If N ≦ N _2, it is compared with the _first set rotational speed N ₁ in S73, and if N> N ₁ as a result,
In S75, the valve timing determining means 62 outputs a signal for retarding the intake valve to the driving means 65. As a result, the control signal is input to the step motor 23 to send out the wire 22. Therefore, the spring force of the return spring 21 swings the adjusting lever 17 around the pin 17a counterclockwise by a predetermined amount to loosen 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, the exhaust valve camshaft 4 sends the tension side a to the left in the figure for tension relaxation on the tension side a. As a result, the third cam sprocket 13 is rotated counterclockwise to the delay side by that amount, and the intake valve opening / closing timing is retarded as shown in FIG. As a result, the amount of overlap between the intake / exhaust valve opening timings is reduced, and the amount of intake air sent into the combustion chamber with a large boost pressure is reduced to the exhaust passage 31 or is prevented. As a result, the fuel is effectively used, the supercharging filling efficiency is improved, the output is increased, and the fuel consumption and the exhaust property are improved.

The length of the loosened side b becomes longer as the length of the second timing belt 14 on the tension side a becomes shorter. However, as the adjusting lever 17 rotates in the counterclockwise direction, the adjust lever 17 on the loose side b is moved through the connecting lever 26. 18 also rotates counterclockwise to move the adjusting pulley 16 upward in the figure to prevent the belt tension from being loosened on the loosening side b.

Here, the elastic force of the tension spring 30 balances the tension on the loosening side b of the timing belt 14 and maintains the tension at a predetermined value.

When the engine speed shifts from high speed to low speed, that is, S73
If it is determined that N ≦ N ₁ , the valve timing determination means 62 outputs a signal for switching the intake valve to the advance side in S74, the step motor 23 is operated via the drive means 65, and the wire 22 is pulled. .

As a result, the overlap amount of the intake / exhaust valve opening timing is increased as shown in FIG. The overlap amount at this time is matched to an optimum value in order to prevent backflow of air sucked into the combustion chamber, prevent deterioration of intake charging efficiency, prevent deterioration of exhaust gas properties, and improve fuel efficiency.

On the other hand, in S72, when the severe area determination means 63 detects that the rotational speed is excessive (N> N ₂ ), the severe area valve timing determination means 64 advances the opening / closing timing of the intake valve (S74),・ Increase the overlap of the exhaust valve opening timing. As a result, the supercharged air is blown into the exhaust port in the early stage of the intake stroke, the filling efficiency is reduced, and the engine output is reduced to prevent the engine rotation from becoming excessive. At this time, the exhaust energy is also reduced, so that the supercharger is prevented from over-rotating and the supercharging pressure is prevented from becoming excessively large, so that the intake system and the engine can be protected.

The above valve timing control characteristics are shown in FIG.

The engine speed detecting means may be a combination of the vehicle speed and the gear position of the transmission, in addition to the crank angle sensor as in the embodiment.

Further, in the above embodiment, the example in which the present invention is applied to the internal combustion engine with a supercharger has been described. However, when the present invention is applied to a normal internal combustion engine without a supercharger, it is necessary to control the amount of overlap of the intake / exhaust valves by controlling the valve timing, which is the reverse of the control with the supercharger. . That is, N <N
_In the case of ₁ , the valve overlap amount is reduced to prevent backflow of the intake air and the inertia is effectively used to increase the intake charging efficiency. In the case of N ₂ > N ≧ N ₁ , the valve overlap amount is increased. By preventing the delay due to the inertia of the intake air introduction, the intake charging efficiency is increased and the output is improved.

When N ≧ N _2, the valve overlap amount is made small again, that is, the intake valve opening timing is delayed to cause the introduction delay due to the inertia of the intake, thereby reducing the filling efficiency and reducing the output to reduce the engine output. Prevents excessive rotation.

In addition to the winding transmission device, the variable valve timing device may be provided with a variable device in the hydraulic tappet or other valve mechanism itself. In this case, a solenoid valve or the like is used as the drive mechanism instead of the step motor 23. Is common. The variable control of the valve timing may be a continuously variable type instead of the two-stage control type as in the embodiment. Depending on the purpose, either of the camshafts 4 and 12 may be used for the intake valve or the exhaust valve, and the variable control of the relative phase of both camshafts may change the phase of either camshaft or both phases. Obviously, you can change

FIG. 7 shows another embodiment of the present invention. In the above-mentioned embodiment, the severe condition of the engine is taken as an example when the rotation speed is N ₂ or more. However, in this embodiment, the vehicle speed V is the limited vehicle speed V ₁ for example 180 km / h.
Take the case of as an example.

That is, in FIG. 7, the vehicle speed V signal input from the vehicle speed sensor 42 via the vehicle speed detecting means 67 to the severe area determining means 63a is compared with the preset vehicle speed V ₁ (S72 in FIG. 8).
a) When V> V ₁ , the valve timing of the intake valve is advanced by the severe region valve timing determining means 64 in S74 (in the case of an internal combustion engine with a supercharger). As a result, the engine output is reduced, and the vehicle speed is prevented from rising too fast during high-speed traveling. The other points are the same as those in the above-mentioned embodiment, and therefore the description thereof is omitted.

Incidentally, in order to detect the vehicle speed, other than the embodiment, the rotation speed of the transmission output shaft may be detected, or a combination of the engine rotation speed and the gear position of the transmission may be used.

As described above, the severe condition of the engine is determined by the engine speed and the vehicle speed.

<Advantages of the Invention> As described above, according to the present invention, the valve timings of the intake and exhaust valves are controlled to secure the output in the normal operation region, but once the engine enters the severe condition, the output is reduced. Since the valve timing is controlled, it is possible to prevent the engine from excessively rotating and the vehicle speed from rising too fast under severe conditions.

In addition, since the fuel is not shut off even under severe conditions, the shock of the engine is not large, and since cold air does not flow to the exhaust manifold and catalyst that were at high temperatures, damage or damage is prevented without these heat shocks. it can.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a configuration diagram showing a first embodiment of the present invention, FIG. 3 is a block diagram showing a functional configuration of a control device of the same, and FIG. FIG. 5 is a graph showing the intake / exhaust valve timing control characteristic of the embodiment, FIG. 5 is a flowchart showing the operation of the control device in FIG. 3, and FIG. 6 is a torque characteristic diagram based on the valve timing control of the first embodiment. FIG. 8 is a block diagram of a control device showing a second embodiment of the present invention, and FIG. 8 is a flow chart showing the operation of the same. 1 ... Reciprocating internal combustion engine, 11 ... Second cam sprocket, 13 ... Third cam sprocket, 14 ... Second timing belt, 17, 18 ... Adjust lever, 22 ... Wire, 23 ...... Step motor, 24 ...... Control device, 25 ……
Crank angle sensor, 26 ...... connecting lever, 42 ...
… Vehicle speed sensor, 62,64 …… Valve timing determination means,
63, 63a ... Severe area determination means, 65 ... driving means

Claims (1)

[Claims] 1. A valve timing varying device for variably operating an opening / closing timing relative phase of intake / exhaust valves, an engine speed detecting means for detecting an engine speed, and a predetermined engine speed upper limit value or vehicle speed upper limit value. Severe area detecting means for detecting a severe area exceeding, a severe area determining means for judging a severe area based on a detection signal of the severe area detecting means, and a engine speed detecting means other than the severe area, Valve timing determining means for selectively determining the opening / closing timing relative phase of the intake / exhaust valve based on the detected engine rotation speed, and the engine opening / closing timing relative phase of the intake / exhaust valve when it is determined to be in the severe region. Side valve timing determining means to be selected on the side, and the valve timing varying device acting on the valve timing varying device based on the outputs of the two valve timing determining means. The valve timing control apparatus for an internal combustion engine, characterized by comprising drive means for obtaining an opening and closing timing relative phase of the exhaust valve, the.