JP4410462B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve operating apparatus for an internal combustion engine, and more particularly to a technique for changing the valve opening (valve lift) of an intake valve in accordance with the operating state of the internal combustion engine.
[0002]
[Related background]
In an internal combustion engine, for example, a gasoline engine, the intake valve is opened because the intake air amount is controlled by a throttle valve provided in the intake passage and the opening amount (valve lift) of the intake valve is limited. When intake is performed, the combustion chamber has a negative pressure and a large pumping loss occurs. This problem becomes more prominent as the engine speed increases.
[0003]
Patent Document 1 below discloses that the valve lift amount is reduced at a low speed and a low load range, and the valve lift amount is increased at a high speed and a high load.
Recently, a technology for adjusting the intake air intake amount by changing the opening of the intake valve by eliminating the throttle valve has been developed, and this has significantly reduced the pumping loss.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-107725
[Problems to be solved by the invention]
By the way, when the degree of opening of the intake valve is changed as in Patent Document 1, the valve lift of the intake valve is set to be small or the valve opening period is set to be short at the time of low engine speed. In order to reduce the pressure as much as possible, the valve lift of the intake valve should be set as large as possible. To achieve this, the valve lift curve at the time of maximum valve lift of the intake valve is increased so that the valve lift curve at the time of maximum valve lift is steep. It is better to set the acceleration higher.
[0006]
However, increasing the valve lift acceleration increases the load on each part of the valve operating system at high speeds. Generally, the valve lift is maximized at the engine rotation speed at which the engine exhibits the maximum output in order to ensure the output performance. In other words, since the intake valve is variably controlled so that the valve lift acceleration reaches the maximum, if the engine rotation speed exceeds the maximum output engine rotation speed, the valve lift acceleration becomes extremely large. There is a problem that such a load becomes excessive.
[0007]
If the load applied to each part of the valve operating apparatus becomes excessive in this way, the engine is deteriorated earlier and the durability is deteriorated, which is not preferable.
The present invention has been made to solve these problems, and the object of the present invention is to enable an internal combustion engine that can secure output performance while ensuring sufficient durability while reducing pumping loss. The object is to provide a variable valve device.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the variable valve operating apparatus for an internal combustion engine according to claim 1, an intake valve for communicating and blocking air flowing into the combustion chamber, and a communication and blocking for exhaust discharged from the combustion chamber. In a variable valve operating apparatus for an internal combustion engine capable of adjusting the intake air amount by variably controlling at least the valve opening amount of the intake valve, the intake valve is driven by rotation of a crankshaft, and the intake valve is operated during an intake stroke. A cam for opening and closing the valve; and a valve opening amount changing means for changing a valve opening amount of the intake valve by the cam according to an operating state of the internal combustion engine, wherein the valve opening amount changing means is an output of the internal combustion engine. The valve opening amount of the intake valve is increased in response to the increase, and the valve opening amount is maximized when the engine rotational speed reaches the maximum output engine rotational speed. When the engine rotational speed exceeds the maximum output engine rotational speed, the valve Reduce lift acceleration It is characterized in that to gradually reduce the valve opening amount according to Ku rise of the engine speed.
[0009]
That is, the valve opening amount changing means increases the opening amount of the intake valve in response to the increase in the rotation of the internal combustion engine in the full load state, but opens when the engine speed reaches the maximum output engine speed. When the valve amount is maximized and the engine rotational speed exceeds the maximum output engine rotational speed, the valve opening amount is gradually decreased.
Therefore, the valve opening amount (valve lift) can be maximized at the maximum output engine speed to ensure the output performance, and the valve opening amount (valve lift) can be gradually decreased in the region above the maximum output engine speed. Thus, an excessive load applied to each part of the valve gear is prevented, and the durability of the internal combustion engine is ensured.
[0010]
Further, in the variable valve operating apparatus for an internal combustion engine according to claim 2, the cam is a swing cam that periodically swings by rotation of a crankshaft to open and close the intake valve, and the valve opening amount change The means is characterized in that the valve opening amount of the intake valve is changed by changing the position of the swing fulcrum of the swing cam according to the operating state of the internal combustion engine.
Therefore, the valve opening amount (valve lift) of the intake valve can be easily and reliably changed with a simple configuration.
[0011]
Preferably , the cam profile is set so that the valve opening amount becomes large from the initial valve opening stage of the intake valve.
As a result , the valve opening amount (valve lift) of the intake valve is increased from the beginning of valve opening, and therefore the intake air amount is increased, and the pumping loss is further reduced and the output performance is further improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of a variable valve operating apparatus for an internal combustion engine according to the present invention mounted on a vehicle. Hereinafter, the configuration of the variable valve operating apparatus according to the present invention will be described with reference to FIG. To do.
[0013]
As the engine (internal combustion engine), a spark ignition gasoline engine is adopted, and a piston 12 is fitted in the cylinder 10 of each cylinder.
In the cylinder head of the engine, an intake valve 15 that communicates and shuts off the combustion chamber 13 and the intake port 14 and an exhaust valve 17 that communicates and shuts off the combustion chamber 13 and the exhaust port 16 are provided for each cylinder. The intake valve 15 and the exhaust valve 17 are opened and closed by a valve operating device 20.
[0014]
As shown in the figure, when the camshaft 22 and the camshaft 26 rotate in synchronization with engine rotation, the valve gear 20 presses the head of the intake valve 15 with the cam 24 formed on the camshaft 22. Thus, the intake valve 15 is opened and closed, and the cam 28 formed on the camshaft 26 presses the head of the exhaust valve 17 to open and close the exhaust valve 17.
[0015]
Specifically, a rocker arm 30 and a swing cam 40 are interposed between the intake valve 15 and the camshaft 22, and when the camshaft 22 rotates, the valve gear 20 rotates the cam 24 with a roller 44. The rocking cam surface 42 of the rocking cam 40 is swung around the rocking fulcrum 41 via the roller, and the rocking cam surface 42 rocks the rocker arm 30 around the fulcrum 31 via the roller 32, thereby The intake valve 15 is opened and closed by pressing the head of the valve 15.
[0016]
Further, a roller 45 is fitted around the swing fulcrum 41 of the swing cam 40, and an eccentric roller unit (valve opening changing means) 50 is provided so that the roller 45 and the eccentric roller 52 come into contact with each other. It has been. The eccentric roller unit 50 is provided with an eccentric roller 52 that is eccentric about the shaft 54, and the shaft 54 is configured to be rotatable by a step motor 60 via a worm gear 62. That is, in the eccentric roller unit 50, when the worm gear 62 is rotated by the step motor 60, the eccentric roller 52 rotates together with the shaft 54, and the eccentric roller 52 presses the roller 45 of the swing cam 40 to bias the swing support point 41. It is configured to let you.
[0017]
When the swing fulcrum 41 is biased, the contact state between the swing cam surface 42 of the swing cam 40 and the roller 32 of the rocker arm 30 changes, and the degree of pressing of the head of the intake valve 15 changes. As a result, the valve lift (opening amount) of the intake valve 15 changes.
The cylinder head is provided with a spark plug 70 facing the combustion chamber 13, and the spark plug 70 is connected to the ignition coil 72.
[0018]
In addition, an ECU (electronic control unit) 80 including an input / output device, a storage device (ROM, RAM, etc.), a CPU, and the like is provided, and the ECU 80 provides comprehensive control of the variable valve operating device including the engine. Is done.
Various sensors such as a crank angle sensor 82 are connected to the input side of the ECU 80, and detection information from these sensors is input. The engine speed Ne is calculated based on the crank angle information from the crank angle sensor 82.
[0019]
On the other hand, various output devices such as the above-described step motor 60 and ignition coil 72 are connected to the output side of the ECU 80.
Hereinafter, an operation of the variable valve operating apparatus configured as described above will be described.
In the variable valve operating apparatus according to the present invention, the intake air amount is adjusted by the intake valve 15 instead of the throttle valve, thereby reducing the pumping loss particularly at a low load. That is, in the variable valve operating apparatus, when the engine output is small at a low load and the engine speed Ne is low, the valve lift is set small, and the step motor 60 is operated and eccentric as the engine output, that is, the engine speed Ne increases. The roller unit 50 is moved to increase the valve lift. That is, referring to FIG. 2, the valve lift (a) at the time of high output and the valve lift (b) at the time of low output are shown. The valve lift is increased to increase the intake air amount at high output, and the valve lift is maximized at the maximum output of the engine.
[0020]
Further, in the variable valve operating apparatus, the cam profile of the swing cam surface 42 of the swing cam 40 is set so that the intake air amount becomes as much as possible from the initial opening of the intake valve 15. That is, in FIG. 2, the valve lift in the case of a general cam profile is also indicated by a broken line, but in the variable valve operating apparatus, the swing cam surface so that the valve lift curve of the intake valve 15 is thick. 42 cam profiles are set. That is, referring to FIG. 2 (a), the valve lift acceleration is also indicated by a one-dot chain line, but in this way, the intake valve 15 is set so that the valve lift acceleration is relatively large from the beginning of valve opening. ing.
[0021]
As a result, as shown in FIG. 2A, the valve lift at the time of high output is increased as a whole, the intake air amount is increased, and the output performance of the engine is improved. Further, as shown in FIG. 2B, the valve lift amount is increased even during the low lift control, and the pumping loss is further reduced.
By the way, when the cam profile of the swing cam surface 42 is set so that the valve lift curve of the intake valve 15 is thick and the valve lift acceleration is increased so that the intake air amount is increased as much as possible, Since the load increases as the engine speed Ne increases, the load continues to increase even after the engine output reaches the maximum output, that is, after the engine speed Ne exceeds the maximum output engine speed Ne1. Therefore, there is a possibility that the load applied to each part of the valve gear becomes extremely large.
[0022]
Therefore, in the valve gear according to the present invention, after the engine output reaches the maximum output, that is, after the engine rotational speed Ne exceeds the maximum output engine rotational speed Ne1, the eccentric roller unit 50 is reversed to perform the valve lift. The valve lift acceleration is decreased so as to be gradually decreased. That is, referring to FIG. 3, the relationship between the engine speed Ne and the engine output is shown. As shown in FIG. 3, after the engine speed Ne exceeds the maximum output engine speed Ne1, the valve The lift is gradually reduced to reduce the intake air intake amount, and the engine output is reduced as shown by the dotted line. It should be noted that after the engine speed Ne reaches the maximum output engine speed Ne1, there is no problem even if the engine output decreases because the engine is not in the normal rotation range (so-called red zone).
[0023]
Thereby, it is prevented that the load concerning each part of a valve operating apparatus becomes very large, and durability of an engine is ensured.
Thus, in the valve gear of the present invention, the intake air amount is adjusted by the intake valve 15, the valve lift curve of the intake valve 15 is increased to increase the intake air amount as a whole, and the maximum output is achieved. At this time, the valve lift is maximized, and the valve lift is gradually decreased after the engine rotational speed Ne exceeds the maximum output engine rotational speed Ne1.
[0024]
Accordingly, the pumping loss is reduced and the engine output performance is secured, and further increase of the valve lift acceleration after the engine rotational speed Ne exceeds the maximum output engine rotational speed Ne1 is prevented. This excessive load can be prevented, and the durability of the engine can be ensured.
The description of the embodiment is finished as above, but the present invention is not limited to the above embodiment.
[0025]
For example, in the above-described embodiment, the case where the swing fulcrum 41 of the swing cam 40 is biased as an example of the valve opening amount change means has been described. However, the valve opening amount change means is not limited to this, and the swing cam 40 The present invention can be sufficiently applied even to a general system that changes the amount of rocking or the range of rocking, or a rotating cam.
[0026]
【The invention's effect】
As described above in detail, according to the variable valve operating apparatus for an internal combustion engine according to claim 1 of the present invention, the valve opening amount of the intake valve is increased in accordance with an increase in the output of the internal combustion engine, so that it exceeds the maximum output engine speed. In this area, the valve opening amount (valve lift) is gradually decreased as the engine speed increases to reduce the valve lift acceleration, so that the pumping loss is reduced and the output performance is secured while ensuring the output performance. Further increase in the load applied to each part of the valve device can be prevented, and the durability of the internal combustion engine can be ensured.
[0027]
Further, according to the variable valve operating apparatus for an internal combustion engine of claim 2, since the opening amount of the intake valve is changed by changing the position of the swing fulcrum of the swing cam, The valve opening amount (valve lift) of the valve can be easily changed with certainty .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a variable valve operating apparatus for an internal combustion engine according to the present invention mounted on a vehicle.
FIG. 2 is a diagram showing a valve lift (a) at high output and a valve lift (b) at low output.
FIG. 3 is a diagram showing a relationship between an engine rotation speed Ne and an engine output, and is a diagram for explaining the operational effects of the present invention.
[Explanation of symbols]
15 Intake valve 20 Valve operating device 30 Rocker arm 40 Oscillating cam 41 Oscillating fulcrum 42 Oscillating cam surface 50 Eccentric roller unit (valve opening amount changing means)
80 ECU (Electronic Control Unit)
82 Crank angle sensor

Claims (2)

An intake valve for communicating and blocking air flowing into the combustion chamber; and an exhaust valve for communicating and blocking exhaust discharged from the combustion chamber, and at least the intake valve opening amount is variably controlled. In a variable valve operating apparatus for an internal combustion engine capable of adjusting the amount of air,
A cam that is driven by rotation of the crankshaft to open and close the intake valve in the intake stroke;
Opening amount changing means for changing the opening amount of the intake valve by the cam according to the operating state of the internal combustion engine,
The valve opening amount changing means increases the valve opening amount of the intake valve in response to an increase in the output of the internal combustion engine, and maximizes the valve opening amount when the engine rotational speed reaches the maximum output engine rotational speed. A variable valve operating system for an internal combustion engine, wherein when the speed exceeds the maximum output engine speed , the valve opening amount is gradually decreased in accordance with an increase in the engine speed so as to reduce valve lift acceleration . The cam is a swing cam that swings periodically by rotation of a crankshaft to open and close the intake valve,
The valve opening amount changing means changes the valve opening amount of the intake valve by changing a position of a swing fulcrum of the swing cam according to an operating state of the internal combustion engine. A variable valve operating apparatus for an internal combustion engine as described.

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