JPH10176506A - Camshaft structure of internal combustion engine - Google Patents

Abstract

(57) Abstract: A camshaft structure for an internal combustion engine, wherein vibration caused by an increase in load on a timing belt and torsion of a camshaft in a valve mechanism of an engine valve of the internal combustion engine is attached to an end of the camshaft. In addition to the damping by the dynamic damper, the life of the timing belt is improved. A dynamic damper (12) capable of suppressing vibration caused by torsion of a camshaft (3) of an internal combustion engine (1) and an increase in load on a timing belt (9) caused by an increase in acceleration of an engine valve of the internal combustion engine (1). Are provided in the dead space (dead space) D of the internal combustion engine 1 without changing the layout of the internal combustion engine 1 so that the detection accuracy of the cam sensor 13 for determining the cylinder can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft structure for an internal combustion engine, in which a dynamic damper is provided on the camshaft to attenuate vibration caused by torsion of the camshaft in a valve mechanism for an intake and exhaust valve of an internal combustion engine. ,
In particular, the present invention relates to a camshaft structure of an internal combustion engine having a camshaft provided with a cam sensor.

[0002]

2. Description of the Related Art In an internal combustion engine, an engine valve such as an intake / exhaust valve is driven to open and close in accordance with the rotation of a crankshaft. Therefore, as is well known, a conventional internal combustion engine is provided between a crankshaft and a camshaft. In order to transmit the rotation, a rotation transmission mechanism such as a timing belt drive system or a chain drive system is used.

In recent years, in internal combustion engines aiming at high output, it has been considered to increase the valve lift, valve opening time, and valve opening area of the engine valve as a technique for improving the volumetric efficiency. When the above method is performed, the acceleration of the engine valve increases, and depending on how the valve timing is set, resonance occurs in the cam drive system, so that the cam drive torque amplitude increases.

[0004] The cam drive torque amplitude is related to the camshaft rotation fluctuation and is proportional to the load of a timing belt or a timing gear chain (hereinafter simply referred to as a timing belt). That is, when the cam drive torque amplitude increases, for example, as shown in FIG. 6, the load on the timing belt increases with respect to the rotation speed of the internal combustion engine (engine rotation speed), especially around the resonance point. The durability of the belt becomes a problem.

[0005] Incidentally, it is considered that the rotation fluctuation of the camshaft due to the increase in the load is caused by vibration caused by torsion of the camshaft. Various proposals have been made to prevent the occurrence of such vibrations caused by torsion, for example, Japanese Patent Application Laid-Open Nos. 2-218805, 6-23684, and 59-73643. There is a gazette.

The vibration caused by the camshaft torsion is described in, for example, Japanese Patent Application Laid-Open No. 59-73643, and will be described with reference to FIGS. As shown in FIG. 7, the valve operating mechanism of the engine valve, which is an intake / exhaust valve of the internal combustion engine 02, has a combustion chamber 0 in the cylinder head 04.
6 is a mechanism for opening and closing an engine valve 010 disposed at an opening of the camshaft 012 so as to communicate with and block the intake hole (or exhaust hole) 08. And a rocker arm 018 pivotally supported so as to swing around a support shaft 016 by a periodic contact relationship with the cam 014. The end portion 019 of the rocker arm 018 as shown in FIG. The stem 022 of the engine valve 010 against the urging force of the valve spring 020
The engine valve 010 is opened and closed by periodically pushing down the upper end.

The stem 022 of the engine valve 010 is penetrated by the valve guide 024. A spring retainer 026 is provided at the rear of the stem 022. The stem 022 is elastically supported in the valve closing direction by a valve spring 020 abutting on the spring retainer 026. Further, such a valve operating mechanism is provided in a cylinder head cover 028 fixed on the cylinder head 04.

With such a configuration, the camshaft 01
When the cam 014 attempts to push up the rocker arm 018 by rotating the cam 2, a force for stopping the rotation acts on the tip of the cam 014 via the rocker arm 018 in accordance with the urging force of the valve spring 020. On the other hand, as shown in FIG. 8, a crankshaft sprocket 03 fixed to one end of a camshaft 014, for example, to a camshaft sprocket 030 by a timing belt 032 or the like is fixed to one end of a crankshaft 034.
6, a rotational difference is generated between the cam 014 and the camshaft sprocket 030, and the camshaft 012 between them is twisted. Then, after the cam 014 pushes up the rocker arm 018, a restoring force is generated corresponding to the torsion.

In this way, every time the cam 014 acts on the rocker arm 018, the torsion and its restoring force are repeated between the cam 014 and the camshaft sprocket 030, and the camshaft 018 is twisted. Vibration will occur. When the above-described vibration or the fluctuation of the camshaft rotation caused by the increase in the cam drive torque amplitude of the internal combustion engine aiming at high output is frequency-matched with the natural vibration of the camshaft 012 itself, further resonance occurs and the torsion is caused. A situation arises in which the vibration caused by the vibration is further increased.

[0010] When the vibration caused by the above-mentioned torsion occurs, the timing belt 03 between the camshaft sprocket 030 and the crankshaft sprocket 036 is generated.
The tensile force is repeatedly applied to the second belt 2 and the like, which causes an abnormal load on the timing belt 032 and the like, which is not preferable. Therefore, in order to remove the abnormal load as described above, measures must be taken to prevent the occurrence of the vibration in the camshaft 012, and various proposals as described above have been made.

The technique described in the above-mentioned Japanese Patent Application Laid-Open No. 2-218805 discloses a valve in which a dynamic damper for preventing occurrence of resonance is mounted near an end of a camshaft in a valve train in the vicinity of an end of a camshaft. This is a train damper device, and the occurrence of resonance of the camshaft can be stopped or reduced by the spring force or viscous resistance of the damper elastic body and the inertia force of the damper weight, so that the occurrence of chatter vibration of the hydraulic lift and And the occurrence of abnormal noise.

The technique described in Japanese Utility Model Publication No. 6-23684 discloses a crankshaft sprocket fixed to a crankshaft and a camshaft sprocket fixed to one end of a camshaft connected by a timing belt. In the internal combustion engine that transmits the rotational motion of the shaft to the camshaft, at the other end of the camshaft without the camshaft sprocket,
A dynamic damper for suppressing vibration caused by torsion of the camshaft is provided to effectively suppress the vibration.

The technique described in Japanese Patent Application Laid-Open No. 59-73643 discloses a technique in which a crankshaft sprocket and a camshaft sprocket fixed to one end of a camshaft are connected by a timing belt, and the rotational motion of the crankshaft is controlled by the above-described method. In an internal combustion engine for transmitting a force to a camshaft, a weight unit having an annular weight and an annular weight disposed around an outer periphery of the camshaft via an elastic coupling body is attached to an end of the camshaft.

[0014]

In an internal combustion engine, in addition to a crank angle sensor for detecting a crank angle, a sensor provided on a camshaft for cylinder discrimination (a sensor installed on this camshaft) Is called a cam sensor). Considering the installation of such a cam sensor, as shown in FIG. 8, since there is no space for the sprocket of the camshaft, it becomes an issue to which part of the camshaft to install.

A double camshaft having two camshafts
In the case of an overhead camshaft (DOHC), as shown in FIG. 9, sprockets 030A and 030B provided at the end of each camshaft are connected to a timing belt 0.
32 receives the rotational force of the crankshaft sprocket 036, but on the tension side of the crankshaft 034 (in FIG. 9, the upper right side of the crankshaft sprocket 036).
The camshaft sprocket 030B rotates with high precision, but the camshaft sprocket 030 on the loose side (the upper left side of the crankshaft sprocket 036 in FIG. 9).
In A, although the tension is adjusted by the tensioner 038, the rotation accuracy is lower than that of the tension side.

Therefore, in the case of such a DOHC type internal combustion engine, if the accuracy of the cam sensor is ensured and the space in which the cam sensor can be installed is taken into consideration, the more accurate camshaft on the tension side of the timing belt is provided without the sprocket. It is conceivable that the cam sensor extends to the rear side wall of the cylinder head on the opposite side (the other end side) and is disposed outside the rear wall of the cylinder head at the other end of the camshaft.

However, none of the techniques described in the above three publications takes into account the existence of the above-described sensor for detecting the crank angle. Merely describes the installation of a dynamic damper. Therefore, in this technique, it is possible to secure the installation space for the sensor for detecting the above-described cylinder discrimination signal, secure the detection accuracy, and effectively achieve the suppression of the vibration caused by the torsion of the camshaft. In addition, the above-mentioned dynamic damper and sensor cannot be arranged compactly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an efficient installation structure. The vibration is caused by the torsion of the camshaft of the internal combustion engine and the acceleration of the engine valve of the internal combustion engine is increased. It is an object of the present invention to provide a camshaft structure for an internal combustion engine, which can suppress an increase in the load on a timing belt and can accurately perform cylinder discrimination.

[0019]

According to the present invention, there is provided a camshaft structure for an internal combustion engine according to the first aspect of the present invention, wherein two camshafts are installed in pairs on a cylinder head to drive an engine valve of the internal combustion engine. A camshaft, a sprocket provided at one end of each of the camshafts, a timing belt wound around a sprocket provided at one end of a crankshaft of the internal combustion engine, and the two camshafts And a cam sensor provided at the other end of the pulling camshaft located on the pulling side of the timing belt, wherein a dynamic damper is mounted inside the cam sensor of the pulling camshaft. Features.

According to a second aspect of the present invention, there is provided a camshaft for an internal combustion engine, comprising: two camshafts installed in pairs on a cylinder head for driving engine valves of the internal combustion engine; A sprocket mounted at one end of a shaft, a timing belt wound around a sprocket mounted at one end of a crankshaft of the internal combustion engine, and a tension side of the timing belt of the two camshafts And a cam sensor installed at the other end of the pulling side camshaft, and a dynamic damper is mounted on a sprocket mounted on the pulling side camshaft.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic plan view showing the internal combustion engine viewed from the top of a cylinder head, showing a partly broken cross section. FIG. .

As shown in FIG. 1, an internal combustion engine (hereinafter, also referred to as an engine) 1 has four cylinders (not shown) and a double overhead camshaft (DOHC) having two camshafts. Each of the cylinders is provided with a pair of intake valves and exhaust valves, which are engine valves (not shown). The valve mechanism 5 for opening and closing the engine valve includes a pair of camshafts 3 and 4.
A rocker arm indicated by a two-dot chain line that slides on the cams 3a, 4b to open and close the intake valve and the exhaust valve. 5a and 5b.

The camshaft sprockets 7, 8 are fixed to one end of the camshafts 3, 4 by bolts 15a. As shown in FIG. 2, the camshaft sprockets 7, 8 include a timing belt (or a belt driven by a timing gear chain, both of which are collectively referred to as a timing belt) 9. The crankshaft 10 is connected to a crankshaft sprocket 11 provided at one end of the camshaft 10, and the rotational motion of the crankshaft 10 is transmitted to the respective camshafts 3 and 4, and the camshafts 3 and 4 rotate according to the angle of the crankshaft 10. It is configured as follows.

Since the camshaft 3 on the pulling side of the timing belt 9 among the camshafts 3 and 4 is constantly pulled, the camshaft 3 on the feed side (loose side) is more connected to the crankshaft 10 than the camshaft 4 on the feed side (loose side). On the other hand, it is rotating accurately. By the way, in order to determine the timing of ignition timing, fuel injection timing, fuel injection amount, etc., it is necessary to detect the crank angle and the cylinder discrimination in order to detect the crank angle. , By a cam sensor installed on the camshaft.

Since such a cam sensor is required to have higher detection accuracy, as shown in FIG. 1, the cam sensor 13 is attached to the tension side cam shaft 3 of the timing belt 9 which rotates relatively accurately. Have been. Further, since there is no space on the camshaft sprocket 7 side due to the camshaft 3, the other end of the camshaft 3 is extended to the rear side wall 2a of the cylinder head 2, and a cam sensor 13 is provided on the extended end side. .

The cam sensor 13 is conventionally used in general. The cam sensor 13 includes a sensing cylinder 13a having a notch, and a detector 13b in which a light emitting diode and a photodiode (not shown) are incorporated. The detector 13b is attached to the outside of the rear side wall 2a of the cylinder head 2 by bolts 15b, and the cam sensing cylinder 13a is attached to the other end of the camshaft 3 by bolts 15b.

The detection unit 13b detects the passage of the notch of the cam sensing cylinder 13a, which rotates with the rotation of the camshaft 3, as an angle corresponding to the crank angle. Input to the device. A dynamic damper 12 is installed on the camshafts 3 and 4 of the engine. The dynamic damper 12 will be described.

As shown in FIG. 1, the dynamic damper 12 is attached to the camshaft 3, and in particular, is installed inside the extended end of the camshaft 3 where the cam sensor 13 is attached. I have. That is, the camshaft 3 is provided at its end with a journal 3j supported by the bearing 2b of the rear side wall 2a of the cylinder head 2, and a portion adjacent to the journal 3j is larger than the outer diameter of the journal 3j. The enlarged diameter portion 3b is formed,
The dynamic damper 12 is mounted on the enlarged diameter portion 3b.

Further, the dynamic damper 12 is provided with the enlarged diameter portion 3.
b, an inner cylinder 12a having a diameter larger than the outer diameter of the journal 3j, and an elastic member 12b made of an annular rubber, a synthetic resin or the like attached to the outer periphery of the inner cylinder 12a.
And an outer annular weight 12c formed of a weight ring made of iron or the like fixed to the outer periphery of the elastic member 12b.

The dynamic damper 12 configured as described above is inserted from the end of the cam sensor 3 on the mounting side of the cam sensor 13 so as to pass through the journal 3j.
The outermost cam 3a (closer to the end provided with the cam sensor 13) provided on the camshaft 3 and the cam sensor 13
And a large-diameter portion 3b provided in a dead space (dead space) in the cylinder head 2.

The camshaft 3 to which the dynamic damper 12 is attached is disposed on the cylinder head 2 and is supported by a well-known bearing cap (not shown). Thereafter, as described above, the cam sensor 13 is attached by the bolt 15b as shown in FIG.

In FIG. 2, reference numeral 20 denotes a tension pulley, 21 denotes a tensioner, 22 and 24 denote idle pulleys, and 25 denotes sprockets 7, 8, 11 and pulleys 20,
This is a rotation transmission mechanism including the rotation belts 22, 24 and the timing belt 9. Since the camshaft structure of the internal combustion engine as the first embodiment of the present invention is configured as described above, the rotational movement of the crankshaft 10 is controlled by the rotation transmitting mechanism 2.
5 are transmitted to the camshafts 3 and 4 via the camshaft sprockets 7 and 8, the timing belt 9, the crankshaft sprocket 11, the tension pulley 20 and the idle pulleys 22 and 24. The engine valves are driven to rotate, and the engine valves are opened and closed by the cams 3a and 4a and the rocker arms 5a and 5b, respectively.

Therefore, during rotation of the engine, the vibration caused by the torsion generated in the camshaft 4 can be reduced by being absorbed by the annular weight 12c of the dynamic damper 12, and as shown in FIG. Even if the cam drive torque amplitude increases due to the high rotation of the motor and the load on the timing belt increases due to this, as shown in the characteristics of the engine speed and the belt load in FIG. 4, an increase in load near the resonance point can be greatly reduced.

At the same time, by providing the cam sensor 13 on the tension side camshaft 3 which rotates with higher precision, the cam sensor 13 can also detect the crank angle with high accuracy. The ignition timing, the fuel injection timing, and the fuel injection amount can be accurately performed to improve the performance of the internal combustion engine. Further, since the dynamic damper 12 is disposed in the dead space (dead space) D of the cylinder head 2 corresponding to the space between the cam 3a and the cam sensor 13, the overall shape of the internal combustion engine can be made compact. it can.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 3 is a schematic plan view similar to FIG. 1 as viewed from the top of the cylinder head of the internal combustion engine, FIG. 4 is a diagram showing a timing belt system relating to the valve mechanism in FIG. 3, and FIG. Arrow view,
4B is a schematic cross-sectional view showing a cross section of a main part along line 4B-4B in FIG. 4A, and the same parts as those in the first embodiment shown in FIGS. The description is given with reference numerals.

In the first embodiment, the dynamic damper 12 is attached to the camshaft 3 between the outermost cam 3a near the rear end of the pulling-side camshaft 3 and the cam sensor 13. In the present embodiment, as shown in FIGS. 3 and 4, the dynamic damper 12
A bolt 15 is attached to one end of the sprocket 7 at the front end of the camshaft 3 via the boss 12d of the dynamic damper 12.
a.

In particular, the dynamic damper 12 is provided in the boss 7a of the sprocket 7 so as to be rotatable and partially overlap the sprocket 7. The cam sensor 13 is installed in the same manner as in the first embodiment. With such a configuration, vibration caused by torsion generated in the camshaft 4 during rotation of the engine can be absorbed and reduced by the annular weight 12c of the dynamic damper 12, and the like.

The dynamic damper 12 is a dead space (dead space) D in the boss 7a of the sprocket 7.
The camshaft 3 is provided so as to be partially overlapped coaxially with the camshaft 3 without increasing the length of the camshaft 3.
Can be provided compactly while maintaining the length of the first embodiment, so that substantially the same operational effects as in the first embodiment can be achieved.

At the end of the camshaft 3, the dynamic damper 12 can be easily mounted. Further, in each of the embodiments of the present invention, the valve operating mechanism using the timing belt and the sprocket has been described. However, the present invention is not limited to this, and the present invention can be applied to a valve operating mechanism using the timing gear chain and the sprocket. Accordingly, while the cam sensor 13 and the dynamic damper 12 are efficiently installed in space, each function can be more effectively exhibited, and the vibration or the like generated on the camshaft during the rotation described above is reliably suppressed. As a result, the service life of the timing belt and the chain is improved, and the operation noise is also reduced.

[0040]

As described above in detail, according to the camshaft structure of the internal combustion engine according to the first aspect of the present invention, the pulling camshaft located on the pulling side of the timing belt of the two camshafts. A cam sensor is provided at the other end of the camshaft, and a dynamic damper is mounted inside the cam sensor of the pulling side camshaft. Therefore, when the engine rotates, the load on the timing belt increases and the camshaft generates Vibrations can be absorbed and reduced by the dynamic damper,
The load on the timing belt can be reduced, the life of the timing belt can be improved, and the operating noise of the internal combustion engine can be suppressed.

In addition, since the cylinder can be accurately determined by the cam sensor, the ignition timing, fuel injection timing, and fuel injection amount of the internal combustion engine can be accurately performed, and the performance of the internal combustion engine can be improved. Further, since the above-mentioned dynamic damper is disposed in a dead space (dead space) of the cylinder head corresponding to between the above-mentioned cam and the cam sensor, the whole shape of the above-mentioned internal combustion engine can be made compact.

According to the camshaft structure for an internal combustion engine of the present invention, a cam sensor is provided at the other end of the pulling camshaft located on the pulling side of the timing belt among the two camshafts. Since the dynamic damper is mounted on the sprocket mounted on the pulling side camshaft, the dynamic damper can be easily and compactly provided, and the dynamic damper is provided on the pulling side camshaft. Since it is arranged in the dead space (dead space) in the boss portion of the sprocket, the overall shape of the internal combustion engine can be made compact without changing the current layout.

Further, the vibration of the camshaft can be reliably suppressed and the increase in the load on the timing belt can be suppressed, so that the life of the timing belt can be improved and the operating noise of the internal combustion engine can be reduced. There are advantages.

[Brief description of the drawings]

FIG. 1 is a diagram showing a camshaft structure of an internal combustion engine as a first embodiment of the present invention, and is a schematic plan view showing a partly broken surface as viewed from the upper surface of a cylinder head.

FIG. 2 is an explanatory diagram showing only a timing belt system related to a valve operating mechanism as viewed in the direction of arrow Y1 in FIG. 1;

FIG. 3 is a diagram showing a camshaft structure of an internal combustion engine as a second embodiment of the present invention, and is a configuration diagram similar to FIG. 1;

4A and 4B are diagrams showing a timing belt system related to the valve operating mechanism in FIG. 3, wherein FIG.
FIG. 4B is a cross-sectional view showing a cross section of the main part along line 4B-4B in FIG.

FIG. 5 is a characteristic diagram showing a relationship between an internal combustion engine speed and a timing belt load in each of the above embodiments of the present invention.

FIG. 6 is a characteristic diagram showing a relationship between an internal combustion engine speed and a timing belt load in a conventional structure.

FIG. 7 is an explanatory view showing a conventional valve mechanism of an internal combustion engine in which a dynamic damper is not inserted.

8 is an explanatory diagram schematically showing a rotation transmission mechanism of a crankshaft and a camshaft of FIG. 7;

FIG. 9 is an end view of the engine showing a timing belt system in a DOHC type internal combustion engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder head 2a Rear wall of cylinder head 3,4 Camshaft 3a, 4a Cam 5a, 5b Rocker arm 5 Valve train mechanism 7,8 Camshaft sprocket 9 Timing belt 10 Crankshaft 11 Crankshaft sprocket 12 Dynamic damper 12a Inside Cylinder 12b Elastic member 12c Annular weight 13 Cam sensor 13A Sensing cylinder 13B Detector 20 Tension pulley 21 Tensioner 25 Rotation transmission mechanism

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code FI F16F 15/126 F16F 15/12 K (72) Inventor Tetsuro Ishida 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation Inside

Claims (2)

[Claims] 1. Two camshafts installed in pairs on a cylinder head for driving an engine valve of an internal combustion engine, a sprocket provided at one end of each of the camshafts, and the internal combustion engine A timing belt wound around a sprocket provided at one end of the crankshaft; and a tension belt installed at the other end of a tension-side camshaft located on the tension side of the timing belt of the two camshafts. A camshaft structure for an internal combustion engine, comprising: a dynamic damper mounted on the tension side camshaft inside the cam sensor. 2. A camshaft installed in a pair with a cylinder head for driving an engine valve of an internal combustion engine, a sprocket provided at one end of each of the camshafts, and the internal combustion engine A timing belt wound around a sprocket provided at one end of the crankshaft; and a tension belt installed at the other end of a tension-side camshaft located on the tension side of the timing belt of the two camshafts. A dynamic damper is mounted on a sprocket mounted on the pull-side camshaft.
Camshaft structure of internal combustion engine.