JPH1193624A - Valve system for driving camshaft by use of connecting rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system for driving a camshaft by means of light- weight connecting rods of a simple structure having a reduced number of part items featuring little noise and space saving. SOLUTION: In a valve system of an OHC type engine, at least two connecting rods 4a, 4b pivotally supported at both ends thereof are interposed between rotors 3a, 3b and a camshaft 5 to be driven by a crankshaft 1 in such a manner that an eccentric distance at the camshaft 5 becomes equal to those at the rotors 3a, 3b. Furthermore, these at least two connecting rods 4a, 4b are disposed with angular deviation with respect to a rotating direction of the camshaft 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating mechanism for opening and closing an intake valve and an exhaust valve of an OHC type engine, and more particularly, to transmitting a rotational force of a crankshaft to a camshaft by a connecting rod. The present invention relates to a valve operating mechanism.

[0002]

2. Description of the Related Art In an internal combustion engine such as a diesel engine, one camshaft is disposed on a cylinder head side, and a cam provided on the camshaft operates a valve mechanism for opening and closing an intake valve and an exhaust valve. There is an OHC (overhead camshaft) engine used.

In general, the driving of the camshaft of the OHC engine is performed by a timing belt or a timing chain in a small engine, and is performed by a timing gear in a diesel engine for a commercial vehicle. However, the timing belt uses a toothed rubber belt, so when the driving force is large, the belt and the bearing are likely to be worn, and the life is shortened in a high-temperature atmosphere. There is a problem that it is not suitable for those with a long vehicle life, and furthermore, because of its low water resistance and oil resistance, it is necessary to completely shield engine oil and water from entering from outside. is there.

Further, the timing chain has a disadvantage that a timing shift occurs due to wear of the chain connecting portion, and a tensioner for automatically adjusting tension and a meandering of the chain because the chain extends and becomes loose during use. Since a mechanism such as a damper for regulating the air pressure is required, the structure is complicated, the assembly is difficult, and there is a problem that the weight is heavy. To solve the problems of the timing belt and the timing chain, a camshaft is driven by a timing gear.

This timing gear is shown in FIGS.
The rotation of the crankshaft 1 is transmitted to the camshaft 5 by the gear trains 12, 13, 14, 15, 16, 17 as shown in FIG. It can withstand enough force and has good durability.

[0006]

However, the gears used in the gear train of the timing gear generally use a helical gear in order to smooth rotation and reduce noise. High precision is required for the bending strength of the gears and the machining of the teeth, and the assembly is also required to have high precision, which raises the problem that the cost increases.

There is also a problem that the weight is increased due to the large number of gears, and the space for accommodating these gear trains is also increased. In transmitting the rotational force (torque) by the gear train of the timing gear, since the fluctuation torque of the cam is large, the backlash of the gear causes the teeth to repeat collisions and separations, resulting in the generation of a rattling sound. There is.

For example, in the case of the L-type OHC engine shown in FIG.
In the V-type OHC engine of five locations, that of FIG. 6 and FIG. 8, there are many locations of six locations and eight locations, respectively, so that the engine as a whole is a large noise source. Especially in the idling state, the combustion noise of the engine such as slap noise is small, and the fluctuation of the rotation of the crankshaft, that is, the change of the angular velocity is large. There is a problem that the sound is noticeable.

[0009] Therefore, in order to reduce the gear hitting noise of the gear train, the two teeth urged in the opposite rotational directions by the spring force sandwich the tooth of the mating gear to absorb the backlash. A scissors gear system that prevents the occurrence of tooth rattling, and a friction gear with one tooth different from the driven gear is pressed against the driven gear with a spring, and meshing with this friction gear cancels the backlash to reduce the rattling noise. Numerous noise countermeasure technologies have been developed, such as a friction gear system for preventing the noise, and a gear made of a material having a high vibration damping property such as ADI (Austempered Ductile Iron).

[0010] However, these countermeasures against tooth rattle have problems that the apparatus becomes complicated, the cost becomes high, and the weight increases. The present invention has been made in order to solve the above-mentioned problem, and an object of the present invention is to provide a camshaft using a connecting rod that has a small number of parts, has a simple structure, is lightweight, saves space, and has low noise. An object of the present invention is to provide a driving valve mechanism.

[0011]

In order to achieve the above object, a camshaft drive mechanism for driving a camshaft of an OHC engine is provided between a rotating body driven by a crankshaft and the camshaft. At least two connecting rods whose both ends are pivotally supported so that the eccentric distance of the camshaft is equal to the eccentric distance of the rotating body, and the at least two connecting rods are rotated by the rotation of the camshaft. The camshaft is driven by a connecting rod at an angle with respect to the direction.

That is, since the camshaft needs to be rotated at a half of the rotation of the crankshaft, the camshaft is rotated by 1/2 of the driven gear.
The speed is reduced to two rotations, and the driven gear, which is a rotating body, and the camshaft are connected by a connecting rod, which is a rod that movably connects the members, to transmit the driving force of the crankshaft to the camshaft. One end of the connecting rod does not necessarily need to be directly connected to the driven gear, but may be connected to a rotating body that is driven to rotate at half the rotation of the crankshaft. That is, the rotating body may be a driven gear or another rotating body such as an arm.

When the camshaft is driven by the connecting rod, that is, when the rotation of the rotating body is transmitted to the camshaft, the distance between the pivotal portions at both ends of the connecting rod is determined by the distance between the axis of the camshaft and the rotating body. Is formed to have the same distance from the axis of According to this configuration, the intermediate gear in the driving portion of the camshaft of the valve operating mechanism is omitted, and the rotation is transmitted by the connecting rod having a simple structure, so that the number of gears is reduced and the weight is reduced. In addition, since the number of meshing points between the gears is reduced, the gear rattle and the noise are reduced. Further, since the connecting rod has little expansion and contraction and good durability, the operation of the cam at an accurate timing is continued.

Further, when the at least two connecting rods are provided at the front end and the rear end in the longitudinal direction of the cylinder arrangement of the internal combustion engine, the driving force acting on the camshaft is dispersed at both ends of the camshaft. As a result, the torsional stress generated in the camshaft is reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1 of the in-line engine and FIG. 2 of the V-type engine, a front crank gear 2a is provided at a front end of a crankshaft 1 and a rear crank gear 2b is provided at a rear end thereof, and a front driven gear ( An idle gear 3a and a rear driven gear 3b are provided. The number of teeth of the driven gears 3a and 3b is determined by the camshaft 5 and the crankshaft 1
It is necessary to rotate at half the number of rotations of
It is assumed to be twice the number of teeth of the crank gears 2a and 2b.

The front driven gear 3 which is the rotating body
A shaft hole 31a at one end of the front rod (linking rod) 4a is fitted to a shaft portion 31a provided at a portion separated by a predetermined eccentric distance Da from the shaft center 30a of the front rod 4a. As shown in FIG. 5, the front arm 51a provided at the front end of the camshaft 5
a shaft portion 52 provided at a portion separated from the a by the eccentric distance Da.
a, and fixed with a washer 43 and a nut 44.

The front rod 4a drives the camshaft 5, that is, the rotation of the front driven gear 3a
Therefore, the distance between the bearing holes 41a and 42a, which are pivotal support portions at both ends of the front rod 4a, is the same as the distance between the axis 50a of the camshaft 5 and the axis 30a of the front driven gear 3a. The bearing holes 41a, 42a and the shaft center 50a,
30a will form each vertex of the parallelogram.

Also, at the rear end of the crankshaft 1,
Similarly to the front end side, a bearing hole 41b on one end side of the front rod 4b is fitted to a shaft portion 31b provided at a portion separated from the shaft center 30b of the rear driven gear 3b by a predetermined eccentric distance Db. Of a rear arm 51b provided at the rear end of the shaft 5,
The bearing hole 42b at the other end of the rear rod 4b is fitted to a shaft portion 52b provided at a portion separated from the shaft center 50b of the camshaft 5 by the eccentric distance Db.

The rotation of the driven gears 3a and 3b is transmitted to the arms 51a and 51b of the camshaft 5 by the rods 4a and 4b pivotally supported at both ends, and the camshaft 5 rotates at half the rotation speed of the crankshaft 1. Let it. This rod 4
In transmitting the rotational force by the rods 4a, 4b,
At the top dead center and the bottom dead center of b, no rotational force can be transmitted except for the inertial force in the rotational direction of the arms 51a and 51b. Therefore, at least two or more rods 4a and 4b are provided. The phase difference Δα is provided by shifting the angle of the rotation direction of the shaft portions 52a, 52b, which are the connecting portions of the arms 51a, 51b, of the camshaft 1 so that the top dead center and the bottom dead center of both arms 51a, 51b are They are formed so that they do not coincide (Δα ≠ 0 ° and Δα ≠ 180 °).

That is, at least two rods 4a, 4a
b, the driven gears 3a, 3b and the arm 51 of the camshaft 1
The rods 4a and 4b are connected to each other, and the rotational angles of the rods 4a and 4b are shifted to have a phase difference Δα so that the rotational force can be always smoothly transmitted. When the number of the rods is two, it is preferable to set the phase difference to 90 ° or 270 ° because the transmission force becomes relatively smooth.

Further, as shown in FIGS. 3 and 4, when an auxiliary machine such as a fuel injection pump whose rotation speed is ク ラ ン ク of the crankshaft 1 is located near the crankshaft 1, A gear (rotating body) 7 for driving the auxiliary machine is provided with an axis of the gear 7.
The rod 4c can be connected to a position away from the 70c by a predetermined eccentric distance Dc. Then, as shown in FIG. 4, one end of the camshaft 5 has a rod 4 attached to a front driven gear 3a, which is another rotating body, and a gear 7 for driving an accessory.
When the first and second rods 4a and 4c are provided, the front rod 4a and the second rod 4c can be connected to the arms 51a and 53a at one end of the camshaft 5, respectively. Can be provided.

Similarly, when the two rods 4a and 4c are provided on the front and back of the same rotating body, the connecting portions between the connecting rods of the pistons and the crankshaft are so arranged that the rods 4a and 4c do not collide with the camshaft 5. As described above, it is necessary to provide the concave portion 54a remote from the shaft center 50a on the camshaft 5 side, and connect the rod 4c to the concave portion 54a. However, in order to equalize the load of the rotational force of the camshaft 5,
As shown in FIGS. 1, 2 and 3, these rods 4a,
4b (or 4a, 4c) is preferably dispersed at the front and rear ends in the longitudinal direction of the cylinder arrangement of the internal combustion engine, that is, it is preferable that the rotational force can be transmitted at both ends of the camshaft 5.

In the valve operating mechanism for driving the camshaft by the connecting rod having the above configuration, the rotational force of the crankshaft 1 is reduced to 1/2 rotation by the driven gears 3a and 3b.
Since the power is transmitted to the camshaft 5 by the rods 4a, 4b, and 4c, the driving portion of the camshaft 5 can be simplified, and the intermediate gear and the bearing portion for the intermediate gear, Since a path for lubricating the bearing portion and the like can be eliminated, the driving portion of the camshaft 5 can be significantly reduced in weight.

Further, since the number of gears which increases the cost in manufacturing and maintenance can be reduced, the cost can be reduced, and the space required for accommodating the driving portion of the camshaft 5 is also reduced. The rods 4a and 4b have a relatively limited range of motion and a small thickness.
Since the rotation is transmitted by the, the space can be reduced, and the engine can be made compact.

In addition, the rods 4a, 4b, 4c
Since it receives only tensile and compressive forces, it is not subject to twisting itself, it requires less strength and has a simpler shape, and it can be easily formed of a metal material with less expansion and contraction and excellent durability. Since the transmission can be performed accurately, the timing of the operation of the cam can be accurately maintained. As for noise, the bearing hole 42a of the rod 4a and the arm 51 shown in FIG.
The gap of the fitting of the shaft portion 52a may be about 20 μm,
General backlash amount of gear 0.05-0.1mm
Because it is very small compared to, there is less backlash,
In addition, since this fitting portion has good oil film retention and can reduce play by the oil film, generation of noise from the supporting portions of the rods 4a, 4b, 4c can be significantly suppressed, and
Since the number of meshing points of the gears can be reduced to about two or three, and the rattle noise can be reduced, the noise can be significantly reduced.

The driving force acting on the camshaft 5 is provided by dispersing the at least two rods (linking rods) 4a and 4b at the front end and the rear end in the longitudinal direction of the cylinder arrangement of the internal combustion engine. Can be applied to both ends of the camshaft 5 in a distributed manner, so that the stress caused by the torsion of the camshaft 5 generated by the driving torque and the force acting on the cam is smaller than when the driving force is transmitted by only one end. The strength of the shaft system of the camshaft 5 can be reduced to reduce the weight.

[0027]

As described above, in the valve operating mechanism for driving the camshaft by the rod according to the present invention, the mechanism for transmitting the rotational force of the crankshaft to the camshaft using the connecting rod (rod) is used. And the need for expensive intermediate gears, bearings for these intermediate gears, and lubrication of these gears are eliminated, which makes it possible to reduce the weight of the drive parts of the camshaft and reduce costs. Can be planned.

Further, since the connecting rod can be easily formed of a metal material or the like which has little expansion and contraction and is excellent in durability, the rotation can be accurately transmitted, and the operation timing of the cam can be accurately maintained. Further, the space required for housing the driving portion of the camshaft can be made compact, so that the entire engine can be made compact. Moreover,
With respect to noise, the number of meshing portions of the gears can be reduced, and the rattle noise can be reduced. Further, since the number of gears is reduced, it is relatively easy to employ a scissor gear as a measure against noise, so that noise can be further reduced.

Further, by dispersing the at least two rods at the front end and the rear end in the longitudinal direction of the cylinder arrangement of the internal combustion engine, the driving force acting on the camshaft is distributed to both ends. Therefore, as compared with the case where rotation is transmitted only on one side, the stress due to the generated torsion can be reduced, the strength of the shaft system of the camshaft can be reduced, and the weight can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a part of a configuration of a camshaft driving portion according to the present invention.

FIG. 2 is a front view showing a part of a configuration of another camshaft driving portion according to the present invention for a V-type engine.

FIG. 3 is a perspective view showing a part of the configuration of another camshaft driving portion according to the present invention.

FIG. 4 is a perspective view showing a part of the configuration of another camshaft driving portion according to the present invention.

FIG. 5 is an exploded view showing a configuration of a connecting portion of a rod.

FIG. 6 is a side view showing a valve operating mechanism of a conventional V-type engine.

FIG. 7 is a gear layout diagram showing an example of a gear train of a valve train of a conventional series engine.

FIG. 8 is a gear layout diagram showing an example of a gear train of a valve train of a conventional V-type engine.

[Explanation of symbols]

Reference Signs List 1 crankshaft 2a, 2b crank gear 3a, 3b driven gear (rotating body) 4a, 4b, 4c
Rod (connecting rod) 5 Camshaft 7 Gears for driving auxiliary equipment 30a, 30b, 50a, 50b, 70c Shaft centers 31a, 31b, 52a, 52b, 54a Bearing portions 41a, 41b, 42a, 42b Bearing holes 43 Washers 44 Nuts 51a, 51b, 53a Arm Da, Db, Dc Eccentric distance

Claims (2)

[Claims] When driving a camshaft of an OHC engine, an eccentric distance of the camshaft is equal to an eccentric distance of the rotating body between the rotating body driven by a crankshaft and the camshaft. At least two connecting rods whose both ends are pivotally supported, and the at least two connecting rods are provided at an angle with respect to the rotation direction of the camshaft, and the camshaft is driven by the connecting rod. . 2. The camshaft is driven by the connecting rod according to claim 1, wherein the at least two connecting rods are provided separately at a front end and a rear end in a longitudinal direction of a cylinder arrangement of the internal combustion engine. Valve train.