JPS6017214A - Valve gear for internal-combustion engine - Google Patents

Abstract

PURPOSE:To control the lifting time of a valve, by making up a cam, driving both suction and exhaust valves, with two cam halving part which take partial charge of the first half and the latter half of the valve lift, while relatively turning round both valves centering on a cam shaft. CONSTITUTION:A cam, driving a suction valve or an exhaust valve, is made up of two cam halving parts 30 and 32 installed on top of a sleeve 14. The cam halving part 30 on one side is locked to the sleeve 14 while the cam halving part 32 on the other is locked to a core shaft 12. The core shaft 12 and the sleeve 14 are interlocked via a slide pin 64 piercing through slits 58 and 60, being crossed with each other, installed in each of them, and each relative phase of both 12 and 14 is controlled by a motor 70 upon adjustment of an axial position of the slide pin 64. With this constitution, the life time of the cam formed by both these cam halving parts 30 and 32 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a valve train with variable operating angle in an internal combustion engine, and can be advantageously used in a device with variable valve timing depending on engine operating conditions. be.

The cam operating angle of prior art internal combustion engines determines the crank angle from the beginning to the end of valve lift. The required value for the start or end timing of the valve lift changes depending on engine operating conditions.

However, in the prior art, since the cam operating angle was constant, it was difficult to adapt the cam operating angle to the entire rotation range of the engine. That is, if the cam operating angle is set toward high speed, low speed, especially idling, becomes unstable, and to avoid this, the idling speed must be set high, which of course worsens the fuel consumption rate. Conversely, if the operating angle is set toward low speed, high output cannot be obtained.

OBJECTS OF THE INVENTION An object of the present invention is to provide a valve train that can achieve optimal cam operating angle characteristics over each engine rotation range.

Structure of the Invention In the present invention, a camshaft is composed of a core shaft and a sleeve shaft rotatably fitted to the core shaft, and the sleeve shaft is in charge of the entire first and second half of the lift during one rotation of the cam. A pair of cam halves forming a single cam profile are provided, one cam half being fixed to the sleeve shaft and the other cam half rotatable relative to the sleeve shaft but not relative to the core shaft. A driving means is provided which is fixed and causes relative rotation between the core shaft and the sleeve shaft. The actuation of the drive means causes relative rotation between the core shaft and the sleeve shaft, causing the pair of cam halves to be out of phase in the direction of rotation of the camshaft, resulting in a change in the cam operating angle.

Therefore, a cam operating angle suitable for the operating conditions can be obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, in FIG. 1, a camshaft 10 comprises a core shaft 12 and a sleeve shaft 14 loosely fitted around the core shaft 12. Metal 1 on sleeve shaft 14
6 is fixed by a pin 18. The metal 16 is placed on the journal portion 2G of the camshaft housing, and is covered with the cam bearing camp 22. Sleeve shaft 1
4, a timing pulley 24 is fitted at a boss portion 248, and a bobbin portion 24G of this pulley 24 is connected to a crankshaft by a timing belt (not shown).

A first cam half 30 and a second cam half 32 are provided adjacently on the sleeve shaft 14 . The first and second cam halves 30 and -32 exhibit cam ridges 301 and 321, respectively, and these form one cam profile as a whole. (arrow in figure 3)
, the cam ridge 301 of the first cam half 30 is located in front of the cam ridge 321 of the second cam half 32, and takes charge of the first half and the second half of the cam lift, respectively.

The first cam half 30 is connected to the sleeve shaft 1 by means of a pin 36.
It is fixed at 4. On the other hand, the second cam half 32 is rotatable on the sleeve shaft 14 and fixed to the core shaft 12 by a pin 38 . This pin 38 is inserted through a slit 39 formed in the sleeve shaft. The size and shape of the slit 39 are such that the core shaft 12 can be freely twisted relative to the sleeve shaft 14 within a range of changing the cam operating angle, which will be described later.

Twisting the core shaft 12 relative to the sleeve shaft 14,
The following rotary drive means is provided to perform variable control of the cam operating angle. That is, the cap member 50 is fitted to the end of the core shaft 2 until it touches the shoulder 141 of the sleeve shaft, and is fixed to the core 112 by a bolt 52 and prevented from rotating by a stop pin 54. A slit 56 inclined in the camshaft direction is cut in the cylindrical surface of the cap member 5o as shown in FIG. A parallel slit 58 is cut.

Incidentally, a slit 60 that is aligned with this slit 58 is also formed in the boss portion 24^ of the pulley 24. A slide pin 64 perpendicular to the camshaft is fitted into the inclined slit 56 of the cap part 50 and the straight slits 5B and 60 to the sleeve shaft 14 and boss part 24, and this slide pin 64
is carried by a slider 68 that is fitted into the camp portion 5o so as to be slidable in the camshaft direction. Due to this configuration, when the slider 68 moves linearly in the camshaft direction, relative rotation between the core shaft 12 and the sleeve shaft 14 connected to the locking tube 5o occurs due to the intersecting relationship between the slits 56, 58, and 60, and the cam action is The angle changes.

Reference numeral 70 denotes a rotary drive motor, and its output shaft 72 is fitted into a nut 7G held in the motor housing 74 so as to slide in the direction of the non-rotating toothpick camshaft. This nut 76 is connected to the slider 68 via a bearing 8o. In this configuration, the rotation of the remote motor output shaft 72 is caused by the slider 6
8, and the cam operating angle can be controlled in accordance with the engine operating conditions.

Reference numeral 84 denotes a cover, one end of which is connected to the pulley hub portion 24B by a bolt 86, and the other end connected to the motor housing 74 by a bearing 88.

Further, 90 is a timing belt cover.

To describe the operation of the present invention as described above, when the motor 70 is rotated in one direction, the NAND 7o moves 111 m to the right, and this is transmitted to the pin 64 of the slider 68 as a movement in the direction of the force indicated by the arrow X in FIG. , this is done until the pin 64 hits the stopper as the slit end face. At this time, a third
A relative rotation occurs in the direction opposite to the arrow in the figure. At this time, the cam ridge 321 of the cam half 32 fixed to the core shaft 12 is positioned as shown by the two-dot chain line on the advancing side in the rotational direction of the camshaft with respect to the cam ridge 301 of the cam half 30 fixed to the sleeve shaft 14. do. At this time, the cam working angle is at its minimum. Here, the cam operating angle is defined as the crank angle at which the cam ridge 301 contacts the valve stem during cam rotation and starts to lift the valve, and the cam ridge 321 stops contacting the valve stem and the valve lift reaches 0. This refers to the angle between the crank angle and the crank angle.

That is, in FIG. 6, the two-dot chain line is the valve lift curve with respect to the crank angle when the cam operating angle is the minimum, and the exhaust valve starts opening at the crank angle k, and at the crank angle k2. At this angle, the exhaust valve finishes closing. Prior to that, the intake valve begins to open at a crank angle of 3 and ends closing at a crank angle of 4. The cam operating angle at this time is therefore expressed as ^. Also,
The angle αI between the intake valve opening start crank angle of 3 and the exhaust valve closing end crank angle of 3 is called overlap, and this state of small overlap is suitable for low speed operation of the engine.

When the motor 70 is reversed in the opposite direction, the nut 76
moves to the left in FIG. 1, the bin 64 on the slider 68 moves as indicated by Xt in FIG. 4, and the slider 68 reaches a stopper as the motor housing 74. The relative rotation between the core shaft 12 and the sleeve shaft 14 at this time produces an angle δ corresponding to the inclination angle of the slit and the stroke, and as a result, the cam half 321 fixed to the core shaft 12 is rotated as shown in FIG. It moves by an angle of δ from the position of the two-dot chain line to the position of the solid line.

Therefore, the cam operating angle increases, and the lift curves of the intake and exhaust valves become as shown in the solid line in Figure 6, and the cam operating angle becomes ^
It becomes large as 2. That is, the crank angle at which the valve starts engaging the cam half 301 is the same as in the previous case;
, k3, but the overlap angle α of the cam half 321
2 is larger than before, which, as is well known, is suitable for high engine speeds.

Effects of the Invention By making the cam working angle variable, it is possible to obtain valve timing that matches the engine operating conditions, and it is possible to satisfy both the requirements for reducing fuel consumption rate and increasing the output direction.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an axial cross-sectional view of the valve train of the present invention, FIG. 2 is a cross-sectional view taken along line nm in FIG. 1, and FIG. 3 is a cross-sectional view taken along line m-m in FIG. m
4 is a cross-sectional view taken along line V-V in FIG. 1, FIG. 5 is a sectional view taken along line V-V in FIG. 1, and FIG. 6 is a valve lift of the valve train of the present invention. Line diagram. 10...Camshaft, 12...Core shaft, 14...
Sleeve shaft, 30, 32...cam half. fIIkl Figure 3 Figure 2 × 1 40th -! 2

Claims (1)

[Claims] In an internal combustion engine, a camshaft is composed of a core shaft and a sleeve shaft rotatably fitted to the core shaft, and a pair of shafts are mounted on the sleeve shaft to handle the first and second half of one cam lift during rotation of the camshaft. Cam halves are provided, one cam half is fixed to the sleeve shaft, the other gum half is rotatable with respect to the sleeve shaft but fixed with respect to the core shaft, and the core shaft and sleeve shaft are connected to each other. A valve train provided with a drive means for causing relative rotation of the valve.