JP2504996Y2 - Variable valve timing mechanism for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a variable valve timing mechanism for an internal combustion engine having an intake camshaft and an exhaust camshaft.

[Conventional technology]

In an internal combustion engine equipped with an intake valve driving camshaft (hereinafter referred to as intake camshaft) and an exhaust valve driving camshaft (hereinafter referred to as exhaust camshaft), the camshafts are interlocked by a helical gear. However, one of the helical gears of the camshaft is sandwiched by the fork-shaped members from both sides, and the helical gears are mounted on the other camshaft via the fork-shaped members, and the operating conditions of the engine (rotational speed,
A valve drive device that moves in the axial direction according to the load) and changes the valve timing accordingly is already known (Shokaisho)
61-27908).

[Issues to be solved]

However, in the case where one of the helical gears is driven by an externally provided drive device as described above, not only the problem that the size of the cylinder head becomes large due to the installation of the drive device but also the cylinder head There is a problem that the structure of is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable valve timing mechanism capable of extremely simplifying the structure without increasing the size of the cylinder head or complicating the structure of the cylinder head.

[Means for solving the problem]

In order to achieve the above object, the present invention comprises an intake camshaft and an exhaust camshaft, and attaches helical gears to each camshaft so that these helical gears mesh with each other, and one camshaft is driven by a crankshaft. In the internal combustion engine in which the other camshaft is driven by the one camshaft via the helical gear, the helical gear attached to the other camshaft rotates with the other camshaft and the axial direction of the other camshaft. Of the helical gear, which is spline-coupled to the other cam shaft so as to be movable to the other end, and the axial end face of the helical gear attached to the other cam shaft, and the end wall which is disposed facing the end face and is fixed to the other cam shaft. A hydraulic chamber is formed between the two, and this hydraulic chamber is connected to the other cam. The other camshaft is connected to the hydraulic control valve device via the oil passage formed in the shaft, and the helical gear is moved in the axial direction by the hydraulic pressure of the hydraulic chamber that directly acts on the axial end face of the helical gear. It is arranged to rotate relative to one of the camshafts.

[Action]

When the hydraulic pressure in the hydraulic chamber is increased by the hydraulic control valve device, the helical gear moves axially by directly receiving this hydraulic pressure, which causes the other camshaft to rotate relative to one camshaft. To be

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a top view of a partial cylinder head having a variable valve timing mechanism according to the present invention.

The cam pulley 1 is fixed to the end portion of the exhaust camshaft 2 and is rotationally driven by a crankshaft (not shown) via a timing belt. The exhaust camshaft 2 is provided with an exhaust side helical gear 3, and the intake camshaft 4 juxtaposed to the exhaust camshaft 2 is also provided with an intake side helical gear 5, and these helical gears 3 and 5 are also provided. Mesh with each other. Therefore, the rotational driving force transmitted to the exhaust camshaft 2 is transmitted to the intake camshaft 4 via the helical gears 3 and 5, so that the intake camshaft 4 also rotates.

FIG. 2 shows the structure of the variable valve timing mechanism according to the present invention. According to the present embodiment, which is a partial cross-sectional view of the intake camshaft, the cylindrical helical gear holding member 6 is provided on the outer periphery of the intake camshaft 4 by, for example, shrink fitting.
Are fitted and fixed. The helical gear holding member 6 is positioned in the camshaft 4 in the axial direction of the camshaft by a flange 4a provided on the camshaft 4 and a thrust bearing 7, and a key 8 embedded in the camshaft 4 prevents the helical gear holding member 6 from moving in the rotational direction of the camshaft. The positioning is done. Further, an oil passage 6a connected to an oil passage 4b of the camshaft 4 described later is formed inside the helical gear holding member 6, and the helical spline 6b and the oil seal ring grooves 6c, 6d are formed on the outer periphery of the member 6. Is formed.

The intake side helical gear 5 is arranged on the outer periphery of the helical gear holding member 6, and the inner peripheral surface of the helical gear 5 meshes with the helical spline 6b formed on the outer periphery of the holding member.
5a is formed. That is, the intake side helical gear 5 and the intake camshaft 4 are spline-coupled via the helical gear holding member 6, and the helical gear can move independently in the camshaft axial direction. The intake side helical gear 5 is biased in the left direction in the figure by a return spring 9 having one end placed on the thrust bearing 7. The helical gear end face 5b supported by the spring 9 has an axial end face 5c opposite to the helical gear end face 5b. The oil passage 6a inside the helical gear holding member is opened, and the hydraulic chamber 10 is defined by the axial end surface 5c of the helical gear 5 and the disk-shaped end wall of the helical gear holding member 6 facing the end surface 5c. To be done. In the figure, reference numerals 11 and 12 denote oil seal rings mounted on the holding member 6, so that oil leakage from the hydraulic chamber 10 to the outside can be prevented. Reference numeral 13 is a nut that restricts the axial movement of the thrust bearing 7 described above.

An oil passage (oil gallery) 4b is formed inside the intake camshaft 4 so as to extend in the camshaft axial direction from the end of the camshaft and communicate with the preceding holding member internal oil passage 6a. At the end of the camshaft where the oil passage 4b opens, a control valve 15 equipped with a piston 14 that is slidable in the camshaft axial direction is mounted inside, and on the side of the control valve, the detected operating condition ( For example, depending on the engine speed and the intake pipe pressure as a representative load value, the piston 14
A solenoid 17 (solenoid valve) having a plunger 16 that slides is arranged in line. These control valves 15
Also, the solenoid 17 constitutes a valve device according to the present invention, and the solenoid is operated by a control signal from a control circuit (ECU) 18 for inputting the above operating conditions. In addition, the piston 14 inside the control valve has a spring 19 mounted inside the valve 15 when the solenoid 17 is not operated,
Moved to the right.

Oil 20 is filled in the oil passages 4b and 6a extending from the end of the camshaft to the end surface 5c of the helical gear. This oil is supplied from the inside of the cylinder head 21 to the thrust bearing 7 and the oil passage 7a formed in the camshaft 4. This oil supply path is closed through a system separate from the lubricating oil path 4d normally formed inside the camshaft as shown in the figure, or by not forming oil paths 7a and 4c although not shown. It is preferable to use a different path to prevent the piston 14 from sticking by making it less susceptible to changes in the oil viscosity due to changes in sludge and engine temperature.

Next, the operation of this mechanism will be described with reference to FIGS. 2 and 3. FIG. 3 shows an example of a valve timing switching map of the variable valve timing mechanism according to the present invention.
When in the low speed / high load operation range, the solenoid 17 is energized (ON) by the control circuit 18. Then, the plunger 16 moves the piston 14 to the left in the drawing, and the pressure in the hydraulic chamber 10 thus raised causes the intake side helical gear 5 to rotate smoothly along the helical splines 5a and 6b in the direction in the drawing. It will move (helical gear position shown in FIG. 2).

As a result, between the outer peripheral portion of the intake side helical gear 5 and the outer peripheral portion of the exhaust side helical gear 3 (FIG. 1), and between the inner peripheral helical spline 5a of the intake side helical gear 5 and the outer peripheral helical spline 6b of the helical gear holding member 6. A phase difference occurs between the intake valves, and in this meshed state, the intake valve (not shown) is quickly opened and closed as shown in the lower part of FIG. 4, so that a so-called low-speed valve timing is achieved. In this case,
A desired phase difference between the helical gears can be achieved by changing the gear angles of the inner and outer peripheral helical splines 5a and 6b. On the other hand, when the engine is in a region other than the shaded region in FIG. 3, that is, at high speed, low-medium-speed low-load region, and idling region, the solenoid 17 is inactive (OFF). in this case,
The piston 14 inside the control valve 15 is moved to the right in FIG. 2 by the spring 19, so that the pressure inside the hydraulic chamber 10 decreases, and the helical gear 5 on the intake side returns to the return spring 9
Due to the urging force of the above and the thrust force received by the intake camshaft 4, it moves to the left in the figure while rotating along the spline (the position of the helical gear shown in FIG. 2). As a result, the phase difference between the intake side helical gear 5 and the exhaust side helical gear 3 disappears, and in this meshed state, the intake valve becomes a preset high-speed valve timing, that is, a late opening and a late closing as shown in the upper part of FIG. The overlap becomes smaller.

FIG. 5 shows the output and torque characteristics of a general engine for the above-mentioned high-speed type and low-speed type valve timing respectively. According to the present embodiment, the solid line in the figure shows in the middle / low speed / high load range. Since the low speed type valve timing shown in Fig. 2 improves the low / medium speed torque, while the high speed type valve timing shown by the dotted line in the figure is used in other operating ranges, the set original high output type engine is achieved. In addition, the idle performance can be improved and the fuel economy can be improved with a small overlap.

〔effect〕

As described above, according to the present invention, since the valve timing is controlled by controlling the hydraulic pressure in the hydraulic chamber inside the helical gear, the cylinder head does not become large and the structure of the cylinder head becomes complicated. It will never happen. Further, in the present invention, the helical gear is directly driven by hydraulic pressure without interposing a hydraulically driven piston or the like. In other words, the helical gear itself also functions as a hydraulic piston. As a result, the structure of the variable valve timing mechanism can be extremely simplified.

[Brief description of drawings]

FIG. 1 is a partial cylinder head top view of an internal combustion engine having a variable valve timing mechanism according to the present invention; FIG. 2 is a partial camshaft sectional view taken along the line II-II in FIG. 1; FIG. 4 is a map diagram showing an example of a valve timing switching region of the variable valve timing mechanism; FIG. 4 is a graph showing a valve lift characteristic by the above mechanism; FIG. 5 is a diagram showing engine output and torque characteristic of high and low speed type valve timing respectively. 2 ... Exhaust camshaft, 3 ... Exhaust side helical gear, 4 ... Intake camshaft, 5 ... Intake side helical gear, 4b ... Oil passage, 15 ... Control valve (valve device), 17 ... Solenoid (Valve device).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-191606 (JP, A) Jpn. Application No. 59-111031 (Jpn. (JP, U) Microfilm (JP, U) Actual application No. 58-151742 (Shokai No. 60-58805)

Claims (1)

(57) [Scope of utility model registration request] Claim: What is claimed is: 1. An intake camshaft and an exhaust camshaft are provided, and helical gears are attached to the respective camshafts so that the helical gears mesh with each other, and one camshaft is driven by a crankshaft while the other camshaft is driven. In an internal combustion engine in which the one camshaft is driven via the helical gear, the helical gear attached to the other camshaft is rotated together with the other camshaft, and in the axial direction of the other camshaft. An axial end surface of a helical gear that is movably spline-coupled to the other cam shaft and is attached to the other cam shaft, and an end wall that is disposed facing the end surface and is fixed to the other cam shaft. An oil pressure chamber is formed between the Of the other cam by moving the helical gear in the axial direction by the hydraulic pressure of the hydraulic chamber directly acting on the axial end surface of the helical gear, which is connected to the hydraulic control valve device through the oil passage formed in the inside of the cam. A variable valve timing mechanism for an internal combustion engine, wherein a shaft is rotated relative to the one camshaft.