JPS62129508A - Variable valve timing device - Google Patents

Abstract

PURPOSE:To improve fuel consumption and output, by simultaneously moving a suction cam shaft and an exhaust cam shaft in the same axial direction in synchronization with rotation of a crank shaft, and changing a relative phase of each cam to each cam shaft. CONSTITUTION:When a pulley 1 is driven through a timing belt by the rotation of a crank shaft, a shaft 2 integral with the pulley 1 is rotated, and a suction cam shaft 3 connected by spline to the shaft 2 and an exhaust cam shaft 4 connected through a journal 14 to the suction cam shaft 3 are rotated. Cams 5 and 6 are connected by helical teeth 3a and 4a contrary in direction to the cam shafts 3 and 4, respectively. The axial movement of the cams 5 and 6 is limited by respective cam guides 13a and 13b through thrust bearings 17. Accordingly, relative positions of the cams 5 and 6 to the shaft 2 may be changed by moving the cam shafts 3 and 4.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 1 The present invention relates to a variable valve timing device that changes the valve timing of an internal combustion engine to improve engine output in a given operating range d3. [Prior Art] Many variable valve timing devices that change the valve timing of internal combustion engines have been proposed in the past, such as those disclosed in Japanese Utility Model Application Publication No. 104704/1983 and Japanese Utility Model Application Publication No. 55-10
As is clear from Publication No. 4705jJ, etc., the helical teeth provided on the cam drive boob are connected to the helical teeth provided on the axially movable cylindrical piston, and the piston and the camshaft are connected to each other with serrated teeth. connected by
It is known that the piston is slid in the axial direction using hydraulic pressure or the like to create a phase difference between the pulley part and the cam part. Furthermore, in JP-A No. 60-1534, a two-wheel phase adjustment mechanism is interposed between the camshaft and the camshaft drive mechanism, and the two-wheel phase adjustment mechanism has two shafts on the input side and one on the output side. Differential teeth on opposite ends of the shaft! 1! 1 shows a device equipped with an n-groove and actuated by an actuator. However, the above-mentioned prior art
As is clear from Publication No. 704 and Japanese Utility Model Application No. 55-104705, in a structure in which the phase of the cam is changed using helical teeth, when both the intake and exhaust valves are driven by one camshaft, Even if the overall phase of the camshaft and shaft was changed, the valve overlap of the intake and exhaust valves could not be changed, so the valve lift curves of both the intake and exhaust valves were simply fixed, and this is shown in Figure 5. It only moves in parallel like this, and by changing the valve overlap (
The problem is that the desired effect cannot be expected. Also, in Japanese Patent Application Laid-open No. Sho+30-153410,
- In the case of a wooden camshaft (SOHC), the phase is shifted in parallel as in the above case! There is a problem in that it is not possible to change the overlap, and in the case of two camshafts (DO and C>), the structure becomes complicated.

[Object of the invention] The present invention has been made in view of the above-mentioned circumstances, and
Instead of changing the phase of the entire camshaft in a given operating range, the phase of each individual cam can be varied, reducing overlap between the intake and exhaust valves at low speeds and preventing valve overlapping at high speeds. The purpose of the present invention is to provide a variable valve timing device whose purpose is to improve charging efficiency, improve fuel efficiency, and improve engine output by increasing the lap suspension. [Means for solving the problem 1 The above-mentioned To achieve the object, according to the present invention, in an engine valve train that controls the timing of intake valves and exhaust valves, the intake cam and the exhaust cam that actuate the intake valve and the exhaust valve are arranged so that their teeth are oriented relative to each other. The intake camshaft and the exhaust camshaft are integrally arranged on the same axis, and each of the cams Each cam connected to the shaft is held and rotated by a cam guide, and the intake camshaft and the exhaust camshaft are integrally moved in the axial direction of each of the camshafts. [Function] Based on the above configuration, according to the present invention, when an axial force is applied to the camshaft by an actuator such as hydraulic pressure, the intake camshaft and the exhaust camshaft simultaneously operate in the same direction. As the cams move in the axial direction, the relative phase of each camshaft and the cam changes due to the helical teeth.Since each of the above camshafts is synchronized with the rotation of the crankshaft, the phase of each cam with respect to the crankshaft will eventually change. Therefore, the valve timing can be changed in accordance with the engine speed, and the amount of overlap between the intake valve and exhaust valve can be changed to improve fuel efficiency or output. It becomes possible to achieve this goal.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of the main parts showing the configuration of the variable valve timing 'iA@ according to the present invention, and FIG.
Furthermore, FIG. 1 is an enlarged view showing the main parts, and FIG. 3 is an exploded view of the camshaft and cam shown in FIG. 1, and the case of a single-cylinder engine having 1111i1 intake valves and 1111i1 exhaust valves will be described. In the figure, numeral 1 is a camshaft driving gear driven by a crankshaft (not shown), 2 is a shaft to which gear 1 is fixed, 3 is an intake camshaft,
Reference numeral 4 indicates an exhaust camshaft, 5 indicates an intake valve cam, and 6 indicates an exhaust valve cam. The shaft 2 and the intake camshaft 3 are spline connected, and the intake camshaft 3 is attached to the shaft 2 so as to be movable in the axial direction. In addition, the above-mentioned intake camshaft 3 and intake valve cam 5
, the exhaust camshaft 4 and the exhaust valve cam 6 are each connected by helical teeth, and the cams 5 and 6 are held within cam guides 13a and t3b integrally formed in the cylinder head 13. It is designed to rotate. The helical teeth 3a, 4a formed on the intake camshaft 3 and the exhaust camshaft 4 are formed so that the tooth directions are opposite to each other as shown in FIG. After assembling each cam 5.6 from the joint end of the intake camshaft 3 and the exhaust camshaft 4, the intake camshaft 3 and the exhaust force shaft 1-4 are integrated with the journal 14 via the Woodruff key 1. are connected to each other. Furthermore, a hydraulic chamber 15 is formed between the end of the intake camshaft 3 and the spline-coupled shaft 2, and pressure oil is supplied and discharged by a hydraulic control device (not shown). The end of the exhaust camshaft 4 integrally connected to the intake camshaft 3 is pressed by a return spring 11 attached via a thrust bearing 16. Note that symbols g, 9, and 10 in the drawings are caps of the camshafts 3 and 4, respectively, and 12 is a presser cap of the return spring 11 that presses the end of the exhaust camshaft 4 to the left in the drawing. Further, the cam 5.6, which is connected to the cam shirts L-3 and L-4 using a helical m, is rotated via a thrust bearing 17 within the cam shafts L:13a and 13b of the cylinder head 13, as shown in FIG. Can be installed freely. This makes it possible to reduce the frictional force caused by the rotation of the cams 5 and 6. Next, the operation of the variable valve timing device configured as described above will be explained. First, when the pulley 1 is driven by the rotation of the crankshaft via the timing belt, the shaft 2 integrated with the pulley 1 rotates, and the intake camshaft 3 spline-coupled to the shaft 2;
The exhaust camshaft 4 connected to the intake camshaft 3 via the journal 14 is rotated at the same time. Here, a cam 5.6 is coupled to the camshaft 3.4 by helical teeth 3a, 4a formed in opposite directions, and the cam 5.6 is coupled to the cam shaft 3.4 by cam guides 13a, 13b via a thrust bearing 17. Since movement in the axial direction is restricted, moving the camshafts 3 and 4 to the left or right will change the relative phase of the cams 5 and 6 with respect to the shaft 2. Therefore, since the shaft 2 is synchronized with the rotation of the crankshaft, the phase of the cam 5.6 relative to the crankshaft changes, and the timing of the intake and exhaust valves can be changed as shown in FIG. . From the idling state to a predetermined engine speed (low speed state), pressure oil is not supplied into the hydraulic chamber 15 formed between the shaft 2 and the intake camshaft 3, so the camshaft 3.4 is operated by the return spring. Due to the biasing force of 11, the valve timing is positioned to the left side in the drawing, and as shown by the solid line in FIG. 4, the amount of overlap between the intake and exhaust valve timings is approximately zero at TDC (top dead center). When the engine speed reaches a predetermined speed (low speed state) or higher (high speed state), pressure oil is supplied into the hydraulic chamber 15 by a hydraulic control device (not shown), and the camshaft 3.4 is rotated against the biasing force of the return spring 11.・Moving to the right side of the figure, the intake and exhaust valve timings overlap at TDC, as shown by the dotted line in FIG. The amount of overlap between the valve timings at low and high speeds is determined according to the characteristics of each engine, and the governor pressure of an automatic transmission with a torque converter may be used as the pressure oil in the hydraulic chamber 15. As described above, the present invention can be applied to the hydraulic chamber 1 according to changes in engine speed.
Although the explanation has been given using an example of φ without controlling the pressure oil in the hydraulic chamber 15, this example is not limited to this example, and when it is desired to change the valve timing, the intake and exhaust valve timings can be adjusted to desired characteristics by controlling the oil pressure in the hydraulic chamber 15. It can be done.

【Effect of the invention】

As explained in detail above, the present invention is characterized in that the phase of each individual cam is changed instead of changing the phase of the entire camshaft by parallel translation as in the conventional example. It is possible to change the overlap between the intake and exhaust valves. Therefore, when the engine is at low 3g8v1, internal EGRffi is reduced by reducing the valve overlap of the intake and exhaust valves, improving combustion in this region and improving fuel efficiency. Furthermore, when the engine is running at high speed, by increasing the amount of valve overlap between the intake and exhaust valves, the filling efficiency is improved and the output in this region can be improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main parts showing the configuration of the variable valve timing device according to the present invention, Fig. 2 is an enlarged view showing the main parts of Fig. 1, and Fig. 3 is an exploded view of the camshaft and cam shown in Fig. 1. 4 are explanatory diagrams showing a valve lift curve according to the present invention, and FIG. 5 is an explanatory diagram showing a valve lift curve according to a conventional embodiment. DESCRIPTION OF SYMBOLS 1... Gear, 2... Shaft, 3... Intake camshaft, 4... Exhaust camshaft, 5... Intake valve cam, 6... Exhaust valve cam, 11...・・・
Return spring, 13... Cylinder head, 13
a, 13b...cam guide, 14...journal, 15...hydraulic chamber. BD (: TDOBE) C Kura>7 mountain θ Ya 5 must 7-7 shi legitimate θ

Claims (1)

[Scope of Claims] In an engine valve train system that controls the timing of intake and exhaust valves, the intake cam and the exhaust cam that operate the intake and exhaust valves are provided with helical teeth whose teeth are in opposite directions. The intake camshaft and the exhaust camshaft are integrated and arranged on the same axis, and each cam connected to each of the camshafts is connected to an intake camshaft and an exhaust camshaft formed with a A variable valve timing device, characterized in that the variable valve timing device is configured to be held and rotated by a cam guide, and to move the intake camshaft and the exhaust camshaft integrally in the axial direction of each of the camshafts.