JP2001140611A - Valve opening/closing angle variable cam device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold a best combustion condition by setting a proper intake/exhaust valve opening/closing angle in every load ranges and rotating speed. SOLUTION: This device is composed of a cam roller having an elliptical shaped cross section wherein a cam profile is continuously changed while holding a top point of a cam in a constant level, which is brought into correctly contact at every positions of the cam profile, and for transmitting cam lift force; and a cam shaft moving device for freely moving a cam shaft 2 in the axial direction. In the case where the cam is a low load, a valve opening angle is reduced. In the case where the cam is a high load, the valve opening angle is increased. The opening and closing positions of each intake and exhaust valve can be set to the optimal position, the lifting range of the valve is constantly held since the top point of the cam is constantly held, and unreasonable force is not applied on the valve and a valve seat. The cam is moved in the axial direction to a cam position corresponding to a load condition during operation of an engine by the cam shaft moving device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0101]

The present invention realizes perfect combustion from a low load range to a high load range by providing ideal valve timing in the field of an internal combustion engine of an industrial machine, thereby increasing the average effective pressure and increasing the indicated thermal efficiency. It is intended to provide improved fuel efficiency and reduced exhaust gas.

[0092]

2. Description of the Related Art Conventionally, in an internal combustion engine, a valve timing is often set to an optimum valve angle in an operation state of a rated output, and in recent years, an advance angle device has been developed.

In the conventional method, the valve timing is designed to be optimum at the rated output of the engine, and the improvement of the illustrated thermal efficiency is remarkable. However, when the engine is under a low load and at a low speed, the piston speed and the intake speed are reduced. The flow rate of the gas is too low to allow sufficient gas exchange in the cylinder. Therefore, a sufficient compression pressure cannot be obtained and the cylinder wall temperature is low, so that a portion of the combustion chamber does not reach the ignition temperature, causing incomplete combustion and lowering the indicated thermal efficiency. It also causes black smoke.

In the cam advancing device, when the cam is moved, for example, when the valve opening angle is increased, the valve closing angle is also increased. Therefore, the time area during which the valve is open does not change, and gas exchange between intake and exhaust in the cylinder depends on the engine load. Is not fully performed. In some cases, increasing the valve lift increases the time area, but this hastens the wear of the valve and valve seat. In this respect, the effect of the valve timing control by the cam advancing device is still insufficient.

The present invention maintains the best combustion state by giving an appropriate intake / exhaust valve opening / closing angle in any load range and rotational speed in an internal combustion engine, thereby improving the illustrated thermal efficiency and reducing the exhaust gas, and the structure is improved. It is intended to provide a simple device.

[0056]

The structure of the cam of the present invention is as follows.
The cam profile (H) changes continuously while the apex (G) of the cam remains constant, and the cam roller (4) having an elliptical cross section capable of accurately contacting and transmitting the cam lift at any position of the cam profile. ) And a camshaft moving device capable of freely moving the camshaft (2) in the axial direction. The cam profile is low engine load (A)
To a high load (B) can be set to a shape having an appropriate time area for all loads. For example, at a low load (A), the valve opening angle is reduced, and at a high load (B), the valve opening angle is increased or the open position (C) and the closed position (D) of each intake / exhaust valve are set to optimal positions. Since the apex (G) of the cam is constant, the head of the valve is constant, and no excessive force is applied to the valve / valve seat. This cam can be moved in the axial direction by a cam shaft moving device to a cam position suitable for the load condition during engine operation.

[0086]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIGS. FIG. 1 is a perspective view of a cam portion of the variable valve opening / closing angle cam device of the present invention. FIG. 2 is a sectional view of a cam profile (H) of the variable cam angle cam device. FIG. 3 is a sectional view of the cam roller portion of the present invention. FIG. 4 is a sectional view taken along line XX of the cam roller portion of the present invention. FIG. 5 is a sectional view of the camshaft moving device of the present invention. FIG. 6 is a sectional view taken along the line YY of the serration portion of the camshaft moving device. FIG. 7 is a schematic configuration diagram showing a state where the camshaft has shifted to the low load side (A). FIG. 8 is a schematic configuration diagram showing a state where the camshaft has shifted to the high load side (B).

The configuration of each part of the variable valve opening / closing angle cam device of the present invention will be described. As shown in FIGS. 1 and 2, the cam (1) has a shape in which the cross section changes continuously in the axial direction.

As shown in FIGS. 3 and 4, the cam roller (4) which comes into contact with the cam and receives the cam lifting force has an elliptical cross section and can be easily attached to the rocker arm (6) at any position of the cam profile (H). Can transmit lift.

In FIGS. 5 and 6, the camshaft moving device moves the camshaft to an arbitrary position while the camshaft (2) is rotating. The camshaft (2) has a serrated fixed hub (2).
4) is attached and rotates together with a serrated pulley (23) driven by a belt (22) to drive the camshaft (2). Pulley with serration (2
3) is a pulley positioning ring (27a) (27
The position in the axial direction is fixed by b).

As shown in FIGS. 5, 7, and 8, when the rack gear (21) is driven by the pinion gear (20), the cam is driven via a thrust bearing (16) mounted on the bearing box (15). The shaft (2) moves and the cam (1) moves with respect to the cam roller (4). At this time, a stopper ring (25) is provided for safety so that the cam shaft (2) does not move excessively.
Install. The camshaft holding spring (12) is the camshaft (2)
Has the effect of always pushing in a certain direction via the thrust ring (14) in order to stabilize the position.

FIG. 7 shows the position of the camshaft (2) when the engine is in a low load state. At this time, the cam (1) acts on the cam roller (4) at the position (A) as shown in FIG. FIG. 8 shows a position where the camshaft (2) is in a high load state of the engine. The rack roller (21) is moved via a thrust bearing (16) to move the cam roller (4) at the position (B) as shown in FIG.
Act on.

[0122]

Next, an embodiment of a variable valve opening / closing angle device will be described. The cam (1) is attached to the camshaft (2) by the key (3) and the fixed hub with serrations (24) is attached by the key (26). Fixed hub with serrations (24)
And a stopper ring (25).

A fixed ring (17) is fixed to the right end of the camshaft (2) with fixing bolts (18), a bearing box (15) equipped with a thrust bearing (16) is fitted and fixed with a bearing box cover (19). . As the thrust bearing (16), an oilless rolling bearing is suitable.

The positioning ring lower part (27) is mounted on the cam bearing (11a).
Attach the positioning ring support bracket lower part (10a) to which a) is attached.

A cam shaft pressing spring (1) is provided at the left end of the cam shaft (2).
2) A spring receiver (13) and a thrust ring (14) are attached and, in this state, mounted on cam bearings (11a) and (11c). The cam shaft (2) is held by the cam bearing covers (11b) and (11d) to which the positioning ring support bracket upper part (10b) is attached.

The cam shaft (2) is connected to the cam bearings (11a) (11).
After holding in step c), the positioning ring upper part (27b) is mounted. The positioning rings (27a) and (27b) hold the position constant so that the pulley with serration (23) does not move in the axial direction even during rotation and stop. The positioning rings (27a) and (27b) allow the pulley with serration (23) to transmit the rotation to the camshaft (2) without being displaced during rotation and to move to the arbitrary position in the axial direction at the same time.

The drive of the pinion gear (20) is preferably controlled by an electric motor, but in another embodiment, hydraulic pressure can be used as a method of driving the rack gear (21).

[0182]

The variable valve opening / closing angle cam device of the present invention is a device which can arbitrarily change the valve opening / closing timing so that the indicated thermal efficiency can be always maintained high according to the load condition of the engine during operation of the engine. That is, in the case of a four-stroke cycle engine, when the load is low, the opening of the exhaust valve may be about 30 degrees to 60 degrees before the bottom dead center. It is necessary to open the exhaust valve earlier. When the intake valve is in the low-speed range, the closing timing may be about 20 to 40 degrees after bottom dead center so as not to let the intake air escape. However, if the closing timing is delayed in the high-speed range, the intake pressure is increased by using the inertia of the intake. be able to. Regarding the valve overlap, in the case of a gasoline engine, at low speeds, the pressure in the intake pipe is low due to throttling adjustment, so if the opening of the intake valve is early, gas backflow will occur. It is better to open earlier for the effect of intake inertia. Therefore, the overlap is advantageous at low speeds and short at high speeds.
In order to perform the cooling function of the combustion chamber, it is preferable that the length be long in a high speed range.
The opening and closing timing of the valve is steplessly changed so that these operations can be performed ideally, and the gas exchange is completely performed in any load range and the amount of intake air can be increased. Therefore, the average effective pressure is increased and the indicated thermal efficiency is improved. In addition, since complete combustion is performed, fuel efficiency can be improved and exhaust gas can be reduced.

[0119]

[Brief description of the drawings]

FIG. 1 is a perspective view of a cam portion according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating a cross-sectional shape of the cam profile according to claim 1 of the present invention.

FIG. 3 is a sectional view of a cam roller portion of the second embodiment of the variable valve opening / closing angle cam device of the present invention.

FIG. 4 is a sectional view of the cam roller according to the second embodiment of the present invention;
It is sectional drawing showing a part.

FIG. 5 is a sectional view of a camshaft moving device according to a third embodiment of the present invention;

FIG. 6 is a sectional view taken along the line YY of the serration portion of the camshaft moving device according to the third embodiment of the present invention;

FIG. 7 is a schematic configuration diagram showing a state in which the variable valve opening / closing angle cam device of the present invention is located on the low speed side.

FIG. 8 is a schematic configuration diagram illustrating a state in which the variable valve opening / closing angle cam device of the present invention is positioned on the high-speed side.

[Explanation of symbols]

1, cam 2, cam shaft 3, key 4, cam roller 5, roller shaft 6, rocker arm 7, rocker arm bearing 8, valve clearance adjusting bolt 9, valve stem 10a. Locating ring support fitting lower part 10b, locating ring support fitting upper part 11a, cam bearing 11b, cam bearing cover 11c, cam bearing 11d, cam bearing cover 12, camshaft holding spring 13, spring receiver 14, thrust ring 15, bearing box 16, Thrust bearing 17, fixed ring 18, fixed bolt 19, bearing box cover 20, pinion gear 21, rack gear 22, belt 23, serrated pulley 24, serrated fixed hub 25, stopper ring 26, key 27a, positioning ring lower 27b , Positioning ring upper part 28, serration A, cam low speed side position B, cam high speed side position D, valve opening start angle E, valve closing end angle G, cam apex H, cam profile M, this distance is always constant N, this distance Is always constant Pl, Ql, cam is driven to low speed side (A) State. The state in which the Ph and Qh cams are driven to the high speed side (B).

Claims (3)

[Claims] 1. A cam device for an internal combustion engine, wherein the cross-sectional area of the cam changes continuously and the opening / closing angle of the valve can be freely changed while the valve lift is constant. 2. A cam roller having an elliptical axial section in contact with the cam of claim 1 and receiving a lift from the cam. 3. A camshaft moving device which drives a camshaft and can move the camshaft in the axial direction while the camshaft is rotating.