JP2878252B2 - Engine valve gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a double overhead camshaft (DOHC) engine valve train.

[0002]

2. Description of the Related Art In a so-called DOHC engine in which an intake / exhaust valve arranged on a cylinder head of an engine is opened and closed by two camshafts arranged above a cylinder head, for example, a so-called DOHC engine is disclosed. 9
As described in Japanese Patent Publication No. 501, only one camshaft (first camshaft) is provided with a driving sprocket (pulley in the case of belt drive), and the other camshaft (second camshaft) is Driving via a gear that connects the camshaft has conventionally been performed. According to such a configuration, the distance between the camshafts can be reduced as compared with a case where the two camshafts are separately driven, and the valve train is compact.

[0003]

In the meantime, there is a demand for the engine to make the intake and exhaust timing variable depending on the operating condition. This is because the engine performance can be improved by changing, for example, the amount of overlap of the intake and exhaust strokes according to the engine speed.

As a mechanism for varying the valve timing, for example, a phase variable means using a helical spline or the like is provided between a driving pulley for transmitting rotation from a crankshaft and a camshaft, and this mechanism is provided by hydraulic pressure or the like. It is conceivable to operate the phase changing means to change the phase of the camshaft. However, a driving pulley is provided on the first camshaft as described in Japanese Utility Model Laid-Open Publication No.
In a valve gear that transmits rotation to a camshaft by a connecting gear, simply providing the above-described phase variable means between a driving pulley and a camshaft simultaneously forms one camshaft with the other. Since the phase of the camshaft also changes in the same direction, it is impossible to change the amount of overlap. Therefore, when the overlap amount between the respective camshafts is to be changed in such a valve train, a phase variable mechanism may be separately provided between the first camshaft and the second camshaft, or the second camshaft may be provided. It is conceivable to separately provide a phase variable mechanism between the rotating body on the side and the shaft portion of the second camshaft. However, even if any of these structures is adopted, the distance between the shafts of the respective camshafts is reduced. However, the advantage of the above-described valve train that the head area can be made compact can be impaired.

As described above, in a valve train having a structure in which the distance between the camshafts can be reduced and the circumference of the head can be made compact, the amount of overlap between the camshafts can be changed without impairing the advantages. Making it possible has been difficult in the past.

It is therefore an object to reduce the distance between the camshafts so that the head can be made compact and the amount of overlap between the camshafts can be changed. The purpose of the present invention is
It is to solve this problem.

[0007]

An engine valve operating apparatus according to the present invention includes a first camshaft for opening and closing one of an intake valve and an exhaust valve, and a first camshaft provided in parallel with the first camshaft. A second camshaft that opens and closes one of the valves; and a second camshaft that is fitted to an end of the first camshaft to receive a rotational driving force of an engine output shaft and apply the rotational driving force to the first camshaft. A first rotation transmitting wheel to be transmitted and a second rotation transmitting wheel which is disposed on the shaft of the first camshaft in a fitted state and transmits the driving force of the engine output shaft received by the first rotation transmitting wheel to the second camshaft. 2 and a rotation transmitting wheel, which is disposed on the shaft of the first camshaft so as to fit therewith,
And a phase varying means for varying a mutual rotational phase between the first rotation transmission wheel and the second rotation transmission wheel. In this case, the rotational driving force of the engine output shaft is transmitted from the first rotation transmission wheel to the first camshaft. Further, the driving force received by the first rotation transmission wheel is transmitted to the second camshaft via the second rotation transmission wheel. At this time, for example, by operating the phase variable mechanism with hydraulic pressure, the mutual rotation phase of the first rotation transmission wheel and the second rotation transmission wheel changes. Thereby, the rotation phase of the second camshaft can be changed. In addition, since the transmission mechanism including the first rotation transmission wheel, the second rotation transmission wheel, and the phase varying means is disposed only on the first camshaft side, the distance between the first camshaft and the second camshaft is reduced. Expansion can be suppressed.

Further, in this valve gear, a cylindrical connecting member extending to a position overlapping with the first rotation transmission wheel while being fitted on the shaft of the first camshaft is integrated with the second rotation transmission wheel. It is preferable that the phase change means is disposed between the connecting member and the first rotation transmission wheel. By extending the connecting member integrally connected to the second rotation transmission wheel to a position overlapping with the first rotation transmission wheel in this way, and disposing the phase changing means inside the first rotation transmission wheel, Each of the rotation transmission wheels, the second rotation transmission wheels, and the phase varying means is compactly set without any restriction on the distance between the camshafts while being set to any size without considering mutual overlap. A valve train can be configured.

It is preferable that the phase changing means is constituted by a helical spline. For example, when the driving portion of the camshaft is separated into a housing portion and a vane portion, and the phase variable mechanism is directly driven in the rotation direction, such as a vane type variable phase mechanism that forms a hydraulic chamber with the housing and the vane, Due to the inertia of the rotating body, the tappet reaction force of the camshaft at the time of valve operation becomes large, and the phase change occurs due to the reaction force in the rotating direction at this time, but the phase variable means is a helical spline. Then, since the reaction force at the time of valve operation is received by the spline, the fluctuation of the phase can be reduced and the control accuracy can be improved.

In the valve gear according to the present invention, for example, the first rotation transmission wheel is preferably a pulley and the second rotation transmission wheel is preferably a gear, so that the transmission is constituted by the chain and the sprocket. Therefore, a more compact configuration can be realized, and the amount of backlash is small, so that control accuracy can be improved.

In this valve gear, the first and second camshafts are, for example, the first camshaft is an exhaust-side camshaft and the second camshaft is an intake-side camshaft.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a valve train according to the present invention will be described below with reference to the drawings.

FIG. 1 is an overall view of a valve train according to the present invention.

This valve train has two intake and exhaust sides.
The camshafts 1 and 2 are provided. A cylindrical spacer 3 is fixed to an end of the exhaust-side camshaft 2, and a driving pulley 4 is mounted outside the spacer 3. One end of a cylindrical connecting member 6 rotatably mounted on the exhaust camshaft 2 is inserted into the base end of the boss 5 of the pulley 4. The relative movement of the pulley 4 and the connecting member 6 in the axial direction is restricted by a retainer ring 7 mounted between the boss 5 and the connecting member 6. The pulley 4 and the connecting member 6 are free in the rotation direction. A first gear 8 is spline-coupled to the other end of the connecting member 6 and fixed by a lock nut 9. The first gear 8 has a second gear fixed to the tip of the intake side camshaft 1.
The gear 10 is meshed and connected.

A straight spline 11 is formed on the inner circumference of the pulley 4 on the tip end side of the boss portion 5.
A helical spline 12 is formed on the inner periphery of the end of the connecting member 6 inserted into the connecting member 6. On the other hand, a helical spline 13 is formed on the outer periphery of the spacer 3 in a direction opposite to the helical spline 12 on the inner periphery of the connecting member 6. A helical spline fitted on the inner periphery of the boss portion 5 of the pulley 4 and a helical spline 12 fitted on the inner periphery of the connecting member 6 is provided on the outer periphery of the central portion. An annular piston 17 having a helical spline 16 fitted on the outer periphery of the spacer 3 on the inner periphery of the central portion is mounted between the spacer 3 and the pulley 4 and the connecting member 6. I have. Piston 17
Is urged to the distal end side by a return spring 19 mounted between the connecting member 6 and the inner stepped portion 18. An oil passage 20 is formed in the exhaust side camshaft 2 along the axis. The cylindrical spacer 3 is fixed to the exhaust-side camshaft 2 by a fixing bolt 22 via a stopper 21. The fixing bolt 22 has an axial through-hole 23 communicating with the oil passage 20.

At the tip of the boss 5 of the pulley 4, a piston 1
A pressure chamber 24 for guiding the oil pressure from the oil passage 20 is formed facing the head of the head 7. Oil pressure is supplied to the pressure chamber 24 via the oil passage 20 and the return spring 19
When the piston 17 is moved in the axial direction by compressing the piston, the spacer 3 and the connecting member 6 which are spline-connected to the helical splines 16 and 15 formed on the inner and outer circumferences of the piston 17 in the opposite direction are indicated by broken lines in FIG. As shown by, the phase is shifted in the opposite directions to the piston 17. Thereby, the phase of the exhaust side camshaft 2 changes with respect to the pulley 4 rotating in the same phase as the piston 17, while the side of the intake side camshaft 1 is connected via a pair of gears 10 and 9. It is drivingly connected to the member 6, so that the phase of the pulley 4 changes in a direction opposite to that of the exhaust camshaft 2.

In this valve gear, when the engine is running at high speed, the hydraulic pressure is turned on, so that the exhaust valve closing timing shifts to the lag side and the intake valve opening timing shifts to the advance side as shown in FIG. .

In this example, as described above, the driving pulley 4
By using the space between the boss portion 5 and the spacer 3 to arrange the annular piston 17 having the helical splines 16 and 15 and the straight spline 14 in the opposite directions, a phase variable mechanism is configured. The valve train does not increase in size.

In the above example, the drive cam pulley is provided on the exhaust side camshaft.
The present invention can be similarly applied to a configuration in which a pulley is provided on the intake side camshaft.

[0020]

According to the present invention, a first rotation transmitting wheel for transmitting the rotational driving force of the engine output shaft to the first camshaft, and a driving force for transmitting the driving force from the first rotation transmitting wheel to the second camshaft. A mechanism for changing the rotation phase of the second camshaft by changing the mutual rotation phase with the second rotation transmission wheel.
The first camshaft and the second camshaft can be made compact without increasing the distance between the axes.

A connecting member integrally connected to the second rotation transmission wheel is extended toward the first rotation transmission wheel, and a phase variable means is provided between the first rotation transmission wheel and the connection member at a position where the connection member overlaps with the first rotation transmission wheel. The compactness can be improved by arranging.

Further, by constituting the phase variable means by a helical spline, it is possible to make the rotation resistant even in a compact size and to enhance the control accuracy.

Further, by using the first rotation transmission wheel as a pulley and the second rotation transmission wheel as a gear, it is possible to enhance control accuracy while improving compactness.

[Brief description of the drawings]

FIG. 1 is an overall view of an example of a valve train according to the present invention.

FIG. 2 is an operation explanatory view of the valve operating device.

FIG. 3 is an explanatory diagram of valve timing in the valve operating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intake side camshaft 2 Exhaust side camshaft 3 Spacer 4 Driving pulley 6 Connecting member 8 1st gear 10 2nd gear 11,14 Straight spline 12,13,15,16 Helical spline 17 Piston 20 Oil passage 24 Pressure chamber

Continuation of the front page (56) References JP-A-60-153411 (JP, A) JP-A-62-185809 (JP, U) JP-A-61-27908 (JP, U) JP-A-63-112 (JP, U) , U) Shokai Sho 955-1001 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F01L 1/34

Claims (6)

(57) [Claims] A first camshaft that opens and closes one of an intake valve and an exhaust valve; and a second camshaft that is provided in parallel with the first camshaft and opens and closes one of the intake valve and the exhaust valve. Is disposed in a state of being fitted to an end of the first camshaft;
A first rotation transmission wheel that receives a rotational driving force of an engine output shaft and transmits the rotational driving force to the first camshaft; and a first rotation transmitting wheel that is fitted on the shaft of the first camshaft;
A second rotation transmission wheel for transmitting the driving force of the engine output shaft received by the first rotation transmission wheel to the second camshaft; and a second rotation transmission wheel fitted on the shaft of the first camshaft. ,
An engine valve actuating device comprising: a phase varying means for varying a mutual rotational phase between the first rotation transmission wheel and the second rotation transmission wheel. 2. A cylindrical connection member extending to a position where the second rotation transmission wheel overlaps with the first rotation transmission wheel while being fitted on an axis of the first camshaft and integrally connected to the second rotation transmission wheel. 2. The valve train of an engine according to claim 1, wherein said variable phase means is provided between said first rotation transmission wheel and said connecting member. 3. The valve train of an engine according to claim 1, wherein said variable phase means is constituted by a helical spline. 4. The valve train according to claim 1, wherein the first camshaft is a camshaft for opening and closing an exhaust valve, and the second camshaft is a camshaft for opening and closing an intake valve. 5. A first camshaft for opening and closing one of an intake valve and an exhaust valve, and a second camshaft arranged in parallel with the first camshaft for opening and closing one of the intake valve and the exhaust valve. Is disposed in a state of being fitted to an end of the first camshaft;
A pulley that receives the rotational driving force of the engine output shaft and transmits the rotational driving force to the first camshaft; and a pulley that is fitted on the shaft of the first camshaft;
A gear for transmitting the driving force of the engine output shaft received by the pulley to the second camshaft; and a gear fitted on the shaft of the first camshaft;
An engine valve operating device comprising: a phase changing means for changing a mutual rotation phase between the pulley and the gear. 6. The valve train according to claim 5, wherein the first camshaft is a camshaft for opening and closing an exhaust valve, and the second camshaft is a camshaft for opening and closing an intake valve.