JP2022090950A - Variable valve mechanism of internal combustion engine - Google Patents

Abstract

To arbitrarily increase and decrease a length of a valve opening period of an intake valve or an exhaust valve of a cylinder, while eliminating a labor for replacement of a cam shaft, with a simple constitution.SOLUTION: A variable valve mechanism of an internal combustion engine includes: a first cam shaft 1 supporting a first cam 11 for opening and closing an intake valve or an exhaust valve of a cylinder and rotating about a prescribed axial center C; a second cam shaft 2 supporting a second cam 21 for opening and closing the same valve as that opened and closed by the first cam 11 and rotating about the axial center C together with the first cam shaft 1; a first phase variable device 3 for advancing or retarding a relative angle about the axial center C of the first cam shaft 1 with respect to a cam sprocket 31 on which a chain or a belt of a winding transmission device for transmitting engine torque from a crank shaft, is wound; and a second phase variable device 4 for advancing or retarding a relative angle about an axial center C of the second cam shaft with respect to the first cam shaft 1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a variable valve mechanism capable of adjusting the length of the valve opening period together with the opening / closing timing of the intake valve or the exhaust valve of the cylinder of an internal combustion engine.

An internal combustion engine (reciprocating engine) mounted on a vehicle or the like is known to be equipped with a phase-changing variable valve timing mechanism capable of variably controlling the opening / closing timing of the intake valve or the exhaust valve of each cylinder. (See the following patent document). This type of VVT mechanism advances the opening / closing timing of the intake valve or the exhaust valve by changing the rotation phase of the camshaft that drives the opening / closing of the intake valve or the exhaust valve with respect to the crankshaft which is the output shaft of the internal combustion engine. To retard.

Japanese Unexamined Patent Publication No. 2020-084903

When designing and developing an internal combustion engine or controlling operation, there is a desire to arbitrarily increase or decrease the length of the valve opening period of the intake valve or the exhaust valve. For example, in a spark ignition type engine, the valve opening period of the intake valve is set to be relatively long, and the valve overlap state in which both the intake valve and the exhaust valve of the same cylinder open is ensured to keep the combustion chamber of the cylinder. Scaveng and fill the cylinder with a sufficient amount of intake air. On the other hand, in the compression ignition type engine, the valve opening period of the intake valve is set shorter, and the intake valve is closed early while avoiding the valve overlap state to keep the combustion chamber of the cylinder warm. In order to put the so-called Homogeneous Charge Compression Ignition engine into practical use, when the mode of appropriately switching between SI combustion and CI combustion is taken, the optimum valve opening period of the intake valve can be expanded or contracted depending on the time.

In the above-mentioned VVT mechanism, the valve opening timing and the valve closing timing of the intake valve or the exhaust valve of the cylinder can be changed, but the length of the period during which the valve is open cannot be changed. This is because the length of the valve opening period of the intake valve or the exhaust valve is defined by the operating angle (working angle) of the cam lobe that presses the valve lifter or rocker arm attached to the valve body of the valve. In order to change the length of the valve opening period, it was necessary to replace the camshaft in which the cam was integrally molded, and it took considerable cost and man-hours to make a prototype and rearrange the camshaft.

In view of the above, it is an intended object of the present invention to make it possible to arbitrarily expand or contract the length of the valve opening period of the intake valve or the exhaust valve by a simple configuration without the trouble of replacing the camshaft. It is supposed to be.

In the present invention, a first camshaft that supports a first cam for opening and closing an intake valve or an exhaust valve of a cylinder and rotates around a predetermined axis, and the same valve that the first cam drives to open and close. A second camshaft that supports the second cam for opening and closing the engine and rotates around the axis together with the first camshaft, and a chain or belt of a winding transmission device that transmits engine torque from the crankshaft are wound. A first phase variable device that advances or retards the relative angle of the first camshaft around the axis with respect to the camsprocket to be hung, and the axis around the second camshaft with respect to the first camshaft. A variable valve mechanism of an internal combustion engine including a second phase variable device for advancing or retarding the relative angle of the camshaft is constructed.

According to the present invention, the length of the valve opening period of the intake valve or the exhaust valve of the cylinder can be arbitrarily expanded or contracted with a simple configuration. Therefore, there is no need to replace the camshaft.

The perspective view of the variable valve mechanism of one Embodiment of this invention. Sectional drawing of the variable valve mechanism of the same embodiment. An exploded perspective view of the camshaft of the variable valve mechanism of the same embodiment. An enlarged cross-sectional view of a main part explaining the operation of the variable valve mechanism of the same embodiment. An enlarged cross-sectional view of a main part explaining the operation of the variable valve mechanism of the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. 1 to 5 show the variable valve mechanism of the internal combustion engine of the present embodiment. This variable valve mechanism opens and closes the intake valve or exhaust valve of each cylinder of a 4-stroke reciprocating engine that includes multiple cylinders, and variablely controls the opening and closing timing of the intake valve or exhaust valve as well as the length of the valve opening period. can do. The illustrated example is a variable valve mechanism applied to an in-line three-cylinder internal combustion engine having two intake valves and an exhaust valve per cylinder.

This variable valve mechanism includes a first camshaft (outer camshaft) 1 that supports a first cam (outer cam) 11 for opening and closing an intake valve or an exhaust valve of each cylinder, and an intake valve or an exhaust of each cylinder. The second camshaft 2 (inner camshaft) 2 that supports the second cam (inner cam) 21 for opening and closing the valve, and the first phase that changes the rotation phase of the first camshaft 1 and the second camshaft 2. The variable device 3 and the second phase variable device 4 that changes the rotation phase of only the second camshaft 2 are the main components.

The first camshaft 1 is a tubular body extending along the axis C direction. The second camshaft 2 is a rod-shaped body extending along the axis C direction, and is inserted into the first camshaft 1. Both the first camshaft 1 and the second camshaft 2 are driven by the crankshaft, which is the output shaft of the internal combustion engine, and rotate about the same axis C.

The first cam 11 is integrally molded with the first cam member 10 fixed to the first cam shaft 1. The first cam member 10 is separate from the first camshaft 1, the second camshaft 2, and the following second cam member 20. As shown in FIG. 3, the first cam 11 projects outward from one end of the base of the cylindrical first cam member 10 in the radial direction orthogonal to the axis C. The first cam 11 includes a cam lobe and a base circle that press the valve lifter or rocker arm attached to the valve body of the intake valve or the exhaust valve. There are two first cam members 10 and two first cams 11 for one cylinder of the internal combustion engine. In a three-cylinder internal combustion engine, the total number of the first cam member 10 and the first cam 11 is six, respectively.

The second cam 21 is integrally molded with the second cam member 20 fixed to the second cam shaft 2. The second cam member 20 is separate from the first camshaft 1, the first cam member 10, and the second camshaft 2. As shown in FIG. 3, the second cam 21 projects radially outward from both ends of the base of the cylindrical second cam member 20. The second cam 21 also includes a cam lobe and a base circle that press the valve lifter or rocker arm attached to the valve body of the intake valve or the exhaust valve. As shown in FIGS. 4 and 5, the profile of the second cam 21, that is, the shape and dimensions of the cam lobe and the base circle as viewed from the axial center C direction are the same as or substantially the same as those of the first cam 11. In particular, in the first cam 11 and the second cam 21, the cam nose (the height of the apex of the cam peak) and the operating angle α are equal to or substantially equal to each other. There is one second cam member 20 for one cylinder of the internal combustion engine, and two second cams 21 for one cylinder. In a three-cylinder internal combustion engine, the total number of second cam members 20 is three, and the total number of second cams 21 is six.

As shown in FIGS. 1 and 2, when assembling the first cam member 10 and the second cam member 20, the first cam is inserted into each shaft hole of the base of each cam member 10 and 20 and the cylindrical journal member 5. The cam members 10, 20 and the journal member 5 are fitted onto the first camshaft 1 by inserting the shaft 1 and the second camshaft 2. At this time, the first cam members 10 are adjacent to each other on both sides of the second cam member 20 along the axis C direction, and the two first cam members 10 are arranged so as to sandwich one second cam member 20. ..

In this variable valve mechanism, a set of two first cam members 10 and one second cam member 20 in between is two intake valves or two intake valves provided in one cylinder of an internal combustion engine. It works as a valve operating system that opens and closes the exhaust valve. The second cam 21 at one end of the second cam member 20 and the first cam 11 at the end of the first cam member 10 adjacent thereto are the same intake valve or the same intake valve on one side of the cylinder. The exhaust valve is opened and closed. The second cam 21 at the other end of the second cam member 20 and the first cam 11 at the end of the first cam member 10 adjacent thereto are the same intake valve or the same intake valve on the other side of the cylinder. The exhaust valve is opened and closed.

The journal member 5 supported by the cylinder head of the internal combustion engine is located between the first cam member 10 corresponding to a certain cylinder and the first cam member 10 corresponding to another cylinder.

By penetrating the pin 12 into the substrate of the first cam member 10 and the peripheral wall of the first camshaft 1, the first cam member 10 is fixed to the first camshaft 1. The first cam member 10 is integrated with the first cam shaft 1 and rotates about the axis C.

In addition, the second cam member 20 is fixed to the second camshaft 2 by penetrating the pin 22 into the substrate of the second cam member 20 and the second camshaft 2. The second cam member 20 is integrated with the second cam shaft 2 and rotates about the axis C. The first camshaft 1 is previously provided with an elongated hole 13 that penetrates the peripheral wall and extends along the circumferential direction around the axis C. The pin 22 for fixing the second cam member 20 to the second camshaft 2 fits in the elongated hole 13, and the second cam member 20 is fastened to the second camshaft 2 through the elongated hole 13.

The first camshaft 1 and the second camshaft 2 receive engine torque from the crankshaft of the internal combustion engine and rotate around the axis C. A cam sprocket 31 and a first phase variable device 3 are arranged on one end side thereof. The cam sprocket 31 constitutes a winding transmission device together with the crank sprocket fixed to the crankshaft. A timing chain or belt is wound around the cam sprocket 31 and the crank sprocket, and engine torque is transmitted from the crank sprocket to the cam sprocket 31 and eventually to the camshafts 1 and 2 via the chain or belt.

The first phase variable device 3 can rotate the first camshaft 1 around the axis C with respect to the cam sprocket 31 within a finite angle, and the first camshaft 1 is relative to the cam sprocket 31. It is possible to maintain the angle (or posture) around the axis C at an arbitrary position. One end of the first camshaft 1 is housed in the housing (or body) of the first phase variable device 3. As the first phase variable device 3, that of a known VVT mechanism of an internal combustion engine can be adopted. That is, even if the phase variable device 3 is a vane type VVT mechanism in which the lubricating oil (engine oil) of the internal combustion engine is used as a working fluid and the rotation phase of the first camshaft 1 with respect to the cam sprocket 31 is displaced by the lubricating oil. Alternatively, it may be a motor drive VVT mechanism that is displaced by an electric motor of the first camshaft 1 with respect to the cam sprocket 31.

A coupling 14 and a second phase variable device 4 are arranged on the other end side of the first camshaft 1 and the second camshaft 2. The coupling 14 is fixed to the other end of the first camshaft 1.

The second phase variable device 4 can rotate the second camshaft 2 around the axis C within a finite angle with respect to the coupling 14, and the second camshaft 2 is relative to the coupling 14. It is possible to maintain the angle (or posture) around the axial center C at an arbitrary position. The other end of the second camshaft 2 is housed in the housing (or body) of the second phase variable device 4. Similar to the first phase variable device 3, the second phase variable device 4 can adopt that of a known VVT mechanism. That is, the phase variable device 4 may be a vane type VVT mechanism that displaces the rotational phase of the second camshaft 2 with respect to the coupling 14 by the lubricating hydraulic pressure, and displaces the rotation phase of the second camshaft 2 with respect to the coupling 14 by the motor of the second camshaft 2. It may be a motor drive VVT mechanism.

As a whole, the first camshaft 1 (and the first cam 11) and the second camshaft 2 (and the second cam 21) that rotate in accordance with the crankshaft by the first phase variable device 3 with respect to the crankshaft. The relative rotation phase can be variably controlled. The first camshaft 1 and the second camshaft 2 can rotate integrally via the second phase variable device 4. By changing the rotational phase of the first cam 11 and the second cam 21 with respect to the crankshaft, the opening / closing timing of the intake valve or the exhaust valve of each cylinder is advanced or retarded with the known VVT mechanism of the internal combustion engine. It is the same.

Then, the first camshaft 1 (and the first cam 11) of the second camshaft 2 (and the second cam 21) that is driven by the first camshaft 1 and rotates by the second phase variable device 4 ) Can be variably controlled relative to the rotation phase. This means that the angle (or attitude) around the axis C relative to one of the first cam 11 and the second cam 21 that drives the opening and closing of the same single intake valve or exhaust valve can be variably controlled. do. That is, as shown in FIG. 4, if the second cam 21 is superposed on the first cam 11 adjacent to each other along the axis C direction, the substantially operating angle A of the cams 11 and 12 as a whole is realized. In other words, the valve opening period of one valve driven by these cams 11 and 12 can be minimized. On the other hand, as shown in FIG. 5, if the second cam 21 adjacent to the first cam 11 is deviated around the axis C, the substantially operating angle of the cams 11 and 12 as a whole is substantial. A can be expanded beyond the operating angle α of the cams 11 and 12 themselves, and the valve opening period of one valve driven by these cams 11 and 12 can be further extended.

In the present embodiment, the first camshaft 1 that supports the first cam 11 for opening and closing the intake valve or the exhaust valve of the cylinder and rotates around a predetermined axis C, and the first cam 11 are driven to open and close. A second camshaft 2 that supports the second cam21 for opening and closing the same valve and rotates around the axis C together with the first camshaft 1, and a winding that transmits engine torque from the crankshaft. The first phase variable device 3 for advancing or retarding the relative angle of the first camshaft 1 around the axis C with respect to the cam sprocket 31 around which the chain or belt of the hanging transmission device is wound, and the first. A variable valve mechanism of an internal combustion engine including a second phase variable device 4 for advancing or retarding a relative angle of the second camshaft 2 around the axis C with respect to the camshaft 1 is configured. According to this embodiment, it is possible to arbitrarily and continuously change the length of the valve opening period of the intake valve or the exhaust valve of the cylinder.

When evaluating the output performance, etc. by changing the length of the valve opening period in the field of research and development of an internal combustion engine, the camshaft had to be replaced before, and the cost and rearrangement of the camshaft were costly. It took a lot of work. In the variable valve mechanism of the present embodiment, it is not necessary to replace the camshafts 1 and 2 assembled to the internal combustion engine in order to change the length of the valve opening period of the valve, and such costs and man-hours can be saved. ..

Assuming an internal combustion engine that appropriately switches between SI combustion and CI combustion, in CI combustion, the valve overlap period in which both the intake valve and the exhaust valve of the same cylinder open is shortened or set to 0, and the intake valve is closed. To keep the combustion chamber temperature of the cylinder as high as possible. On the other hand, in SI combustion, the valve overlap period is further extended to scaveng the combustion chamber of the cylinder.

If the cam nose of the first cam 11 and the cam nose of the second cam 21 that open and close the same valve are equivalent, only the valve opening period should be expanded or contracted without changing the valve lift amount of the intake valve or the exhaust valve. Can be done.

If this variable valve mechanism is applied to a conventional internal combustion engine that exclusively performs SI combustion, the length of the valve opening period can be variably controlled without excessively increasing the valve lift amount of the intake valve or the exhaust valve. The amount of air sucked into the cylinder (and the amount of fuel injection) can be appropriately increased or decreased to improve the output performance. It is also possible to reduce the actual operating angle A of both cams 11 and 12 (advance the closing timing of the intake valve) and carry out Miller cycle (Atkinson cycle) operation that closes the intake valve during the intake stroke of the cylinder. can. As a result, in a port injection type internal combustion engine, it is possible to prevent the air-fuel mixture containing unburned fuel from blowing through from the intake passage to the exhaust passage without staying in the combustion chamber of the cylinder, and the throttle loss due to the throttle valve can be reduced. It also leads to.

A ready-made phase variable VVT mechanism can be used for the phase variable devices 3 and 4, and the control thereof is easy.

The present invention is not limited to the embodiment described in detail above. The specific configuration of each part can be variously modified without departing from the spirit of the present invention.

The present invention can be used for an internal combustion engine mounted on a vehicle or the like.

1 ... 1st camshaft 11 ... 1st cam 2 ... 2nd camshaft 21 ... 2nd cam 3 ... 1st phase variable device 31 ... Cam sprocket 4 ... 2nd phase variable device C ... Axial center

Claims (1)

A first camshaft that supports the first cam for opening and closing the intake valve or exhaust valve of the cylinder and rotates around a predetermined axis, and
A second camshaft that supports the second cam for opening and closing the same valve that the first cam drives to open and close, and rotates around the axis together with the first camshaft.
A first phase variable device that advances or retards the relative angle around the axis of the first camshaft to the cam sprocket on which the chain or belt of the winding transmission that transmits engine torque from the crankshaft is wound. When,
A variable valve mechanism of an internal combustion engine including a second phase variable device for advancing or retarding a relative angle of the second camshaft around the axis with respect to the first camshaft.

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