Patent Application
20100242878
1. Field of the Invention
The present invention relates to a variable valve apparatus for an internal combustion engine which makes it possible to change drive phases and valve lifts of an air intake valve, an exhaust valve, and the like. 2. Description of the Related Art
In an internal combustion engine such as an automobile engine, a variable valve apparatus is known which changes drive phases and lifts of intake/exhaust valves depending on driving states of the internal combustion engine to purify an exhaust gas discharged from the engine or to reduce a fuel consumption of the automobile.
As the variable valve apparatus, a variable valve apparatus having a continuous variable rocker arm mechanism is known in which a third arm is arranged between a first arm which drives a valve and a second arm caused to oscillate by a cam, the valve is driven through the third arm, and a fulcrum of oscillation of the second arm is displaced to continuously change the phase and lift of the valve (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2004-339079).
The variable valve apparatus having the continuous variable rocker arm mechanism adjusts the lift and phase of a valve to purify an exhaust gas and adjusts an opening valve angle to make it possible to improve a fuel consumption.
On the other hand, a variable valve apparatus having a switching rocker arm mechanism is known in which a mechanism which selectively transmits displacement is arranged between the first arm which drives the valve and the second arm caused to oscillate by the cam to operate or stop the first arm (for example, see Jpn. Pat. Appin. KOKAI Publication No. 2005-105953).
The variable valve apparatus having the switching rocker arm mechanism performs internal EGR by opening an exhaust valve in an intake stroke to make it possible to purify an exhaust gas and opens the exhaust valve at a compression top dead center to make it possible to apply the engine braking.
However, the variable valve apparatus as described above must select any one of a switching rocker arm mechanism 40 and a continuous variable rocker arm mechanism 50, and can exert only one of the functions of the mechanisms. Furthermore, although the switching rocker arm mechanism 40 can be instantaneously operated, the switching rocker arm mechanism 40 cannot be finely adjusted in lift and phase of the valve. On the other hand, although the continuous variable rocker arm mechanism 50 can be finely adjusted in lift and phase, the continuous variable rocker arm mechanism 50 requires about one second for an operation and has poor responsiveness.
Therefore, it is an object of the present invention to provide a variable valve apparatus for an internal combustion engine which can execute internal EGR and apply engine braking and can simultaneously exert a plurality of functions such as improvement in fuel consumption and purification of an exhaust gas.
In order to solve the problem and achieve the object, the variable valve apparatus for an internal combustion engine of the present invention has the following configuration.
A variable valve apparatus for an internal combustion engine, comprises a cam shaft arranged to be rotatable on a cylinder head of the internal combustion engine; a rocker shaft arranged to be capable of oscillation in the internal combustion engine; a continuous variable rocker arm mechanism which is driven by a cam formed on the cam shaft, opens or closes at least one of an air intake valve and an exhaust valve, and continuously makes a lift of the valve variable; and a switching rocker arm mechanism which is driven by the cam formed on the cam shaft, opens or closes at least one of the air intake valve and the exhaust valve, and switches the lift of the valve in a stepwise manner.
As shown in
The variable valve apparatus 20 is a valve operation apparatus which opens/closes valves of an internal combustion engine. One pair of variable valve apparatuses 20 is arranged to sandwich the cylinder 11. Since the one pair of variable valve apparatuses 20 has a structure symmetrical with reference to the cylinder 11, only the variable valve apparatus 20 on the exhaust valves 14 and 15 side will be explained, and an explanation of the variable valve apparatus 20 on the air intake valves 12 and 13 side is not explained.
The cylinder head 10 comprises one pair of cam shafts 21 arranged to be rotatable, one pair of rocker shafts 30 arranged to be capable of oscillation, one pair of switching rocker arm mechanisms 40 which are driven by a cam 22 formed on the cam shaft 21 and open and close the air intake valves 12 and 13 and the exhaust valves 14 and 15 and switch lifts of the air intake valves 12 and 13 and the exhaust valves 14 and 15 in a stepwise manner, and one pair of continuous variable rocker arm mechanisms 50 which are driven by a cam 23 formed on the cam shaft 21 and open and close the air intake valves 12 and 13 and the exhaust valves 14 and 15 and continuously make the lifts variable. The switching rocker arm mechanisms 40 and the continuous variable rocker arm mechanisms 50 share a rocker arm 60.
The cam shafts 21 and the rocker shafts 30 are connected to a crank shaft (not shown) of an internal combustion engine through a cam chain, gears, and the like. When the crank shaft is rotated, the cams 22 and 23 having different cam profiles are rotationally driven in a direction indicated by an arrow R. The cams 22 and 23 drive the variable valve apparatus 20 at a predetermined timing described later.
An oil path 31 to which engine oil is supplied is arranged inside the rocker shaft 30. An oil pressure supply mechanism 80 which supplies the engine oil to the oil path 31 is connected to the oil path 31. The rocker shaft 30 comprises a drive mechanism 90 which controls a rotational angle position about a shaft center line of the rocker shaft 30. Furthermore, a notch 32 is formed in the rocker shaft 30 at a position corresponding to the continuous variable rocker arm mechanism 50.
With reference to
In the switching rocker arm 41, a boss portion 41a supported by the rocker shaft 30 to be capable of oscillation is formed; a strike arm 41b which projects upwardly from the boss portion 41a, enters a window portion 71b of a vertical piston structure 70 serving as a transmission mechanism described later, and retreats from the window portion 71b is formed; and a roller 41c capable of oscillation is formed. When the roller 41c is brought into contact with the cam 22 to rotate the cam 22, the switching rocker arm 41 is caused to oscillate by using a shaft center line of the rocker shaft 30 as a fulcrum. A trench 41d is formed in the switching rocker arm 41.
Reference number 42 in
The shared rocker arm 60 comprises a boss portion 61 fitted in the rocker shaft 30 portion to be capable of oscillation, arms 62 and 63 extending from the boss portion 61 to the exhaust valves 14 and 15, and a pressed portion 64 pressed by a pressing portion 53b described later. In the boss portion 61, a flow path 61a which guides the engine oil from the oil path 31 is formed.
In the boss portion 61, as a transmission mechanism to selectively transmit displacement from the switching rocker arm 41 to the shared rocker arm 60, the cylindrical vertical piston structure 70 is arranged. The vertical piston structure 70 comprises a storage tube 71 having a hollow portion 71a continuing to an internal surface of the boss portion 61 and the window portion 71b on the side surface, a lid member 72 which blocks an upper-end opening of the hollow portion 71a of the storage tube 71, a piston 73 reciprocatingly stored in the hollow portion 71a, and a spring 74 arranged on the lid member 72 to bias the piston 73 on the boss portion 61 side. A notch 73a is formed in the piston 73. The notch 73a is generally set such that the notch 73a is located at a position of the window portion 71b by the operation of the spring 74. When oil pressure is applied by the oil pressure supply mechanism 80, engine oil is supplied from the oil path 31 to the hollow portion 71a to compress the spring 74 and push up the piston 73. In this manner, a circumference of the piston 73 is exposed to the window portion 71b. In contrast to this, when the oil pressure is released, the piston 73 is pushed down by the operation of the spring 74. An on/off operation of the oil pressure can be instantaneously performed.
The strike arm 41b is arranged to face the window portion 71b. The strike arm 41b is formed to have a shape such that the strike arm 41b idly moves in the notch 73a when the notch 73a is positioned at the window portion 71b and moves while being struck on the circumference portion of the piston 73 when the circumference portion is positioned at the window portion 71b.
In this manner, in the structure, when the strike arm 41b of the switching rocker arm 41 is not struck on the piston 73, cam displacement from the switching rocker arm 41 is not transmitted to the shared rocker arm 60. When the strike arm 41b is struck on the piston 73, the cam displacement from the switching rocker arm 41 opens the exhaust valves 14 and 15 through the shared rocker arm 60. An oil discharge chamber 32 having a width larger than that of the flow path 61a is formed in the rocker shaft 30 on the downstream side of the oil path 31, so that the engine oil can be supplied to the hollow portion 71a even when the position of the flow path 61a is changed by oscillation of the rocker shaft 30 itself or oscillation of the switching rocker arm 41 with rotation of the cam 22. The width of the oil discharge chamber 32 is preferably larger than a distance of oscillation of the switching rocker arm 41 and preferably set to a width at which the engine oil can be supplied to the flow path 61a even when the rocker shaft 30 reaches the position of maximum oscillation.
Furthermore, an oil supply chamber 75 having a width larger than that of the flow path 61a is formed in the vertical piston structure 70 on an upstream side of the hollow portion 71a. Even when the switching rocker arm 41 is caused to oscillate with rotation of the cam 22 to change the position of the flow path 61a, the engine oil can be supplied to the hollow portion 71a. The width of the oil supply chamber 75 is preferably larger than a distance of oscillation of the switching rocker arm 41.
The continuous variable rocker arm mechanism 50 will be explained with reference to
The intermediate arm 51 comprises an annular shaft fitting portion 51a and a pressing portion 51b projecting from the shaft fitting portion 51a in a radial direction. A roller 51c is arranged on the pressing portion 51b. When the intermediate arm 51 is caused to oscillate about the rocker shaft 30, the pressing portion 53b presses the pressed portion 64 of the shared rocker arm 60, and the shared rocker arm 60 opens the exhaust valves 14 and 15.
The continuous variable arm 53 comprises a connection member 54 which connects the continuous variable arm 53 and the rocker shaft 30. The connection member 54 is a stud bolt, has a spherical universal coupling 54a on one end side thereof, is screwed into a screw hole 33 formed in the notch 32 of the rocker shaft 30, and is fixed by a lock nut 54b. When the connection member 54 is fixed to the rocker shaft 30, the universal coupling 54a functions as the fulcrum Q.
Reference number 55 in
The continuous variable arm 53 is formed to have an almost laterally-facing U shape in a side view. A laterally-facing U-shaped base end 53a is formed on a lower side in
On the continuous variable arm 53, a roller 53d is arranged to be capable of oscillation at an intermediate position between the base end 53a and the contact portion 53b. When the roller 53d is brought into contact with the cam 23 and the cam 23 is rotated, the continuous variable arm 53 is caused to oscillate by using the center of the universal coupling 54a as a fulcrum.
Reference number 56 in
The transmission surface portion 56b is formed such that a distance between the transmission surface portion 56b and the slide surface portion 56a has a predetermined value along the slide surface portion 56a . More specifically, the transmission surface portion 56b is formed such that, when the transformation member 56 is slidably moved along an arc-like lower surface of the pad 57, a member being in contact with the transmission surface portion 56b at a predetermined position makes a predetermined motion in a direction perpendicular to the pad 57 with the movement of the transformation member 56.
A trench 56c is formed in the transmission surface portion 56b, and the moving portion 55b of the torsion coil spring 55 is engaged in the trench 56c. When the moving portion 55b is engaged in the trench 56c, the torsion coil spring 55 biases the transformation member 56 such that the transformation member 56 moves to the continuous variable arm 53 side.
Furthermore, a semi-cylindrical joint 57 is arranged between the transformation member 56 and the contact portion 53b of the continuous variable arm 53. The joint 57 is attached to the contact portion 53b of the continuous variable arm 53 and slidably fitted on the transformation member 56. The joint 57 is designed to absorb a change in a contact angle between the transformation member 56 and the contact portion 53b and to transmit a pressing operation of the continuous variable arm 53 to the transformation member 56.
An operation of the continuous variable rocker arm mechanism 50 will be explained with reference to
The base end 53a is pulled to the left by the universal coupling 54a, and the continuous variable arm 53 moves to the left as a whole. On the other hand, the transformation member 56 is biased by the torsion coil spring 55 on the continuous variable arm 53 side. For this reason, the transformation member 56 is brought into tight contact with the pad 57, and the roller 53d is brought into contact with the cam 23. At this time, since the cam shafts 21 rotate counterclockwise, an angle between a start point of a cam nose and a contact point between the roller 53d and the cam 23 is set to be widest, and the continuous variable arm 53 is driven by the cam 23 later than that in the neutral state. As a result, the valve opening timing or the valve closing timing are retarded.
On the other hand, when a valve opening or valve closing timing of an exhaust valve is to be advanced, the universal coupling 54a of the connection member 54 is caused to oscillate in such a direction that the universal coupling 54a goes away from the exhaust valves 14 and 15 side with reference to the neutral position.
The base end 53a is pulled to the right by the universal coupling 54a, and the continuous variable arm 53 moves to the right as a whole. On the other hand, the transformation member 56 is biased by the torsion coil spring 55 on the continuous variable arm 53 side. For this reason, the transformation member 56 is brought into tight contact with the pad 57, and the roller 53d is brought into contact with the cam 23.
At this time, since the cam shafts 21 rotate counterclockwise, an angle between a start point of a cam nose and a contact point between the roller 53d and the cam 23 is set to be narrowest, and the continuous variable arm 53 is driven by the cam 23 earlier than that in the neutral state. As a result, the valve opening timing or the valve closing timing are advanced.
The retarding and advancing adjustments are continuously performed by continuously adjusting an angle position of the rocker shaft 30.
As described above, the variable valve apparatus 20 can change a valve opening timing and a valve closing timing by making the drive mechanism 90 cause the rocker shaft 30 to oscillate. For this reason, the valve opening timing and the valve closing timing are changed to make it possible to increase an intake air flow and to achieve a reduction in fuel consumption.
With this configuration, in the internal combustion engine comprising the variable valve apparatus 20 having the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50, the following control can be performed.
First, the operations of the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 performed when an amount of internal EGR is optimized will be explained while comparing a “normal operation” and an “internal EGR operation”.
The cam shaft 21 causes an exhaust stroke which opens the exhaust valves 14 and 15 to slightly overlap an intake stroke performed by opening the air intake valves 12 and 13. An operation of the switching rocker arm mechanism 40 at this time is shown in
More specifically, when the operation mode of the switching rocker arm mechanism 40 is set to be off, oil pressure is not applied by the oil pressure supply mechanism 80, and engine oil is not supplied into the hollow portion 71a in the switching rocker arm mechanism 40. For this reason, the piston 73 is biased downward by an elastic force of the spring 74, and the notch 73a is located at the window portion 71b. On the other hand, the roller 41c moves along the cam 22 by the rotation of the cam 22 rotated by the cam shaft 21, and the switching rocker arm 41 oscillates about the rocker shaft 30 at predetermined intervals in a direction indicated by an arrow E in
In the continuous variable rocker arm mechanism 50, the rocker shaft 30 is set at a neutral position by means of the drive mechanism 90. Therefore, the roller 53d moves along the cam 23 by rotation of the cam 23 rotated by the cam shaft 21, and the continuous variable arm 53 oscillates about the rocker shaft 30 at predetermined intervals in a direction indicated by an arrow F in
As described above, in the normal operation, by the continuous variable rocker arm mechanism 50, the air intake valves 12 and 13 and the exhaust valves 14 and 15 are driven according to phases and lifts which change along a solid line S.
In an internal EGR operation, on the air intake valves 12 and 13 side, the operation mode of the switching rocker arm mechanism 40 is set to be off, and the operation mode of the continuous variable rocker arm mechanism 50 is set to an early closing (advance) mode. On the exhaust valves 14 and 15 side, the operation mode of the switching rocker arm mechanism 40 is set to be on, and the operation mode of the continuous variable rocker arm mechanism 50 is set to a normal (neutral) mode.
The operations of the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 are summarized as follows.
When the operation mode of the switching rocker arm mechanism 40 on the exhaust valves 14 and 15 side is set to be on, oil pressure is applied by the oil pressure supply mechanism 80. As shown in
In the continuous variable rocker arm mechanism 50 on the air intake valves 12 and 13 side, the rocker shaft 30 is rotated counterclockwise by a predetermined angle by means of the drive mechanism 90 and set at an advance angle position. A fulcrum of oscillation of the continuous variable arm 53 is distanced from the air intake valves 12 and 13. In this state, by rotation of the cam 23 rotated by the cam shaft 21, the roller 53d moves along the cam 23, and the continuous variable arm 53 oscillates about the rocker shaft 30 at predetermined intervals in a direction indicated by an arrow F in
As described above, in an intake stroke of the internal EGR operation, the air intake valves 12 and 13 are driven by the continuous variable rocker arm mechanism 50, and the exhaust valves 14 and 15 are driven by the switching rocker arm mechanism 40. Therefore, the air intake valves 12 and 13 open according to phases and lifts indicated by reference symbol S in
Since the lifts of the exhaust valves 14 and 15 at this time are constant, an amount of internal EGR is constant. On the other hand, since an operation state of the engine is not constant, a required amount of EGR changes. For this reason, this fine adjustment is performed by the operations of the air intake valves 12 and 13. More specifically, in order to prevent a reduction in NOx from being hindered due to an excessively small amount of internal EGR, the end of closing of the air intake valves 12 and 13 is made early to make it possible to reduce an amount of intake itself, and the amount of internal EGR consequently relatively increases.
As described above, the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 are operated in conjunction with each other to make it possible to obtain a more appropriate amount of EGR and to purify an exhaust gas.
Operations of the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 in an engine braking operation will be explained while comparing a “normal operation” and an “engine braking operation”.
The cam shaft 21 causes an exhaust stroke which opens the exhaust valves 14 and 15 to slightly overlap an intake stroke performed by opening the air intake valves 12 and 13. An operation of the switching rocker arm mechanism 40 at this time is shown in
The operation of the switching rocker arm mechanism 40 and the operation of the continuous variable rocker arm mechanism 50 in the normal state will not be explained because the operations are the same as those in
In an engine braking operation, on the air intake valves 12 and 13 side, the operation mode of the switching rocker arm mechanism 40 is set to be off, and the operation mode of the continuous variable rocker arm mechanism 50 is set to a normal (neutral) mode. On the exhaust valves 14 and 15 side, the operation mode of the switching rocker arm mechanism 40 is set to be on, and the operation mode of the continuous variable rocker arm mechanism 50 is set to an early opening (advance) mode.
The operations of the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 are summarized as follows.
When the operation mode of the switching rocker arm mechanism 40 on the exhaust valves 14 and 15 side is set to be on, oil pressure is applied by the oil pressure supply mechanism 80. As shown in
As shown in
As described above, in the engine braking operation, the air intake valves 12 and 13 are driven by the continuous variable rocker arm mechanism 50, and the exhaust valves 14 and 15 are driven by both the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50. Therefore, the air intake valves 12 and 13 open according to phases and lifts indicated by reference symbol N in
On the other hand, since the operation state of the engine is not constant, a necessary braking force changes. For this reason, this fine adjustment is performed by the operations of the exhaust valves 14 and 15 driven by the continuous variable rocker arm mechanism 50. More specifically, when the exhaust valves 14 and 15 start to open in a phase M1 or M2 slightly earlier than a standard phase M0 to make an opening timing early, an exhaust energy (amount of air) can be increased, and the braking force is consequently relatively increased.
As described above, when the switching rocker arm mechanism 40 and the continuous variable rocker arm mechanism 50 are operated in conjunction with each other, a more appropriate engine braking force can be obtained, and preferable drive feeling can be obtained.
As described above, according to the variable valve apparatus 20 for an internal combustion engine according to the embodiment, a plurality of functions such as execution of internal EGR, application of engine braking, improvement in fuel consumption, and purification of an exhaust gas can be simultaneously exerted.
According to the present invention, valves are opened or closed by using both the switching rocker arm mechanism and the continuous variable rocker arm mechanism to make it possible to realize a plurality of functions such as instantaneous switching of opening/closing timings of the valves and fine control of lifts.
Furthermore, transmission of oscillation displacement is selectively performed as needed to make it possible to open or close a valve without delay. The transmission of oscillation displacement is continuously performed to make it possible to finely control the drive phase and lift of the valve. When fine adjustment of an amount of EGR is performed while performing the internal EGR, an exhaust gas can be purified. Engine braking can be applied, and the effect can be enhanced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-338360 | Dec 2007 | JP | national |
| 2008-004745 | Jan 2008 | JP | national |
This is a Continuation application of PCT Application No. PCT/JP2008/073635, filed Dec. 25, 2008, which was published under PCT Article 21(2) in Japanese. This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2007-338360, filed Dec. 27, 2007; and No. 2008-004745, filed Jan. 11, 2008, the entire contents of both of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2008/073635 | Dec 2008 | US |
| Child | 12814139 | US |
