JP2000186517A - Valve driving mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the quantity of internal EGR gas supplied to the combustion chamber. SOLUTION: A second cam 3 and a valve 10 are switched so as to be driven- connected to each other or not. When the second cam 3 and an exhaust valve 10 are driven-connected, the exhaust valve 10 is opened during the intake stroke, and burnt gas is supplied from the engine-exhaust passage to the combustion chamber as the internal EGR gas. On the other hand, when the second can 3 and the exhaust valve 10 are not driven-connected, the exhaust valve 10 is closed during the intake stroke, and the internal EGR gas is not supplied from the engine-exhaust passage to the combustion chamber. The second cam 3 and the intake valve 10 are driven-connected, the intake valve 10 is opened during the exhaust stroke, and burnt gas is supplied from the engine-intake passage into the combustion chamber during the next intake stroke. When the second cam 3 and the intake valve 10 are not driven-connected, the intake valve 10 is closed, and the internal EGR gas is not supplied from the engine- exhaust passage to the combustion chamber during the next intake stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a valve drive mechanism.

[0002]

2. Description of the Related Art Conventionally, a first cam nose for opening an exhaust valve during a process in which burned gas is discharged out of a combustion chamber (hereinafter referred to as an "exhaust process"), and intake air is drawn into the combustion chamber. There is known a valve drive mechanism including a second cam nose for opening an exhaust valve during a power stroke (hereinafter, referred to as an “intake stroke”). According to this valve drive mechanism, by opening the exhaust valve during the intake stroke, the burned gas is supplied as internal EGR gas into the combustion chamber through the exhaust valve during the intake stroke. The exhausted NOx is reduced. An example of this type of valve driving mechanism is disclosed in, for example, Japanese Utility Model Laid-Open No. 1-166666.

FIG. 13 is a side view, partially in the axial direction, of a conventional exhaust valve driving cam, and FIG. 14 is a valve opening characteristic diagram of an exhaust valve driven by the cam shown in FIG. In FIG.
100 is an exhaust valve driving cam, 101 is a cam shaft, 1
02 is a first cam nose for opening the exhaust valve during the engine exhaust stroke, 103 is a second cam nose for opening the exhaust valve during the intake stroke, and 104 is a cam base circle. As shown in FIG. 13, the first cam nose 102
And the second cam nose 103 are formed in a single cam 100. Therefore, as shown in FIG. 14, the exhaust valve driven by the conventional exhaust valve driving cam 100 is opened not only in the exhaust stroke but also in the intake stroke.

[0004]

However, as described above, in the conventional valve drive mechanism, a single exhaust valve drive cam 1 is used.
Since the two cam nose 102 and 103 are formed at 00, the exhaust valve is always opened during the intake stroke. As a result, the internal EGR is always maintained during the intake stroke even under engine operating conditions in which burned gas (hereinafter referred to as “internal EGR gas”) does not need to be supplied from the engine exhaust passage to the combustion chamber via the exhaust valve during the intake stroke. Gas is supplied into the combustion chamber.

In view of the above problems, the present invention provides a valve drive mechanism capable of adjusting the amount of internal EGR gas supplied into a combustion chamber by switching whether or not to open an exhaust valve during an intake stroke. The purpose is to provide.

A further object of the present invention is to provide a valve drive mechanism capable of adjusting the amount of internal EGR gas supplied into the combustion chamber by switching whether or not to open an intake valve during an exhaust stroke. And

[0007]

According to the present invention, a first cam nose for opening a valve during a first stroke and a second cam nose different from the first stroke are provided. A second cam nose for opening a valve during a stroke, wherein the first cam nose is formed on a first cam, and the second cam nose is formed on a second cam. Switching means for switching whether to perform the drive connection between the second cam and the valve, and during the second stroke when the second cam and the valve are drive-connected. A valve drive mechanism is provided wherein the valve is open and the valve is closed during the second stroke when the second cam and the valve are not drivingly connected. .

According to a second aspect of the present invention, there is provided the valve drive mechanism according to the first aspect, wherein the valve is an exhaust valve.

According to the third aspect of the invention, the first stroke includes a stroke in which burned gas is discharged out of the combustion chamber, and the second stroke includes a stroke in which the intake air is exhausted from the combustion chamber. 3. The method according to claim 2, wherein the stroke is a part of a stroke sucked into the cylinder.
A valve drive mechanism according to (1) is provided.

In the valve driving mechanism according to any one of the first to third aspects, it is possible to switch whether or not to perform driving connection between the second cam and the valve. For example, when the exhaust valve is opened during a part of an intake stroke in which intake air is sucked into the combustion chamber and the second cam and the valve are not drivingly connected, for example, the intake air is sucked into the combustion chamber. The exhaust valve is closed during a part of the stroke. If the exhaust valve is opened during a part of the intake stroke, the burned gas enters the combustion chamber from the engine exhaust passage through the internal EGR.
If the exhaust valve is closed during a part of the intake stroke, the internal EGR gas is not supplied from the engine exhaust passage into the combustion chamber. As a result, for example, the amount of internal EGR gas supplied into the combustion chamber can be adjusted according to the engine operating conditions and the like.

According to a fourth aspect of the present invention, there is provided the valve drive mechanism according to the first aspect, wherein the valve is an intake valve.

According to the invention described in claim 5, the first stroke is a stroke including a stroke in which the intake air is sucked into the combustion chamber, and the second stroke is a stroke in which the burned gas is discharged outside the combustion chamber. 5. The process according to claim 4, wherein the discharge is part of a stroke discharged to the vehicle.
A valve drive mechanism according to (1) is provided.

In the valve drive mechanism according to the fourth and fifth aspects,
When the drive connection between the second cam and the valve is made possible by switching whether or not the drive connection between the second cam and the valve is performed, for example, an exhaust stroke in which burned gas is discharged outside the combustion chamber when the second cam and the valve are drive-connected. When the intake valve is opened and the second cam and the valve are not drivingly connected to each other, the intake valve is closed, for example, in a part of an exhaust stroke in which burned gas is discharged outside the combustion chamber. If the intake valve is opened during part of the exhaust stroke, burned gas is discharged from the combustion chamber into the engine intake passage,
Next, in the next intake stroke, the burned gas is supplied from the engine intake passage into the combustion chamber as internal EGR gas. On the other hand, if the intake valve is closed during a part of the exhaust stroke, the burned gas is not discharged from the combustion chamber into the engine intake passage. EGR gas is not supplied. as a result,
For example, the amount of internal EGR gas supplied into the combustion chamber can be adjusted according to engine operating conditions and the like.

According to the invention described in claim 6, the first cam is a high cam having a large maximum valve lift,
The valve drive mechanism according to claim 1, wherein the second cam is a low cam having a maximum valve lift smaller than a maximum valve lift of the first cam.

In the valve drive mechanism according to the present invention, the maximum valve lift of the second cam which affects the amount of internal EGR gas supplied into the combustion chamber is determined by the amount of burned gas discharged outside the combustion chamber or the maximum valve lift of the second cam. Since the maximum valve lift of the first cam which affects the amount of intake air drawn into the combustion chamber is made smaller, it is possible to prevent the amount of internal EGR gas supplied to the combustion chamber from becoming excessive. Can be.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view of a first embodiment of the valve drive mechanism of the present invention when the low cam and the exhaust valve are drivingly connected and the exhaust valve is opened by the cam nose of the high cam. FIG. 2 is a schematic configuration diagram of the present embodiment when the exhaust valve is opened by a cam nose of the low cam when the low cam and the exhaust valve are drivingly connected to each other, and FIG. FIG. 4 is a schematic configuration diagram of the present embodiment when the exhaust valve is opened by a cam nose of a high cam when the cam and the exhaust valve are not drivingly connected, and FIG. 4 shows that the second cam and the exhaust valve are driven. FIG. 3 is a schematic configuration diagram of the present embodiment when the exhaust valve is closed when not connected.

1 to 4, reference numeral 1 denotes a cam shaft for driving an exhaust valve, 2 denotes a high cam having a high nose height and a large maximum valve lift, and 3 denotes a low cam having a low nose height and a small maximum valve lift. It is. 4 is an inner lifter for contacting the low cam 3, 5 is an outer lifter for contacting the high cam 2, and 6 and 6 'are inner bodies forming part of the outer lifter 5. Reference numeral 7 denotes a connection plate for connecting the inner lifter 4 and the outer lifter 5, reference numeral 8 denotes a hydraulic pressure supply device for urging the connection plate 7 to the side connecting the inner lifter 4 and the outer lifter 5, and reference numeral 9 denotes an inner lifter 4.
And a spring for biasing the connecting plate 7 to the side where the outer lifter 5 and the outer lifter 5 are separated from each other. Reference numeral 10 denotes an exhaust valve, 11 denotes a valve seat with which the exhaust valve 10 contacts during a valve closing period, 12 denotes a retainer attached to the cam side end of the exhaust valve 10, and 13 denotes a valve for biasing the exhaust valve 10 to an open side. And a valve spring disposed between the retainer 12 and the cylinder head 15. Reference numeral 14 denotes a lifter spring that biases the inner lifter 4 toward the low cam 3 in order to position the inner lifter 4 at a position where it can be connected to the outer lifter 5.

As shown in FIGS. 1 to 4, the low cam 3 and the exhaust valve 10 are driven by the connecting plate 7 and the hydraulic supply device 8 via the inner lifter 4, the inner bodies 6 and 6 ′, and the retainer 12. Can be linked. In detail, as shown in FIGS. 1 and 2, when the connection plate 7 is urged toward the side connecting the inner lifter 4 and the outer lifter 5 by supplying hydraulic pressure from the hydraulic pressure supply device 8, the low cam 3 and the exhaust The valve 10 is drivingly connected. On the other hand, as shown in FIGS. 3 and 4, when the hydraulic pressure is not supplied by the hydraulic pressure supply device 8 and the connection plate 7 is urged to the side that separates the inner lifter 4 and the outer lifter 5, the low cam 3 and the exhaust valve 10 is not drivingly connected.

When the low cam 3 and the exhaust valve 10 are drivingly connected, the cam nose of the high cam 2 is
When the exhaust valve 10 is in contact with the exhaust valve 10 as shown in FIG.
Is opened by the cam nose of the high cam 2 via the outer lifter 5, the connecting plate 7, and the inner bodies 6, 6 '. When the low cam 3 and the exhaust valve 10 are drivingly connected, the cam nose of the low cam 3 is
When the exhaust valve 10 is in contact with the exhaust valve 10 as shown in FIG.
Is opened by the cam nose of the low cam 3 via the inner lifter 4, the connecting plate 7, and the inner bodies 6, 6 '. When the low cam 3 and the exhaust valve 10 are not drivingly connected and the cam nose of the high cam 2 is in contact with the outer lifter 5, as shown in FIG.
0 is opened by the cam nose of the high cam 2 via the outer lifter 5, the connecting plate 7, and the inner bodies 6, 6 '. Low cam 3 cam nose is inner lifter 4
When the low cam 3 and the exhaust valve 10 are not drivingly connected to each other, the exhaust valve 10 is not opened and remains closed as shown in FIG.

FIG. 5 is a graph showing the relationship between the crank angle and the valve lift by comparing the case where the low cam 3 and the exhaust valve 10 are drivingly connected and the case where the low cam 3 is not drivingly connected. FIG. 5A shows the low cam 3 and the exhaust valve 10.
FIG. 5B is a graph showing the relationship between the crank angle and the valve lift amount when the low cam 3 and the exhaust valve 10 are drivingly connected to each other. 4 is a graph showing a relationship with a valve lift amount. FIG. 6 is a partial sectional side view of the camshaft 1, the low cam 2, and the high cam 3. 5 and 6, 23 is a high cam cam nose, 24 is a high cam base circle, 33 is a low cam cam nose, 34 is a low cam base circle, L1 is the maximum valve lift of the high cam, and L2 is low. This is the maximum valve lift of the cam. The first stroke I is a stroke in which the exhaust valve 10 is opened by the high cam nose 23 or the low cam nose 33, and the second stroke II is the exhaust valve 10 is opened only by the low cam nose 33. A process that can be excused.

When the low cam 3 and the exhaust valve 10 are drivingly connected as shown in FIG. 5A, the exhaust valve 10 is opened by the high cam cam nose 23 in the first stroke I. Specifically, burned gas is discharged from the combustion chamber to the engine exhaust passage from the start of the first stroke I to the top dead center TDC, and the burned gas is discharged from the top dead center TDC to the end of the first stroke I. During that time, the burned gas is supplied from the engine exhaust passage to the combustion chamber as internal EGR gas. The state of the valve drive mechanism shown in FIG. 1 corresponds to the crank angle T1. Next, in the second stroke II, the exhaust valve 10 is set to the low cam cam nose 3.
3 opens the valve. Also in the second stroke II, the burned gas is supplied from the engine exhaust passage to the combustion chamber as internal EGR gas. The state of the valve drive mechanism shown in FIG. 2 corresponds to the crank angle T2. In addition, the second process II
The burned gas flows into the combustion chamber from the engine exhaust passage
Intake valve (not shown) when supplied as R gas
The valve is opened to allow intake air to be sucked into the combustion chamber. That is, in the second stroke II, the internal EGR gas is supplied into the combustion chamber via the exhaust valve 10 and the intake air is supplied via the intake valve (not shown).

On the other hand, when the low cam 3 and the exhaust valve 10 are not drivingly connected as shown in FIG.
As in the case shown in (a), in the first stroke I, the exhaust valve 10 is opened by the cam nose 23 having a high cam. More specifically, the top stroke T
Burned gas is discharged from the combustion chamber to the engine exhaust passage until DC, and burned gas is transferred from the engine exhaust passage to the combustion chamber from the top dead center TDC to the end of the first stroke I.
Supplied as gas. The state of the valve drive mechanism shown in FIG. 3 corresponds to the crank angle T3. Next, FIG.
In the second stroke II, the exhaust valve 10 is kept closed. Therefore, the burned gas is not supplied from the engine exhaust passage to the combustion chamber as internal EGR gas. The state of the valve drive mechanism shown in FIG.
It corresponds to. Note that, during the second stroke II, the intake valve (not shown) is opened to allow the intake air to be drawn into the combustion chamber. That is, in the second stroke II, the internal EGR gas is not supplied to the combustion chamber via the exhaust valve 10 but only the intake air is supplied via the intake valve (not shown).

According to this embodiment, the low cam 3 and the exhaust valve 1
When the low cam 3 and the exhaust valve 10 are drivingly connected by making it possible to switch whether or not to make the driving connection with 0, the intake air is drawn into the combustion chamber as shown in FIG. The exhaust valve 10 is opened in a second stroke II which is a part of the intake stroke. On the other hand, when the low cam 3 and the exhaust valve 10 are not drivingly connected, as shown in FIG. 5 (b), the exhaust valve 10 in the second stroke II, which is a part of the intake stroke in which the intake air is sucked into the combustion chamber. Is closed. When the exhaust valve 10 is opened during a part of the intake stroke, burned gas is supplied from the engine exhaust passage into the combustion chamber as internal EGR gas.
When 0 is closed, the internal EGR gas is not supplied from the engine exhaust passage into the combustion chamber.

As a result, by switching whether or not to drive the low cam 3 and the exhaust valve 10, it is possible to adjust the amount of internal EGR gas supplied into the combustion chamber according to, for example, engine operating conditions. It becomes possible. By appropriately supplying the internal EGR gas into the combustion chamber from the engine exhaust passage,
Emission can be improved and fuel efficiency can be improved. Further, when a supercharger is provided, the exhaust pressure is increased, so that it becomes easy to supply the internal EGR gas into the combustion chamber.

Further, according to this embodiment, the maximum valve lift L2 of the low cam 3, which affects the amount of internal EGR gas supplied from the engine exhaust passage to the combustion chamber, is discharged from the combustion chamber to the engine exhaust passage. Since it is made smaller than the maximum valve lift amount L1 of the high cam 2 which affects the burned gas amount,
It is possible to avoid an excessive amount of the internal EGR gas supplied into the combustion chamber.

In the present embodiment, the connection plate 7 is configured so that the inner lifter 4 and the outer lifter 5 are connected when the hydraulic pressure is supplied from the hydraulic pressure supply device 8. However, in other embodiments, the hydraulic supply is performed. It is also possible to configure the connection plate so that the inner lifter and the outer lifter are connected when the supply of the hydraulic pressure from the device is interrupted.

Hereinafter, a second embodiment of the valve drive mechanism of the present invention will be described. The present embodiment differs from the first embodiment only in that the phase of the cam nose of the low cam with respect to the high cam is different from that of the first embodiment.

FIG. 7 is a graph showing the relationship between the crank angle and the valve lift by comparing the case where the low cam 3 and the exhaust valve 10 are drivingly connected and the case where the low cam 3 is not drivingly connected. FIG. 7A shows the low cam 3 and the exhaust valve 10.
FIG. 7B is a graph showing the relationship between the crank angle and the valve lift amount when the low cam 3 and the exhaust valve 10 are drivingly connected. 4 is a graph showing a relationship with a valve lift amount. FIG. 8 is a partial cross-sectional side view of the camshaft 1, the low cam 2, and the high cam 3. As shown in FIGS. 7 and 8, in the valve drive mechanism of the present embodiment, the cam nose 23 of the high cam and the cam nose 33 of the low cam rotate the cam shaft more than in the first embodiment shown in FIG. It is arranged close to the direction. Therefore, the first stroke I and the second stroke II are closer to each other than in the case of the first embodiment shown in FIG.

As described above, by changing the timing of the second stroke II, that is, by changing the timing at which the internal EGR gas is supplied into the combustion chamber, it is possible to appropriately perform stratified combustion.

Hereinafter, a third embodiment of the valve drive mechanism of the present invention will be described. This embodiment differs from the first embodiment only in that the present invention is applied to an intake valve instead of an exhaust valve. That is, in FIGS. 1 to 4, reference numeral 1 denotes an intake valve driving cam shaft, 10 denotes an intake valve, 11 denotes a valve seat with which the intake valve 10 abuts during a closing period, and 12 denotes a cam-side end of the intake valve 10. The retainer 13 is a valve spring disposed between the retainer 12 and the cylinder head 15 to bias the intake valve 10 toward the valve opening side.

As shown in FIGS. 1 to 4, the low cam 3 and the intake valve 10 are driven by the connecting plate 7 and the hydraulic supply device 8 via the inner lifter 4, the inner bodies 6 and 6 ′, and the retainer 12. Can be linked. In detail, as shown in FIGS. 1 and 2, when the connection plate 7 is urged toward the side connecting the inner lifter 4 and the outer lifter 5 by supplying hydraulic pressure from the hydraulic supply device 8, the low cam 3 and the intake The valve 10 is drivingly connected. On the other hand, as shown in FIGS. 3 and 4, when the hydraulic pressure is not supplied by the hydraulic pressure supply device 8 and the connection plate 7 is biased to the side that separates the inner lifter 4 and the outer lifter 5, the low cam 3 and the intake valve 10 is not drivingly connected.

When the low cam 3 and the intake valve 10 are drivingly connected, the cam nose of the high cam 2 is
1, as shown in FIG.
Is opened by the cam nose of the high cam 2 via the outer lifter 5, the connecting plate 7, and the inner bodies 6, 6 '. When the low cam 3 and the intake valve 10 are drivingly connected, the cam nose of the low cam 3 is
2, the intake valve 10 as shown in FIG.
Is opened by the cam nose of the low cam 3 via the inner lifter 4, the connecting plate 7, and the inner bodies 6, 6 '. When the low cam 3 and the intake valve 10 are not drivingly connected and the cam nose of the high cam 2 is in contact with the outer lifter 5, as shown in FIG.
0 is opened by the cam nose of the high cam 2 via the outer lifter 5, the connecting plate 7, and the inner bodies 6, 6 '. Low cam 3 cam nose is inner lifter 4
Even when the low cam 3 and the intake valve 10 are not drivingly connected to each other, the intake valve 10 is not opened and remains closed as shown in FIG.

FIG. 9 is a graph showing the relationship between the crank angle and the valve lift by comparing the case where the low cam 3 and the intake valve 10 are drivingly connected and the case where the low cam 3 is not drivingly connected. FIG. 9A shows the low cam 3 and the intake valve 10.
FIG. 9B is a graph showing the relationship between the crank angle and the valve lift amount when the low cam 3 and the intake valve 10 are drivingly connected to each other. 4 is a graph showing a relationship with a valve lift amount. FIG. 10 is a partial cross-sectional side view of the camshaft 1, the low cam 2, and the high cam 3. 9 and FIG.
Is the high cam cam nose, 24 is the high cam base circle, 33
Is the low cam cam nose, 34 is the low cam base circle, L1
Is the maximum valve lift of the high cam, and L2 is the maximum valve lift of the low cam. The first stroke I is defined by the cam nose 23 having a high cam or the cam nose 33 having a low cam.
The second stroke II is a stroke in which the intake valve 10 can be opened only by the cam nose 33 having a low cam.

When the low cam 3 and the intake valve 10 are drivingly connected as shown in FIG. 9A, the intake valve 10 is opened by the low cam cam nose 33 in the second stroke II. Specifically, the burned gas is discharged from the combustion chamber to the engine intake passage. The state of the valve drive mechanism shown in FIG. 2 corresponds to the crank angle T5. In addition, the second process II
When the burned gas is being discharged from the combustion chamber to the engine intake passage in (2), an exhaust valve (not shown) is opened to discharge the burned gas to the engine exhaust passage. Next, in the first stroke I, the intake valve 10 is moved to the high cam cam nose 23.
The valve is opened. Specifically, the burned gas is discharged from the combustion chamber to the engine intake passage from the start of the first stroke I to the top dead center TDC, and the burned gas is discharged from the top dead center TDC to the end of the first stroke I. During that time, burned gas as internal EGR gas and intake air are supplied from the engine intake passage into the combustion chamber. The state of the valve drive mechanism shown in FIG.
6 is supported.

On the other hand, when the low cam 3 and the exhaust valve 10 are not drivingly connected as shown in FIG.
Unlike the case shown in (a), in the second stroke II, the intake valve 10 remains closed. Therefore, the burned gas is not discharged from the combustion chamber to the engine intake passage. The state of the valve drive mechanism shown in FIG. 4 corresponds to the crank angle T7. Note that, during the second stroke II, the exhaust valve (not shown) is opened to discharge burned gas to the engine exhaust passage. That is, in the second stroke II, the burned gas is not discharged to the engine intake passage via the intake valve 10 but is discharged only to the engine exhaust passage via the exhaust valve (not shown).
Next, as in the case shown in FIG.
The intake valve 10 is opened by the cam nose 23 having a high cam. Specifically, the burned gas is discharged from the combustion chamber to the engine intake passage from the start of the first stroke I to the top dead center TDC, and the burned gas is discharged from the top dead center TDC to the end of the first stroke I. During that time, burned gas as internal EGR gas and intake air are supplied from the engine intake passage into the combustion chamber. The state of the valve drive mechanism shown in FIG. 3 corresponds to the crank angle T8.

According to the present embodiment, the low cam 3 and the intake valve 1
When the low cam 3 and the intake valve 10 are drivingly connected, the burned gas is discharged from the combustion chamber as shown in FIG. In the second stroke II which is a part of the exhaust stroke to be performed, the intake valve 10 is opened. On the other hand, when the low cam 3 and the intake valve 10 are not drivingly connected to each other, as shown in FIG. 9B, the intake valve is in a second stroke II which is a part of an exhaust stroke in which burned gas is discharged from the combustion chamber. 10 is closed. When the intake valve 10 is opened in the second stroke II which is a part of the exhaust stroke, burned gas is discharged from the combustion chamber to the engine intake passage, while the second combustion which is a part of the exhaust stroke is performed. Itinerary I
If the intake valve 10 is closed in I, the burned gas is not discharged from the combustion chamber to the engine intake passage.

As a result, by switching whether or not the driving connection between the low cam 3 and the intake valve 10 is performed, the burned combustible discharged from the combustion chamber to the engine intake passage in the exhaust stroke according to the engine operating conditions, for example. It is possible to adjust the gas amount, that is, to adjust the amount of burned gas as internal EGR gas supplied from the engine intake passage into the combustion chamber in the next intake stroke. Internal EG from the engine intake passage into the combustion chamber
By appropriately supplying the R gas, it is possible to improve emission and fuel efficiency.

Further, according to the present embodiment, the maximum of the low cam 3 which affects the amount of burned gas supplied as internal EGR gas from the engine intake passage into the combustion chamber after being discharged from the combustion chamber to the engine intake passage. Since the valve lift amount L2 is smaller than the maximum valve lift amount L1 of the high cam 2 which affects the intake air amount supplied from the engine exhaust passage to the combustion chamber, the internal EGR gas amount supplied into the combustion chamber is reduced. It is possible to avoid being excessive.

In the present embodiment, the connecting plate 7 is configured so that the inner lifter 4 and the outer lifter 5 are connected when the hydraulic pressure is supplied from the hydraulic pressure supply device 8. It is also possible to configure the connection plate so that the inner lifter and the outer lifter are connected when the supply of the hydraulic pressure from the device is interrupted.

Hereinafter, a fourth embodiment of the valve drive mechanism of the present invention will be described. This embodiment differs from the third embodiment only in that the phase of the cam nose of the low cam with respect to the high cam is different from that of the third embodiment.

FIG. 11 is a graph showing the relationship between the crank angle and the valve lift by comparing the case where the low cam 3 and the intake valve 10 are drivingly connected and the case where the low cam 3 is not drivingly connected. FIG. 11A is a graph showing the relationship between the crank angle and the valve lift when the low cam 3 and the intake valve 10 are drivingly connected.
(B) is a graph showing the relationship between the crank angle and the valve lift when the low cam 3 and the intake valve 10 are drivingly connected. FIG. 12 is a partial sectional side view of the camshaft 1, the low cam 2, and the high cam 3. As shown in FIGS. 11 and 12, in the valve drive mechanism of this embodiment, the cam nose 23 of the high cam and the cam nose 33 of the low cam rotate the cam shaft more than in the first embodiment shown in FIG. It is arranged close to the direction. Therefore, the first process I
And the second step II are closer than in the first embodiment shown in FIG.

[0043]

According to the first to fifth aspects of the present invention, the amount of internal EGR gas supplied into the combustion chamber can be adjusted.

According to the sixth aspect of the invention, it is possible to prevent the internal EGR gas amount supplied into the combustion chamber from becoming excessive.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of a valve drive mechanism of the present invention when an exhaust valve is opened by a cam nose of a high cam when a low cam and an exhaust valve are drivingly connected. It is.

FIG. 2 is a schematic configuration diagram of the first embodiment when the exhaust valve is opened by a cam nose of the low cam when the low cam and the exhaust valve are drivingly connected.

FIG. 3 is a schematic configuration diagram of the first embodiment when the exhaust valve is opened by a high cam nose when the second cam and the exhaust valve are not drivingly connected;

FIG. 4 is a schematic configuration diagram of the first embodiment when the exhaust valve is closed when the second cam and the exhaust valve are not drivingly connected.

FIG. 5 is a graph showing a relationship between a crank angle and a valve lift amount in a case where the low cam and the exhaust valve of the first embodiment are drivingly connected and not drivingly connected. .

FIG. 6 is a partial cross-sectional side view of the camshaft, the low cam, and the high cam of the first embodiment.

FIG. 7 is a graph showing a relationship between a crank angle and a valve lift amount in a case where the low cam and the exhaust valve of the second embodiment are drivingly connected and not drivingly connected. .

FIG. 8 is a partial cross-sectional side view of a camshaft, a low cam, and a high cam according to a second embodiment.

FIG. 9 is a graph showing a relationship between a crank angle and a valve lift amount when a low cam and an exhaust valve of the third embodiment are drivingly connected and not drivingly connected. .

FIG. 10 is a partial cross-sectional side view of a camshaft, a low cam, and a high cam according to a third embodiment.

FIG. 11 is a graph showing a relationship between a crank angle and a valve lift amount in a case where the low cam and the exhaust valve of the fourth embodiment are drivingly connected and not drivingly connected. .

FIG. 12 is a partial cross-sectional side view of a camshaft, a low cam, and a high cam according to a fourth embodiment.

FIG. 13 is a side view, partially in the axial direction, of a conventional exhaust valve driving cam.

FIG. 14 is a valve opening characteristic diagram of an exhaust valve driven by a conventional cam.

[Explanation of symbols]

 2 First cam 3 Second cam 7 Connection plate 8 Hydraulic supply device 9 Spring for separation 10 Valve

Claims (6)

[Claims] 1. A first cam nose for opening a valve during a first stroke and a second cam nose for opening a valve during a second stroke different from the first stroke. Wherein the first cam nose is formed on a first cam, the second cam nose is formed on a second cam, and performs a drive connection between the second cam and the valve. The second cam and the valve are drivingly connected, the valve is opened during the second stroke, and the second cam and the second cam are connected to each other. A valve drive mechanism, wherein the valve is closed during the second stroke when the valve is not drivingly connected to the valve. 2. The valve driving mechanism according to claim 1, wherein the valve is an exhaust valve. 3. The first stroke includes a stroke in which burned gas is discharged out of the combustion chamber, and the second stroke is a part of a stroke in which intake air is sucked into the combustion chamber. The valve drive mechanism according to claim 2, wherein the valve drive mechanism is provided. 4. The valve driving mechanism according to claim 1, wherein the valve is an intake valve. 5. The first stroke includes a stroke in which intake air is sucked into a combustion chamber, and the second stroke is a part of a stroke in which burned gas is discharged outside the combustion chamber. The valve drive mechanism according to claim 4, wherein the valve drive mechanism is provided. 6. The first cam is a high cam having a large maximum valve lift, and the second cam is a low cam having a maximum valve lift smaller than the maximum valve lift of the first cam. The valve drive mechanism according to claim 1, wherein