JP7354645B2 - Cam switching mechanism and internal combustion engine - Google Patents

Description

The present invention relates to a cam switching mechanism and an internal combustion engine, and more particularly to a cam switching mechanism and an internal combustion engine that open and close at least one of an intake valve and an exhaust valve.

BACKGROUND ART Conventionally, internal combustion engines are known that include a cam switching mechanism that opens and closes an intake valve (for example, see Patent Document 1).

The above Patent Document 1 discloses an internal combustion engine that includes a cam switching mechanism that switches cams that open and close intake valves. The cam switching mechanism is configured to control the phase width in which the intake valve is opened by switching the cam. Note that in an internal combustion engine, the phase width in which the intake valve and the exhaust valve are opened is approximately 90 degrees to 180 degrees.

Japanese Patent Application Publication No. 2013-144945

In the internal combustion engine described in Patent Document 1, the phase width in which the intake valve and the exhaust valve are opened is about 90 degrees to 180 degrees, which is relatively small. It tends to create large negative pressure. For this reason, the intake passage after the throttle valve (on the downstream side) also tends to have a large negative pressure, and there is a problem in that the resistance (pumping loss) caused by the throttle valve becomes large when intake air is sucked into the downstream side of the intake passage.

This invention has been made to solve the above problems, and one object of the invention is to provide a cam switching mechanism and an internal combustion engine that can reduce pumping loss.

In order to achieve the above object, a cam switching mechanism according to a first aspect of the present invention includes a first cam and a second cam that open and close an intake valve , and the first cam controls the intake valve so that the piston is at the bottom dead center. The opening/closing timing is set to advance the phase between the bottom dead center and the top dead center during the movement from the top dead center to the top dead center, and the second cam retards the intake valve from the intermediate phase. The opening/closing timing is set to close at the side, and the first cam and the second cam are configured to be switchable. The valve position and the valve position are located close to each other .

In the cam switching mechanism according to the first aspect of the present invention, by being configured as described above, when the first cam and the second cam are provided, the mechanism is switched to the second cam that closes the intake valve at an extremely slow phase. , the intake valve can be closed on the retard side with respect to the intermediate phase between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. That is, the intake valve can be closed very late. Therefore, most of the intake air that has flowed into the cylinder can be blown back toward the intake passage when the piston is raised, so that negative pressure in the cylinder can be suppressed. That is, it is also possible to suppress negative pressure in the intake passage after the throttle valve (on the downstream side). As a result, pumping loss (resistance due to the throttle valve) can be reduced when intake air is sucked into the downstream side of the intake passage. Furthermore, it has been desired to effectively exhibit catalytic performance. Catalyst performance deteriorates as the amount of oxygen passing through the catalyst increases, as thermal deterioration of the catalyst becomes more likely to occur. As mentioned above, if the intake air can be blown back into the intake passage when the piston rises, the amount of oxygen flowing to the catalyst side can be reduced, thereby suppressing thermal deterioration (deterioration in performance) of the catalyst. . Additionally, if the intake air can be blown back into the intake passage, the temperature of the intake air and fuel can be effectively raised (atomized) within the intake passage, reducing the amount of fuel injected (reducing rich spikes). can do.

In the cam switching mechanism according to the first aspect, preferably, the second cam is configured to set the opening/closing timing of the intake valve to open near the top dead center.

With this configuration, the intake valve can remain open during almost all phases from when the piston starts descending until it completes its ascent, which further suppresses negative pressure inside the cylinder. can do. Therefore, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.

In the cam switching mechanism according to the first aspect, preferably, fuel is supplied to the combustion chamber at least during a period when the output torque generation request is released and fuel injection from the injector is stopped (during fuel cut). The second cam is configured to open and close the intake valve during the period until the engine is first ignited (when the engine is started).

With this configuration, it is possible to reduce pumping loss (resistance due to the throttle valve) during fuel cut or engine start, and it is also possible to effectively exhibit catalyst performance.

In this case, preferably, if the intake valve is opened and closed by the second cam during a period when the output torque generation request is canceled and fuel injection from the injector is stopped, it is preferable that the intake valve be opened and closed immediately after the output torque generation request is canceled. The first cam is configured to switch from the first cam to the second cam at the timing when the ignition in the combustion chamber is turned off.

With this configuration, it is possible to switch from the first cam to the second cam at an appropriate timing that matches the timing at which the fuel cut is started. Therefore, even immediately after the fuel cut is started, pumping loss (resistance due to the throttle valve) can be appropriately reduced, and the catalyst performance can be effectively exhibited.

In the cam switching mechanism according to the first aspect, preferably, the first cam and the second cam are configured to set the opening/closing timing of the intake valve so that the intake valve and the exhaust valve do not open at the same time. ing.

With this configuration, valve overlap can be reliably prevented, and therefore intake air can be reliably prevented from flowing to the exhaust side.

An internal combustion engine according to a second aspect of the invention includes an internal combustion engine main body provided with an intake valve and an exhaust valve, and an intake side cam switching mechanism that opens and closes the intake valve. A first cam that sets the opening/closing timing to close the valve on the advance side of the intermediate phase between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center; The second cam is configured to be able to switch between the first cam and the second cam, and the second cam sets the opening/closing timing to be closed on the retarded side than the phase of the valve opening/closing timing. The position when the intake valve is open and the position when the intake valve is closed are located close to each other .

In the internal combustion engine according to the second aspect of the present invention, by configuring as described above, pumping loss can be reduced similarly to the cam switching mechanism according to the first aspect.
A cam switching mechanism according to a third aspect of the invention includes a first cam and a second cam that open and close an intake valve, and the first cam controls the intake valve while the piston moves from bottom dead center to top dead center. Setting the opening/closing timing to close the intake valve at an advanced angle side than the intermediate phase between the bottom dead center and the top dead center, and setting the opening/closing timing to close the intake valve at the retarded side than the intermediate phase using the second cam, The first cam and the second cam are configured to be switchable, and the second cam is configured to set the opening/closing timing to close the intake valve near the top dead center.
By configuring the cam switching mechanism according to the third aspect of the invention as described above, pumping loss can be reduced similarly to the cam switching mechanism according to the first aspect. Furthermore, the intake air that has flowed into the cylinder can be blown back to the intake passage side more effectively. Therefore, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.
A cam switching mechanism according to a fourth aspect of the invention includes a first cam and a second cam that open and close an intake valve, and the first cam controls the intake valve while the piston moves from the bottom dead center to the top dead center. Setting the opening/closing timing to close the intake valve at an advanced angle side than the intermediate phase between the bottom dead center and the top dead center, and setting the opening/closing timing to close the intake valve at the retarded side than the intermediate phase using the second cam, The first cam and the second cam are configured to be switchable, and the first cam is configured to set the opening/closing timing to close the intake valve on the retarded side of bottom dead center, and The apparatus further includes a small cam that opens near the bottom dead center and closes at an advance side of the bottom dead center, and is configured to be able to switch between the small cam, the first cam, and the second cam.
With the cam switching mechanism according to the fourth aspect of the present invention, by configuring as described above, pumping loss can be reduced similarly to the cam switching mechanism according to the first aspect. In addition, the small cam allows more appropriate (fine) switching of the cam depending on the driving situation of the vehicle, which further reduces pumping loss (resistance caused by the throttle valve). Catalytic performance can be demonstrated more effectively.
An internal combustion engine according to a fifth aspect of the invention includes an internal combustion engine main body provided with an intake valve and an exhaust valve, and an intake side cam switching mechanism for opening and closing the intake valve. , the intake side cam switching mechanism is configured to set the opening/closing timing to close the intake valve at an advanced angle than the intermediate phase between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. 1 cam and a second cam that sets the opening/closing timing to close the intake valve on the retarded side than the intermediate phase, and is configured to be able to switch between the first cam and the second cam, and the second cam The valve is configured to open and close at a timing close to the top dead center.
In the internal combustion engine according to the fifth aspect of the present invention, by configuring as described above, pumping loss can be reduced similarly to the cam switching mechanism according to the first aspect. Furthermore, the intake air that has flowed into the cylinder can be blown back to the intake passage side more effectively. Therefore, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.
An internal combustion engine according to a sixth aspect of the invention includes an internal combustion engine main body provided with an intake valve and an exhaust valve, and an intake side cam switching mechanism for opening and closing the intake valve. , the intake side cam switching mechanism sets the opening/closing timing to close the intake valve on the advance side of the intermediate phase between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. 1 cam and a second cam that sets the opening/closing timing to close the intake valve on the retarded side than the intermediate phase, and is configured to be switchable between the first cam and the second cam, and the first cam is configured to be able to switch between the first cam and the second cam. The valve is configured to open and close at a timing that is retarded from bottom dead center, and the intake valve is opened near top dead center and closed at an advanced angle from bottom dead center. The apparatus further includes a small cam, and is configured to be able to switch between the small cam, the first cam, and the second cam.
In the internal combustion engine according to the sixth aspect of the present invention, by configuring as described above, pumping loss can be reduced similarly to the cam switching mechanism according to the first aspect. In addition, the small cam allows for more appropriate (fine) cam switching depending on the vehicle's driving conditions, which further reduces pumping loss (resistance caused by the throttle valve). Catalytic performance can be demonstrated more effectively.

In addition, in the present application, the following configurations are also considered for the cam switching mechanism and internal combustion engine.

(Additional note 1)
That is, in the above cam switching mechanism and internal combustion engine, the second cam is configured such that the intake valve opens at the movement timing of the piston corresponding to the intake stroke and the compression stroke after fuel is supplied to the combustion chamber of the internal combustion engine body and ignited. It is configured to set the opening/closing timing of the intake valve so that the intake valve is maintained in this state.

With this configuration, the intake valve can be kept open over a longer phase width during the movement timing of the piston corresponding to the intake stroke and the compression stroke, and pumping loss (resistance due to the throttle valve) can be reduced. Catalytic performance can be effectively exhibited.

(Additional note 2)
Further, in the cam switching mechanism and internal combustion engine, the second cam is configured such that the angular width of the intake valve opening period is 360 degrees at the opening/closing timing of the intake valve.

With this configuration, when the intake valve moves, it is possible to reliably prevent negative pressure from being generated in the cylinder (the intake passage after the throttle valve (on the downstream side)).

1 is a diagram showing the configuration of an engine according to a first embodiment. FIG. 1 is a front view and a side view schematically showing a cam switching mechanism of an engine according to a first embodiment. FIG. 3 is a diagram showing valve timings of an intake valve and an exhaust valve when the first cam of the engine according to the first embodiment is used. FIG. 6 is a diagram showing valve timings of an intake valve and an exhaust valve when the second cam of the engine according to the first embodiment is used. FIG. 3 is a diagram showing the relationship between the valve phase and valve lift amount of the intake valve of the engine according to the first embodiment. FIG. 3 is a diagram for explaining the relationship between on/off of the accelerator, ignition timing, cam switching, throttle opening, fuel injection, and O ₂ emissions discharged from the engine. FIG. 7 is a front view and a side view schematically showing a cam switching mechanism of an engine according to a second embodiment. FIG. 7 is a diagram showing a relationship between a valve phase and a valve lift amount of an intake valve of an engine according to a second embodiment. FIG. 3 is a diagram showing the configuration of an engine according to a modification of the first embodiment. FIG. 7 is a diagram showing valve timings of intake valves and exhaust valves when the second cam and fourth cam of the engine are used according to a modification of the first embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described based on the drawings.

[First embodiment]
The configuration of an engine 1 (an example of an internal combustion engine) according to the first embodiment will be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, the engine 1 of the first embodiment includes an engine main body 2 (an example of the "internal combustion engine main body" in the claims), an ECU (Engine Control Unit) 3, and an intake side cam switching mechanism 4 ( An example of the "cam switching mechanism" in the claims).

The engine body 2 includes a cylinder block 21 and a cylinder head 22 attached to the upper part of the cylinder block 21. The cylinder block 21 has a cylinder 24 in which a combustion chamber 23 is provided. A crankshaft (not shown) is provided within the engine body 2. Further, the engine body 2 is provided with an intake valve 25a and an exhaust valve 25b.

An intake pipe 4a is connected to the engine body 2 from the upstream side, and an exhaust pipe 4b is connected from the downstream side. The intake pipe 4a is configured to supply intake air to the combustion chamber 23 via an intake valve 25a. The exhaust pipe 4b is configured to discharge exhaust gas (exhaust gas) discharged from the combustion chamber 23 to the outside (atmosphere) via the exhaust valve 25b. A catalyst C is provided in the exhaust pipe 4b.

The engine 1 rotates the intake camshaft 26a and the exhaust camshaft 26b using the power of the crankshaft via a timing chain (not shown), thereby adjusting the intake valve 25a and the exhaust valve 25b to predetermined valve positions, respectively. It is configured to open and close depending on the timing.

In each figure (FIG. 1, FIG. 2, FIG. 7, and FIG. 9), the axial direction (extending direction) of the intake side camshaft 26a and the exhaust side camshaft 26b is shown as the S direction.

The ECU 3 is configured to transmit a predetermined drive signal to the intake-side cam switching mechanism 4 to control switching between the first cam 42a and the second cam 42b.

(Configuration of intake side cam switching mechanism)
As shown in FIG. 2, the intake cam switching mechanism 4 includes a power transmission section 41, a first cam 42a, and a second cam 42b. Note that the second cam 42b is formed larger than the first cam 42a when viewed from the side (viewed from the axial direction of the intake-side camshaft 26a).

<Configuration of power transmission section>
The power transmission section 41 is configured to be able to switch between a first cam 42a and a second cam 42b. The power transmission section 41 is configured to switch between the first cam 42a and the second cam 42b and transmit the power of one of the first cam 42a and the second cam 42b to the intake valve 25a.

The power transmission unit 41 connects a first rocker arm 41a driven by a first cam 42a, a second rocker arm 41b driven by a second cam 42b, and the first rocker arm 41a and the second rocker arm 41b. and a connecting portion (not shown) that synchronizes the driving of both. Note that the first rocker arm 41a and the second rocker arm 41b are rotatably supported by a common shaft 43.

The first rocker arm 41a directly supports the intake valve 25a at one end. Therefore, the intake valve 25a is normally configured to be driven by the first cam 42a via the first rocker arm 41a. Further, when the intake side cam switching mechanism 4 receives a predetermined drive signal from the ECU 3 (see FIG. 1), the first rocker arm 41a and the second rocker arm 41b are connected by the connecting portion, and the second cam 42b is connected to the first rocker arm 41a and the second rocker arm 41b. It is configured to switch to a state in which the intake valve 25a is driven.

<Configuration of the first cam>
The first cam 42a is configured to drive the intake valve 25a via the power transmission section 41 when the engine 1 is driven and the vehicle is in a normal driving state. As shown in FIG. 3, the first cam 42a opens the intake valve 25a near the top dead center, and also opens the intake valve 25a near the top dead center and between the bottom dead center and the top dead center while the piston P moves from the bottom dead center to the top dead center. The opening/closing timing is configured to be set to close on the advance side of the intermediate phase α.

As a specific example, the cam profile of the first cam 42a has an IVO set to approximately 0 degrees TDC. Further, the cam profile of the first cam 42a has an IVC set to about 45 degrees ABDC.

Note that the above IVO is a description that omits Intake Valve Open. Moreover, the above TDC is a description that omits Top Dead Center. Furthermore, the above IVC is a description that omits Intake Valve Close. Moreover, the above-mentioned ABDC is a description that omits After Bottom Dead Center.

As shown in FIG. 5, the first cam 42a causes the valve lift amount of the intake valve 25a to instantaneously reach the maximum value R2 at an intermediate phase between IVO (approximately ABDC 45 degrees) and IVC (approximately TDC 0 degrees). is configured to do so. That is, the first cam 42a is not configured to maintain (keep) the intake valve 25a in a state where the valve lift amount is the maximum value R2.

Therefore, the first cam 42a generally has a shape that is a combination of a circular portion and a triangular portion provided on the outer circumferential side of the circular portion when viewed from the side (viewed from the axial direction of the intake side camshaft 26a). (See Figure 2).

<Configuration of second cam>
The engine 1 shown in FIG. 1 opens and closes the intake valve 25a using the second cam 42b during a period when the output torque generation request is released and fuel injection from the injector is stopped (including when the vehicle is stopped). It is configured. Note that the release of the output torque generation request essentially means that the accelerator is turned off.

Here, as shown in FIG. 6, in the engine 1, the timing at which the ignition in the combustion chamber 23 is turned off (immediately after the accelerator is turned off) after the output torque generation request is released (immediately after the accelerator is turned off) (the timing at which the fuel is cut) is determined. ), the intake cam switching mechanism 4 is configured to switch from the first cam 42a to the second cam 42b. Thereby, the amount of oxygen exhausted from the engine 1 is reduced to approximately zero. Note that when the first cam 42a is switched to the second cam 42b, a small amount of oxygen is discharged to the exhaust side, but thereafter oxygen is not discharged to the exhaust side.

Further, the engine 1 is configured to turn off fuel injection from the injector immediately after the output torque generation request is released (immediately after the accelerator is turned off). Further, the engine 1 is configured to reduce the opening degree of the throttle immediately after the output torque generation request is released (immediately after the accelerator is turned off).

Further, the engine 1 is configured to open and close the intake valve 25a using the second cam 42b during a period from when fuel is supplied to the combustion chamber 23 to when it is first ignited. In short, the engine 1 is configured so that the second cam 42b opens and closes the intake valve 25a when the vehicle is started.

As shown in FIG. 4, the second cam 42b moves the intake valve 25a at a retard angle relative to the intermediate phase α between the bottom dead center and the top dead center while the piston P moves from the bottom dead center to the top dead center. The opening/closing timing is set to close on the side. Specifically, the second cam 42b is configured to set the opening/closing timing to close the intake valve 25a near the top dead center (including the top dead center). Further, the second cam 42b is configured to set the opening/closing timing of the intake valve 25a to open near the top dead center. That is, the second cam 42b is configured to set the opening/closing timing to keep the intake valve 25a open until the piston P moves from the top dead center to the top dead center again.

As a specific example, in the cam profile of the second cam 42b, both IVO and IVC are set to about TDC 0 degrees. Therefore, the second cam 42b is configured such that the angular width of the opening period of the intake valve 25a is 360 degrees at the opening/closing timing of the intake valve 25a.

In short, the second cam 42b maintains the intake valve 25a in the open state at the movement timing of the piston P corresponding to the intake stroke and compression stroke after fuel is supplied to the combustion chamber 23 of the engine body 2 and ignited. Thus, the opening/closing timing of the intake valve 25a is set.

As shown in FIG. 5, the second cam 42b maintains (keeps) the valve lift amount at the maximum value R2 for a predetermined phase interval from the phase in which the valve lift amount of the first cam 42a takes the maximum value R2. It is composed of

Therefore, the second cam 42b generally has a shape that is a combination of a circular portion and a trapezoidal portion provided on the outer peripheral side of the circular portion when viewed from the side (viewed from the axial direction of the intake side camshaft 26a). (See Figure 2).

As shown in FIGS. 3 and 4, the cam 5 (see FIG. 1) that drives the exhaust valve 25b moves the exhaust valve 25b between top dead center and bottom dead center while the piston P moves from top dead center to bottom dead center. The opening/closing timing is set to open at a later angle than the phase β intermediate between the dead center and the opening/closing timing to close near the top dead center.

As a specific example, the cam profile of the cam 5 has an EVO set to about 45 degrees BBDC. Further, the cam profile of the cam 5 has an EVC set to approximately 0 degrees TDC.

Note that the above EVO is a description that omits Exhaust Valve Open. Moreover, the above-mentioned BBDC is a description in which "Before Bottom Dead Center" is omitted. Moreover, the above EVC is a description that omits "Exhaust Valve Close".

Therefore, the first cam 42a and the second cam 42b shown in FIG. 1 are configured to set the opening/closing timing of the intake valve 25a so that the intake valve 25a and the exhaust valve 25b do not open at the same time. ing. That is, the engine 1 is configured so that there is (substantially) no valve overlap between the intake valve 25a and the exhaust valve 25b. Note that in the valve timing, the angular width (phase width) from when the exhaust valve 25b is closed until the intake valve 25a is opened is (approximately) 0 degrees. That is, the engine 1 is configured such that the intake valve 25a is opened immediately after the exhaust valve 25b is closed.

(Effects of the first embodiment)
In the first embodiment, the following effects can be obtained.

In the first embodiment, with the above configuration, the first cam 42a and the second cam 42b (intake side cam switching mechanism 4) are provided, and the second cam 42b closes the intake valve 25a at an extremely slow phase. By switching, the intake valve 25a can be closed on the retard side with respect to the intermediate phase between the bottom dead center and the top dead center while the piston P moves from the bottom dead center to the top dead center. That is, the intake valve 25a can be closed extremely late. Therefore, most of the intake air that has flowed into the cylinder 24 can be blown back toward the intake passage when the piston P rises, so that negative pressure in the cylinder 24 can be suppressed. That is, it is also possible to suppress negative pressure in the intake passage after the throttle valve (on the downstream side). As a result, pumping loss (resistance due to the throttle valve) can be reduced when intake air is sucked into the downstream side of the intake passage. Furthermore, it has been desired to effectively exhibit catalytic performance. The catalyst performance decreases as the amount of oxygen passing through the catalyst C increases, because the catalyst C is more likely to undergo thermal deterioration. As mentioned above, if the intake air can be blown back to the intake passage side when the piston P rises, the amount of oxygen flowing to the catalyst C side can be reduced, thereby suppressing thermal deterioration (performance deterioration) of the catalyst C. be able to. Additionally, if the intake air can be blown back into the intake passage, the temperature of the intake air and fuel can be effectively raised (atomized) within the intake passage, reducing the amount of fuel injected (reducing rich spikes). can do. Note that if the inside of the cylinder 24 can be suppressed from becoming a negative pressure, engine oil will flow from the crankcase side into the combustion chamber 23 via between the piston P and the inner surface of the cylinder 24. It is possible to suppress the infiltration of As a result, it is possible to suppress the amount of engine oil from decreasing.

In the first embodiment, as described above, the second cam 42b is configured to set the opening/closing timing to close the intake valve 25a near the top dead center. Thereby, the intake air that has flowed into the cylinder 24 can be blown back to the intake passage side more effectively. Therefore, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.

In the first embodiment, as described above, the second cam 42b is configured to set the opening/closing timing of the intake valve 25a to open near the top dead center. This allows the intake valve 25a to remain open (continue to open) during almost all phases from when the piston P starts descending until it completes its ascent, thereby preventing the inside of the cylinder 24 from becoming negative pressure. can be further suppressed. Therefore, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.

In the first embodiment, as described above, at least the period when the output torque generation request is released and fuel injection from the injector is stopped (during fuel cut), or the initial period after fuel is supplied to the combustion chamber 23. The second cam 42b is configured to open and close the intake valve 25a during the period until the engine is ignited (when the engine is started). As a result, pumping loss (resistance due to the throttle valve) can be reduced when fuel is cut or when the engine is started, and the catalyst performance can be effectively exhibited.

In the first embodiment, as described above, when the second cam 42b opens and closes the intake valve 25a during the period in which the output torque generation request is canceled and fuel injection from the injector is stopped, the output torque is generated. It is configured to switch from the first cam 42a to the second cam 42b (by the intake side cam switching mechanism 4) at the timing when the ignition in the combustion chamber 23 is turned off immediately after the request is released. Thereby, it is possible to switch from the first cam 42a to the second cam 42b at an appropriate timing that matches the timing at which the fuel cut is started. Therefore, even immediately after the fuel cut is started, pumping loss (resistance due to the throttle valve) can be appropriately reduced, and the catalyst performance can be effectively exhibited.

In the first embodiment, as described above, the first cam 42a and the second cam 42b set the opening/closing timing of the intake valve 25a so that the intake valve 25a and the exhaust valve 25b do not open at the same time. It is configured. This makes it possible to reliably prevent valve overlap, thereby reliably preventing intake air from flowing to the exhaust side.

In the first embodiment, as described above, the second cam 42b controls the intake air at the movement timing of the piston P corresponding to the intake stroke and the compression stroke after supplying fuel to the combustion chamber 23 of the engine body 2 and igniting it. The opening/closing timing of the intake valve 25a is configured so that the valve 25a is maintained in an open state. As a result, at the movement timing of the piston P corresponding to the intake stroke and the compression stroke, the intake valve 25a can be kept open over a longer phase width to reduce pumping loss (resistance due to the throttle valve), and improve catalyst performance. can be demonstrated effectively.

In the first embodiment, as described above, the second cam 42b is configured such that the angular width of the opening period of the intake valve 25a is 360 degrees at the opening/closing timing of the intake valve 25a. Thereby, when the intake valve 25a moves, it is possible to reliably prevent negative pressure from being generated in the cylinder 24 (the intake passage after the throttle valve (on the downstream side)).

[Second embodiment]
A second embodiment will be described with reference to FIGS. 7 and 8. In this second embodiment, in addition to the configuration of the first embodiment, an example will be described in which the intake side cam switching mechanism 204 (an example of a "cam switching mechanism" in the claims) further includes a small cam 42c. Note that in the drawings, the same components as in the first embodiment are denoted by the same reference numerals.

As shown in FIG. 7, an engine 201 according to the second embodiment (an example of an "internal combustion engine" in the claims) includes a first cam 42a, a second cam 42b, a small cam 42c, and a power transmission section 241. The intake cam switching mechanism 204 includes an intake side cam switching mechanism 204. Note that the power transmission section 241 has a structure similar to that of the power transmission section 41 of the first embodiment, so a description thereof will be omitted.

As shown in FIG. 8, the small cam 42c is configured to set the opening/closing timing of the intake valve 25a to open near the top dead center. Further, the small cam 42c is configured to set the opening/closing timing to close the intake valve 25a on the more advanced side than the first cam 42a. Further, the maximum value R1 of the valve lift amount of the small cam 42c is smaller than the maximum value R2 of the valve lift amount of the first cam 42a.

The other configurations of the second embodiment are the same as those of the first embodiment.

(Effects of the second embodiment)
In the second embodiment, the following effects can be obtained.

In the second embodiment, as in the first embodiment, pumping loss (resistance due to the throttle valve) can be further reduced, and the catalyst performance can be more effectively exhibited.

In the second embodiment, as described above, the first cam 42a is configured to set the opening/closing timing to close the intake valve 25a on the retarded side of the bottom dead center, and the first cam 42a closes the intake valve 25a at the top dead center. It further includes a small cam 42c that opens near the bottom dead center and closes at an advance side of the bottom dead center, and is configured to be able to switch between the small cam 42c, the first cam 42a, and the second cam 42b. . This allows the small cam 42c to perform more appropriate (fine) switching of the cam according to the vehicle driving situation, thereby further reducing pumping loss (resistance due to the throttle valve). At the same time, the catalyst performance can be exhibited more effectively.

Other effects of the second embodiment are similar to those of the first embodiment.

[Modified example]
The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the description of the above embodiments, and further includes all changes (modifications) within the meaning and scope equivalent to the claims.

For example, in the first and second embodiments described above, an example was shown in which a cam switching mechanism (intake side cam switching mechanism) was provided only on the intake valve side, but the present invention is not limited to this. In the present invention, the cam switching mechanism (exhaust side A cam switching mechanism 7 (an example of a "cam switching mechanism" in the claims) may be provided. As an example, the engine 301 is configured as follows.

The engine 301 includes an exhaust side cam switching mechanism 7 including a power transmission section 71, a third cam 72a, and a fourth cam 72b. The power transmission section 71 has the same configuration as the power transmission section 41 of the first embodiment. That is, the power transmission section 71 includes a rocker arm 71a and a rocker arm 71b, and the rocker arm 71a and the rocker arm 71b are rotatably supported by a common shaft 73. The third cam 72a opens the exhaust valve 25b at a retard side than the intermediate phase between the top dead center and the bottom dead center while the piston P moves from the top dead center to the bottom dead center, and It is configured to set the opening/closing timing to close near . That is, the third cam 72a is configured to have the same valve timing as the cam 5 of the exhaust valve 25b of the first embodiment. The fourth cam 72b is configured to open and close the exhaust valve 25b near the top dead center and close the exhaust valve 25b near the top dead center (both EVO and EVC are about 0 degrees TDC). In short, the fourth cam 72b maintains the exhaust valve 25b in the open state at the movement timing of the piston P corresponding to the combustion process and exhaust process after fuel is supplied to the combustion chamber 23 of the engine body 2 and ignited. Thus, the opening/closing timing of the exhaust valve 25b is set.

Therefore, the fourth cam 72b is configured such that the angular width of the opening period of the exhaust valve 25b is 360 degrees at the opening/closing timing of the exhaust valve 25b. By providing the exhaust side cam switching mechanism 7, the exhaust valve 25b is kept open (continues to be opened) in substantially all phases from top dead center to the next top dead center.By switching to the fourth cam 72b, the exhaust valve 25b can be kept open (kept open) during almost all phases from when the piston P starts descending until it completes its ascent, so it is possible to suppress negative pressure inside the cylinder 24. can. Therefore, it is possible to suppress negative pressure in the intake passage after the throttle valve (on the downstream side), and therefore, pumping loss can be reduced.

Further, in the first and second embodiments described above, an example is shown in which the intake side cam switching mechanism is provided, but the present invention is not limited to this. In the present invention, as long as the exhaust side cam switching mechanism is provided, the intake side cam switching mechanism may not be provided.

Further, in the first and second embodiments described above, examples were shown in which there was no valve overlap between the intake valve and the exhaust valve, but the present invention is not limited to this. In the present invention, there may be valve overlap between the intake valve and the exhaust valve.

Further, in the first and second embodiments described above, an example was shown in which the intake valve is closed by the second cam near the top dead center, but the present invention is not limited to this. In the present invention, the timing at which the second cam closes the intake valve does not have to be near top dead center.

Further, in the first and second embodiments described above, an example was shown in which the number of cams to be switched by the intake side cam switching mechanism was two or three, but the present invention is not limited to this. In the present invention, the number of cams to be switched by the air side cam switching mechanism may be four or more.

Further, in the first and second embodiments described above, an example was shown in which the maximum lift amount of the second cam of the intake side cam switching mechanism was made the same as the maximum lift amount of the first cam, but the present invention is not limited to this. I can't do it. In the present invention, the maximum lift amount of the second cam may be larger or smaller than the maximum lift amount of the first cam.

Furthermore, in the first and second embodiments described above, an example was shown in which the second cam of the intake side cam switching mechanism was configured to be held (kept) for a predetermined phase width at the maximum lift amount. The invention is not limited to this. In the present invention, the second cam of the intake side cam switching mechanism is not held at the maximum lift amount for a predetermined phase width, but is instantaneously changed to the maximum lift amount in the same way as the first cam (see FIG. 5). It may be configured as follows.

1, 201, 301 Engine (internal combustion engine)
2 Engine body (internal combustion engine body)
4,204 Intake side cam switching mechanism (cam switching mechanism)
7 Exhaust side cam switching mechanism (cam switching mechanism)
23 Combustion chamber 25a Intake valve 25b Exhaust valve 42a First cam 42b Second cam 42c Small cam 72a Third cam 72b Fourth cam P Piston

Claims (10)

It includes a first cam and a second cam that open and close the intake valve,
The first cam sets the opening/closing timing to close the intake valve on the advance side of a phase intermediate between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. and the second cam is configured to set the opening/closing timing to close the intake valve on a retarded side than the intermediate phase, and to be able to switch between the first cam and the second cam,
The second cam is configured to have a cam switching mechanism configured such that the opening position of the intake valve and the closing position of the intake valve are close to each other in a phase of valve opening/closing timing. . The cam switching mechanism according to claim 1 , wherein the second cam is configured to set the opening/closing timing of the intake valve to open near the top dead center. At least during the period when the output torque generation request is released and fuel injection from the injector is stopped, or during the period from supplying fuel to the combustion chamber to ignition for the first time, the second cam controls the intake valve. The cam switching mechanism according to claim 1 or 2 , which is configured to open and close. When the second cam opens and closes the intake valve during a period in which the output torque generation request is canceled and fuel injection from the injector is stopped, the second cam opens and closes the intake valve immediately after the output torque generation request is canceled. The cam switching mechanism according to claim 3 , wherein the cam switching mechanism is configured to switch from the first cam to the second cam at a timing when ignition in a combustion chamber is turned off. The first cam and the second cam are configured to set the opening / closing timing of the intake valve so that the intake valve and the exhaust valve do not open at the same time. The cam switching mechanism according to any one of the items. an internal combustion engine body provided with an intake valve and an exhaust valve;
an intake side cam switching mechanism that opens and closes the intake valve;
The intake side cam switching mechanism is configured to open/close timing for closing the intake valve at an advanced angle side with respect to an intermediate phase between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. and a second cam that sets the opening/closing timing to close the intake valve on a retarded side than the intermediate phase, and is configured to be switchable between the first cam and the second cam. is,
In the internal combustion engine, the second cam is configured such that a position when the intake valve is open and a position when the intake valve is closed are close to each other in a phase of valve opening/closing timing. It includes a first cam and a second cam that open and close the intake valve,
The first cam sets the opening/closing timing of the intake valve to be closed at an advance side of a phase intermediate between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. , the second cam is configured to set the opening/closing timing to close the intake valve on the retarded side than the intermediate phase, and to be able to switch between the first cam and the second cam;
The second cam is a cam switching mechanism configured to set the opening/closing timing for closing the intake valve near the top dead center. It includes a first cam and a second cam that open and close the intake valve,
The first cam sets the opening/closing timing of the intake valve to be closed at an advance side of a phase intermediate between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. , the second cam is configured to set the opening/closing timing to close the intake valve on the retarded side than the intermediate phase, and to be able to switch between the first cam and the second cam;
The first cam is configured to set the opening/closing timing of the intake valve at a position retarded from the bottom dead center,
further comprising a small cam that sets the opening/closing timing of the intake valve to open near the top dead center and close on the advance side of the bottom dead center,
A cam switching mechanism configured to be able to switch between the small cam, the first cam, and the second cam. an internal combustion engine body provided with an intake valve and an exhaust valve;
an intake side cam switching mechanism that opens and closes the intake valve;
In the case where the intake side cam switching mechanism is provided, the intake side cam switching mechanism is configured to move the intake valve between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. a first cam that sets the opening/closing timing to close the intake valve at an advanced angle side than the intermediate phase; and a second cam that sets the opening/closing timing to close the intake valve at a retarded side than the intermediate phase; and the second cam,
In the internal combustion engine, the second cam is configured to set the opening/closing timing for closing the intake valve near the top dead center. an internal combustion engine body provided with an intake valve and an exhaust valve;
an intake side cam switching mechanism that opens and closes the intake valve;
In the case where the intake side cam switching mechanism is provided, the intake side cam switching mechanism is configured to move the intake valve between the bottom dead center and the top dead center while the piston moves from the bottom dead center to the top dead center. a first cam that sets the opening/closing timing to close the intake valve at an advanced angle side than the intermediate phase; and a second cam that sets the opening/closing timing to close the intake valve at a retarded side than the intermediate phase; and the second cam,
The first cam is configured to set the opening/closing timing of the intake valve at a position retarded from the bottom dead center,
further comprising a small cam that sets the opening/closing timing of the intake valve to open near the top dead center and close on the advance side of the bottom dead center,
An internal combustion engine configured to be able to switch between the small cam, the first cam, and the second cam.

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