JPH07238845A - Variable valve switching control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the durability of a cam switching mechanism while improving the running safety according to the operating condition. CONSTITUTION:A converting standard engine rotational speed VVLN according to the gear position is retrieved from a map, and when the engine rotational speed Ne exceeds the converting standard engine rotational speed VVLN, a change-over valve 103 is controlled by a control unit 102 so as to open and close an intake valve by a cam for high speed. And when the speed Ne does not exceeds, the valve 103 is controlled to open and close the intake valve by a cam for low speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve switching control device for an internal combustion engine, and more particularly to a technique for switching and controlling valve characteristics while improving traveling safety according to operating conditions.

[0002]

2. Description of the Related Art Conventionally, the lift characteristic (opening / closing characteristic) of an intake valve or an exhaust valve has been changed for the purpose of achieving both high torque characteristics at low and medium speed operation and improved output at high speed operation.
For example, it is known that the high-speed cam and the low-speed cam are selectively used according to operating conditions, thereby making them different, and thereby controlling the intake / exhaust timing or intake / exhaust amount (Japanese Patent Laid-Open No. 63-167016). Gazette, JP-A-63-
57805, JP-A-5-171909, etc.).

By switching the valve lift characteristics as described above (using the high speed cam and the low speed cam properly),
As shown in FIG. 12, the torque characteristic in the low speed range and the torque characteristic in the high speed range are combined, and the torque can be increased from the low speed range to the high speed range.

[0004]

By the way, as described above, in order to control the switching between the valve opening characteristic corresponding to the high speed range and the valve opening characteristic corresponding to the low speed range, the engine rotational speed is set to a preset reference value. Based on the result of determination as to whether or not the rotational speed is exceeded, it has been decided whether to use the high-speed valve (high-speed cam) or the low-speed valve (low-speed cam) as the valve opening characteristic.

As shown in FIG. 12, the reference rotational speed is a boundary at which the output torque is substantially the same between the low speed characteristic and the high speed characteristic, and the characteristic is switched with the reference rotational speed as a boundary. Thus, it is possible to obtain higher torque in each speed range divided by the reference rotation speed while avoiding the occurrence of a torque step due to the switching of the valve opening characteristic.

However, in the above-described valve opening characteristic switching control based on the engine rotation speed, since the cam switching is performed at the reference rotation speed regardless of the traveling conditions, unnecessary sudden acceleration and sudden start occur, and traveling safety is improved. There was a problem that could not be secured. For example, when the engine speed exceeds the reference speed due to an accelerator operation error when the vehicle is being parked in low gear or back gear, the low-speed cam switches to the high-speed cam, resulting in unnecessary and sudden acceleration. May lead to.

Further, when the engine rotation speed exceeds the reference rotation speed due to an accelerator operation error or an accelerator operation at the time of slippage during low gear running on a rough road, the low speed cam is switched to the high speed cam, and unnecessary sudden acceleration or sudden acceleration occurs. There is a risk of starting the vehicle and leading to an accident. Furthermore, when switching is performed at a place where the torque difference is small during traveling at the 2nd speed, the low speed cam and the high speed cam are easily switched frequently near the switching point, and the durability of the cam switching mechanism is improved. There was a problem that was worse.

The present invention has been made in view of the above conventional problems, and a variable valve for an internal combustion engine in which the durability of the cam switching mechanism is improved while improving the running safety according to the operating condition. An object is to provide a switching control device.

[0009]

In order to achieve the above object, the invention of claim 1 is, as shown in FIG. 1, a valve characteristic switching means for switching a plurality of preset valve characteristics and a transmission. Gear position detecting means for detecting a gear position, reference switching point setting means for setting a reference switching point of valve characteristics based on a condition including the gear position detected by the gear position detecting means, and based on the reference switching point And a switching control unit that controls the switching operation of the valve characteristic by the valve characteristic switching unit.

Further, the invention of claim 2 further includes a rotation speed detecting means for detecting a rotation speed of the engine, and the reference switching point setting means sets the reference switching point as a reference rotation speed corresponding to a gear position. The switching control means, based on a comparison between the engine rotation speed detected by the rotation speed detection means and the reference rotation speed set by the reference switching point setting means, determines the valve characteristic of the valve characteristic switching means. The switching operation can be controlled.

Further, the invention of claim 3 is characterized in that the valve characteristic switching means is configured to switch a cam for opening and closing the valve to either one of a high speed cam and a low speed cam, and the switching control means, The control may be switched to the high speed cam when the engine rotation speed is higher than the reference rotation speed, and may be switched to the low speed cam when the engine rotation speed is lower than the reference rotation speed.

Further, the invention of claim 4 includes a vehicle speed detecting means for detecting a vehicle speed and a basic fuel injection amount setting means for setting a basic fuel injection amount to be supplied to the engine, and the reference switching point setting means. Is for setting a reference switching point as a reference fuel injection amount based on a gear position and a vehicle speed, and the switching control means performs a valve characteristic switching operation by the valve characteristic switching means based on the reference fuel injection amount. It may be configured to control.

Further, the invention according to claim 5 is characterized in that the valve characteristic switching means switches the cam for opening and closing the valve to one of a high speed cam and a low speed cam, and the switching control means comprises: When the basic fuel injection amount set by the basic fuel injection amount setting means is larger than the reference fuel injection amount set by the reference switching point setting means, switching control is performed to the high speed cam, while the basic fuel injection amount is It may be configured to control the switching to the low speed cam when the amount is smaller than the reference fuel injection amount.

[0014]

According to this structure, in the invention of claim 1, the switching control means performs the valve characteristic switching operation by the valve characteristic switching means based on the reference switching point according to the gear position set by the reference switching point setting means. To control.
That is, for example, in a low speed operation state in which the gear position is neutral N, reverse R, and first speed, the reference switching point setting means is
The reference switching point of valve characteristics is set to a position where unintentional switching can be prohibited, and the switching operation of valve characteristics is controlled by the reference switching point to prevent unnecessary sudden acceleration or sudden start. be able to.

Further, when the gear position is the second speed medium speed operation state, the valve characteristic reference switching point is set to a position where frequent switching can be reduced, and the valve characteristic switching operation is controlled by the reference switching point. As a result, the number of switching of valve characteristics can be reduced. Further, in the high speed operation state where the gear position is the 3rd speed to the 5th speed, the reference switching point of the valve characteristic is set to a position where the occurrence of the torque step due to the switching can be prevented, and the switching operation of the valve characteristic is performed by the reference switching point. By controlling, it is possible to prevent the driving shock due to the torque step when switching the valve characteristics.

As described above, the traveling safety can be ensured according to the driving condition, and the number of times of operation of the valve characteristic switching means can be reduced, so that the durability of the valve characteristic switching means can be improved. . Further, in the invention of claim 2, the switching control means uses the valve characteristic switching means based on the comparison between the engine rotation speed detected by the rotation speed detection means and the reference rotation speed set by the reference switching point setting means. Controls the characteristic switching operation.

Further, in the invention of claim 3, the valve characteristic switching means is configured to switch the cam for opening and closing the valve to either one of the high speed cam and the low speed cam, and the switching control means makes the engine rotation. When the speed is higher than the reference rotation speed, the cam is switched to the high speed cam, and when the engine speed is lower than the reference rotation speed, the low speed cam is controlled to be switched.

Further, in the invention of claim 4, the switching control means controls the valve characteristic switching operation by the valve characteristic switching means based on the reference fuel injection amount set based on the gear position and the vehicle speed. That is, for example, in the low speed operation state in which the gear position is neutral N, reverse R, or 1st speed among a plurality of map tables in which the reference fuel injection amount is stored in advance using the vehicle speed as a parameter, the switching point of the valve characteristic is careless. Select a map table that is set to prohibit switching, and select a map table that is set to reduce frequent switching when the gear position is 2 speed and medium speed operation. Is 3
In the high speed to fifth speed operating state, a map table set so as to prevent the occurrence of a torque step due to switching is selected, and the reference fuel injection amount corresponding to the vehicle speed retrieved from the selected map table is selected. Based on this, the switching operation of the valve characteristics is controlled.

According to this, it is possible to obtain substantially the same effect as the invention of claim 1. Further, in the invention of claim 5, the valve characteristic switching means is configured to switch the cam for opening and closing the valve to one of the high speed cam and the low speed cam, and the switching control means sets the basic fuel injection amount setting. When the basic fuel injection amount set by the means is larger than the reference fuel injection amount set by the reference switching point setting means, switching control is performed to the high speed cam, while the basic fuel injection amount is smaller than the reference fuel injection amount. Control to switch to low speed cam.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, the engine 1 is provided with a variable valve mechanism 101 (valve characteristic switching means) that selectively switches a plurality of preset valve opening / closing characteristics (lift characteristics).

The variable valve mechanism 101 is a hydraulic variable mechanism that switches the valve opening / closing characteristics by operating hydraulic pressure. The operating hydraulic pressure is supplied by the control unit 10.
It is configured to be adjusted by the switching valve 103 which is driven and controlled by 2. The control unit 102 having a built-in microcomputer inputs detection signals from a crank angle sensor 104 for detecting the engine rotation speed Ne, a gear position sensor 105 for detecting the gear position, etc., and based on these detection signals, valve characteristics Is determined and the switching valve 103 is controlled according to the determination.

Here, the variable valve mechanism 101 will be described with reference to FIGS. That is, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves V, and the base end of the rocker arm 1 is provided with a hollow main rocker shaft 3 common to each cylinder. The rocker arm 1 is swingably supported by the cylinder head, and each forked end of the rocker arm 1 contacts the stem top of the intake valve V.

A free cam follower 2 is provided substantially above the center of the rocker arm 1, and both ends of the free cam follower 2 are in contact with the low speed cams 21 and 21 for the roller 1.
1, 11 are provided. These rollers 11, 11 are
A bearing shaft 12 inserted through a through hole 13 provided in the rocker arm 1 is rotatably supported via a needle bearing 14.

The base end of the free cam follower 2 is swingably (relatively rotatable) supported by the rocker arm 1 via the sub-rocker shaft 16. The free cam follower 2 does not have a portion that comes into contact with the intake valve V, and a cam follower portion 2A that slidably contacts the high speed cam 22 is formed at the tip thereof so as to project in an arc shape. Further, a recess 27 into which a spring retainer 29 is slidably fitted is formed below the free cam follower 2, and the spring retainer 29 is provided.
Has a base end abutting against the rocker shaft 3 by the elastic biasing force of the coil spring 26 supported by the bottom surface of the recess 27.

Further, the free cam follower 2 described above has a stepped portion 2B with which a later-described lever member 7 is engaged and an inclined portion 2C continuous with the stepped portion 2B, which is formed below the cam follower 2 portion 2A. Further, below the rocker arm 1, there is provided a lever member 7 which is swingably supported by a pin 6 on the side of the rocker shaft 3. A protrusion 7A is integrally formed on the upper side of the lever member 7, and a return spring 9 and a spring retainer 10 housed in a recess 8 formed in the rocker arm 1 are engaged with the free cam follower 2 described above. Is urged in the direction to be released.

On the other hand, the lower end portion of the lever member 7 is in contact with the operating plunger 31 driven by the supply of the operating hydraulic pressure to the hydraulic chamber 34 provided in the rocker arm 1. An oil passage for guiding the operating oil pressure to the oil pressure chamber 34 is provided through the rocker arm 1 and the main rocker shaft 3. The rocker arm 1 is formed with a through hole 41 having one end opened to the hydraulic chamber 34 and the other end penetrating the bearing surface for the main rocker shaft 3. An oil gallery 42 is axially formed inside the main rocker shaft 3.
Communicates with the through hole 41 of the rocker arm 1 through the through hole 43.

A discharge hydraulic pressure of an oil pump (not shown) driven by an engine is selectively introduced into the oil gallery 42 via a switching valve 103 whose operation is controlled by the control unit 102. The low speed cams 21 and 21 and the high speed cam 22 between them are
The camshafts 20 are formed integrally with each other, and have different shapes so as to satisfy the valve lift characteristics (opening / closing characteristics) required at low engine speed and high engine speed. That is, the high speed cam 22 has a profile in which at least one of the valve lift amount and the valve open period is larger than that of the low speed cam 21. Here, the valve lift amount and the open period are both increased, and the valve characteristics can be switched to two types by properly using the high speed cam 22 and the low speed cam 21.

According to the variable valve mechanism 101 having the above-described structure, when the hydraulic pressure is not supplied to the hydraulic chamber 34, the rocker arm 1 swings according to the cam profile of the low speed cam 21 to open / close each intake valve V. . At this time, although the free cam follower 2 is swung by the high speed cam 22, the lever member 7 is in the position shown by the solid line in FIG. 5 due to the urging force of the return spring 9, and the lost motion mechanism 25 exerts its function. Coordinated at 1 position. Therefore, even if there is an input from the free cam follower 2, the motion of the rocker arm 1 is not hindered by only bending of the lost motion spring 26.

On the other hand, when the operating hydraulic pressure is introduced into the hydraulic chamber 34 through the oil gallery 42 and the oil passage 41 during the high speed operation of the engine, the operating plunger 31 causes the lever member 7 to apply the biasing force of the return spring 9. Rocking against
It is brought to a second position shown by a broken line in FIG. In this state,
The end of the lever member 7 is a step 2B of the free cam follower 2.
By engaging with the rocker arm 1, the rocker arm 1 and the free cam follower 2 are connected and integrated, and swing about the main rocker shaft 3.

The high speed cam 22 is the low speed cam 21.
By comparison, since the valve opening and the valve lift amount are both large, when the free cam follower 2 and the rocker arm 1 swing together, the rocker arm 1
Roller 11 floats up from the low speed cam 21, and each intake valve V is driven to open and close according to the profile of the high speed cam 22, so that both the valve opening degree and the valve lift amount increase.

On the other hand, the high speed cam 22 to the low speed cam 21
Switching to the hydraulic chamber 34 is controlled by the switching valve 103.
This is done by lowering the hydraulic pressure guided to the lever, moving the lever member 7 and the actuating plunger 31 to the original position (the solid line position in FIG. 5) by the elastic biasing force of the return spring 9, and releasing the restraint of the rocker arm 1. . As described above, by selectively supplying the operating oil pressure to the hydraulic chamber 34 by the switching valve 103, the valve opening characteristic adapted to the low speed range according to the profile of the low speed cam 21 and the low speed according to the profile of the high speed cam 22 are provided. Either the valve opening characteristic or the valve opening characteristic that is suitable for a high speed range in which both the valve opening degree and the valve lift amount are larger than those of the use cam 21 can be switched and selected.

In this embodiment, the valve characteristic switching means includes the rocker arm 1, the free cam follower 2, and the free cam follower 2.
The lever member 7, the actuating plunger 31, the switching valve 103 and the like are included. In the present embodiment, the high speed cam 22
As described above, the switching between the low speed cam 21 and the low speed cam 21 is performed depending on whether or not the rocker arm 1 and the cam follower 2 are connected by the swing of the lever member 7, but the cam switching mechanism is described above. It is not limited.

For example, as disclosed in JP-A-63-167016 and JP-A-63-57805, a high speed rocker arm and a low speed rocker arm are fitted in a direction parallel to the rocker shaft. Alternatively, the high speed cam 22 and the low speed cam 21 may be switched by selectively connecting and disconnecting the hole and the plunger.

Further, instead of using a plurality of cams selectively, a cam sprocket capable of controlling the phase while maintaining a constant operating angle is attached to the cam shaft, and the intake valve opening / closing timing can be switched to an appropriate timing for each speed range. Valve timing controller ("New model vehicle manual (FGY32-
1) ”, pages B-44 to 45, edited and published by Nissan Motor Co., Ltd., published in August 1991), and does not limit the configuration of the variable valve mechanism 101.

In this embodiment, the functions as the reference switching point setting means and the switching control means are as shown in FIGS.
Control unit 1 as shown in the flow chart
02 is equipped with software. Next, an example of switching control of valve characteristics (high speed cam and low speed cam) performed by the control unit 102 via the switching valve 103 will be described with reference to the flowchart of FIG.

First, in step 1 (hereinafter referred to as "S1"), the gear position detected by the gear position sensor 105 (for example, neutral N, reverse R, first speed ...
(5th speed) is read. In S2, the switching reference engine rotation speed VVLN corresponding to the gear position is retrieved from the map and set.

As shown in FIG. 8, this map shows the reference engine rotation speed VVLN for switching from the low speed cam 21 to the high speed cam 22 in the low speed operation state where the gear position is neutral N, reverse R and the first speed. Switching from the low-speed cam 21 to the high-speed cam 22 is prohibited to prevent unnecessary sudden acceleration and sudden start. For example, a high rotation speed of 9000 rpm is set.

Further, when the gear position is the second speed medium speed operation state, the number of switching from the low speed cam 21 to the high speed cam 22 can be reduced, for example, 6000 rpm is set. Further, in a high speed operation state in which the gear position is the third speed to the fifth speed, it is possible to prevent a driving shock due to a torque step when switching from the low speed cam 21 to the high speed cam 22, for example, 5000
Set to rpm.

In S3, the engine rotation speed Ne detected from the crank angle sensor 104 is read, and in S4, the engine rotation speed Ne and the switching reference engine rotation speed VVLN.
Compare with. If Ne exceeds VVLN, the switching valve 103 is controlled so that the intake valve V is opened and closed by the high speed cam 22 in S5. In particular,
The switching valve 10 so that the hydraulic oil is supplied to the hydraulic chamber 34.
3, the end of the lever member 7 is engaged with the step 2B of the free cam follower 2, whereby the rocker arm 1 and the cam follower 2 on which the high speed cam 22 slides are connected and integrated. , So as to swing around the main rocker shaft 3.

On the other hand, if Ne does not exceed VVLN in S4, the process proceeds to S6, and the switching valve 103 is controlled so that the low speed cam 21 opens and closes the intake valve V. Specifically, the switching valve 103 is controlled so as to reduce the hydraulic pressure in the hydraulic chamber 34, whereby the engagement between the rocker arm 1 and the free cam follower 2 is released. Where S2 is
As the reference switching point setting means, S4 to S6 function as the switching control means.

In this way, the switching reference engine rotation speed VVLN is set according to the gear position, and the high speed cam 22 and the low speed cam 21 are switched based on the reference engine rotation speed VVLN (switching of valve opening / closing characteristics). In the low speed operation state in which the gear position is neutral N, reverse R, and 1st speed, for example, as shown in FIG. 9, the reference engine rotation speed VVLN is set to around 9000 rpm so that Cam 21 to high speed cam 2
Switching to 2 can be prohibited to prevent unnecessary sudden acceleration and sudden start.

Further, in the medium speed operation state where the gear position is the second speed, the number of switching from the low speed cam 21 to the high speed cam 22 can be reduced by setting the speed to 6000 rpm, for example. Further, in a high speed operation state in which the gear position is the third speed to the fifth speed, for example, by setting it to 5000 rpm, it is possible to prevent a driving shock due to a torque step when switching from the low speed cam 21 to the high speed cam 22. .

As described above, the traveling safety can be improved according to the driving condition, and the variable valve mechanism 1 can be used.
Since the number of operations of 01 can be reduced, the variable valve mechanism 1
The durability of 01 can be improved. Next, another embodiment will be described with reference to FIGS. That is, in FIG. 10, the control unit 102 has a crank angle sensor 104 as a rotation speed detecting means for detecting the rotation speed Ne of the engine and a gear position sensor 10 as a gear position detecting means for detecting a gear position.
5, detection signals from a vehicle speed sensor 106 as a vehicle speed detection means for detecting the vehicle speed VSP, an air flow meter 107 for detecting the intake air flow rate Q of the engine, etc. are input, and the control unit 102 controls the valve characteristics based on these detection signals. Is determined and the switching valve 103 is controlled according to the determination.

Next, the operation of this one will be described with reference to the flowchart of FIG. First, step 11
(Hereinafter, referred to as “S11”), the gear position sensor 10
5 detected gear position (eg neutral N,
Reverse R, first speed to fifth speed) is read and input to the control unit 102. In S12, a map table in which the reference fuel injection amount is stored in advance using the vehicle speed as a parameter, which is set according to the gear position, is selected. This map table is selected, for example, by selecting a map table that is set so that inadvertent switching can be prohibited in a low speed operation state where the gear position is neutral N, reverse R, and 1st speed. Select a map table that is set to reduce frequent switching in high-speed to medium-speed operating state, and prevent torque step due to switching in high-speed operating state in which the gear position is 3rd to 5th speed. Select a map table that is set to be able to.

In S13, the vehicle speed VSP detected by the vehicle speed sensor 106 is read, and the control unit 1
Enter in 02. In S14, the reference fuel injection amount VVLTp corresponding to the vehicle speed VSP is searched from the map table selected in S12. In S15, the control unit 102 controls the basic fuel injection amount T based on the engine speed Ne detected by the crank angle sensor 104 and the intake air flow rate Q detected by the air flow meter 107.
Calculate p.

In S16, the basic fuel injection amount Tp is compared with the reference fuel injection amount VVLTp. When Tp is larger than VVLTp, the switching valve 103 is controlled so that the intake valve V is opened and closed by the high speed cam 22 in S17. Specifically, the switching valve 103 is controlled so that the hydraulic oil is supplied to the hydraulic chamber 34, whereby the end portion of the lever member 7 is engaged with the step portion 2B of the free cam follower 2, whereby The rocker arm 1 and the cam follower 2 on which the high speed cam 22 slides are connected and integrated so as to swing about the main rocker shaft 3.

On the other hand, when Tp does not exceed VVLTp, the routine proceeds to S18, where the switching valve 103 is controlled so that the low speed cam 21 opens and closes the intake valve V. Specifically, the switching valve 103 is controlled so as to reduce the hydraulic pressure in the hydraulic chamber 34, whereby the engagement between the rocker arm 1 and the free cam follower 2 is released. Where S12
To S14 are S16 to S1 as the reference switching point setting means.
8 functions as switching control means.

In this way, by separately providing a switching map according to the gear position and controlling the switching between the low speed cam 21 and the high speed cam 22, the same as in the above embodiment, depending on the operating state. Since the traveling safety can be improved and the number of times of operation of the variable valve mechanism 101 can be reduced, the durability of the variable valve mechanism 101 can be improved.

[0049]

As described above, according to the present invention,
A reference switching point setting means for setting a reference switching point of valve characteristics based on a condition including a gear position detected by the gear position detecting means, and a valve characteristic switching operation by the valve characteristic switching means based on the reference switching point. Since it has a switching control means for controlling, depending on the operating state,
The traveling safety can be improved, and the number of times of operation of the valve characteristic switching means can be reduced, so that the durability of the valve characteristic switching means can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a variable valve switching control device for an internal combustion engine according to the present invention.

FIG. 2 is a system diagram showing an overall configuration of an embodiment of the present invention.

FIG. 3 is a plan view showing a variable valve mechanism according to an embodiment of the present invention.

4 is a sectional view taken along line IV-IV in FIG.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 8 is a map table in which reference rotational speeds are stored in advance using gear positions as parameters.

FIG. 9 is a valve switching characteristic diagram for explaining the operation of one embodiment.

FIG. 10 is a system diagram showing the overall configuration of another embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of another embodiment of the present invention.

FIG. 12 is a valve switching characteristic diagram for explaining problems of the conventional technique.

[Explanation of symbols]

 1 rocker arm 2 free cam follower 3 main rocker shaft 7 lever member 9 return spring 11 roller 16 sub-rocker shaft 21 low speed cam 22 high speed cam 25 lost motion mechanism 26 spring 31 actuating plunger 34 hydraulic chamber 42 oil gallery 101 variable valve mechanism 102 Control unit 103 Switching valve 104 Crank angle sensor 105 Gear position sensor 106 Vehicle speed sensor 107 Air flow meter V Intake valve

Claims (5)

[Claims] 1. A valve characteristic switching means for switching a plurality of preset valve characteristics, a gear position detecting means for detecting a gear position of a transmission, and a condition including a gear position detected by the gear position detecting means. A reference switching point setting means for setting the reference switching point of the valve characteristic based on the reference switching point; and a switching control means for controlling the switching operation of the valve characteristic by the valve characteristic switching means based on the reference switching point. A variable valve switching control device for an internal combustion engine, comprising: 2. A rotation speed detecting means for detecting a rotation speed of an engine, wherein the reference switching point setting means sets a reference switching point as a reference rotation speed according to a gear position, and the switching control means. Controls the switching operation of the valve characteristic by the valve characteristic switching means based on the comparison between the engine rotational speed detected by the rotational speed detection means and the reference rotational speed set by the reference switching point setting means. The variable valve switching control device for an internal combustion engine according to claim 1, wherein: 3. The valve characteristic switching means is configured to switch a cam for opening and closing the valve to one of a high speed cam and a low speed cam, and the switching control means sets the engine rotation speed to a reference rotation speed. 3. The variable valve for an internal combustion engine according to claim 2, wherein when the engine rotational speed is smaller than a reference rotational speed, the control is switched to the low speed cam when the engine rotational speed is smaller than a reference rotational speed. Switching control device. 4. A vehicle speed detecting means for detecting a vehicle speed, and a basic fuel injection amount setting means for setting a basic fuel injection amount to be supplied to an engine, wherein the reference switching point setting means uses a reference switching point as a gear. The reference fuel injection amount is set based on the position and the vehicle speed, and the switching control means controls the valve characteristic switching operation by the valve characteristic switching means based on the reference fuel injection amount. Claim 1 characterized by
A variable valve switching control device for an internal combustion engine as described above. 5. The valve characteristic switching means is configured to switch a cam for opening and closing the valve to one of a high speed cam and a low speed cam, and the switching control means includes the basic fuel injection amount setting means. When the basic fuel injection amount set by is larger than the reference fuel injection amount set by the reference switching point setting means, switching control is performed to the high speed cam, while the basic fuel injection amount is smaller than the reference fuel injection amount. 5. The variable valve switching control device for an internal combustion engine according to claim 4, wherein switching control is performed to the low speed cam.