JPH07217419A - Variable valve changeover control device for engine - Google Patents

Abstract

PURPOSE:To avoid generation of torque difference when changeover is conducted between a high speed cam and a low speed cam. CONSTITUTION:An absolute value of an intake amount is obtained under the condition that same intake amounts are alloted to respective cams, in every engine speed. The obtained absolute value is a reference air amount Qs used for judgment of a changeover timing (S2). The reference air amount Qs is compated to an actually detected engine intake amount Q (S4). When the actual air amount exceeds the reference air amount Qs, changeover is conducted to a high speed cam (S5). On the contrary, when the actual air amount Q is less than the reference air amount Qs, changeover is conducted to a low speed cam.

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 engine, and more particularly to a technique for switching and controlling valve opening characteristics while avoiding the occurrence of a torque step.

[0002]

2. Description of the Related Art Conventionally, the lift characteristic (opening characteristic) of an intake valve or an exhaust valve is changed to, for example, a high-speed cam for the purpose of achieving both high torque characteristics at low and medium speed operation and improved output at high speed operation. It is known that the low-speed cam and the low-speed cam are used differently depending on operating conditions, and thereby the intake / exhaust timing or the intake / exhaust amount is controlled (Japanese Patent Laid-Open Nos. 63-167016 and 63/63). -5780
5 and JP-A-5-171909).

By switching the valve lift characteristics as described above (using the high speed cam and the low speed cam properly),
As shown in FIG. 8, 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, when the valve opening characteristic corresponding to the high speed range and the valve opening characteristic corresponding to the low speed range are switched and controlled, the engine rotation speed is set in advance. Based on the result of determination as to whether or not the reference rotation speed is exceeded, it was decided whether to use the high-speed valve (high-speed cam) or the low-speed valve (low-speed cam) as the valve opening characteristic. .

The reference rotational speed is, as shown in FIG.
This is a boundary where the output torques of the low-speed characteristic and the high-speed characteristic become substantially the same, and by switching the characteristics at the reference rotation speed, it is possible to avoid the occurrence of a torque step due to the switching of the valve opening characteristics. At the same time, a higher torque is obtained in each speed range divided by the reference rotation speed.

However, in the above-mentioned switching control of the valve opening characteristic based on the engine rotation speed, it is not possible to stably carry out the switching that does not cause a large torque step, and it becomes large when the valve characteristic (used cam) is switched. There was a case where a torque step was generated and a driving shock was generated. The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to reliably avoid the occurrence of a large torque step when switching the opening characteristics of a valve.

[0007]

Therefore, the variable valve switching control device for an engine according to the invention of claim 1 is constructed as shown in FIG. In FIG. 1, the valve opening characteristic switching means switches the valve opening characteristic of the engine to a plurality of preset types.

Further, the reference air amount setting means sets the reference air amount based on the engine speed detected by the engine speed detecting means. Then, the air amount switching control means switches the valve opening characteristic based on a comparison between the intake air amount of the engine detected by the intake air amount detecting means and the reference air amount set by the reference air amount setting means. The switching operation of the valve opening characteristic by the means is controlled.

Here, in the apparatus according to the second aspect of the present invention, the valve opening characteristic switching means switches the cam for opening and closing the valve to one of the high speed cam and the low speed cam. The air amount switching control means controls switching to the high-speed cam when the intake air amount of the engine is larger than the reference air amount,
When the intake air amount of the engine is smaller than the reference air amount, the control is switched to the low speed cam.

[0010]

In the engine variable valve switching control device according to the first aspect of the present invention, the intake air amount of the engine is compared with the reference air amount set based on the rotation speed of the engine. Then, depending on the comparison result, that is, whether the actually detected air amount is larger or smaller than the reference air amount, it is judged which valve opening characteristic should be used, and the actual valve opening characteristic is determined accordingly. Is switched.

The switching of the valve opening characteristic is required to be performed under the condition that substantially the same torque is obtained between the characteristic before switching and the characteristic after switching. On the other hand, the engine output torque is the engine intake air amount (cylinder intake air amount).
The absolute value of the intake air amount under the condition that the engine intake air amount is the same in each open characteristic varies depending on the engine rotation speed.

Therefore, the engine intake air amount (reference air amount) which becomes the switching timing depending on the engine rotation speed
Is set, and which open characteristic is to be used is determined depending on whether the actual engine intake air amount is larger or smaller than the reference air amount. On the other hand, in the device according to the invention of claim 2, the valve is opened / closed by using one of the high speed cam and the low speed cam, and the actual engine intake air amount is compared with the reference air amount. hand,
The high-speed cam is used when the intake air amount exceeds the reference air amount, and the low-speed cam is used when the intake air amount less than the reference air amount is obtained.

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 2 is a block diagram showing the outline of the system configuration of this embodiment.
In FIG. 2, an engine (not shown) is provided with a variable valve mechanism 101 (valve opening characteristic switching means) that selectively switches the valve opening characteristic (lift characteristic) among a plurality of preset types.

The variable valve mechanism 101 is a hydraulic variable mechanism that switches the valve opening characteristic by operating hydraulic pressure. The operating hydraulic pressure is supplied to the control unit 102.
It is configured to be adjusted by the switching valve 103 which is driven and controlled by. The control unit 102 having a built-in microcomputer controls the engine rotation speed Ne.
Rotation speed sensor 104 (rotation speed detection means) for detecting
A detection signal from an air flow meter 105 (intake air amount detecting means) for detecting the intake air flow rate Qa of the engine is input, and the valve opening characteristic is determined based on these detection signals.
The switching valve 103 is controlled according to the determination.

That is, in this embodiment, the control unit 102 detects the switching timing of the valve opening characteristic based on the engine speed Ne and the intake air flow rate Qa, and controls the valve opening characteristic through the drive control of the switching valve 103. Switch. Therefore, the control unit 102 corresponds to the switching control means according to the air amount in this embodiment.

3 to 6 show the variable valve mechanism.
A specific example of 101 is shown. Explaining this, each cylinder is provided with a single rocker arm 1 corresponding to two intake valves V. The base end of the rocker arm 1 is swingably supported by the cylinder head through a hollow main rocker shaft 3 common to each cylinder, and the bifurcated ends of the rocker arm 1 abut the stem top of the intake valve V. .

The rocker arm 1 is formed into a substantially bifurcated shape in a plan view, and the rocker arm 1 is provided with a single free cam follower 2 approximately above the center thereof. And FIG.
At both sides of the free cam follower 2, low speed cam 2
Rollers 11, 11 with which 1, 21 abut are provided. The base end of the free cam follower 2 is swingably (relatively rotatable) supported by the rocker arm 1 via a 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 of the free cam follower 2 so as to project in an arc shape.

A recess 27 into which a spring retainer 29 is slidably fitted is formed on the lower side of the free cam follower 2, and the base end of the spring retainer 29 is supported on the bottom surface of the recess 27. The elastic biasing force of the coil spring 26 makes contact with the rocker shaft 3. Further, in the free cam follower 2 described above, below the cam follower portion 2A, a step portion 2B with which a later-described lever member 7 engages and an inclined portion 2C continuous with this are formed. 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 7 is provided on the upper side of the lever member 7.
A is integrally formed and is urged by a return spring 9 and a spring retainer 10 housed in a recess 8 formed in the rocker arm 1 in a direction in which the engagement with the free cam follower 2 is released. On the other hand, at the lower end of the lever member 7, an operating plunger 31 driven by the supply of operating hydraulic pressure to the hydraulic chamber 34 provided in the rocker arm 1.
Are in contact.

The oil passage for guiding the working hydraulic pressure to the hydraulic chamber 34 is
It is provided through the inside of 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. Also,
An oil gallery 42 is axially formed inside the main rocker shaft 3, and the oil gallery 42 communicates with a through hole 41 of the rocker arm 1 through a 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. Low speed cam 2
1, 21 and the high speed cam 22 between them are integrally formed on a common cam shaft 20, and satisfy the valve lift characteristics (open characteristics) required at low engine speed and high engine speed. Are formed in different shapes.
That is, the high speed cam 22 has a cam profile that makes at least one of the valve lift amount and the valve open period larger than the low speed cam 21. In this embodiment, the valve lift amount and the opening period are both increased, and the valve opening characteristic can be switched between two types by properly using the high speed cam 22 and the low speed cam 21. There is.

According to the variable valve mechanism 101 having the above structure,
In a state in which 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 moved by the biasing force of the spring 9 as shown in FIG.
Is in the position shown by the solid line. Therefore, the free cam follower 2
Even if there is an input from, only the spring 26 bends and the movement of the rocker arm 1 is not affected.

On the other hand, when the working hydraulic pressure is supplied to the hydraulic chamber 34, the working plunger 31 swings the lever member 7 against the return spring 9 and returns it to the position shown by the broken line in FIG. . In this state, the end portion of the lever member 7 engages with the step portion 2B of the free cam follower 2 so that the rocker arm 1 and the cam follower 2 are connected and integrated, and swing about the main rocker shaft 3. become.

Since the high speed cam 22 is formed so that both the valve opening angle and the valve lift amount are larger than the low speed cam 21, the free cam follower 2 is integrated with the rocker arm 1. Rocker arm 1 when rocking
Roller 11 floats up from low speed cam 21, and each intake valve V is driven to open and close according to the profile of high speed cam 22, so that both the opening angle and the lift amount increase.

On the other hand, switching from the high speed cam 22 to the low speed cam 21 lowers the hydraulic pressure introduced into the hydraulic chamber 34 by the control of the switching valve 103, and the elastic restoring force of the return spring 9 causes the lever member 7 and the actuating plunger. This is performed by moving 31 to the original position (the position indicated by the solid line in FIG. 5) and releasing the lock of the rocker arm 1. In this way, the switching valve
By selectively supplying the hydraulic pressure to the hydraulic chamber 34 by the 103, the valve opening characteristic that conforms to the profile of the low speed cam 22 in the low speed range and the opening characteristic of the high speed cam 21 that is higher than that of the low speed cam 22 are provided. Either the angle or the valve opening characteristic suitable for the high speed range where the lift amount is large can be switched and selected.

In this embodiment, the valve opening characteristic switching means is constituted by the rocker arm 1, the free cam follower 2, the lever member 7, the plunger 31, the hydraulic chamber 34, the switching valve 103 and the like. In the present embodiment, switching between the high speed cam 21 and the low speed cam 22 is performed depending on whether or not the rocker arm 1 and the cam follower 2 are connected by swinging the lever member 7 as described above. However, the cam switching mechanism is not limited to the above.

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

Further, it is possible to attach a cam sprocket capable of controlling the cam phase with the operating angle kept constant to the camshaft and switch the intake valve opening / closing timing to an appropriate timing for each speed range instead of using a plurality of different cams. Variable valve timing controller ("New model vehicle manual (FGY32-
1) ", pages B-44 to B-45, edited and published by Nissan Motor Co., Ltd., published in August 1991, etc.), and does not limit the configuration of the variable valve mechanism 101.

Here, the switching control of the valve opening characteristic (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. In the present embodiment, the functions of the air amount switching control means and the reference air amount setting means are provided in software by the control unit 102 as shown in the flowchart of FIG.

In the flow chart of FIG. 7, first, in step 1 (denoted as S1 in the figure, the same applies hereinafter),
Engine rotation speed Ne detected by the rotation speed sensor 104
Read. Then, in the next step 2, the reference intake air amount Qs (reference air amount) is previously set for each engine rotation speed Ne.
The reference intake air amount Qs corresponding to the current engine speed Ne read in step 1
Ask for.

The reference intake air amount Qs is equal to each rotation speed N.
For each e, the absolute value of the engine intake air amount when the engine intake air amount (torque) is approximately equal is obtained in advance regardless of whether the low speed cam 21 or the high speed cam 22 is used, and this is used as the reference intake air amount. The amount of air is Qs. Here, with the reference intake air amount Qs as a boundary at the same rotation speed Ne, the high-speed cam 22 is provided on the side with a larger air amount on the higher load side.
A higher torque can be obtained by using, and a higher torque can be obtained by using the low speed cam 21 on the side where the air amount on the low load side is smaller.

That is, the switching between the high speed cam 22 and the low speed cam 21 is required to be performed under the condition that substantially the same torque is obtained before and after the cam switching. On the other hand, the engine output torque correlates with the engine intake air amount (cylinder intake air amount), and the absolute value of the intake air amount under the condition that the engine intake air amount is the same for each cam differs depending on the engine rotation speed Ne. .

Therefore, the engine intake air amount (reference intake air amount Qs) which becomes the switching timing is set by the engine rotation speed Ne, and depending on whether the actual air amount Q is larger or smaller than the reference intake air amount Qs. It is made to determine which cam is in the operating range where a higher output torque can be obtained. The switching of the cams is performed when the actual intake air amount Q crosses the reference intake air amount Qa. When the actual intake air amount Q becomes the reference intake air amount Qs, which cam is used. Is a condition for obtaining the same air amount, it is possible to suppress the change in the air amount due to the cam switching and avoid the occurrence of the torque step.

Naturally, the throttle valve opening will differ when the reference intake air amount Qs is obtained for each rotational speed Ne. In the next step 3, the air flow meter 10
Intake air flow rate Qa and engine speed N detected at 5
From e and engine intake air amount Q (cylinder intake air amount)
Ask for.

Then, in step 4, the reference intake air amount Qs is compared with the actual engine intake air amount Q obtained in step 3. Actual engine intake air amount Q
However, when the operating range is larger than the reference intake air amount Qs, a higher torque can be obtained by using the high speed cam 22 in the present embodiment, so that the actual engine intake air amount Q is determined in step 4. When it is determined that the value exceeds the reference intake air amount Qs, the routine proceeds to step 5, where the switching valve 103 is controlled so that the intake valve V is opened and closed by the high speed cam 22.

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. As a result, the rocker arm 1 and the cam follower 2 with which the high-speed cam 22 is in sliding contact are connected and integrated, so that the rocker arm 1 swings around the main rocker shaft 3.

On the other hand, when it is determined in step 4 that the actual engine intake air amount Q is less than or equal to the reference intake air amount Qs, the low speed cam 21 in this embodiment is used in such an operating range. Since a higher torque is obtained, the process proceeds to step 6 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 10 is used to reduce the hydraulic pressure in the hydraulic chamber 34.
3 is controlled to release the engagement between the rocker arm 1 and the free cam follower 2.

As described above, switching between the high-speed cam 22 and the low-speed cam 21 (switching of valve opening characteristics) is performed based on the engine intake air amount Q set according to the engine rotation speed Ne, not the engine rotation speed Ne. ) Is determined, the engine intake air amount Q changes greatly when switching between the high speed cam 22 and the low speed cam 21.
It is possible to avoid the occurrence of a large torque step.

Further, in particular, as in this embodiment, a high speed cam is used.
In the configuration in which the 22 and the low speed cam 21 are selectively used, the cam switching control based on the reference intake air amount Qs can avoid the occurrence of a torque step due to the cam switching, and appropriately selects the cam that can obtain a higher torque. Therefore, the torque performance of the engine can be maximized.

In the above embodiment, the reference intake air amount Qs
However, in the case of such a configuration, the reference intake air amount Qs
When the air amount fluctuates in the vicinity, the cam is frequently switched, which is not preferable. Therefore, in the determination of the switching timing by comparing the reference intake air amount Qs and the actual intake air amount Q, it is preferable to provide a hysteresis to avoid unnecessary repeated cam switching.

[0041]

As described above, according to the engine variable valve switching control device of the invention of claim 1, the reference air amount set according to the engine rotation speed and the actual engine intake air amount are set. Since the valve opening characteristic is switched based on the comparison, it is possible to stably reduce the torque step difference before and after the switching, and it is possible to avoid the occurrence of the driving shock due to the switching of the valve opening characteristic. There is.

Further, in the apparatus according to the invention of claim 2,
In the configuration in which the switching of the valve opening characteristics is performed by selectively using the high speed cam and the low speed cam, it is possible to avoid the occurrence of a torque step when switching between the high speed cam and the low speed cam, and at the same time, the reference There is an effect that an appropriate cam can be used for each operation region divided by the air amount and a high torque can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

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

FIG. 3 is a diagram showing a variable valve mechanism of the embodiment.

FIG. 4 is a view showing a variable valve mechanism of the embodiment (IV- in FIG. 3;
IV cross section).

FIG. 5 is a view showing a variable valve mechanism of the embodiment (V- in FIG.
V sectional view).

FIG. 6 is a view showing a variable valve mechanism of the embodiment (VI- in FIG. 4;
VI cross section).

FIG. 7 is a flowchart showing a valve opening characteristic control of the embodiment.

FIG. 8 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 10 Spring Retainer 21 Low Speed Cam 22 High Speed Cam 31 Actuating Plunger 34 Hydraulic Chamber 101 Variable Valve Mechanism 102 Control Unit 103 Switching Valve 104 Rotation Speed Sensor 105 Air Flow Meter

Claims (2)

[Claims] 1. A valve opening characteristic switching means for switching a valve opening characteristic of an engine to a plurality of preset values, a rotation speed detecting means for detecting a rotation speed of the engine, and an engine detected by the rotation speed detecting means. Reference air amount setting means for setting a reference air amount based on the rotation speed, intake air amount detecting means for detecting an intake air amount of the engine, engine intake air amount detected by the intake air amount detecting means, An air amount switching control unit for controlling a valve opening characteristic switching operation by the valve opening characteristic switching unit based on a comparison with a reference air amount set by the reference air amount setting unit. A variable valve switching control device for an engine. 2. The valve opening 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 air amount switching control means is for intake of an engine. When the air amount is larger than the reference air amount, switching control is performed to the high speed cam, and when the intake air amount of the engine is smaller than the reference air amount, switching control is performed to the low speed cam. The variable valve switching control device for an engine according to claim 1.