JPH07217460A - Intake and exhaust valve open/close timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide an intake and exhaust valve open/close timing control device for an internal combustion engine, while reducing HC. CONSTITUTION:Detected engine temperature Tw and cooling water temperature Twv for an engine 10 showing the completion of engine warm-up are compared with each other, thereby making judgement as to whether the engine 10 is at a warm-up process. In this case, the value of Tw equal to or larger than Twv means that the warm-up process is complete. Thus, timing for an exhaust valve 17 is selected at a level applicable after the warm-up process. On the other hand, when the value Tw is less than Twv, valve timing with an operation angle smaller than for timing after the warm-up is selected. Then, timing for an intake valve 16 is selected, so as to have a valve overlap amount corresponding to throttle opening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an intake / exhaust valve opening / closing timing control device for an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional intake / exhaust valve opening / closing timing control device for an internal combustion engine, there is, for example, one disclosed in Japanese Patent Laid-Open No. 4-194330. That is, this is an intake / exhaust valve for an internal combustion engine equipped with valve opening / closing timing changing means for opening and closing an intake valve or an exhaust valve at a predetermined timing in synchronization with the rotation of the engine, while varying the valve timing. In the opening / closing timing control device, the opening timing of the exhaust valve is delayed only when the engine is cold compared to when it is warmed up.

In such a conventional intake / exhaust valve opening / closing timing control device, when the engine is cold, the opening timing of the exhaust valve is delayed as compared with after warming up to increase the heating and reaction chamber residence time due to the reaction of the combustion gas. In addition to the decrease in the amount of HC generated due to the increase in exhaust temperature due to the above, the catalyst warm-up promotion effect can effectively reduce HC.

[0004]

However, this valve has the following problems because the closing timing of the exhaust valve is constant. When cold, the concentration characteristics of HC are shown in FIG.
As shown in (2), there are two peaks of high HC concentration (the reason will be described later). Therefore, if the closing timing of the exhaust valve is set in the vicinity of top dead center (TDC) as usual, the second HC concentration becomes high. The HC of the peak portion A is discharged, and the HC reducing effect as a whole may be reduced.

Another problem occurs because the overlap period with the intake valve is constant. That is, when the overlap amount is large, the amount of combustion exhaust gas blown back from the cylinder to the intake valve at a low load is large, and the intake amount is small, so the ratio of the residual exhaust gas re-injected into the cylinder to the intake air increases. As a result, the combustibility deteriorates and the amount of HC generated increases.
On the other hand, when the load is high, the ratio of the residual exhaust gas amount to the intake air amount is small, so the tendency of deterioration of the combustibility is small, and exhaust gas containing a large amount of HC near the end of the exhaust stroke is reburned and removed as a total. HC emissions are reduced.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide an intake / exhaust valve opening / closing timing control device for an internal combustion engine in which HC is reduced when the engine is cold. And

[0007]

In order to achieve the above object, the invention of claim 1 drives the intake valve or the exhaust valve to open and close at a predetermined timing in synchronization with the rotation of the engine, and at the same time, the valve timing. In an intake / exhaust valve opening / closing timing control device for an internal combustion engine, which includes a valve opening / closing timing varying means for varying the engine temperature, an engine temperature detecting means for detecting an engine temperature, and a throttle valve opening detecting means for detecting an opening of a throttle valve. And when the engine detected by the engine temperature detecting means is cold, the intake valve and the exhaust valve opening / closing timing after warming up are set as a reference, and the opening timing of the exhaust valve is delayed and the closing timing is advanced. The valve opening timing is set by increasing and changing the overlap amount with the exhaust valve opening period according to the increase of the throttle valve opening by the throttle valve opening detection means. And intake and exhaust valve opening and closing timing setting means, a structure containing.

Further, the invention of claim 2 further comprises an ignition means for igniting the air-fuel mixture in the combustion chamber, and an ignition by the ignition means in response to an increase in the delay of the opening timing of the exhaust valve when the engine is cold. Ignition timing retard amount control means for increasing and controlling the timing retard amount.

[0009]

According to this structure, in the invention of claim 1, after the engine is warmed up, the intake valve or the exhaust valve is opened / closed at a predetermined timing in synchronization with the rotation of the engine, and a predetermined valve overrun is performed. Although the intake / exhaust valve opening / closing timing is controlled to obtain the overlap amount, when the engine is cold during warm-up, the exhaust valve opening timing is delayed compared to the valve timing after warming up Is accelerated, that is, the exhaust valve opening period is shortened.

By the way, as described above, the distribution of the HC concentration in the exhaust stroke is such that the HC concentration contained in the exhaust becomes high near the beginning of the exhaust stroke and near the piston top dead center position, and during the other exhaust strokes. Indicates that the HC concentration becomes low. This is because near the beginning of the exhaust stroke, it is not sufficiently oxidized, and in the vicinity of the piston top dead center position, the flame is formed in the gap (piston clevis) formed between the piston top land and the cylinder wall. This is because unburned HC is generated and the HC concentration becomes high.

Therefore, as described above, by delaying the opening timing of the exhaust valve, the high concentration of HC generated in the vicinity of the initial stage of the exhaust stroke due to the heating by the reaction of the combustion gas and the increase in the exhaust temperature due to the increase in the combustion chamber residence time. Can be reduced. Further, by advancing the closing timing of the exhaust valve, it is possible to reduce the discharge amount of unburned gas containing high concentration HC near the piston top dead center position.

Further, the intake / exhaust valve opening / closing timing setting means changes the opening timing of the intake valve in accordance with the increase of the throttle valve opening by the throttle valve opening detecting means to increase the overlap amount with the exhaust valve opening period. Change and set. That is, at the time of high load in which the throttle valve opening increases, the intake valve opening timing is controlled so as to increase the valve overlap amount. In this case, if the intake valve opens during the exhaust stroke, part of the combustion gas flows to the intake valve side, and if the valve overlap amount is increased, the amount of combustion gas that flows to the intake valve side also increases. The amount of unburned gas containing HC flowing to the side can be reduced. Then, the combustion gas flowing to the intake valve side returns to the combustion chamber in the next intake stroke as a part of the residual gas and is re-combusted.

At high load, the amount of fresh air also does not increase and the ratio of residual gas to the amount of fresh air does not increase, so combustion does not become unstable, and HC It will not increase. Further, at the time of low load when the throttle valve opening decreases, the intake valve opening timing is controlled to be delayed so as to reduce the valve overlap amount. In this case, when the valve overlap amount is increased, the amount of residual gas increases as described above, and since the amount of fresh air is small at low load, the ratio of residual gas to the amount of fresh air increases and combustion Since HC will increase due to instability, the valve overlap amount is reduced to reduce the proportion of residual gas.

As described above, by controlling the opening / closing timing of the intake / exhaust valve when the engine is cold, the HC reduction effect can be improved as a whole. Further, in the invention of claim 2, further, when the engine is cold, the ignition timing retarding amount control means controls the ignition timing retarding amount by the ignition means to increase in response to an increase in the delay of the exhaust valve opening timing. To do. That is, for example, when the engine is warming up while it is cold,
When the opening timing of the exhaust valve is later than the timing after warming up, the retard amount of the ignition timing is controlled to be increased compared to after warming up.

As a result, the gas temperature in the combustion chamber in the latter stage of combustion rises, post combustion of unburned HC is promoted, and the effect of reducing HC can be improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 showing an embodiment, an engine body 10
A piston 12 slides in a cylinder 11 formed in the above, and an intake port 14 and an exhaust port 15 which communicate with a combustion chamber 13 formed in the cylinder 11 are formed.

The intake port 14 is a passage for guiding the air-fuel mixture supplied from the upstream side thereof into the combustion chamber 13, and the intake port 14 is provided with an intake valve 16 for opening and closing its intake port 14a. Has been. The exhaust port 15 is a passage for discharging the burnt gas burned in the combustion chamber 13 to the outside, and the exhaust port 15 is provided with an exhaust valve 17 for opening and closing the exhaust port 15a. ing.

A spark plug 18 as an ignition means for igniting the air-fuel mixture in the combustion chamber 13 is provided at the upper center of the combustion chamber 13 and operates based on an ignition signal from a distributor (not shown). The ignition timing can be changed based on a signal from the control unit 30. Next, FIGS.
The exhaust valve opening / closing timing control device 40 will be described based on FIG.

That is, in the figure, a first cam 21 having a small operating angle used during warming up and a second cam 22 having a large operating angle used after warming up are attached to the cam shaft 20. . A rocker arm 23 having a mechanism for selecting the first cam 21 and the second cam 22 is arranged below the rocker arm 23. This rocker arm 23 has 2
The exhaust valves 17, 17 of the book can be driven simultaneously, and are composed of a main rocker arm 23a and a sub rocker arm 23b swingable with respect to the main rocker arm 23a. The first follower 24 and the second follower 25 are provided on the sub rocker arm 23b.

During warm-up, the first cam 21 having a small operating angle swings the main rocker arm 23a directly via the first follower 24, and a small operating angle state is set. In this state, the second follower 25, which is in contact with the second cam 22, is put into the idle state by the lost motion mechanism 26 and does not participate in the lift. That is, the lost motion body 26
By positioning the prop 27 at a position avoiding a, the prop 27 hits only the lost motion member 26b slidably inserted in the lost motion body 26a. Inside the lost motion member 26b, a spring is interposed as an elastic member that biases the lost motion body 26a in the direction of the cam shaft 20.

Next, after warming up, when a switching signal is input from the control unit 30 to the control valve 31 as a valve opening / closing timing varying means and hydraulic pressure acts on the hydraulic piston 32 of the rocker arm 23, the piston 32a causes the prop 27 to move. The sub rocker arm 23b is fixed to the main rocker arm 23a by pushing and moving the prop 27 to a position where the prop 27 rides on the upper end surface of the lost motion body 26a. As a result, the large operating angle state is achieved.

When the signal hydraulic pressure is released, the prop spring 27 is pushed back by the return spring 33, and the propeller 27 returns to the small operating angle state by the first cam 21. In addition, the opening / closing timing control 50 of the intake valve is performed, for example, by the method disclosed in Japanese Utility Model Laid-Open No. 2-118147 filed by the applicant of the present application. That is, a hydraulic oil control valve for switching the cam pulley to a plurality of stages for relatively rotating the hydraulic pressure of the cam pulley with respect to the cam shaft for opening and closing the intake valve of the internal combustion engine is provided, and the engine load and the engine for the stepwise operation of the control valve. The desired phase angle difference between the cam shaft and the cam pulley is determined by the sensor output that detects the rotation speed and the target phase angle difference between the cam shaft and the cam pulley that is assigned in advance based on the engine load and engine speed. It's something I got to get.

Thus, the opening timing of the intake valve that is optimal for the operating conditions can be set. For example, the intake valve 16 can be set according to the throttle opening detected by the throttle sensor 34 as the throttle valve opening detecting means. The valve opening timing of can be controlled in multiple stages. Next, the operation of the embodiment will be described based on the flowchart of FIG.

As shown in the flow chart below,
The control unit 30 has a function as a valve opening / closing timing varying means and an intake / exhaust valve opening / closing timing setting means as software. First, step 1 (hereinafter, S1
Say. In (), the cooling water temperature Tw of the engine is detected by the water temperature sensor 19 as the engine temperature detecting means, and is input to the control unit 30.

Next, in S2, the detected engine temperature Tw is compared with the engine cooling water temperature Twv indicating the completion of warm-up to determine whether or not the engine is warming up. And Tw> T
If wv, warm-up has been completed, so the valve timing after warm-up is selected in S3, and if Tw <Twv, the valve timing during warm-up is selected in S4. That is, the valve timings after and during warm-up are shown in FIG.
And the second cam 22 having the timing as shown in FIG.
Alternatively, it is performed by operating the first cam 21. The valve timing during warm-up is exhaust valve 1 more than after warm-up.
The valve opening timing of 7 is delayed and the valve closing timing is advanced. Here, TDC represents the top dead center, BDC represents the bottom dead center, the horizontal axis represents the crank angle, and the vertical axis represents the valve lift amount.

The reason for setting the valve timing during warm-up as shown in FIG. 7 is as follows. That is, as shown in FIG. 11, the distribution of the HC concentration in the exhaust stroke is such that the vicinity of the initial stage of the exhaust stroke and the piston top dead center (TD).
The HC concentration contained in the exhaust gas becomes high near the position C), and the HC concentration becomes low during the other exhaust strokes. Therefore, by delaying the opening timing of the exhaust valve 17, the combustion chamber residence time is increased. The amount of high-concentration HC generated in the vicinity of the initial stage of the exhaust stroke can be reduced by promoting post-combustion based on the increase, and by advancing the closing timing of the exhaust valve 17, the vicinity of the piston top dead center position (in the figure) This is because the amount of unburned gas containing a high concentration of HC in the portion A) is reduced, and HC can be reduced.

Next, at S5, the valve timing of the intake valve 16 is changed so that the valve overlap amount θov corresponding to the throttle valve opening detected by the throttle valve opening sensor is obtained. That is, for example, as shown in FIGS. 7 and 8, at the time of high load when the throttle valve opening increases, the opening timing of the intake valve 16 is advanced so that the valve overlap amount θov is increased, while the throttle valve is opened. At the time of low load when the opening degree decreases, control is performed such that the opening timing of the intake valve 16 is delayed so as to reduce the valve overlap amount θov.

That is, at high load, when the intake valve 16 is opened during the exhaust stroke, a part of the combustion gas flows to the intake valve 16 side, and flows to the intake valve 16 side by increasing the valve overlap amount θov. The amount of combustion gas is positively increased, and as a result, HC flowing toward the exhaust valve 17 side
Emissions of unburned gas, including, are reduced. Then, the combustion gas flowing to the intake valve 16 side returns to the inside of the combustion chamber 13 in the next intake stroke as a part of the residual gas and is re-combusted.

At a high load, the ratio of residual gas to fresh air does not increase even if the valve overlap amount θov is increased by increasing the amount of fresh air, so that HC due to combustion instability increases. However, since the intake negative pressure is large at the time of low load, a large amount of combustion gas in the combustion chamber is returned to the intake valve 16 side even if the amount of overlap is small, and the amount of fresh air is reduced. When the valve overlap amount θov is increased, the ratio of the residual gas to the fresh air is increased, and HC is deteriorated due to unstable combustion. Therefore, the valve overlap amount θov is decreased.

In the above, S2 to S5 function as the intake / exhaust valve opening / closing timing setting means. In this way, the unburned gas containing HC is not discharged to the exhaust side, but is re-combusted in the next combustion stroke, so that the total HC
The reduction effect can be improved. Next, the operation of the other embodiment will be described based on the flowchart of FIG.

That is, the flow of S1 to S5 is basically the same as that shown in FIG. 5, but the ignition timing of the spark plug 18 is retarded according to the opening timing of the exhaust valve 17. The difference is in controlling the amount. Therefore,
Only the different steps will be described. That is, after selecting the valve timing during warm-up and changing the valve timing of the intake valve 16 so that the valve overlap amount according to the throttle opening degree is obtained, in S6, according to the opening timing of the exhaust valve 17. The retard amount of the ignition timing by the ignition means is controlled. That is, for example, as shown in FIG. 10, when the opening timing of the exhaust valve 17 lags behind the timing after warm-up during cold engine warm-up, the ignition timing retard amount is warmed up. Control to increase more than after.

As a result, the gas temperature in the combustion chamber in the latter stage of combustion rises, post combustion of unburned HC is promoted, and the effect of reducing HC can be improved.

[0033]

As described above, according to the first aspect of the present invention, when the engine detected by the engine temperature detecting means is cold, the exhaust valve opening / closing timing after warming up is used as a reference. The valve opening timing is set to be delayed and the valve closing timing is set to be advanced, and the valve opening timing of the intake valve is changed by changing the overlap amount with the exhaust valve opening period according to the throttle valve opening by the throttle valve opening detection means. Since the intake / exhaust valve opening / closing timing setting means is set, the staying time of the unburned gas containing HC in the combustion chamber is increased to promote the afterburning of the HC, and further from the piston clevis to the latter half of the exhaust stroke. HC can be reduced by re-combusting the discharged high-concentration HC in the next combustion process without discharging it to the exhaust side.

Further, according to the second aspect of the present invention, the ignition timing retarding means for increasing the retardation amount of the ignition timing by the ignition means in accordance with the increase of the delay of the opening timing of the exhaust valve when the engine is cold. Since the amount control means is provided, the gas temperature in the combustion chamber in the latter stage of combustion rises, and the afterburning of unburned HC is promoted.
The effect of reducing HC can be improved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an intake / exhaust valve opening / closing timing control device for an internal combustion engine according to the present invention.

FIG. 2 is a system diagram showing an exhaust valve opening / closing timing control device portion of FIG.

FIG. 3 is a plan view showing a rocker arm portion of FIG.

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a flowchart showing the operation of one embodiment of the present invention.

FIG. 6 is a diagram showing valve timing after warm-up.

FIG. 7 is a diagram showing valve timing during warm-up.

FIG. 8 is a diagram showing a relationship between a throttle opening and a valve overlap amount.

FIG. 9 is a flowchart showing the operation of another embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between an opening timing of an exhaust valve and a retard amount of an ignition timing.

FIG. 11 is a diagram showing the relationship with the HC concentration in the exhaust during the exhaust stroke.

[Explanation of symbols]

 11 Cylinder 12 Piston 13 Combustion Chamber 14 Intake Port 14a Intake Port 15 Exhaust Port 15a Exhaust Port 16 Intake Valve 17 Exhaust Valve 18 Spark Plug 19 Water Temperature Sensor 20 Cam Shaft 21 First Cam 22 Second Cam 23 Rocker Arm 23a Main Rocker Arm 23b Sub rocker arm 24 1st follower 25 2nd follower 26 Lost motion mechanism 26a Lost motion body 27 Blob 30 Control unit 31 Control valve 32 Hydraulic piston 32a Piston 33 Return spring 34 Throttle sensor 40 Exhaust valve opening / closing timing control device 50 Intake valve opening / closing timing Control device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F01N 3/24 ZAB R F02D 43/00 301 BK Z F02P 5/15

Claims (2)

[Claims] 1. An intake valve or an exhaust valve is opened and closed at a predetermined timing in synchronization with the rotation of an engine.
In an intake / exhaust valve opening / closing timing control device for an internal combustion engine, comprising: a valve opening / closing timing varying means for varying the valve timing, an engine temperature detecting means for detecting an engine temperature, and a throttle valve opening for detecting an opening degree of a throttle valve. Temperature detection means, and when the engine detected by the engine temperature detection means is cold, the opening and closing timing of the exhaust valve is set to be delayed and the closing timing is set to be advanced based on the intake and exhaust valve opening and closing timing after warming up. Along with the intake / exhaust valve opening / closing timing setting means, the opening timing of the intake valve is set by increasing and changing the overlap amount with the exhaust valve opening period according to the increase of the throttle valve opening by the throttle valve opening detecting means. An intake / exhaust valve opening / closing timing control device for an internal combustion engine, comprising: 2. An ignition means for igniting an air-fuel mixture in a combustion chamber, and an ignition timing retarding amount by the ignition means is controlled to increase in response to an increase in a delay of an exhaust valve opening timing when the engine is cold. 2. An intake / exhaust valve opening / closing timing control device for an internal combustion engine according to claim 1, further comprising: ignition timing retard amount control means.