JP2919988B2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an engine having a variable valve timing mechanism for changing the phase of an intake valve or an exhaust valve with respect to the phase of a drive system.

[0002]

2. Description of the Related Art A conventional intake system for an engine includes a variable valve timing mechanism for changing the phase of at least one of an intake valve and an exhaust valve with respect to the phase of a drive system (for example, a cam pulley). There is an apparatus in which the valve opening / closing period is controlled by changing the valve opening / closing timing by the variable valve timing mechanism in accordance with the operation state of the engine (for example, Japanese Patent Application Laid-Open No. 62-191636). reference). According to such a device, for example, in a high rotation region where the intake air flow rate is high or a high load region where the intake air amount is large, the combustibility of the engine is increased by increasing the valve opening overlap period, thereby improving fuel efficiency. In a low-rotation, low-load region where the scavenging property is low, by shortening the valve-opening overlap period, it is possible to prevent the intake air from returning due to this overlap.

[0003]

In the above-described apparatus, in order to further enhance the combustibility of the engine, the region where the overlap period is long is set as wide as possible.
It is desirable to limit the region in which the overlap period is shortened as much as possible without causing any inconvenience.

However, when the overlap period control area is set without margin, the variable valve timing mechanism is used when the operation state of the engine shifts from an area where the overlap period is made longer to an area where the overlap period is to be shortened. When the operation delay occurs, the overlap period is kept long during the operation delay even in the region where the overlap period should be shortened, that is, even in the low rotation and low load region where the scavenging property is low. In this period, the intake air blows back and the engine misfires, and in the worst case, it may stop. In particular, when the variable valve timing mechanism operates with lubricating oil or the like circulating in the engine, the pressure of the lubricating oil is substantially proportional to the engine speed. ), The above inconveniences will become more serious.

Therefore, conventionally, the overlap period control area must be set with a margin.
There was a disadvantage that the overlap period enlarged area could not be widened.

In view of such circumstances, the present invention seeks to improve engine flammability as much as possible and to prevent engine misfiring or the like due to backflow of intake air even if the operation of the variable valve timing mechanism is delayed. An object of the present invention is to provide an intake device for an engine that can reliably prevent inconvenience from occurring.

[0007]

SUMMARY OF THE INVENTION The present invention provides a variable valve timing mechanism for changing the phase of at least one of an intake valve and an exhaust valve with respect to the phase of a drive system thereof, and a variable valve timing mechanism in a low-speed low-load region of an engine. The valve-opening overlap period of the intake valve and the exhaust valve is a first period, and the valve-opening overlap period in a region higher in rotation speed or higher load than in the low-rotation low-load region is longer than the first period. And a valve timing control means for controlling the operation of the variable valve timing mechanism in such a manner that the operation period of the variable valve timing mechanism is controlled from the region where the valve opening overlap period is the second period. A pressure increasing means is provided for increasing the intake passage pressure upstream of the intake valve for a set time when shifting to the region defined as the first period (claim 1).

Specifically, a supercharger, a supercharger bypass passage for bypassing the supercharger, and an opening / closing valve provided in the middle of the supercharger bypass passage and opened at least in a low load region And the pressure increasing means determines that the operating state of the engine is in the valve-open overlap period for the second time.
It is preferable that the opening / closing valve be forcibly closed for a set time when a transition is made from the region of the period to the region of the first period (claim 2).

The present invention also provides a variable valve timing mechanism for changing a phase of at least one of an intake valve and an exhaust valve with respect to a phase of a drive system thereof, and an intake valve and an exhaust valve in a low-speed low-load region of an engine. Of the valve-opening overlap period is a first period, and the valve-opening overlap period in the higher rotation or higher load region than the low rotation and low load region is a second period longer than the first period. A valve timing control means for controlling the operation of the variable valve timing mechanism, wherein the operating state of the engine is changed from a region in which the valve-opening overlap period is a second period to a first period. The intake air interposed in the intake passage is set so that the intake air amount becomes larger than the intake air amount in the low-speed low-load region only for a set time when shifting to the region where Those having an intake amount increasing means for increasing the set opening degree of the control valve (claim 3).

Specifically, the engine includes an idle speed control passage that bypasses the throttle valve, and an idle speed control valve that is provided in the middle of the idle speed control passage. A bypass amount increasing means for increasing the opening of the idle speed control valve for a set time when the operating state shifts from a region in which the valve-opening overlap period is the second period to a region in which the valve-opening overlap period is the first period. Those are suitable (claim 4).

On the other hand, various types of the variable valve timing mechanism can be applied. If the variable valve timing mechanism uses a hydraulic pressure that increases with an increase in the engine speed as a driving source, the variable valve timing mechanism can be used. The invention is more effective as described below (claim 5).

[0012]

According to the above arrangement, when the operating state of the engine shifts from the region in which the valve-opening overlap period is the second period to the region in which the valve-opening overlap period is the first period, an operation delay occurs in the variable valve timing mechanism. However, during the set time, the intake passage pressure and the intake air amount upstream of the intake valve are increased by the pressure increasing means and the intake air amount increasing means, so that the blowback of the intake air is suppressed correspondingly and the combustion in the engine is promoted. Therefore, it is possible to prevent the inconvenience such as engine misfire or the like from being caused by the blowback of the intake air due to the switching delay of the overlap period due to the operation delay.

More specifically, in the device according to the second aspect,
When the on-off valve is forcibly closed during the set time, the supercharging effect of the supercharger is increased by that amount, thereby increasing the intake passage pressure.

According to the third aspect of the present invention, the set amount of the intake air amount control valve interposed in the intake passage (in the fourth aspect, the opening of the idle speed control valve) is increased to increase the amount of intake air. And the promotion of combustion is achieved.

[0015] Further, when the variable valve timing mechanism uses a hydraulic pressure which increases with an increase in the engine speed as a drive source, the valve timing variable mechanism particularly in a low rotation region. The present invention works more effectively because the operation delay of the mechanism easily occurs.

[0016]

FIG. 1 shows the overall structure of an engine and its intake device according to an embodiment of the present invention.

The engine body 10 shown here has a plurality of cylinders, a combustion chamber 12 is provided above each cylinder, and an intake valve 14 and an exhaust valve 15 are provided at positions facing the combustion chamber 12. The intake valve 14 and the exhaust valve 15 are driven to open and close by rotation of an intake camshaft 16 and an exhaust camshaft 17, respectively. Further, an injector 18 is disposed at a position upstream of each intake valve 14.

The intake device 20 includes a mechanical supercharger 22, and a supercharger upstream passage 24 is provided upstream of the mechanical supercharger 22, and a supercharger downstream passage 26 is provided downstream thereof. An air flow meter 28 and a throttle valve 30 are provided in the turbocharger upstream passage 24, and an idle speed control (hereinafter, referred to as ISC) passage 32 that bypasses the throttle valve 30 is provided, and the ISC passage 32 is provided. An ISC valve 34 is provided halfway. Passage 2 on the downstream side of the turbocharger
6 has an intercooler 36 on its way,
The intercooler 36 has a branch passage 38 branching for each bank, and each branch passage 38 is connected to the surge tank 4.
Further, it branches further downstream of the cylinder 0 and is connected to the intake port of each cylinder.

Each branch passage 38 and the supercharger upstream passage 2
A supercharger bypass passage 42 for bypassing the supercharger 22 is provided between the supercharger bypass passage 4 and the supercharger bypass passage 4.
An opening / closing valve 44 for opening and closing the passage 42 is provided in the middle of 2. The on-off valve 44 includes a valve element 43 and a diaphragm 45, and a supercharger upstream pressure and a supercharger downstream pressure act on chambers on both sides of the valve element 43,
The valve element 4 of the on-off valve 44 with the diaphragm 45 as a boundary
The pressure on the downstream side of the supercharger is introduced via a chamber 46 into the chamber on the side opposite to the side where 3 is located (upper side in the figure). With this structure, the on-off valve 44 is opened and closed with a pressure balance between the upstream pressure and the downstream pressure of the turbocharger. For example, in a low load region where the pressure downstream of the throttle valve 30 in the turbocharger upstream passage 24 decreases, the on-off valve 44 is opened by the action of the negative pressure (in the figure, the valve body 43 is pulled up). This causes the supercharger 22 to be bypassed in the supercharger bypass passage 42, thereby suppressing a drive loss caused by driving the supercharger 22.

Further, in this device, the normal state where the chamber on the side where the valve element 43 is located (the lower side in the figure) with the diaphragm 45 as a boundary is connected to the downstream side of the throttle valve 30 and the upstream side of the throttle valve 30 There is provided a three-way solenoid valve 48 which is switched to a forced valve closing state communicating with (ie, the atmosphere side). Therefore, when the three-way solenoid valve 48 is switched to the normal state, the on-off valve 44 is opened and closed in the balance between the supercharger upstream pressure and the downstream pressure as described above, whereas the forced closing is performed. When the state is switched, the pressure on the side where the valve element 43 is located increases with the diaphragm 45 as a boundary, and the on-off valve 44 is forcibly closed, whereby the effect of increasing the intake pressure by the supercharger 22 is enhanced. Has become.

On the other hand, the engine body 10 is provided with a variable valve timing mechanism 50 for changing the phase of the intake valve 14 of each cylinder with respect to the phase of its drive system.
The structure is shown in FIG.

An intake-side cam pulley 19 is connected to one end of the intake-side camshaft 16, and the intake-side cam pulley 19 is connected to an engine crankshaft via a timing belt or the like (not shown). . The intake-side cam pulley 19 has a hollow housing 19a, and the end of the intake-side camshaft 16 is inserted into the housing 19a, and a seal member 51 is provided between the two.

A sliding sleeve 52 is provided between the end of the intake camshaft 16 and the housing 19a. Flat splines 53 and 16a to be fitted to each other are formed on the inner peripheral surface of the sliding sleeve 52 and the outer peripheral surface at the end of the intake side camshaft 16, respectively. Is rotated integrally with the intake-side camshaft 16 and is slidable in the axial direction with respect to the shaft 16. Helical splines 54, 5 fitted to each other are provided on the outer peripheral surface of the sliding sleeve 52 and the inner peripheral surface of the housing 19a.
5, the phases of the sliding sleeve 52 and the intake camshaft 16 are changed by the sliding of the sliding sleeve 52.
To change with respect to the phase.

One chamber partitioned by the sliding sleeve 52 in the housing 19a is a hydraulic chamber 56.
And a compression spring 57 is press-fitted into the other chamber,
By the elastic force of the compression spring 57, the sliding sleeve 52 is used.
Is biased toward the hydraulic chamber 56. From this state, the lubricating oil circulating through the engine is appropriately introduced into the hydraulic chamber 56, whereby the sliding sleeve 52 is formed.
Of the intake cam pulley 19
, The phase of the intake camshaft 16 changes, in other words, the opening timing of the intake valve 14 changes.

Further, the intake device is provided with an ECU (valve timing control means and output increasing means) 60 as shown in FIG. The ECU 60 includes an intake pressure sensor 62, an engine speed sensor 64, an oil temperature (temperature of the lubricating oil) sensor 66, and the air flow meter 28.
And the like, control of the introduction of hydraulic oil into the hydraulic chamber 56 in the variable valve timing mechanism 50 (ie, valve timing control), switching control of the three-way solenoid valve 48 (ie, forced closing of the on-off valve 44). Valve control), opening / closing control of the ISC valve 34 (i.e., idle speed control), fuel injection control by the injector 18 and the like.

In this embodiment, when the operating state of the engine is in the low-load low-rotation region, the ECU 60 turns off the variable valve timing mechanism 50, that is, delays the opening timing of the intake valve 14 and sets the exhaust valve 15 To a state in which the valve opening overlap period is set to a relatively short first period, and when the operating state of the engine is in a high load region or a high rotation region, the variable valve timing mechanism 50 is in an on state; That is, control is performed to advance the valve opening timing of the intake valve 14 to switch to a state in which the valve opening overlap period is set to a relatively long second period. Further, when shifting from the region in which the valve opening overlap period is in the second period to the region in which the valve opening overlap period is in the first period, control is performed to close the on-off valve 44 for a predetermined time.

Next, the actual control operation performed by the ECU 60 will be described with reference to the flowcharts of FIGS.

First, in FIG. 3, the ECU 60 reads various detection signals relating to the engine speed Ne, the load factor Pe based on the intake pressure, the oil temperature T, and the like (step S).
1). If the engine speed Ne exceeds a predetermined constant value Neo (NO in step S2), or if the load factor Pe exceeds a constant value Peo (NO in step S3), the valve timing variable mechanism (flow chart) Is turned on VTC.) 50 is turned on (step S4), and the valve-opening overlap period is set to a relatively long second period.
, But otherwise (step S
(2, YES in S3 and NO in step S5), the variable valve timing mechanism 50 is kept in the off state, that is, the state in which the valve opening overlap period is the first period that is relatively short. Then, when shifting to the low-load low-rotation region after the variable valve timing mechanism 50 is once turned on (YES in steps S2, S3, S5), the variable valve timing mechanism 50 is switched from on to off (step S5). At the same time as S6), the process proceeds to the output increasing routine (Step S7) shown in FIG.

In this routine, first, an output increase period is set according to the engine speed Ne and the oil temperature T. That is, in this embodiment, the variable valve timing mechanism 50 is used.
Uses the pressure of the lubricating oil circulating in the engine as a drive source. The introduced oil has a lower pressure as the engine speed Ne decreases, and a viscosity increases as the oil temperature T decreases. Since the operation delay of the variable mechanism 50 is likely to occur, the output increase time is set to be longer as the engine speed Ne and the oil temperature T become higher.

More specifically, an operation of reading the count number N corresponding to the oil temperature T and the engine speed Ne from a map prepared in advance as shown in FIG. 5 is performed (step S).
71). In the illustrated example, the engine speed Ne is 2000 rpm.
When the oil temperature T is 80 ° C., the above count is set to N1, and when the engine speed Ne is 1000 rpm and the oil temperature T is
Is 0 ° C., the count number is set to N2 (> N1).

With the setting of the count number N,
The three-way solenoid valve 48 is turned on (step S7
2) Forcibly close the on-off valve 44. As a result, the supercharging effect of the supercharger 22 is enhanced, and combustion in the engine is promoted by an increase in the intake pressure, and the output thereof is increased.

If the engine speed Ne or the load factor Pe increases during the execution of the output increase control and the variable valve timing mechanism 50 is switched from off to on again (YES in step S73), immediately. The three-way solenoid valve 48 is turned off (step S77), and the output increase control is stopped.

In other cases (NO in step S73), after a unit time (for example, 1 sec) has elapsed from the setting of the count number N (YES in step S74),
Subtract 1 from the current count number N (step S7)
Five). Such subtraction of the count number N is performed every time the unit time elapses (YES in step S74) until the count number N becomes 0 (NO in step S76), and when the count number N becomes 0 ( (YES in step S76), the three-way solenoid valve 48 is turned off (step S77), and the output increase control is completed. That is, in this routine, the opening / closing valve 4 is operated for a time corresponding to the initially set count number N.
4, the forced valve closing operation, that is, the output increasing operation is executed.

According to such an apparatus, even when an operation delay occurs in the variable valve timing mechanism 50 when the valve opening overlap period is switched from the second period to the first period, the opening / closing operation is performed during the operation delay. By forcibly closing the valve 44 to increase the intake pressure, it is possible to prevent the engine from misfiring due to the return of the intake air. Therefore, an area where the overlap period is the first period,
That is, the region where the combustibility is increased by extending the overlap period can be expanded without any inconvenience, so that the engine performance can be improved.

Further, in the apparatus in which the variable valve timing mechanism 50 uses the oil pressure of the engine lubricating oil as the drive source as in this embodiment, the operation delay of the variable valve timing mechanism 50 increases as the engine is in the low load and low rotation range. Therefore, by applying the present invention to this device, the effect becomes more remarkable. Further, the oil temperature T
By setting the output increase period according to the engine speed Ne and the engine speed Ne, the output increase control suitable for the actual operation delay degree can be executed. However, in the present invention, regardless of the specific configuration of the variable valve timing mechanism provided in the engine, even if the drive source is, for example, electricity, the opening and closing timing of at least one of the intake valve and the exhaust valve is shifted. What is necessary is just to change the valve opening overlap period.

In the present invention, the means for suppressing the return of the intake air and promoting the combustion of the engine is not limited to the above-mentioned means for forcibly closing the on-off valve. The ECU 6 serves as a bypass amount increasing means for increasing the opening degree of the ISC valve 34 for a predetermined time after the switching of the 50 from on to off.
0 may be configured. Further, by further configuring the ECU 60 so as to function as an ignition advancing means for advancing the ignition timing in each combustion chamber 12 and a fuel increasing means for increasing the fuel injection amount by the injector 18 for the above-described predetermined time, the ECU 60 is further improved. The effect is obtained.

[0037]

As described above, the present invention is provided with a variable valve timing mechanism, in which the valve-opening overlap period is set to a relatively short first period in the low-speed and low-load region, and to the valve-opening overlap period in other regions. The valve timing control is performed so that the period is set to a relatively long second period, and only the set time is set when the region where the valve opening overlap period is set to the first period from the region where the second period is set. Since the intake passage pressure and intake air amount upstream of the intake valve are increased, even if an operation delay occurs in the variable valve timing mechanism during the switching of the valve-open overlap period, during the operation delay, By suppressing the return of the intake air and promoting the combustion of the engine, it is possible to prevent a misfire or the like of the engine. In other words, the region where the overlap period is the first period, that is, the region where the overlap period is lengthened and the combustibility is increased is enlarged, thereby improving the engine performance and causing the operation delay. There is an effect that inconvenience such as engine misfire can be reliably prevented.

In particular, when the variable valve timing mechanism uses a hydraulic pressure as a drive source that rises with an increase in the engine speed, the operation delay becomes more significant in a low-load low-speed range. Therefore, the effect of the present invention becomes more remarkable by applying to such an apparatus.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine and an intake device thereof according to an embodiment of the present invention.

FIG. 2 is a sectional side view showing a variable valve timing mechanism provided in the engine.

FIG. 3 is a flowchart showing a control operation executed by an ECU provided in the engine.

FIG. 4 is a flowchart showing the contents of an output increasing routine in the above flowchart.

FIG. 5 is a graph showing a relationship between an oil temperature, an engine speed, and a count in a map used in the output increasing routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Engine main body 12 Combustion chamber 14 Intake valve 15 Exhaust valve 16 Intake side camshaft 18 Injector 20 Intake device 22 Supercharger 32 ISC passage (idle speed control passage) 34 ISC valve (idle speed control valve) 42 Supercharger Bypass passage 44 On-off valve 48 Three-way solenoid valve 50 Variable valve timing mechanism 60 ECU (pressure increasing means, intake air amount increasing means)

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI F02D 43/00 301 F02D 43/00 301R (58) Fields investigated (Int.Cl. ⁶ , DB name) F02B 29/08 F02D 41 / 04 305 F02D 43/00 301

Claims (5)

(57) [Claims] 1. A variable valve timing mechanism for changing a phase of at least one of an intake valve and an exhaust valve with respect to a phase of a drive system thereof, and opening the intake valve and the exhaust valve in a low-speed low-load region of the engine. First overlap period
, The valve-opening overlap period in the higher rotation or higher load region than the low rotation and low load region is set to the first period.
And a valve timing control means for controlling the operation of the variable valve timing mechanism so as to have a second period longer than the period. The pressure for increasing the intake passage pressure upstream of the intake valve for a set time when shifting from the region of period 2 to the region of first period
An intake device for an engine, comprising a force increasing unit . 2. An intake system for an engine according to claim 1, wherein a supercharger and a supercharger bypass that bypasses the supercharger.
Pass passage and the turbocharger bypass passage
An open / close valve that is opened at least in a low load region.
In addition, the pressure increasing means is used for controlling the operating state of the engine.
Is a region where the valve-opening overlap period is the second period
From the first period to the region that is the first period
An intake device for an engine, wherein the intake valve is forcible closing means for forcibly closing the on-off valve . 3. An at least one of an intake valve and an exhaust valve.
Valve that changes the phase of the
Variable timing mechanism and low engine speed and low load range
The opening overlap period of the intake and exhaust valves during
Higher rotation or higher negative than the above low rotation and low load range
The valve opening overlap period in the area on the
So that the second period is longer than the second period.
Valve timing system that controls the operation of the variable imaging mechanism
In an intake device for an engine having
The operating state of the valve
When transitioning from the area to be between to the area to be the first period
For a set time, the intake air amount is in the low-speed low-load region.
Interposed in the intake passage so that it is larger than the intake air volume
An intake system for an engine, comprising an intake amount increasing means for increasing a set opening of an intake amount control valve . 4. The idle speed control for bypassing a throttle valve in the intake system for an engine according to claim 3.
A passage and an idle speed control passage.
And an idle speed control valve,
The amount increase means is used when the operating state of the engine
From the region where the lap period is the second period to the first period
Idle speed above for the set time when shifting to the
An intake device for an engine, which is a bypass amount increasing means for increasing an opening degree of a control valve . 5. The engine according to claim 1, wherein
In the intake device, the variable valve timing mechanism
Drives the hydraulic pressure that increases as the engine speed increases
An intake device for an engine, which is a source .