JPH06117280A - Air intake negative pressure control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To use a negative pressure device while securing low fuel consumption even in a so-called non-throttle engine. CONSTITUTION:When an engine is in an EGR area (FEGR=1) or a purge area (FPUG=1), a valve opening value theta THTRG of a throttle valve is calculated (S3-S5), and valve opening theta TH of the throttle valve is set in a theta THTRG value, and suction air quantity control (S6) is carried out by an air intake valve. When internal pressure PC of a vacuum tank is not more than a prescribed value PCLL, throttling operation is carried out, and the vacuum tank is put always in a negative pressure condition (S9).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake negative pressure control system for an internal combustion engine, and more particularly to an intake negative pressure control for an internal combustion engine which controls the intake air amount by the valve opening of a throttle valve and the opening period of the intake valve. Regarding the device.

[0002]

2. Description of the Related Art Valve timing of an intake valve provided in a cylinder head of an engine (valve opening timing and valve lift amount)
The so-called non-throttling engine that controls the intake air amount by making the intake air variable is different from the throttle ring engine that controls the intake air amount by controlling the opening / closing of the throttle valve provided in the intake passage, so Since pressure is not generated and so-called pumping loss is less likely to occur, there is an advantage that fuel efficiency can be improved.

On the other hand, in the above non-throttling engine, since the intake negative pressure is not generated as described above, the negative pressure devices such as the exhaust gas recirculation device (EGR device) and the evaporated fuel processing device cannot be used, There is a drawback that it is inconvenient to suppress the emission of harmful components such as NOx and evaporated fuel generated in the fuel tank to the atmosphere.

Further, in the above non-throttling engine, since the intake negative pressure is not generated even in the low load region, the promotion of atomization of the liquid fuel is hindered, the amount of fuel adhering to the intake pipe is increased, and the combustion performance is deteriorated. There was also the drawback of doing so.

Therefore, as a means for solving such a drawback, in a non-throttle engine, the intake air amount is controlled by the opening period of the throttle valve and the intake valve.
There has been proposed a device that improves combustion and control accuracy at low load (for example, Japanese Patent Publication No. 59-22055).

[0006]

However, in the above-mentioned prior art, since the throttle valve is interlocked with the accelerator pedal, the intake negative pressure fluctuates depending on the accelerator opening, so that the negative pressure required for the negative pressure device is increased. However, it is difficult to always ensure that the control of the negative pressure device becomes complicated.

Further, when it is desired to use a braking booster as a negative pressure device, it is conceivable to provide a separate air pump for producing a predetermined negative pressure. However, deterioration of fuel efficiency and cost due to drive loss of the air pump are considered. There is a problem in that it is difficult to bring up the layout or secure a space on the layout.

Further, when it is desired to use the EGR device, the EGR valve can be lifted by a slight negative pressure so that the EGR valve can be lifted.
The diaphragm diameter of the GR valve may be increased, or the EGR valve may be enlarged in order to secure the recirculation amount, but problems such as deterioration of the recirculation amount control and an increase in the weight of the entire device occur.

The present invention has been made in view of the above problems, and provides an intake negative pressure control device for an internal combustion engine which can utilize a negative pressure device while ensuring low fuel consumption even in a non-throttle engine. The purpose is to

[0010]

In order to achieve the above object, the present invention provides an intake valve whose valve opening period can be arbitrarily changed, an electrically operated throttle valve, and a driving force for driving a negative pressure in the intake pipe. In an intake air negative pressure control device for an internal combustion engine having a control device as a power source, pressure accumulating means for accumulating negative pressure in the intake pipe, pressure detecting means for detecting pressure of the pressure accumulating means, and operating condition of the engine are detected. The operating range detecting means and the operating range determining means for determining whether or not the operating range is in which the intake air amount is controlled only by the intake valve based on the detection result of the operating state detecting means. Even when it is determined by the determining means that the intake air amount is controlled only by the intake valve, if the pressure detected by the pressure detecting means is below a predetermined value, the intake valve and the throttle The torque valve is characterized by having an intake negative pressure generating means for generating a negative pressure in the intake pipe. Further, the control device is specifically a vehicle braking booster.

Further, the present invention has an intake valve whose valve opening period can be arbitrarily changed, an electrically operated throttle valve, and a control device for controlling the control gas introduced by the negative pressure in the intake pipe. In an intake negative pressure control device for an internal combustion engine, an operating state detecting means for detecting an operating state of the engine, and the operating state detecting means for detecting whether or not the operating range is in which an intake air amount is controlled only by the intake valve. At least in the control device even when it is determined that the operating region determining unit determines the intake air amount by only the intake valve. It is characterized by having an intake negative pressure setting means for setting a predetermined negative pressure in the intake pipe by the intake valve and the throttle valve when in a specific operating state where the control gas should be introduced. It is set to.

Further, specifically, the control device includes a fuel tank, a canister that adsorbs and stores evaporated fuel generated from the fuel tank, and a purge passage that connects the canister and an intake system of an internal combustion engine, It is characterized in that it is an evaporative fuel treatment device provided with a purge control valve interposed in the purge passage, and / or an exhaust gas recirculation device for recirculating a part of exhaust gas to an intake pipe.

[0013]

According to the above construction, when the pressure of the pressure accumulating means is below the predetermined value, the intake negative pressure is generated by the intake valve and the throttle valve. As a result, the vehicle braking booster that uses the negative pressure in the intake pipe as the driving force source can always be operated.

Further, according to the above configuration, in the specific operating state where the control gas is to be introduced into the control device, the intake valve and the throttle valve set the inside of the intake pipe to a predetermined negative pressure. As a result, the evaporated fuel processing device which is the control device or /
Also, the exhaust gas recirculation device can introduce the control gas.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of an intake negative pressure control system for an internal combustion engine according to the present invention. In FIG. 1, a throttle valve 2 is arranged in a collecting portion 1a of an intake pipe 1, and an actuator 3 composed of, for example, a stepping motor is connected to the throttle valve 2. The actuator 3 is an electronic control unit (hereinafter referred to as “EC
U ”) 4 and drives the throttle valve 2 in response to a control signal from the ECU 4. A throttle valve opening (θTH) sensor 5 is mechanically connected to the throttle valve 2 and a detection signal thereof is supplied to the ECU 4.

An air cleaner 6 is provided at the upstream end of the collecting portion 1a of the intake pipe 1. A bypass pipe 7 that bypasses the throttle valve 2 is connected between the collecting portion 1a of the intake pipe 1 and the branch pipe 1b on the downstream side thereof, and a bypass valve 8 including a linear solenoid or the like is provided in the middle of the bypass pipe 7. Is provided. The bypass valve 8 is opened / closed by a signal from the ECU 4.

An intake air temperature (T
A) A sensor 9 and an intake pipe absolute pressure (PBA) sensor 10 are mounted, and their detection signals are supplied to the ECU 4.

The fuel injection valve 11 is provided for each cylinder in the branch pipe 1b of the intake pipe 1 on the upstream side of the engine 12. Further, each fuel injection valve 11 is connected to a fuel pump 14 via a fuel supply pipe 13 and electrically connected to the ECU 4, and a valve opening time of fuel injection is controlled by a signal from the ECU 4.

An intake valve 16 is attached to an intake port 15 of the engine 12, and a valve timing (a valve opening timing and a valve lift amount) is controlled by a control signal from the ECU 4 via a hydraulically driven valve unit described later. On the other hand, engine 1
An exhaust valve 18 is attached to the exhaust port 17 of No. 2, and the valve timing is controlled via a hydraulically driven valve unit by a control signal from the ECU 4 as well.

An engine cooling water temperature (TW) sensor 19 is attached to the cylinder peripheral wall of the engine 12, and its detection signal is E.
It is supplied to CU4. An engine speed (NE) sensor 20 is arranged so as to face the crankshaft of the engine, generates a pulse signal (TDC signal) for each predetermined crank angle of each cylinder, and supplies the pulse signal (TDC signal) to the ECU 4.

The cylinder head 12a of the engine 12 is provided with a hydraulic pressure (TOIL) sensor 21.
The IL sensor 21 detects the temperature of hydraulic oil of a hydraulic drive unit, which will be described later, and supplies the detection signal to the ECU 4.

Further, the cylinder head 12 of the engine 12
intake pipe collecting portion 1a on the upper side of a and on the upstream side of the throttle valve 2.
Are communicated with each other through a fresh air introduction pipe 22, and the upper portion of the cylinder head 12a and the branch pipe 1b are communicated with each other through a blowby gas reduction pipe 23. As a result, the throttle valve 2 is slightly closed to make the branch pipe 1b a weak negative pressure to introduce fresh air into the engine 12, and blowby gas leaking from the combustion chamber to the crankcase through the cylinder peripheral wall is blowby gas. Reduction tube 23
Also, the blow-by gas can be returned to the combustion chamber again through the branch pipe 1b, and the blow-by gas can be re-combusted.

A pipe 24 is branched from the branch pipe 1b, and a vacuum tank 26 is provided at the tip of the pipe 24 via a check valve 25. The vacuum tank 26 is provided with a tank internal pressure (VP) sensor 27, and the pressure in the vacuum tank 26 detected by the VP sensor 27 is converted into an electric signal and E
It is supplied to CU4.

Therefore, an exhaust gas recirculation path 28 is provided between the branch pipe 1b and the exhaust pipe 101 in a bypass shape.

Further, an exhaust gas recirculation amount control valve (hereinafter referred to as an EGR valve) 29 is interposed in the exhaust gas recirculation passage 28. The EGR valve 29 includes a valve chamber 30 and a diaphragm chamber 3
A casing 32, a wedge-shaped valve element 33 located in the valve chamber 30 and vertically movable so that the exhaust gas recirculation path 28 can be opened and closed, and a valve. Axis 3
Diaphragm 35 connected to the valve element 33 via 4
And a spring 36 for urging the diaphragm 35 in the valve closing direction.
It consists of and. Further, the diaphragm chamber 31 is
The atmospheric pressure chamber 3 defined on the lower side via the diaphragm 35
7 and a negative pressure chamber 38 defined on the upper side.

Further, the atmospheric pressure chamber 37 is communicated with the atmosphere through the ventilation hole 37a, while the negative pressure chamber 38 is connected to the negative pressure communication passage 39.
It is connected to the. That is, the negative pressure communication passage 39 has its tip connected to the vacuum tank 26, and the negative pressure in the vacuum tank 26 is introduced into the negative pressure chamber 38 via the negative pressure communication passage 39. A pressure adjusting valve 40 is provided in the middle of the negative pressure communication passage 39. The pressure adjusting valve 40 is a normally closed solenoid valve, and atmospheric pressure or negative pressure is selectively supplied into the negative pressure chamber 38 of the diaphragm chamber 31 via the pressure adjusting valve 40, so that the negative pressure chamber 38 Generates a predetermined control pressure. That is, when the pressure adjusting valve 40 operates, the solenoid valve opens and negative pressure is introduced into the negative pressure chamber 38, and when the pressure adjusting valve is in the inoperative state, the solenoid valve closes,
Atmospheric pressure is introduced into the negative pressure chamber 38 through the air introduction port 41.

Further, the EGR valve 29 is provided with a valve opening (lift) sensor (hereinafter referred to as “L sensor”) 42, and the L sensor 42 is in the operating position of the valve body 33 of the EGR valve 29. (Valve lift amount) is detected and the detection signal is supplied to the ECU 4.

Further, a purge pipe 43 is provided so as to branch from the branch pipe 1b, and the purge pipe 43 is provided in the evaporated fuel processing device 4
4 is connected.

Thus, the fuel vapor processing apparatus 44 has a fuel tank 46 having a filler cap 45 that is opened at the time of refueling the fuel, and an activated carbon 47 as an adsorbent, which is built-in to collect the fuel vapor from the fuel tank 46. A canister 48 for adsorbing and storing, an evaporated fuel flow passage 49 connecting the canister 48 and the fuel tank 46, and an evaporated fuel flow passage 4
The two-way valve 50 including a positive pressure valve and a negative pressure valve interposed in the valve 9 is provided.

Further, in the vaporized fuel processing device 44, a hot-wire flow meter (hereinafter, simply referred to as "flow meter") 51 is provided in the middle of the purge pipe 43 near the canister 48, and further downstream of the flow meter 51. A purge control valve 52 and an electromagnetic opening / closing valve 53 are provided in the middle of the purge pipe 43.

The flowmeter 51 utilizes the fact that when a platinum wire heated by passing an electric current is exposed to an air stream, its temperature lowers and its electric resistance decreases. Changes according to the concentration, flow rate, etc., and supplies an output signal corresponding to these changes to the ECU 4.

Further, the purge control valve 52 is divided into a first chamber 55 and a second chamber 56 by a diaphragm 54, and a spring 57 for pressing the diaphragm 54 is contracted in the first chamber 55. There is. Then, the purge control valve 5
2 is that when the electromagnetic opening / closing valve 53 is opened, the diaphragm 54 moves upward in the figure against the elastic urging force of the spring 57, and the evaporated fuel stored in the canister 48 branches via the purge pipe 43. Purged to 1b.

A braking booster 58 having a master bag is connected to the vacuum tank 26. Negative pressure in the vacuum tank 26 is supplied to the braking booster 58, and a strong braking force is obtained by a small pedaling force of the brake pedal.

Further, the ECU 4 has an accelerator opening degree (θACC) sensor 59 for detecting the amount of depression of the accelerator pedal as a parameter representing the driver's request to the engine.
And an atmospheric pressure (PA) sensor 100 for detecting the atmospheric pressure are electrically connected.
The detection signal of the A sensor 100 is supplied to the ECU 4.

Therefore, the ECU 4 shapes the input signal waveforms from the various sensors described above, corrects the voltage level to a predetermined level, and converts the analog signal value into a digital signal value. Central processing circuit (hereinafter referred to as "CPU"), storage means including ROM and RAM for storing various calculation programs executed by the CPU and various maps and calculation results described later, the fuel injection valve 11, fuel The pump 14, the pressure control valve 40, the electromagnetic opening / closing valve 53, and an output circuit for supplying a drive signal to a hydraulic drive unit described later are provided.

FIG. 2 is a sectional view showing the details of the intake side valve operating mechanism. An intake valve 16 is provided in an intake port 15 of the engine 12. The intake valve 16 is arranged so as to be guided in the cylinder head 12a so as to open and close the intake valve opening 61 in the vertical direction in the drawing. Collar 6 of intake valve 16
A valve spring 63 is contracted between the cylinder 2 and the cylinder head 12a, and the valve spring 63 elastically urges the intake valve 16 upward (in the valve closing direction) in the drawing.

On the other hand, on the left side of the intake valve 16 in the figure, the cam 6
A cam shaft 65 having 4 is rotatably arranged. The cam shaft 65 is connected to a crank shaft (not shown) via a timing belt (not shown). And
A hydraulic drive valve unit 60 is interposed between a cam 64 integrally formed with the cam shaft 65 and the intake valve 16.

The hydraulic drive valve unit 60 presses the intake valve 16 downward against the elastic urging force of the valve spring 63 according to the profile of the cam 64 to open / close the hydraulic drive mechanism 60A.
And a hydraulic pressure release mechanism 60B for canceling the pressing force of the hydraulic drive mechanism 60A during the valve opening operation and closing the intake valve 16 regardless of the cam profile.

The hydraulic drive mechanism 60A is used for the cylinder head 1.
First fixed to a block 66 formed integrally with 2a
Of the cylinder body 67 and a lower end (front end) of the cylinder body 67 abutting against the upper end (rear end) of the intake valve 16 and slidably fitted in the cylinder hole 67a of the first cylinder body 67 (valve drive piston). ) 68, an operating hydraulic chamber 69 defined by the first cylinder body 67 and the valve side piston 68, and the block 6
6, a second cylinder body 70 fixedly mounted on the second cylinder body 6, a lifter 71 slidably contacting the cam 64, and a lower end of the lifter 71 abutted to be slidably fitted to a lower portion of the second cylinder body 70. Main components are a cam side piston 72, a hydraulic pressure generation chamber 73 defined by the second cylinder body 70 and the cam side piston 72, and an oil passage 74 that connects the hydraulic pressure generation chamber 73 and the working hydraulic pressure chamber 69. Then, when the hydraulic pressure in the hydraulic pressure chamber 69 is equal to or higher than a predetermined value, the intake valve 1 follows the profile of the cam 74.
Open and close 6

The block 66 includes a collar portion 62 of the intake valve 16.
A valve lift sensor 75 is arranged at a position facing to. The valve lift sensor 75 is electrically connected to the ECU 4, detects the valve lift amount of the intake valve 16, and supplies the detection signal to the ECU 4.

On the other hand, the hydraulic pressure release mechanism 60B is provided with the oil passage 7
4, an oil passage 77 connecting the oil supply gallery 76, a spill valve 78 interposed in the oil passage 77, a feed valve 79 and a check valve 80 arranged in the oil passage 77, The main components are an accumulator 82 for holding the released hydraulic pressure in the accumulator circuit 81a defined by the valves 79 and 80 and the spill valve 78. The solenoid 78a of the spill valve 78 is connected to the ECU 4 and is excited or demagnetized by its control signal. The oil supply gallery 76 is provided to supply hydraulic pressure to the hydraulically driven valve unit provided for each cylinder, and is connected to the oil pump 83. The oil pump 83 supplies the hydraulic oil in the auxiliary oil pan 84 provided in the cylinder head 12a to the oil supply gallery 76 as the hydraulic pressure within a predetermined range. The hydraulic oil supplied to the oil supply gallery 76 may be supplied by an oil pump from an oil pan provided under a crankcase (not shown).

The accumulator 82 is the hydraulic pressure release mechanism 60.
A cylinder hole 85 provided in the middle of the accumulator circuit 81 for accumulating the hydraulic pressure and the discharged oil released by the spill valve 78 of B, and a cap 87 having an air hole 86, a cylinder hole 85 formed in the block 66, and a cylinder hole 85. 88 slidably fitted to the cap, the cap 87 and the piston 88
And a spring 89 compressed between the two.

The hydraulic drive mechanism 60 configured as described above
The operation of A and the hydraulic pressure release mechanism 60B will be described below.

When the solenoid 78a of the spill valve 78 is excited by the control signal from the ECU 4, the spill valve 78 is closed and the hydraulic pressure generating chamber 73, the hydraulic passage 74 and the working hydraulic chamber 69 of the hydraulic drive mechanism 60A are closed. Is maintained at a high pressure equal to or higher than a predetermined value, and the intake valve 16 is opened / closed according to the profile of the cam 64. Therefore, the valve operating characteristics in this case (relationship between crank angle and valve lift)
Becomes as shown by the solid line in FIG.

On the other hand, when the solenoid 78a of the spill valve 78 is demagnetized by the control signal from the ECU 4 when the intake valve 16 is opened, the spill valve 78 is opened and the hydraulic pressure generating chamber 73 of the hydraulic drive mechanism 60A and the oil are generated. The hydraulic pressure in the passage 74 and the hydraulic pressure chamber 69 decreases, and the intake valve 16 starts the valve closing operation regardless of the profile of the cam 64. At this time, the closing speed of the intake valve 16 is relaxed during the valve closing operation by the hydraulic oil return amount limiting mechanism provided on the valve side piston 68, and the intake valve 16 is gently seated on the valve seat 90. The valve operating characteristic in this case is as shown by the broken line in FIG. That is,
In the figure, when the solenoid 78a is demagnetized at the crank angle θOFF, the intake valve 16 starts the valve closing operation with a slight delay (θ = θST) from θOFF, and the valve closing state is completed at θ = θIC.

As described above, the spill valve 78 is opened / closed by the control signal from the ECU 4, and the action of the hydraulic drive mechanism 60A is invalidated when the valve is opened.
It is possible to arbitrarily set the valve closing start timing (valve closing timing) of the intake valve 16, and thus the valve opening period. As a result, the intake air amount of each cylinder can be controlled by the control signal of the ECU 4.

In the present embodiment, the hydraulic valve unit (not shown) similar to the intake valve side is provided on the exhaust valve side, but the exhaust valve side is normally closed at a constant timing according to the cam profile. Alternatively, a variable valve timing mechanism capable of setting a plurality of valve opening / closing timings may be used.

Next, the control procedure of the intake negative pressure control executed in this embodiment will be described.

FIG. 4 is a flow chart of the intake negative pressure control routine, and this program is executed, for example, in synchronization with the generation of the TDC signal pulse.

First, in step S1, the flag FNONT is set.
It is determined whether H is "1" and whether the engine is in the non-throttling operation region. Here, whether or not it is in the non-throttling operation area is determined by a non-throttling operation area determination routine (not shown). Specifically, when the engine is in the starting mode (for example, during cranking) and the oil temperature TOIL detected by the TOIL sensor 21 is equal to or lower than a predetermined temperature (for example, 20 ° C.),
Alternatively, the engine is determined to be in the throttling operation range when the accelerator opening degree θACC detected by the θACC sensor 59 is in a high load operation range of a predetermined angle (for example, 50 °) or more.

When the flag FNONTH is "0", that is, when the engine is in the throttling operation range, the routine proceeds to step S10, where a predetermined throttling operation is performed and the intake air amount is controlled by the valve opening θTH of the throttle valve 2. I do.

On the other hand, in step S1, the flag FNONTH is set.
Is "1", that is, when it is determined that the engine is in the non-throttling operation region, the process proceeds to step S2, and the flag FE
It is determined whether the GR or the flag FPUG is "1". That is, in step S1, it is determined whether the engine 12 is in the operating region (EGR region) of the EGR valve 29, or whether the electromagnetic opening / closing valve 53 is opened and the evaporated fuel is to be purged in the intake pipe 1 (purge region). It is determined whether or not there is.

Specifically, as shown in FIGS. 5A and 5B, the engine speed NE (r
pm), accelerator opening θACC (°), and engine cooling water temperature TW. Specifically, the engine speed is within a predetermined speed (for example, 900 rpm <NE <380).
0 rpm), the accelerator opening is within a predetermined angle (for example, 10 ° <θACC <50 °), and the engine cooling water temperature TW is at or above a predetermined temperature (for example, 60 ° C), it is determined that the engine is in the EGR region. It That is, when the engine is in the idling region, the high load operation region, the high rotation speed region and the deceleration region, and when the engine cooling water temperature is low and the warm-up has not been completed yet, the EGR valve 29 is closed to prevent exhaust gas recirculation. Not performed. Whether it is in the purge region or not is estimated by, for example, estimating the vaporized fuel stored in the canister 48 based on the purge flow rate detected by the flow meter 51, and purging when the detected value of the flow meter 51 is equal to or greater than a predetermined value. It is judged to be in the area.

Then, the flag FEGR or the flag FPU
When it is determined that G is "1", the process proceeds to step S3, where θ
The THTRGM map is searched to calculate the basic opening value θTHTRGM of the throttle valve 2.

The θTHTRGM map is specifically shown in FIG.
As shown in, the accelerator opening degrees θACC00 to θACC1
5 and engine speeds NE00-NE15 are mapped in a matrix form θTHTRGM (00,00)-
θTHTRGM (15,15) is given. This θTHTRGM map is given map values according to the accelerator opening θACC and the engine speed NE so that the intake negative pressure in the branch pipe 1b becomes a predetermined negative pressure, for example, about −60 mmHg. The basic opening value θTHTRGM of the throttle valve 2 is read out by searching this θTHTRGM map or calculated by an interpolation method. The predetermined negative pressure may be set according to the exhaust gas recirculation amount and the purge supply amount.

Next, at step S4, the valve opening correction coefficient K
The TH and the feedback correction coefficient KFBTH are calculated. The valve opening correction coefficient KTH is determined by the atmospheric pressure PA and the intake air temperature TA.
The feedback correction coefficient KFBTH is set to a predetermined value according to the intake pipe absolute pressure PBA.

Next, at step S5, the valve opening degree θTH of the throttle valve 2 which should be a constant negative pressure based on the mathematical expression (1).
Calculate TRG.

ΘTHTRG = θTHTRGM × KTH × KFBTH (1) Next, in step S6, the valve opening degree θTH of the throttle valve 2
Is set to the valve opening degree θTHTRG calculated by the mathematical expression (1), and the intake air amount is controlled by the valve timing of the intake valve 16.

Thus, the exhaust gas can be returned to the intake pipe 1 and the evaporated fuel can be purged into the intake pipe 1 without any trouble, and these negative pressure devices can be utilized.

On the other hand, when both the flag FEGR and the flag FPUG are "0" in step S2, that is, when it is determined that the engine is not in the EGR region or the purge region, the process proceeds to step S7 to execute a predetermined non-throttling operation. .

At this time, the throttle valve may be closed by a predetermined angle to set the inside of the branch pipe to a weak negative pressure (for example, about -40 mmHg) to perform non-throttling operation.
It is possible to prevent the occurrence of pulsation of the air flow in the branch pipe 1b when the intake valve 16 is substantially fully closed to avoid the occurrence of intake noise, and set the inside of the branch pipe 1b to the above-mentioned weak negative pressure. This is also convenient for the reduction of blow-by gas.

Next, in step S8, the tank internal pressure PC in the vacuum tank 26 is the predetermined tank internal pressure PCLL.
Determine if it is less than. And PC <PCLL
When the above condition is established, it is determined that the pressure in the vacuum tank 26 is low, and a throttling operation is performed to control the intake air amount by controlling the valve opening degree of the throttle valve 2 so as to supply a negative pressure to the vacuum tank 26. This program ends.

As a result, a negative pressure is always accumulated in the vacuum tank 26, and the braking booster 58 can be always driven by the negative pressure.

FIG. 7 is a diagram showing the fuel consumption improvement rate with respect to the intake negative pressure of this embodiment together with a comparative example. Point a is the present embodiment, that is, the negative pressure in the intake pipe 1 is controlled to a constant value. When the intake air amount control by valve timing is performed, point b
Represents a normal non-throttling operation, point c represents a throttling operation, and point d represents a case where a negative pressure is forcibly supplied to the negative pressure device by using an air pump.

As is apparent from FIG. 7, fuel consumption is poor during throttling operation because pumping loss occurs, and when an air pump is used, fuel consumption is considerably lower than that during non-throttling operation due to drive loss of the air pump. On the other hand, in the present embodiment, the negative pressure in the intake pipe 1 slightly reduces the fuel consumption, but it is possible to suppress the deterioration of the fuel consumption not only during the throttling operation but also when using the air pump. That is, it is possible to use the negative pressure device while ensuring low fuel consumption.

FIG. 8 shows the improvement rate of fuel consumption with respect to the intake negative pressure depending on whether or not EGR is introduced. The solid line shows the case where EGR is introduced, and the broken line shows the case where EGR is not introduced.
Point a is the present embodiment, that is, when EGR is introduced with a constant negative pressure, point b is EGR during non-throttling operation.
Shows the case where is not introduced.

As is apparent from FIG. 8, it is understood that fuel efficiency can be improved by introducing EGR even in non-throttling operation.

[0069]

As described above, the intake negative pressure control system for an internal combustion engine according to the present invention includes pressure accumulating means for accumulating the negative pressure in the intake pipe, pressure detecting means for detecting the pressure of the accumulating means, and an engine. An operating state detecting means for detecting the operating state of the vehicle, and an operating area determining means for determining whether or not the operating area in which the intake air amount is controlled only by the intake valve is determined based on the detection result of the operating state detecting means. And the pressure detected by the pressure detection unit is equal to or less than a predetermined value even when it is determined by the operation region determination unit that the intake air amount is controlled only by the intake valve. Since it has an intake negative pressure generating means for generating a negative pressure in the intake pipe by the intake valve and the throttle valve,
It is possible to generate the minimum required intake negative pressure in the operating region of the negative pressure device that uses the negative pressure in the intake pipe as the driving force source, and it is possible to use the negative pressure device while ensuring low fuel consumption.

Further, even when the vehicle brake booster is used as the negative pressure device, when the pressure of the pressure accumulating means is equal to or lower than the predetermined value, a negative pressure is generated in the intake pipe, and this negative pressure is generated via the pressure accumulating means. Since it is supplied to the vehicle brake booster, a desired braking operation can always be performed.

Further, even when it is judged by the operation area judging means that it is in the operation area where the intake air amount is controlled only by the intake valve, at least the specific operation state in which the control gas should be introduced into the control device. Since the intake valve and the throttle valve have the intake negative pressure setting means for setting the inside of the intake pipe to a predetermined negative pressure, the intake air amount can be easily controlled, and the throttle valve Since the differential pressure between the front and rear becomes constant, the accuracy of flow control of the negative pressure device is also improved.

Further, even when the evaporated fuel processing apparatus is used as the negative pressure device, the inside of the intake pipe is maintained at a predetermined negative pressure, so that the purge flow rate can be controlled accurately.

Further, even when an exhaust gas recirculation device is used as a negative pressure device, it can be operated with a minimum negative pressure, and low fuel consumption can be secured.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an intake negative pressure control device for an internal combustion engine according to the present invention.

FIG. 2 is a sectional view showing details of an intake valve operating mechanism.

FIG. 3 is an operating characteristic diagram of an intake valve.

FIG. 4 is a flowchart of an intake negative pressure control routine.

FIG. 5 is a diagram showing an EGR region.

FIG. 6 is a θTHTRGM map.

FIG. 7 is a characteristic diagram showing a fuel consumption improvement rate with respect to an intake negative pressure in the present embodiment together with a comparative example.

FIG. 8 is a characteristic diagram showing a fuel efficiency improvement rate with respect to intake negative pressure depending on whether or not EGR is introduced.

[Explanation of symbols]

 2 throttle valve 12 internal combustion engine 16 intake valve 19 TW sensor (operating state detecting means) 20 NE sensor (operating state detecting means) 21 TOIL sensor (operating state detecting means) 26 vacuum tank (pressure accumulating means) 27 VP sensor (pressure detecting means) ) 28 exhaust gas recirculation path 29 EGR valve 58 vehicle braking booster 59 θACC sensor (operating state detection means)

Claims (5)

[Claims] 1. An intake valve whose valve opening period can be arbitrarily changed,
In an intake negative pressure control device for an internal combustion engine having an electrically operated throttle valve and a control device using a negative pressure in the intake pipe as a driving force source, a pressure accumulating means for accumulating the negative pressure in the intake pipe and the pressure accumulating means. Detecting means for detecting the operating pressure of the engine, operating state detecting means for detecting the operating state of the engine, and detecting whether the operating state detecting means detects whether or not it is in an operating range in which the intake air amount is controlled only by the intake valve. Even if it is determined that the operating area determining means determines based on the result, the operating area determining means determines that the operating area is such that only the intake valve controls the intake air amount, the pressure detecting means An internal combustion engine having an intake negative pressure generating means for generating a negative pressure in the intake pipe by the intake valve and the throttle valve when the detected pressure is below a predetermined value. Intake negative pressure control apparatus. 2. The intake negative pressure control device for an internal combustion engine according to claim 1, wherein the control device is a vehicle braking booster. 3. An intake valve whose valve opening period can be arbitrarily changed,
In an intake negative pressure control device for an internal combustion engine having an electrically operated throttle valve and a control device for controlling a control gas introduced by a negative pressure in an intake pipe, an operating condition detecting means for detecting an operating condition of the engine, And an operating region discriminating unit for discriminating whether or not it is in an operating region in which the intake air amount is controlled only by the intake valve, based on the detection result of the operating state detecting unit. Even when it is determined that the intake air amount is controlled by only the valve, the intake valve and the throttle valve are used at least when in the specific operation state where the control gas should be introduced into the control device. An intake negative pressure control device for an internal combustion engine, comprising an intake negative pressure setting means for setting a predetermined negative pressure in the intake pipe. 4. The control device includes a fuel tank, a canister that adsorbs and stores evaporated fuel generated from the fuel tank, a purge passage that connects the canister and an intake system of an internal combustion engine, and a purge passage through the purge passage. 4. An intake air negative pressure control device for an internal combustion engine according to claim 3, which is an evaporated fuel processing device including a purge control valve mounted therein. 5. The intake negative pressure control device for an internal combustion engine according to claim 3, wherein the control device is an exhaust gas recirculation device that recirculates a part of exhaust gas to an intake pipe.