JPH0380969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for an engine, and more particularly, the present invention relates to an intake system for an engine, and more particularly, it supplies intake air into a cylinder through an intake passage during an intake stroke of an engine, and also supplies intake air into a cylinder during a compression stroke of an engine. The present invention relates to an intake system for an engine that returns a portion of the intake air to the intake passage and controls the amount of intake air filled by adjusting the amount of returned intake air.

In an automatic cycle engine, it is not possible to extract all of the thermal energy generated within the cylinders as shaft output, and a considerable portion of it is lost as various losses such as heat loss and mechanical loss, which becomes an obstacle to improving fuel efficiency. There is. One of these mechanical losses is the pump loss during the suction and exhaust strokes, and this pump loss is larger at low loads than at high loads, so
Automotive engines that are frequently used at low loads are hindered from improving fuel efficiency. On the other hand, it is known that installing an engine with a small stroke volume in the same vehicle improves fuel efficiency, but this is largely due to the reduction in pump loss since the engine operates at a relatively high load. This is thought to be one of the reasons. Therefore, if the engine performs the same function as a small stroke volume engine only at low loads, pumping loss at low loads can be reduced and fuel consumption can be improved without compromising the engine's required characteristics at high output. It is thought that it can be improved.

In other words, in order to reduce pump loss at low loads, it is necessary to reduce the throttling loss due to the increase in suction negative pressure based on the small throttle valve opening during the suction stroke and the compression loss during the compression stroke. good. As a means for this purpose, for example, as described in JP-A No. 55-69715, extra intake air is taken in during the intake stroke to reduce throttling loss, and a part of this intake air is transferred during the compression stroke. A method of significantly delaying the closing timing of the intake valve at low loads to cause leakage and reduce the effective stroke volume, or
As described in No. 52-139819, in addition to the normal intake passage, an auxiliary intake passage is provided to allow some of the intake air to leak out during the compression stroke, and an auxiliary intake valve is arranged in this auxiliary intake passage. The intake valve closing timing is set to be later than the normal intake valve closing timing,
A method is known in which the auxiliary intake valve is opened and closed when the engine is under low load, that is, when the engine is under partial load. It is believed that these engines have reduced pumping loss during intake of air-fuel mixture at low loads, resulting in greatly improved fuel efficiency.

However, in the engines disclosed in the above two patent publications, there is a valve that regulates the return amount when returning a part of the air-fuel mixture once sucked into the cylinder via the intake passage to the intake passage. The throttling effect of the intake valve of There is a problem in that an overrun phenomenon occurs in which the engine rotational speed exceeds the rotational speed corresponding to the set position of the operating member such as the accelerator pedal, that is, the set engine rotational speed.

SUMMARY OF THE INVENTION The present invention provides an engine intake system that reduces pump loss by returning a portion of the intake air-fuel mixture once supplied into the cylinder through the intake passage to the intake passage during low-load operation. The purpose of this is to prevent overruns caused by

The present invention supplies an air-fuel mixture into a cylinder through an intake passage during an engine's intake stroke, while exhausting a portion of the air-fuel mixture in the cylinder during an engine's compression stroke, and uses the amount of the air-fuel mixture during engine operation. Detecting the actual value of at least one of various operating signals governing engine rotational speed in an engine intake system that controls the filling amount of air-fuel mixture by adjusting it according to the state. a detection device, a setting device that sets a reference value of the actuation signal corresponding to the amount of accelerator operation; and a setting device that compares the actual value of the actuation signal with the reference value, and when the actual value is larger than the reference value, the intake air of the engine is This device is characterized by being provided with an intake air restriction device that limits the amount of filling.

As described above, the engine intake system according to the present invention is equipped with the above-mentioned intake air restriction device, and when the actual value of one operating signal that governs the engine speed during low-load operation is larger than the above-mentioned reference value, the engine Since the intake air filling amount is limited,
The rotational speed of the engine is suppressed, and the overrun phenomenon described above is prevented. Note that the above-mentioned operating signals that govern the engine speed include, for example, the output signal that an air flow sensor outputs by detecting the amount of intake air, as well as the output signal that an engine speed sensor outputs by detecting the actual engine speed itself. It may be a signal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an engine intake system according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an intake system for an engine according to an embodiment of the present invention. In this figure, the symbol E indicates an engine, and this engine E includes a cylinder C as a cylinder, and a cylinder C fitted in the cylinder C. piston P, and connecting rod R to this piston P.
It has a crankshaft S connected via.
At the top of this cylinder C, there is a normal intake port 1.
In addition to the exhaust port 2, an intake recirculation port 3, which is a third port, is provided. Intake port 1, exhaust port 2 and intake recirculation port 3,
An intake valve 7, an exhaust valve 8, and an intake recirculation valve 9 whose opening and closing are controlled by first, second, and third cams 4, 5, and 6, respectively, are arranged.

An intake passage 10 is connected to the intake port 1, and an exhaust passage 11 is connected to the exhaust port 2. The intake passage 10 is provided with a carburetor 12, and on the downstream side of the carburetor 12, the intake passage 12 is fully opened during normal operation and is closed during deceleration.
A valve 13 for closing 0 is provided. Intake passage 10
The downstream side of the valve 13 and the intake recirculation port 3 are:
It is communicated with by an intake recirculation passage 14 for recirculating intake air from the cylinder C to the intake passage 10 via the intake recirculation port 3 during the compression stroke. This intake recirculation passage 14 is provided with an on-off valve 15 that communicates with an accelerator pedal (not shown). The on-off valve 15 is configured to be fully closed when the load is full, and open at an opening degree corresponding to the load when the load is low.

A first cam 4 that controls opening and closing of the intake valve 7
is the rod 7 of the intake valve 7 as shown in FIG.
The cam profile in the cam shaft direction is changed so that the lift amount and closing timing of the intake valve 7 can be controlled depending on the position where a contacts the cam surface of the cam 4. The cam 4 is shaped so that the lift amount of the valve 7 becomes smaller and the closing timing becomes earlier as it goes to the left in the figure. The cam 4 is fixed to the shaft 16,
Enlarged diameter portions 16c and 16b are provided on both sides of the cam 4 of the shaft 16, respectively. The enlarged diameter portion 16a is slidably supported by guide members 17a and 17b fixed to a cylinder head (not shown) of the engine. An enlarged diameter portion 16c is provided further outward than the enlarged diameter portion 16a of the shaft 16,
A spring 18 is disposed between the enlarged diameter portion 16c and the guide member 17a. This spring 18 biases the shaft 16 and the cam 4 to the right in the figure.

A solenoid 19a and an armature 1 are provided on the end side of the shaft 16 in the direction biased by the spring 18.
An actuator 19 consisting of 9b is arranged. A pulley 20 is fixed to the opposite end of the shaft 16, a drive belt 21 is stretched around the pulley 20, and the pulley 20 is constantly driven to rotate by the drive belt 21. Along with this, the cam 4 is also constantly rotated.

The actuator 19 is connected to a drive circuit 22, and the armature 19a expands in proportion to the magnitude of the current output from the drive circuit 22. An input end of this drive circuit 22 is connected to an output end of a differential amplifier 23 . A reference voltage is applied to one input terminal of the differential amplifier 23 according to the opening degree of the on-off valve 15 detected by the opening sensor 24.
A reference voltage generation circuit 25 that generates V ₁ is connected. The reference voltage V ₁ indicates the reference rotation speed according to the amount of accelerator depression. The other output terminal of the differential amplifier 23 is connected to a voltage that detects the actual rotation speed of the engine E and indicates the rotation speed.
An engine speed sensor 26 that outputs V ₂ is connected.

Next, the operation of the engine intake system having the structure described above will be explained with reference to the valve operation timing chart of FIG.

First, when operating under high load when the accelerator pedal is depressed, the on-off valve 15 is closed, so intake air is supplied to the cylinder C via the intake passage 10 and the intake port 1, and from the cylinder C. Since intake air is not recirculated through the intake air recirculation port 3, the engine E is operated in the same manner as a normal engine.

Next, explaining the case of low-load operation, the on-off valve 15 is opened in conjunction with the release of the accelerator pedal. The cam 6 is configured to open and close the intake recirculation valve 9 with a certain phase delay from the intake valve 7, as shown in FIG. During this time, the intake recirculation port 3 and the intake recirculation passage 14 are opened.
A part of the intake air in the cylinder C is recirculated toward the intake passage 10 through the cylinder C. This recirculation amount is substantially determined by the opening degree of the on-off valve 15 and the intake recirculation valve 9.
It is adjusted according to the relationship with the closing timing of the load, and is set to increase as the load is smaller.

In the above-described operation of the engine intake system at low and medium loads, as the engine speed increases, the throttling effect of the recirculation valve 9 and the on-off valve 15 increases, resulting in an increase in the engine filling amount. The voltage output by the engine speed sensor 26
V ₂ is the reference voltage output from the reference voltage generation circuit 25
V will be higher than ₁ . That is, an overrun phenomenon occurs. Then, the differential amplifier 23 outputs a voltage V ₂
A voltage V ₃ proportional to the difference between the voltage V 1 and the reference voltage V ₁ is generated.
The drive circuit 22 generates a current I proportional to this voltage _V3 .
is generated and this current I is output to the actuator 19. The actuator 19 operates the solenoid 19b in proportion to this current I to control the armature 19a.
, thereby causing the shaft 16 to be connected to the spring 1
8 to the left in the figure, and also moves the cam 4 to the left. In this way, the axial position where the rod 7a of the intake valve 7 contacts the cam surface of the cam 4 is changed, the lift amount of the intake valve 7 is reduced as shown by the two-dot chain line in FIG. 3, and the closing timing is advanced. This reduces the amount of intake air, reduces the charge amount, and lowers the engine speed. The above prevents overrun.

Next, an air supply system for a fuel injection engine according to a second embodiment of the present invention will be described with reference to FIG. 4 and subsequent figures. Among the members and elements shown in FIG. 4, those having the same functions as those shown in FIGS. 1 to 3 are given the same reference numerals, and their explanations will be omitted.

In this embodiment, the third valve, which is the intake recirculation valve, is not used, and the closing timing of the intake valve 7 is changed according to the engine load as shown in FIG. The amount of intake air pushed back into the intake port 1 by the rise of the piston P is controlled, and the cylinder volume when the intake valve closes during the compression stroke is set as the effective volume, and the system is operated in the same manner as in the first embodiment, during low load operation. This reduces pumping losses.

In FIG. 4, the reference numeral 30 indicates a fuel injection valve, the reference numeral 31 an air flow sensor that detects the intake air flow rate, and the reference numeral 32 the air flow rate detected by the air flow sensor 31, which is detected by the engine rotation speed sensor 26. 3 shows injection control circuits that control the injection timing and amount of fuel by the fuel injection valve 30 based on the engine rotation speed. The injection control circuit 32 is composed of a microcomputer.

The cam 4' that drives the intake valve 7 has a cam profile that is changed in the camshaft direction so that only the closing timing of the intake valve 7 can be changed. By moving cam 4' in the cam axis direction,
The intake recirculation amount is adjusted by changing the opening/closing characteristics of the intake valve 7 so as to delay the valve closing timing, as shown in FIG. 5, depending only on the load.
This controls the filling amount. The filling amount decreases as the closing timing of the intake valve 7 is moved toward the compression top dead center side.

In the case of this second embodiment as well, the above-mentioned overrun phenomenon occurs due to an increase in the throttling effect of the intake valve 7 as the engine speed increases.

In the case of the first embodiment described above, overrun was prevented by reducing the filling amount by controlling the lift amount and valve closing timing of the intake valve 7.
In this embodiment, the amount of intake air is adjusted by closing the valve 13 according to the degree of overrun, thereby reducing the filling amount and preventing overrun.

The valve body 13a of the valve 13 is attached to a rotating shaft 13b with one end protruding from the intake passage 10,
A pulley 40 is attached to the one end of this rotating shaft 13b. On the other hand, a pulley 42 is also attached to the output shaft 41a of the step motor 41, and an endless belt 43 that transmits the rotation of the pulley 42 to the pulley 40 is stretched between the pulley 42 and the pulley 40. A drive circuit 22' is connected to the step motor 41. This drive circuit 22' uses the voltage V ₃ output from the differential amplifier 23.
The step motor 41 is rotated by the same number of steps as the number of pulses P.

In this embodiment, a depression amount sensor 24' that detects the depression amount of the accelerator pedal is used in place of the opening sensor 24. The reference voltage generation circuit 25 is
A reference voltage V ₁ is generated corresponding to the engine rotational speed according to the amount of depression of the accelerator pedal detected by this depression amount sensor 24'. Furthermore, instead of the engine speed sensor 26, an air flow sensor 31 is used that detects the amount of incoming air, which is one of the factors that govern the engine speed.

Next, the operation of the control system of the embodiment described above will be briefly explained. When an overrun phenomenon occurs as described above, based on the output voltage V ₁ from the reference voltage generation circuit 25 connected to the depression amount sensor 24' and the output voltage V ₂ from the air flow sensor 31,
Differential amplifier 23 outputs voltage V ₃ and drives circuit 2
2' outputs a number of pulses P corresponding to the height of this voltage 23. The step motor 41 moves the output shaft 41a by the number of steps corresponding to the number of pulses P.
Rotate. The rotation of this output shaft 41a is caused by the pulley 42, belt 43, pulley 40 and shaft 13b.
is transmitted to the valve body 13a through the valve body 13a, and rotates the valve body 13a in the closing direction. This reduces the amount of air taken in by the intake passage 10, reducing the amount of charge in the engine, thus preventing overrun.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an engine intake system according to a first embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a control system used in the intake system shown in FIG. 1, FIG. 3 is an opening/closing timing chart showing the opening/closing characteristics of the valve of the intake system shown in FIG.
FIG. 4 is a schematic diagram showing an engine intake system according to the second embodiment, FIG. 5 is an opening/closing timing chart showing the opening/closing characteristics of the valves of the intake system shown in FIG. 4, and FIG. 4 is a circuit diagram showing an example of a control system used in the intake device shown in FIG. 4. FIG. E...Engine, C...Cylinder as cylinder, P...Piston, 1...Intake port, 2...
Exhaust port, 3... Intake recirculation port, 7... Intake valve, 8... Exhaust valve, 9... Intake recirculation valve, 10... Intake passage, 11... Exhaust passage, 13
... Valve, 14 ... Intake recirculation passage, 15 ... Opening/closing valve, 19 ... Actuator, 22 ... Drive circuit, 23 ... Differential amplifier, 24 ... Opening sensor,
25... Reference voltage generation circuit, 26... Rotation speed sensor.

Claims (1)

[Claims] 1. During the intake stroke of the engine, the air-fuel mixture is supplied into the cylinder through the intake passage, while during the compression stroke of the engine, a part of the air-fuel mixture in the cylinder is exhausted, and the amount of the air-fuel mixture is adjusted according to the operating state of the engine. A detection device for detecting the actual value of at least one operating signal among various operating signals governing engine rotational speed, in an engine intake system configured to control the filling amount of the air-fuel mixture by adjusting the amount of air-fuel mixture; a setting device that sets a reference value of the actuation signal corresponding to the amount of accelerator operation; and a setting device that compares the actual value of the actuation signal with the reference value, and when the actual value is larger than the reference value, sets the intake air filling amount of the engine. An intake system for an engine, characterized in that it is provided with an intake limiting device.