JPH0450426Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is an engine intake system, in particular, an intake system in which the intake passage is composed of a primary intake passage and a secondary intake passage, and a control valve is disposed in the secondary intake passage. The present invention relates to an intake system for an engine installed in the engine.

(Prior art) As an engine intake system, the intake passage is composed of a primary intake passage with a small passage cross-sectional area and a secondary intake passage with a large passage cross-sectional area, and the secondary intake passage is closed when the engine is under low load. Additionally, some are equipped with a control valve that opens when the load is high. This is achieved by supplying intake air to the combustion chamber only from the primary intake passage, which has a small passage cross-sectional area, at low load in an engine with a small amount of intake air, thereby increasing the flow velocity of the intake air or creating a swirl by the intake air within the combustion chamber. This promotes fuel vaporization and atomization and the propagation of fire after the fuel is ignited, thereby improving combustibility and fuel efficiency at low loads. Next, by supplying intake air from both of the secondary intake passages, a required intake air filling amount can be ensured.

By the way, in this type of intake system, although the strength of the swirl required to ensure good fuel efficiency etc. differs slightly depending on the operating range of the engine, the above-mentioned 2. Normally, the control valve of the next intake passage is selectively controlled to either a fully open state or a fully closed state depending on the engine load and the like. Therefore, depending on the settings such as the cross-sectional area or shape of the primary intake passage or the shape or size of the combustion chamber, sufficient swirl may not be obtained at extremely low loads such as when idling, or in some cases. However, there was a problem in that the swirl was rapidly weakened under low and medium loads, making it impossible to fully utilize the effect of swirl on improving combustibility.

To deal with this, for example, as shown in Japanese Patent Application Laid-Open No. 59-65515, the control valve of the secondary intake passage is kept fully closed or nearly fully closed when the engine is under extremely low load. An engine intake system has been proposed that includes a control device that maintains the opening at a predetermined opening (constant low opening) at times, and fully opens the intake when the load is high. According to this, at times of extremely low load such as during idling when the amount of intake air is extremely small, the intake air supplied only from the primary intake passage generates a strong swirl within the combustion chamber, further improving combustibility. At low to medium load, which is the normal operating range, the secondary intake passage is opened at a suitable communication ratio to generate a swirl of the desired strength in the combustion chamber while ensuring an appropriate amount of intake air to improve combustibility. In addition, during high loads, it is possible to supply a large amount of intake air into the combustion chamber from both the primary and secondary intake passages as before, thereby increasing engine output.

(Problems to be solved by the invention) By the way, the control device shown in the above publication has two problems.
Since it uses an actuator with a heavy diaphragm structure, its configuration tends to be complicated.

That is, the specific configuration of this control device is such that the inside of the actuator is partitioned into a first and second negative pressure chamber by two diaphragms, and two negative pressure introduction passages communicating with both negative pressure chambers are used as an intake passage. Each passage is opened at a predetermined location (two different locations). Then, the displacement of the diaphragm is appropriately controlled based on the magnitude of the intake negative pressure generated in each of the openings and the difference between the two, and the displacement of one diaphragm is arranged in the secondary intake passage. By converting the opening/closing operation of the control valve into the opening/closing operation of the control valve, the opening degree of the control valve can be changed in three stages according to the engine load as described above. Therefore,
In this device, each diaphragm is biased in a predetermined direction within the actuator.
Not only does the structure of the actuator itself become complicated as it is necessary to include two elastic members and a linkage mechanism for linking both diaphragms, but it is also necessary to provide two negative pressure introduction passages leading into the actuator as described above. Due to this nature, the passage structure becomes complicated, which leads to problems such as a large-scale control device or an increase in cost.

(Means for Solving the Problems) The present invention provides an engine intake system, particularly an intake system having a primary intake passage for swirl generation and a secondary intake passage provided with a control valve as an intake passage. By providing a control mechanism that can appropriately control the opening degree of the control valve with a simple configuration and generating swirls of desired strength in the combustion chamber at extremely low loads and low to medium loads of the engine, combustibility can be improved. The purpose of the present invention is to improve fuel efficiency, etc., and is characterized by the following configuration.

That is, the engine intake system according to the present invention has a primary intake passage and a secondary intake passage as intake passages, and the secondary intake passage is provided with a control valve. It has a negative pressure actuator that operates the control valve in the closing direction when the negative pressure is larger than a first set negative pressure, and the actuator is connected to a single negative pressure chamber and an atmospheric chamber partitioned by a diaphragm. The actuator controls the control valve by connecting one negative pressure introduction passage for introducing intake negative pressure into the negative pressure chamber and contacting a connecting member connecting the actuator and the control valve. A locking portion is provided that restricts the movement in the closing direction at a predetermined opening degree by the elastic force of the elastic member. The elastic force of the elastic member is adjusted when the intake negative pressure exceeds a second set negative pressure that is larger than the first set negative pressure (which is smaller than the first set negative pressure in terms of absolute pressure). The control valve is set to a value that causes the control valve to be operated in the closing direction from the predetermined opening degree. In that case, the first set negative pressure is set to a value that can divide the operating range of the engine into a high load range and a low to medium load range, and the second set negative pressure is set to a value that can divide the operating range of the engine into a high load range and a low to medium load range. These values are appropriately set to allow division into regions.

(Function) According to the above configuration, when the intake negative pressure corresponding to the engine load is smaller than the first set negative pressure, that is, when the engine is under high load, the negative pressure actuator becomes inactive. Therefore, the control valve of the secondary intake passage is fully open, and a large amount of intake air is supplied into the combustion chamber from both the primary and secondary intake passages.

On the other hand, during the time when the intake negative pressure exceeds the first set negative pressure and reaches the second set negative pressure, that is, when the engine is under low to medium load, which is the normal operating range, the control valve is operated by the actuator. However, in this case, the elastic force of the elastic member in the locking portion overcomes the biasing force of the actuator, so that the control valve is opened to a predetermined opening degree (constant low opening degree).
is maintained, and the secondary intake passage is opened at an appropriate communication ratio. As a result, during low to medium load conditions when the intake air amount is not large enough to fully open the control valve, the intake air supplied from the primary intake passage into the combustion chamber generates a swirl of desired strength to improve combustibility. However, the desired amount of intake air supplied from the secondary intake passage makes it possible to suitably improve the intake air filling efficiency. Furthermore, in this case, the predetermined opening degree is set to a value that can minimize the fuel consumption rate under low and medium loads, so it is possible to improve fuel efficiency in such an operating range.

Further, when the intake negative pressure exceeds the second set negative pressure, that is, when the load of the engine is extremely low, the biasing force of the actuator overcomes the elastic force of the elastic member at the locking portion, so that the control is performed. The valve is fully closed or approximately fully closed, and intake air is mainly supplied into the combustion chamber only from the primary intake passage. As a result, a strong swirl is generated in the combustion chamber at times of extremely low load such as when the engine is idling when the amount of intake air is extremely small, making it possible to ensure good combustion performance. In addition, by controlling the opening degree of the control valve in three stages as described above, the passage of the primary intake passage can be adjusted to generate a swirl that meets the respective requirements, especially at extremely low loads and low to medium loads. This makes it possible to appropriately set the condition and shape of the combustion chamber.

In particular, according to the above configuration, the negative pressure operated actuator that changes the opening degree of the control valve of the secondary intake passage is an actuator having a single negative pressure chamber and an atmospheric chamber, and the negative pressure The chamber and the intake passage are communicated through a single negative pressure introducing passage, and the locking portion can be of a simple structure, such as a movable stopper equipped with a spring having a desired elastic force. Moreover, since the locking portion acts on the connecting member that connects the actuator and the control valve, it can be provided outside the actuator and independently from the connecting member,
Therefore, a very common general-purpose actuator can be used as the actuator. As a result, the configuration of the control device that controls the opening degree of the control valve in three stages is significantly simplified.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings, and this embodiment is an application of the present invention to a carburetor type engine.

As shown in FIG. 1, an engine 1 includes a cylinder bore 2a formed in a cylinder block 2, an upper surface of a piston 3 fitted into the bore 2a, and a cylinder head 4 mounted above the cylinder block 2. The combustion chamber 5 has a combustion chamber 5 formed of a lower surface, and is provided with an intake passage 8 and an exhaust passage 9 that communicate with the combustion chamber 5 via intake and exhaust valves 6 and 7, respectively. The intake passage 8 includes an intake port 10 formed in the cylinder head 4 and an internal passage 12 of an intake manifold 11 connected to one side of the head 4.
and an internal passage 17 of a carburetor 16 connected to the upstream end face of the manifold 11 and provided with a bench lily portion 13, a fuel nozzle 14, and a throttle valve 15, respectively. An air cleaner (not shown) is installed at the end, and the exhaust passage 9 connects to the cylinder head 4.
The head 4 includes an exhaust port 18 formed in the head 4, and an exhaust manifold (not shown) connected to the other side of the head 4.

On the downstream side of the intake passage 8, there is a combustion chamber 5 branched from the internal passage 12 of the intake manifold 11 and located at the intake port 10 of the cylinder head 4.
A passage 19 having a small passage cross-sectional area is provided immediately upstream of the opening to the combustion chamber 5, and this passage 19 serves as a primary intake passage that generates a swirl of intake air within the combustion chamber 5. Further, a control valve 20 is installed immediately downstream of the upstream branch of the primary intake passage 19 in the internal passage 12 of the intake manifold 11,
A passage 21 having a large passage cross-sectional area leading to the combustion chamber 5 via this control valve 20 is used as a secondary intake passage.

Note that a camshaft 22 is mounted on the top of the cylinder head 4.
A valve operating mechanism 29 is provided, which includes intake and exhaust valve cams 23 and 24 formed in the same manner as shown in FIG. The rotation of a crankshaft (not shown) is transmitted to the camshaft 22, so that the intake and exhaust valves 6 and 7 are opened at predetermined times.

However, at the downstream end of the intake manifold 11, there is a control valve 20 disposed in the secondary intake passage 21.
A control device 30 is provided to control the opening degree of. This control device 30 includes a negative pressure operated actuator 31 in which an internal space of a casing 31a is partitioned by a diaphragm 31b into a single negative pressure chamber 31c and an atmospheric chamber 31d, and a displacement of the diaphragm 31b in the actuator 31. Swing mechanism 32 that converts the opening/closing operation of the control valve 20
and a movable stopper 33 that restricts the closing operation of the control valve 20 by the mechanism 32. It is configured to communicate with the downstream side of the tutle valve 15. Then, by introducing the intake negative pressure generated in the intake passage 8 into the negative pressure chamber 31c of the actuator 31, the diaphragm 31b is moved against the first spring 31e compressed in the negative pressure chamber 31c. The operating rod 35 whose upper end is fixed to the diaphragm 31b is also moved upward in the figure, and in addition to this movement, the swing mechanism 32 and movable stopper 33 perform predetermined movements. By doing so, the opening degree of the control valve 20 is controlled in accordance with the intake negative pressure, that is, the engine load. As described above, the intake negative pressure when the diaphragm 31b starts to move upward against the first spring 31e is set as the first set negative pressure.

Here, the swing mechanism 32 and the movable stopper 3
The configuration of No. 3 will be explained in detail based on FIG. As shown in the figure, the swinging mechanism 32 has a lever 37 that is fixed to the swinging shaft 36 of the control valve 20 so as to be able to swing integrally with the valve 20, and a predetermined portion of the lever 37. By pivoting the lower end of the operating rod 35 fixed to the diaphragm 31b of the actuator 31, the operating rod 35 of the actuator 31 and the control valve 20 are connected via the lever 37. The lever 37 is configured to swing in the direction a as the lever 35 moves upward. On the other hand, the movable stopper 33
The base member 38 is fixedly installed near the downstream flange of the intake manifold 11, and the movable member is fitted into a through hole formed in the member 38 and is movable back and forth within a predetermined dimension ₁ . 39, and a second spring 40 is compressed between the hemispherical portion 39a formed at the tip of the member 39 and the base member 38. Then, the tip end (free end side end) of the lever 37 in the swing mechanism 32 swings in the direction a with the upward movement of the operating rod 35, and the hemispherical part 39a of the movable member 39 in the movable stopper 33 When the lever 37 comes into contact with the lever 37 (see FIG. 3), the swinging of the lever 37 in the direction a, that is, the swinging of the control valve 20 in the closing direction, is temporarily prevented. Furthermore, from such a state, the biasing force acting on the lever 37 in the direction a increases and overcomes the spring force of the second spring 40, causing the lever 37 to further swing in the direction a. The movable member 39 has a predetermined size.
When the lever 37 is moved backward by ₁ (see FIG. 4), the swinging of the lever 37 is stopped and the control valve 20 is fully closed. and,
As mentioned above, the lever 3 resists the second spring 40.
The above actuator 31 when 7 resumes rocking
The intake negative pressure in the negative pressure chamber 31c at is set as the second set negative pressure. Therefore, this second set negative pressure is
The first set negative pressure is set to a value larger than the first set negative pressure (a smaller value in terms of absolute value), and in this case, the first set negative pressure divides the operating range of the engine 1 into a high load range and a low to medium load range. The second set negative pressure is set to a value that can be divided into a low-medium load area and an extremely low load area.

Next, the operation of the above embodiment will be explained.

First, as shown in FIG. 1, when the engine 1 is under high load and the throttle valve 15 disposed on the upstream side of the intake passage 8 is opened at a large opening, the throttle valve 15 in the intake passage 8 is opened at a large opening. valve 15
The intake negative pressure generated on the downstream side of , that is, near the opening of the negative pressure introduction passage 34 becomes smaller than the first set negative pressure _P1 . Therefore, the intake negative pressure introduced into the negative pressure chamber 31c of the negative pressure actuator 31 through the negative pressure introduction passage 34 is compressed to correspond to the first set negative pressure _P1 . 1 spring 31e
The diaphragm 31b cannot be displaced against the spring force of 2, and therefore the control valve 20 disposed in the secondary intake passage 21 is forced to move as shown in FIGS. Alternatively, it is held in the fully open state as shown by reference numeral A in FIG. As a result, a large amount of intake air or air-fuel mixture is supplied to the combustion chamber 5 through both the primary and secondary intake passages 19 and 21, and the output of the engine 1 is increased.

On the other hand, in a low to medium load region where the throttle valve 15 is closed to a certain extent and has a relatively small opening, the intake negative pressure becomes the first set negative pressure _P1.
, the diaphragm 31b and the operating rod 35 are moved upward against the first spring 31e, and the lever 37 of the swing mechanism 32 is accordingly moved upward.
and the control valve 20 is swung in the direction a in FIG.
As shown in the figure, the tip of the lever 37 comes into contact with the movable member 39 of the movable stopper 33. In this case, since the above-mentioned intake negative pressure has not reached _the second set negative pressure _P2 , the above-mentioned intake negative pressure is The lever 37 cannot move the movable member 39 backward to the right in the drawing, and therefore, in this low-medium load region, the control valve 20 operates at a predetermined low opening α as shown by the symbol B in FIG. held at ₀ .
As a result, the combustion chamber 5
Since the intake air supplied from the primary intake passage 19 is set to be a small amount and the optimum amount, the swirl generated in the combustion chamber 5 by the intake air supplied from the primary intake passage 19 is set to the desired strength, and the intake air is filled appropriately. This makes it possible to secure a sufficient amount of fuel, and the effect of improving combustibility in the low-medium load region, which is the normal operating region, can be favorably obtained. Note that the predetermined low opening degree α ₀ is the opening degree that minimizes the fuel consumption in this operating range, so it is also possible to improve fuel efficiency.

Furthermore, in an extremely low load region where the throttle valve 15 has an extremely small opening, the intake negative pressure becomes greater than the second set negative pressure _P2 , so
The rightward biasing force acting on the movable member 39 from the diaphragm 31b of the actuator 31 via the operating rod 35 and lever 37 overcomes the spring force of the second spring 40, and the movable member 39
is moved backward by a predetermined distance ₁ , and as a result, the movable member 39 reaches the backward end and the lever 37 reaches the swing end, as shown in FIG. As shown by symbol C in the figure, it is in a fully closed state. As a result, in the idle region where the amount of intake air is extremely small, the intake air is supplied to the combustion chamber 5 only from the primary intake passage 19 whose passage cross-sectional area is set small, so that the flow rate within the chamber 5 is low. The increased intake air generates a powerful swirl, further improving combustion performance.

As described above, the opening degree of the control valve 20 is controlled in three stages depending on the magnitude of the intake negative pressure, that is, the engine load, thereby providing two-stage control for either fully open or fully closed. Compared to the previous case, a sufficiently strong swirl can be obtained at extremely low loads, and the problem of sudden weakening of the swirl at low to medium loads can be avoided. Looking at this from another perspective, by performing the three-stage control as described above, the passage condition of the intake passage 8, especially the primary intake passage 19, the shape of the combustion chamber 5, etc. are controlled at extremely low loads. It becomes possible to appropriately set the swirl so that the required strength of swirl can be generated at low and medium loads.

In particular, according to the above embodiment, the negative pressure actuator 31 having a single diaphragm structure,
The control device 30, which is composed of one negative pressure introduction passage 34, a swing mechanism 32 of a simple structure, and a movable stopper 33, controls the opening degree of the control valve 20 according to the magnitude of the intake negative pressure. Since the control is performed appropriately and reliably in three stages, the negative pressure operated actuator 31 may be, for example, an actuator with a double diaphragm structure or the movable stopper 33.
There is no need to use an actuator with a double spring structure that has the function of . Additionally, the control device 30
It is also possible to reduce the size and cost of the device.

(Effects of the invention) As described above, according to the invention, in the intake system for an engine in which the intake passage is composed of a primary intake passage and a secondary intake passage, and a control valve is disposed in the secondary intake passage, The diaphragm, spring, and negative pressure chamber are all used as a control device that fully closes the control valve during extremely low engine loads, maintains it at a predetermined low opening during low and medium loads, and fully opens the control valve during high loads. A control device with a simple structure consisting of one extremely common general-purpose negative pressure operated actuator, one negative pressure introduction passage, a movable stopper, etc. is realized. As a result, while simplifying this type of control device and reducing costs, it becomes possible to generate swirls of the desired strength required especially at extremely low loads and low to medium loads, thereby making it possible for the engine to Combustibility, fuel efficiency, etc. will be improved.

[Brief explanation of the drawing]

1 to 5 show examples of the present invention,
FIG. 1 is a longitudinal cross-sectional view showing a schematic configuration of an engine intake system and a control device for a control valve provided in the engine according to the present invention; FIG. 2 is an enlarged cross-sectional view of the main parts of the control device; FIG. 4 is an enlarged cross-sectional view of a main part showing the action of the first embodiment, and FIG. 5 is a graph showing the action and effect of the first embodiment. 1...Engine, 8...Intake passage, 19...1
Secondary intake passage, 20...Control valve, 21...Secondary intake passage, 31...Negative pressure actuator, 31
b...Diaphragm, 31c...Negative pressure chamber, 31d
...atmospheric chamber, 33...locking part (movable stopper),
34... Negative pressure introduction passage, 40... Elastic member (second
spring).

Claims (1)

[Scope of utility model registration request] An intake system for an engine, wherein the intake passage is constituted by a primary intake passage and a secondary intake passage, and a control valve that closes when the engine is under low load and opens when the engine has a high load is disposed in the secondary intake passage, The control valve has a negative pressure actuator that operates the control valve in the closing direction when the intake negative pressure generated in the intake passage is larger than a first set negative pressure, and the actuator is defined by a diaphragm. It is composed of a negative pressure chamber and an atmospheric chamber, and is connected to a negative pressure introduction passage that introduces intake negative pressure into the negative pressure chamber, and is a connecting member that connects the actuator and the control valve. A locking portion is provided that restricts the operation of the control valve in the closing direction by the actuator at a predetermined opening degree by the elastic force of the elastic member, and the elastic member is arranged such that the intake negative pressure is The intake air of the engine is characterized in that its elastic force is set so as to operate the control valve in the closing direction from the predetermined opening degree when a second set negative pressure that is greater than the first set negative pressure is exceeded. Device.