JPS6220626A - Suction device for diesel engine - Google Patents

Abstract

PURPOSE:To improve a degree of combustibility at a wide engine speed range, by installing plural pieces of an on-off valve in each suction passage side by side,and varying each valve opening suction pressure of these valves, in case of a device which installs these on-off valves, restricting the extent of suction intake up to the point midway in a suction stroke, in the suction passage at every cylinder. CONSTITUTION:Each of on-off valves 11 and 12 consisting of a suction pressure responsive valve is installed side by side in an auxiliary suction passage 9b of a suction passage 9, classified by cylinders, to be interconnected to a suction port 5, and with these on-off valves 11 and 12, suction intake into a combustion chamber 3 is restricted up to the point midway in a suction stroke, but from the midway of the suction stroke, suction air is suddenly lead into the combustion chamber 3 whereby adiabatic compression is made so as to be performed. Also a suction throttle valve 13 is installed in a main suction passage 9a. Each of these on-off valves 11 and 12 is provided with the valve body 17 connected to a diaphragm 19 via a coupling shaft 18 and constituted to be be opened by suction pressure to be taken from an interconnecting hole 23 to a chamber 20 against a spring 22. In addition, each of these on-off valves 11 and 12 varies energizing force of the spring 22 for these valves whereby each suction pressure is made so as to be varied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an intake system for a diesel engine that increases the temperature of intake air through compression in order to promote starting of the diesel engine and improve emissions.

(Prior Art) Conventionally, as shown in Japanese Utility Model Application Publication No. 59-107936, in order to improve the ignitability at the time of starting a diesel engine, the intake air supplied to the combustion chamber is definitely compressed to increase the intake air temperature. Intake devices (starting promotion devices) are known. This device is provided with an on-off valve in the intake passage that opens during the intake stroke, and specifically, an intake throttle valve is provided in the main intake passage, and a bypass intake passage that bypasses the intake throttle valve is provided with an intake valve. An 0rIi valve is provided, and the rM opening/closing valve is opened in the middle of the intake stroke while the main intake passage is throttled by the intake throttle valve during low-load operating conditions from startup to warm-up. By operating such an on-off valve, the introduction of intake air into the combustion chamber is restricted until the middle of the intake stroke, and intake air is suddenly introduced into the combustion chamber from the middle of the intake stroke to ensure compression. According to this device, compared to the case where intake air is heated by an air heater, a large amount of energy is not consumed as electric power, and moreover, the intake air temperature can be efficiently raised in the combustion chamber. In addition, in the above-mentioned conventional device, the on-off valve is operated during startup and warm-up operation, but even during normal operation, the combustion chamber temperature is low and poor combustion may occur, such as during low-load, low-speed operation, etc. If the on-off valve is operated in this region, combustion performance will be improved by raising the intake air temperature, and generation of white smoke, HC, etc. will be prevented.

In addition, the on-off valve heard during the intake stroke in this device is of the type that is driven by the engine output shaft via a valve train or interlocking mechanism, or that has a set negative pressure depending on the negative pressure generated within the cylinder. It is possible to adopt a type that opens when the positive pressure is reached (a negative pressure responsive valve), but if the latter type is used, the intake air can be completely compressed with a simple structure without the need for a valve mechanism or interlocking mechanism. can be made to do so.

By the way, when using an on-off valve consisting of such a negative pressure responsive valve, conventionally the on-off valve, which opens when the negative pressure in the cylinder reaches a certain set negative pressure, is placed in each intake passage for each cylinder. Since only one of them is provided, it is difficult to achieve a good compression effect of the intake air over a wide rotational speed range.

In other words, in order to definitely increase the compression effect of the intake air, it is desirable to increase the opening negative pressure of the on-off valve, but the negative pressure generated inside the cylinder is proportional to the amount of leakage intake air flowing into the cylinder from around the piston, etc. The engine speed is low due to
[It tends to become smaller as the For this reason, for example, if the valve-opening negative pressure is set to a certain degree so that a good compression effect can be obtained in the rotation speed range above idling speed, the negative pressure in the cylinder will be lower than the valve-opening negative pressure during cranking at a low engine speed. The pressure may not be reached, and the on-off valve may no longer open, which may prevent the intake air from being compressed or filling the intake air. In addition, even if the opening operation is performed, the rotation speed is low and the intake period is long, so
Once metered, the on-off valve closes before BDC, adiabatic expansion occurs, and the intake air temperature decreases, causing problems such as insufficient intake air volume and smoke generation. To explain this specifically, using the measurement results of the relationship between the engine speed during motoring and the average temperature inside the cylinder shown in Fig. 9, when one on-off valve is used with the above settings. The average temperature inside the cylinder is as shown by line A, and compared to the case without using an on-off valve (line B), the effect of increasing the intake air temperature is obtained above the idle speed, but as a result, the above effect cannot be obtained at low speeds. do not have. This is BD below the idle speed.
It is considered that the on-off valve closes before C and the temperature decreases due to adiabatic expansion. Therefore, in order to obtain a sufficient compression effect, it is necessary to close the on-off valve after BDC regardless of the rotation speed.

In addition, if the opening/closing valve negative pressure is set small enough to ensure that the opening/closing valve opens at low rotation speeds such as during cranking, the compression effect of the intake air can be kept low even if the rotation speed increases to a certain extent during normal operation. You will end up getting hurt.

As a means to solve this problem, it is possible to adjust the opening negative pressure of the on-off valve and control the opening negative pressure according to the engine speed. The structure of the mechanism for adjusting the negative pressure and the means for controlling it is WIN.

(Objective of the Invention) In view of the above circumstances, the present invention is capable of exhibiting an excellent compression effect of intake air over a wide rotation speed range, and
To provide an intake system for a diesel engine that can sufficiently achieve startup acceleration when starting at a low rotation speed and sufficient reduction of white smoke, HC, etc. even in a relatively high rotation range during normal operation. .

(Structure of the Invention) The present invention provides an on-off valve in the intake passage for each cylinder of an engine, and the on-off valve is a negative pressure responsive valve that opens when the negative pressure in the cylinder reaches the valve opening negative pressure. This is a diesel engine that is configured by the on-off valve, which restricts the intake air into the combustion chamber until the middle of the intake stroke, and suddenly introduces the intake air into the combustion chamber from the middle of the intake stroke to ensure compression. In the intake system, a plurality of the on-off valves are arranged in parallel in the intake passage, and the opening negative pressure of each on-off valve is set to a different value.With this configuration, a plurality of on-off valves with different opening negative pressures can be set. The on-off valve operates according to the engine speed, and the intake air is compressed well over a wide range of engine speeds.

(Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention. In these figures, 1 is a cylinder of a diesel engine, and a combustion chamber 3 is formed above a piston 2 inside the cylinder.This combustion chamber 3 includes an intake boat 5 with an intake valve 4 and an exhaust valve 6. An exhaust boat 7 equipped with a fuel injection valve 8 is opened, and a fuel injection valve 8 is provided. An intake passage 9 is communicated with the intake boat 5, and an exhaust passage 10 is communicated with the exhaust boat 7. In the intake passage 9 for each cylinder that communicates with the intake boat 5, on-off valves 11 and 12, which are negative pressure responsive valves, restrict the introduction of intake air into the combustion chamber 3 until the middle of the intake stroke. An intake air introduction device is provided which introduces intake air into the combustion chamber 3 and causes it to be compressed. In this intake air introduction device, a plurality of on-off valves are arranged in parallel, for example, two on-off valves 11.
12 are arranged in parallel.

In this embodiment, the intake air introduction device has a main intake passage 9a and a sub-intake passage 9b forming an intake passage 9 for each cylinder, and an intake throttle valve 13 is provided in the main intake passage 9a. A sub-intake passage 9b opens downstream from the valve 13, and two on-off valves 11 and 12 are installed in this sub-intake passage 9b.
are arranged in parallel. Note that the main intake passage 9a and the auxiliary intake passage 9b are connected to the surge tank 14.
It is connected to an air cleaner (not shown) via.

Each of the above-mentioned on-off valves 11.12 responds to the negative pressure generated in the cylinder 1 during the intake stroke when the main intake passage 9a is closed by the intake throttle valve 13. The structure is such that the valve opens automatically when the opening negative pressure is reached, and specifically, the structure is as shown in FIG. 2.

The on-off valve 11 (the same goes for the in-close valve 12) includes a valve body 17 provided in the valve chamber 15 and abutting the valve seat 16 from the upstream side, and a valve body 17 connected to the valve body 17 via a connecting shaft 18. diaphragm 19, two chambers 20 and 21 partitioned by this diaphragm 19, and a return spring 22 provided in one of the chambers 20 and urging the valve body 17 in the valve opening direction. . The one chamber 20 communicates with the downstream side of the valve body 17 through a communication hole 23 passing through the valve body 17, the connecting shaft 18, and the diaphragm 19, and the other chamber 21 communicates with the valve body 17 through an opening 24. It communicates with the upstream side and is maintained at approximately atmospheric pressure.

With this structure, in the on-off valve 10.11, the negative pressure introduced into the one chamber 20 from the downstream side of the auxiliary intake passage 9b is determined by the biasing force of the return spring 22 and the pressure receiving areas of the valve body 17 and the diaphragm 19. When the set negative pressure is reached, that is, when the force acting on the diaphragm 19 due to the negative pressure becomes greater than the resistance force due to the return spring 22 and the negative pressure acting on the valve body 17 itself, the valve body 1
7 will be held. Further, the valve opening model is such that the valve body 17 is closed when the negative pressure becomes sufficiently small. Note that when the intake throttle valve 13 of the main intake passage 9a is opened, almost no intake negative pressure is generated, so the opening and closing operations of the on-off valves 11 and 12 are stopped.

The above-mentioned on-off valves 11 and 12 are set to have different opening negative pressures by making the biasing force of each return spring 22 different. The opening/closing valve 11 (hereinafter referred to as the "first on-off valve") is set to have a relatively low opening negative pressure so that it opens and closes properly in the low-speed operating range, and the other on-off valve 12 (hereinafter referred to as the "second on-off valve")
) 12 is set to have a negative opening pressure higher than that of the first on-off valve 11 so that it opens and closes in a somewhat high-speed operating range. Roughly speaking, in this embodiment, the opening areas of the opening/closing valves 11 and 12 are made different, and the opening area of the second opening/closing valve 12 is made larger than that of the first opening/closing valve 11.

On the other hand, for the intake throttle valve 13, as shown in FIG. 28
A driving means including a switching valve 29 and the like is provided, and this driving means closes the intake throttle valve 13 and enables the on-off valves 11 and 12, and opens the intake throttle valve 13 and operates the main intake passage 9a. @By opening the on-off valve 11
．． The intake system can be switched between a state in which 12 operating functions are stopped. In addition, a control circuit 30 using a microcomputer that receives signals from detecting means (not shown) for detecting engine speed, load, etc. opens and closes the engine during starting operation and during normal operation in an operating range that extends to a certain level of high operation. The above drive is configured so that the valves 11 and 12 are enabled to operate, and the operating function of the on-off valves 11 and 12 is stopped in a high-speed, high-load operation region where there is no need to completely compress the intake air. Means are controlled.

According to the intake system configured in this way, the intake throttle valve 1
3, when the main intake passage 9a is closed, the cylinder 1 is closed as the piston 2 descends during the intake stroke.
11 in relation to the engine speed depending on the negative pressure generated within the engine.
Only one or both on-off valves 11,12 are opened. As a result, the intake air is rapidly introduced into the combustion chamber 3 through the sub-intake passage 9b during the intake stroke, and the intake air is definitely compressed.

In this case, the functions of the two on-off valves 11 and 12 depending on the engine speed will be described in detail later, and first the basic effect of absolute compression will be explained with reference to FIG. This diagram shows the exhaust gas from each cylinder in a four-cylinder engine when the main intake passage 9a is opened and the operation of the on-off valves is stopped, to the state where at least one on-off valve is activated. It shows data when gas temperature was measured, and lines T1 to T4 show changes in exhaust gas temperature of each cylinder. As can be seen from this figure, when switching from a state in which the operating function of the on-off valve is stopped to a state in which the on-off valve is activated, combustibility is improved due to the compression effect of the intake air, so the exhaust gas from each cylinder The gas temperature increases,
In particular, the exhaust gas temperature (line T4) of the cylinder in which the combustion condition was extremely poor increases significantly because the unburned gas remaining in the combustion chamber is combusted. This effect can be obtained if the intake air is compressed properly through the operation of the on-off valve, but as mentioned above, it is difficult to ensure proper compression over a wide range of times with a single on-off valve. (See Figure 9).

Next, the operation according to the engine speed of the present embodiment device using two on-off valves 11 and 12 with different opening negative pressures will be explained with reference to FIGS. 4 and 5.

The negative pressure generated in the cylinder 1 during the intake stroke with the intake throttle valve 13 closed is as shown in Figure 4 (a) at low rotation speeds such as during cranking, and as shown in Figure 4 (a) at relatively high speeds. b)

As shown in these figures, cylinder 1 starts from the beginning of the intake stroke.
The internal pressure decreases (negative pressure increases), but at low rotation speeds when the descending speed of the piston 2 is slow, a large amount of leak intake air flows into the cylinder 1 from around the piston 2, etc., which causes leakage to occur inside the cylinder 1. The negative pressure generated will be smaller than when the pressure is high. At this time as well, the negative pressure inside the cylinder 1 reaches the valve opening negative pressure P1 of the first on-off valve 11, which has been set relatively small in advance, and this causes the first on-off valve 11 to close during the intake stroke (time 1
1), the intake air is introduced into the cylinder 1 through the first on-off valve 11. At low speeds, even if the first on-off valve 11, which has a relatively small opening area, is opened, the negative pressure is reduced, and the C cylinder 1 is filled with intake air, and during this period, the intake air is definitely compressed. Also, at this time, if intake air is introduced too rapidly, BD at the end of the intake stroke
Before time C, the negative pressure decreases and the first on-off valve 11 is closed, and after the valve is closed, negative pressure occurs again, but the first on-off valve 1
By appropriately setting the area of the opening 1, such a situation can be prevented, and the compression effect and intake air filling amount can definitely be ensured.

On the other hand, when the rotation speed is relatively high, the negative pressure generated in the cylinder 1 becomes large, and the piston 2 in particular descends rapidly. The negative pressure gradually increases and reaches the opening negative pressure P2 of the second on-off valve 12, and the second on-off valve 12 also opens (time t2). After that, as intake air is introduced multiple times through both on-off valves 11 and 12, the negative pressure inside the cylinder 1 decreases and the charging IMf
fl is secured, and a significant compression effect can be obtained.

Due to this operation, the relationship between the engine speed and the intake air intake per unit time becomes as shown by the solid line in FIG. As the engine speed shifts to the high speed range N2 where .12 is activated, the amount of intake air increases sufficiently to ensure the required amount of intake air filling. Also, the relationship between engine speed and average cylinder temperature is the sixth
As shown by the solid line C in the figure, the intake air temperature is increased from the low rotation range N1 to the high rotation range N2 compared to the case where the gl11111 valve is not used (broken line B).

FIG. 7 shows a second embodiment of the invention. In this embodiment, each cylinder 1 is provided with a main intake passage 9a and two auxiliary intake passages 9G and 9d whose downstream ends face each other and open into the main intake passage 9a. A first on-off valve 31 and a second on-off valve 32 are provided, respectively. Each of the on-off valves 31 and 32 is of WTI construction similar to the on-off valves 11 and 12 of the first embodiment.
1 has a relatively small opening negative pressure and a small opening area.
The second on-off valve 32 has a larger opening negative pressure and a considerably larger opening area than the first on-off valve 31. Further, an intake throttle valve 33 is arranged in the main intake passage 9a at a position where the downstream ends of both the sub-intake passages 9-c and 9d face each other.

This intake throttle valve 33 is operated by a driving means and a control means (not shown) to shut off the main intake passage 9a and the auxiliary intake passage 9d on the second n-th closing valve 32 side with respect to the combustion chamber 3 in the low rotation range.
It is operated to the position where the a1 intake passage 9C on the on-off valve 31 side is opened (double-dashed line A), and in a relatively high rotation range, the main intake passage 9a and the auxiliary intake passage 9C on the first on-off valve 31 side are opened with respect to the combustion chamber 3.
@ - It is operated to the position (double-dashed line opening) where the auxiliary intake passage 9d on the second on-off valve 32 side is opened by shutting off, and the main intake passage 9a is opened in the high rotation and high load range where there is no need to completely compress the intake air. It is operated to the neutral position (solid line c) where it opens.

According to this structure, in the low rotation range, the intake throttle valve 33 is placed in the position indicated by the two-dot chain line A, so that the negative pressure in the cylinder 1 is reduced to the first opening/closing valve 31, as shown in FIG. 8(a). When the valve-opening negative pressure P1 is reached, the first on-off valve 31 is opened and intake air is introduced from the auxiliary intake passage 9C, and in a relatively high rotation range, the intake throttle valve 33 is at the position indicated by the chain double-dashed line. As a result, as shown in FIG. 8(b), when the negative pressure in the cylinder 1 reaches the opening negative pressure P2 of the second on-off valve 32, the second on-off valve 32 is opened and the sub-intake is opened. Intake air is introduced from the passage 9d.

In this case as well, since the opening negative pressure and opening area of both the on-off valves 31 and 32 are different, each on-off valve 31 and 32 operates properly depending on the low rotation range and the relatively high rotation range. A compression effect is obtained and the intake air filling amount is also secured.

In each of the above embodiments, the intake passage for each cylinder is divided into the main intake passage and the auxiliary intake passage, and two on-off valves are provided in the auxiliary intake passage. A passage may be provided and both on-off valves may be arranged side by side in this intake passage. In this case, when there is no need to absolutely compress the intake air, both on-off valves may be moved to a position where they are evacuated from the intake passage. All you have to do is make it possible.

Further, in the above embodiment, two on-off valves are provided, but three or more on-off valves each having a different opening negative pressure may be arranged in parallel in the intake passage.

(Effects of the Invention) As described above, in the present invention, since a plurality of 1111Il valves each consisting of negative pressure responsive valves with different valve opening negative pressures are arranged in parallel in the intake passage, when the valve opening negative pressure is increased, the opening/closing valve is This ranges from low rotation speeds such as during cranking, where the valve does not operate, to relatively high rotation speeds, where it is desirable to increase the opening negative pressure of the opening/closing valve. It can be effective. This improves startability and eliminates white smoke and ignition over a wide rotation speed range during normal operation.
This low frequency range can be achieved with a simple structure using a plurality of on-off valves.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a first embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view of an on-off valve consisting of a negative pressure responsive valve, and Fig. 3 shows when the on-off valve is switched from a stopped state to an operating state. Graph showing changes in exhaust gas temperature of each cylinder, Figure 4 (a) (
b) is an explanatory diagram showing the change in cylinder internal pressure during the intake stroke at low and high revolutions when using the device of the first embodiment, and Fig. 5 shows the engine speed and intake when using the same device. Figure 6 is an explanatory diagram of the relationship between the engine speed and average cylinder temperature, Figure 7 is a schematic diagram showing the second embodiment, and Figure 8 is based on the device of the second embodiment. Figure 9 is an explanatory diagram showing the change in cylinder pressure during the intake stroke at low and high revolutions in the case of a conventional Diegel engine using the intake system and one on-off valve. It is a graph which shows the measurement result which investigated the relationship between engine rotation speed and the average temperature in a cylinder in the case of a conventional device. 1... Cylinder 1.9... Intake passage, 11.31.
...First on-off valve, 12.32...Second on-off valve. Patent applicant Mazda Corporation No. 1
Fig. 2 Fig. 3 Fig. 4 (a) (ky) Fig. 5 Engine private administration Fig. 6 Shienji'ycr whale Fig. 7 DeC Fig. 8 (ko) (death) Fig. 9

Claims (1)

[Claims] 1. An on-off valve is provided in the intake passage for each cylinder of the engine, and this on-off valve is configured with a negative pressure responsive valve that opens when the negative pressure in the cylinder reaches the valve opening negative pressure. In the intake system of a diesel engine, the intake air is restricted from being introduced into the combustion chamber until the middle of the intake stroke by the operation of the valve, and the intake air is rapidly introduced into the combustion chamber from the middle of the intake stroke to perform compression. An intake system for a diesel engine, characterized in that a plurality of on-off valves are arranged in parallel in the intake passage, and the opening negative pressure of each on-off valve is set to a different value.