JPS627926A - Intake device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent starting malfunction of an engine on account of freezing of a valve and so on, by opening a closing valve in case of low temperature starting of the engine, which carries out an adiabatically compressing air intake by means of a valve to be quickly released in case of prescribed negative pressure inside of an intake pipe due to be provided at a downstream portion of an intake passage having the closing valve. CONSTITUTION:An intake passage (b) which takes in air through a valve 10 is opened at a downstream portion of an intake passage 6a having a closing valve 7. In case that the closing valve 7 is closed, and when negative pressure of the intake air caused by a descent of a piston2 exceeds a prescribed value, the valve 10 is quickly released to take in air so that charging efficiency is enhanced by its adiabatic compression. When an engine is going to start under cold condition, the valve 10 can't sometimes work on account of freezing, and air intake can't be carried out. Therefore, a control circuit 25 releases the closing valve 7 in such a situation.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an intake system for a fusel engine, which increases the intake air temperature by adiabatic compression in order to promote starting of a diesel engine and improve emissions. It is something that can be done.

(prior art).

Conventionally, as shown in Japanese Utility Model Application Publication No. 59-107936, in order to improve ignitability at the time of starting a diesel engine, there has been an intake system that adiabatically compresses the intake air supplied to the combustion chamber to avoid an increase in intake thirst. A starting acceleration device) is known. This device has an on-off valve in the intake passage that opens during the intake stroke. Specifically, an intake throttle valve is provided in the main intake passage, and an on-off valve is provided in the bypass intake passage that bypasses the intake throttle valve. During low-load operating conditions from startup to warm-up, with the main intake passage throttled by the intake throttle valve, the on-off valve is operated by a valve mechanism or pressure-responsive on-off valve during the intake stroke. By operating the on-off valve in this way, the introduction of intake air into the combustion chamber is limited until the middle of the intake stroke, and the intake air is rapidly introduced into the combustion chamber from the middle of the intake stroke. According to this device, compared to heating the intake air with a heater,
A large amount of energy is consumed as electricity <r
In addition, the intake air temperature can be increased efficiently within the combustion chamber. In addition, in the conventional device described above, the on-off valve is operated during startup and warm-up operation, but if the on-off valve is operated during normal operation, for example, in the relatively low rotation and low load operating range, the suction If J: is placed on the upper back of the temperature stone, the combustibility will be improved and the generation of white smoke, IC, etc. will be prevented.

In addition, in this device, the on-off valve that opens during the intake stroke may be driven by the engine output shaft via a valve mechanism or interlocking mechanism, or it may be automatically opened when the negative pressure in the cylinder reaches a predetermined negative pressure. A pressure-responsive type that opens automatically can be used, but if a pressure-responsive type is used in particular, adiabatic compression of intake air can be performed with a simple structure without the need for a valve mechanism or interlocking mechanism. can.

By the way, when using such a pressure-responsive on-off valve, if the engine is started when the outside temperature is low and the on-off valve is frozen, the engine speed will decrease by -1-9.
? The release may be delayed and require a long time to crank or may be difficult to start.

In other words, even if an attempt is made to automatically operate the on-off valve by blocking the inflow of intake air from sources other than the on-off valve at startup, negative pressure is generated in the cylinder during the initial cranking period due to leakage from around the piston and the relationship with the intake member. Since the on-off valve is relatively small, if the on-off valve is frozen, it can only be opened 1'.

When the engine speed increases to a certain degree and the negative pressure inside the cylinder becomes large enough, the negative J- force causes the on-off valve to open against the sticking force caused by freezing, and the freeze is removed. However, until then, the on-off valve remains closed, so the filling amount decreases and pumping becomes noisy. This may cause a significant delay in the increase in engine speed during C-cranking.

(Purpose of the Invention) The present invention has been developed in view of the above circumstances, and is designed to reduce pumping loss at the initial stage of cranking and increase the engine speed even when the on-off valve is frozen. To provide an intake device for a diesel engine that can speed up the cranking process and prevent cranking failures and increases in cranking time.

(Structure of the Invention) The present invention provides a pressure-responsive on-off valve that opens when the negative pressure in the cylinder reaches a predetermined negative pressure in the intake passage of each cylinder of the engine, and operates the on-off valve. In a diesel engine intake system, the introduction of intake air into the combustion chamber is restricted until the middle of the intake stroke, and the intake air is rapidly introduced into the combustion chamber from the middle of the intake stroke to perform adiabatic compression. A control means is provided for stopping the operation of the on-off valve until a predetermined rotational speed is reached when the engine is started at low speed, and for introducing intake air downstream of the on-off valve.

In other words, when the engine starts, until the engine speed reaches a speed that allows the opening/closing valve to unfreeze, the intake air is introduced into the combustion chamber with the opening/closing valve stopped, thereby securing the charging amount and reducing the pumping [1st]. That's how it is.

(Example) 1 to 3 show one embodiment of the present invention.

In these figures, 1 is each cylinder of a diesel engine, and a combustion chamber 3 is located above a piston 2 inside the cylinder.
An intake boat 5 equipped with an intake valve 4 and an exhaust port (not shown) equipped with an exhaust valve are opened into the combustion chamber 3.

The intake passage 6 communicating with the intake boat 5 is connected to the combustion chamber 3 by a pressure-responsive on-off valve 10 until the middle of the intake stroke.
An intake air introduction regulating device is provided that restricts the introduction of intake air into the combustion chamber 3 and suddenly introduces the intake air into the combustion chamber 3 from the middle of the intake stroke to perform -C adiabatic compression.

In this embodiment, this intake air introduction regulating device is the main intake passage 6a.
and a sub-intake passage 6b whose downstream end opens into the main intake passage 6a.
Since (5) the intake passage 6 is formed separately for each cylinder 1,
In addition, an intake throttle valve 7 is provided upstream of the open position of the auxiliary intake passage 6b of the main intake passage 6a, and the auxiliary intake passage 6
b is provided with the on-off valve 10 described above.

The main intake passage 6a and the auxiliary intake passage 6b are each connected to an air cleaner (not shown) via a separate tank 8.9.

The on-off valve 10 is disposed at the opening to the auxiliary intake passage 6i) and the gauge tank 9, and includes a valve body 13 provided in the valve chamber 11 and abutting the valve seat 12 from the upstream side. A diaphragm 15 connected to the body 13 via a connecting shaft 14
and two chambers 1 separated by this diaphragm 15.
6.17 and the valve body 13 provided in the chamber 16 on one side.
and a return spring 18 that biases the valve in the valve closing direction. The one chamber 16 contains the valve body 13 and the connecting shaft 1.
4 and the auxiliary intake passage 6b downstream of the valve body 13 through a communication hole 19 penetrating the diamond noram 15, and the other chamber 17 communicates with the surge tank 9 and is maintained at approximately atmospheric pressure. When the negative pressure introduced from the valve body 13 into the one chamber 16 from the F-flow auxiliary intake passage 6b reaches a predetermined valve-opening negative pressure, the on-off valve 10 controls the biasing force of the return spring 18 and the valve. The valve body 13 is opened against the h pressure acting on the body 13 itself, and the main intake passage 6a is throttled by the -C intake throttle valve 7. During the intake stroke when the negative pressure reaches the above-mentioned valve opening negative pressure, the on-off valve 10 is automatically opened.Furthermore, when the intake throttle valve 7 is opened, intake air is introduced into the cylinder 1 from the 1-intake passage 6a. As a result, almost no negative pressure is generated downstream of the on-off valve 10, so the operation of the on-off valve 10 is stopped.

On the other hand, for the intake throttle valve 7, there is an actuator 21 formed by a diaphragm device that opens and closes the intake throttle valve 7, and a passage 22 for moving the actuator 21.
, a driving means composed of a vacuum pump 23 and a switching valve 24, and this driving means controls the intake throttle valve 7.
The intake system is divided into an on-off valve operating state in which the on-off valve 10 is operated by closing the on-off valve 10, and an inactive state in which the operating function of the intake throttle valve 7 is stopped by listening to the intake throttle valve 7 and opening the main intake passage 6a. It is possible to switch.

Reference numeral 25 denotes a control means consisting of a microphone [1 computer, etc., which receives signals for detecting the operating state from the rotational speed detecting means 26 and the direct direction detecting means 27, etc. When the on-off valve on the load side is in the operating range, the intake throttle valve 7 is closed and the on-off valve 10 is in the operating state, and in the operating range on the high-speed, high-load side where there is no need to perform adiabatic compression of intake air, the intake throttle valve 7 is opened. The driving means is controlled so that the on-off valve 10 is brought into a non-operating state.

Furthermore, during cranking when starting the engine, the control means 25 opens the intake throttle valve 7 and deactivates the on-off valve 10 until the engine speed reaches a predetermined number of rotations necessary for unfreezing the on-off valve 10. state, and after reaching a predetermined rotational speed, the intake throttle valve 7 is opened and the on-off valve 10 is activated.
: The sea urchin controls the above drive 1ift.

The operation of the intake device configured in this manner will be explained with reference to FIG. 4.

FIG. 4 shows temporal changes in the engine speed at startup (line B) and temporal changes in the state of the on-off valve 10 (line C) in response to the operation of the engine switch (line A). As shown in this figure, cranking is initiated by setting the engine switch to the star position (ST), and this cranking start point t
The engine speed gradually increases from o. In this case, if the on-off valve 10 is frozen, the on-off valve 10 will not be able to resist the sticking force due to freezing unless a negative pressure that is two times larger than the original opening pressure of the on-off valve 10 is generated in the cylinder 1. In this state, even if you close the intake throttle valve 7 at the beginning of cranking and try to operate the on-off valve 10 (double-dashed line C'), the piston 2 will not open while the engine speed is low. The amount of intake air leaking from around the piston 2 increases.As a result, the negative pressure generated in the cylinder 1 is relatively low, so the on-off valve 10 is not actually opened.Furthermore, the amount of intake air leaking from around the piston 2 is sufficient. Intake air cannot be filled into the cylinder 1 during this time, and a pumping loss occurs, causing a significant delay in the increase in engine speed (as shown by the two-dot chain line B').
).

In contrast, in the present invention, as shown by line C, the on-off valve 10 is turned OFF (operation stopped state) at the initial stage of cranking.In other words, by opening the intake throttle valve 7, intake air is directed into the cylinder 1 from the main intake passage 6a. Let it be introduced freelyC
As a result, the intake air is sufficiently filled into the cylinder 1, the pumping loss is reduced, and as shown by line B, the upper limit of the engine rotational speed is promoted.

When the engine speed reaches a predetermined speed No., the intake throttle valve 7 is closed and the C on-off valve 10 is turned on.
At this point, the number of revolutions is above 1292, so the negative pressure generated in the cylinder 1 becomes large, and this negative pressure causes the on-off valve 10 to resist the sticking force due to freezing, and the freezing is released. Therefore, after that, the on-off valve 10 automatically operates,
In other words, during the intake stroke when the negative pressure in the cylinder 1 reaches the opening Ω pressure of the on-off valve 10, the on-off valve 10 is turned off, and a large amount of intake air is suddenly introduced into the combustion chamber 3, thereby performing adiabatic compression of the intake air. This adiabatic compression improves ignition and combustibility, facilitating starting. Zarani T
Even after the engine is started, the on-off valve 10 is operated in a region of relatively low rotation and low load to perform adiabatic compression of the intake air, thereby preventing misfires and improving emissions.

41. In the above embodiment, the engine speed is simply checked during cranking, and the on-off valve 10 is stopped when the speed is below a predetermined speed. Only when the temperature is low enough to cause freezing, the on-off valve 10 may be brought into a non-operational state when the rotation speed is below a predetermined number.

In addition, in the embodiment described in -11, the intake passage 6 for each cylinder is divided into the main intake passage 6a and the auxiliary intake passage 6b, and the auxiliary intake passage 6b is provided with an on-off valve 10, but one for each cylinder. A pressure-responsive on-off valve 10 may be provided in each intake passage. In this case, for example, a bypass passage that bypasses the on-off valve 10 is provided so that a predetermined rotation speed is reached during cranking. Until then, it is sufficient to open this bypass passage to allow intake air to flow downstream of the on-off valve 10.Furthermore, the on-off valve 10 can be rotated to a position where it is retracted from the intake passage, and the on-off valve 10 can be turned into a non-operating state. 10 to the retracted position to open the intake passage.j: You may leave it as is.

(Effects of the Invention) As described above, the present invention provides an intake system for a diesel engine equipped with a pressure-responsive on-off valve that performs adiabatic compression of intake air by automatically opening and closing in response to changes in pressure within the cylinder. At least when starting when the outside air temperature is low, the operation of the on-off valve is stopped until a predetermined rotation speed is reached, and intake air is allowed to flow downstream of the on-off valve, so even if the on-off valve is frozen, cranking will continue. This reduces the initial pumping loss and enables good starting.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional side view of a device according to an embodiment of the present invention, Fig. 2 is a schematic cross-sectional plan view of this device, Fig. 3 is an enlarged sectional view of an on-off valve, and Fig. 4 is an engine rotation at engine startup. FIG. 3 is an explanatory diagram showing the number change and control of the on-off valve. 1... Cylinder, 3... Combustion chamber, 4... Intake valve,
6... Intake passage, 7... Intake throttle valve, 10... Opening/closing valve, 25... Control means. Figure 3 Figure 4

Claims (1)

[Claims] 1. A pressure-responsive on-off valve that opens when the negative pressure in the cylinder reaches a predetermined value is installed in the intake passage of each cylinder of the engine, and the operation of this on-off valve closes the combustion chamber until the middle of the intake stroke. In a diesel engine intake system that restricts the intake air into the combustion chamber and rapidly introduces the intake air into the combustion chamber from the middle of the intake stroke to perform adiabatic compression, the intake system operates at a predetermined rotational speed at least when starting the engine when the outside air temperature is low. An intake system for a diesel engine, characterized in that the intake system for a diesel engine is provided with a control means for stopping the operation of the on-off valve until reaching the above-mentioned on-off valve and introducing intake air downstream of the on-off valve.