JPH068607B2 - Intake device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intake system for a diesel engine in which an intake temperature is raised by adiabatic compression in order to accelerate start-up of the diesel engine and improve emission.

(Prior Art) Conventionally, as disclosed in Japanese Utility Model Laid-Open No. 59-107936, in order to improve the ignitability at the time of starting in a diesel engine, the intake air supplied to the combustion chamber is adiabatically compressed to raise the intake air temperature. An intake device (start promotion device) is known. This device is provided with an opening / closing valve that opens in the intake passage in the middle of the intake stroke, specifically, an intake throttle valve is provided in the main intake passage, and an opening / closing valve is provided in a bypass intake passage that bypasses the intake throttle valve. During a low load operation state from start-up to warm-up, the above-mentioned open / close valve is opened in the middle of the intake stroke by a valve mechanism or a pressure-responsive open / close valve with the main intake passage being throttled by the intake throttle valve. I am trying to make it work. By such operation of the on-off valve, introduction of intake air into the combustion chamber is restricted until the middle of the intake stroke, and intake air is rapidly introduced into the combustion chamber from the middle of the intake stroke to perform adiabatic compression. According to this device, much energy is not consumed as electric power as compared with the case where the intake air is heated by the air heater, and the intake air temperature can be efficiently raised in the combustion chamber. In the above-mentioned conventional device, the on-off valve is operated during the startup warm-up operation,
Even during normal operation, for example, by operating the on-off valve in an operation region where the rotation speed is relatively low and the load is low, the combustibility is improved due to the rise in intake air temperature and the generation of white smoke and HC is prevented.

The on-off valve that opens during the intake stroke in this device is one that is driven by the engine output shaft through a valve mechanism or an interlocking mechanism, or automatically when the negative pressure in the cylinder reaches a predetermined negative pressure. Although a pressure-responsive type that opens can be adopted, in particular, if a pressure-responsive type is used, it is possible to perform adiabatic compression of intake air with a simple structure without requiring a valve operating mechanism or an interlocking mechanism.

By the way, when such a pressure-responsive on-off valve is used, in the conventional device, the negative pressure in the cylinder is reduced to near atmospheric pressure after the on-off valve is simply opened at a preset valve opening negative pressure. Since it is only closed at this point, even if the valve opening negative pressure is set so that the on-off valve operates properly at a specific engine speed, if the engine speed becomes lower than this, As the time from the opening and closing operation of the on-off valve to the end of the intake stroke becomes longer, the negative pressure decreases before the end of the intake stroke and the on-off valve closes earlier. When the on-off valve closes early in this way, there is a problem in that the introduction of intake air is again hindered, the pressure in the cylinder decreases, and the filling amount and the adiabatic compression effect are reduced.

(Object of the Invention) In view of such circumstances, the present invention aims to improve combustibility and emission by adiabatic compression of intake air with a simple structure using a pressure-responsive on-off valve, and in particular, engine speed. (EN) Provided is an intake system for a diesel engine, which can secure a sufficient amount of intake air and can exhibit a good adiabatic compression effect even when the value is low.

(Structure of the Invention) The present invention is a pressure-responsive type that has a chamber for introducing a negative pressure in a cylinder in an intake passage for each cylinder of an engine and opens when the negative pressure reaches a predetermined negative pressure. An on-off valve is provided, and the operation of this on-off valve restricts the introduction of intake air into the combustion chamber until the middle of the intake stroke, and suddenly introduces intake air into the combustion chamber from the middle of the intake stroke to perform adiabatic compression. In the intake device, the open state of the on-off valve is maintained by blocking the release of negative pressure from the chamber at least until the end of the intake stroke after the on-off valve is opened.
The valve-opening state holding means for releasing negative pressure from the chamber after the end of the intake stroke is provided.

In other words, from the opening operation of the opening / closing valve in the middle of the intake stroke to at least the end of the intake stroke, the holding means keeps the open / closed valve open state even if the negative pressure in the cylinder decreases during that period. It is designed to be drooped.

(Embodiment) FIGS. 1 to 5 show an embodiment of the present invention. In these drawings, reference numeral 1 denotes each cylinder of a diesel engine, and a combustion chamber 3 is formed above the piston 2 inside the cylinder. The combustion chamber 3 has an intake port 5 equipped with an intake valve 4. , And an exhaust port (not shown) provided with an exhaust valve is open. Intake passage 6 communicating with the intake port 5
In addition, the pressure-responsive open / close valve 10 limits the introduction of intake air into the combustion chamber 3 until the middle of the intake stroke, and abruptly introduces intake air into the combustion chamber 3 from the middle of the intake stroke to perform adiabatic compression. A restraint device is provided. In this intake air introduction restricting device, in this embodiment, an intake passage 6 including a main intake passage 6a and a sub intake passage 6b having a downstream end opening to the main intake passage 6a is formed for each cylinder 1, and the main intake passage 6a is formed. 6
The intake throttle valve 7 is provided upstream of the opening position of the auxiliary intake passage 6b of the a, and the opening / closing valve 10 is provided in the auxiliary intake passage 6b.
Is provided. The main intake passage 6a and the sub intake passage 6b are connected to an air cleaner (not shown) via surge tanks 8 and 9, respectively.

The on-off valve 10 is arranged in the opening of the auxiliary intake passage 6b to the surge tank 9, and is provided in the valve chamber 11 and is in contact with the valve seat 12 from the upstream side.
A diaphragm 15 which is connected to the via a connecting shaft 14,
Two chambers 16 partitioned by this diaphragm 15,
17 and a return spring 18 that is provided in one of the chambers 16 and biases the valve body 13 in the valve closing direction. The one chamber 16 is communicated with the auxiliary intake passage 6b downstream of the valve body 13 through a communication hole 19 penetrating the valve body 13, the connecting shaft 14 and the diaphragm 15, and the negative pressure in the cylinder causes the negative pressure in the cylinder to be increased. It will be introduced via the downstream side of. The other chamber 17 communicates with the surge tank 9 and is maintained at about atmospheric pressure. Thus, the on-off valve 10
From the auxiliary intake passage 6b downstream of the valve body 13 to the one chamber 1
When the negative pressure introduced into 6 reaches a predetermined valve opening negative pressure, the valve element 13 is opened against the biasing force of the return spring 18 and the negative pressure acting on the valve element 13 itself. Therefore, in the state where the main intake passage 6a is throttled by the intake throttle valve 7, the opening / closing valve 10 is automatically opened during the intake stroke when the negative pressure in the cylinder 1 reaches the valve opening negative pressure. ing.

Further, for the on-off valve 10, there is provided an open-state holding means for holding the open state of the on-off valve 10 from the opening operation of the on-off valve 10 to at least the end of the intake stroke. The valve-opening state holding means prevents negative pressure from being released from the chamber at least until the end of the intake stroke after the opening / closing valve is opened, and releases negative pressure from the chamber after the end of the intake stroke. It was done. That is, as shown in FIGS. 3 to 5, the valve-opened state holding means has a check valve 21 arranged in the communication hole 19 of the opening / closing valve 10 and a communication passage 22 in one chamber 16 of the opening / closing valve 10. A negative pressure actuated control valve 23, which is connected via a valve and is capable of switching the one chamber 16 between a closed state and an open state to the atmosphere, and a spring 24 for urging the control valve 23 in the closing direction. It is composed of an operating negative pressure introducing passage 25 for introducing a negative pressure for operating the control valve 23 to the open state. Then, the operating negative pressure introducing passage 25 acts on the control valve 23 for the on-off valve 10 corresponding to a certain cylinder 1 by applying a negative pressure generated in the intake stroke from the side of another cylinder 1 whose intake stroke is different from that of the cylinder 1. For example, according to the ignition order, the first cylinder side is from the third cylinder side, the third cylinder side is from the fourth cylinder side, the fourth cylinder side is from the second cylinder side, and the second cylinder side is from the second cylinder side. It is arranged so that the negative pressure generated in the downstream of the on-off valve 10 from the first cylinder side acts on the control valve 23.

On the other hand, with respect to the intake throttle valve 7, an actuator 26 formed by a diaphragm device for opening and closing the intake throttle valve 7 is provided.
And the passage 2 for operating this actuator 26
7, a drive means composed of a vacuum pump 28 and a switching valve 29 is provided, and the intake throttle valve 7 is provided by this drive means.
The intake system can be switched between an on-off valve operating state in which the valve is closed to operate the on-off valve 10 and an operation stop state in which the operation function of the on-off valve 10 is stopped by opening the intake throttle valve 7 to open the main intake passage 6a. There is. Further, the rotation speed detection means 31
The control circuit 30 using a microcomputer or the like which receives signals from the load detection means 32 and the like causes the on-off valve to be in the operating state during the starting operation and in the relatively low rotation, low load side operation region to perform adiabatic compression of intake air. The driving means is controlled so as to be in the operation stop state in the operating region on the high rotation and high load side which does not need to be performed.

According to the intake device as described above, the opening / closing valve 10 operates in the state where the main intake passage 6a is throttled by the intake throttle valve 7 during the starting operation or in the operating region of relatively low rotation and low load, that is, the intake stroke. Intake of air into the combustion chamber 3 is limited until the middle of the period, and the negative pressure in the cylinder 1 gradually increases. When this negative pressure exceeds a predetermined value, the on-off valve 10 is opened and the auxiliary intake passage 6b releases the combustion chamber. A large amount of intake air is suddenly introduced into 3. As a result, adiabatic compression of the intake air is performed and the temperature in the combustion chamber 3 rises, so that ignitability and combustibility are enhanced, and white smoke, HC, etc. in the exhaust gas are reduced.

In particular, when the pressure-responsive on-off valve 10 is operated in this way, after the on-off valve 10 is opened during the intake stroke, the valve-opening state holding means ensures that the open state is maintained until the end of the intake stroke. To be kept. That is, according to the valve open state maintaining means having the structure shown in the figure, the negative pressure introduced into the one chamber 16 of the on-off valve 10 corresponding to the cylinder 1 reaches the valve opening negative pressure during the intake stroke of the cylinder 1. After the opening / closing valve 10 is opened by the check valve 21, the check valve 21 prevents the negative pressure from being released through the communication passage 22. Therefore, even if the negative pressure in the cylinder 1 becomes small, the control valve 23 Until the valve is opened, the negative pressure is contained in the one chamber 16 and the valve open state is maintained. After the end of the intake stroke of the cylinder 1, when the control valve 23 is opened by the negative pressure generated in the intake stroke of the other cylinder 1, the one chamber 16
Negative pressure is released from the inside and the on-off valve 10 is closed.

By the function of the valve open state maintaining means, the intake charge amount can be secured and the adiabatic compression effect can be exhibited well even at low rotation speed. This operation will be further described with reference to FIG. This figure shows the opening / closing operation of the opening / closing valve 10 and the pressure change in the cylinder 1 at the time of low rotation by the solid line A in the case of the device of the present invention provided with the above-mentioned valve open state maintaining means.
₁ and B ₁ , and two-dot chain lines A ₂ and B ₂ when the valve-opening state holding means is not provided (corresponding to the conventional device). In this figure, t ₁ is the opening operation timing of the on-off valve 10, and this timing t ₁ becomes a substantially constant crank angle, which is determined in advance by setting the valve opening negative pressure and the like.
In this case, the opening operation timing t ₁ is set in advance so that intake air can be sufficiently introduced after the opening operation of the opening / closing valve 10 even when the engine speed becomes high to some extent in the operating region where the opening / closing valve 10 should be operated. Need to be set. And this way, by opening operation time t ₁ is set, at the time of low rotation of engine starting secondary, opening operation timing of the opening and closing valve 10 t ₁
As the time from to the end of the intake stroke becomes longer, the adiabatic compression of the intake air (period T) ends considerably before the end of the intake stroke, and the negative pressure decreases.

Therefore, when the above-mentioned valve open state holding means is not provided, the on-off valve 10 closes early as indicated by the chain _double- dashed line A ₂ due to the decrease in the intake negative pressure, and thereafter, as shown by the chain _double- dashed line B ₂ , the inside of the cylinder 1 is closed. Since the pressure decreases again, the temperature decreases due to the adiabatic expansion of the intake air and the intake air charge decreases. On the other hand, according to the device of the present invention, which is provided with the valve open state holding means, the open state of the on-off valve 10 after the end of the intake stroke is obtained as shown by the solid line A ₁ , and therefore as shown by the solid line B _1. After the adiabatic compression of the intake air, the intake air is introduced to prevent the pressure in the cylinder 1 from decreasing, which ensures the filling amount and prevents the temperature from decreasing after the adiabatic compression.

In the above embodiment, the intake passage 6 for each cylinder is divided into the main intake passage 6a and the sub intake passage 6b, and the sub intake passage 6b is divided.
Although the on-off valve 10 is provided in each of the cylinders, one intake passage may be provided for each cylinder and the pressure-responsive on-off valve 10 may be provided in the intake passage. When the intake valve is rotatable to the retracted position and the operation is stopped, the on-off valve 10 may be rotated to the retracted position to open the intake passage. In this case as well, by providing the opening / closing valve 10 with the same valve opening state holding means as in the above-described embodiment, the same operation as in the above-described embodiment can be obtained.

(Effects of the Invention) As described above, according to the present invention, the adiabatic compression of intake air is performed with a simple structure by the pressure-responsive on-off valve that opens when the negative pressure in the cylinder reaches a predetermined negative pressure. Combustibility and emission can be improved. Moreover, in the present invention, in particular, since the opening state holding means for holding the opening state of the opening / closing valve is provided at least from the opening operation of the opening / closing valve to the end of the intake stroke, even at the time of low rotation such as engine start. It is possible to reliably prevent the on-off valve from being closed early, to secure the intake charge amount and to exhibit the adiabatic compression effect satisfactorily.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an apparatus according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional plan view of this apparatus, FIG. 3 is an enlarged sectional view of an on-off valve, and FIG. FIG. 5 is a schematic view of the constituent passage arrangement portion, FIG. 5 is an enlarged view of the control valve arrangement portion in the valve open state maintaining means, and FIG. 6 is an explanatory diagram showing the operation of the opening / closing valve and the pressure change in the cylinder. DESCRIPTION OF SYMBOLS 1 ... Cylinder, 3 ... Combustion chamber, 4 ... Intake valve, 6 ... Intake passage, 7 ... Intake throttle valve, 10 ... Open / close valve, 21-25 ... Open valve state maintaining means.

Claims (1)

[Claims] 1. A pressure-responsive on-off valve having a chamber for introducing a negative pressure in the cylinder in an intake passage for each cylinder of an engine and opening when the negative pressure reaches a predetermined negative pressure. In the intake system of a diesel engine, the intake valve is restricted from being introduced into the combustion chamber until the middle of the intake stroke by the operation of this on-off valve, and the intake is rapidly introduced into the combustion chamber from the middle of the intake stroke to perform adiabatic compression. , The open state of the on-off valve is maintained by blocking the release of negative pressure from the chamber at least until the end of the intake stroke after the on-off valve opens, and after the end of the intake stroke, the negative pressure is released from the chamber. An intake system for a diesel engine, characterized in that a valve open state maintaining means for releasing pressure is provided.