JPS623126A - Air intake device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent a torque shock and smoke occurrence for an engine wherein an open/close valve is provided at an air intake passage for limiting the introduction of suction air into a combustion chamber until the half-way of a suction stroke, by controlling said valve in different states at steady and transient conditions. CONSTITUTION:In an engine wherein a limiting device for introducing suction air is provided at an air intake passage 8 for limiting an air flow into a combustion chamber 3 until the half-way of a suction stroke and causing the sudden introduction of air into said chamber 3 in the course of a suction stroke for adiabatic compression through the operation of an open/close valve 10, it is made possible to change over the open/close valve 10 by the actuating device 11 thereof as controlled through a control means 25, so that said valve 10 will be in a working condition and a stop condition wherein operation stops and the air intake passage 8 is open throughout a suction stroke. And the control means 25 is so regulated and constituted that said valve 10 can be gradually changed over to a working condition at a steady state wherein a load fluctuation is small, and quickly to a stop condition at a transient state wherein a load fluctuation is large.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an intake device for a diesel engine that increases the temperature of intake air through adiabatic 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 ignitability at the time of starting a diesel engine, the intake air supplied to the combustion chamber is adiabatically compressed to increase the intake air temperature. Intake devices (starting promotion devices) are 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. , warm-up from start-up
During low-load operating conditions up to 1000 hrs, while the main intake passage is throttled by the intake throttle valve, the opening m valve is operated to open in the middle of the intake stroke using a valve operating mechanism or a pressure-responsive opening/closing valve. By operating this on-off valve, the introduction of intake air into the combustion chamber is restricted until the middle of the intake stroke, and then the intake air is rapidly introduced into the combustion chamber from the middle of the intake stroke to perform adiabatic 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 the intake air temperature can be efficiently raised within the combustion chamber. In addition, in the above-mentioned conventional device, the 1711m valve is operated during startup and warm-up operation, but if the on-off valve is operated during operating conditions and temperature conditions where poor combustion is likely to occur even during normal operation, the intake air The increase in temperature improves combustibility and prevents the generation of white smoke, HC, etc.

By the way, in such an intake system, when intake air introduction is restricted by the operation of the on-off valve and it becomes difficult to secure the necessary filling amount (for example, during high-speed, high-load operation), the operation function of the on-off valve is disabled. The operation function is stopped and the intake passage is opened throughout the entire intake stroke. Conventionally, switching between the operating state and the non-operational state of the on-off valve was performed simply at a constant speed. However, during steady-state conditions with small load fluctuations, especially if the on-off valve is suddenly switched to an operating state, the combustibility is increased and the engine speed fluctuates rapidly, causing torque shock. During large transients, especially if the on-off valve is not quickly switched to the state where the operation function is stopped, the intake air volume is temporarily insufficient and smoke is likely to occur. Conventionally, these problems cannot be solved at the same time. was difficult.

(Object of the Invention) In view of the above circumstances, the present invention appropriately switches the operating state and the operating function stopped state of the on-off valve depending on the steady state and the transient state, and reduces the torque at the time of switching in the steady state. To provide an intake system for a diesel engine that can secure a necessary filling amount even during transient periods while reducing shock.

(Structure of the Invention) The present invention provides an on-off valve in the intake passage of each cylinder, keeps this on-off valve in a closed state until the middle of the intake stroke, and restricts the introduction of intake air into the combustion chamber. In a diesel engine intake system that rapidly introduces intake air into the combustion chamber and performs adiabatic compression by opening the valve, the operating state and function of the on-off valve are stopped and the intake passage is closed throughout the intake stroke. a drive means capable of switching between an operating state in which the valve is opened for a period of time, a load detecting means for detecting the load on the engine, and a switching means for controlling switching between the operating state and the operating state of the on-off valve by the driving means, and ,
The control means is provided with a control means that slowly switches to the operating state during steady state with small load fluctuations, and rapidly switches to at least the operating function stop state during transient periods of large load fluctuations.

With this configuration, sudden fluctuations in engine speed are suppressed when the on-off valve switches from an inoperative state to an operating state in steady state, and on the other hand, during transient times, the on-off valve changes from an operating state to an inactive state. When switching, the filling amount is ensured with good responsiveness.

(Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention. In the figure, 1 is a cylinder that constitutes each cylinder of a diesel engine, and a combustion chamber 3 is formed above a piston 2 inside the cylinder.
An intake boat 5 with an exhaust valve 6 and an exhaust boat 7 with an exhaust valve 6 are open.

An intake passage 8 is communicated with the intake boat 5, and an exhaust passage 9 is communicated with the exhaust boat 7. and,
The intake passage 8 has an on-off valve 10 that restricts the introduction of intake air into the combustion chamber 3 until the middle of the intake stroke, and then suddenly introduces intake air into the combustion chamber 3 from the middle of the intake stroke to perform adiabatic compression. equipment is provided.

In this embodiment, this intake air introduction regulating device is a rotary valve type on-off valve that opens in the middle of the intake stroke in conjunction with the engine output shaft. It is designed to be driven. By incorporating an opening/closing timing variable means into this opening/closing valve drive device 11, which can change the opening/closing timing so that the opening/closing valve 10 is open during the entire period of the intake stroke, the operating function of the opening/closing valve 10 is substantially stopped. It is now possible to do so.

That is, as shown in FIG. 2, the on-off valve drive device 11 includes a drive shaft 12 connected to an engine output shaft (crankshaft), and a valve drive shaft 15 connected to this via a gear 13, 14. , a valve shaft 18, and a variable opening/closing timing means consisting of a pair of helical splines 17.18 and an adjustment member 19 that engages with these is incorporated between the valve drive shaft 15 and the valve shaft 16. The movement allows the on-off valve 10 to be switched between an operating state and a non-operating state. And the adjustment member 1
9 is provided with an actuator 20 such as a diaphragm device, a vacuum pump 21 for operating the actuator, a passage 22, and a control valve 23 whose duty ratio can be controlled. The adjusting member 19 can be moved and its moving speed can be controlled.

25 is a control means (CP) consisting of a microcomputer, etc.
U) receives a control lever opening signal 26 corresponding to the engine load, an engine speed signal 27, and an engine cooling water temperature signal 28, and controls the opening/closing valve drive device 11 according to the operating state and temperature state of the engine. By outputting a control signal to the control valve 23 of the timing variable means, the on-off valve 10 is switched between an operating state and a non-operating state in which it is opened for the entire period of the intake stroke. In other words, this control means 25 sets the operating range of the on-off valve 10 in advance, for example, on the relatively low rotation and low load side, keeps the on-off valve 10 in the operating state in this range regardless of the cooling water temperature, and also sets the on-off valve 10 in the operating state at low temperatures. A correction area is set to expand the operating rotation range, and in this correction area, the on-off valve 10 is operated only when the cooling water temperature is below a predetermined value, and in other operating conditions or temperature conditions, the on-off valve 10 is operated.
The operation function is stopped.

Further, the control means 25 controls the duty ratio of the control valve 23 to control the moving speed of the adjustment member 19, thereby changing the speed at which the on-off valve 10 is switched between the operating state and the operating function stopped state in response to load fluctuations. The control is performed so that at least the switching to the operating state is performed slowly during a steady state with small load fluctuations, and at least the switching to the operating function stop state is performed rapidly during transient times when the load fluctuations are large.

Note that 29 is a fuel injection pump, and 29' is a fuel injection valve.

A specific example of control by the control means 25 will be explained with reference to the flowchart of FIG.

In this flowchart, the engine speed and load are detected in steps S1 and S2, and based on these detection signals, it is checked in step S3 whether or not the operating state is in the operating range of the on-off valve 10. If so, it is checked in step S4 whether or not it is in the correction area. If it is in the correction area, the cooling water temperature is detected in step S5, and it is checked in step S6 whether or not the cooling water temperature is a predetermined water temperature. These are processes for detecting and determining operating conditions and temperature conditions.

When the operating state is in the operating range of the on-off valve 10 (when the determination result in step S3 is YES), the acceleration is detected by checking the load fluctuation in step S7, and it is checked in step S8 whether or not acceleration is occurring. It's true. And this step S
When the judgment result in step S9 is NO, that is, in a steady state with small load fluctuations, and when the operating state and temperature state are such that the on-off valve 10 should be operated, the on-off valve 10 is activated in step S9. Gradually switch to the operating state (II adjustment member 19
The actuator 20 is controlled via the control valve 23 so as to gradually move the motor.

Also, when the water temperature exceeds the specified value even if it is within the correction area (
When the determination result in step S6 is No), load fluctuation is detected in step S1o, and step ・S1
1 to check whether it is a transient period with large load fluctuations.

If it is not a transient state, the on-off valve 10 is gradually switched to a non-operational state in step 812, and if it is a transient state, the on-off valve 10 is immediately switched to a non-operational state in step 813 (the adjustment member 19 is rapidly moved). The actuator 20 is controlled via the control valve 23 so that the

On the other hand, when it is determined in step S8 that the current state is accelerating, or when it is determined in step S4 that it is not in the correction region, the process moves to step 813, and the open m-valve 10 is immediately switched to the operational disabled state.

In the intake system as described above, when operating conditions or temperature conditions are such that combustion defects are inherently likely to occur, such as low rotation and low load, the on-off valve 10 is opened and closed in the middle of the intake stroke. As a result, intake air is rapidly introduced into the combustion chamber 3 during the intake stroke, and adiabatic compression of the intake air is performed, thereby increasing the intake air temperature and improving combustibility. In addition, at high speeds and high loads, the operating function of the on-off valve 10 is substantially stopped and the intake passage 8 is opened for the entire period of the intake stroke, which means that the restriction on intake air introduction is lifted and the required intake air filling amount is is ensured.

In particular, in the present invention, when the on-off valve 10 switches from the operating state to the operating state in response to changes in the operating state or temperature state during steady state with small load fluctuations, this switching is performed gradually. As the combustibility increases, the engine speed also increases gradually. Therefore, the engine speed is prevented from rapidly changing due to relatively small load changes during steady state.

On the other hand, during a transient period such as during acceleration where the load fluctuation is large, the on-off valve 10 is immediately switched from the operating state to the non-operational state, so that the necessary filling amount is ensured with good responsiveness. In other words, during the above-mentioned transient period, if the switching to the operational function stop state is delayed in response to the increase in fuel, a temporary air intake shortage will occur, which will impede the improvement in output, and
Since black smoke is likely to be generated, such a situation is prevented by rapidly performing the above switching.

Another embodiment of the on-off valve and on-off valve driving device according to the present invention will be described with reference to FIGS. 4 and 5. FIG.

As the on-off valve 10' in this embodiment, this on-off valve 1
An automatic valve type is used that automatically opens and closes when the negative pressure in the intake passage downstream of 0' becomes larger than a predetermined value, and the intake passage has a main intake passage 8a and an auxiliary intake passage 8b. A control means 25 is provided in the main intake passage 8a.
The auxiliary intake passage 8b is opened downstream of the intake throttle valve 30, and the automatic valve 30 is provided in the auxiliary intake passage 8b. A type of on-off valve 10' is provided. Further, as a means for rotating the intake throttle valve 30, an actuator 3 such as a diaphragm device is used.
1, a passage 32 for operating this, and a vacuum pump 33
A driving device including a control valve 34 and the like is provided.

The control valve 34 is controlled by the control means 25 so that the intake throttle valve 30 is opened when negative pressure is introduced from the vacuum pump 33 to the actuator 31 through the passage 32.

As shown in an enlarged view in FIG. 5, the on-off valve 10' includes a valve body 42 provided in a valve chamber 40 and abutting a valve seat 41 from the upstream side, and a valve body 42 connected to the valve body 42 via a connecting shaft 43. It consists of a connected diaphragm 44, two chambers 45 and 46 partitioned by the diaphragm 44, and a return spring 47 that biases the valve body 42 provided in one of the chambers 45 in the valve closing direction. The one chamber 45 is connected to the sub-intake passage 8b downstream of the valve body 42 via a communication hole 48 passing through the valve body 42, the connecting shaft 43, and the diaphragm 44.
The other chamber 46 communicates through an opening 49 with the upstream side of the sub-intake passage 8b, that is, a surge tank (not shown), and is maintained at approximately atmospheric pressure.

Therefore, the negative pressure in the auxiliary intake passage 8b downstream of the on-off valve 10' is transmitted to the chamber 45 via the communication hole 48, and when this negative pressure is below a certain value, the return ring 47 moves the valve body 42 in the valve closing direction. I am energized by □, but
When the negative pressure increases beyond a certain value, the valve body 42 resists the biasing force of the return spring 47 via the diaphragm 44.
Now the valve can be opened ゛・.

It's on.

In addition, for the above-mentioned open m valve 10', a return
□A movable spring support plate 50 that supports the spring support plate 50, an actuator 51 that operates this spring support plate 50, a passage 52 that operates this actuator 51, a vacuum pump 33, and a control valve 53 control the on-off valve 10'. A valve-opening negative pressure adjusting means is configured to adjust the valve-opening negative pressure.

With this configuration, when the main intake passage 8a is throttled by the intake throttle valve 30, the on-off valve 10' changes from the closed state to the open state during the intake stroke when the negative pressure in the cylinder 1 reaches the valve opening negative pressure. When the intake throttle valve 30 is opened, intake air is introduced from the main intake passage 8a and the opening/closing valve 10 is opened.
’ operating function stops. Then, by opening and closing the intake throttle valve 30 via the drive device in response to a signal from the control means 25, the on-off valve 10' is switched between an operating state and a non-operating state, and when it is switched to an operating state in a normal state, , while the intake throttle valve 30 is gradually closed,
By controlling the opening negative pressure of the on-off valve 10' to gradually change from a small value to a normal value, the switching to the operating state is performed gradually. In addition, during a transient state, the on-off valve 10' is rapidly opened, thereby rapidly switching to a state in which the operating function is stopped. Even in this case, the same effect as in the above embodiment can be obtained.

In addition to these embodiments, for example, an intake passage having the same intake passage configuration as shown in FIG. It is also possible to adopt a device that controls the opening and closing of the intake throttle valve and its opening and closing speed.

(Effects of the Invention) As described above, the present invention aims to improve combustibility by adiabatic compression of intake air by operating the on-off valve when necessary depending on the operating state, etc., and also enables the on-off valve to operate during steady state with small load fluctuations. During steady-state operation, the RrM valve is switched slowly to the RrM valve, and during transient periods with large load fluctuations, the RrM valve's operation function is stopped rapidly. This ensures the necessary intake air filling amount during transient periods and prevents the generation of black smoke.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an intake system for a diesel engine according to an embodiment of the present invention, FIG. 2 is a configuration diagram of essential parts showing an example of an integral part of an on-off valve driving means in the same device, and FIG. A control flowchart, FIG. 4 is a cross-sectional view of main parts showing another embodiment of the on-off valve and drive means in the intake system, and FIG. 5 is a cross-sectional view of the on-off valve. 8...Intake passage, 10.10'...Opening/closing valve, 11
... Opening/closing valve drive device, 25... Control means, 26...
・Control lever opening signal (load detection means). Patent Applicant Mazda Co., Ltd. Agent Patent Attorney Etsushi Kotani Patent Attorney Chief 1) Masayuki Patent Attorney Yasuo Itaya No. 1 Figure No. 2 @ No. 4rg! J

Claims (1)

[Claims] 1. An on-off valve is provided in the intake passage for each cylinder, and this on-off valve is kept closed until the middle of the intake stroke to restrict the introduction of intake air into the combustion chamber, and by changing from the closed state to the flat state midway through the intake stroke, In a diesel engine intake system that introduces intake air into the combustion chamber and performs adiabatic compression,
a driving means capable of switching between an operating state of the on-off valve and an operating function stopped state in which the operating function is stopped and the intake passage is opened for the entire intake stroke; a load detecting means for detecting engine load; and the driving means. control the switching between the operating state and the operating function disabled state of the on-off valve, and at least gradually switch to the above operating state during steady state with small load fluctuations, and at least switch to the above operating function disabled state during transient periods with large load fluctuations. An intake system for a diesel engine, characterized in that it is provided with a control means for rapidly switching.