JPH068606B2 - Intake device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intake system in which an intake temperature is raised by adiabatic compression in order to accelerate starting of a 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.

By the way, in the above-mentioned conventional device, the opening / closing valve is operated only during the warming-up operation for starting the engine.However, even during the normal operation after the warming-up operation, the misfire or the poor combustion may occur depending on the operating conditions. In addition, white smoke and unburned HC and CO that are unburned components may be easily generated in the exhaust gas due to the above. Therefore, adiabatic compression by the operation of the on-off valve is used to raise the combustion temperature. This is effective in preventing misfire and reducing HC and the like in exhaust gas. It is desirable to operate the on-off valve over a relatively wide range of rotation speed, because there is a possibility of misfiring and poor combustion even at high engine speeds, especially at low temperatures and high altitudes where atmospheric pressure is low. . However, in this case, if the on-off valve is simply set to open at a substantially constant crank angle, the intake introduction time from the opening of the on-off valve to the closing of the intake valve changes depending on the engine speed. Even if the on-off valve functions properly in the rotational speed range, the adiabatic compression effect and the intake charge amount are likely to decrease in other rotational speed ranges.For example, when the engine speed increases, the intake air introduction time decreases. However, there was a problem that intake air could not be introduced sufficiently and the intake charge amount decreased.

(Object of the Invention) In view of such circumstances, the present invention provides a sufficient adiabatic compression effect of intake air from low rotation speed to high rotation speed while ensuring a sufficient intake air charge amount, and improves the ignitability and combustibility of the engine. It is intended to provide an intake system for a diesel engine, which can achieve the improvement of the exhaust gas and the improvement of the emission over a wide range of rotational speeds.

(Structure of the Invention) According to the present invention, an on-off valve is provided in the intake passage, the on-off valve is closed until the middle of the intake stroke to restrict the introduction of intake air into the combustion chamber, and the on-off valve is opened during the intake stroke. In the intake system of a diesel engine equipped with an intake induction control device that rapidly introduces intake air into the combustion chamber to perform adiabatic compression, a drive that varies the opening operation timing by the crank angle of the on-off valve in the intake induction control device Means and control means for controlling the drive means so as to advance the opening operation timing of the on-off valve as the engine speed increases.

With this configuration, the time from the opening operation timing of the on-off valve to the end of the intake stroke is appropriately adjusted over a wide range of rotation speeds so that the intake charge amount can be secured and the adiabatic compression effect can be satisfied. is there.

(Embodiment) FIGS. 1 to 3 show a first 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. In the intake passage 6 communicating with the intake port 5, the opening / closing valve 10 limits the introduction of intake air into the combustion chamber 3 until the middle of the intake stroke, and rapidly introduces the intake air into the combustion chamber 3 from the middle of the intake stroke to insulate the heat. An intake air introduction regulation device for performing compression is provided. In this embodiment, this intake air introduction control device has a main intake passage 6a and a downstream end of the main intake passage 6a.
An intake passage 6 composed of an auxiliary intake passage 6b opening to each of the cylinders 1 is formed for each cylinder 1, and an intake throttle valve 7 is provided upstream of the opening position of the auxiliary intake passage 6b of the main intake passage 6a. The automatic intake valve opening / closing valve 10 that opens in the middle of the intake stroke according to the pressure change when the main intake passage 6a is throttled is provided in the sub intake passage 6b. 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 which is provided in one of the chambers 16 and biases the valve element 13 in the valve opening direction. The one chamber 16 communicates 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 other chamber 1
7 communicates with the surge tank 9 and is maintained at substantially atmospheric pressure. According to this structure, when a negative pressure is generated in the auxiliary intake passage 6b downstream of the valve body 13, the negative pressure is applied to the one chamber 1
6 is introduced into the valve body 13 due to the pressure difference between the chambers 16 and 17.
The force in the opening direction acts on the diaphragm 15, while the pressure applied to the valve body 13 itself and the return spring 18
Is a resistance force, and when the valve body 13 is opened, the negative pressure acting on the valve body 13 itself becomes small. Therefore,
By setting the pressure receiving areas of the diaphragm 15 and the valve body 13 to appropriate levels and by making the spring force of the return spring 18 relatively small, combustion occurs when the main intake passage 6a is throttled by the intake throttle valve 7. The valve body 13 is opened in the middle of the intake stroke when the negative pressure generated in the chamber 3 and on the downstream side of the auxiliary intake passage 6b communicating therewith exceeds a predetermined value, and conversely, when the negative pressure becomes sufficiently small, the valve body 13 is opened. Is closed. On the other hand, when the intake throttle valve 7 is open, almost no intake negative pressure is generated, so the operation of the on-off valve 10 is stopped, that is, the closed state is maintained. The valve seat 12 is made of a damping steel plate or plastic, and the surge tank 9
If a sound absorbing material is attached to the inner surface of the, the noise during operation of the on-off valve 10 can be reduced.

The intake throttle valve 7 provided in the main intake passage 6 a is connected to the actuator 21. This actuator 2
1 is formed by, for example, a diaphragm device, and the passage 22
Is connected to the vacuum pump 23 via the
2 is provided with a control valve 24 for controlling the negative pressure introduction amount from the vacuum pump 23 to the actuator 21 by controlling the duty ratio or the like. The actuator 21, the passage 22, the vacuum pump 23, and the control valve 24 constitute a drive means for the intake air intake control device. This drive means enables opening / closing of the intake throttle valve 7 and adjustment of the opening degree thereof to operate and stop the open / close valve 10, and the intake throttle valve 7 allows the main intake passage 6 to operate.
It is possible to adjust the amount of intake leakage from the main intake passage 6a to the combustion chamber 3 when the on-off valve 10 is activated by narrowing a.
By adjusting the intake leak amount, the opening operation timing depending on the crank angle of the on-off valve 10 can be changed. That is, as will be described in detail later, the timing (crank angle) at which the negative pressure generated in the intake stroke reaches the opening pressure of the opening / closing valve 10 and the opening / closing valve 10 opens is changed according to the intake leak amount, and The opening operation timing of the on-off valve 10 advances as the amount decreases.

Reference numeral 25 denotes a control circuit (control means) for controlling the drive means, which is composed of a microcomputer or the like, and detects a load by a signal from a rotation speed detection means 26 provided in a fuel injection pump or the like and an accelerator opening degree or the like. Load detection means 2
The actuator 21 is controlled by receiving a signal from the control valve 7 and controlling the control valve 24. The control circuit 25 sets an operating region in which the on-off valve 10 should be operated in advance, and closes the intake throttle valve 7 to a small opening when the operating state detected by the engine speed and the load is in the operating region. The actuator 21 is controlled to operate the on-off valve 10, and in this case, the opening of the intake throttle valve 7 is controlled via the control valve 24 and the actuator 21 according to the engine speed detection signal. The intake leak amount is controlled so that the opening operation timing of the on-off valve 10 is advanced as the rotation speed increases. That is, when the engine speed is high, the angle of the intake throttle valve 7 is reduced to reduce the intake leak amount, and as the engine speed is decreased, the opening of the intake throttle valve 7 is gradually increased to increase the intake leak amount. Are controlled to increase. It should be noted that the operating region in which the on-off valve 10 should be operated requires improvement of ignitability and combustibility, and the on-off valve 10
Is set in a region where the on-off valve 10 can effectively function, for example, near the limit rotational speed of the opening / closing valve 10 from the starting operation region (at which the opening / closing valve 10 cannot correctly follow negative pressure fluctuations at higher rotation speeds). Is set to a relatively low load range (including the starting operation range) over a relatively wide rotation speed range up to. In addition, in order to reduce pumping loss and facilitate introduction of intake air in a region other than such an area, the intake throttle valve 7 is opened to open the main intake passage 6a to stop the operation function of the on-off valve 10. ing.

According to the intake device as described above, the open / close valve 10 opens in the middle of the intake stroke in the state where the main intake passage 6a is throttled by the intake throttle valve 7, that is, the combustion chamber 3 reaches the middle of the intake stroke.
The introduction of intake air into the combustion chamber 3 is restricted and the negative pressure in the combustion chamber 3 gradually increases. When this negative pressure exceeds a predetermined value, the on-off valve 1
When 0 is opened, a large amount of intake air is rapidly introduced into the combustion chamber 3 from the auxiliary intake passage 6b. As a result, the adiabatic compression of the intake air is performed, the temperature in the combustion chamber 3 rises, and the ignitability and combustibility are enhanced.

And in this case, the control circuit 2
5, the opening operation timing of the on-off valve 10 is properly controlled via the drive means. This action will be described below with reference to FIGS. 4 and 5.

FIG. 4 shows the pressure fluctuation in the combustion chamber 3 and the opening / closing valve 10 in the intake stroke in a state where the main intake passage 6a is throttled by the intake throttle valve 7 to operate the automatic valve type opening / closing valve 10. The opening operation timing is shown with the horizontal axis as the crank angle, the curve A is the pressure fluctuation when the intake leak amount flowing into the combustion chamber 3 through the main intake passage 6a is increased to some extent, and the curve B is the intake leak amount. It represents the pressure fluctuation when the pressure is reduced. As shown in this figure, the pressure in the combustion chamber 3 gradually decreases from the time of TDC, but if the intake leak amount is increased within a range in which the opening / closing valve 10 can be opened, the above pressure decrease becomes gentle. , The negative pressure is the valve opening pressure P of the on-off valve 10.
The opening operation timing Ta that reaches 0 is retarded, and the opening operation timing Tb is advanced by reducing the intake leak amount. Therefore, in the present embodiment, as described above, the intake leak amount is controlled by adjusting the opening degree of the intake throttle valve 7 so that the opening operation timing is advanced as the rotation speed increases.

When controlled in this way, the pressure fluctuation in the combustion chamber 3 with the horizontal axis as the time axis shows the solid lines A ₁ and B in FIG. 5 (a) and (b) at low rotation speed and high rotation speed, respectively. _As shown by ₁ , the opening operation timing T of the on-off valve 10 is
The time from a, Tb to the end of the intake stroke is properly maintained. That is, after the opening / closing valve 10 is opened in the intake stroke, intake air is introduced into the combustion chamber 3 from the auxiliary intake passage 6b, and the combustion chamber 3
When the negative pressure in the inside decreases and returns to near atmospheric pressure, the on-off valve 10 closes. However, if the opening operation timing of the on-off valve 10 is unnecessarily advanced at low rotation speed, 2 in Fig. 5 (a). As indicated by the dashed line A ', the on-off valve 10
Is closed too early, and then the pressure drops again and the filling amount decreases. Therefore, when the engine speed is low, the intake leak amount is increased to some extent and the opening operation timing Ta of the opening / closing valve 10 is appropriately delayed as shown by the solid line A ₁ , so that the closing operation timing of the opening / closing valve 10 substantially coincides with the end of the intake stroke. The filling amount is secured by this.

On the other hand, at high rotation speed, if the opening / closing valve 10 is opened at the same crank angle as the proper opening operation timing Ta at low rotation speed, the intake air introduction time from the opening operation timing Ta to the end of the intake stroke is at low rotation speed. Since it is shorter than that of Fig. 5,
As indicated by the chain double-dashed line B ′ in (b), the intake air introduction time has elapsed until the negative pressure becomes sufficiently small, and the intake air cannot be sufficiently introduced, and the filling amount and the adiabatic compression effect decrease. Therefore, the intake operation time is not shortened by advancing the opening operation timing Tb of the on-off valve 10 at the time of high rotation, which ensures the intake charge amount even at the time of high rotation and has the adiabatic compression effect. Is increased.

When the on-off valve 10 is in the operating state, small amount of air leaks from around the piston 2 and flows into the combustion chamber 3 until the on-off valve 10 opens during the intake stroke. Then, the intake leak amount in the intake throttle valve 7 is controlled while being sufficiently reduced, and in particular, when advancing the operation timing, the intake throttle valve 7 is brought into a substantially fully closed state to prevent leakage of intake air due to poor closing. There is a need. Therefore, for example, the valve shaft of the intake throttle valve 7 is offset from the center of the intake throttle valve 7, or the inner surface of the main intake passage 6a corresponding to the periphery of the intake throttle valve 7 is formed of a material having a high sealing property such as rubber. For example, it is preferable to prevent the closing failure and perform the leak control with high accuracy.

Further, the specific structure of the intake air introducing device and the driving device in the present invention is not limited to the above-mentioned embodiment, and various modifications can be made. Several examples will be described below.

In the second embodiment shown in FIGS. 6 and 7, the automatic valve type on-off valve 10 is provided in the main intake passage 6a, and the sub intake passage 6b is not provided. This on-off valve 10
The structure is similar to that of the first embodiment so that it opens and closes in response to changes in pressure, but its end is attached to the main intake passage 6a through the rotary shaft 10a, so that the main intake passage 6a is opened. The operating state in which the intake air intake is restricted and the recess 30 provided in the side wall of the main intake passage 6a.
Stored in the main air intake passage 6a and is rotatable to a stopped state in which the main intake passage 6a is opened. The on-off valve 10 is switched between an operating state and a stopped state according to the operating state by a drive unit for switching between operation and stop including an actuator 31 that rotates the on-off valve 10 via the rotary shaft 10a. It can be switched to. Further, a small-diameter leak passage 6c is provided between the main intake passage 6a between the upstream side and the downstream side of the on-off valve 10, and the leak passage 6c is provided with a check valve 32 and an opening / closing valve 10a. A leak control valve 33 using a linear solenoid valve or the like is provided as a drive unit that makes the operation time variable.

With this structure, when the on-off valve 10 is in an operating state, the opening operation timing of the on-off valve 10 is controlled by the control of the leak control valve 33 according to the engine speed by the control circuit 25, as in the case of the first embodiment. The intake leak amount may be controlled so as to be adjusted. That is, when the opening degree of the leak control valve 33 is increased, the amount of intake leak that flows into the combustion chamber 3 through the leak passage 6c increases, and the decrease in the pressure in the combustion chamber 3 during the intake stroke becomes gentle. As a result, the opening operation timing at which the negative pressure reaches the opening pressure of the on-off valve is delayed, and conversely, the leak control valve 33
When the opening degree of is decreased, the opening operation timing is advanced.
Therefore, the opening degree of the leak control valve 33 may be reduced as the engine speed increases. Further, in this structure, the check valve 32 provided in the leak passage 6c is provided with the intake valve 4 after the opening / closing valve 10 is operated from open to closed.
Before closing, the intake air is prevented from flowing back into the leak passage 6c, that is, a reduction in the filling rate due to the blowback of the intake air is prevented.

In both the first and second embodiments, the opening operation timing of the automatic valve type on-off valve 10 is controlled by controlling the intake leak amount, but the spring force of the return spring 18 in the on-off valve 10 is adjusted. The opening pressure of the on-off valve 10 may be made variable by making it possible, and the opening operation timing of the on-off valve 10 may be controlled by controlling this valve opening pressure.

8 and 9 show a third embodiment of the device of the present invention. In this embodiment, the main intake passage 6a is used as an intake introduction restricting device.
The intake throttle valve 7 is provided in the
An on-off valve 40 composed of a rotary valve is provided.
The on-off valve 40 has an engine output shaft 41 and gears 42, 43.
And interlocking via the interlocking shafts 44 and 45,
A timing adjusting mechanism including a pair of helical splines 46, 47 and an adjusting member 48 engaged with these is provided between the 45. This timing adjusting mechanism is configured such that the axial movement of the adjusting member 48 causes the two interlocking shafts 44,
45 is capable of changing the opening / closing timing of the opening / closing valve 40 by relative displacement in the rotation direction. An actuator 49 for operating the timing adjusting mechanism and the adjusting member 48 of the mechanism, a vacuum pump 50, a passage 51. The control valve 52 and the like constitute drive means for varying the opening operation timing of the on-off valve 40. The timing adjusting mechanism is controlled by the control circuit 25 via the control valve 52, etc., so that the on-off valve 4 is controlled in accordance with the engine speed.
The opening operation timing of 0 is controlled. Since it is not necessary to control the intake leak amount, the intake throttle valve 7 in the main intake passage 6a may be simply opened / closed according to the operating region by an actuator (not shown).

Even in the case of this structure, if the opening / closing valve 10 is opened faster than necessary at a low speed, the adiabatic compression effect may be reduced or the intake air may be blown back, so that the opening operation timing of the opening / closing valve 10 is appropriately delayed. When the engine speed increases, the opening operation timing of the on-off valve 10 is advanced, so that the time until the end of the intake stroke is properly secured.

As still another embodiment, a rotary valve type opening / closing valve that interlocks with an engine output shaft may be provided in the main intake passage with an intake passage structure including a main intake passage and a leak passage as shown in the second embodiment. . Also in this case, a timing adjusting mechanism may be incorporated in the interlocking mechanism between the engine output shaft and the on-off valve, and this may be controlled according to the engine speed. That is, in the second embodiment described above, the automatic valve type opening / closing valve 10 is provided in the main intake passage 6a (see FIG. 6), but instead of this, a rotary valve type opening / closing valve is provided and its opening In an operating region where adiabatic compression of intake air should be performed by controlling the timing adjustment mechanism that makes the timing variable, the opening / closing valve is opened in the middle of the intake stroke and the opening / closing timing is advanced as the engine speed increases. You can do this. In addition, except in the operating range where adiabatic compression of intake air should be performed, the opening / closing valve should be adjusted so that it is in the middle of the entire intake stroke, or interlocking shutoff means should be incorporated to stop the opening / closing valve in the open state. You can leave it.

Further, in the diesel engine having the supercharger in the intake passage, the structure is such that the timing adjusting mechanism is incorporated between the opening / closing valve formed of the rotary valve and the engine output shaft as in the third embodiment and the above-mentioned embodiments. In this case, in addition to operating the open / close valve to perform adiabatic compression of intake air in a specific operating region, the open / close valve is opened only during the intake stroke during high load, etc. The on-off valve can also be used in an Atkinton cycle that increases the supercharging effect while suppressing the maximum pressure.

(Effects of the Invention) As described above, according to the present invention, the on-off valve provided in the intake passage is operated in the middle of the intake stroke to perform adiabatic compression of the intake air, and the opening operation timing according to the crank angle of the on-off valve is set to the engine. As the engine speed is advanced as the engine speed increases, adiabatic compression is achieved over a wide engine speed range by properly adjusting the time from the opening operation timing of the on-off valve to the end of the intake stroke while ensuring the intake charge amount. The effect can be enhanced. Therefore, in addition to improving the startability, it is possible to achieve the effect of preventing misfires, poor combustion, white smoke, HC, etc. at low temperatures or in highlands over a wide range of rotational speeds.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a device according to a first embodiment of the present invention, and FIG.
FIG. 3 is a schematic cross-sectional plan view of this device, FIG. 3 is an enlarged cross-sectional view of the on-off valve, and FIG. 4 is a crank angle for the pressure fluctuation in the combustion chamber and the opening operation timing of the on-off valve in the case of the device of the first embodiment. 5 (a) and 5 (b) are explanatory diagrams showing the pressure fluctuation in the combustion chamber and the opening operation timing of the on-off valve at low rotation speed and high rotation speed in correspondence with time. The figure is the second
FIG. 7 is a vertical sectional side view of the apparatus of the embodiment, and FIG. 7 is VII-VII of FIG.
FIG. 8 is a sectional side view taken along the line, FIG. 8 is a vertical sectional side view of the device of the third embodiment, and FIG. 9 is a schematic plan view of the device of this embodiment. 1 ... Cylinder, 3 ... Combustion chamber, 4 ... Intake valve, 6 ... Intake passage, 7 ... Intake throttle valve, 10, 40 ... Open / close valve, 40 ... Open / close valve, 21-24, 33, 41-52 ... Open / close valve Drive means for changing the opening operation timing, 25 ... Control circuit.

Claims (1)

[Claims] 1. An on-off valve is provided in the intake passage, and the on-off valve is closed until the middle of the intake stroke to restrict the introduction of intake air into the combustion chamber. In an intake system of a diesel engine equipped with an intake introduction control device for introducing a fuel into a combustion chamber to perform adiabatic compression, a drive means for varying an opening operation timing depending on a crank angle of an on-off valve in the intake introduction control device, and an engine An intake device for a diesel engine, comprising: a control unit that controls the drive unit so as to advance the opening operation timing of the on-off valve as the rotation speed increases.