JPH0351890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a diesel engine that has a function of increasing the initial temperature of the compression stroke during startup or warm-up.

(Prior art) Conventionally, in diesel engines, as a means to improve the ignitability at the time of starting and promote starting, as shown in Japanese Utility Model Application Publication No. 55-165935, a method of introducing exhaust gas into the combustion chamber has been proposed. It is known that the initial temperature of the compression stroke of the air in the combustion chamber is increased by adiabatic compression work. In other words, this device is equipped with a throttle valve in the intake passage, which is activated during startup to throttle the intake passage, and also opens the exhaust valve between the end of the intake stroke and the beginning of the compression stroke. During the period from the end of the intake stroke to the beginning of the compression stroke, exhaust gas is allowed to flow into the combustion chamber whose pressure has been reduced, thereby performing adiabatic compression work. However, with this device, the exhaust gas is introduced into the combustion chamber, so the carbon in the exhaust wears the sliding surfaces between the cylinder liner and the piston ring, and the oil used to lubricate the sliding surfaces becomes dirty. There were flaws.

(Objective of the Invention) In view of these circumstances, the present invention provides a diesel engine capable of eliminating the harmful effects of introducing exhaust gas while having the same function as conventional devices to increase the initial temperature of the compression stroke through adiabatic compression work. The present invention provides an intake device.

(Structure of the Invention) The present invention provides an intake passage for a diesel engine.
A throttle valve is provided to throttle the intake passage during startup or warm-up, or during both startup and warm-up, and a throttle valve is provided to throttle the intake passage during startup or warm-up, or during both startup and warm-up. The engine is equipped with an intake air introduction device that opens the intake passage upstream of the throttle valve to the combustion chamber between the end of the intake stroke and the beginning of the compression stroke.

(Embodiment) Fig. 1 shows a first embodiment of the device of the present invention, in which 1 is a cylinder of a diesel engine, a piston 2 is fitted inside the cylinder, and a piston 2 is fitted above the piston 2. A combustion chamber 3 is formed.
4 is an intake passage, and 5 is an exhaust passage, and each opening of both passages 4 and 5 to the combustion chamber 3 is equipped with an intake valve 6 and an exhaust valve 7, respectively.

The intake passage 4 includes a main intake passage 4a provided with a throttle valve 10, and a bypass passage 4b connecting an upstream part and a downstream part of the main intake passage 4a from the throttle valve 10.
is formed. This bypass passage 4b,
A mushroom valve type on-off valve 20 is provided at the opening to the main intake passage 4a downstream of the throttle valve 10.

The throttle valve 10 is operated by a negative pressure actuator 11 using a diaphragm device, and a control circuit 1 is connected to a negative pressure introduction passage 13 between the actuator 11 and the vacuum pump 12.
A three-way solenoid valve 14 controlled by 5 is provided. The control circuit 15 starts the engine based on signals from a load sensor 17 that detects the engine load by detecting the control lever position of the fuel injection pump 16, for example, and a water temperature sensor 18 that detects the engine cooling water temperature. This operating state is detected during the low-load operating state from the time to the warm-up time (hereinafter referred to as the start-up warm-up time). At this time, by introducing negative pressure into the actuator 11 via the three-way solenoid valve 14, the throttle valve 10
is closed to throttle the main intake passage 4a, and during normal operation after warming up, the throttle valve 10 is opened by introducing atmospheric air into the actuator 11 via the three-way solenoid valve 14.

Further, the intake and exhaust valves 6 and 7 and the on-off valve 20 have springs 21, 22 and 23, respectively.
Valve driving cams 25, 26, 2 for each of the above-mentioned valves are provided on a camshaft 24 which is urged in the valve closing direction by
7, the push rods 28, 29, 30 and rocker arms 31, 32, 33 are operated at predetermined timings. In this case, the exhaust valve 7 and the intake valve 6 are opened during the exhaust stroke and intake stroke, respectively, as shown by curves A and B in FIG. 3, as in a general engine. On the other hand, the on-off valve 20 is
As shown by curve C, it is opened from the end of the suction stroke to the beginning of the compression stroke.
In this way, the bypass passage 4b and the on-off valve 20
An intake air introduction device is constituted by the valve mechanism and the valve operating mechanism therefor. Furthermore, the valve operating cam 2 of the on-off valve 20
An on-off valve stop mechanism is provided between the valve drive cam 7 and the push rod 30 to prevent the transmission of operating force from the valve operating cam 27 during normal operation after warming up.

For example, as shown in FIG. 2, this mechanism includes a tappet 40 disposed on a valve operating cam 27 so as to be vertically slidable, and a tappet 40 fitted into the tappet 40 so as to be vertically movable and connected to a push rod 30. It has a plunger 41 and a hydraulic chamber 42 formed in a tapepet 40 below the plunger 41. The hydraulic chamber 42
, from the oil pump 43 to the oil filter 44.
An oil supply passage 46 that supplies oil via a check valve 45 and an oil discharge passage 48 that is opened and closed by a solenoid valve 47 are connected, and the solenoid valve 47 receives the signal a from the control circuit 15. activated accordingly. During startup and warm-up operation, the solenoid valve 4
7 closes the oil discharge passage 48 and confines oil in the hydraulic chamber 42, so that the vertical movement of the tappet 40 in response to the operation of the valve drive cam 27 is transmitted to the plunger 41 and the push rod 3 via the hydraulic pressure in the hydraulic chamber 42.
0, and during normal operation, the electromagnetic valve 47 opens the oil discharge passage 48, so that the hydraulic pressure in the hydraulic chamber 42 is released and the movement of the tappet 40 is not transmitted to the plunger 41.

Next, the operation of this device will be explained.

During the startup warm-up operation, the throttle valve 10 is closed to a small opening degree in response to a signal from the control circuit 15, and the on-off valve 20 is operated at the predetermined timing. In addition, generally the opening period of the intake valve 6 is somewhat longer than the period of the intake stroke, and the intake valve 6 is fully closed when the piston passes the bottom dead center and reaches the early stage of the compression stroke (see Fig. 3). . Therefore, during this startup warm-up operation, the main intake passage 4a is throttled and the bypass passage 4b is closed until the end of the intake stroke, so that the internal pressure of the combustion chamber 3 gradually decreases, and from the end of the intake stroke to the beginning of the compression stroke. In this case, the bypass passage 4b is opened and a large amount of intake air is introduced into the combustion chamber 3. As a result, adiabatic compression work is performed and the temperature at the beginning of the compression stroke increases, and along with this, the temperature at the end of the compression stroke is also raised, making it easier to ignite, improving startability and warm-up performance.

During normal operation after warming up, the throttle valve 10 is opened, and a sufficient amount of air is supplied into the combustion chamber 3 from the main intake passage 4a. At this time, the operation of the on-off valve 20 is stopped by the on-off valve stop mechanism, and the bypass passage 4b is maintained in a closed state. Although it is not necessarily necessary to provide an on-off valve stop mechanism, if the throttle valve 10 is operated for another purpose even after warming up, for example, the throttle valve 10 may be throttled down to some extent to increase heating performance to increase the load on the engine. When the throttle valve 10 is used to block intake air to prevent engine vibration when the engine is stopped, the bypass passage 4b is kept closed by an on-off valve stop mechanism. It is preferable that

4 and 5 show a second embodiment of the invention. In this embodiment, as an intake air introduction device, a butterfly-type on-off valve 50 is provided in the middle of a bypass passage 4b that connects an upstream part and a downstream part of the throttle valve 10 of the main intake passage 4a. , is operated by a pressure-responsive actuator 51 that operates in response to a decrease in the pressure within the intake passage downstream of the throttle valve 10. The actuator 51 includes first and second diaphragm devices 52 and 53, which are divided into atmospheric pressure chambers 52b and 53b and a negative pressure chamber 52, respectively, which are partitioned by diaphragms 52a and 53a.
c, 53c. Both diaphragms 52 mentioned above
a and 53a are directly connected to each other by a rod 54 and to the on-off valve 50, and springs 52d and 53a are compressed in the negative pressure chambers 52c and 53c.
53d urges each diaphragm 52a, 53a in a direction to close the on-off valve 50. 1st
The negative pressure chamber 52c of the diaphragm device 52 is connected to the communication path 5.
Bypass passage 4 downstream of the on-off valve 50 via 5
It is connected to b. Further, the negative pressure chamber 53c of the second diaphragm device 53 communicates with the bypass passage 4b upstream of the on-off valve 50 when it is closed, and communicates with the bypass passage 4b downstream of the on-off valve 50 when the on-off valve 50 is opened to a certain extent. so that communication path 5
6 to a predetermined location of the bypass passage 4b.

According to this structure, the relationship between the negative pressure change downstream of the on-off valve 50 and the opening degree of the on-off valve 50 from the suction stroke to the compression stroke during startup warm-up operation is as shown in FIG. That is, at the beginning of the intake stroke during start-up warm-up operation, the main intake passage 4a is throttled by the throttle valve 10 and the on-off valve 50 is closed, and as the intake stroke progresses from this state, the on-off valve 50 is closed. The downstream intake negative pressure gradually increases, and this negative pressure flows into the negative pressure chamber 52 of the first diaphragm device 52.
introduced in c. When this negative pressure exceeds a predetermined value indicated by point P, the on-off valve 50 is gradually opened against the spring force of the springs 52d and 53d, and the opening degree indicated by point Q (two points in FIG. 5) is gradually opened. When the state shown by the chain line is reached, the negative pressure chamber 5 of the second diaphragm device 53 is
The intake negative pressure downstream of the on-off valve 50 is also introduced into the on-off valve 3c, so that the on-off valve 50 is suddenly fully opened. For this reason, fresh air is supplied from the bypass passage 4b to the combustion chamber 3, and the above-mentioned negative intake pressure also decreases.
Since both diaphragm devices 52 and 53 support each other in the valve open state, the on-off valve 50 is closed when the intake negative pressure is sufficiently reduced. In this way, even with this structure, during startup and warm-up operation,
The on-off valve 50 is opened between the end of the suction stroke and the beginning of the compression stroke, and the same effect as in the first embodiment is obtained.

Note that the specific structure of the device of the present invention is not limited to the above-mentioned embodiments, and includes, for example, means for controlling the throttle valve in the intake passage to open only from the end of the intake stroke to the beginning of the compression stroke during startup warm-up operation. can also be considered. However, with this method, it is difficult to operate the throttle valve with good response at a predetermined timing.
On the other hand, in each of the embodiments described above, the on-off valve 2
0,50 can be activated at predetermined timing. Further, according to the structure of the second embodiment, all the intake air introduction devices can be installed in the intake piping section outside the engine body, and there is no need to perform any special processing on the engine body section (cylinder head, etc.).

Further, in each of the embodiments described above, the throttle valve 10 is closed over the entire range during startup and warm-up operation, and the intake air introduction device is operated, but only at the time of startup when it is particularly necessary to improve ignition performance. For example, the throttle valve 10 and the intake air introduction device may be activated by an ON signal from a starter. Furthermore, since the warm-up performance is improved by the operation of the throttle valve 10 and the intake air introduction device as described above, the throttle valve 10 and the intake air introduction device may be operated only during warm-up.

(Effects of the Invention) As described above, the device of the present invention throttles the intake passage using the throttle valve during startup, warm-up, or both of these startup and warm-up times, and
At this time, a large amount of air can be supplied to the combustion chamber from upstream of the throttle valve between the end of the intake stroke and the beginning of the compression stroke. Therefore, the initial temperature of the compression stroke can be improved by the adiabatic compression work, and the disadvantages of conventional means for introducing exhaust gas into the combustion chamber can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the first embodiment of the device of the present invention, FIG. 2 is an enlarged cross-sectional view of the on-off valve stop mechanism, and FIG.
The figure is an explanatory diagram showing the operation timing of the intake and exhaust valves and the on-off valve, FIG. 4 is a cross-sectional view showing the second embodiment of the device of the present invention, FIG.
The figure is an explanatory diagram showing the relationship between intake negative pressure and opening/closing valve opening degree in this embodiment. 1... Cylinder, 3... Combustion chamber, 4... Intake passage, 4a... Main intake passage, 4b... Bypass passage, 10... Throttle valve, 20, 50... Open/close valve.

Claims (1)

[Scope of Claims] 1. A throttle valve is provided in the intake passage of the diesel engine to throttle the intake passage at the time of starting or warming up, or during a period spanning both of these starting and warming up. Diesel characterized by being provided with an intake air introduction device that opens the intake passage upstream of the throttle valve to the combustion chamber between the end of the intake stroke and the beginning of the compression stroke during the start-up and warm-up periods. Engine intake system. 2. The intake air introduction device includes a bypass passage that connects upstream and downstream of the throttle valve in the intake passage, an on-off valve that closes the bypass passage, and an on-off valve that closes the on-off valve from the end of the intake stroke to the beginning of the compression stroke in conjunction with engine operation. 2. The intake system for a diesel engine according to claim 1, further comprising a valve operating mechanism that is opened during a period of time. 3. The intake air introduction device includes a bypass passage that connects the upstream and downstream sides of the throttle valve in the intake passage, an on-off valve that is provided in the bypass passage and closes the bypass passage, and a valve that closes the bypass passage when the throttle valve is closed. The diesel engine according to claim 1, further comprising a pressure-responsive actuator that opens the on-off valve in response to a decrease in pressure in the intake passage downstream of the throttle valve at the end of the intake stroke. Engine intake system.