JPH06280721A - Method for starting diesel engine - Google Patents

Abstract

PURPOSE:To shorten a time before reaching initial explosion and to reduce generation of white smoke by efficiently increasing a temperature of air sucked into a cylinder while increasing a rotational speed of a crankshaft by reducing pumping resistance when started a diesel engine. CONSTITUTION:Air, closely sealed between the inside of a cylinder 1c and the inside of an exhaust manifold 11 in the upstream from an exhaust brake valve 5 connected to this cylinder, is continuously compressed and expanded by reciprocating a piston 8, and in this way, a temperature of air in the cylinder 1c is increased, to inject fuel into the cylinder 1c first when this air temperature sufficiently rises, so that a diesel engine 1 is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a diesel engine, which improves ignition performance of the diesel engine and improves startability thereof.

[0002]

2. Description of the Related Art Conventionally, in order to start a diesel engine, a crankshaft is rotated by a starter motor,
This is performed by opening and closing the intake valve and the exhaust valve in accordance with each process of intake, compression, expansion, and exhaust of the diesel engine, and injecting fuel into the cylinder by an electronically controlled fuel injection system. However, due to the peculiarities of the diesel engine that does not have a spark plug, until the injected fuel explodes for the first time (hereinafter referred to as the initial explosion), the above-mentioned steps are repeated (hereinafter referred to as pumping) It is necessary that the temperature of the air rise above a predetermined value. Therefore, it takes a predetermined time to start the diesel engine.

[0003]

In order to start the diesel engine in this way, it is necessary to repeat the above four steps several times by rotating the crankshaft with the starter motor. If the rotation speed of the shaft is increased, the time until the initial explosion can be shortened. However, in the compression step of the above steps, the air trapped in the cylinder must be compressed by the piston, so the compression resistance and heat loss at this time prevent the crankshaft from increasing in rotational speed during diesel engine startup. It has become. Conventionally, a means of increasing the rotation speed of the crankshaft by increasing the capacity of the starter motor has been adopted, but there is a limit to the increase of the capacity of the starter motor.

Further, the air that has been compressed in the above-mentioned compression process and whose temperature has risen is also discharged out of the cylinder in the subsequent exhaust process, so it cannot be said that the heating efficiency of the air is high. A method of heating the intake air to the cylinder by providing an intercool heater in the intake path of the diesel engine is also adopted, but an interheat heater must be provided separately, and a device for controlling this is further added. The drawback is that it must be provided.

Further, conventionally, the fuel has been injected from the beginning of the rotation of the crankshaft. Therefore, the fuel injected before ignition is discharged to the outside of the cylinder together with the air discharged to the outside of the cylinder in the exhaust process, and the white It has the drawback of producing smoke.

Therefore, an object of the present invention is to reduce the pumping resistance at the time of starting the diesel engine to increase the rotational speed of the crankshaft and to efficiently increase the temperature of the air taken into the cylinder. It is an object of the present invention to provide a method for starting a diesel engine, which can shorten the time until the explosion and reduce the generation of white smoke.

[0007]

In order to achieve the above-mentioned object, a method for starting a diesel engine according to the present invention is to open an intake valve and close an exhaust valve of a diesel engine, and then lower a piston to move the cylinder inside the cylinder. And a step of inhaling into the cylinder is completed, the intake valve is closed, the exhaust valve is opened, and an exhaust brake valve disposed in an exhaust passage of the diesel engine is closed, Forming a closed space consisting of a space in the exhaust passage upstream of the exhaust brake valve, a space in the cylinder, and a space in the exhaust port between the two spaces; and reciprocating the piston. The step of repeatedly expanding and contracting the air in the closed space to raise the temperature of the air to a predetermined value, and the rotational speed of the diesel engine are When raised to value, said exhaust valve closes to inject fuel into the cylinder, characterized in that a step of igniting is raised the piston.

[0008]

According to the present invention, the air sealed inside the cylinder, the exhaust manifold upstream of the exhaust brake valve communicating with the cylinder, and the space therebetween is continuously compressed by reciprocating the piston. -Expand to raise the temperature of the air in the cylinder, and only when the temperature of the air has risen sufficiently is fuel injected into the cylinder to start the diesel engine.

According to such a diesel engine starting method, the air continuously compressed / expanded by the reciprocating movement of the piston is not compressed only in the cylinder but rather in the cylinder and in the exhaust brake valve. Since it is compressed in a larger space that communicates with the inside of the exhaust manifold on the upstream side, it is possible to reduce the compression resistance and heat loss during air compression, and easily increase the engine speed at engine startup. be able to. Moreover, as described above, this air is held in the sealed space that connects the cylinder and the exhaust manifold, and is not exhausted until the engine is ignited, so that the air temperature is efficiently raised. You can Then, the fuel is injected only when the temperature of the air in the cylinder rises sufficiently, so that the amount of unburned combustion exhausted as white smoke can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing only a cylinder head 1b portion of a cylinder 1a of a diesel engine 1, and an exhaust port 1c and an intake port 1d are formed in the cylinder head 1b. An exhaust valve 3a is attached to the exhaust port 1c, and an intake valve 3a is attached to the intake port 1d.
b is attached. An exhaust manifold 4 is connected to the exhaust port 1c, and an exhaust brake valve 5 is attached downstream of the exhaust manifold 4. In the figure,
6 is an exhaust pipe, and 6a is a silencer interposed in the exhaust pipe 6. Further, the intake manifold 7 is installed in the intake port 1d.
And the intake manifold 7 communicates with the atmosphere through an air cleaner (not shown). In the figure, I
Is a pressure accumulating unit injector for injecting fuel into the cylinder 1a, 8 is a piston, and 8a is a connecting rod connecting the piston 8 and a crankshaft (not shown).

A valve actuator 15 is connected to each of the intake valve 3a and the exhaust valve 3b, and the exhaust brake valve 5 is also connected to the valve actuator 15 via a link mechanism 9. The detailed structure and operation of the valve actuator 15 will be described later. These valve actuators 15 are high pressure air supply pipes 15a,
The control valve 10 is connected via 15a and 15a, and the control valve 10 is connected to a high pressure air supply source 11 via a high pressure air supply pipe 10a. Reference numeral 12 is a central processing unit (CPU) that issues a control signal to the control valve 10 and the unit injector I. The CPU 12 may be an ordinary vehicle-mounted computer.

When the diesel engine 1 is started, the CPU 12 sends a control signal to the control valve 10 to open the intake valve 3b and close the exhaust valve 3a by the valve actuator 15 to start a starter motor (not shown). ) Is driven to lower the piston 8 to suck air into the cylinder 1c. At the end of this intake process, the intake valve 3b is closed, the exhaust valve 3a is opened, and the exhaust brake valve 5 is closed. As a result, a sealed space defined by the inside of the cylinder 1a, the inside of the exhaust port 1c, and the inside of the exhaust manifold 4 upstream of the exhaust brake valve 5 is formed. In this state, the piston 8 is reciprocated by the starter motor, and the air in the sealed space is repeatedly compressed and expanded to raise the temperature of the air.

FIG. 2 shows the relationship between the pressure in the cylinder 1c and the stroke of the piston 8 at this time. In the figure, a
Indicates a compression stroke, and b indicates an expansion stroke. According to the starting method of the present invention, the piston 8 repeats the compression stroke a and the expansion stroke b, and warms the air by the energy loss A between the strokes a and b. On the other hand, when the conventional diesel engine is started, the air is compressed only in the cylinder 1c, so the piston repeats the compression stroke c and the expansion stroke d, and the pressure in the cylinder 1c rises sharply in the compression stroke c. However, this causes a large resistance (compression resistance) to the movement of the piston 8 and causes a heat loss. The energy loss between the compression stroke c and the expansion stroke d is represented by B.
In the starting method of the present invention, the pressure increase in the cylinder 1c can be suppressed to a much lower level than in the conventional method, and therefore, the starter motor can sufficiently increase the rotation speed at the time of starting the diesel engine 1. You can Therefore, without increasing the capacity of the starter motor,
Air can be sufficiently warmed up.

In this way, when the rotation speed of the diesel engine 1 is sufficiently increased and the temperature of the air reaches a predetermined temperature, the CPU 12 issues a fuel injection signal to the unit injector I, and the unit injector I becomes a cylinder. 1c
Fuel is injected into the inside. This state is shown in FIG. In the figure,
C shows an increase curve of the engine speed by the starting method of the present invention, and D shows an increase curve of the engine speed by the conventional starting method. According to the method of the present invention, the engine speed rises quickly, so if fuel is injected at the time e when the engine reaches a predetermined speed, immediately after that, the initial explosion occurs at f. On the other hand, in the conventional starting method, not only the increase in the engine speed is slow, but also the fuel is continuously injected for a period h from immediately after the engine starts to the initial explosion g, During this period, white smoke containing unburned fuel is discharged during h.

4 to 10 are vertical sectional views of the valve actuator 15 in various operating states. The valve actuator 15 is vertically symmetrical, and the upper member corresponding to the lower member is designated by the same reference numeral as the lower member with a subscript a.

As shown in FIG. 4, the valve actuator 15 has an output shaft 31, and the exhaust valve 3 is provided at one end thereof.
a, the intake valve 3b is fixed, and the link mechanism 13
The exhaust brake valve 14 is connected through the valve (see FIG. 1). In addition, the valve actuator 15
The housing 39 has a low-mass main piston 33 equipped with an O-ring 43 and air valves 35 and 35a. The air valves 35 and 35a are locked by the permanent magnets 41 and 41a at fixed positions, respectively, and moved from their respective positions by pulse excitation of the coils 45 and 45a by the control device. The air valves 35 and 35a have annular bodies having hollow valve shafts 37 and 37a extending therefrom, respectively. The air valves 35 and 35a are used to perform various opening / closing operations during the operation of the valve actuator 15.
3 and the housing 39. The housing 39 is, for example, 1 by a pump (not shown).
High pressure cavity 5 pressurized to around 00 psi gauge pressure
9, 59a and low pressure cavity 61 open to the atmosphere,
61a.

FIG. 4 shows an initial state in which the main piston 33 is at the lower end position and the air valve 35 is closed. In this state, the annular ring 49 of the air valve 35 is in the annular groove of the housing 39 and is in contact with the O-ring 51 for sealing. As a result, the compressed air in the cavity 59 is confined and the main piston 33
To prevent exerting power on. In this position,
The main piston 33 is pressed downward by the force of compressed air in the cavity 64a. The pressure of this compressed air is greater than that of the cavity 61a. Cavity 6
In FIG. 4, 1a communicates with the surface 34 of the recessed body 52 via an annular passage 36a in the air valve 35a which is parallel to the hole 42a and parallel to the passage 71 in the body 52a. The annular passages 36 and 36a are provided for the air valve 3
5, 35a are formed when each is in the closed position and are closed when the air valves 35, 35a are each in the open position. The bodies 52 and 52a having the recesses are the main
It is attached to the piston 33 and is integral with it. Shallow recesses 46 and 46a, 54 and 54a are formed in the bodies 52 and 52a, respectively. When the main piston 33 is at the lower end, the main piston 33
Surface 62 communicates with low pressure cavity 61 via valve port 53, hole 42, and passage 36.

In FIG. 5, a reciprocating air valve 35 is used.
Moves downwards, for example 1.5 mm, while the main
The piston 33 is still in a non-moving state, but high-pressure air is supplied to the main piston 33 from the cavity 59 through the four shallow recesses 54 provided at equal intervals in the circumferential direction around the body 52. To the lower surface 62 of.
The air valve 35 is opened by applying an electric pulse to the coil 45 that temporarily weakens or disables the restraining force of the armature 40 by the permanent magnet 41. The armature 40 is fixed to the end of the valve shaft 37. When the restraint force is temporarily disabled, the air pressure in the cavity 59 acted by the pressure in response to the first annular surface 69 of the air valve 35 causes the air valve 35 to open. The communication between the cavity 57 and the cavity (low-pressure air outlet) 61 formed between the second annular surface 38 and the housing wall 47 by the annular shoulder 44 as the air valve 35 moves downward is established. Force is exerted on the main piston 33 in the upward direction.

The ring 49 is not attached to the housing 3 until the annular shoulder 63 of the air valve 35 is engaged with the end of the recess 54.
The pressure of the cavity 59 is fully transmitted to the recess 54 and the cavity 64 away from the annular groove 9 (see FIG. 6).

In FIG. 6, the air valve 35 is almost fully opened to about 2.
It shows a state in which the main piston 33 is moved upward by about 3.5 mm while being opened by 8 mm. FIG. 5 shows that high pressure air is supplied to the cavity 57 and the surface 62 of the main piston 33 and starts moving upward. The supply of high pressure air to the cavity 64 is stopped when the end of the recess 54 passes through the annular shoulder 75 of the housing 39.
However, the main piston 33 continues to move upward due to the force of the high pressure air in the cavity 64. There are a plurality of holes 42 around the air valve 35. Air valve 35 and main
By the relative movement of the piston 33 in the axial direction, the air valve 3
When the annular shoulder 65 of 5 makes the cavity 59 and the cavity 57 communicate with each other through the recess 46 and the hole 42, the surface 38
Due to the high pressure acting on the air valve 35, a force in the closing direction (upward direction) acts on the air valve 35. The inner annular surfaces 48, 48a of the air valves 35, 35a, respectively, are at low atmospheric pressure throughout operation of the air valves.

In FIG. 7, the main piston 33 is about 6.1.
mm and continues to move further upwards in FIG. The air valve is still at the 2.8 mm position and is in the lowest fully open position. The shoulder 65 is completely away from the end of the cooperating recess 46 and directs high pressure air from the cavity 59 through the sealing surface 47 into the cavity 57 and exerts pressure on the surface 38. The air valve 35 tries to stop at this position for a short time because of the compressed air acting on the annular surface 69 and the surface connected to the annular surface 69, but since the area of the surface 38 is larger than the surface of the surface 69,
The air valve 35 receives a force in a direction of closing the air valve 35 (upward). This significantly reduces the force required to return the air valve from the open position (bottom end), so
The magnetic force required for the permanent magnet 41 on the armature 40 is greatly reduced. By discharging the high pressure air in the cavity 59 through the recess 46 located behind the recess 54,
The pressure at 8 is delayed until the main piston 33 is fully advanced and the air valve 35 is still closed.

A feature of the valve actuator 15 is that a passage 71 parallel to the axial direction exists in the bodies 52, 52a and the main piston 33. These are arranged at intervals in the circumferential direction, and the air valves 35, 35
a and the main piston 33 are in operation, the cavity 5 is always
The pressures within 0 and 50a are equalized. This is because at least one of the cavities 50, 50a maintains fluid communication with the low pressure cavities 61, 61a. This is an efficient way to keep the surfaces 48, 48a at a low pressure at all times. Therefore, the cavities 57, 57a,
When a high pressure acts on the air valves 35 and 35a, the air valves 35 and 35a are efficiently closed by aerodynamic force.

In FIG. 8, the air valve 35 is located about 2.0 mm from its closed position, is being returned to the closed position by receiving aerodynamic force on the surface 38, and the magnet 4 to the armature 40 is being moved.
An attractive force of 1 is trying to return the armature 40 towards the magnet latch. In FIG. 8, the main piston 33 is about 6.1 m.
It is moving m. In FIG. 9, the main piston 33 has moved about 6.1 mm. In FIG. 9, the air valve 35 is about 1.5 mm from the closed position and the main piston 33 has moved about 10 mm.

An intermediate pressure of about 4 psi as a gauge pressure is introduced into the cavity 64 from the intermediate port 67 so that the high pressure air in the cavity 64 is reduced to the intermediate pressure. The port 67 discharges the pressure of the pressurized air acting on the surface 62 of the main piston 33 and removes the acceleration force from the piston. The port 67 also exerts an intermediate pressure on the opposite face 62a of the piston, which acts to trap it, compress it, and slow it down when approaching the second position. The port 67 also serves to apply an intermediate pressure to this working surface of the piston, temporarily fixing the piston in the second position until the air valve 35a starts the next opening operation.

FIG. 10 shows a state in which both the air valves 35 and 35a are fully closed and the main piston 33 is about to reach the upper end. The air compressed in the cavity 64a to a high pressure has a recess 54a, a hole 42, and a cavity 5
7a and the cavity 61 to the atmosphere.

The movement of the valve actuator 15 in one direction has been described above. However, since the structure of the valve actuator 15 is symmetrical in the vertical direction, the return movements of the air valve 35a and the main piston 33 are the same as those described above. Is the same as the upside down, and the description thereof is omitted.

[0027]

As described above, according to the diesel engine starting method of the present invention, the inside of the cylinder and the inside of the exhaust manifold upstream of the exhaust brake valve communicating with the cylinder are hermetically sealed. The air is continuously compressed and expanded by reciprocating the piston, which quickly raises the temperature of the air in the cylinder and injects fuel into the cylinder only when the air temperature rises sufficiently. And start the diesel engine.

According to such a diesel engine starting method, the air continuously compressed and expanded by the reciprocating movement of the piston is not compressed only in the cylinder but rather in the cylinder and in the exhaust brake valve. Since it is compressed in a larger space that communicates with the inside of the exhaust manifold on the upstream side, it is possible to reduce the compression resistance and heat loss during air compression, and easily increase the engine speed at engine startup. be able to. Moreover, as described above, this air is held in the sealed space that connects the cylinder and the exhaust manifold, and is not exhausted until the engine is ignited, so that the air temperature is efficiently raised. You can Then, the fuel is injected only when the temperature of the air in the cylinder rises sufficiently, so that the amount of unburned combustion exhausted as white smoke can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a cylinder head portion of a diesel engine for explaining a method for starting a diesel engine of the present invention.

FIG. 2 is a diagram showing a relationship between a piston stroke and a cylinder pressure for comparing a starting method of a diesel engine of the present invention and a conventional starting method.

FIG. 3 is a diagram showing a relationship between an engine speed and time for comparing a diesel engine starting method of the present invention and a conventional starting method.

FIG. 4 is a vertical cross-sectional view of a valve actuator.

FIG. 5 is a vertical cross-sectional view of a valve actuator.

FIG. 6 is a vertical sectional view of a valve actuator.

FIG. 7 is a vertical cross-sectional view of a valve actuator.

FIG. 8 is a vertical sectional view of a valve actuator.

FIG. 9 is a vertical cross-sectional view of a valve actuator.

FIG. 10 is a vertical sectional view of a valve actuator.

[Explanation of symbols]

 1 ... Diesel engine 1a ... Cylinder 1b ... Cylinder head 1c ... Exhaust port 1d ... Intake port 3a ... Exhaust valve 3b ... Intake valve 4 ... Exhaust manifold 5 ... Exhaust brake valve 8 ... Piston 10 ... Control valve 11 ... High pressure air supply source 15 … Valve actuators

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Negishi Inventor Hideo Negishi 3-1, 1 Hinodai, Hino City, Tokyo Hino Motors Co., Ltd. Hino Factory

Claims (1)

[Claims] 1. A diesel engine has an intake valve opened and an exhaust valve closed, and then a piston is lowered.
Intake into the cylinder, and after the intake into the cylinder is completed, the intake valve is closed, the exhaust valve is opened, and the exhaust brake valve arranged in the exhaust passage of the diesel engine is closed. Forming a closed space consisting of a space in the exhaust passage upstream of the exhaust brake valve, a space in the cylinder, and a space in an exhaust port between the two spaces; and reciprocating the piston. And repeatedly expanding and contracting the air in the closed space to raise the temperature of the air to a predetermined value, and when the rotation speed of the diesel engine rises to a predetermined value, the exhaust valve is closed to A step of injecting fuel into a cylinder, raising the piston and igniting the fuel, and starting the diesel engine.