JPS6067768A - Pneumatic starter of diesel engine - Google Patents

Abstract

PURPOSE:To improve the startability of an engine by controlling the quantity of compressed air to be flown into a cylinder at an approximately constant rate regardless of variation in pressure of air discharged from an air supply source when a starting valve provided for each cylinder is opened to send compressed air into each cylinder at the expansion stroke so as to start the engine. CONSTITUTION:The entitled equipment controls the opening and closing timings of a starting valve 2 by sending compressed air, fed from an air source 3, into the control chamber of said valve 2 via a passage 6, a distributor 8 and a passage 10, and promotes the starting by sending said compressed air from a passage 5 to the inlet of the starting valve 2 and flowing the compressed air into a cylinder 1 when said valve 2 is opened. A passage resistor 23 is disposed in the passage 6. Inside this passage resistor 23, a two-stage piston 24 is engaged in the two-stage cylinder 25 and pushed higher as the pressure of air discharged by the air source 3, namely, the pressure P0 of air inside a large-diameter chamber 30 becomes higher. Resultantly, the number of the turns of the helical groove 31 with respect to the internal face of a small-diameter part 25a, that is, the resistance against the compressed air may be increased along with the lift of the piston 24.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air starter suitable for large-scale marine diesel engines and the like.

(Conventional example) For example, a large diesel engine for ships/L'41! In Seki,
Since a large starting torque is required, when starting with a YL type starter, the battery power will be large,
The weight of the starter also increases. Therefore, it has conventionally been customary to start the engine using compressed air.Here, to explain an example of a conventional static electric starter for Diesel/I/engines, in Fig. 1, 1 is a cylinder; 1
A total of six sides are provided, and each cylinder 1 is equipped with a starting valve 2. Reference numeral 8 denotes an air source (such as an air tank), and the original pulp 4 is provided at the outlet of the air source 8. On the downstream side of the spring pump 4, the compressed air supply passage (supply pipe line) is divided into two branches,
One of the passages 5 branches into six passages and communicates with an inlet of each starting valve 2 (described later). The other passage 6 also communicates directly with the inlet of the distribution valve 8 via the pulp 7.

The distribution valve 8 has six outlets, each outlet communicating via a passage 10 with a respective start-up, 11F2 control chamber (described below).

Next, the internal structure of the distribution valve 8 (t!S2 diagram) will be explained.
The substantially disc-shaped rotor 9 is fixed to the end of the camshaft 11, and has a notch 12 (FIG. 8) at its peripheral edge. The rotor 9 is provided with an arcuate groove 13 and an annular groove 14 located closer to the center than the groove 13, and both grooves 18,14 communicate with each other via a radial groove 15. As the rotor 90 rotates, the outlet of the distribution valve 8, that is, the inlet 10a of each passage 10,
It can freely communicate with both the notch 12 and the arcuate groove 13. The annular groove 14 communicates with a relief passage 16.

In FIG. 4, each of the aforementioned passages 5 communicates with an inlet 17 (inflow port) of the starter valve 2, and each passage 10 communicates with a control chamber 18 of the starter valve 2. 19 is a starter valve body, and 20 is a spring.

Compressed air (control air) introduced into the distribution chamber 21 of the distribution valve 8 from the passage 6 in FIG.
0, once during the rotation of the camshaft 1101, and during the expansion stroke of the cylinder 1 corresponding to each passage 10.

In the starting valve 2 that receives compressed air through the passage 10 (Fig. 4), the air pressure in the control chamber 18 (control air pressure) increases, and this air pressure increases the pressure in the cylinder 1 (in-cylinder pressure). This overcomes the elasticity (spring force) of the spring 20 and the valve body 19 moves downward in the figure, opening the starter valve 2. That is, now the cross-sectional area of the control chamber 18 is A, the control air pressure is Pl, the cross-sectional area of the valve body 19 is A3, and the cylinder pressure is P.
2. If the spring force is F, PIAl) P, A2
When the pressure reaches +F, the starting valve 2 opens (P, P2 is the pressure per unit cross-sectional area). During the opening period of the starter valve 2, compressed air (starting air) led from the passage 5 flows into the cylinder 1 through the inlet 17, energizes a binuton (not shown) and starts the engine. Passage 1 in Figure 8
0 communicates with the arcuate groove 18, the control chamber 18
The compressed air inside leaks to the relief passage 16 through the passage 10, the groove 18, etc., the control air pressure P□ decreases, and the starting valve 2 closes.

The above-mentioned starting valve opening period is, for example, as shown in B in Fig. 5 when the engine is stopped, that is, when compressed air is injected into the cylinder 1 for the first time, and after the second time after the engine starts rotating. When compressed air is injected, the condition will be as shown in C in FIG. 5, for example.

In FIG. 5, TDC is compression top dead center, and BDC is bottom dead center at the end of expansion. Note that FIG. 5 shows the relationship between the crank angle and the cylinder pressure immediately after the engine rotation starts.

Next, to explain the problems with the conventional device mentioned above,
The discharge air pressure P0 of the air source 8 gradually changes (decreases), but conventionally, the discharge pressure P0 of the air source 8 is the same. When C1 is high, the valve opening timing C1 in FIG. There was a drawback that the amount of compressed air inflow per expansion stroke increased significantly as a whole. Moreover, the intense adiabatic expansion of the compressed air within the cylinder 1 cooled the cylinder 1, lowering the compression temperature and reducing the startability of the engine.

In addition, due to the deterioration of fuel conditions in recent years, there has been an increasing demand for lower engine fuel consumption and higher turbocharging. It has become more difficult to increase the compression temperature within the compressor 1 than in the past.

(Object of the Invention) An object of the present invention is to improve the startability of an air-starting diesel engine.

(Structure of the Invention) A pneumatic starter for a diesel engine according to the first invention suppresses an increase in the amount of air flowing into the cylinder when the discharge air pressure of the air source is high, and suppresses an increase in the amount of air flowing into the cylinder when the discharge air pressure of the air source is high. The structure is such that the amount of air flowing into the cylinder per expansion stroke is approximately constant. Further, in the second invention, in addition to the configuration of the first invention, the starting valve is opened during the compression stroke at the time of starting, so that compressed air flows into the cylinder.

(Example) First, a first example of the air starting device for a diesel engine according to the first invention will be described. That is, in the first embodiment, the starter device is configured almost the same as the conventional example described above, but a new passage resistance is added in the passage 6 between the pulp 7 (FIG. 1) and the distribution valve 8. The container 23 is inserted.

Next, the internal structure of the path resistor 28 will be explained based on FIG. That is, FIG. 6 shows an enlarged cross section of the passage resistor 28, and in the figure, the two-stage piston 24 is slidably fitted into the two-stage cylinder 25. An annular chamber 26 is provided between the small diameter portion 24a of the piston 24 and the cylinder 25. An axial hole 27 and a radial hole 28 perpendicular to the axial hole 27 are provided in the piston 24, and the large diameter chamber 30 in the cylinder 25 and the annular chamber 26 are communicated through the holes 27,28. A spiral groove 81 with a relatively small cross-sectional area is provided on the outer periphery of the small diameter portion of the piston 24, and the spiral groove 81 allows the annular chamber 26 to be closed.
and a small diameter chamber 82 within the cylinder 26 are communicated with each other. Between the large diameter portion 24b of the piston 24 and the cylinder 25,
The spring 88 is compressed. 84 is a ventilation hole provided in the cylinder 25.

A portion of the spiral groove B1 faces the inner circumference of the piston small diameter portion 25a, and the compressed air supplied from the air source 8 to the distribution valve 8 passes through the portion of the spiral groove 81 that faces the inner circumference of the small diameter portion. When doing so, it is designed to receive resistance depending on the air pressure. That is, the piston 24 maintains the air pressure P in the large diameter chamber 30. , that is, as the discharge pressure of the air source 8 increases, the sixth
Slide upwards in the diagram. Accordingly, the length of the spiral groove 31 facing the inner periphery of the small diameter portion 25a, in other words, the number of turns of the spiral groove 3'1 facing the inner periphery of the small diameter portion increases, and the resistance to compressed air also increases. Furthermore, when the air pressure P0 in the large diameter chamber 8o decreases, the piston 24 slides downward in the figure, reducing the resistance to compressed air.

FIG. 7 shows how the control air pressure P□ gradually increases over time after the start of compressed air supply from the distribution valve 8 for various discharge air pressures Po of the air source 3. The middle curve 'L□ represents the relationship between the control air pressure P1 and time T when the discharge air pressure P07% is the lowest, as follows L2, L
The discharge air pressure P0 is higher in the order of No. 3, and L4 is the discharge air pressure P. The relationship between the control air pressure P1 and the time T is shown when P1 is the highest. As is clear from FIG. 7, due to the presence of the passage resistor 2B, the time T1 required for the control air pressure P□ to reach a constant @p□' is equal to the discharge air pressure P of the air source 3.

The higher the value, the longer it will be.

If this relationship is expressed in a graph, it will be as shown in FIG.

FIG. 9 shows the valve opening period C' of the starter valve 2 and the discharge air pressure P of the air source 3 according to the first embodiment. As is clear from the relationship shown in FIG. 8, in the first embodiment, the higher the discharge air pressure Po, the later the valve opening timing C1° becomes. Therefore, the valve opening period C° is Discharge air pressure P. The higher the value, the shorter it becomes. On the other hand, the amount of compressed air flowing into the cylinder 1 per unit crank angle is the discharge air pressure P as described above. The higher the value, the greater the number, so the valve opening period C' for the entire cylinder 1
As with the compressed air, the discharge air pressure P. Regardless of changes in
It remains approximately constant. Therefore, the compression temperature inside the cylinder 1 is also the same as the first one.
As shown by the solid line in Figure 1, the discharge air pressure P. It remains approximately constant regardless of changes in . Note that C2'' in FIG. 9 represents the valve closing timing, and the broken lines in FIGS. 10 and 11 represent the relationship between the discharge air pressure P, air consumption, and compression temperature in the conventional example.

Next, a second embodiment will be explained. In the second embodiment, in place of the passage resistor 28 described above, a resistance portion 41 is provided in the distribution valve 8'' of FIG. The circumferential width is narrower than the circumferential width of the notch 12 in FIG.
A small diameter hole 41 (resistance section...see FIG. 18) and a large diameter hole 42 communicating with the small diameter hole 41 are provided adjacent to 2'. 12th
In the figure, the distance l□ between the large diameter hole 42 and the notch 12 is the passage 1o.
The distance l between the arcuate groove 18' and the notch 12' is equal to the diameter of the inlet 10a.

First, the large-diameter hole 42 (FIG. 18) communicates with the passage 10, and compressed air within the distribution chamber 21° is supplied to the passage 10 through the small-diameter hole 41 and the large-diameter hole 42. Note that the compressed air in the distribution chamber 21' is subjected to large resistance when passing through the small diameter hole 41. As the rotor 9' rotates, the cutout 12' (FIG. 14) continues to communicate with the passage 10, and the compressed air in the distribution chamber 21° flows into the passage 10 without resistance. 1st
Since the spacing shown in FIG. 2 is set as described above, the supply of compressed air to the passage 10 through the large diameter hole 42 and the supply of compressed air through the notch 12' are continuously performed.

As a result, the control air pressure P□ in Fig. 4 rises, and the starting valve 2
is opened and compressed air for starting flows into the cylinder 1 from the passage 5. Subsequently, when the arcuate groove 18° in FIG.
, 15', and 14' into the relief passage 16', the control air pressure P1 decreases, and the starting valve 2 closes.

FIG. 16 shows the supply state of control air according to the second embodiment, and in the second embodiment, compressed air is supplied to the passage 10 through the large diameter hole 42 within the period E during the expansion stroke. Then, within period G, compressed air is supplied through the notch 12'. The boundary point of the rainy period ID, G is, for example, a point approximately 25° after compression top dead center.

For reference, the supply period of compressed air by the notch 12 (FIG. 8) of the first embodiment is shown in FIG. 16. Note that H1 indicates the opening period of the intake valve and exhaust valve, respectively.

In the second embodiment, since the resistance due to the small diameter hole 41 is constant, the discharge air pressure P is as shown by the two-dot chain lines in FIGS. 10 and 11, respectively. The air consumption increases somewhat and the compression temperature decreases somewhat as the It has been greatly improved.

In the eighth embodiment shown in FIG. 17, a throttle valve 50 is provided in the middle of the above-mentioned relief passage (16'), so that the opening degree of the throttle valve 50 can be changed steplessly. In the eighth embodiment, the opening degree of the throttle valve 50 can be increased to promote leakage of compressed air from the passage 10 to the relief passage 16, and -
As a result, the closing timing of the starter valve 2 shown in FIG. 4 can be advanced and the opening period of the starter valve 2 can be shortened. When the valve opening period becomes shorter, the amount of compressed air flowing into the cylinder 1 from the passage 5 decreases, which reduces the cranking speed (
crankshaft rotation speed). The inventor of the present invention has confirmed through experiments that the compression temperature inside the cylinder 1 becomes higher when the cranking rotational speed at startup is lower to some extent. According to experiments, the cranking speed at startup is 6 Or, 1), m, ~100 r
, p, m, the compression temperature is the highest. Conventionally, the cranking speed at startup was usually set to 100.
It is set to r, p, m, and so on.

FIG. 18 shows an embodiment of the second invention, in which two distribution valves are provided. As mentioned above, one distribution valve 8 supplies compressed air to the control chamber of the starter valve 2 during the expansion stroke of each cylinder 1, and the other distribution valve 4
From 8 onwards, compressed air is supplied to the control chamber of the starting valve 2 during the compression stroke of each cylinder 1. That is,
In this embodiment, the starting valve 2 is opened not only during the expansion stroke at startup but also during the compression stroke at startup to allow compressed air to flow into the cylinder 1 from the passage 5. As a result, the amount of air compressed during the compression stroke at startup increases, and the compression temperature becomes even higher.

In embodying the present invention, the number of cylinders 1, etc. can be changed freely. Also, the opening and closing of the starting valve 2 is not based on air pressure.
It can also be performed using an electric or hydraulic actuator. In that case, the discharge air pressure P of the air source 3. It goes without saying that the opening period of the starter valve 2 may be changed in response to fluctuations in the engine speed. In the embodiment shown in FIG. 18, the number of distribution valves can be reduced to one by changing the number of grooves in the distribution valve.

(Effects of the Invention) As described above, according to the first invention, the compression temperature in the cylinder at the time of starting can be increased to improve the startability of the engine. Further, according to the second invention, it is possible to further increase the compression temperature and further improve the startability.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure 1 is a schematic diagram showing the layout of the air starting device, Figures 2 and 8 are a schematic cross-sectional diagram of the distribution valve, Figure 1 is a simplified diagram, and Figure 4 is a simplified diagram of the distribution valve.
The figure is a schematic cross-sectional diagram of the starting valve, Figure 5 is a graph showing the relationship between crank angle and cylinder pressure, Figure 6 is a schematic cross-sectional diagram of the passage resistor, and Figure 7 is a diagram showing how the control air pressure changes over time. Graphs, Figures 8 to 11 are graphs showing the relationship between discharge air pressure and various variables, Figure 12 is a schematic front view of the distribution valve in the second embodiment, and Figures 13 to 15 are Figure 12, respectively. A schematic cross-sectional diagram along the Xjill-XI line to the XV-XV line,
FIG. 16 is a time chart showing the opening and closing timing of the valve in the second embodiment, FIG. 17 is a sectional view of the eighth embodiment, and FIG. 18 is a layout diagram of the second invention. 1... cylinder,
2...Starting valve, 8...-Air source Patent applicant Yanmar Diesel Co., Ltd. Figure 9 Franz angle -1→- Figure 1θ, 7 7/ Figure 1I SIL#-Amaru Po-- 16 ' Figure 18

Claims (2)

[Claims] (1) Air starter for a diesel engine configured to introduce compressed air for starting from an air source to a starting valve installed in the cylinder, open the starting valve during the expansion stroke during starting, and allow the compressed air to flow into the cylinder. In the device, the amount of air flowing into the cylinder is suppressed from increasing when the discharge air pressure of the air source is high, and the amount of air flowing into the cylinder during one expansion stroke is approximately An air starting device characterized by being made to be constant. (2) Air starter for a diesel engine configured to introduce compressed air for starting from an air source to a starting valve provided in the cylinder, open the starting valve during the expansion stroke at starting, and allow the compressed air to flow into the cylinder. In the device, the amount of air flowing into the cylinder is suppressed from increasing when the discharge air pressure of the air source is high, and the starting valve is also opened during the compression stroke at startup to allow compressed air to flow into the cylinder. An air starting device characterized by: