JPS6025612B2 - Diesel engine fuel injection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a diesel engine,
In particular, the present invention relates to one in which fuel injection timing is delayed and corrected depending on the engine load.

In general, in diesel engines, in order to take measures against emissions, exhaust gas, noise, etc. during operation, when the engine load falls below a certain set value, the fuel injection timing is corrected to be delayed compared to when the engine is under normal load. It is equipped with a fuel injection system that allows it to do so. As this type of fuel injection device, there are subordinate systems, for example, Japanese Patent Application Laid-Open No. 53-44724.
The one disclosed in the above publication and the one shown in FIG. 1 are known as those generally practiced.

That is, in FIG. 1, 1 is a housing of a distribution type fuel injection pump, 2 is a pump chamber formed in the housing 1, 3 is a drive shaft that rotates at half the engine speed, and 4 is the drive shaft. A hydraulic pressure generating device consisting of a feed pump 5 attached to a shaft 3 and a regulating valve 6 that adjusts the oil feeding pressure of the feed pump 5, and the hydraulic pressure generating device 4 generates fuel hydraulic pressure corresponding to the engine rotation speed. The pump chamber 2 is provided so as to be transmitted to the pump chamber 2. Reference numeral 7 denotes a pump/distribution plunger mounted in a sliding hole 8 formed in the housing 1, and the end of the plunger 7 has a cam surface 9a having a number of ridges corresponding to the number of cylinders of the engine. The formed cam disk 9 is fixed, and the cam disk 9 and the drive shaft 3 are connected in the rotational direction via a driving disk 10.

On the other hand, reference numeral 11 denotes a roller holder rotatably provided in the housing 1 concentrically with the drive shaft 3, and the roller holder 11 has rollers 12, 12 having the same number of ridges as the cam surface 9a of the cam disk 9. ... is supported and maintained,
A cam surface 9a of a cam disc 9 is pressed against the rollers I2, 12, . The reciprocating movement and the rotation for dispensing are performed simultaneously. Further, reference numeral 14 denotes an injection timing adjustment device for adjusting the injection timing of fuel. is fixed shaft 17
It is connected to the roller holder 11 via a lever 18 that can freely swing around the timer piston 16, and the hydraulic pressure generated by the hydraulic pressure generating device 4 transmitted to the pump chamber 2 is applied to the pressure receiving surface of the timer piston 16 to generate a timer piston. 16 is moved, and the movement of the timer piston 16 causes the roller holder 11 to rotate via the lever 18, thereby relatively changing the contact position between the roller 12 and the cam surface 9a of the cam disc 9. The injection timing is adjusted according to the hydraulic pressure generated by the hydraulic pressure generator 4, and when the generated hydraulic pressure is high, the fuel injection timing is advanced, and when the generated hydraulic pressure is low, the fuel injection timing is delayed. . Reference numeral 19 denotes a cut-off sleeve slidably mounted on a portion of the plunger 7 that projects into the pump chamber 2 so as to open and close the cut-off port 7b that fits into the vertical hole 7a of the plunger 7; Slide the off-sleep 19 on the plunger 7 and move it to the left in the figure to advance the entrance timing of the cut-off port 7b and reduce the fuel injection amount, and conversely move it to the right to reduce the fuel injection amount. It is provided to delay the exit timing and increase the fuel injection amount.

Further, 20 is a control lever that is linked to an accelerator pedal (not shown), and the control lever 20
is controlled by housing 1/shaft 21'
An eccentric pin 22 is attached to the inner end of the shaft 21', and the upper end of a tension lever 24 is connected to the eccentric pin 22 via a governor spring 23. The lower end of the pin 26 is connected to the collector lever 25- which is supported on the housing 1.
The pin 26 is pivotally supported by the start lever 2.
7 is rotatably supported on the tension lever 24, and the upper end of a start spring 28 whose lower end contacts the tension lever 24 is fixed to the upper end of the start lever 27, while the lower end of the start spring 28 is fixed to the upper end of the start lever 27. A ball head pin 29 is provided upright to engage with a pin hole 19a formed in the cut-off sleeve 19, and the tension of the governor spring 23 is changed by changing the angle of the control lever 20 according to the engine load. Governor spring 23
The fuel injection amount is controlled by swinging the tension lever 24 and moving the cutoff sleeve 19 by changing the tension of the cutoff sleeve 19. 30 is a centrifugal flyweight mechanism built into the pump chamber 2, and the centrifugal flyweight mechanism 30 includes a governor gear 32 that meshes with a drive gear 31 fixed to the drive shaft 3.
a flyweight 35 built into a flyweight holder 34 that is integrated with the governor gear 32, and a governor shaft 33 that rotatably supports the governor shaft 33;
The governor sleeve 36 is slidably attached to the start lever 27, and the governor sleeve 36 is slid by the expanding operation of the flyweight 35 due to centrifugal force, and the tip of the governor sleep 36 presses the back of the start lever 27. Accordingly, the cut-off sleeve 19
The fuel injection amount is adjusted according to the engine speed by moving and adjusting the engine speed.

Furthermore, 37' is a hydraulic control device for controlling the fuel oil pressure, and the hydraulic control device 37' has an oil pressure lowering passage 38', and the oil pressure lowering passage 38' is connected to the governor shaft 33 of the flyweight mechanism 30. The pump chamber 2 and the suction side of the hydraulic pressure generator 4 are connected through a hole 39' formed in the governor sleeve 36 through the housing, and the hydraulic pressure of the hydraulic pressure generator 4 (pump chamber 2) is connected to the pump chamber 2 and the suction side of the hydraulic pressure generator 4. This reduces the When the engine load is below the set value, that is, when the angle of the control lever 20 is below the set angle, the hydraulic control device 37' causes the governor sleeve 36 of the flyweight mechanism 30 to move to the right in the figure. The hole 39' of the governor sleeve 36 is aligned with the closed part of the oil pressure lowering passage 38 on the pump chamber 2 side to open the oil pressure lowering passage 38', thereby lowering the fuel oil pressure in the pump chamber 2, and the injection timing adjustment device 14 This operates to delay the fuel injection timing as shown by the broken line in FIG. 4. Note that 40 is a delivery valve that prevents the fuel pumped by the plunger 7 from flowing back, and 41 is a fuel cut valve that cuts off the fuel from being fed to the plunger 7. The fuel injection device is thus configured. However, in such conventional fuel injection devices, the fuel injection timing is uniformly delayed in all areas where the engine load is below the set value, so the fuel injection timing is delayed during light loads including idling. There is a problem in that this delay has a large effect on engine performance, and on the contrary, the combustion state of the engine becomes unstable, making white smoke more likely to be produced due to misfire.

Regarding measures against N○×, when the engine is under a light load, the occurrence of N○× is relatively small, and there is little need to forcefully delay the injection timing.

The present invention has been made in view of these points, and in the fuel injection system for a diesel engine as described above, a cut valve is provided in the oil pressure decreasing passage of the hydraulic control device, and the oil pressure decreasing passage is closed when the engine is under light load. By doing so, the fuel injection timing characteristics at light loads where the degree of N0k generation is relatively small can be set to be the same as those at high loads with good combustion, and the fuel injection timing characteristics at light loads can be It is an object of the present invention to provide a fuel injection device for a diesel engine that can maintain good engine performance. Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The basic structure of the fuel injection device for a diesel engine has been described in detail with reference to FIG. 1, so the same parts as in FIG. 1 are denoted by the same reference numerals and detailed explanation thereof will be omitted.
In a diesel engine fuel injection device as shown in FIG. 1, there is a hydraulic pressure generating device 4 that generates fuel hydraulic pressure corresponding to the engine rotation speed, and the fuel injection timing is adjusted according to the hydraulic pressure generated by the hydraulic pressure generating device 4. and an oil pressure lowering passage 38' for reducing the oil pressure of the oil pressure generator 4, the oil pressure control device lowers the oil pressure and delays the fuel injection timing when the engine load is below a set value. 37', as shown in FIGS. 2 and 3, the hydraulic pressure lowering passage 3 of the hydraulic control device 37
8, the control lever shaft 21 interlocked with the accelerator pedal is connected to a grooved hole 21a equipped with iron, and the grooved hole 21a constitutes a part of the oil pressure lowering passage 38, and the shaft hole 21a A cut valve constituted by the control lever shaft 21 is disposed in the (hydraulic pressure lowering passage 38).

That is, the cut valve is connected to the shaft hole 2 of the oil pressure lowering passage 38 in the peripheral wall of the control lever shaft 21.
A passage groove 42 extending in the vertical direction (in the direction of the wisteria) is formed corresponding to the entrance portion 1a, and as the control lever shaft 21 rotates, the passage groove 42 is connected to the opening □ of the shaft hole 21a of the oil pressure lowering passage 38. The oil pressure lowering passage 38 is disconnected by making the gates coincide and passing through each other, or by separating them from the gate and closing the opening □ with the peripheral wall of the shaft 21. By setting the circumferential upper layer of the circumferential wall of the shaft 21 of the above-mentioned structure 42 at a predetermined position, as shown by the solid line in FIG. At times, the oil pressure lowering passage 38 is closed to maintain the oil pressure in the pump chamber 2 at a high pressure, thereby preventing a delay in the fuel injection timing. Next, to explain the operation of the above embodiment, when the engine load is high, i.e., the engine load exceeds a set value, the angle of the control lever 20 is large and the tension of the governor spring 23 becomes large, and the governor sleeve 36 is moved as shown in FIG. Since the hole 39 of the governor sleeve 36 and the entrance of the oil pressure lowering passage 38 on the pump chamber 2 side do not match, the oil pressure in the pump chamber 2 does not drop and is removed from the oil pressure generator 4. It corresponds to the engine rotation speed as it is being transmitted, and therefore the injection timing adjustment device 14
Since the is not activated, the fuel injection timing is not delayed.

Additionally, when the engine load decreases to below the set value, the angle of the control lever 20 decreases by 4 degrees, and the governor sleeve 36 moves to the right in the figure due to the decrease in the tension of the governor spring 23. The lever hole 39 coincides with the entrance of the oil pressure lowering passage 38 on the pump chamber 2 side, and at the same time, the cut valve, that is, the passage groove 42 of the control lever shaft 21 allows the closed parts of the shaft holes 21a of the oil pressure lowering passage 38 to pass through each other. Since the oil pressure lowering passage 38 is opened, the fuel in the pump chamber 2 flows out into the oil pressure lowering passage 38, and the fuel oil pressure in the pump chamber 2 is lowered.Therefore, the injection timing adjustment device 14 is activated, and the fuel pressure is lowered. The injection timing is corrected to be delayed compared to when the load is high.

Further, when the load on the engine decreases to a predetermined value smaller than the above-mentioned set value and enters a light load state including an idling state, the angle of the control lever 20 becomes even smaller, and the governor leaf 36 is held at the right side in the figure, as in the case where The opening □ of the hole 21a is closed by the operation of the cut valve (rotation of the control lever shaft 21).
The oil pressure drop passage 38 will be closed, so that
The oil pressure in the pump chamber 2 does not decrease, so that the fuel injection timing is prevented from being delayed and adjusted to the same state as at the time of high load. As a result, the combustion state of the engine is maintained well, misfires and the like are prevented, and engine performance can be improved. In addition, since the cut valve is constituted by the control lever shaft 21, the lever opening characteristic (governor characteristic) of the control lever 20 to which the shaft 21 is attached is shown in FIG.
As shown in Fig. 6, it is possible to utilize the similarity between the lever relationship characteristics and the NO wide occurrence state, which makes it possible to control the operation of the cut valve with high precision, and to improve its structure. can be made simple.

As shown in Figure 5, the relationship between the fuel injection timing delay prevention area and the engine speed when the engine is under light load is such that when the engine speed is high, the delay prevention area A becomes smaller (inversely). On the other hand, when the engine speed is low, the delay stop zone A becomes large (on the contrary, the delay zone B becomes 4.0 cm), and the delay stop zone A changes depending on the engine speed. can be done.

As described above, according to the present invention, there is provided a hydraulic pressure generator that generates fuel oil pressure corresponding to the engine rotation speed, an injection timing adjustment device that adjusts fuel injection timing according to the oil pressure generated by the oil pressure generator, A fuel injection device for a diesel engine, comprising: a hydraulic pressure reducing passage that lowers the hydraulic pressure of the hydraulic pressure generation device; and a hydraulic control device that reduces the hydraulic pressure and delays fuel injection timing when the engine load is below a set value. , a cut valve is provided in the oil pressure lowering passage of the hydraulic control device to block the oil pressure lowering passage when the engine load is at a light load that is less than a predetermined value smaller than the set value, thereby delaying the fuel injection timing at light loads. By preventing this, it is possible to improve the combustion performance of the engine under light load while ensuring countermeasures against N○×, etc., and it is possible to improve the engine performance.

In addition, if the cut valve is configured with a control lever shaft that interlocks with the accelerator pedal, and the oil pressure lowering passage is interrupted by a groove formed in the peripheral wall of the control lever shaft, the engine load on the control lever shaft can be reduced. Since the characteristics of the cut valve are similar to those of the melon generation characteristic, the cut valve can be controlled easily and accurately.

Brief explanation of the drawings Figure 1 is a vertical sectional view showing a conventional example, Figure 2 is a longitudinal sectional view showing a conventional example;
7 to 7 illustrate embodiments of the present invention, FIG. 2 is an enlarged vertical cross-sectional view of the main part, FIG. 3 is a cross-sectional view taken along line mm in FIG. 2,
Fig. 4 is a graph showing the correction characteristics of fuel injection timing with respect to load, Fig. 5 is an operating range diagram, Fig. 6 is a graph showing the characteristics of the NO generation state, and Fig. 7 is a graph showing the load characteristics of control lever opening. This is a graph showing.

1...Housing, 2...Pump chamber, 4...
・Hydraulic pressure generator, 14... Injection timing adjustment device,
21....・Control lever shaft, 37・
... Hydraulic control device, 38 ... Oil pressure lowering passage, 39 ... Hole, 42 ... Communication groove.

Figure 1 Figure 2 Figure 3 Diagram Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A hydraulic pressure generator that generates fuel oil pressure corresponding to the engine rotation speed, an injection timing adjustment device that adjusts fuel injection timing according to the oil pressure generated by the oil pressure generator, and A fuel injection device for a diesel engine, comprising a hydraulic pressure reducing passage that lowers the hydraulic pressure, and a hydraulic control device that reduces the hydraulic pressure and delays fuel injection timing when the engine load is below a set value, the hydraulic control device as described above. A cut valve is provided in the oil pressure lowering passage to block the oil pressure lowering passage when the engine load is at a predetermined value or less, which is smaller than the above-mentioned set value, to prevent a delay in the fuel injection timing when the engine load is at a light load below the predetermined value. A diesel engine fuel injection device characterized by: 2. The fuel for a diesel engine according to claim 1, wherein the cut valve is constituted by a control lever shaft that is linked with an accelerator pedal, and the oil pressure lowering passage is cut off and cut off by a communication groove formed in the peripheral wall of the control lever shaft. Injection device.