JPS6138335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a diesel engine, and more particularly to one in which fuel injection timing is delayed and corrected in accordance with engine load.

Generally, in diesel engines, in order to take measures against emissions, exhaust gas, noise, etc. during operation, the fuel injection timing is corrected to be delayed when the engine load is light compared to when the engine is under normal load. An injection device is provided.

As this type of fuel injection device, the one disclosed in, for example, Japanese Unexamined Patent Publication No. 53-44724, and the one shown in FIG. 1 as a general example are known. That is, in FIG. 1, 1 is the housing of the distribution type fuel injection pump, 2
3 is a hydraulic chamber formed in the housing 1; 3 is a drive shaft that rotates at half the engine speed; 4 is a feed pump 5 attached to the drive shaft 3; and 4 adjusts the oil feeding pressure of the feed pump 5. The hydraulic pressure generating device 4 is constructed of a regulating valve 6, and the hydraulic pressure generating device 4 is provided to generate fuel hydraulic pressure corresponding to the engine rotational speed and transmit it to the hydraulic chamber 2. Reference numeral 7 denotes a pump/distribution plunger fitted 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, 11 is a drive shaft 3 inside the housing 1.
The roller holder 11 is provided with the same number of rollers 12, 1 as the number of ridges on the cam surface 9a of the cam disk 9.
2, . . . are supported and held, and the rollers 12, 1
2, ......, the cam surface 9a of the cam disk 9 is pressed by the plunger spring 13, and as the cam disk 9 rotates on the roller 12, the plunger 7 is moved back and forth for suction and pressure feeding of fuel. It is configured to simultaneously perform movement and rotation for distribution. Reference numeral 14 denotes an injection timing adjustment device for adjusting the fuel injection timing, and the injection timing adjustment device 14 has a timer piston 16 that slides within a cylinder 15 formed in the housing 1. is connected to the roller holder 11 via a lever 18 that is slidable around a fixed shaft 17, and applies the hydraulic pressure generated by the hydraulic pressure generator 4 transmitted to the hydraulic chamber 2 to the pressure receiving surface of the timer piston 16. Let timer piston 1
6 is moved, and the movement of the timer piston 16 rotates the roller holder 11 via the lever 18, and the roller 12 and the cam surface 9 of the cam disk 9 are rotated.
By relatively changing the contact position with a, the fuel injection timing is adjusted by the fuel oil pressure from the oil pressure generator 4, and when the fuel oil pressure is high, the fuel injection timing is advanced, and when the fuel oil pressure is low, the fuel injection timing is adjusted. It operates to delay the fuel injection timing. Reference numeral 19 denotes a cut-off sleeve that is slidably fitted in a portion of the plunger 7 that projects into the hydraulic chamber 2 so as to open and close a cut-off port 7b that communicates with the vertical hole 7a of the plunger 7.
By sliding the cut-off sleeve 19 on the plunger 7, moving it to the left in the figure advances the opening timing of the cut-off port 7b and reducing the fuel injection amount, and conversely, moving it to the right opens the cut-off port 7b. It is provided to delay the opening timing of 7b and increase the fuel injection amount. Reference numeral 20 denotes a control lever that is linked to an accelerator pedal (not shown). A tension lever 24 is attached to the eccentric pin 22 via a governor spring 23.
The upper end of the tension lever 24 is connected, and the lower end of the tension lever 24 is pivotally supported by a pin 26 to a collector lever 25 that is pivotally supported on the housing 1. An upper end of a start spring 28 whose lower end abuts against the tension lever 24 is fixed to the upper end of the start lever 27, while the cut-off sleeve 19 is attached to the lower end of the start spring 28. A ball head pin 29 that engages with a pin hole 19a formed in the engine is provided upright, and the tension of the governor spring 23 is changed by changing the angle of the control lever 20 according to the engine load. The fuel injection amount is controlled by swinging the tension lever 24 and moving the cut-off sleeve 19 as a result of the change. 30 is a centrifugal flyweight mechanism built into the hydraulic chamber 2, and the centrifugal flyweight mechanism 30 includes a governor shaft 33 that rotatably supports a governor gear 32 that meshes with a drive gear 31 fixed to the drive shaft 3. It consists of a flyweight 35 built into a flyweight holder 34 integrated with the governor gear 32, and a governor sleeve 36 slidably attached to the governor shaft 33. By sliding the governor sleeve 36 and pressing the back of the start lever 27 with the tip of the governor sleeve 36, the cut-off sleeve 19 is moved and adjusted, and the fuel injection amount is adjusted according to the engine speed. It is something to do. Furthermore, 37 is a hydraulic control device for controlling fuel oil pressure, and the hydraulic control device 37 has a fuel return passage 38, and the fuel return passage 38 is
Governor shaft 3 of the flyweight mechanism 30
3 and the housing 1 to communicate between the hydraulic chamber 2 and the suction side of the hydraulic pressure generating device 4 via a hole 39 formed in the governor sleeve 36. This lowers the oil pressure. And the hydraulic control device 37
When the engine load is small, that is, when the angle of the control lever 20 is smaller than the set angle, the flyweight mechanism 30 moves the governor sleeve 36 to the right in the figure to connect the hole 39 of the governor sleeve 36 to the fuel return passage. The fuel return passage 38 is opened in line with the opening on the hydraulic chamber 2 side of the hydraulic chamber 2, thereby lowering the fuel oil pressure in the hydraulic chamber 2, and the injection timing adjusting device 14 is operated to delay the fuel injection timing. . In addition, 40 is a delivery valve that prevents the backflow of the fuel fed under pressure by the plunger 7, 41 is a fuel cut valve that cuts off the fuel feeding to the plunger 7,
The fuel injection device is configured as described above.

However, in such conventional fuel injection devices, the fuel injection timing is uniformly delayed even in the high rotational speed range of the engine, so there is a problem in that fuel efficiency and output performance deteriorate as a whole.

The present invention has been made in view of the above, and provides a rotation speed correction device that disables the oil pressure lowering function of the hydraulic control device only when the engine is in a high rotation region in a diesel engine fuel injection device having the above configuration. By providing this, the fuel injection timing is not delayed in the high engine speed range, which is not the normal engine speed range, and corresponds to the engine speed as usual, thereby improving fuel efficiency and output performance as a whole. The present invention aims to provide a fuel injection device for a diesel engine.

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 the fuel injection device for a diesel engine as shown in FIG. 1, there is an injection timing adjustment device 14 that adjusts the fuel injection timing using fuel oil pressure corresponding to the engine rotation speed, and an injection timing adjustment device 14 that reduces the oil pressure when the engine load is small. As shown in FIG. 2, the diesel engine fuel injection system is equipped with a hydraulic control device 37 for delaying the fuel injection timing, and is provided with a rotation speed correction device 42 that operates according to the engine rotation speed, as shown in FIG. That is, the rotation speed correcting device 42 operates on the cut valve 4 which is disposed in the fuel return passage 38 that lowers the oil pressure in the hydraulic chamber 2 and is biased in the valve opening direction by a spring 43.
4, and a hydraulic passage 45 formed in the housing 1 so as to communicate the hydraulic chamber 2 and the back surface of the cut valve 44, and transmitting the pressure of the hydraulic chamber 2 to the back surface of the cut valve 44, so that the engine rotation speed is set to the set rotation speed. In a region where the speed is higher than the number (for example, 2500 rpm), the hydraulic chamber 2 that acts on the back surface of the cut valve 44
When the pressure in the (hydraulic passage 45) overcomes the biasing force of the spring 43, the cut valve 44 closes the fuel return passage 38, disabling the oil pressure lowering function of the hydraulic control device 37, and thereby disabling the injection timing adjustment device 14. It is configured to operate normally and cancel the delay in fuel injection timing.

Next, the operation of the above embodiment will be explained.
When the engine speed is in the low-medium speed range lower than the set speed, for example 2500 rpm, the hydraulic chamber 2
The pressure within the spring 4, that is, the pressure acting on the back surface of the cut valve 44 of the rotation speed correction device 42, is small, for example, less than 5 kg/cm ² as shown in FIG.
3, the cut valve 44
does not close, and the fuel return passage 38 is kept open. Therefore, when the engine load is small, the tension of the governor spring 23 decreases, and the governor sleeve 36 moves to the right in FIG. As a result, the fuel in the hydraulic chamber 2 flows out, the oil pressure decreases, and the fuel injection timing is delayed. On the other hand, as the engine load increases, the tension of the governor spring 23 increases, causing the governor sleeve 36 to move to the left in FIG. The opening of the hydraulic chamber 2 of the fuel return passage 38 is closed, and the hydraulic pressure of the hydraulic chamber 2 is maintained at a high pressure state, preventing a delay in the fuel injection timing, and therefore, as shown in the left half of FIG. The timing is delayed and corrected according to the engine load.

On the other hand, when the engine speed increases to a high speed range exceeding the set speed (2500 rpm), the oil pressure in the hydraulic chamber 2 increases to 5 kg/cm ² or more as shown in Figure 3, and the cut valve 44 becomes larger than the biasing force of the spring 43, the cut valve 44 closes against the biasing force of the spring 43 and closes the fuel return passage 38, thereby reducing the hydraulic pressure of the hydraulic control device 37. The degraded function becomes disabled. Therefore, as shown in the right half (shaded area) of FIG. 4, the delay in fuel injection timing is canceled regardless of the engine load, and as a result, the injection timing is advanced in accordance with the engine speed.

Therefore, since the delay in fuel injection timing is canceled and the injection timing is advanced only in the high rotational speed range of the engine where output is required, fuel efficiency and output performance can be improved as a whole.

In the above embodiment, the cut valve 44 provided in the fuel return passage 38 is closed by the hydraulic pressure in the hydraulic chamber 2.
Although it may be configured with a solenoid valve that closes in the high rotation range where the engine rotation speed is higher than the set rotation speed, the structure as in the above embodiment is simpler and has a lower reliability. It is preferable.

As described above, according to the present invention, there is provided an injection timing adjustment device that adjusts the fuel injection timing using fuel oil pressure corresponding to the engine rotation speed, and an injection timing adjustment device that adjusts the fuel injection timing by lowering the oil pressure when the engine load is small. In a fuel injection system for a diesel engine equipped with a hydraulic control device for delaying the fuel injection timing, a rotation that disables a hydraulic pressure lowering function of the hydraulic control device and cancels the delay in fuel injection timing in a region where the engine speed is equal to or higher than a set rotation speed. By providing the number correcting device, it is possible to improve fuel efficiency and output performance without significantly impairing the emission performance, noise performance, etc. of the diesel engine.

In addition, if the rotation speed correcting device is configured with a cut valve provided in the fuel return passage that lowers the oil pressure in the hydraulic chamber, and a hydraulic passage that transmits the pressure in the hydraulic chamber to the cut valve, the structure becomes simpler and the operation becomes easier. This has the advantage of improving reliability.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing a conventional example, Figs. 2 to 4 illustrate embodiments of the present invention, Fig. 2 is an enlarged sectional view of main parts, and Fig. 3 shows pressure retention in the hydraulic chamber. The graph shown in FIG. 4 is an operating range diagram. DESCRIPTION OF SYMBOLS 1... Housing, 2... Hydraulic chamber, 14... Injection timing adjustment device, 21... Control lever shaft, 37... Hydraulic control device, 38... Fuel return passage, 39... Hole, 42... Rotation speed Correction device, 43...spring, 44...cut valve, 45...hydraulic passage.

Claims (1)

[Scope of Claims] 1. An injection timing adjustment device that adjusts the fuel injection timing using fuel oil pressure corresponding to the engine rotation speed, and a hydraulic control device that reduces the oil pressure and delays the fuel injection timing when the engine load is small. In the fuel injection device for a diesel engine, the engine speed correction device disables the oil pressure lowering function of the hydraulic control device to cancel the delay in fuel injection timing in a region where the engine speed is equal to or higher than a set rotation speed. A diesel engine fuel injection device characterized by: 2. The rotation speed correction device includes a cut valve provided in the fuel return passage that lowers the oil pressure in the hydraulic chamber;
2. The fuel injection device for a diesel engine according to claim 1, further comprising a hydraulic passageway for transmitting the pressure of the hydraulic chamber to the cut valve.