JPS6025613B2 - Fuel injection timing adjustment method for diesel engine fuel injection pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of adjusting fuel injection timing in a diesel engine having a fuel injection pump for each cylinder.

Generally, a fuel injection pump for a diesel engine has a plunger, and as shown in FIG. ) 3 through an elevating member 4 to raise the fuel to a required pressure and supply it to the cylinder.

To adjust the fuel injection amount, although not shown, the plunger 1 is rotated by the rack twill, and the position of the diagonal notch groove provided on the outer periphery of the plunger 1 is aligned with the fuel inlet of the plunger barrel of the pump body 5. This is done by changing the Furthermore, the elevating member 4 has conventionally been constructed by attaching a roller 7 to the lower part of a cylindrical member 6, and screwing a push rod 8 having a threaded part 8a to a female threaded part at the upper part of the cylindrical part 6. It has a structure in which a rotating part 9 is provided in the middle part of the
The fuel injection timing can be adjusted using the window cover 103 (first
(In the figure, the back part is a window cover that can be opened and closed), loosen the nut 11 manually from the entrance part, and turn the push rod 8 using the turning part 9 to open the cylindrical member of the push shaft 8. 6, that is, the length of the elevating member 4 in the vertical direction. In this case, if the length of the elevating member 4 is made longer, the plunger 1 will reach the predetermined injection start position at an earlier stage of the rotation angle of the cam 3, and if the length of the elevating member 4 is made shorter, this will be the opposite. , the fuel injection timing is adjusted. The fuel injection timing adjustment using the above structure is performed regardless of the fuel injection timing, so during injection, etc.
Even when the plunger 1 is receiving back pressure due to fuel pressure, it is necessary to be able to overcome the back pressure and adjust the length of the elevating member 4.

Therefore, a large amount of adjustment power is required and a durable adjustment mechanism is required.For this reason, for example, if an automatic adjustment mechanism using a pulse motor is adopted, a large and expensive pulse motor is required. It is impractical and has few benefits, so automation has not been done in the past. This invention was proposed against the background of the above circumstances, and aims to enable adjustment of fuel injection timing with a small adjustment power, thereby facilitating the adoption of an automatic fuel injection timing adjustment mechanism. , is characterized by the fact that in diesel engines equipped with fuel injection pumps for each cylinder, it is possible to determine when all cylinders are in a non-fuel injection state, and to detect when all cylinders are in a non-injected state. ,
The purpose is to adjust the length of the extendable elevating part that pushes up the plunger driven by the fuel cam only during the all-cylinder non-injection period. This makes it possible to adjust the length of the elevating member even with a small adjustment power when no back pressure is acting on the elevating member. An embodiment of the present invention will be described below with reference to FIG. 2 and subsequent figures. In FIG. 2, 21 is a plunger, 22 is a camshaft, 23 is a cam, and 25 is a pump body, which have the same structure as in FIG. 1.

Reference numeral 24 denotes an elevating member, and this elevating member 24 is the same as the one in FIG. and a roller 2 attached to the lower part of this cylindrical portion 26.
7, and a push twill 28 having a threaded part 28a screwed into the upper part of the cylindrical member 26.

The cylindrical member 26 and the roller 27 have a structure similar to that of FIG. 1, but a driven gear 28b is fixed to the push rod 28 at an intermediate portion. Furthermore, a driving gear 29 that meshes with this gear 28b is provided.
The shaft 9, that is, the adjustment shaft 31, is connected to a pulse motor (not shown) directly or via a transmission mechanism.
Next, the fuel injection timing control mechanism will be explained based on the block diagram shown in FIG. It is installed at a crank angle position (preferably set at a position immediately after the end of injection when the fuel injection amount is maximum), detects the passage of this reflector 32, and generates a pulse (as shown in FIG. A rotation pulse transmitting device 33 is provided that transmits this pulse (referred to as a rotation pulse).

This rotational pulse transmitting device 33 is a gate pulse generating circuit 3
4, and this gate pulse generating circuit 34 inputs a pulse having an appropriate width, that is, a gate pulse as shown in FIG. There is. On the other hand, a load rotation speed detection device 36 that detects the load and rotation speed of the engine inputs signals of the engine load and rotation speed to a fuel injection timing control device 37 that performs microcomputer control, for example. , calculates the appropriate fuel injection timing based on the input engine load and rotational speed information, compares the calculation result with the actual fuel injection timing, and calculates the required amount of fuel injection timing adjustment based on the difference. The information is sent to the pulse motor drive circuit 35, and the pulse motor drive circuit 3
In 5, only when the gate pulse is input,
The number of pulse motor drive pulses (10 pulses in FIG. 4) is output to the pulse motor 38 in accordance with the required fuel injection amount adjustment amount information sent from the fuel injection timing control device 37. ing.

Next, the effect will be explained.

The rotational pulse transmitting device 33 periodically injects the optical reflector attached to the crankshaft, that is, in the case of the six-cylinder diesel engine of the embodiment, three times at equal intervals per crankshaft rotation (in each case, fuel is injected). The rotation pulse is detected (when the rotation pulse is not in the state), and each time a rotation pulse is sent to the gate pulse circuit 34, and the gate pulse circuit 34 pulses a gate pulse with an appropriate width each time this rotation pulse is input. The signal is input to the motor drive circuit 35.

On the other hand, the fuel injection control device 37 calculates the optimum fuel injection timing based on the engine load and rotation speed information that is constantly input from the load rotation speed detection device 36, and calculates the optimum fuel injection timing, which differs from the actual fuel injection timing. If so, information on the difference, that is, the required adjustment amount of fuel injection timing, is sent to the pulse motor drive circuit 35. The pulse motor drive circuit 35 selects and outputs a number of pulse motor drive pulses proportional to the required amount of fuel injection timing adjustment to the pulse motor 38 only when the gate pulse is input. In this example, a total of 10 pulse motor drive pulses, 4, 4, and 2, are output for three gate pulses during one rotation (360 degrees) of the crankshaft, and the pulse motor 38 is driven. 10
The case of rotating by the pulse amount is shown. Pulse motor 38
, the adjustment shaft 31 rotates, the driven gear 28b rotates via the drive gear 29, the push rod 28 rotates, and the screw rod 28a thereof protrudes and retracts from the cylindrical member 26, so that the elevating member The overall length of 24 is long,
Or become shorter.

If the length of the elevating member 24 becomes longer or shorter, as described above, the plunger 21 is moved at an early stage of the rotation angle of the cam 23.
reaches the predetermined injection start position, or vice versa, and the fuel injection timing has been adjusted. The above-mentioned adjustment timing is always performed in a state where no fuel is injected, and therefore in a state where no back pressure of fuel injection pressure is acting on the plunger 21. Therefore, when adjusting the push rod 28, especially when the cylindrical member 26 Even when ejecting it, it can be done with a small driving force without receiving back pressure from the fuel.

The width of the drive gear 29 is set to include the range of elevation of the driven gear 28b when the elevating member 24 is moved up and down by the cam 23, so the drive gear 29 allows the driven gear 28b to move up and down. Note that instead of the optical reflector 32,
A dielectric material is provided (for example, a protrusion may be provided at a predetermined position on the crankshaft), and when this dielectric material is passed, a change in the magnetic force generated by a permanent magnet placed at an appropriate non-rotating location is detected. The crankshaft angle may be detected by means such as.

Furthermore, it goes without saying that the method of the present invention can be applied to single-cylinder diesel engines.

As explained above, the method of the present invention adjusts the fuel injection timing by adjusting the length of the elevating member only when all the cylinders are in the non-heat injection state. Back pressure of fuel injection does not act on the elevating section, and the fuel injection timing can be adjusted with a small driving force.

Therefore, it has become extremely easy to use a pulse motor as the adjustment drive source and use microcomputer control to adjust the optimal fuel injection timing according to the engine load or rotation speed, making it extremely easy to create an automatic adjustment mechanism, which is on the verge of practical application. opened.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a roller guide portion of a fuel injection pump to explain the method of the substructure, and Fig. 2 and the following show an embodiment of the present invention. 3 are block diagrams showing the fuel injection timing adjustment mechanism, and FIG. 4 is a time chart. 21...Plunger, 22...Camshaft, 23.
... Fuel cam, 24 ... Lifting member, 25
... Pump body, 26 ... Cylindrical member, 27 ... Roller, 28 ... Push rod,
28b... Driven gear, 29... Drive gear,
31...Adjustment axis. Figure 1 Figure 2 Figure 3 Dimensions

Claims (1)

[Claims] 1. In a diesel engine equipped with a fuel injection pump for each cylinder, find the time when all cylinders are in a non-fuel injection state, insert a fuel cam between the fuel cam and the lower surface of the plunger of the fuel injection pump, and drive it by the cam. A method for adjusting fuel injection timing in a diesel engine fuel injection pump, characterized in that the length of an extendable and retractable elevating member that pushes up a plunger is adjusted only during the all-cylinder non-injection period.