JPH0513982Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a fuel injection device for a diesel engine.

(Prior Art) There are two types of in-line fuel injection pumps used in diesel engines: a double-lead type in which leads are formed on both sides of the pump plunger to determine the end of fuel injection, and a single-lead type in which leads are formed on one side. Are known.

(Problem that the invention aims to solve) Although the double lead type has excellent transient characteristics, it has the disadvantage that the amount of fuel injection decreases significantly in the high speed range under full load, and flat torque characteristics cannot be obtained. be.

On the other hand, the single lead type has less fuel loss in the high speed range under full load, and therefore can obtain flat torque characteristics with respect to rotation speed, but especially under light loads such as when idling. The effective stroke is small and the transient characteristics are poor.

An object of the present invention is to provide a fuel injection device for a diesel engine that can take advantage of the respective advantages of the double-lead type and the single-lead type.

(Means for Solving the Problems) Therefore, the present invention provides a fuel injection system for a diesel engine that includes a plunger that reciprocates inside a plunger barrel and is equipped with means for changing the rotational position of the plunger according to the load. In the device, fuel suction ports are provided on both sides of the plunger barrel, and corresponding leads are formed on both sides of the plunger, with the leads on both sides having the same angle of inclination in the low load range, and only one lead in the high load range. The angle of inclination was set small.

(Function) During the injection stroke to pump fuel, fuel injection ends when the reed communicates with the suction port, but in the low load range both reeds communicate with the suction port at the same time, resulting in the injection characteristics of both reed types. On the other hand, in a high load range, the lead with a small angle on one side communicates with the suction port, and at this point fuel injection substantially ends, resulting in a single lead type injection characteristic.

Therefore, in the low load range, the transient characteristics of the fuel are good, and in the high load range, flat torque characteristics can be obtained over the entire rotation range.

(Example) An example of the present invention will be described with reference to the drawings.

Fig. 1 shows the plunger part, which is the main part of the in-line fuel injection pump. Reference numeral 1 is a plunger barrel fixed to a pump housing (not shown), and a plunger 2 is housed inside the plunger barrel so as to be able to slide freely. Ru. The plunger 2 is reciprocated by a cam (not shown) in synchronization with the rotation of the engine, and rotates about its axis via a control rack and a control sleeve (also not shown).

The plunger barrel 1 has fuel suction ports 3A on both sides, which are symmetrical about the axis and located at the same height.
3B is formed.

These suction ports 3 are located on both sides of the plunger 2.
Leads (slanted grooves) 4A and 4B are formed symmetrically corresponding to A and 3B, respectively.

These leads 4A, 4B determine the end of fuel injection, and the leads 4A, 4B and the suction port 3
Fuel injection ends when A and 3B communicate.
The leads 4A and 4B are, as shown in the exploded views in FIGS. 2A and 2B, one of the leads 4A is a single-stage lead formed with the same inclination angle, while the other lead 4B is a one-stage lead formed with the same inclination angle. Up to this point, the inclination angle is the same as that of the lead 4A, but after that, a two-stage lead is formed with a smaller inclination angle.

Note that FIGS. 2A and 2B show the relative positional relationship with the suction ports 3A and 3B in response to the axial displacement (stroke) and circumferential displacement (load) of the plunger 2. For convenience of explanation, the plunger 2 is shown stationary and the relative positions of the suction ports 3A and 3B are changed.

The system is constructed as described above, and its operation will be explained next.

Plunger 2 descends and suction ports 3A, 3B
When opened, fuel is sucked into the plunger barrel 1. When the plunger 2 rises due to the rotation of the cam and closes the suction ports 3A and 3B, fuel injection begins. Note that until the suction ports 3A, 3B are completely closed, fuel flows back into the suction ports 3A, 3B and no injection is performed. After the suction ports 3A and 3B are closed, the fuel compressed as the plunger 2 moves upward pushes open a delivery valve (not shown) at the top of the plunger barrel 1 and is forcefully delivered to the fuel injection nozzle.

As the plunger 2 further rises, the leads 4A, 4B eventually communicate with the suction ports 3A, 3B, and the fuel in the plunger barrel 1 escapes to the low pressure suction ports 3A, 3B, ending fuel injection.

The effective stroke from the beginning of fuel injection to the end of injection changes by changing the circumferential position of the plunger 2, as also shown in FIGS. 2A and 2B. In the figure, T ₁ indicates the relationship between the suction ports 3A, 3B and the leads 4A, 4B at a partial load, and T ₂ indicates the relationship between the suction ports 3A, 3B and the leads 4A, 4B at a high load. When rotating around the axis through the piston, the leads 4A and 4B communicate with the suction ports 3A and 3B earlier than the stroke of the plunger 2 in the _T1 state, but do not communicate with the suction ports 3A and 3B until the latter half of the stroke in the _T2 state.

Therefore, when the rotational position of the plunger 2 is T ₁ under partial load, the effective stroke is small, so the fuel injection amount is small, whereas when the plunger ₂ is under high load, the effective stroke is large, so the fuel injection amount is small. becomes larger.

By the way, in the present invention, the inclination angles of the leads 4A and 4B are formed to be the same when the rotational position of the plunger 2 is in the low load range. 3A and 3B, and the fuel injection ends. Therefore, at least in a low load state, the fuel injection characteristics are double-lead characteristics, and in this region, the thrust force acting on the plunger 2 is small and the sliding resistance is small, resulting in good dynamic characteristics and good transient characteristics.

On the other hand, in the high load range (position T ₂ ) where the rotational displacement of the plunger 2 is large, in the rising process of the plunger 2, one lead 4B, which is a second stage lead, first communicates with the suction port 3B. Then, the other lead 4A communicates with the suction port 3A. Since fuel injection substantially ends when one lead 4B communicates with the suction port 4B, the fuel injection characteristic under high load becomes a single-lead characteristic.

In the case of a single lead, the release of fuel pressure at the moment it communicates with the suction port is slower than in the case of a double lead, which suppresses the drop in fuel injection amount, especially in the high rotation range, and increases speed from low to high rotation. A relatively flat torque characteristic can be obtained up to that point.

(Effects of the invention) As described above, according to the invention, in the low load range, both leads ensure good transient characteristics, and in the high load range, one lead ensures flat output characteristics with no drop in torque over the entire rotation range. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention, and FIGS. 2A and 2B are developed views of each lead. 1...Plunger barrel, 2...Plunger,
3A, 3B...Suction port, 4A, 4B...Lead.

Claims (1)

[Scope of utility model registration request] In a fuel injection device for a diesel engine that houses a plunger that reciprocates inside the plunger barrel and is equipped with means for changing the rotational position of the plunger according to the load, fuel suction ports are provided on both sides of the plunger barrel. Correspondingly, leads are formed on both sides of the plunger, and in the low load range, the leads on both sides are set at the same angle of inclination.
A fuel injection system for diesel engines that features a small inclination angle of the reed on one side only in the high load range.