JP2516084Y2 - Fuel injection pump - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a fuel injection pump used in a diesel engine, etc., and in particular, due to a malfunction of the device or the like, the plunger exceeds the normal operating range and reaches the maximum effective stroke position. In this case, the present invention relates to a fuel injection pump that can automatically reduce the fuel injection amount.

[Prior Art] A fuel injection pump shown in FIG. 3 (a) is generally known. As shown in the figure, a plunger b is provided in a cylindrical plunger barrel a so as to be able to move up and down, and a compression chamber c is formed. A spill port d is bored in the plunger barrel a to introduce fuel into the compression chamber c. The fuel introduced from the spill port d into the compression chamber c is compressed by the up-and-down movement of the plunger b and is sent under pressure to a fuel injection nozzle (not shown).

In order to make the amount of fuel pumped to the fuel injection nozzle variable, a lead portion e is formed on the surface of the plunger b and is obliquely cut along the axial direction. As shown in FIG. 3 (b), the plunger b having such a lead portion e causes the compressed fuel to flow from the spill port d when the lead portion e coincides with the spill port d during the upward compression stroke. A leak will occur and the pumping of fuel will end.

Therefore, as shown in FIG. 4, the plunger b is rotated in the circumferential direction by the rack and pinion mechanism f to relatively change the matching position between the lead portion e and the spill port d. The effective stroke g of the plunger b shown in (4) is changed to make the amount of fuel pumped variable to adjust the amount of fuel injection. That is, when the rack h of the rack and pinion mechanism f is moved in the increasing direction in the figure, the effective stroke g of the plunger b is increased to increase the fuel injection amount, and when it is moved in the decreasing direction, the fuel injection amount is decreased. Become.

[Problems to be Solved by the Invention] By the way, as shown in FIG. 5, a conventional fuel injection pump in which the fuel injection amount is variable depending on the position of the rack h is required at the full load of the engine. The maximum fuel injection amount j that can be injected is set to be considerably larger than the fuel injection amount i. Therefore, when the rack h moves beyond the full load rack position k, which is the upper limit position of the normal range, to the mechanical upper limit position 1 of the rack that hits the rack stopper, an excessive amount of fuel is generated when an abnormality occurs in the device for some reason. Since the fuel is injected into the engine, abnormally thick black smoke is emitted from the vehicle, which poses a danger to the following vehicle, and there is a possibility that the engine body and the injection system may malfunction.

For example, in a fuel injection pump having an electronic governor for controlling a rack h shown in FIG. 4 by a solenoid motor, a target rack position and a rack position which are normally determined from an accelerator opening and an engine speed are detected. The actual rack position obtained from the rack sensor is compared, and the solenoid motor is controlled so as to eliminate these deviations to obtain an appropriate fuel injection amount. However, in the case where the rack sensor fails, in order to prevent the vehicle from becoming inoperable and allowing it to travel to a repair shop by itself,
The target engine speed determined from the accelerator opening is compared with the actual engine speed, and if the target engine speed is smaller than the actual engine speed, the rack h is moved to its mechanical upper limit position 1 shown in FIG. If the target engine speed is greater than the actual engine speed, the solenoid motor is controlled so as to move the rack h to the mechanical upper limit position m so that the vehicle can manage itself.

That is, when the rack sensor fails, the fuel injection amount is alternately changed to the maximum amount and the minimum amount by performing ON-OFF control in which the rack h is alternately moved to its mechanical upper limit position 1 and its lower limit position m. , The vehicle was in a state where it could be self-propelled. However, as shown in FIG. 5, at the mechanical upper limit position 1 of the rack h, the fuel injection amount j at that time is set to be considerably larger than the fuel injection amount i required at the full load of the engine. As a result, excessive fuel will be injected into the engine, and abnormally thick black smoke will be emitted from the vehicle, obstructing the visibility of the following vehicles and causing a danger, and there is also a possibility that malfunctions may occur in the engine body and the injection system. .

Therefore, conventionally, when such a rack sensor malfunctions, the driver once gets out of the vehicle, opens the engine room, and adjusts a rack stopper that regulates the mechanical upper limit position of the rack. Such work outside the vehicle is extremely dangerous especially when the rack sensor fails on a highway.

By the way, as a means for limiting the maximum amount of fuel injection to a range required by the engine, there is Jikkai 55-1942 "Fuel injection device for diesel engine". However, in this fuel injection device, the effective stroke of the lead portion of the plunger is constant from the maximum output position of the engine to the end point of the fuel increasing direction. At the end point of, the same amount of fuel is injected as at the maximum output of the engine regardless of the operating state of the engine, and the problem of excessive fuel injection still occurs.

The object of the present invention devised in consideration of the above circumstances is to automatically reduce the fuel injection amount when the plunger reaches the maximum effective stroke position beyond the normal operating range due to a device failure or the like. A fuel injection pump that can be used.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is configured to obliquely form a plunger that moves up and down in a barrel so that part of pressurized fuel leaks into a spill port formed in the barrel. When the lead portion, the rack for rotating the plunger around its axis in order to make the effective stroke of the lead portion spill port variable, and the sensor for detecting the position of the rack fail, the rack is mechanically moved. In a fuel injection pump equipped with an electronic governor that switches between an upper limit position and a lower limit position to ensure traveling, a maximum of the lead end that matches the spill port when the rack reaches the mechanical upper limit position. A leak groove having an effective stroke smaller than the effective stroke is formed continuously with the maximum effective stroke position.

[Operation] According to the above configuration, when the plunger reaches the maximum effective stroke position due to a failure of the rack sensor, the effective stroke at that time is less than the maximum effective stroke due to the leak groove formed continuously at the maximum effective stroke position. Becomes a small stroke, and the fuel injection amount automatically decreases.

That is, in this case, the leak groove coincides with the spill port to provide a small effective stroke, thereby preventing the excessive injection of fuel.

[Embodiment] An embodiment of the present invention will be described with reference to the accompanying drawings. First
As shown in the drawing, a plunger 2 is provided in a cylindrical plunger barrel 1 so as to be able to move up and down, and a compression chamber 3 is defined by the plunger barrel 1 and the plunger 3. A spill port 4 is bored in the plunger barrel 1 for introducing fuel into the compression chamber 3.
The fuel introduced from the spill port 4 into the compression chamber 3 is compressed by the vertical movement of the plunger 2,
It is adapted to be pressure-fed to a fuel injection nozzle (not shown).

In order to adjust the amount of fuel pumped to the plunger 2,
A lead portion 5 is formed that leaks a part of the pressurized fuel into the spill port 4 and variably determines the effective stroke. As shown in FIG. 1, the lead portion 5 is formed by cutting the surface of the plunger 2 obliquely in the axial direction.

Therefore, the plunger 2 having the lead portion 5 is rotated in the circumferential direction by the rack and pinion mechanism 6 to relatively change the coincidence position between the lead portion 5 and the spill port 4, thereby making an effective stroke of the plunger 2. Changes and the amount of fuel pumped is adjusted.

That is, when the rack 7 of the rack and pinion mechanism 6 is moved in the ON direction, the effective stroke gradually increases in accordance with the moving amount, the pumping amount increases, and the fuel injection amount gradually increases. Conversely, if the rack 7 is moved in the OFF direction, the fuel injection amount will gradually decrease.

A feature of the present invention is that a leak groove 9 is formed which is continuous with the maximum effective stroke position 8 of the lead portion 5 and determines a stroke position smaller than this. As shown in FIG. 1, the leak groove 9 is continuous with the maximum effective stroke position 8 which is the end portion of the lead portion 5, and is directed toward the compression chamber 3 side along the axial direction of the plunger 2. Is engraved on the surface of.

Therefore, as shown in FIG. 1, when the rack 7 is moved in the ON direction so that the leak groove 9 and the spill port 4 coincide with each other, a part of the pressurized fuel in the compression chamber 3 becomes small. The fuel injection amount that leaks from the spill port 4 through the leak groove 9 that determines the effective stroke and gradually increases until the rack 7 moves in the ON direction suddenly decreases.

The relationship between the position of the rack 7 of the fuel injection pump and the effective stroke of the plunger 2 is shown in FIG. As shown in the figure, in the normal range of the fuel injection pump, the fuel injection amount gradually increases with the movement of the rack 7 in the ON direction, but the rack machine in which the rack 7 hits the rack stopper beyond the normal range. When moving to the target upper limit position 10, the fuel injection amount 11 at full load of the engine is generated by the leak groove 9 formed continuously at the maximum effective stroke position 8.
The injection amount is reduced to about 12

That is, as shown in FIG. 1, the state in which the leak groove 9 and the spill port 4 coincide with each other is the mechanical upper limit position 10 of the rack 7 shown in FIG. 2, so that the rack 7 cannot move further in the ON direction. It has become. Then, during normal operation, the rack 7 moves within the normal range shown in FIG. 2 in order to adjust the fuel injection amount according to the accelerator opening and the engine speed.

The operation of this embodiment having the above configuration will be described.
When the rack 7 moves to the mechanical upper limit position 10 of the rack that hits the rack stopper beyond the rack position 13 at the time of full load of the engine, which is the upper limit position of the normal range shown in FIG. 2, due to a device failure or the like, FIG. As shown in Fig. 2, the leak groove 9 and the spill port 4 are in agreement, and as shown in Fig. 2, the effective stroke is small, and the fuel injection amount at that time is automatically half the injection amount 11 at full engine load. Injection amount 12
Decrease to.

By reducing the fuel injection amount in this manner, it is possible to prevent the occurrence of black smoke discharge and malfunction of the engine body and the injection system due to the excessive fuel injection.

For example, in a fuel injection pump equipped with an electronic governor for controlling the rack 7 shown in FIG. 1 by a solenoid motor, if the function of detecting the most important position of the rack 7 is impaired, the vehicle cannot run. Rack 7 in order to prevent
The fuel injection amount is controlled by performing ON-OFF control for alternately moving the engine to the mechanical upper limit position 10 and the mechanical lower limit position 14.

If such an injection pump as shown in FIG. 1 and FIG. 2 is adopted as the fuel injection pump, the fuel injection amount at that time at the mechanical upper limit position 10 of the rack 7 is automatically adjusted by the leak groove 9 to the entire engine. Since the injection amount 12 is reduced to about half of the injection amount 11 at the time of load, it is possible to prevent the discharge of black smoke and the occurrence of malfunctions of the engine body and the injection system without excessive fuel injection.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects can be exhibited.

When the plunger reaches the maximum effective stroke position beyond the normal operating range due to a rack sensor failure, the fuel injection amount can be automatically reduced by the leak groove formed continuously at this maximum effective stroke position. It is possible to prevent the discharge of black smoke and the occurrence of defects in the engine body and the injection system due to the excessive fuel injection amount.

[Brief description of drawings]

FIG. 1 is a perspective view of an essential part of a fuel injection pump showing an embodiment of the present invention, FIG. 2 is an injection characteristic view of the fuel injection pump shown in FIG. 1, FIGS. 3 (a) and 3 (b). ) Is a cross-sectional view of a main part of a fuel injection pump showing a conventional example, FIG. 4 is a partial perspective view of the conventional fuel injection pump, and FIG. 5 is an injection characteristic view of the conventional fuel injection pump. In the figure, 2 is a plunger, 4 is a spill port, 5 is a lead portion, 8 is a maximum stroke position, and 9 is a leak groove.

Claims (1)

(57) [Scope of utility model registration request] 1. A lead portion obliquely formed on a plunger moving up and down in a barrel for leaking a part of pressurized fuel to a spill port formed in the barrel, and an effective stroke of the lead portion with respect to the spill port. In order to make it variable, when the rack that rotates the plunger around its axis and the sensor that detects the position of the rack fail, the rack is switched between its mechanical upper limit position and its mechanical lower limit position to ensure traveling. In a fuel injection pump with a formula governor,
When the rack reaches the mechanical upper limit position, a leak groove that becomes an effective stroke smaller than the maximum effective stroke is formed continuously at the maximum effective stroke position at the end of the lead portion that matches the spill port. And fuel injection pump.