Internal-combustion engines – Charge forming device – With fuel pump
Utility Patent
1999-07-22
2001-01-02
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S506000, C123S467000
Utility Patent
active
06167870
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control device and a control method for a cam driving type electronic control unit injector, and the invention particularly relates to a control device and a control method for a cam driving type electronic control unit injector for high pressure injection of a diesel engine.
BACKGROUND ART
With the improved fuel economy and power of diesel engines, a demand for environmental friendliness such as noise and emission reductions has been increasing recently. In order to obtain such contradictory performances as above at the same time, it is necessary to provide high pressure injection, improve the pattern of injection rate, and shorten the period of injection. Thus unit injectors start to be adopted. Explaining with reference to
FIG. 1
, such a unit injector receives a force from a cam
4
via components such as a roller
3
, a push rod
5
, a rocker arm
6
and the like, and injects high pressure fuel by means of a plunger
11
of a unit injector
10
.
However, as high pressure injection of the unit injector
10
is used, the load exerted by the inner pressure of the plunger
11
becomes larger, thus bending the rocker arm
6
as shown by the broken line in FIG.
1
. After finishing injection, the rocker arm
6
, which has been bent during the high pressure injection, is bent in reverse by reaction force as shown by the two-dot chain line, thereby causing a so-called jump phenomenon in which driving system parts (driving force transmitting parts) separate from the cam
4
. In this situation, the driving force transmitting parts hit the surface of the cam
4
, thereby causing an impact force. This impact not only becomes a significant source of noise, but also causes the disadvantage of severely deteriorating the durability of the driving force transmitting parts.
DISCLOSURE OF THE INVENTION
Mitigating the aforesaid disadvantage, the present invention is made, and its object is to provide a control device and a control method for a cam driving type electronic control unit injector, in which driving force transmitting parts will not separate from a cam, with less impact force and noise being caused, even when a high injection pressure is used.
A control device for a cam driving type electronic control unit injector according to the present invention is a control device for a cam driving type electronic control unit injector including a cam driving type plunger having the function of a reciprocating pump, a structure in which fuel is discharged from a plunger chamber formed at one end portion side of the plunger during an injection stroke and fuel is taken into the plunger chamber during a fuel charge stroke, and a fuel injection nozzle placed below the plunger chamber, characterized by including:
an oil reservoir communicating with a low pressure fuel source passage and a drain passage,
a feed and pressure passage for providing communication between the oil reservoir and the plunger chamber,
a valve for opening and closing the feed and pressure passage,
a first solenoid for moving the valve during the injection stroke to close the feed and pressure passage to raise a pressure in the plunger chamber,
a spring or a second solenoid, which presses the valve to open the feed and pressure passage, and
a control means for supplying a smaller current than that when the valve is moving during the injection stroke, through the first solenoid for a predetermined period after the lapse of a predetermined period of time immediately after the completion of main injection during the injection stroke to move the valve in a closing direction of the feed and pressure passage to thereby output a command for raising the pressure in the plunger chamber.
According to the above configuration, when the cam is rotated and reaches a predetermined position, the control means outputs a command to the first solenoid and operates the valve against the spring or the second solenoid to close the valve. Further as a result of the cam rotating, the plunger is pressed down to thereby carry out main injection. In this situation, large loads are exerted on the driving force transmitting parts placed between the cam and the plunger, for example, a bending load is on the rocker arm, and a compression load is on the push rod. After the lapse of the predetermined period of time immediately after the completion the main injection, specifically, before the valve is completely returned to the original position, a smaller current is supplied through the first solenoid once again to operate the valve in the closing direction for the predetermined period once again. The valve operates in the closing direction, thereby raising the pressure in the plunger chamber. As a result of the rise in pressure, for example, the load exerted on the rocker arm is not abruptly reduced to zero from the maximum load. As a result, the rocker arm is not bent in reverse, and the driving force transmitting parts are abutted to one another to be driven, thus eliminating a so-called jumping phenomenon in which the driving force transmitting parts separate from the cam. For this reason, impact force, which causes the driving force transmitting parts to hit the cam surface, does not occur, and noises caused by the impact can be prevented. Further the durability of the driving force transmitting parts is dramatically increased.
It may be suitable to include a speed sensor for detecting the speed of an engine, a position sensor for detecting an operating amount of an accelerating means of the engine, and an angle sensor for detecting the rotational angle of the cam, and the control means may receive signals from the speed sensor, the position sensor, and the angle sensor, obtain the predetermined period of time immediately after the completion of the main injection and the predetermined period during which the smaller current is supplied, and output the obtained values to the first solenoid.
According to the above configuration, the control means obtains the predetermined period of time and the predetermined period according to the engine speed, the operating amount (load exerted on the engine) of the accelerating means, and changes the predetermined period of time and/or the predetermined period during which the current is supplied through the first solenoid. As a result, the position and the magnitude of the pressure, at which the pressure in the plunger chamber is raised once again, become variable according to the engine speed and the load exerted on the engine, thus enabling to generate pressure in the plunger chamber in response to a load exerted on the driving force transmitting parts for driving the unit injector.
A control method for a cam driving type electronic control unit injector is a control method for a cam driving type electronic control unit injector in which the driving force from a cam is transmitted to a plunger of a unit injector via driving force transmitting parts including at least a push rod and a rocker arm to inject fuel by means of the plunger, characterized by including the step of:
after the lapse of a predetermined period of time immediately after the completion of main injection, producing pressure in a plunger chamber of the plunger for a predetermined period and pressing each of the driving force transmitting parts so that each of them is not separated.
According to the above configuration, after the lapse of the predetermined period of time immediately after the completion of the main injection in which the plunger is pressed down, predetermined pressure lower than that in the main injection is generated in the plunger chamber for the predetermined period. Due to the pressure, as in the aforesaid invention of the control device, the load exerted on the rocker arm is not abruptly reduced to zero from the maximum load. As a result, the rocker arm is not bent in reverse, and the driving force transmitting parts are always abutted to one another to be driven, therefore eliminating a so-called jump phenomenon. As a result, the impact force, which causes the driving force
Komatsu Ltd.
Moulis Thomas N.
Sidley & Austin
LandOfFree
Control device and control method for cam driving type... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control device and control method for cam driving type..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control device and control method for cam driving type... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469685