JPS59165856A - Fuel injection pump for internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain an optimum injection rate for pilot injection and main injection, by providing a pump for pilot injection only independently of a pump for main injection, and controlling such plural pumps separately according to engine operating conditions. CONSTITUTION:A fuel injection pump has plungers 3 and 33 and high pressure chambers 4 nd 34, and comprises a first pump A and a second pump B. A cam lift time t1 of one cam face of a first set of cam ring 8 is set shorter than a cam lift t2 of one cam face of a secons set of cam ring 38. A fuel injection rate in the first set is set smaller than that in the second set. Adjustment of a fuel injection timing is effected by adjusting rotational positions or phases about central axes of the cam rings 8 and 38 with respective inner-surface cam ring position adjusting devices 40A and 40B. The devices 40A and 40B are controlled by timer pistons 43 and 44.

Description

TECHNICAL FIELD The present invention relates to a fuel injection pump for injecting and supplying fuel to a compression ignition internal combustion engine such as a diesel engine, and more particularly to an improvement in a fuel injection pump that performs pilot injection.

BACKGROUND ART In compression ignition internal combustion engines such as diesel engines, there is an ignition delay of the injected fuel, so combustion occurs explosively, which tends to increase combustion noise. This tendency becomes more noticeable during idling or when the engine is under low load, when combustion tends to deteriorate.

Therefore, when the engine load is low, etc., prior injection (
A known method is to perform a pilot injection to form a combustion chamber atmosphere that facilitates ignition during the main injection.

A conventional example of this type is MTZ20 issued in May 1959.
-5, pages 142 to 144, or "Diesel Engine" published by Nissan Motor Co., Ltd. in 1980.

However, these conventional models were configured to perform two-stage fuel injection during the compression stroke of the plunger, one for pilot injection and one for main injection, using a cam with two convex shapes. There is a risk that a phenomenon (the plunger separating from the cam) may occur, and the cam speed diagram cannot be made steep, or the connection between the first cam ridge and the second cam ridge is necessary to smoothly connect the first cam ridge and the second cam ridge. Since slow compression is performed in the engine, there is an inconvenience that sufficient fuel compression cannot be achieved at high speeds.

Purpose: In order to eliminate the disadvantages of the conventional device described above, the present invention configures a pump dedicated to pilot injection independently of a pump for main injection, and controls the plurality of pumps independently from each other according to engine operating conditions. In particular, it is an object of the present invention to enable easy control of optimum injection rates for pilot injection and main injection.

SUMMARY OF THE INVENTION To achieve this, the present invention provides a plurality of independent plunger type pongs that rotate and slide inside the inner cam ring to perform a pumping action, and also provides an inner cam ring position that independently adjusts the phase of each set of inner cam rings. The first set of pumps has a shorter cam lift period and a lower injection rate than the other second set of pumps, and is configured exclusively for Byron ff injection. Based on the output signal of the means, the respective inner cam ring position adjusting devices are actuated to adjust the mutual cam lift period to the extent that the cam lift period of the first set of pumps is within the cam lift period of the second set of pumps. A control circuit is provided to control the speed and speed.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a distribution type fuel injection pump, in which a drive shaft 1 is driven to rotate at a speed equal to the engine rotational speed, and drives a rotary shaft 2 to rotate through a spline connection. As shown in detail in FIG. 2(A), the rotary shaft 2 has a plurality of plungers 3 that can freely slide back and forth in the radial direction.
are stored in the radial direction. A high pressure chamber 4 is formed between these plungers 3. A suction boat 5 and a distribution boat 6 that communicate with the high pressure chamber 4 and open on the outer periphery of the rotary shaft 2 are formed.

On the other hand, fuel in a fuel tank (not shown) is pumped up via a feed pump, sucked into the transfer pump 11, and fed under pressure into the pump chamber 10. The pressure-fed fuel is passed through a fuel passage 12 to an electromagnetic opening/closing fuel cut valve 13.
When the suction passage 14 coincides with the suction boat 5 of the rotary shaft 2, it is introduced into the high pressure chamber 4 through the pressure feeding passage 15.

An inner cam ring (hereinafter referred to as a cam ring) 8 is disposed on the outside of the 1 lander 3 via a row 27. The cam ring 8 has a cam face 8a formed on its inner peripheral surface, and when the plunger 3 revolves as the rotary shaft 20 rotates, the plunger 3 passes through the roller 7 when the roller 7 opens on the cam ridge. are moved toward each other in the centripetal direction, and the high-pressure fuel in the high-pressure chamber 4 is discharged through the pressure-feeding passage 15. When the distribution boat 6 coincides with the distribution passage 21 communicating with each injection nozzle, the delivery pulp 22
through which fuel is pumped to the corresponding injection valve. A plurality of distribution passages 21 are provided corresponding to the fuel injection valves disposed in each cylinder of the engine, and the inner end opening 211L is formed around the inner peripheral surface of the cylinder 23 in which the rotary shaft 2 rotates. They are arranged and opened in the direction.

On the other hand, another set of plungers 33, a row 231, an inner cam ring (hereinafter referred to as a cam ring) 38, and a high pressure chamber 34 having substantially the same configuration as the above are provided.
(See Figure (B)), by the configuration of these two sets of plungers, etc., the fuel injection rate characteristic can be obtained as a composite characteristic of the fuel injection rate based on the actions of the two sets of plunger pumps.

In particular, the pumps made up of the former set of plungers 3, etc. will be referred to as the first set of pumps A1, and the latter set of pumps made up of the plungers 33, etc. will be referred to as the second set of pumps B.

As shown in FIG. 5, the cam lift period t1 of one cam face of the first set of cam rings 8 is made smaller than the cam lift period t2 of one cam face of the second set of cam rings 3B. cam ring 8, 3
The injection amount (oil supply amount), that is, the injection rate at the cam angle determined by the cam lift of No. 8, the diameter of plunger 3, 330, and K is also designed to be smaller in the first set than in the second set. At this time, the first set of pumps A is used exclusively for pilot injection, and the second set of pumps B is used for main injection only.

Regarding adjustment of fuel injection timing, the cam rings 8, 3
The rotational position, that is, the phase, of the center shaft rotation of No. 8 is adjusted by inner cam ring position adjustment devices 40A and 40B, respectively.

That is, the devices 40A, 40B include a timer histone 4 at the outer end of a rod 41.42 connected to a cam ring 8.38.
3.44 are connected to the timer pistons, and the fuel pressure in the pump chamber 10 is transmitted to the timer pistons through the pressure oil passages 47, respectively, to the timer pistons 43.43.
The pressure oil passages 47 guided to the 44 are connected to the low pressure pump chambers 10
It opens and closes on and off to the low pressure passage 50 that communicates with the timer piston 43, and controls the on/off time ratio (duty) to maintain the optimum fuel pressure for the engine operating condition.
or 44 to adjust the positions of the cam rings 8 and 38 to control the compression stroke timing of the plungers 3 and 330, that is, the fuel injection timing. Such control is performed by inputting an output signal from an engine operating state detection device consisting of an engine rotational speed sensor N, an engine load sensor T that detects the fuel injection amount, etc. to a control circuit C such as a microcomputer, and determining the optimum fuel injection timing. In order to obtain the inner cam ring position corresponding to , the predetermined duty of the timer control valves 45 and 46 is looked up, and an output corresponding to the read υ value is supplied to the timer control valves 45 and 46. .

This control is performed independently for each timer control valve 45,46.

Note that 48 and 49 are compression springs that press and bias the timer pistons 43 and 44, respectively.

The pressure feeding passage 15 that communicates and connects each of the high pressure chambers 4 and 34 with the distribution port 6 is opened on the outer peripheral surface of the shaft via a relief passage 51 formed in the four-tally shaft 2, as shown in FIG. The relief port 52 is connected to the relief port 52. A control sleeve 53 disposed on the outer periphery of the rotary shaft 2 and freely sliding in the direction of the axis O has a cut-off port 54 .
When the pressure coincides with the relief port 52, the high pressure fuel in the pressure feeding passage 15 is relieved into the low pressure pump chamber 10, and the other relief ports 52 are closed. The control sleeve 53 is displaced in the axial direction of the shaft by an actuator such as a step motor 55, and the step motor 55 controls the amount of displacement of the control sleeve 53 according to the engine operating state by the control circuit C. .

Therefore, when the fuel in the high pressure chamber 4°34 is fed under pressure by the plungers 3 and 33, the control sleeve 53
As long as the relief port 52 is closed, when the distribution port 6 and one of the distribution passages 21 are aligned, the fuel is fed under pressure to the injection nozzle of the corresponding cylinder, and is injected into the combustion chamber. As the rotary shaft rotates 20 times, the cut-off boat 54 of the control sleeve 53 and the relief port 52 coincide with each other, and at this stage, the high-pressure fuel in the pressure passage 15 moves the relief port 52 and the cut-off boat 54. Since the fuel is relieved into the low-pressure pump chamber 10 through the injected fuel, the pressure of the injected fuel decreases rapidly, the fuel injection nozzle closes, and fuel injection ends.

That is, the communication timing between the cut-off boat 54 and the relief port 52 is the fuel injection end time, and the fuel injection amount is controlled by the fuel injection end time.

Next, a control circuit C that acts on the inner cam ring position adjustment devices 40A and 40B to control the compression timing of the plunger 3.33, that is, the fuel pumping timing will be explained.

FIG. 6 shows the overall configuration of the control circuit C, in which the engine rotation speed sensor N and the engine load sensor T (in the case of this embodiment, the accelerator pedal depression angle sensor that detects the required load of the engine driver) are output from the engine rotation speed sensor N and the engine load sensor T. The operating state detection signal is input to the Kugata processing circuit 61 of the control circuit C. The input signal is input to the central processing circuit (CPU) and read only memory (ROM).
) and the required injection amount and injection timing stored in advance in a random access memory (RAM) are determined by table lookup, and then arithmetic processing is performed. The calculated value is output as a duty value to a step motor drive circuit 63 and timer control valve drive circuits 64 and 65 via an output processing circuit 62 to control the step motor 55 and timer control valves 45 and 46, respectively.

To explain the central processing circuit (CPU) of the control circuit C in detail using FIG. 7, the total pJt deviation calculation unit 11
is calculated by looking up the total required injection amount Q stored in the ROM in advance from the engine rotational speed f-N and the output value of the engine load sensor T.

The pilot injection amount calculation device T2 is connected to each of the above-mentioned sensors N+Q.
The actual pilot injection amount q, which varies depending on changes in , is calculated. That is, the amount of fuel pumped by the first set of pumps A is determined by the cam lift of its cam ring 80 and the effective area of the plunger 3, so it is a substantially constant value. The fuel pressure in the high pressure chamber 4 changes depending on the pump rotation speed, that is, the engine rotation speed, due to the influence of viscous resistance and the like. Therefore, the actual pumping amount will be different, so this is stored in advance in the RO11/] to know the actual pumping amount.

Then, these values are input to the differential amplifier 73, and a necessary and sufficient main injection amount (Q-q) is calculated by correcting the change in the pilot injection amount q, and the step motor drive circuit is adjusted according to the calculated value. 63 to operate the step motor 55 and move the control sleeve 53 in its axial direction. As a result, the open position of the relief port 52 of the cut-off port 54 is adjusted, and the end of injection of the main injection amount pumped by the second set of pumps is controlled, thereby adjusting the main injection amount and thus the total injection amount.

However, here, the output of the pilot injection amount calculation device 72 is inputted to one terminal of the differential amplifier T3 via the selection circuit T4. When the selection circuit T4 detects the total injection amount Q, the engine rotation speed N, and the engine operating state, for example, the high speed rotation and high load region, the selection circuit T4 changes the pilot injection amount q signal that had been output until then to 0 level. and output it.

Both the total injection amount Q signal and the engine rotational speed N signal are input to a pilot injection timing calculation device 81 and a main injection timing calculation device 82.

The pilot injection timing calculation device 81 uses these N.

QReceives two input signals and stores them in ROM in advance.
A value proportional to the duty value of the pilot timer control valve 45 corresponding to the pilot injection timing is calculated by table lookup, and the calculated value is input to the comparator 83.

Then, this input value is compared with the triangular wave signal output from the triangular wave signal generator 84, and the power transistor 4 interposed in the drive circuit 45a of the pilot timer control valve 45 is
A pulse signal such that the duty ratio of the timer control valve 45 becomes smaller as the pilot injection timing advances is inputted to the base terminal of the control valve 5b to control on/off of the control valve 45.

On the other hand, the main injection timing calculation device 82 calculates a duty value proportional to the duty value of the main injection timer control valve 46 corresponding to the main injection timing stored in advance in the ROM based on the total injection amount Q and the engine rotational speed N. The value is calculated by table lookup, and the set value is input to the comparator 83. Then, similarly to the pilot system, the triangular wave signal output from the triangular wave signal generator 84 and the input value are compared, and the main injection timer control valve 4
A pulse signal that causes the duty value of the timer control valve 46 to become smaller as the main injection timing advances is input to the base terminal 60 to control on/off of the control valve 460.

Next, the operation will be explained using FIG.

The cam lift timing of the cam ring 80 in the first set of pumps in the low load (for example, idle link/no load) region is also advanced by the pump angle corresponding to the engine operating state than the cam lift timing of the cam ring 38 in the second set of pumps. For this reason, pilot injection P is performed prior to main injection M, and the main injected fuel is slowly burned without ignition delay, reducing combustion noise and reducing NOx components in the exhaust gas.

At this time, the total injection amount Q can be small due to the low load, but since the pilot injection amount is almost specified, the differential amplifier 7
In step 3, the output value corresponding to the main injection amount becomes small, and the step motor 55 is operated accordingly, and the relief boat 52 and the cut-off boat 54 are made to match in the most area at the end of the main injection cam lift. Reduce the main injection amount.

The cam profile of the cam ring 8 is preferably formed so that the pilot injection rate rises more rapidly than the main injection. This increases the initial injection pressure during pilot injection, efficiently atomizes the injected fuel, promotes vaporization of the fuel in the combustion chamber, ignites the pilot injected fuel before main injection, and delays the ignition of the main injected fuel. can be almost eliminated.

Medium-speed rotation medium load (for example, road load) region In this region, pilot injection is not performed, but the pilot injection partially overlaps the above-mentioned portion of the main injection, making the entire injection into one injection. In order to prevent ignition delay in the main part (the main injection part by the second set of pumps), the injection rate of the initial injection prior to the main part is lowered to improve the combustion atmosphere of most of the fuel in the main part. Improving the noise level and NOx emission level through rapid combustion. At this time, the main injection amount by the second set of pumps is increased by the total injection amount increase, and by the action of step 55, the end of main injection is delayed compared to when there is no load.

High-pressure injection is performed for a short period of time to ensure output. At this time, if the injection rate becomes the so-called front stage, which is the above-mentioned dog, the noise level etc. will deteriorate, so it is necessary to make the injection rate as high as possible in the latter stage, which is the so-called rear stage.

Therefore, the cam lift of the pilot injection cam ring 80 is included in the cam lift period of the second set of main injection cam rings 38 so that the full lift position of the first set of pilot injection cam rings 8 is near the entire injection path timing. Controls injection timing.

In particular, the cut-off port 54 and the relief port 5
2, that is, the injection end timing at which fuel injection is not substantially performed even if there is a cam lift of the cam rings 8, 38, is different from the low and medium load range ib, the cam lift of the first set of pilot injection cam rings 8. Set during the period.

Therefore, in this case, the selection circuit 74 detects such an operating range, converts the output value from the pilot injection amount calculating device T2 to O level, and inputs the output value to the differential amplifier T3. Therefore, the output of the differential amplifier T3 corresponds to the total injection amount Q, υ,
The step motor 55 is activated to increase the main injection amount due to the cracking. If the selection circuit 74 were not present, even though the pilot injection amount was cut by the injection path Q, the uncut total pilot injection amount signal would be input to the differential amplifier 73 and the difference from the total injection amount Q would be calculated. , control is performed using this as the requested main injection amount, which may lead to a shortage of the main injection amount and the total injection amount, leading to a lack of output. However, if the stored value of the required total injection amount in the total injection amount calculation device 71 is set to a value corrected by the cut amount of the pilot injection amount, the selection circuit 74 can be omitted.

Note that in this embodiment, the first. Although this was done using the second two sets of pumps, it goes without saying that the injection rate can be controlled more precisely using three or more sets of pumps.

Effects As described above, according to the present invention, a plurality of plunger type pumps that perform a pumping action using an inner cam ring are provided,
Among these, the first set of pumps is configured exclusively for pilot injection by having a shorter cam lift period and a smaller injection rate than the other pumps of the second set, and the injection period for the pilot is the main injection period for the second set of pumps. Since the cam lift periods of each pump are independently advanced within a certain range before the injection period, pilot injection in the low load range and arbitrary injection rate control in the medium and high load ranges can be performed easily and accurately. This can improve combustion and improve noise, emission levels and power characteristics.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the injection pump of the present invention;
Figure 2) is a cross-sectional view taken along the line A-A in Figure 1; Figure 1 is an exploded side enlarged view showing the injection amount control section, Figure 5 is a cam lift curve diagram of Figure 1, and (A) is the cam lift curve of Figure 1.
FIG. 6 is a block diagram showing an example of the control circuit of FIG. 1, FIG. 7 is a detailed diagram of the same, and FIG. 8 is a detailed diagram of the same. FIG. 3 is a cam rib and injection rate characteristic diagram according to engine operating conditions, showing an example of the operation of the embodiment. A...First set of pumps B...Second set of pumps 2
... Rotary shaft 3, 33 ... Plunger 4, 34 ... High pressure chamber 5 ... Suction port small 6
...Distribution boat 8,38...Cam ring 10
... Pump chamber 40A, 40B ... Inner cam ring position adjustment device 43.44 ... Timer piston 4
5.46...Timer control valve 52...Relief bow) 53...Control three 7' 5
4... Cut-off boat 55... Step motor N... Engine rotation speed sensor T... Engine load sensor Q... Total required injection amount C... Control circuit patent
Applicant Nissan Motor Co., Ltd. Agent Patent Attorney Fujio Sasashima Figure 2 41 48 Figure 4 @ 4 Figure 5 (A) CB)

Claims (1)

[Claims] A plurality of plunger type pumps are provided which rotate and slide inside the inner cam ring to pump the injected fuel to be supplied to the injection valve, and an inner cam ring position adjustment device is provided which independently adjusts the phase of the inner cam ring of each set. In the fuel injection pump that performs fuel injection by combining the pumping actions of the plurality of pumps, the pump of the first set has a shorter cam lift period and a smaller injection rate than the other pumps of the second set. It is configured exclusively for pilot injection, and acts on each of the inner cam ring position adjustment devices based on the output signal of the engine operating state detection means provided in the internal combustion engine,
A fuel injection pump for an internal combustion engine, characterized in that a control circuit is provided for controlling the advancement or retardation of mutual cam lift periods within a range in which the cam lift periods of the pumps of the pair are within the cam lift periods of the second pump.