JP2600999B2 - Fuel injection control device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a fuel injection control device for a diesel engine.

(Prior Art) There have been many proposals for a fuel injection pump for variably controlling a fuel injection timing and an injection amount of a diesel engine in accordance with operating conditions, for example, Japanese Patent Application Laid-Open No. 61-218769.

In general, a plunger that feeds fuel is driven by a cam that synchronizes with the engine rotation, and the position of a control sleeve inserted into the plunger is adjusted to variably control the fuel injection timing. The fuel injection end timing is changed by adjusting the rotation position of the surroundings, and the fuel injection amount is controlled to increase or decrease.

(Problems to be Solved by the Invention) By the way, in such a device, the maximum injection amount at full load is also set in advance according to the engine speed and the accelerator opening. If the injection amount varies between the cylinders, fuel having a larger injection amount than the predetermined maximum injection amount is injected into a cylinder having a large injection amount, so that the smoke discharge amount increases, and the smoke level discharged as a whole deteriorates.

Therefore, an object of the present invention is to provide a fuel injection device for a diesel engine that does not increase the smoke emission amount at full load even if the injection amount varies between cylinders.

(Means for Solving the Problems) As shown in FIG. 1 (A), a first invention is a fuel injection pump 1 which is driven by a cam which rotates synchronously with an engine to pump high-pressure fuel, and an engine speed. Means 2 for presetting the maximum injection amount Qmax common to all cylinders in accordance with the above, means 3 for determining whether the engine is in the idling stable state, means for measuring the engine speed Ni for each cylinder in the idling stable state, Means 5 for calculating an injection amount Q _IDLE i for each cylinder at the time of idling corresponding to the rotation speed Ni;
Correction _{amount IDLE} i is compared with a preset idling injection quantity set value Q _SET the maximum amount from the setting value Q _SET is reduced the maximum injection amount Qmax based on the cylinder injection amount which is the maximum Means 6 for calculating ΔQ ₁ , means 7 for reducing the maximum injection amount Qmax by the correction amount ΔQ _1, and injecting the reduced maximum injection amount (for example, Qmax−Q ₁ ) into the engine. Means 8 for controlling the injection amount adjusting mechanism of the fuel injection pump 1 so as to be supplied.

As shown in FIG. 1 (B), the second invention is a fuel injection pump 1 driven by a cam which rotates synchronously with an engine to pump high-pressure fuel, and common to all cylinders based on the engine speed and the engine load. basic injection quantity Q _N means 31 for setting beforehand, as with means 32 for setting beforehand all cylinders common base excess air ratio lambda _N based on the engine speed and the engine load, all cylinders common limit air excess ratio of means 33 for presetting λmax, means 3 for determining whether or not the engine is in the idling stable state, means 4 for measuring the engine speed Ni for each cylinder in the idling stable state,
Means 5 for calculating the injection quantity Q _IDLE i for each cylinder at idle, and comparing this injection quantity Q _IDLE i for each cylinder with a preset value Q _{SET of the} injection quantity at idle, and setting this Cylinder injection quantity Q _IDLE i with the largest excess from the value Q _SET
Means 34 for calculating a correction amount △ λ for increasing the limit excess air rate λmax based on the above, a means 35 for increasing and correcting the limit excess air rate λmax with this correction amount 、 λ, It calculates a correction amount △ Q ₂ that the excess air ratio (e.g. λmax + △ λ) is reduced to the basic injection quantity Q _N based on the increased corrected limit air excess ratio is smaller than the basic air excess ratio lambda _N Means 36 and the correction amount △
A means 37 for decreasing correction of the basic injection quantity Q _N at Q _2, the weight loss corrected injection quantity Q ₂ (e.g. Q _N - △ Q ₂₎ of the fuel injection pump 1 to be supplied to the engine Means 38 for controlling the injection amount adjusting mechanism.

(Function) In the first invention, for example, when the injection amount Q _IDLE i of this cylinder becomes larger than the set value Q _{SET in a} cylinder having a large injection amount, the calculating means 6 calculates the reduction correction amount △ Q ₁ for the maximum injection amount Qmax. Is calculated.

When the correction amount △ Q ₁ only preset maximum injection amount Qmax is reduced by the correction unit 7, jetted too at full load is suppressed at high cylinder of the injection quantity.

However, when weight loss maximum injection amount Qmax by the correction amount △ Q _1, but also decreases torque produced, since reduction in torque as compared to a region small injection quantity is in the vicinity of the maximum injection amount is small, affecting the drivability Never.

In the second invention, when the injection amount Q _IDLEi of this cylinder becomes larger than the set value Q _{SET in a} cylinder having a large injection amount, the correction amount △ λ for increasing the limit excess air ratio λmax is calculated by the calculation means. .

When the limit air excess ratio λmax is increased by the correction amount △ lambda correction means 35, the reduction correction amount △ Q ₂ in calculating means 36 is increased by an amount corresponding to the correction amount △ lambda.

As a result, many weight loss amount of the basic injection quantity Q _N of the correction means 37, spouting too much at more cylinders of injection amount can be suppressed even in the second invention.

(Embodiment) First, FIG. 2 shows an example of a fuel injection pump 10, which is a so-called row type fuel injection pump (see Japanese Patent Application Laid-Open No. 61-218769). Then, the fuel in the pressurizing chamber 13 is pumped to the fuel injection nozzle 20 through the fuel valve 14.

A control sleeve 15 is mounted around the plunger 12,
The start time of the fuel pumping is determined by the position of the sleeve 15. The sleeve 15 has a fuel chamber 16 into which fuel is fed and a pressurizing chamber.
When the opening of the passage 17 is closed by the lower end of the sleeve 15 in the process of opening and closing the opening of the passage 17 provided in the plunger 12 communicating with the opening 13 toward the fuel chamber, and the plunger 12 rises, the fuel chamber The communication with the pressure chamber 16 is interrupted, and the pressure in the pressure chamber 13 starts to increase.

Further, when the port 17a branched from the passage 17 communicates with the communication port 15a provided in the middle of the sleeve 15 due to the rise of the plunger 12, the pressurizing chamber 13 communicates with the fuel chamber 16 again, and the fuel pumping ends. .

By moving the position of the sleeve 15 up and down by the position control mechanism 18, it is possible to advance or delay the fuel pumping start timing.

Further, since the branch port 17a is opened as an inclined groove around the plunger, by changing the rotation position of the plunger 12 around the axis by the rotation control mechanism 19,
The timing of communication with the passage 15a changes, and the timing of ending fuel pumping, that is, the fuel injection amount, can be changed.

According to the present invention, if there is a variation in the injection amount among the cylinders during idling stabilization, the maximum injection amount is corrected in response to this, so that there is no excessively injected cylinder.
The operation of a position control mechanism 18 of the sleeve 15 and a rotation control mechanism (injection amount adjusting mechanism) 19 of the plunger 12 is controlled by a controller 25 shown in FIG.

The controller 25 is composed of a CPU as an operation part, a ROM and a RAM as storage parts, and a microcomputer including I / O as an input / output part.

The controller 25 includes an engine speed sensor 21, an accelerator opening sensor (engine load sensor) 22, and a water temperature sensor 2.
3, the detection signals from the idle switch 24 and the like are input, and based on these, the position control mechanism 18 of the sleeve 15 and the rotation of the plunger 12 are respectively controlled so that the fuel injection timing and the injection amount are appropriately controlled. A drive signal is output to the control mechanism 19.

Here, the control operation executed by the CPU of the controller 25 will be described with reference to the flowcharts of FIG. 4 and FIG.

First, in step 1, the engine speed Ne and the accelerator opening Ac
c, the cooling water temperature Tw and the idle switch state are read, and it is determined whether or not the engine is in the idle stable state based on these data (step 2). For example, idle switch 24
Is ON, the cooling water temperature Tw is within a predetermined range, and the engine speed Ne at that time is equal to or lower than a predetermined value, it is determined that the engine is in the idling stable state, and the routine proceeds to step 3.

In step 3, an idle speed N _IDLE i (i is the cylinder number) for each cylinder is calculated, and a map is referred to from this speed N _IDLE i to obtain an injection amount (map value) Q for each cylinder at idle.
_IDLE i is obtained (step 4). FIG. 6 shows the characteristics of the map value Q _IDLE . As the amount of fuel injected into one cylinder increases, the rotational speed of the cylinder increases. Therefore, a proportional relationship is provided here.

The reason why the idle speed is measured for each cylinder is to know the variation of the injection amount at the time of full load. The variation in the injection amount during idling appears as a difference in idle speed, and as shown in FIG. 11, the injection amount has almost the same tendency at idle and at full load. This is because the variation in the injection amount at the full load can be understood from the variation in the above.

In step 5, the largest one of the map values Q _IDLE i of the idling injection amount obtained for each cylinder is selected as Q _IDLE max, and the selected idling injection amount (predetermined from the set value of the idling speed) Q _SET (Q _IDLE max−
Q _SET ) is calculated, and a correction amount ΔQ ₁ with respect to the maximum injection amount is obtained by referring to the map from the difference. When showing the characteristics of the correction amount △ Q ₁ in FIG. 7, the Q _IDLE max> Q _SET a positive value, giving a Q _IDLE max <Q negative value in _SET vice versa.

In step 6, and stores the value of the correction amount △ Q ₁ at a predetermined address in the RAM, and ends the routine of FIG. 4.

Next, in step 11, the engine speed Ne, the accelerator opening Acc, and the like are read, and a basic injection amount, a basic injection timing, and a maximum injection amount are obtained by referring to a map from these data (step 12).

As shown in FIG. 8 is a map value Q _N of the basic injection amount, based on the engine speed Ne and the accelerator opening Acc, also map values of the map values IT _N and the maximum injection amount of the basic injection timing Qmax
Are determined in advance to the optimum characteristics based on the rotational speed Ne as shown in FIGS. 9 and 10.

In step 13 reads the correction amount △ Q ₁ stored in step 6.

In step 14, the map value Q _N of the basic injection amount, a value obtained by subtracting the correction amount △ Q ₁ from the map value Qmax of the maximum injection quantity (Qm
ax− △ Q ₁ ), and if Q _N > Qmax− △ Q ₁ , it is determined that the region is not in the vicinity of the maximum injection amount, and Q _N is selected to be the injection amount Q ₁ ( Step 15).

If Q _N ≦ Qmax- △ Q ₁ in the reverse, to select the better of Qmax- △ Q ₁ as the region near the maximum injection quantity, which is referred to as injection quantity Q ₁ (step 16).

Accordingly, in the case of Q _IDLE max> Q _SET , the maximum injection amount is limited to a value smaller by the correction amount ΔQ ₁ (ΔQ ₁ > 0). That is, if there is a cylinder that is more injected than the set idle injection amount Q _SET is supposed to both cylinders is limited to the correction amount △ Q ₁ as few injection amount from the map value Qmax of the maximum injection quantity Thus, excessive spraying at full load is suppressed, and deterioration of smoke is prevented. The correction of the maximum injection amount also reduces the variation in the injection amount at the full load as shown in the right end of FIG.

However, if you reduce the maximum injection amount by the correction amount △ Q _1,
The generated torque also decreases, but as shown in FIG. 12,
In the vicinity of the maximum injection amount, the decrease in torque is smaller than that in the region where the injection amount is small, and therefore, there is no influence on drivability.

It should be noted that, if only not supplied a small injection amount than the set idle injection quantity Q _SET (In the case of Q _IDLE max <Q _SET) is, does not occur originally smoke of the deterioration of the problem at the time of full load, maximum injection quantity Is increased by the correction amount | △ Q ₁ | (△ Q ₁ <0), so that a little more torque can be extracted.

Injection amount at step 17 Q ₁ and injection timing to store IT (= IT _N) at a predetermined address and terminates the routine of FIG. 5.

Next, the embodiment of FIGS. 13 and 14 will be described. This is based on the data of the engine speed Ne, the accelerator opening Acc, and the actually detected excess air ratio λ.
Q _N , together with the basic injection timing IT _N , the basic excess air ratio λ _N ,
Advance set limits excess air ratio .lambda.max (step 32), calculates the correction amount △ Q ₂ for the basic injection quantity Q _N in accordance with the difference between these excess air ratio (λ _N -λmax) (step 35), A value (Q _N − △ Q ₂ ) obtained by subtracting the correction amount △ Q ₂ from the basic injection amount Q _N is determined as the injection amount Q ₂ (step 36).
In this example, the set idle injection amount Q
_If there is a cylinder that is injected more than _SET , the actual excess air ratio becomes smaller than a preset limit excess air ratio λmax, and the amount of smoke emission increases rapidly.

Therefore, for this case, when Q _IDLE max> Q _SET , the correction amount △ λ (△ λ>
0) (step 21), and the critical excess air ratio λmax is greatly corrected by this correction amount △ λ (step 3).
4), the correction of the limiting excess air ratio reduces the injection amount as shown in FIG. 12, thereby preventing an increase in the smoke emission amount.

In practice, the base excess air ratio lambda _N, the limit air excess ratio .lambda.max, in addition to providing the map correction amount △ Q ₂ (see Figure 16 through Figure 18), the correction amount △ in lambda of FIG. 15 Q as
The characteristics in the case of _IDLE max <Q _SET are also given.

As a result, also in this example, the same effect as in the previous embodiment is obtained, and the correction amount △ Q ₂ for the injection amount is obtained using the excess air ratio. Can be controlled more accurately.

(Effect of the Invention) In the first invention, the variation of the injection amount at full load is estimated from the rotational speed of each cylinder at idle, and the injection amount at idle of the cylinder whose maximum value is the maximum from the set value is estimated. Since the fuel injection amount of all cylinders is corrected by the correction amount determined based on the above, even if a cylinder whose injection amount fluctuates to an excessive side due to aging or the like occurs, the engine torque is not significantly impaired, and the engine torque at full load is reduced. Generation of smoke can be reliably suppressed. In addition, since the maximum injection amount of all cylinders is uniformly corrected, it is not necessary to perform injection amount control for each cylinder, and therefore, it can be easily applied to, for example, a general fuel injection pump that controls the control sleeve position uniformly for all cylinders. There is also an advantage.

In the second invention, the amount of correction for the basic injection amount is determined using the excess air ratio.
And the maximum injection amount can be controlled more precisely.

[Brief description of the drawings]

1 (A) and 1 (B) are views corresponding to claims of each invention, FIG. 2 is a sectional view of a fuel injection pump showing one embodiment,
FIG. 3 is a block diagram of the controller, FIGS. 4 and 5 are flowcharts of the same control operation, and FIGS. 6 to 10 are cylinder-by-cylinder injection amounts, maximum injection amount correction amounts, basic injection amounts, and basic injection timings, respectively. FIG. 11 is a characteristic diagram showing variations in the injection amount, FIG. 12 is a characteristic diagram showing smoke and torque with respect to the injection amount and excess air ratio, and FIGS. 13 and 14 are other characteristic diagrams. Flow chart of control operation of the embodiment, fifteenth
FIG. 18 to FIG. 18 are map characteristic diagrams of the limit excess air ratio correction amount, the basic excess air ratio, the limit excess air ratio, and the injection amount correction amount, respectively. 10 ... fuel injection pump, 18 ... sleeve position control mechanism,
19 …… Plunger rotation control mechanism (injection amount adjustment mechanism), 21
…… Engine speed sensor, 22 …… Accelerator opening sensor, 23 …… Water temperature sensor, 24 …… Idle switch, 25…
…controller.

Claims (2)

(57) [Claims] 1. A fuel injection pump driven by a cam which rotates synchronously with an engine to pump high-pressure fuel, a means for presetting a maximum injection amount common to all cylinders in accordance with an engine speed, and an idle stable state. Means for determining whether or not, an engine speed for each cylinder in an idling stable state, a means for calculating an injection amount for each cylinder during idling corresponding to this speed, and an injection amount for each cylinder. Is compared with a preset set value of the injection amount during idling,
A means for calculating a correction amount for reducing the maximum injection amount based on the cylinder-by-cylinder injection amount having the largest excess amount from the set value; a means for reducing the maximum injection amount with the correction amount; Means for controlling an injection amount adjustment mechanism of the fuel injection pump such that the reduced injection amount of the maximum injection amount is supplied to the engine. 2. A fuel injection pump driven by a cam which rotates synchronously with the engine to pump high-pressure fuel, a means for presetting a basic injection amount common to all cylinders based on an engine speed and an engine load, and an engine. Means for presetting a basic excess air ratio common to all cylinders based on the engine speed and engine load, means for presetting a critical excess air ratio common to all cylinders, and means for determining whether the engine is in an idle stable state. Means for measuring the engine speed for each cylinder in the idling stable state, means for calculating the injection amount for each cylinder during idling corresponding to this speed, and setting the injection amount for each cylinder at the idle time set in advance. Comparing with a set value of the injection amount, a correction amount for increasing the limit excess air ratio is calculated based on the cylinder-by-cylinder injection amount having the largest excess amount from the set value. Means for increasing the critical excess air ratio by the correction amount, and increasing the critical excess air ratio when the increased excess critical air ratio is smaller than the basic excess air ratio. Means for calculating a correction amount for reducing the basic injection amount based on the correction amount, means for reducing and correcting the basic injection amount with this correction amount, and a means for supplying the reduced injection amount to the engine. Means for controlling an injection amount adjusting mechanism of the fuel injection pump.