JPH05272377A - Fuel injection device - Google Patents

Abstract

PURPOSE:To hold a drive voltage and responsiveness of a solenoid valve of a fuel injection pump, and an injection pressure and injection quantity of the fuel injection pump constant respectively by correcting drive pulses applied to the solenoid valve in accordance with a voltage drop between the solenoid valve and its drive circuit. CONSTITUTION:A control unit performs predetermined actions at a desired injection quantity computation part 47, a cam angle converting part 48, and a valve closing time computation part 49 based on output signals from a rotation detection part 41 and an accelerator opening detection part 42 respectively. A pulse generation control part 59 adds output timing signals from the valve closing time computation part 49 and a delay time computation part 51, and decides an output timing for a drive pulse to be outputted to a drive pulse forming part 52, that is the optimum timing of starting fuel injection. In this case, the drive pulse of the drive pulse forming part 52 is corrected at a drive pulse correction part 53 based on an output signal from a power supply voltage detection part 45. It is thus corrected in accordance with a voltage drop between a solenoid valve 20 and a drive circuit 54 to drive it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device in which the amount of fuel injected to an internal combustion engine is adjusted by controlling the opening / closing of a solenoid valve provided in a fuel supply passage leading to a compression chamber of a fuel injection pump. Regarding

[0002]

2. Description of the Related Art As a fuel injection device of this type, for example, the one shown in Japanese Patent Laid-Open No. 63-21346 is known, and the injection amount is determined by the actual closing time of the solenoid valve. The seating of the solenoid valve is detected, and the actual valve closing time is counted from this seating timing.

For this reason, the fuel injection device is provided with an actual valve closing detection unit for detecting the timing at which the electromagnetic valve is actually closed in response to the application of the drive pulse. The valve detection unit has a voltage detection circuit for obtaining a voltage signal corresponding to a current waveform flowing in the exciting coil in response to the drive pulse, and a differentiation circuit for differentiating the output voltage from the voltage detection circuit. ..

Therefore, in response to the abrupt decrease in the level of the exciting current, the differential circuit obtains a differential output indicating the timing, and the actual valve closing timing is obtained from this differential output. is there. by this,
A drive voltage is applied to the solenoid valve for a time obtained by adding the valve closing delay time of the solenoid valve and the actual valve closing time, so that a desired injection amount can be secured.

[0005]

However, the length of the electric wire (wire harness) that connects the drive circuit that outputs the drive pulse and the solenoid valve differs for each cylinder due to the engine layout, and the difference in the DC resistance is different. It may be so large that it cannot be ignored in terms of injection performance.

As a result, the drive pulse applied to each solenoid valve is reduced in the drive voltage by the voltage drop of the wire harness, so that the valve closing delay time varies among the solenoid valves, and the valve closing delay time is also varied. Since the preflow of each solenoid valve differs depending on the type, the injection pressure and the injection amount of the fuel injection pump vary.

Therefore, the present invention is to provide a fuel injection device which corrects a drive pulse applied to each solenoid valve in accordance with a voltage drop of a wire harness leading to each solenoid valve.

[0008]

Therefore, the present invention is
A fuel injection pump provided for each cylinder, and a solenoid valve for adjusting a communication state between the high pressure chamber and the low pressure chamber between a high pressure side and a low pressure side communicating with a compression chamber of the fuel injection pump are provided. , Calculating the output time of the target injection amount from at least the accelerator opening and the engine speed, and opening and closing the solenoid valve by a drive pulse determined by the valve closing delay time of the solenoid valve and the output time of the target injection amount In the fuel injection device that adjusts the injection amount of the fuel injection pump that is supplied during the internal combustion period, the drive pulse applied to the solenoid valve arranged in each cylinder is used to drive each solenoid valve and the solenoid valve. It is provided with a drive pulse correcting means for correcting in accordance with the voltage drop between them.

[0009]

Therefore, in the present invention, the drive pulse correction means corrects the drive pulse applied to each solenoid valve in accordance with the voltage drop in the wire harness connecting the solenoid valve and the drive circuit for driving the solenoid valve. Therefore, in response to a voltage drop that increases in proportion to the distance from the drive circuit, a drive pulse corrected to fill this voltage can be applied to each solenoid valve, so the drive that flows to the solenoid of each solenoid valve is driven. The current can be made constant, and the above-mentioned problems can be achieved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

The fuel injection system shown in FIG. 1 is provided for each cylinder of a diesel engine, for example, and has a unit injector type injection pump 1 for injecting fuel into the cylinder. This injection pump 1 includes a cylinder 3 formed on a base of a plunger barrel 2 and a plunger 4
Is slidably inserted, and a spring 6 is interposed between the plunger barrel 2 and a tappet 5 connected to the plunger 4, so that the plunger 4 is constantly urged in a direction away from the barrel (upward direction in the figure). is doing.

A cam formed on a drive shaft (not shown) is in contact with the tappet 5, so that the plunger 4 can be reciprocated in cooperation with the spring 6 by the rotation of the drive shaft connected to the engine. The plunger reciprocates to perform compression and suction.

A holder portion 7 is assembled with a holder nut 8 at the tip of the plunger 4, and a nozzle 10 is connected to the holder portion 7 via a spacer 9 with a retaining nut 11. A spring storage chamber 12 is formed in the holder portion 7, and the spring storage chamber 1
The needle spring of the nozzle (not shown) is pressed downward in the figure by the nozzle spring 13 housed in No. 2. The structure of the nozzle is known per se, and when high-pressure fuel is supplied through the high-pressure passage 14 described below, the needle valve is opened and the fuel is injected from the injection hole formed at the tip of the nozzle.

The high pressure passage 14 is formed in the plunger barrel 2 and has a discharge hole 16 whose one end opens into the compression chamber 15 at the tip of the plunger, a communication hole 17 formed in the holder portion 7, and a valve passage formed in the spacer 9. 18, and the nozzle 10
Is formed by a fuel outlet hole (not shown).

The compression chamber 15 formed in the valve housing 21.
The fuel supply passage 34 for supplying fuel to the first fuel supply passage 34a is supplied with fuel from the fuel inlet 35,
Annular recess 34b, second fuel supply passage 34c, sliding hole 38 described below, valve body storage chamber 27, third fuel supply passage 34
The fuel is supplied from the fuel inlet 35 to the compression chamber 15 through the fuel supply passage 34.

The solenoid valve 20 includes a valve housing 21 having a rod 22 integrally extending to the side of the plunger barrel 2.
Is slidably inserted into the sliding hole 38 formed in
The valve housing 21 at the lower end of the valve seat 24 is provided with a valve seat 24 that abuts the poppet type valve body 23 at the rod end, and a header 25 screwed to the valve housing 21 so as to cover the valve body 23 allows a stopper 26 for the valve body 23 to be provided. And a valve body accommodating chamber 27 that communicates the sliding hole 38 with the valve housing 21.

Further, the rod 22 is inserted into a holder 28 screwed to the side opposite to the header 25 of the valve housing 21, and the holder 28 and a solenoid accommodating barrel connected to the holder 28 via a holder nut 29. It is connected to the armature 31 between 30 and 30. The armature 31 faces the solenoid 32 held by the solenoid housing barrel 30.

The holder 28 is provided with a valve body 23 and a valve seat 24.
Spring 33 in order to always urge it away from
Are normally stored and held, and normally the valve body 23 is separated from the valve seat 24, and the solenoid 32 is energized to drive the valve body 23 in the direction of abutting the valve seat 24.

An annular groove 39 is formed in the sliding hole 38, and the third fuel supply passage 34d is connected to the annular groove 39. A second fuel supply passage 34c communicates with the valve accommodating chamber 27, and fuel is constantly supplied and filled through the passage 34c, and the fuel supply passage 34c has a pressure of about 5 kg / cm ² .
Therefore, fuel is supplied to the compression chamber 15 from the sliding hole 38, the annular groove 39, and the third fuel supply passage 34d during the return stroke of the plunger 4 when the valve body 23 is separated. The pressure at that time is about 5 Kg / cm ² .

When the solenoid valve 20 is energized, that is, when the valve body 23 is seated on the valve seat 24, the third fuel supply passage 34d is formed.
The fuel already supplied is compressed in the compression chamber 15 by the downward stroke of the plunger 4 and supplied to the nozzle. And the solenoid valve 20
By the separation of the valve element 23 from the valve seat 24, the compression chamber 15 is opened, and the compression action ends.

The control of the solenoid valve 20 is controlled by a control unit 40 as shown in FIG.
A D converter, a multiplexer, a microcomputer, etc., and is attached to a drive shaft, a rotation detection unit 41 that detects the rotation state of the engine, an accelerator opening detection unit 42 that detects the depression amount (accelerator opening) of the accelerator pedal, and a drive shaft. A reference pulse generator 43 that generates a pulse each time the drive shaft reaches the reference angular position, a needle valve lift sensor 44 that detects the lift timing of the needle valve, a power supply voltage detector 45 that detects the power supply voltage (battery voltage), Each signal from the control cylinder detector 46 for detecting the cylinder to be controlled (control cylinder) is input.

In FIG. 2, the processing executed by the control unit 40 is shown in the form of a functional block diagram for the sake of convenience. Hereinafter, description will be given based on this block diagram. Outputs from the rotation detecting section 41 and the accelerator opening degree detecting section 42 will be described. A signal is input to the target injection amount calculation unit 47, and based on these input signals, the optimum target injection amount that matches the engine operating conditions at this time is calculated from predetermined map data and output as a target injection signal. ..

This target injection signal is supplied to the cam angle converter 48.
The cam angle required to obtain the optimum target injection amount is calculated according to the engine speed based on the predetermined map data and is output as a cam angle signal.

The valve closing time calculator 49 receives the cam angle signal and converts it into a time required for the cam to rotate by the cam angle calculated by the cam angle converter 48. That is,
Here, the time (valve closing time) Tq required to inject the target injection amount is calculated from the closing of the electromagnetic valve 20 that starts the injection.

The valve closing time Tq calculated here does not include the delay time Tv accompanying the valve movement until the valve body 23 whose valve seat 24 is separated is completely seated. For this reason,
The drive pulse width Td actually required to drive the solenoid valve 20 is formed by the sum of Tq and Tv (Td = Tq.
+ Tv).

The pulse generation control unit 50 includes a valve closing time Tq calculated by the valve closing time calculating unit 47 and a delay time calculating unit 5.
The output timing of the drive pulse Dp that is added to the delay time Tv calculated in 1 and output to the drive pulse forming unit 52,
That is, the optimum timing of the fuel injection start is determined by the reference signal output from the reference pulse generator 43 and the needle valve lift sensor 44.
Timing signal output from the rotation detection unit 4
1 based on the rotation signal output from 1.

This drive pulse Dp is sent to the drive pulse forming section 52, where the reference drive pulse Dr is formed. This drive pulse forming unit 52 is, for example, shown in FIG.
The one-shot pulse generator 56 shown in FIG.
AND circuit 57, high frequency generator 58, and OR circuit 59
The drive pulse Dp from the pulse generation controller 50 shown in FIG. 3B is input to one of the one-shot pulse generator 56 and the AND circuit 57.

Further, the high frequency shown in FIG. 3C output from the high frequency generator 58 is input to the other side of the AND circuit 57, whereby the output signal L of the AND circuit 57 is generated.
o has a high frequency only during the period given by the drive pulse Dp as shown in FIG. This output signal Lo is O
It is input to one of the R circuits 59, and the other end of the OR circuit 59 has the one-shot pulse generator 56 shown in FIG.
The one-shot pulse Po having a predetermined width and having the same rising timing as the drive pulse Dp output by the above is input.

[0029] This by the output signal from the OR circuit 59, as shown in FIG. 3 (f), the a duty ratio larger (100% in this case) period (Force period T _P), a small driving duty ratio Period with pulse (limit period T
_The drive pulse Dr composed of _L ) is obtained. The drive pulse Dr is formed so as to shorten the seating delay time of the solenoid valve by the drive pulse of the forced period and facilitate the detection of the seating timing of the solenoid valve by the drive pulse of the limited period.

As shown in FIG. 4, the drive pulse Dr is corrected by a drive pulse correction section 53 described below according to a predetermined program and sent to the drive circuit 54. The drive circuit 54 includes a solenoid valve 20 arranged in each cylinder.
_1, 20 _2, ..., 20 _n solenoids 32 _1, 32 _2, ...
.., 32 _n to the wire harness 56 _1, 56 _2, ..., 56
Field drop transistor FET _1, F connected via _n
ET _2, ..., FET _n , and this FET _1, FET _2, ...
.. Resistors R _{1 and} R for detecting the current flowing through FET _n
, ..., R _n, and the drive pulses Dr _1, Dr _2, ...
, Dr _n is applied to the gates of FET _1, FET _2, ..., FET _n to make each circuit conductive.

[0031] Incidentally, the resistor R _1, R _2, · · ·, each resistor R ₁ by the voltage across R _n, R _2, · · ·, current through R _n is detected, from the current value The seating detection unit 55 detects the seating timing of the solenoid valve by detecting the minimum value of the current value due to the seating of the solenoid valve.

The correction of the drive pulse Dr performed by the drive pulse correction section 53 will be described below with reference to the flowchart of FIG. 5 and will be described with reference to this flowchart.

The correction of the drive pulse starting from step 200 is performed in step 210 by the control cylinder detecting section 4 described above.
The number of the cylinder to be controlled this time, which is detected by the control cylinder 6, is input (kth cylinder), and step 220
At, the value α of the power supply voltage (battery voltage) V _B is input, and at step 230, the drive pulse Dr is input.

In step 240, the length of the compulsory period T _P is calculated from the power supply voltage V _B based on the characteristics of the kth cylinder according to the map shown in FIG. 6 (a). Specifically, when the control cylinder is the first cylinder, the compulsory period T _P1 is obtained from the value α of the power supply voltage V _B based on the characteristic indicated by k = 1. Similarly, in the case of the second cylinder, the compulsory period T _P2 is obtained, and in the case of the nth cylinder, the compulsory period T _P2.
This is what gives _Pn . As a result, the drive circuit 54
The farther from the cylinder, the longer the compulsory period can be obtained.

In step 250, the duty ratio of the drive pulse within the time limit T _L is calculated from the power supply voltage V _B based on the characteristics of the kth cylinder according to the map shown in FIG. 6B. Specifically, when the control cylinder is the first cylinder, the duty ratio D ₁ is obtained from the value α of the power supply voltage V _B based on the characteristic indicated by k = 1. Similarly, in the case of the second cylinder, the duty ratio D ₂ is obtained,
In the case of the nth cylinder, the duty ratio D _n is obtained. As a result, a larger duty ratio is obtained for a cylinder located farther from the drive circuit 54.
Note that steps 240 and 250 surrounded by the one-dot chain line in the figure are the driving pulse correction value calculation step 280.

In step 260, the length T _P1, T of the forced period T _P calculated in step 240 is calculated.
_P2, ..., T _Pn , a limit period T _L determined from the compulsory period T _P and the driving pulse width Td, and the step 25
Duty ratios D _{1 and} D within the limit period calculated at 0
_The drive pulse Dr is corrected by _2, ..., D _n .
Specifically, when the control cylinder is the first cylinder closest to the drive circuit 54, as shown in FIG. 9A, the drive pulse D
r has a compulsory period T _P1 and a limit period T _L1 and is corrected to a drive pulse Dr ₁ having a duty ratio of D ₁ within the limit period, and the control cylinder is the n-th cylinder farthest from the drive circuit 54. In this case, as shown in FIG. 9B, the drive pulse Dr
_Has a compulsory period T _Pn and a limit period T _Ln, and is corrected to a drive pulse Dr _n having a duty ratio of D _n within the limit period.

This corrected drive pulse Dr _1, Dr _{2 ,.}
.., Dr _n are driven by the drive circuit 54 in step 270.
Is output to. As a result, each solenoid valve 20
_{1, 20} 2, ..., the driving voltage applied to 20 _n, the wire harness 56 _1, 56 _2, ..., after the voltage drop by 56 _n, each of the solenoid valves 20 _1, 20 _2, ... .., 32 _n of the solenoids 32 _1, 32 _2, ..., 32 _n become constant at the stage of being applied to the solenoids 32 _1, 32 _{2 ,} .
_The drive current flowing through _n becomes constant, and each solenoid valve 20 _1, 20
The response of _2, ..., 20 _n can be made constant.

In the above embodiment, the correction of the drive pulse having the compulsory period and the limited period has been described. However, when the drive pulse Dp is directly applied to the drive circuit, the step shown by the one-dot chain line in FIG. In 280, the drive voltage is calculated. Specifically, the drive voltage is calculated from the value α of the power supply voltage V _B based on the characteristic of the kth cylinder shown in FIG. 7. For example, in the case of the first cylinder, k
= 1, the drive voltage Vd ₁ is calculated, in the case of the second cylinder, the drive voltage Vd ₂ is calculated from the characteristic of k = 2, and in the case of the nth cylinder, the drive voltage Vd _n Is calculated, and the drive voltage increases as the operation proceeds to the nth cylinder.

Accordingly, in step 260, when the control cylinder is the first cylinder closest to the drive circuit 54,
The drive pulse Dp is corrected to the drive pulse Dp ₁ whose drive voltage is Vd ₁ as shown in FIG. 10A, and when the control cylinder is the nth cylinder farthest from the drive circuit 54, the drive pulse Dp is , As shown in FIG. 10 (b), the drive voltage Vd is sequentially higher for each cylinder than that for the first cylinder.
_Since it is corrected to the driving pulse Dp _n of _n , the same effect as that of the above-described embodiment can be obtained.

When the drive pulse Dr is composed of a pulse having a predetermined duty ratio, the duty ratio is calculated in step 280.
Specifically, the duty ratio of the drive pulse is calculated from the value α of the power supply voltage V _B based on the characteristic of the kth cylinder shown in FIG. For example, in the case of the first cylinder, the duty ratio D ₁ is calculated from the characteristic of k = 1, and in the case of the second cylinder, the duty ratio D _{2 of the} drive pulse is calculated from the characteristic of k = 2. in the case of the n-th cylinder is to duty ratio D _n of the drive pulse is calculated.

Accordingly, in step 260, if the control cylinder is the first cylinder closest to the drive circuit 54,
The drive pulse Dr is corrected to the drive pulse Dr ₁ having the duty ratio D ₁ as shown in FIG. 11A, and when the control cylinder is the nth cylinder farthest from the drive circuit 54, the drive pulse Dr is As shown in FIG. 11B, the drive pulse Dr _n is corrected to have a duty ratio D _n that is set to be larger for each cylinder than the duty ratio of the first cylinder, and the same effect as that of the above-described embodiment is obtained. Is something that can be done.

[0042]

As described above, according to the present invention, the voltage drop in each wire harness between the solenoid valve provided with the fuel injection pump for each cylinder and the drive circuit for driving this solenoid valve is dealt with. By correcting the ability of the drive pulse applied to each solenoid valve, the drive voltage of each solenoid valve can be made constant, so that the response of each solenoid valve can be made constant, and each fuel injection pump The injection pressure and the injection amount can be kept constant.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a fuel injection device according to an embodiment of the present invention.

FIG. 2 is a functional block diagram illustrating a control unit of the fuel injection device according to the embodiment of the present invention.

FIG. 3A is a circuit diagram showing an example of a drive pulse forming unit according to an embodiment of the present invention, and FIGS. 3B to 3F are timing charts of output signals.

FIG. 4 is an electric circuit diagram showing an example of a drive circuit and a circuit leading to each solenoid valve.

FIG. 5 is a flowchart showing control of a drive pulse correction unit.

FIG. 6A is a characteristic line map diagram showing the relationship between the power supply voltage in each cylinder and the compulsory period, and FIG. 6B is a characteristic curve showing the relationship between the power supply voltage in each cylinder and the duty ratio of the restriction period. It is a line map figure.

FIG. 7 is a characteristic line map diagram showing the relationship between the power supply voltage and the drive voltage in each cylinder.

FIG. 8 is a characteristic line map diagram showing the relationship between the power supply voltage and the drive voltage in each cylinder.

FIG. 9 is the first cylinder (a) and the n-th cylinder when the duty ratio of the drive pulse within the forced period and the limited period is corrected.
It is a timing chart figure of the drive pulse of No. cylinder (b).

FIG. 10 is a first cylinder (a) when the drive voltage is corrected.
6 is a timing chart of drive pulses applied to the n-th cylinder (b).

FIG. 11 is a timing chart of drive pulses applied to the first cylinder (a) and the nth cylinder (b) when the duty ratio is corrected.

[Explanation of symbols]

 20 Solenoid Valve 40 Control Unit 45 Power Supply Voltage Detection Unit 46 Control Cylinder Detection Unit 50 Pulse Generation Control Unit 51 Delay Time Calculation Unit 52 Drive Pulse Forming Unit 53 Drive Pulse Correction Unit 54 Drive Circuit

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[Procedure amendment]

[Submission date] June 4, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Shinagawa 3-13-26, Yasumi-cho, Higashimatsuyama, Saitama Prefecture Zexel Higashimatsuyama Factory

Claims (1)

[Claims] 1. A fuel injection pump arranged for each cylinder,
Between the high pressure side and the low pressure side communicating with the compression chamber of the fuel injection pump, there is provided a solenoid valve for adjusting the communication state between the high pressure chamber and the low pressure chamber, and the target injection is performed based on at least the accelerator opening and the engine speed. Of the fuel injection pump that calculates the output time of the amount of fuel and supplies the fuel to the internal combustion period by opening and closing the electromagnetic valve with a drive pulse determined by the valve closing delay time of the electromagnetic valve and the output time of the target injection amount. In the fuel injection device that adjusts the amount, the drive pulse applied to the solenoid valve arranged for each cylinder is
A fuel injection device comprising drive pulse correction means for correcting according to a voltage drop between each solenoid valve and a drive circuit for driving the solenoid valve.