JPH08319872A - Fuel injection timing control device of fuel injection pump for diesel engine - Google Patents

Abstract

PURPOSE: To provide stable controllability with good response for the fuel injection timing using a timer piston. CONSTITUTION: A high pressure chamber 21 and a low pressure chamber 23 at the two ends of a timer piston 8 are put in communication with each other through passages 25-1, 25-2, and there the first control valve 26 is installed. The second control valve 27 is installed on passages 20-1, 20-2 which puts the high pressure chamber 21 in communication with a pump chamber 4 (the discharge side of a feed pump 3). When the difference between the actual injection timing and the target injection timing is below the specified value, the first and second control valves 26, 27 are both closed. When the difference is over the specified value and the actual injection timing is advanced from the target, the first control valve 26 is opened while the second 27 is closed. When the difference is over the specified value and the actual injection timing is retarded from the target, the first control valve 26 is closed while the second 27 is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection timing control device for a diesel engine fuel injection pump.

[0002]

2. Description of the Related Art In a conventional diesel engine distributed fuel injection pump, a timer piston is provided as a fuel injection timing control member, and the fuel injection timing is controlled according to the moving position of the timer piston. There is. (November 1, 1984, Grand Prix published "Latest Technology for Diesel Passenger Cars", pages 132-133, and Showa
Published by Sankaido on June 10, 63, "Diesel Fuel Injection" 203
Pp. 204) Here, at the one end side of the timer piston, there is a high-pressure chamber into which high-pressure fuel (pressure depends on pump speed) pumped by the feed pump is guided through the orifice. A low-pressure chamber is formed on the other end side and communicates with the suction side (suction chamber) of the feed pump.

Further, a passage for connecting the high pressure chamber and the low pressure chamber is provided, and an electromagnetic control valve is provided in this passage. The opening and closing of the control valve is always performed by duty control, and the pressure of the high pressure chamber is controlled by controlling the amount of fuel flowing from the high pressure chamber to the low pressure chamber by the duty ratio. In this way, the pressure difference between the high pressure chamber and the low pressure chamber is controlled, and the position of the timer piston is controlled by the balance with the spring that has been applied to the timer piston in advance to control the fuel injection timing.

[0004]

However, in such a conventional fuel injection timing control device, since the timer piston position is adjusted by constantly flowing fuel from the high pressure chamber to the low pressure chamber, hunting is prevented. In addition, it is necessary to provide an orifice in the passage that connects the pump chamber and the high pressure chamber, and as a result, there is a problem that the responsiveness deteriorates.

Further, since the high pressure chamber and the low pressure chamber are always in communication by constantly flowing the fuel from the high pressure chamber to the low pressure chamber, the timer piston position changes due to the driving reaction force of the plunger (cam), There is a problem that the fuel injection timing changes. Further, since the pump chamber and the high pressure chamber are always in communication with each other, the position of the timer piston also fluctuates due to the pressure fluctuation in the pump chamber, and the fuel injection timing also fluctuates.

Further, since the control valve is always driven by duty, there are problems such as an increase in power consumption, an increase in noise, and deterioration of valve durability. The present invention aims to solve such conventional problems.

[0007]

Therefore, in the invention according to claim 1, in the fuel injection timing control device of the fuel injection pump for a diesel engine, the timer is controlled according to the moving position of the timer piston. A high-pressure chamber that communicates with the discharge side of the feed pump at one end of the piston,
A low pressure chamber communicating with the suction side of the feed pump is formed at the other end, and a passage communicating with the high pressure chamber and the low pressure chamber is provided, and a first control valve is provided in the passage, and the feed pump is provided. A second control valve is provided in a passage that communicates the discharge side with the high-pressure chamber, and a control device that controls opening and closing of the first and second control valves is provided.

According to another aspect of the present invention, the control device includes target injection timing means for calculating a target fuel injection timing based on engine operating conditions, and actual injection timing detection means for detecting an actual fuel injection timing. And comparing means for comparing the target injection timing with the actual injection timing, and valve control means for controlling the opening and closing of the first and second control valves according to the comparison result.

In the invention according to claim 3, the valve control means includes fixed control means for closing both the first and second control valves when the difference between the actual injection timing and the target injection timing is less than a predetermined value. A retard control means for opening the first control valve and closing the second control valve when the difference between the actual injection timing and the target injection timing is greater than or equal to a predetermined value and the actual injection timing is ahead of the target injection timing. When the difference between the actual injection timing and the target injection timing is a predetermined value or more and the actual injection timing is retarded from the target injection timing, the first control valve is closed and the second control valve is opened. And a control means.

In the invention according to claim 4, the valve control means drives at a duty ratio according to a difference between the actual injection timing and the target injection timing when the first and second control valves are opened. It is characterized by being. In the invention according to claim 5,
The valve control means includes start-time detection means for detecting the start-up of the engine, and forced advance control means forcibly closing the first control valve and opening the second control valve when the engine is started. It is characterized by being configured.

[0011]

According to the first aspect of the invention, the high pressure chamber and the low pressure chamber at both ends of the timer piston are provided with a passage communicating with them, and the first control valve is interposed in this passage, and the feed pump A second control valve is provided in a passage communicating between the discharge side (pump chamber) and the high pressure chamber, and the first and second control valves are opened and closed.

When it is desired to fix the fuel injection timing, both the first and second control valves are closed to seal the fuel in the high pressure chamber and fix the position of the timer piston. As a result, even if the driving reaction force of the cam is received or the pressure in the pump chamber changes, it is possible to prevent the position of the timer piston from changing. When retarding the fuel injection timing, in order to move the timer piston to the high pressure chamber side,
The first control valve is opened to allow the fuel in the high pressure chamber to escape to the low pressure chamber, and the second control valve is closed to reduce the flow rate from the pump chamber to the high pressure chamber to 0 to reduce the pressure in the high pressure chamber. In this case, by closing the passage from the pump chamber to the high pressure chamber, the pressure in the high pressure chamber is quickly reduced, and the moving speed of the timer piston can be improved.

When advancing the fuel injection timing, in order to move the timer piston to the low pressure chamber side, the first control valve is closed to make the flow rate from the high pressure chamber to the low pressure chamber zero, and The pressure in the high pressure chamber is increased by opening the control valve and guiding the high pressure fuel in the pump chamber to the high pressure chamber. In this case, since there is no orifice, the pressure in the high pressure chamber rises quickly and the moving speed of the timer piston can be improved.

According to the second aspect of the present invention, the target injection timing of fuel is calculated based on the engine operating conditions, the target injection timing and the actual injection timing are compared, and the first and first fuel injection timings are determined according to the comparison result. By controlling the opening and closing of the second control valve, the injection timing can be controlled with good responsiveness. In the invention according to claim 3, when the difference between the actual injection timing and the target injection timing is less than the predetermined value, the injection timing can be stably fixed by closing both the first and second control valves. it can.

The first control valve is opened and the second control valve is opened when the difference between the actual injection timing and the target injection timing is a predetermined value or more and the actual injection timing is advanced from the target injection timing. Is closed, the actual injection timing can be quickly retarded to the target injection timing. Further, when the difference between the actual injection timing and the target injection timing is a predetermined value or more and the actual injection timing is behind the target injection timing, the first control valve is closed and the second control valve is opened. As a result, the actual injection timing can be quickly advanced to the target injection timing.

According to the fourth aspect of the present invention, when the first and second control valves are opened, the duty ratio corresponding to the difference between the actual injection timing and the target injection timing is used to drive the injection timing control. Overshoot or undershoot can be prevented, and control convergence can be improved. In the invention according to claim 5, by forcibly closing the first control valve and opening the second control valve at the time of starting the engine, the fuel injection timing is promptly controlled to the advance side at the time of starting, Good startability is obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of a distributed fuel injection pump for a diesel engine. In the fuel injection pump 1, a feed shaft 3 in a pump case is driven by a drive shaft 2 which is rotationally driven by an engine, and the feed pump 3 draws fuel from a fuel tank (not shown) to pump the pump in the pump case. Guided to Chamber 4.

A plunger 6 having a cam disk 5 connected to the drive shaft 2 so as to be movable in the axial direction thereof is coaxially arranged, and the plunger 6 is arranged in a cylinder 7.
High-pressure pumping is performed by reciprocating inside. The timer piston 8 is provided on the flange surface of the cam disk 5.
A plurality of cams corresponding to the number of cylinders that come into contact with the rollers held by the position-adjustable roller holder 9 are formed at equal intervals, and the plunger 6 is rotated every time the cams pass over the rollers by the rotation of the cam disk 5. Move in the direction. Therefore, while the plunger 6 rotates coaxially with the drive shaft 2,
Reciprocates as many as the number of cams per unit rotation.

When the plunger 6 is in the intake stroke to the left in the figure, the fuel in the pump chamber 4 is sucked from the suction port 10 on the cylinder 7 side into the pumping chamber 12 through the suction groove 11 of the plunger 6, 6 moves to the right in the drawing, the fuel in the pumping chamber 12 is compressed and the plurality of discharge ports on the cylinder 7 side from the distribution groove 13 of the plunger 6 are compressed.
It is guided to one of 14 and is pressure-fed from the delivery valve 15 to the fuel injection nozzle 16 through the high-pressure pipe.

Here, by changing the rotational position of the roller holder 9 by adjusting the position of the timer piston 8, the start timing of the reciprocating movement of the plunger 6 changes, so that the fuel injection timing (injection start) is changed. You can Therefore, the fuel injection timing (injection start) can be controlled by adjusting the position of the timer piston 8 as described later.

A control sleeve 17 is slidably inserted in a portion of the plunger 6 outside the cylinder 7, and when the cutoff port 18 of the plunger 6 is exposed outside the inner peripheral surface of the control sleeve 17, pumping is performed. The fuel in the chamber 12 leaks from the cutoff port 18 and the injection ends. Therefore, by adjusting the position of the control sleeve 17 with an electronic governor (not shown), the end of injection, that is, the injection amount can be controlled.

Reference numeral 19 in the drawing denotes a fuel cut valve for stopping the engine, which can stop the fuel supply by closing the intake port 10. Next, the fuel injection timing control device by adjusting the position of the timer piston 8 will be described in detail. At one end of the timer piston 8, the pump chamber 4 (the discharge side of the feed pump 3) and the passages 20-1, 20-
2 forms a high-pressure chamber 21 that communicates with the other end, and at the other end, a low-pressure chamber 23 that communicates with the suction side of the feed pump 3 through a passage 22.
Is formed. A spring 24 that biases the timer piston 8 toward the high pressure chamber 21 is housed in the low pressure chamber 23 side.

Further, passages 25-1 and 25-2 which connect the high pressure chamber 21 and the low pressure chamber 23 are provided, and an electromagnetic first control valve 26 is provided in the passages 25-1 and 25-2. I am doing it. Further, an electromagnetic second control valve 27 is provided in the passages 20-1 and 20-2 that connect the pump chamber 4 and the high pressure chamber 21. The first and second control valves 26 and 27 are controlled to be opened and closed by a control unit 28 having a microcomputer as a control device.

For this control, the control unit 28
Signals are input to the various sensors. A rotation sensor 29 is provided as the various sensors. The rotation sensor 29 is an electromagnetic pick-up type sensor that is opposed to a signal disk plate having teeth for signal generation on the outer periphery attached to the drive shaft 2 of the fuel injection pump 1, and the drive shaft of the fuel injection pump 1. A pulse signal is generated each time 2 rotates by a predetermined angle, the crank angle is detected from this pulse signal, and the engine speed (fuel injection pump speed) Ne is determined from the cycle of the pulse signal (or the number of pulses within a predetermined time). Can be detected.

Further, an accelerator sensor 30 for detecting the accelerator opening as the engine load Q is provided. Also,
A needle valve lift sensor 31 that detects a needle valve lift for detecting the actual injection timing is attached to the fuel injection nozzle 16.
The control unit 28 also has a starter signal (3
2) etc. have been entered.

Next, the operation will be described. When it is desired to fix the fuel injection timing, both the first and second control valves 26 and 27 are closed to seal the fuel in the high pressure chamber 21 and fix the position of the timer piston 8. As a result, it is possible to prevent the timer piston from moving due to the driving reaction force of the cam as shown in FIG. Further, it is possible to prevent the timer piston position from fluctuating due to the pressure fluctuation in the pump chamber.

When the fuel injection timing is retarded, the timer piston 8 is controlled to move to the high pressure chamber 21 side. That is, the first control valve 26 is opened to allow the fuel in the high pressure chamber 21 to flow into the low pressure chamber.
23, the second control valve 27 is closed, the flow rate from the pump chamber 4 to the high pressure chamber 21 is set to 0, and the pressure in the high pressure chamber 21 is reduced, so that the timer piston 8 is spring-loaded.
It is moved to the high pressure chamber 21 side by the force of 24.

In the conventional example, the fuel always flows from the pump chamber to the high pressure chamber, and even if the flow rate (duty ratio) of the control valve in the passage between the high pressure chamber and the low pressure chamber is maximized, the pressure in the high pressure chamber is increased. Although there is a problem that it takes a long time to lower the pressure, in the present invention, since the passage from the pump chamber 4 to the high pressure chamber 21 is closed, the pressure in the high pressure chamber 21 is rapidly reduced and the moving speed of the timer piston 8 is improved. can do.

When advancing the fuel injection timing, control is performed to move the timer piston 8 to the low pressure chamber 23 side. That is, the first control valve 26 is closed to set the flow rate from the high pressure chamber 21 to the low pressure chamber 23 to zero, and the second control valve 27 is opened to transfer the high pressure fuel in the pump chamber 4 to the high pressure chamber 21. By guiding, the timer piston 8 is moved to the low pressure chamber 23 side against the force of the spring 24.

In the conventional example, the movement of the timer piston due to the driving reaction force of the cam is minimized, and the passage of the pump chamber and the high pressure chamber is connected to each other so that the pressure of the high pressure chamber is lowered during the retard control. Although it was necessary to reduce the flow rate through the orifice, this orifice is not necessary in the present invention, and the moving speed of the timer piston 8 can be improved. Next, the control will be described.

FIG. 2 is a functional block diagram of a control unit 28 portion as a control device, which detects a target injection timing means for calculating a target injection timing of fuel based on engine operating conditions and an actual fuel injection timing. Of the actual injection timing detection means, comparison means for comparing the target injection timing with the actual injection timing, and valve control means for controlling the opening and closing of the first and second control valves 26, 27 according to the comparison result. Specific contents will be described with reference to a flowchart.

FIG. 3 is a flow chart of the first embodiment. Step 1 (denoted as S1 in the figure. The same applies hereinafter)
Then, the engine speed (fuel injection pump speed) Ne and the engine load (accelerator opening) Q are input. In step 2, the target injection timing (target IT) is referred from the engine speed Ne and the engine load Q with reference to the map shown in FIG.
Is calculated.

In step 3, the crank angle and the needle valve lift are input. In step 4, the actual injection timing (actual IT) is calculated from the crank angle at the start of the needle valve lift. In step 5, the difference D = actual IT−target IT between the actual injection timing (actual IT) and the target injection timing (target IT) is calculated.

In step 6, the absolute value of the difference D is compared with the dead zone DELTA of the injection timing control given as data in advance. When | D | <DELTA, steps 7 and 8 are executed for the fixed control of the timer piston. That is,
The first control valve 26 is closed in step 7, and the second control valve 26 is closed in step 8.
The control valve 27 of is closed.

If | D | ≧ DELTA, the process proceeds to step 9 to determine whether the difference D is positive or negative. If D> 0, the actual injection timing is ahead of the target injection timing, so steps 10 and 11 are executed for the retard control of the timer piston. That is, in step 10, the first control valve 26 is opened, and in step 11, the second control valve 27 is closed. If D <0,
Since the actual injection timing is behind the target injection timing, steps 12 and 13 are executed for the advance control of the timer piston. That is, in step 12, the first control valve 26 is closed, and in step 13, the second control valve 27 is opened.

Here, the steps 1 and 2 correspond to the target injection timing calculating means, the steps 3 and 4 correspond to the actual injection timing detecting means, and the steps 5, 6 and 9 correspond to the comparing means. , Steps 7, 8, 10, 11, 12, 13 correspond to the valve control means. In the valve control means, steps 7 and 8 correspond to fixed control means, and steps 10 and 8
The portion 11 corresponds to the retard control means, and the portions of steps 12 and 13 correspond to the advance control means.

According to this embodiment, the exhaust performance and the output performance can be improved by improving the response of the fuel injection timing control.
In particular, the transition from the retard control at low speed and low load to the advance control at acceleration operation becomes quick, so that smoke during acceleration and PM can be greatly reduced, and fuel consumption can be improved. Further, by greatly reducing the injection timing fluctuation due to the cam driving reaction force, it is possible to improve the exhaust performance (particularly PM and HC) during steady operation and reduce the torque fluctuation.

Further, by using the ON / OFF control valve, the cost can be reduced (the response speed and durability required for the duty control valve are unnecessary), the operating noise when the valve is driven, and the power consumption can be reduced. FIG. 6 shows a flowchart of the second embodiment. In this embodiment, the first and second control valves
When the valves 26 and 27 are driven to open, the driving is performed at a duty ratio (open time ratio) according to the difference between the actual injection timing and the target injection timing.

Therefore, in step 10 ', the first control valve
When the valve 26 is driven to open, the duty ratio (DUTY ratio) corresponding to the difference | D | between the actual injection timing and the target injection timing is calculated, and the second control valve 27 is turned on in step 12 '. The difference between the actual injection timing and the target actual injection timing when the valve opening drive is performed | D |
The duty ratio (DUTY ratio) corresponding to is calculated.

Specifically, as shown in FIG. 7, the difference | D |
The duty ratio (DUTY ratio) is increased as is increased. As a result, overshooting or undershooting during injection timing control can be prevented, and control convergence is improved. FIG. 8 shows a flowchart of the third embodiment.

In this embodiment, the fuel injection timing is forcibly advanced when the engine is started (while the drive of the starter motor is ON). Therefore, first enter the starter signal in step 101 and then
At 102, it is determined whether the starter is ON, and the starter is ON.
In this case, the first control valve 26 is closed in step 103, and the second control valve 27 is driven at 100% duty ratio to be fully opened in step 104. The steps 101 and 102 correspond to the starting detection means, and the steps 103 and 104 correspond to the forced advance control means.

When the engine is stopped, the differential pressure acting on the timer piston 8 is 0, and the timer piston 8 is located on the most retarded side by the spring 24. On the other hand, at the time of starting, it is required to control the fuel injection timing to the advance side. Therefore,
With this control, the fuel injection timing can be promptly controlled to the advance side at the time of start, and good startability can be obtained.

[0043]

As described above, according to the first aspect of the invention, not only the first control valve is provided in the passage connecting the high pressure chamber and the low pressure chamber at both ends of the timer piston, but also the feed pump is provided. A second control valve is provided in a passage that connects the discharge side (pump chamber) and the high-pressure chamber of
By controlling the opening and closing of the control valve, the timer piston is fixedly controlled, and stable injection timing control can be achieved by preventing fluctuations in the timer piston position due to cam drive reaction force and pump chamber pressure fluctuations. At the same time, it is possible to improve the responsiveness of the injection timing control by improving the moving speed of the timer piston during advance or retard control of the timer piston.

According to the second aspect of the present invention, the target fuel injection timing is calculated based on the engine operating conditions, compared with the actual injection timing, and the first and second fuel injection timings are calculated according to the comparison result.
By controlling the opening and closing of the control valve, the effect that the injection timing can be controlled with good response is obtained. According to the invention of claim 3, when the difference between the actual injection timing and the target injection timing is less than the predetermined value, the injection timing can be stably fixed by closing both the first and second control valves. Further, when the difference between the actual injection timing and the target injection timing is a predetermined value or more and the actual injection timing is advanced from the target injection timing, the first control valve is opened and the second control valve is closed. As a result, the actual injection timing can be quickly retarded, and when the difference between the actual injection timing and the target injection timing is a predetermined value or more and the actual injection timing is delayed from the target injection timing, the first By closing the control valve and opening the second control valve, the effect that the actual injection timing can be advanced rapidly is obtained.

According to the fourth aspect of the present invention, when the first and second control valves are opened, the duty ratio corresponding to the difference between the actual injection timing and the target injection timing drives the duty ratio to control overcontrol. Shooting or undershooting can be prevented, and the effect of improving control convergence can be obtained. According to the invention of claim 5, by forcibly closing the first control valve and opening the second control valve at the time of starting the engine, the fuel injection timing is promptly controlled to the advance side at the time of starting. Therefore, the effect that the startability is improved can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a distributed fuel injection pump showing an embodiment of the present invention.

FIG. 2 is a functional block diagram of a control unit part.

FIG. 3 is a flowchart showing a first embodiment of control.

FIG. 4 is a diagram showing a map for calculating a target injection timing.

FIG. 5 is a diagram showing a change in a timer piston position due to a cam driving reaction force.

FIG. 6 is a flowchart of a second embodiment of control.

FIG. 7 is a diagram showing a map for calculating a valve drive duty ratio.

FIG. 8 is a flowchart of a third embodiment of control.

[Explanation of symbols]

 1 Fuel Injection Pump 2 Drive Shaft 3 Feed Pump 4 Pump Chamber 5 Cam Disc 6 Plunger 8 Timer Piston 9 Roller Holder 20-1, 20-2 Passage 21 High Pressure Chamber 22 Passage 23 Low Pressure Chamber 24 Spring 25-1, 25-2 Passage 26 First control valve 27 Second control valve 28 Control unit 29 Rotation sensor 30 Accelerator sensor 31 Needle valve lift sensor

Claims (5)

[Claims] 1. A fuel injection timing control device for a fuel injection pump for a diesel engine, which controls fuel injection timing according to a moving position of a timer piston, wherein a high pressure chamber communicating with a discharge side of a feed pump is provided at one end of the timer piston. , A low pressure chamber communicating with the suction side of the feed pump is formed at the other end, and a passage communicating the high pressure chamber and the low pressure chamber is provided, and a first control valve is provided in this passage, For a diesel engine, characterized in that a control device for interposing a second control valve in a passage connecting the discharge side of the pump and the high-pressure chamber and controlling opening and closing of the first and second control valves is provided. Fuel injection timing control device for fuel injection pump. 2. The control device includes a target injection timing means for calculating a target injection timing of fuel based on engine operating conditions, an actual injection timing detection means for detecting an actual injection timing of fuel, and a target injection timing. The diesel engine according to claim 1, further comprising: a comparison unit that compares the actual injection timing with a valve control unit that controls opening and closing of the first and second control valves according to a comparison result. Injection timing control device for a fuel injection pump for automobiles. 3. The valve control means includes fixed control means for closing both the first and second control valves when the difference between the actual injection timing and the target injection timing is less than a predetermined value, and the actual injection timing and the target injection timing. When the difference from the timing is a predetermined value or more and the actual injection timing is advanced from the target injection timing, the first control valve is opened and the second control valve is closed. An advance control means for closing the first control valve and opening the second control valve when the difference from the target injection timing is a predetermined value or more and the actual injection timing is retarded from the target injection timing. The fuel injection timing control device for a diesel engine fuel injection pump according to claim 2, which is configured. 4. The valve control means is driven at a duty ratio corresponding to a difference between an actual injection timing and a target injection timing when the first and second control valves are opened. The fuel injection timing control device for a diesel engine fuel injection pump according to claim 3. 5. The valve control means includes a start-time detection means for detecting the start-up of the engine, and a forced advance control forcibly closing the first control valve and opening the second control valve when the engine is started. And a structure including means.
A fuel injection timing control device for a fuel injection pump for a diesel engine according to claim 4.