JPH06257496A - Accumulation type fuel injection device - Google Patents

Abstract

PURPOSE:To surely prevent abnormal increase of accumulator chamber pressure in overrun condition even when a computer mounted on a vehicle cannot work normally. CONSTITUTION:A safety valve 113, which serves as another relief valve in addition to an ordinary relief valve 4a, is arranged in a common rail 4. The safety valve 113 opens when a rod 129 is pulled so as to discharge a fuel oil from the common rail 4. The rod 129 is pulled, when weights 107, which are opened when the number of revolutions of an engine reaches an overrun number of revolutions or more, pushes out a bar 109 provided with a disk and a force point of a lever member 111 is pushed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation fuel injection device for a diesel engine, and more particularly to a pressure-accumulation fuel injection device equipped with a mechanism for preventing the pressure in the pressure accumulator chamber from rising above an overrun speed.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Laid-Open No. 258160/1987 and No. 176158/1987 are known as pressure-accumulation fuel injectors for such diesel engines. These pressure-accumulation fuel injection devices control the amount of fuel pressure fed to the pressure accumulator by controlling the valve closing timing of the externally open solenoid valve of the high-pressure pump driven by the rotational force of the diesel engine, thereby controlling the pressure accumulation. It was configured to bring the chamber pressure to the desired fuel injection pressure. Then, the in-vehicle computer is configured to calculate the fuel injection timing and the like based on various detected values of the operating state and control the opening of the fuel injection valve connected to the pressure accumulating chamber.

By the way, in such a pressure accumulating fuel injection device, when the diesel engine overruns and the number of revolutions further rises, the externally opening solenoid valve is naturally closed and the fuel is abnormally pumped to the accumulating chamber. Could be damaged. For this reason, a technology has been proposed in which the solenoid valve of the high-pressure pump is fixedly controlled at an overrun speed or higher to prevent the fuel from being introduced into the pressure accumulating chamber and prevent the pressure accumulating chamber from being damaged (Japanese Patent Laid-Open No. 4-42). 272471).

[0004]

However, Japanese Unexamined Patent Publication (Kokai) No. 4-2.
Since the safety mechanism described in Japanese Patent No. 72471 is controlled by the vehicle-mounted computer, when the vehicle-mounted computer becomes inoperable, there is a problem that the safety mechanism does not work even if the overrun speed is reached. . Further, the overrun itself may occur due to a malfunction such as a runaway of the vehicle-mounted computer, and in this case, the overrun state may be further promoted.

Therefore, the present invention provides a pressure-accumulation fuel injection device capable of reliably preventing an abnormal increase in pressure of the pressure accumulator in an overrun state even when the vehicle-mounted computer cannot operate normally. To aim.

[0006]

SUMMARY OF THE INVENTION The pressure-accumulation fuel injection device of the present invention, which has been made to achieve the above object, comprises:
In a pressure-accumulation type fuel injection device in which fuel drawn from a fuel tank is pressure-fed to a pressure accumulation chamber by a rotational force of a diesel engine, and fuel is injected at the pressure of the pressure accumulation chamber, a fuel pressure feeding system to the pressure accumulation chamber or the pressure accumulation chamber itself is provided. A pressure increase preventing member for stopping the pressure feed of fuel to the accumulator and / or releasing the fuel from the accumulator by a mechanical operation to prevent an increase in pressure of the accumulator, and an output shaft of the diesel engine or the output shaft thereof. An operating member that is provided on another shaft that is coupled to the mechanical member and that mechanically operates when the diesel engine reaches a predetermined overrun speed, and mechanically transmits the motion of the operating member to the pressure increase prevention member, And a motion transmission member for performing an operation of preventing the pressure in the pressure accumulating chamber from rising.

According to the pressure-accumulation type fuel injection device of the present invention, when the diesel engine reaches the overrun speed, the operating member mechanically operates, and the operation transmitting member mechanically transfers the operation to the pressure rise preventing member. The pressure increase prevention member also mechanically performs an operation of mechanically preventing the pressure in the accumulator chamber from increasing. As a result, when the diesel engine reaches the overrun speed, the pressure accumulating chamber releases the fuel and / or stops the pressure feeding of the fuel, so that the fuel pressure does not increase at least further.

[0008]

The present invention will now be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a configuration explanatory view of a common rail fuel injection control device including a variable discharge high pressure pump.

This common rail fuel injection control device 1
Is a 6-cylinder diesel engine 2, an injector 3 for injecting fuel into each cylinder of the diesel engine 2, a common rail 4 for accumulating high-pressure fuel supplied to the injector 3, and a variable discharge for pumping high-pressure fuel to the common rail 4. A high-pressure pump 5 and an electronic control unit (ECU) 6 that controls these pumps.

The ECU 6 controls the state of the diesel engine 2, for example, the detection value of the rotation speed sensor 7 and the accelerator sensor 8.
The target common rail pressure PFIN for realizing the fuel injection pressure that optimizes the combustion state of the diesel engine 2 is calculated by taking in the operating conditions such as the detection value of the above, and the detection value of the common rail pressure sensor 9 provided in the common rail 4 is calculated. Based on the actual common rail pressure PC based on the target common rail pressure PFI
Common rail pressure feedback control is performed to drive and control the variable discharge high pressure pump 5 so as to maintain N.

The variable discharge high-pressure pump 5 sucks the fuel stored in the fuel tank 10 through the low-pressure supply pump 11 and pressurizes it to a high pressure inside itself according to a control command from this ECU, and pressurizes this. Supplying high pressure fuel 12
To the common rail 4 by pressure.

Each injector 3 is connected by a pipe 13 to
It is connected to a common rail 4 that stores high-pressure fuel.
Then, by opening and closing the control valve 14 arranged in each injector 3, the high pressure fuel accumulated in the common rail 4 to become the target common rail pressure PFIN is injected into the combustion chamber of each cylinder of the diesel engine 2. To be done. The opening / closing operation of the control valve 14 of the injector 3 is executed based on an injector control command from the ECU 6. This injector control command is for adjusting the fuel injection amount and the fuel injection timing, and is calculated based on the detection values from the operating condition detecting means such as the rotation speed sensor 7 and the accelerator sensor 8, and the crank angle sensor 15 It is output from the ECU 6 at a predetermined timing based on the detection value of the cylinder discrimination sensor 16 or the like. The control command for the variable discharge high-pressure pump 5 is also output at a predetermined timing based on the detected values from the crank angle sensor 15, the cam angle sensor 38 described later, and the like.

Next, the structure of the variable discharge high pressure pump 5 will be described with reference to FIGS. Variable discharge high pressure pump 5
Is connected to the housing 20, the cam chamber 30 arranged at the lower end thereof, the pump cylinder 21 arranged in the housing 20, and the pump cylinder 21, and supplies low-pressure fuel from the low-pressure supply pump 11. The receiving pipe 22 for receiving and the solenoid valve 60 screwed to the upper end of the pump cylinder 21 are provided.

A plunger 23 is slidably inserted in the pump cylinder 21 while maintaining liquid tightness. The plunger 23 has a cylindrical shape, and an upper end surface thereof cooperates with an inner peripheral surface of the pump cylinder 21 to form a pump chamber 24. In the pump cylinder 21, the supply pipe 1 to the common rail 4
A discharge hole 41 for connecting the two is formed.

Further, the pump cylinder 21 and the housing 2
A fuel tank 26 is formed between the fuel tank 26 and 0, and the low-pressure fuel introduced into the housing 20 from the introduction pipe 22 is collected there. The fuel reservoir 26 also functions as a relief of the fuel overflowing from the pump chamber 24.

The discharge hole 41 communicates with the discharge port 45 via a check valve 42. The fuel pressurized in the pump chamber 24 pushes the valve body 43 of the check valve 42 open against the urging force of the return spring 44 and the common rail pressure, and passes from the discharge port 45 through the supply pipe 12 to It is pumped to the common rail 4.

The lower end of the plunger 23 is connected to a valve seat 35, and the valve seat 35 is pressed by a plunger spring 27 against a tappet 34 having a cam roller 33. In the cam chamber 30, the rotation speed of the diesel engine 2 is 1
A cam shaft 31 that rotates at / 2 is inserted, and a cam 32 that is in contact with a cam roller 33 is fixed to the cam shaft 31.
The rotation of the cam shaft 31 causes the plunger 23 to reciprocate up and down along the cam profile of the cam 32 via the cam roller 33 and the tappet 34.

When the bottom dead center of the plunger 23 of the cam profile is a cam angle of 0 degree, the cam 32 has a circle of curvature R ₁ having a center outside the cam 32 between about 0 degree and about 30 degrees. It is composed of an arcuate concave curved surface 32c and a curved surface 32d having a center of curvature inside the cam 32, and has a substantially elliptical shape having a cam profile such that the plunger 23 reaches the top dead center at a cam angle of 90 degrees.

The solenoid valve 60 screwed to the upper end of the pump cylinder 21 has a valve body 62 for opening and closing a low pressure passage 61 opening to the pump chamber 24. The valve body 62 is a so-called open valve. Therefore, the valve body 62 is usually the spring 6
5 is opened into the pump chamber 24 by 5 to open the low-pressure passage 61.
5 against the urging force of the low pressure passage 61 and the pump chamber 2
It becomes the state of shutting off 4 and. Further, since the valve body 62 receives the fuel pressure inside the pump chamber 24 as the pressure in the valve closing direction, the higher the fuel pressure is, the better the sealing performance at the time of valve closing becomes.

The low pressure passage 61 opened and closed by the valve body 62 communicates with the fuel reservoir 26 via a gallery 63 and a passage 64. On the other hand, the plunger 23 moves up and down in the pump cylinder 21 as the cam shaft 31 rotates. The plunger 23 is lowered by the returning force of the plunger spring 27.

When the plunger 23 descends, the low pressure fuel is transferred to the fuel reservoir 26 through the solenoid valve 60 which is normally open.
Is sucked into the pump chamber 24. The fuel sucked into the pump chamber 24 tends to pressurize as the plunger 23 rises, but when the solenoid valve 60 is not energized, it passes through the low pressure passage 61, the gallery 63 and the passage 64 and enters the fuel reservoir 26. Overflow does not substantially pressurize the fuel in the pump chamber 24.

On the other hand, when the solenoid valve 60 is energized while the plunger 23 is moving up, the valve body 62 causes the low pressure passage 61 to move.
Therefore, the fuel in the pump chamber 24 cannot overflow and starts to be pressurized. And pump room 2
When the fuel pressure in 4 rises and overcomes the biasing force of the return spring 44 of the check valve 42 and the pressure of the common rail 4 applied to the valve body 43, the check valve 42 is pushed open and the high pressure fuel is discharged. It is pressure-fed to the common rail 4 through the hole 41, the discharge port 45, and the supply pipe 12.

As shown in FIG. 3, the cam shaft 31 has one timing gear 36 and a variable discharge high-pressure pump 5 (in this embodiment, 3) which is half the number of cylinders of the engine 2.
Individual pieces) are provided. In the figure, for convenience, one of the variable discharge high pressure pumps is omitted and only two variable discharge high pressure pumps 5a and 5b are shown. Further, since the same configurations as those shown in FIG. 2 are respectively attached with subscripts a and b, refer to FIG. 2 for the detailed structure and the like of the configurations with those subscripts a and b.

The timing gear 36 is provided with a total of six protrusions 37. Further, a cam angle sensor 38 including an electromagnetic pickup is provided in close proximity to the timing gear 36. The projection 37 provided on the timing gear 36 is provided on each cam 32 during one rotation of the cam shaft 31.
By the action of a, 32b, ...
The cam angle sensor 38 detects the start timing of the ascending stroke of the plungers 23a, 23b, ... The timing signal detected by the cam angle sensor 38 is E
Input to CU6.

Based on the timing signal from the cam angle sensor 38, the ECU 6 causes the solenoid valves 60a, 60b, ...
Drive pulse is output to. As shown in FIG. 4, the drive pulse is output with a delay of a period TF (hereinafter, referred to as an output waiting period TF) using the timing signal detected at the bottom dead center position of the plunger 23 as a reference pulse. Due to this drive pulse, energization of the solenoid valve 60 is started, and the valve body 62 is closed with a delay of a period TC (hereinafter referred to as a valve closing delay TC) due to the rising of the current. After that, since the valve body 62 is maintained in the closed state due to the pressure rise in the pump chamber 24 accompanying the rise of the plunger 23, the drive pulse is turned off after a short period TON, and the power consumption is saved. . This is an advantage because the valve is open.

After the valve body 62 is closed in this way, the period until the plunger 23 reaches the top dead center is the fuel pressurization period in the pump chamber 24, and the amount of fuel proportional to the area of the hatched portion in the drawing is common rail. It will be pumped to No. 4. Therefore, in this figure, if the output timing of the drive pulse is advanced so that the hatching area becomes large, more fuel is pumped to the common rail 4, and conversely, if the output timing is delayed, the amount of fuel pumped to the common rail 4 is increased. Decrease.
That is, the pressure of the common rail 4 can be adjusted by the output timing of the drive pulse (output waiting period TF).

Next, the main routine for feedback controlling the pressure of the common rail 4 will be described. E
In the CU 6, the engine speed Ne is calculated based on the detection value of the rotation speed sensor 7 (S1), and the detection value of the accelerator sensor 8 is A / D converted to obtain the accelerator opening degree Accp (S2).

Next, referring to a target fuel injection amount calculation map as shown in FIG. 6 based on the engine speed Ne and the accelerator opening degree Accp, the target fuel injection amount QFIN is obtained.
Is calculated (S3). Then, this target fuel injection amount QF
Based on the IN and the engine speed Ne, the target common rail pressure calculation map as shown in FIG. 7 is referred to, and the target common rail pressure PFIN is calculated (S4). Each map is stored in the built-in ROM of the ECU 6, and the calculation results QFIN, PFIN, etc. are stored in the built-in RAM.

On the other hand, in the first reference pulse interruption process (FIG. 8) synchronized with the compression stroke of each cylinder of the diesel engine 2, the intake of the target common rail pressure PFIN and the intake of the target fuel injection amount QFIN are executed. (S11, S12). Then, based on the target common rail pressure PFIN and the target fuel injection amount QFIN, the drive pulse output waiting period calculation map as shown in FIG. 9 is referred to, and the reference value (reference output waiting period) TFBASE of the drive pulse output waiting period is set. Calculate (S13).

Then, the detected value of the common rail pressure sensor 9 is A / D converted to calculate the actual common rail pressure PC (S).
14). Then, the actual common rail pressure PC and the target common rail pressure PFIN are compared, and the pressure difference ΔP = PC−PF.
A correction amount TFFB for the reference output waiting period TFBASE is calculated according to IN (S15). In calculating the correction amount TFFB, a generally well-known PID control method is used.

Subsequently, the control output waiting period TF is calculated as the sum of the reference output waiting period TFBASE and the correction amount TFFB (S16). Output waiting period TF thus calculated
.. are controlled in accordance with the above, and the pressure in the common rail 4 is maintained at a target common rail pressure PFIN suitable for performing fuel injection according to operating conditions such as the engine speed Ne and the accelerator opening degree Accp. .

By the way, the diesel engine 2 of this embodiment
In order to prevent engine overrun, it operates mechanically at overrun speed Neo or higher, and the common rail 4
A safety mechanism has been adopted to forcibly release the fuel from. This safety mechanism will be described with reference to FIG.

The safety mechanism includes a rotary shaft 101 connected to a crankshaft or a camshaft of a high-pressure pump, a disc 103 provided at one end of the rotary shaft, and a hinge on the disc 103 via an L-shaped lever 105. A weight 107 connected to the lever 107, a bar 109 with a disk that abuts against the L-shaped lever 105, a lever member 111 that is swung by the bar 109 with a disk, and a safety valve 113 that is connected to the lever member 111. Equipped with.

A spring 115 for applying a predetermined set-up load is attached to the disc-equipped bar 109. This spring 115 and spring 1 described later
The setup load of No. 27 is set by the relationship with the centrifugal force that the weight 107 receives by the rotation so that the bar with disk 109 moves to the right in the figure only when the overrun rotation speed is reached.

The safety valve 113 includes a housing 121, a cap 123 screwed to the housing 121, a valve body 125 housed therein, a spring 127 for applying a predetermined setup load to the valve body 125, and a valve body 1.
25 and a rod 129 that connects the working end of the lever member 111 to each other, and the inlet port 13 connected to the common rail 4
1 and an outlet 133 communicating with the fuel tank 10. An oil seal is applied to the housing penetrating portion of the rod 129.

The safety valve 113 is another relief valve provided separately from the relief valve 4a of the common rail 4. The oil passage diameter and the like are configured so that a larger amount of fuel oil can be discharged than the relief valve 4a, and the spring 127 is set so as to give a higher setup load than the relief valve 4a. Therefore, normally, the relief valve 4 does not open earlier than the relief valve 4. On the other hand, when the safety valve 113 opens, the relief valve 4a
It allows more fuel to escape than when it was opened.

According to this safety mechanism, when the engine speed is lower than the overrun speed, even if the weight 107 tries to move to the outside due to the centrifugal force, the spring 11 is released.
It will be pushed back by 5, and the bar with disc 1
09 and the lever member 111 remain in the initial position. On the other hand, when the engine speed exceeds the overrun speed, the force of the weight 107 to move outward becomes large, and the spring 115 loses to cause the L-shaped lever 10 to move.
5 starts rotating in the direction of the thick arrow in the figure. At the same time, the bar with disc 109 also starts moving to the right as indicated by the thick arrow in the figure. Then, the lever member 111 becomes a shape in which the force point is pushed, and the rod 129 of the safety valve 113 is pulled. As a result, the valve element 125 blocking the inflow port 131 of the safety valve 113 moves, the common rail 4 and the fuel tank 10 are communicated with each other,
Fuel oil in the common rail 4 is discharged through the safety valve 113.

Therefore, the pressure of the common rail 4 decreases,
Even if the high-pressure pump 5 continues to pump fuel to the common rail 4, it will not be damaged. Further, even if injector driving or high-pressure pump driving that promotes overrun due to a data error of the ECU 6 or runaway is performed, the fuel injection is suppressed or stopped as a result of the pressure drop of the common rail 4, and further Overrun is not promoted. Then, the overrun gradually converges.

Although one embodiment of the present invention has been described above, the present invention is not limited to this, and various modes can be adopted without departing from the scope of the invention. For example, the portion operated by centrifugal force may be configured as shown in FIG. 11 so that the rod 129 of the safety valve 113 can be directly pulled without using the lever member 111.

Further, the relief valve which is usually provided may be used as the safety valve without providing the dedicated safety valve. Further, as shown in FIG. 12, a 3-port 2-position switching valve 140 having a port arrangement as shown is provided between the high-pressure pump 5 and the low-pressure supply pump 11, and the same operation as that described in the embodiment is performed. A transmission mechanism may be applied to switch this so that fuel is not supplied to the high-pressure pump 5 at an overrun speed or higher. This is because, if the fuel is not supplied to the high-pressure pump 5, the fuel is not pressure-fed to the common rail 4 and at least the rise of the common rail pressure can be prevented.

In addition, as shown in FIG. 13, the high pressure pump 5
A mechanical switch 150 is provided between the electromagnetic valves 60a and 60b of the above and the ECU 6, and the operation transmission mechanism described in the embodiment is applied to switch the mechanical switch 150. May not be able to pump fuel.

As the solenoid valve 60 of the high pressure pump 5,
As shown in FIG. 14, the exciting coil 163 is arranged on the inner side wall surface of the housing 161, and the iron core portion 167 of the valve body 165 is attracted to close the valve.
The upper part of the valve is protruded from the housing 161, and the protrusion 169 is mechanically closed so that it can be pulled up at an overrun speed or more by applying the motion transmission mechanism as described in the embodiment. 160 may be used as a safety mechanism. In addition, reference numeral 171 in the figure indicates the valve body 1 at the normal time.
A spring 17 for keeping the valve 65 open.
Reference numeral 3 is an oil seal of the penetrating portion on the side of the protrusion.

Since the safety mechanism of the embodiment has a structure in which fuel is drained from the common rail 4, the effect of collecting overruns at an early stage is the highest. The common rail pressure is maintained only by stopping the fuel pressure feeding to the common rail 4, and the fuel injection in that state can be continued. However, if the common rail pressure is removed, the injector will open even if fuel injection is instructed. This is because the valve pressure is not reached and fuel cannot be injected.

[0044]

As described above, according to the pressure-accumulation type fuel injection device of the present invention, it is possible to prevent the pressure increase in the pressure-accumulation chamber at the time of an abnormality such as an overrun, and to promote the overrun state or to increase the pressure of the pressure-accumulation chamber. Damage can be avoided. In particular, even if the vehicle-mounted computer is abnormal, the overrun state can be appropriately dealt with, and the safety is extremely high.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a system of an embodiment.

FIG. 2 is a cross-sectional view showing the configuration of a variable discharge high pressure pump.

FIG. 3 is a schematic diagram schematically showing the configuration of a variable discharge high pressure pump.

FIG. 4 is a timing chart for explaining the operation of the variable discharge high pressure pump.

FIG. 5 is a flowchart of a main routine executed by the ECU for calculating a target fuel injection amount and a target common rail pressure.

FIG. 6 is a map for calculating a target fuel injection amount.

FIG. 7 is a map for calculating a target common rail pressure.

FIG. 8 is a flowchart of a first reference pulse interrupt process for calculating a drive pulse output waiting period to the solenoid valve.

FIG. 9 is a map for calculating a reference output waiting period.

FIG. 10 is a configuration diagram of a safety mechanism that mechanically operates at an overrun rotation speed or more.

FIG. 11 is a configuration diagram of a modified example of the operation member and the motion transmission member of the safety mechanism.

FIG. 12 is a configuration diagram of a modified example of the pressure rise prevention member of the safety mechanism.

FIG. 13 is a configuration diagram of a modified example of the pressure rise prevention member of the safety mechanism.

FIG. 14 is a configuration diagram of a modified example of the pressure rise prevention member of the safety mechanism.

[Explanation of symbols]

1 ... Common rail fuel injection control device, 2 ... Diesel engine, 3 ... Injector, 4 ... Common rail, 5 ... Variable discharge high-pressure pump, 6 ...
Electronic control unit (ECU), 10 ... Fuel tank, 11
... Low-pressure supply pump, 101 ... Rotary shafts 101, 1
03 ... disk, 105 ... L-shaped lever, 1
07 ... weight, 109 ... bar with disc, 1
11 ... Lever members 111, 113 ... Safety valve, 11
5 ... Spring, 125 ... Valve body, 127 ...
Spring, 129 ... Rod, 131 ... Inlet, 133 ... Outlet, 140 ... 3-port 2-position switching valve, 150 ... Mechanical switch, 160 ... Mechanically closed valve Open valve possible.

Claims (1)

[Claims] 1. A pressure-accumulation type fuel injection device, in which fuel pumped from a fuel tank is pressure-fed to a pressure accumulation chamber by a rotational force of a diesel engine and fuel is injected at the pressure of the pressure accumulation chamber, wherein A pressure rise prevention member that is provided in the accumulator chamber itself and that stops the pumping of fuel to the accumulator chamber and / or discharges the fuel from the accumulator chamber by a mechanical operation to prevent the pressure of the accumulator chamber from rising and the output of the diesel engine. An operating member that is provided on a shaft or another shaft connected to the output shaft and that mechanically operates when the diesel engine reaches a predetermined overrun rotation speed, and a movement of the operating member to the pressure rise prevention member. Accumulator-type fuel injection device, comprising: a motion transmission member that transmits the power to prevent the pressure of the accumulator chamber from rising.