JP2000027693A - Accumulator type fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an accumulator type fuel injection device which is excellent in a rise-up characteristic without the necessity of a large size exclusive inductor, and which can prevent aging effect. SOLUTION: Since energy is recovered with the use of a fly-back voltage of an injector, and since energy generated during a drive of a high pressure pump is recovered, the energy can be efficiently recovered without carrying out a special operation in order to obtain a charge energy of a charge capacitor 50. Further, energy generated when a pump linear solenoid 18 is driven for carrying out feed-back control is recovered without feeding a pulse with which the injection is not operated, and accordingly, it is possible to prevent abrasion of components of the injector, variation in the characteristic of an injector solenoid 36, and deterioration of an fuel injection characteristic. Thereby it is possible to prevent aging effect of a common rail type fuel injection device.

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 for an internal combustion engine that drives an injector for injecting and supplying high-pressure fuel stored in a pressure accumulation chamber to the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as means for supplying high-pressure fuel to a plurality of injectors provided corresponding to a plurality of cylinders of a multi-cylinder internal combustion engine, a so-called common rail for supplying high-pressure fuel stored in a pressure storage chamber to each injector is known. 2. Description of the Related Art A known fuel injection device is known.

In such a common rail type fuel injection device, a drive circuit for causing the injector to respond at a high speed includes a capacitor connected in parallel to a drive current supply path to the injector, and a drive circuit for driving the injector while the injector is not driven. A booster circuit for charging the capacitor with a high voltage exceeding the battery voltage.The booster circuit discharges energy stored in the capacitor at the time of driving the injector, and makes the injector respond at high speed by flowing a peak current to the injector. A known driving circuit is known.

[0004]

However, in such a drive circuit, it is necessary to complete the charging of the capacitor while each injector is driven, that is, between the fuel injection and the next fuel injection. Therefore, it is necessary to configure the booster circuit using a large-capacity transformer or switching element so that the capacitor can be charged even at the time of high-speed rotation and high load of the internal combustion engine in which the fuel injection interval is shortest, There has been a problem that the electronic control device becomes large and expensive.

In view of this, Japanese Patent Publication No. 63-9096 proposes a drive circuit that uses a flyback voltage from the injector that is generated when the injector is closed. Also, in Japanese Patent No. 2598595,
A drive circuit has been proposed which uses the above flyback voltage and sends a pulse to the extent that the injector does not operate during the injector closing period to recover energy.

However, the driving circuit disclosed in Japanese Patent Publication No. 63-9096 has a problem that only small energy is charged. Patent No. 25
In the drive circuit disclosed in Japanese Patent No. 98595, a pulse is sent to the injector only for the purpose of recovering energy, which may lead to wear of sliding parts of the injector, change in solenoid characteristics, and deterioration of fuel injection performance. However, there is a problem that the fuel injection device may cause a temporal change.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made in order to solve the above-mentioned problems. The purpose is to provide. Another object of the present invention is to provide a pressure accumulating fuel injection device capable of reducing the size of an electronic control device and reducing manufacturing costs.

[0008]

According to a first aspect of the present invention, there is provided a pressure-accumulation type fuel injection device, wherein a first injection control solenoid valve for controlling a fuel injection timing and a fuel injection amount of an injector is provided. An electromagnetic solenoid, and a second electromagnetic solenoid provided on an electromagnetic control valve for controlling a fuel discharge amount for discharging fuel from the high-pressure pump to the pressure accumulating chamber, wherein the first electromagnetic solenoid is provided when the injector is closed. While recovering the generated first energy, the second energy
The second energy generated when the electromagnetic solenoid is driven is recovered. Therefore, energy can be efficiently recovered without using a large-sized dedicated inductor for obtaining charge energy.

Further, since energy generated when the second electromagnetic solenoid of the high-pressure pump for which feedback control is performed is recovered without sending a pulse that does not operate to the injector, the sliding parts of the injector can be recovered. It is possible to prevent wear, a change in the solenoid characteristics of the first electromagnetic solenoid of the injector, and deterioration of the fuel injection performance. Therefore, it is possible to prevent the pressure-accumulation type fuel injection device from changing over time.

According to the pressure accumulating fuel injection device of the present invention, the first switching means connected in series with the first electromagnetic solenoid, and the power supply is connected to one end of the series circuit; A capacitor branched and connected between the solenoid and the first switching means; an energy recovery path for guiding the first and second energies to the capacitor; and a second energy recovery path provided in the energy recovery path for opening and closing the energy recovery path. And switching means connected in series with the second electromagnetic solenoid to control the second electromagnetic solenoid. For this reason, energy can be efficiently recovered without performing a special operation for obtaining charge energy.

Further, it is possible to realize a capacitor discharge type injector driving circuit having excellent start-up characteristics without using a large dedicated inductor for obtaining charge energy. Therefore, the electronic control unit is reduced in size,
Manufacturing costs can be reduced.

According to the pressure accumulating type fuel injection device according to the third aspect of the present invention, the protection means is connected in parallel with the second electromagnetic solenoid to electrically protect the control means, thereby preventing the control means from being destroyed. be able to. Therefore, the control of the second electromagnetic solenoid can be prevented from being affected, and the control of the fuel discharge amount for discharging fuel from the high-pressure pump to the accumulator can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. One embodiment in which the present invention is applied to a common rail type fuel injection device used in a six-cylinder vehicle diesel engine (hereinafter, “diesel engine” is referred to as an engine) is shown in FIGS.

As shown in FIG. 2, a common rail type fuel injection device 1 includes six injectors 3 arranged in each cylinder of an engine 2 for injecting fuel into each cylinder, and accumulating high pressure fuel to supply fuel. Each injector 3 through the passage 13
Rail 4 for supplying fuel to the fuel cell, and a high-pressure pump 5 for pressure-feeding the fuel to the common rail 4 via a fuel supply passage 12.
And a feed pump 11 that sucks up fuel stored in the fuel tank 10 and supplies it to the high-pressure pump 5, a common rail pressure sensor 9 that detects the internal pressure of the common rail 4, and an electronic control device (hereinafter, “electronic control”) that controls these. The device is referred to as an ECU. In addition to the common rail pressure sensor 9, the ECU 6 also receives signals from various operating state detecting means such as a rotational speed sensor 7 for detecting an engine rotational speed and an accelerator opening sensor 8 for detecting an accelerator opening. .

As shown in FIG. 3, the high-pressure pump 5
2 shows a control valve 19 serving as an electromagnetic control valve for adjusting the flow rate of the low-pressure fuel sucked from the fuel tank 10 by the feed pump 11 shown in FIG. A three-cylinder rotary pump 22 that supplies the common rail 4 is provided.

The metering valve 19 includes a pump linear solenoid 18 as a second electromagnetic solenoid and a spring 14
, A cylinder 15, and a valve element 16, and a check valve 17 is provided between the metering valve 12 and the rotary pump 22.
Since a, 17b, and 17c are provided, the feed pump 11 and the rotary pump 22 can communicate with each other and can be shut off.

The rotary pump 22 includes a spring 23
a, 23b and 23c, cylinders 24a, 24b and 24c, plungers 25a, 25b and 25c
Check valves 27a, 27b and 27c and eccentric cam 2
1 and a drive shaft 20. The plungers 25a, 25b, and 25c move up and down in the cylinders 24a, 24b, and 24c in synchronization with the drive shaft 20 via the eccentric cam 21, and the internal pressure of the cylinders 24a, 24b, and 24c exceeds a predetermined set valve opening pressure. Then, the check valves 27a, 27
The valves b and 27c are opened to supply the fuel in the cylinders 24a, 24b and 24c to the common rail 4 via the fuel supply passage 12.

In the high-pressure pump 5 configured as described above, when the metering valve 19 is opened, the cylinder 2
When the plungers 25a, 25b and 25c rise and the metering valve 19 is closed, the cylinders 24a, 24b and 24c are filled with fuel in a low pressure state.
The fuel filled in 4b and 24c is pressurized. When this pressure exceeds the set valve opening pressure of the check valves 27a, 27b and 27c, the check valves 27a, 27b and 27c open and the cylinders 24a, 24b and 24c are opened.
The fuel in the common rail 4 passes through the fuel supply passage 12
To be pumped.

In other words, by controlling the closing timing of the metering valve 19, the timing of starting the pressurized fuel supply to the common rail 4 by the high-pressure pump 5 is controlled.
9 shows that once the valve is closed, the valve closed state is maintained until the plungers 25a, 25b and 25c reach the top dead center, that is, the point at which the plunger shifts from ascending to descending. Pumping amount increases. That is, the metering valve 19 is for controlling the fuel discharge amount for discharging fuel from the high-pressure pump 5 into the common rail 4. In this way, the high-pressure fuel stored in the common rail 4 by the high-pressure pump 5 is sent to the injectors 3 installed for each cylinder of the engine 2 via the fuel supply passage 13.

As shown in FIG. 4, the injector 3 has a command piston 37 for opening and closing a fuel injection port 39 by moving a needle 38 up and down, a port 33 communicating with the pressure control chamber 32, and a port communicating with the fuel tank 10. Two-way valve 35 as an injection control solenoid valve that communicates with or shuts off valve 34
And an injector solenoid 36 as a first electromagnetic solenoid which is connected or disconnected by an injector drive circuit of the ECU 6 shown in FIG. 2 and controls the communication state of the two-way valve 35. An oil sump 31 is formed near the opening 39. In the injector 3, the fuel path is branched in two directions. One is in an oil sump 31 provided near the fuel injection port, and the other is through a pressure control chamber 32.
5 is supplied with high-pressure fuel. In the two-way valve 35, the port 33 and the port 34 are shut off when the injector solenoid 36 is not energized, and the port 33 and the port 34 are communicated when the injector solenoid 36 is energized.

In the injector 3 configured as described above, when the injector solenoid 36 in which the port 33 and the port 34 of the two-way valve 35 are shut off is non-conductive, the fuel is supplied from the fuel supply passage 13 and branched in the injector 3. One of the fuels is supplied to the pressure control chamber 32 to push down the needle 38, and the other is supplied to the oil reservoir 31 to push up the needle 38. At this time, since the area of the pressure control chamber 32 is larger, the force for pushing down the needle 38 is superior as a whole, and the fuel injection port 39 is maintained in a closed state.

On the other hand, when the injector solenoid 36 is turned on, the two-way valve 35 communicates with the port 33 and the port 34, and no fuel pressure from the fuel supply passage 13 is applied to the pressure control chamber 32. Is pushed upward, and the fuel injection port 39 is opened to start fuel injection.

Thereafter, when the power supply to the injector solenoid 36 is stopped, the port 33 and the port 34 are returned to a state where they are shut off again, and the fuel pressure from the fuel supply passage 13 is applied to the pressure control chamber 32. The needle 38 moves in the valve closing direction, and the fuel injection is stopped. Therefore,
In the injector 3, the fuel injection timing and the fuel injection amount can be arbitrarily controlled by controlling the power supply timing and the power supply period to the injector solenoid 36.

An injector drive circuit of the ECU 6 shown in FIG. 2 includes a CPU, a ROM, and a CPU for executing various control processes for fuel injection control in accordance with a preset control program.
A well-known microcomputer composed of a RAM or the like is mainly configured, and an injector drive circuit for energizing the injector solenoids 36 to drive the injectors 3 of each cylinder of the engine 2 and energizing the pump linear solenoid 18 shown in FIG. Alternatively, a high-pressure pump drive circuit that drives a metering valve 19 that controls the fuel pressure in the common rail 4 by turning off electricity is provided.

Next, the injector drive circuit and the high-pressure pump drive circuit will be described with reference to FIG. FIG. 1 shows only the one-cylinder injector solenoid 36 to simplify the description. As shown in FIG. 1, a discharging transistor TR1 is connected in series with one end of an injector solenoid 36 via a diode D1 to a power supply + B. The discharge transistor TR1 has a base connected to a microcomputer in the ECU (not shown), a collector connected to a cathode of a diode D1 and a cathode of a diode D3 described later, an emitter connected to one end of the injector solenoid 36, and It is connected to the cathode of a diode D2 described later. A charge capacitor 50 is connected via a diode D3 to a connection point 41 between the collector of the discharge transistor TR1 and the cathode of the diode D1. One end of the charge capacitor 50 is connected to the anode of the diode D3 and the cathode of a diode D5 described later, and the other end is connected to the ground potential point.

One end of the injector solenoid 36 is connected to a constant current source 40 for supplying a predetermined constant current via a diode D2. Further, the other end of the injector solenoid 36 is connected in series to a switching transistor TR2 as first switching means, and the switching transistor TR2 is connected to a ground potential point. Switching transistor TR2
Has a base connected to a microcomputer in the ECU, a collector connected to the other end of the injector solenoid 36, an anode of a diode D4 described later, and an emitter connected to a ground potential point.

One end of the pump linear solenoid 18 is connected to a power source + B via a diode D6. Further, the other end of the pump linear solenoid 18 is connected in series with a transistor TR3 as control means, and the transistor TR3 is connected to a ground potential point. The transistor TR3 has a base connected to a microcomputer in the ECU, a collector connected to the other end of the pump linear solenoid 18, an anode of a diode D8 described later,
And the collector of the transistor TR5 described later, and the emitter is connected to the ground potential point.

At a connection point 42 between the collector of the transistor TR2 and the other end of the injector solenoid 36, a transistor TR4 as a second switching means is connected in series via a diode D4, and the transistor TR4 is connected to a diode D5. Via charge capacitor 5
Connected to 0. The transistor TR4 is connected to a connection point 44 between the other end of the pump linear solenoid 18 and the collector of the transistor TR3 via a diode D8. The transistor TR4 has a base of ECU
The collector is connected to the cathode of the diode D4 and the cathode of the diode D8, and the emitter is connected to the diode D5.
Connected to the anode. Here, the charge capacitor 50 is connected from the connection point 42 via the transistor TR4.
Constitutes an energy recovery path for guiding the energy generated in the injector solenoid 36 to the charge capacitor 50. Further, a path from the connection point 44 to the charge capacitor 50 via the transistor TR4 constitutes an energy recovery path for guiding the energy generated in the pump linear solenoid 18 to the charge capacitor 50. Therefore, the transistor TR4 is provided in the energy recovery path, and has a configuration capable of opening and closing the energy recovery path.

A connection point 43 between one end of the pump linear solenoid 18 and the cathode of the diode D6 is connected to a transistor TR5 as protection means via a diode D7, and the transistor TR5 is connected to a connection point 44. That is, the transistor TR5 is connected in parallel to the pump linear solenoid 18. The transistor TR5 has a base connected to the microcomputer in the ECU, a collector connected to the connection point 44 and the anode of the diode D8, and an emitter connected to the anode of the diode D7.

Next, the operation of the injector drive circuit and the pump drive circuit configured as described above will be described with reference to FIGS.
This will be described with reference to FIG. (1) First, when the voltage of the charge capacitor 50 has reached the required charge voltage, the transistor TR1 is turned on. Thereafter, the transistor TR2 is turned on according to the required injection timing so that the required fuel injection timing is obtained according to the engine state. As a result, at time t1 shown in FIG. 5, the electrostatic energy stored in the charge capacitor 50 is released, and an injector drive current flows through the injector solenoid 36 to operate the injector.

(2) After a lapse of a predetermined time, the discharging of the charge capacitor 50 ends, and at time t2 shown in FIG. 5, the transistor TR1 is turned off. Then, by the constant current drive by the constant current source 40, the fuel injection state of the injector is maintained. At this time, the charging of the charge capacitor 50 is in a preparation state.

(3) At time t4 shown in FIG. 5, the transistor TR2 is turned off after an energization period that satisfies the fuel injection amount of the injector according to the engine state. At this time, magnetic energy as the first energy generated in the injector solenoid 36 is stored in the charge capacitor 50 as electrostatic energy. That is, energy is recovered using the flyback voltage of the injector.

(4) Apart from the above (1) to (3), the transistor TR3 is turned on or off to constantly control the pump linear solenoid 18 so as to satisfy the common rail pressure according to the engine state, To control the amount of fuel discharged into the common rail. Here, the pulse width of the transistor TR3 shown in FIG. 5 has an arbitrary value due to the difference between the command common rail pressure and the actual common rail pressure.
At t3, t5, t6, t7 and t8 shown in FIG. 5, magnetic energy as second energy generated when driving the pump linear solenoid 18 is stored in the charge capacitor 50 as electrostatic energy. That is, energy generated when the high-pressure pump is driven is recovered.

(5) At t9 shown in FIG. 5, when the voltage of the charge capacitor 50 reaches the required charge voltage,
The transistor TR4 is turned off and the transistor TR5 is turned on. Here, the transistor TR5 is for protecting the transistor TR4, and the transistor TR4 and the transistor TR5 are always in an opposite state. That is, when the voltage of the charge capacitor 50 has not reached the required charge voltage, the transistor TR4 is on and the transistor TR5 is off.

In the above (4) and (5), the signal from the microcomputer of the ECU to the transistor TR3 is feedback-controlled to the difference between the command common rail pressure and the actual common rail pressure, so that the solenoid of the pump linear solenoid 18 The solenoid characteristics of the injector solenoid 36 do not change due to changes in the characteristics or the like. That is, the fuel injection characteristics are not affected.

In this embodiment, since the energy is recovered using the flyback voltage of the injector 3 and the energy generated when the high-pressure pump is driven is recovered, a special energy for obtaining the charge energy of the charge capacitor 50 is obtained. Energy can be efficiently recovered without performing any operation.

Further, in the present embodiment, since the energy generated when the pump linear solenoid 18 for which feedback control is performed is driven is recovered without sending a pulse to the extent that the injector 3 does not operate, the sliding of the injector 3 is performed. Wear of moving parts, injector solenoid 3
6 can be prevented from changing and the fuel injection performance can be prevented from deteriorating. Therefore, it is possible to prevent the common rail type fuel injection device 1 from changing with time.

Further, in this embodiment, it is possible to realize a capacitor discharge type injector driving circuit having excellent start-up characteristics without using a large-sized dedicated inductor for obtaining charge energy. Therefore, E
The size of the CU 6 can be reduced, and the manufacturing cost can be reduced.

Further, in this embodiment, the transistor TR3 which constantly controls the pump linear solenoid 18 and controls the amount of fuel discharged from the high-pressure pump 5 into the common rail 4 is electrically protected by the transistor TR5. Therefore, destruction of the transistor TR3 can be prevented. Therefore, the pump linear solenoid 1
8 can be prevented, and the control of the amount of fuel discharged from the high-pressure pump 5 into the common rail can be prevented.

In the present embodiment shown in FIG. 1, only the one-cylinder injector solenoid 36 has been described for the sake of simplicity. For example, as shown in FIG. 6, in the case of the two-cylinder injector solenoid 36, This can be explained by setting the number of the transistor TR2 and the diode D4 to two. Therefore, the present invention is not limited to the number of cylinders.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing an injector drive circuit and a high-pressure pump drive circuit according to one embodiment of the present invention.

FIG. 2 is an overall configuration diagram showing a common rail fuel injection device according to one embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a high-pressure pump according to one embodiment of the present invention.

FIG. 4 is a schematic sectional view showing an injector according to one embodiment of the present invention.

FIG. 5 is a time chart for explaining the operation of the injector drive circuit and the high-pressure pump drive circuit according to one embodiment of the present invention.

FIG. 6 is an electrical configuration diagram showing an injector drive circuit and a high-pressure pump drive circuit according to another embodiment of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 common rail type fuel injection device 3 injector 4 common rail 5 high pressure pump 6 ECU 18 pump linear solenoid (second electromagnetic solenoid) 19 metering valve (electromagnetic control valve) 22 rotary pump 35 two-way valve (injection control electromagnetic valve) 36 Injector solenoid (first electromagnetic solenoid) 40 Constant current source 50 Charge capacitor TR1 Discharge transistor TR2 Switching transistor (first switching means) TR3 transistor (control means) TR4 transistor (second switching means) TR5 transistor (protection) means)

Claims (3)

[Claims] An injector for injecting and supplying high-pressure fuel stored in an accumulator to an internal combustion engine, and a first injection control solenoid valve for controlling a fuel injection timing and a fuel injection amount of the injector. An electromagnetic solenoid, a high-pressure pump for pumping fuel to the pressure accumulation chamber, and a second electromagnetic solenoid provided on an electromagnetic control valve for controlling a fuel discharge amount for discharging fuel from the high-pressure pump to the pressure accumulation chamber. Recovering first energy generated in the first electromagnetic solenoid when the injector is closed, and recovering second energy generated when driving the second electromagnetic solenoid. Accumulator type fuel injection device. 2. A first switching means which is connected in series with the first electromagnetic solenoid, and a power supply is connected to one end of the series circuit, and between the first electromagnetic solenoid and the first switching means. A capacitor that is branched and connected to the capacitor; an energy recovery path that guides the first and second energy to the capacitor; and a second switching unit that is provided in the energy recovery path and that opens and closes the energy recovery path. The accumulator-type fuel injection device according to claim 1, further comprising control means connected in series with the second electromagnetic solenoid to control the second electromagnetic solenoid. 3. The accumulator type fuel injection device according to claim 2, further comprising a protection means connected in parallel with said second electromagnetic solenoid to electrically protect said control means.