JPH0154548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device, and particularly to a spool valve that drives a plunger using hydraulic pressure to inject fuel, and controls the timing at which hydraulic pressure is applied to the plunger. It is suitable for use in a fuel injection device equipped with a supply pressure source, such as a type controlled by a fuel injection device.

This type of fuel injection device has been attracting attention in recent years because of its large degree of controllability and injection performance that increases the fuel efficiency of an engine. In this type of device, a constant displacement pump is generally used as a hydraulic pressure supply source for driving the plunger. However, conventional hydraulic pressure supply control using this constant displacement pump has been adjusted in accordance with the maximum required oil amount, which has had the drawback of significantly deteriorating fuel efficiency, especially at times of light negative pressure. Engine losses caused by liquid supply in medium-sized engines account for approximately 15% of all engine losses, and there is a great need for countermeasures.

In order to eliminate the above-mentioned drawbacks, the hydraulic pressure supply for driving the plunger may be successively corrected to the required amount depending on the operating state of the engine. However, in this case, in order to supply hydraulic pressure to each cylinder without variation, that is, to maintain the pressure source at a stable pressure level, the amount of oil supplied to the hydraulic pressure source must be increased by the required amount + %. , it is necessary to overflow the excess oil amount.

In order to achieve this purpose, it is possible to use variable displacement pumps used in hydraulic equipment, etc., but since the operating conditions are pulsating waves of several milliseconds, the response is insufficient and it is not practical. Not on point. Therefore, in the present invention, we focused on the fact that this type of fuel injection device uses a controller such as a microcomputer, and utilized its functions to achieve the above objectives, as well as to perform more advanced injection pressure control. It is designed so that it can be implemented. Description will be given below with reference to the accompanying drawings.

The injector 1 shown comprehensively in FIG.
a spool valve 25 composed of a bore 2, a spool 3 that freely slides therein, and a spring 3a;
A fuel compression means 26 consisting of one large-diameter piston 6 and a plunger 7 that slide in bores 4 and 5, respectively, and a normal fuel injection nozzle 8 loaded by a spring 8a. 2 position - 2 port solenoid valve for control 9,1
It has 0,11. A fuel chamber 12 formed by the lower end surface of the plunger 7 and the bore 5 is connected to a check valve 13.
It is connected to the supply pressure source 14 via a diameter line, and is also connected to the nozzle 8 at the same time. On the other hand, a hydraulic oil chamber 15 formed by the left end surface of the spool 3 and the bore 2
is connected to the supply pressure source 14 through the first passage 30 and the first solenoid valve 9, and is connected to the low pressure fuel tank 1 through the second passage 40 and the second solenoid valve 10.
Further, one port a of the spool valve 25 communicates with the supply pressure source 14, and the other port b communicates with the fuel tank 1 via the throttle 22 and the third solenoid valve 11.
6. The hydraulic oil chamber 21 formed by the upper surface of the piston 6 and the bore 4 has two ports a and b.
selectively communicated with either one of the two.

The configuration of the supply pressure source 14 is as follows. Fuel from the fuel tank 16' passes through a filter 17,
The primary pump 90 directs the fuel to the fuel inlet of the pump 18 . The discharge pressure of the primary pump 90 is maintained at a constant pressure by a pressure regulating valve 100. Fuel is pumped by pump 18 and sent to surge tank 20 by collection pipe 70. The surge tank 20 is connected to the tank 16'' (low pressure section) via an overflow passage 81 and a 2-position/2-port solenoid valve 80.The pump 18 is provided with an adjustment rod 51 for varying the discharge amount.Adjustment rod 51
A lever 53 is connected to the right end of the lever 53 via a freely rotatable fulcrum 52. The lever 53 is pivotally connected to the moving core 59 via a pivot point 54 . Lever 53
has a fulcrum 55 at a position opposite to the fulcrum 52 with the pivot point 54 as the center. The fulcrum 55 is swung by a fork lever 56 formed on an adjusting lever 58 that rotates about the fulcrum 57. Incidentally, as is well known, the adjuster steering lever 58 is adjusted by a method not shown in the drawings to take a position depending on the engine load. Also, moving core 5
There are springs 62 and 63 at both ends of the core 59, and the core 59 is stationary at a position where the spring forces are balanced. A stator core 61 is provided at the right end of the moving core 59, and the stationary position of the moving core 59 can be changed by applying electricity.

23 is a controller that controls energization of four electromagnetic valves 9, 10, 11, and 80 based on signals from sensors _S1 to _S5 , which will be described later. Note that since the injectors 1 are provided for each cylinder (not shown), the number of injectors 1 is the same as the number of engine cylinders.

FIG. 2 shows a block diagram regarding the sensors S ₁ to _{S 6} , the controller 23, and the solenoid valves 9 to 11 and 80. S ₁ indicates the engine speed, S ₂ indicates the amount of accelerator pedal depression, S ₃ indicates the engine temperature, S ₄ indicates the engine cylinder mark, and S ₅ indicates emergency abnormalities such as fuel leaks from piping or engine overruns. These are sensors that detect each state. Further, S ₆ is a pressure sensor that detects the fluid pressure level of the surge tank 20 of the pressure source 14 .

In the controller 23, P ₁ indicates an injection amount setting circuit, P ₂ indicates an injection start timing setting circuit, and P ₄ indicates a pressure source liquid pressure level setting circuit. A ₁ is sensor S ₁ ,
a calculation circuit that determines the injection amount based on the signal of S ₂ ,
A ₂ is a calculation circuit that determines the injection start timing based on the signal from sensor S ₃ , A ₄ is a calculation circuit that determines the pressure source liquid pressure level based on the signal from sensor S ₆ , and A ₃
is an output amplifier circuit. Specifically, calculation circuit A ₁
is the energization time to the third solenoid valve 11, calculated by the calculation circuit.
A ₂ calculates the timing deviation of the start of energization to the first solenoid valve 9 with respect to the cylinder mark, and the calculation circuit A ₄ calculates the valve opening frequency to the solenoid valve 80 . In addition, the output amplification circuit
_A3 determines the crank position of the engine and energizes the solenoid valves 9, 10, and 11 of the required cylinders at the required timing, and also energizes the solenoid valve 80 at the required valve opening frequency. Normally, the first and third solenoid valves 9 and 11 are energized for a certain period of time, but in response to an emergency signal from sensor S ₅ , the energization may be stopped completely, or
Turn on the power and leave it on. Furthermore, the hydraulic pressure in the surge tank 20 of the pressure source 14 is released by energizing the electromagnetic valve 80 at a constant voltage or by stopping the energization in an emergency.

Next, the operation of the apparatus shown in FIG. 1 will be explained.

By bringing the two ports of the first electromagnetic valve 9 into a conductive state (hereinafter referred to as "open") from the state shown in FIG. , the spool 3 is displaced to the right by overcoming the spring 3a. At this time, the second solenoid valve 10 is closed. By displacing the spool 3 to the right, port b closes, and then port a
will be held. As a result, the hydraulic oil chamber 21 is connected to port a.
The fuel chamber 12 is brought into communication with the pressure source 14 via the nozzle 8, and the pressure is increased according to the area ratio between the piston 6 and the plunger 7, and the fuel in the fuel chamber 12 is injected from the nozzle 8.

At this time, the check valve 13 prevents the compressed fuel from being returned to the pressure source. Next, by returning the first solenoid valve 9 to the closed state and then opening the second solenoid valve 10, the fuel in the hydraulic oil chamber 15 is transferred to the tank 16.
, and the spool 3 is returned to the left again by the force of the spring 3a. By displacement of spool 3 to the left, port a is closed, followed by port b
will be held. Then, the fuel in the hydraulic oil chamber 21 is
The liquid is discharged into the tank 16 through port b only during the time when the solenoid valve 11 is open. As the fuel in the hydraulic oil chamber 21 is released, the piston 6 and plunger 7 are pushed back upward by the pressure in the fuel chamber 12, and the fuel is then injected from the pressure source 14 through the check valve 13. The fuel to be used is led to the fuel chamber 12.

From the controller to the first to third solenoid valves 9,1
The signals to 0 and 11 will be explained in chronological order as follows. That is, in FIG. 3, at time A, the first solenoid valve 9 (top diagram) opens and injection operation starts, and after the spool 3 moves to the right end, the first solenoid valve 9 opens at time B. close. Thereafter, by opening the second electromagnetic valve 10 (middle diagram) at time C, the spool 3 returns to its position, allowing metering.
Thereafter, at time D, the second solenoid valve 10 is closed. Next, at time E, when the third electromagnetic valve 11 (bottom diagram) is opened, the piston 6 and plunger 7 begin to return, metering is started, and desired metering is completed at time F. Then, time A is variably controlled based on signals from sensor _S1, etc. to optimize the injection timing, and times E and F are variably controlled to perform metering.

Next, the operation of the pressure source 14 will be explained. The hydraulic pressure level of the surge tank 20 is set by adjusting the overflow amount from a control valve such as the electromagnetic valve 80, so an optimal overflow amount is required to efficiently ensure the hydraulic pressure level. That is, although the amount of overflow from the solenoid valve 80 is set by the hydraulic pressure level of the surge tank 20, engine speed, engine load, etc., the amount of overflow is ultimately regulated by the opening frequency of the solenoid valve 80. , there is an optimum valve opening frequency depending on the various factors mentioned above. Therefore, in order to maintain this optimal valve opening frequency, that is, to ensure high efficiency and the best hydraulic pressure level, the position of the adjuster steering lever is adjusted according to the engine load using a known method as described above, and the coil The moving core 59 is moved by magnetic force according to the applied voltage value at the stator core 61
is finely adjusted to a balanced position with the springs 62 and 63, and in this way, the discharge amount of the pump 18 is adjusted to an amount that matches the required oil amount.

As is clear from the above description, the surge tank 20 functions as a pressure accumulator that accumulates the pressure from the high pressure pump 18.

In this embodiment, an azimuth steering lever 58 is provided which is adjusted according to the engine load. It is also possible to control the discharge amount of the pump 18 using only the electromagnetic adjustment section without providing a lever.

Furthermore, in order to control the injection performance according to the combustion state of the engine and perform optimal injection, it is also possible to utilize the relationship shown in FIG. 4. That is,
In general, the pressure source fluid pressure level L, injection pressure P, and injection period T have a relationship as shown in Fig. 4.Using this, the optimum injection pressure is set based on information signals such as engine speed and load. and duration can also be obtained by adjusting the pressure source hydraulic level.
It goes without saying that the setting of the pressure source liquid pressure level L can be carried out by the above-mentioned method by feedback from the output of the sensor _S6 .

In this way, by feeding back the output of the pressure source hydraulic pressure sensor _S6 to the opening frequency of the electromagnetic valve that opens and closes at high frequency, a stable hydraulic pressure level can be ensured.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel injection device according to the present invention, FIG. 2 is a block diagram explaining the operation of various sensors, controllers, and electromagnetic valves shown in FIG. 1, and FIG. A pulse diagram chronologically explaining the operation of each electromagnetic valve, and FIG. 4 a graph showing the relationship between the hydraulic pressure level, injection pressure, and injection period. 3... Spool, 6... Piston, 7... Plunger, 8... Fuel injection nozzle, 14... Supply pressure source, 18... Supply pump, 25... Spool valve, 26... Fuel compression means, 81... ...overflow passage, S ₆ ...pressure sensor.

Claims (1)

[Claims] 1. A supply pressure source having a high-pressure pump that pumps high-pressure liquid and a pressure accumulator that accumulates pressure of the pumped liquid from the high-pressure pump, and a compressor that operates independently of the operation of the high-pressure pump in response to the liquid pressure. A fuel injection device having a fuel injection nozzle that injects fuel, a pressure sensor that detects the pressure of the supply pressure source, an overflow passage that connects the supply pressure source to a low pressure section, and a pressure sensor configured to respond to an output signal of the pressure sensor. It has a control valve that opens and closes an overflow passage, and a control device that outputs an activation signal for the control valve in response to the output of the pressure sensor, and adjusts the actual pressure to a predetermined pressure source pressure level for each operating condition. A fuel injection device characterized in that source pressure is maintained.