JPH0681936B2 - Fuel injector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention (1) Field of Industrial Application The present invention relates to a fuel injection device mainly used for directly injecting fuel into a combustion chamber of a diesel engine,
In particular, a plunger-type injection pump that is operated by a camshaft that works in conjunction with the crankshaft of the engine and that can discharge a fixed amount of fuel each time it is operated, and the discharge side of this injection pump, communicate with the discharge pressure of the injection pump. Relates to an improvement provided with a fuel nozzle having a needle valve that opens an injection hole when the value becomes equal to or more than a predetermined value, and an injection amount adjusting device that adjusts a fuel injection amount from the fuel nozzle.

(2) Prior Art Such a fuel injection device is already known as disclosed in, for example, Japanese Patent Application Laid-Open No. 58-204962, and in the fuel injection device, an injection amount adjusting device is installed in an injection pump. A first solenoid valve provided in a passage extending from the discharge side to the injection nozzle;
A second electromagnetic valve is provided in a passage extending from the injection nozzle to the suction side of the injection pump, and the fuel injection amount from the injection nozzle is adjusted by controlling the opening / closing timing of these electromagnetic valves.

(3) Problems to be Solved by the Invention Since the adjustment of the injection amount by the conventional fuel injection device is performed by controlling the opening / closing timing of the two solenoid valves during an extremely short operation period of the injection pump, the solenoid valve In addition, high responsiveness is required for the electronic control device that controls the device, and the cost of the entire device tends to increase inevitably.

The present invention has been made in view of the above circumstances, and makes it possible to control the injection amount adjustment device during a non-operation period that is much longer than the operation period of the injection pump, and yet at a low cost, with high operating accuracy. An object is to provide an injection device.

B. Structure of the Invention (1) Means for Solving the Problems To achieve the above object, according to the present invention, a camshaft that is interlocked with a crankshaft of an engine is operated, and a fixed amount of each operation is performed. A plunger type injection pump capable of discharging fuel, a fuel nozzle having a needle valve which communicates with the discharge side of the injection pump and opens a nozzle hole when the discharge pressure of the injection pump becomes a predetermined value or more, and the fuel from the fuel nozzle. In a fuel injection device having an injection amount adjusting device for adjusting the injection amount,
The injection amount adjusting device includes a cylinder, a metering piston that is fitted into the cylinder and divides the inside into a first chamber that communicates with a pressure fluid source and a second chamber that communicates with a discharge side of the injection pump, and an injection pump During the operation period, a predetermined amount of fluid is supplied from the pressure fluid source to the first chamber through the normally closed solenoid valve to advance the metering piston from the backward limit by a predetermined amount. And means for allowing the metering piston to retract to the retracted limit in order to accommodate the part in the second chamber.

(2) fuel injection quantity Q from the operation for the injection nozzle, the fuel discharge amount to Q ₁ from the injection pump (constant), the amount of fuel Q ₂ absorbed into the second chamber by retraction of the piston in the injection amount adjusting device Further, Q ₂ corresponds to the amount of filling the first chamber with the fluid of the pressure fluid source during the inoperative period of the injection pump, so the injection amount Q is adjusted by controlling the filling amount. be able to.

In particular, the control of the fluid filling amount in the first chamber can be performed by a simple valve opening control for only one solenoid valve corresponding to the pump during a non-operation period that is much longer than the operation period of the injection pump. Therefore, the injection amount can be adjusted accurately even if the means for filling the fluid into the first chamber does not have the responsiveness of the special altitude. Further, it suffices to provide only one solenoid valve between the first chamber and the pressure fluid source, and furthermore, since it is not directly exposed to the high discharge pressure of the injection pump, a special high pressure resistance is not required.

(3) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 shows a fuel supply system of a diesel engine. During operation of the engine, the fuel pump 1 stores fuel in a fuel tank 2. It is sucked up and supplied to the constant pressure channel 3. The fuel pressure in the constant pressure passage 3 is always kept constant by a known pressure regulating valve 4, and the surplus fuel is returned to the fuel tank 2 through the return passage 5.

The fuel in the constant pressure passage 3 is introduced into the unit injector 6 mounted on the cylinder head of the engine, where it is pressurized to a high pressure and directly injected into the combustion chamber of the engine. The fuel injection amount is adjusted by the injection amount adjusting device 7, and the injection timing is adjusted by the injection timing adjusting device 8. Further, these adjusting devices 7 and 8 are controlled by the electronic control device 9 according to the operating conditions of the engine, for example, the number of revolutions, the load, the temperature and the like.

The injection amount adjusting device 7 uses the constant pressure passage 3 as its working fluid.
Fuel is supplied through the branch channel 10.

In FIG. 2, the unit injector 6 is configured by integrally connecting a plunger type injection pump 11 and an injection nozzle 12.

The injection pump 11 includes a vertical cylinder 14 fixedly provided in an intermediate portion of an injector body 13, and a plunger that is inserted into the cylinder 14 and defines a pump chamber 15 below the cylinder.
16 and. A return spring 18 is contracted between a retainer 17 attached to the upper end of the plunger 16 and the injector body 13, whereby the plunger 16 is urged in the volume expanding direction of the pump chamber 15. Further, a cup-shaped cam follower 19 for bringing the inner end wall into contact with the retainer 17 is slidably fitted on the upper end portion of the injector body 13, and the crankshaft (not shown) of the engine is attached to the upper end surface of the cam follower 19. The cam 20a of the cam shaft 20 that rotates in conjunction with is engaged.

An annular introduction chamber 21 is formed between the injector body 13 and the cylinder 14 and communicates with the constant pressure passage 3. An intake port 23 that communicates between the introduction chamber 21 and the pump chamber 15 is provided on the side wall of the cylinder 14. Drilled. The suction port 23 is hidden by the side surface of the plunger 16 while the plunger 16 is descending.

On the other hand, on the plunger 16, a slope 24 inclined at a constant angle with respect to the axis thereof is formed at the lower end, and a slit 25 parallel to the slope 24 is cut on the peripheral wall, and the slit 25 communicates with the pump chamber 15. A communication recess 26 is formed in the center of the lower end surface. The distance between the slope 24 and the slit 25 is the cam 20a.
It is set to be smaller than the pressing amount given to the plunger 16 of.

A pinion 27 is rotatably fitted to the outer periphery of the cylinder 14, and the pinion 27 is connected to the plunger 16 via a joint 28 in the cam follower 19. Joint
Reference numeral 28 is a publicly known one that allows the plunger 16 to move up and down and can transmit the rotation of the pinion 27 to the plunger 16. A rack 29 slidably supported by the injector body 13 is meshed with the pinion 27, and the injection timing adjusting device 8 is connected to the rack 29.

The injection nozzle 12 has first, second and third intermediate members 31, 32, 33 and a nozzle pipe 34 which are sequentially arranged in a lower portion of a cylinder 14, and these are screwed to a lower portion of an injector body 13. It is held by the cap 35. A needle valve 37 that opens and closes a nozzle hole 36 at the tip of the nozzle pipe 34 is mounted. This needle valve 37
Has an upper end protruding into a spring chamber 38 provided between the second and third intermediate members 32 and 33, and a valve spring 39 for urging the protruding end in the valve closing direction is housed in the spring chamber 38.

The needle valve 37 has a large diameter pressure receiving portion 37a slidably supported on the nozzle tube 34, and the lower end surface of the pressure receiving portion 37a faces the pressure chamber 34a in the nozzle tube 34. The pressure chambers 34a are
The pump chamber 15 is constantly communicated with through a series of discharge passages 40 provided in the third intermediate members 31 to 33, and is communicated with the injection hole 36 only when the needle valve 37 is opened.

The injection amount adjusting device 7 includes a cylinder 42 fixed to a mounting portion 41 extending from one side surface of an intermediate portion of the injector body 13, and a stepped measuring piston fitted in the cylinder 42.
With 43. In the cylinder 14, there are a first chamber 44 facing the outer end surface of the large diameter portion 43a of the measuring piston 43, an atmospheric pressure chamber 46 facing the inner end surface of the large diameter portion 43a, and a second chamber 45 facing the outer end surface of the small diameter portion 43b. A return spring 47, which is formed and biases the measuring piston 43 toward the first chamber 44, is contracted in the atmospheric pressure chamber 46. Due to the force of the return spring 47, the measuring piston 43 is normally held in the retracted limit where it abuts against the end wall of the first chamber 44.

The first chamber 44 is connected to the branch flow passage 10 via an electromagnetic valve 48 mounted on the upper surface of the mounting portion 41, and the second chamber 45 is connected to the discharge passage 40.

The solenoid valve 48 is a normally-closed type that opens only when the solenoid 48a is energized.
The valve opens when the pressure in the chamber 44 rises above a predetermined value. The valve opening pressure is set lower than the valve opening pressure of the needle valve 37 of the injection nozzle 12. Thus, the normally closed solenoid valve 48
And a check valve mechanism in the valve 48 (that is, the valve is opened when the pressure in the first chamber 44 rises above a predetermined value smaller than the valve opening pressure of the needle valve 37 even when the renoid 48a is deenergized as described above. The internal mechanism for achieving the check function described above) forms the means A of the present invention.

Next, the operation of this embodiment will be described.

During operation of the engine, the plunger 16 of the injection pump 11 reciprocates up and down by the pushing action of the rotating cam 20a and the returning action of the return spring 18. Thus, when the plunger 16 is in the raised position, the fuel from the constant pressure passage 3 fills the pump chamber 15 via the introduction chamber 21 and the suction port 23, and further passes through the discharge passage 40 to the second chamber 45 and the pressure chamber 34a. And so on.

Thus, during the period when the plunger 16 occupies the raised position,
When the electronic control unit 9 energizes the solenoid valve 48 for a time corresponding to the operating condition of the engine, and the solenoid valve 48 is closed accordingly, fuel is fed from the constant pressure passage 3 through the branch passage 10 to the first chamber 44. Supplied. As a result, the pressure of the constant pressure passage 3 acts equally on both end surfaces of the measuring piston 43, but the pressure receiving surface of the measuring piston 43 facing the first chamber 44 is greater than the pressure receiving surface facing the second chamber 45. Is also wide, the thrust generated by the difference in pressure receiving area causes the measuring piston 43 to move forward from the backward limit to the side of the second chamber 45, and in the end, the first chamber 44 receives a quantity of fuel corresponding to the energization time of the solenoid valve 48. Is filled.

After that, due to the arrival of the injection timing, the cam 20a moves the plunger 1
When 6 is pushed down, while the side surface of the plunger 16 closes the suction port 23, that is, the lower end edge of the plunger 16 is the suction port.
The pump chamber 15 is pressurized by the plunger 16 and discharges a fixed amount of fuel to the discharge passage 40 after the slit 25 faces the suction port 23 after passing through the open end of 23.

The discharge pressure of the pump chamber 15 is supplied to the second chamber via the discharge passage 40.
45 to the pressure chamber 34a and the measuring piston 43 to the first chamber 44
The pressure receiving portion 37a of the needle valve 37 to the valve opening side,
Since the valve opening pressure of the solenoid valve 48 is set lower than that of the needle valve 37, the solenoid valve 48 first opens due to the rising pressure of the first chamber 44, and the first chamber 44 to the branch flow passage 10 is opened. Since the backflow of fuel is allowed, the metering piston 43 is pushed back to the initial retract limit. Due to the backward movement of the metering piston 43, a part of the fuel discharged from the pump chamber 15 is absorbed in the second chamber 45.

When the metering piston 43 reaches the retreat limit, the discharge pressure of the pump chamber 15 further rises, and the needle valve 37 opens this time, so the remaining discharge fuel is injected from the injection hole 36 into the combustion chamber of the engine.

Therefore, the fuel injection amount Q into the combustion chamber is
The discharge amount Q ₁ amount obtained by subtracting the absorption amount Q ₂ of the second chamber 45 from the (constant) to the discharge passage 40 from. Moreover, Q ₂ is a measuring piston
Since it is proportional to the backward movement amount of 43, in other words, the forward movement amount of the piston 43, that is, to the energization time of the solenoid valve 48, the injection amount Q can be freely controlled by controlling the energization time according to the operating conditions of the engine. Can be adjusted to.

In particular, since the control of the energization time of the solenoid valve 48 is performed during a long period during which fuel injection is not performed, there is a sufficient margin in the control time, and the electronic control unit 9 and the solenoid valve 48 have some response delay. Even if there is, the metering piston 43 can be reliably operated to a desired position, and the desired injection amount Q can be accurately obtained.

In addition, the relatively expensive solenoid valve 48 can be used with one unit injector for 61 unit injectors.
Since it is not exposed to the high discharge pressure of 11, high pressure resistance is not required, which can greatly contribute to cost reduction.

On the other hand, the fuel injection timing is adjusted as follows. First, when the plunger 16 is in the upper limit position, the injection timing adjusting device 8 rotates the pinion 27 via the rack 29, and the joint 16 rotates the plunger 16 at the same angle. Then, since the lower end surface of the plunger 16 is the slope 24, the distance from the lower end of the plunger 16 to the suction port 23 changes. And when the distance increases,
When the plunger 16 is pushed down by the cam 20a, when the suction port 23 is closed by the side surface of the plunger 16,
That is, the timing of starting pressurization of the pump chamber 15 is delayed. When the fuel injection timing is delayed, and conversely, when the distance is reduced, the injection timing is advanced.

Even when the rotation of the plunger 16 is adjusted, since the slope 24 and the slit 25 are parallel to each other, the effective pressurization stroke of the plunger 16 with respect to the pump chamber 15 does not change, and therefore the pump chamber 15 to the discharge passage 40 does not change. The discharge amount of fuel is always constant.

In the above, the constant pressure channel corresponds to the pressure fluid source of the present invention.

C. Effects of the Invention As described above, according to the present invention, the injection amount adjusting device is provided with a cylinder, a first chamber fitted in the cylinder and connected to the pressure fluid source inside the cylinder, and a discharge side of the injection pump. While the metering piston that divides into the continuous second chamber and the injection pump is inoperative, a predetermined amount of fluid is controlled from the pressure fluid source to the first chamber through the normally closed solenoid valve to advance the metering piston from the backward limit to the predetermined amount. And a means for allowing the metering piston to retract to the retracted limit in order to accommodate a part of the fuel discharged from the injection pump in the second chamber when the injection pump is operating, so that it is much longer than the operating period of the injection pump. During the non-operation period, the amount of fluid filled from the pressure fluid source to the first chamber is controlled and the amount of fuel injected from the injection nozzle is adjusted by simply opening control of only one solenoid valve corresponding to the pump. Can and want Means for filling the fluid into the first chamber is capable of precise adjustment of the injection quantity without with special high responsiveness. Further, it is sufficient to provide only one solenoid valve between the first chamber and the pressure fluid source, and further, since it is not directly exposed to the high discharge pressure of the injection pump, no special high pressure resistance is required. As described above, in combination with the effect that it does not need to have a special high level of responsiveness, it can greatly contribute to the simplification of the structure and further to the cost reduction.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic view of a fuel system of a diesel engine equipped with the fuel injection device of the present invention, and FIG. 2 is a vertical cross-sectional view of a main part thereof. 3 ... Constant pressure passage as pressure fluid source, 6 ... Unit injector, 7 ... Injection amount adjusting device, 11 ... Injection pump, 12 ... Injection nozzle, 16 ... Plunger, 42 ... Cylinder, 43 ... … Measuring piston, 44 …… First chamber, 45 …… Second
Chamber, 48 ... Solenoid valve, A ... Means

Claims (2)

[Claims] 1. A plunger type injection pump (11) which is operated by a cam shaft (20) which is interlocked with a crank shaft of an engine and can discharge a fixed amount of fuel at each operation, and the injection pump (11). The needle valve (3) that communicates with the discharge side of the injection valve and opens the injection hole (36) when the discharge pressure of the injection pump (11) exceeds a specified value.
Fuel nozzle (12) with this fuel nozzle (1)
Injection amount adjusting device (7) for adjusting the fuel injection amount from 2)
In the fuel injection device including the: (1), the injection amount adjusting device (7) includes a cylinder (42) and a first chamber (44) fitted in the cylinder (42) and connected to the pressure fluid source (3) inside. ) And a metering piston (43) that divides into a second chamber (45) connected to the discharge side of the injection pump (11), and during the inoperative period of the injection pump (11), from the pressure fluid source (3) to the first chamber ( A fixed amount of fluid is controlled to flow through the normally closed solenoid valve (48) to the piston 44 to move the metering piston (43) forward from the backward limit by a predetermined amount, and when the injection pump (11) is operating, the injection pump (1)
A fuel injection device comprising: a means (A) for allowing the metering piston (43) to retract to a retracted limit so as to accommodate a part of the discharged fuel of 1) in the second chamber (45). 2. The fuel injection device according to claim 1, wherein the pressure fluid source is a constant pressure channel (3) to which fuel pressurized to a predetermined pressure is supplied.