JPH0373737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a fuel injection pump for an internal combustion engine, which is provided with a plunger operated by a cam drive device and an injection start timing adjustment device that acts on the cam drive device. and the injection start timing adjustment device has an injection start timing adjustment piston adjustable by the fuel pressure against the force of a return spring, in which case the fuel pressure is synchronous with respect to the fuel injection pump. The feed pump is driven by a feed pump that varies in dependence on the rotational speed and is additionally controllable by a pressure control valve, which is exposed to the fuel pressure on its end side and is spring-loaded. It has a control slide that can be moved in the bore against a force, and there is a constant connection between the pressure-relieving chamber, which receives the spring of the control slide, and the fuel pressure on the end side of the control slide. A connecting hole is provided, and an outflow opening leading from the hole to the return passage is provided on the circumference of the hole accommodating the control slider, and the cross section of the outflow opening extends to the control edge of the control slider. According to the invention, the control slider is gradually opened toward the fuel pressure side when the control slider slides against the force of a spring.

In such a type of fuel injection pump known from DE 190 6 885 A1, the pressure control in the pressure control valve is limited to a constant throttling at low speeds slightly above the starting speed. At subsequent high rotational speeds, this is achieved by additional control of the outflow cross section via a control slide. That is, the pressure control characteristics exhibit quadratic function characteristics for the first section, and extremely linear function characteristics for the second section. In the first section, the increasing fuel quantity is suppressed by a constant cross section and draws a quadratic characteristic line,
The pressure increases accordingly in a quadratic manner with respect to the engine rotational speed (hereinafter simply referred to as rotational speed). As a result, in known fuel injection pumps, the injection start timing is not adjusted as much as possible in the starting speed range, but in the normal speed range, the injection start timing is adjusted by adjusting the necessary control pressure. It is starting to be done. Due to the inflection points that occur in the pressure characteristic line due to the different pressure controls, the specified rotational speed range, above which the injection timing adjustment takes place, can be kept very narrow. This means that the pressure increases significantly with increasing rotational speed until the start-up is interrupted, but then increases only very slightly.

Based on increasingly stringent requirements for toxic components contained in the exhaust gas of internal combustion engines, engine ratings are subject to "exhaust gas optimization" within the engine speed range subject to exhaust gas regulation tests. However, outside this test range, the engine is ``optimized for fuel consumption'' for purely economic reasons. As is well known, exhaust gas and fuel efficiency in diesel engines are mainly affected by injection, particularly by the injection start timing. Emission optimization requires significantly less early adjustment of the engine speed than is necessary for fuel efficiency optimization. Since the test speed range is aimed at low speeds, a flat course of the characteristic line must first be achieved and then a relatively steep course. However, with the pressure control of known fuel injection pumps, it is not possible to obtain such a characteristic line even when transitioning into a corresponding rotational speed range; on the contrary, the bending points obtained in the characteristic line can lead to completely undesired developments. I'll close it.

It is therefore an object of the invention to provide a fuel injection pump with which both exhaust gas optimization and fuel efficiency optimization can be advantageously achieved.

In order to solve this problem, in the configuration of the present invention,
In a fuel injection pump of the type mentioned at the outset, the bore accommodating the control slide is provided with a plurality of outflow openings having different shapes, at least one of these outflow openings comprising: It has a cross section extending in the sliding direction of the control slide, which cross section extends beyond the cross section of the other outlet opening in the sliding direction of the control slide against the spring force.

The fuel injection pump according to the present invention configured as described above has the following advantages over known pumps. This means that initially a flat injection control characteristic curve, which is desired for exhaust gas optimization, is obtained, followed by a significantly steeper characteristic curve section, which is advantageous for fuel economy optimization. Depending on the shape of the outlet cross-section and the opening control profile of this cross-section, different characteristic line profiles for the corresponding rotational speed range can also be obtained in an advantageous manner.
Advantageous embodiments of the invention are set out in the following description and claim 2.

Next, embodiments of the present invention will be described with reference to the drawings.

As is well known, in a diesel engine, fuel injection is performed when the engine piston is within the range of top dead center OT. In this case, the fuel injection start timing is from before top dead center OT to immediately after top dead center OT depending on the rotational speed, that is, usually earlier at high rotational speeds than at low rotational speeds. Whereas the time required by the fuel for the distance between the pump and the nozzle is quite constant regardless of the rotational speed,
The time required for pump discharge and combustion in the engine varies depending on the rotation speed. This time change is compensated for by the injection timing adjustment device. A large part of the working capacity of the injection timing control device is used for this purpose. The remainder of this working capacity is used to improve fuel consumption, power, engine noise and/or exhaust emissions as required in the internal combustion engine. In this case, in particular, the adjustment of the injection timing required for exhaust gas optimization differs significantly from the adjustment for fuel consumption optimization. For exhaust gas optimization, a significantly smaller degree of early adjustment is required than for optimum fuel consumption. Emissions optimization is based on the increasingly stringent requirements of legislators for toxic components in exhaust gases and thus on the basic license of motor vehicles, and fuel consumption optimization is based on increasingly high fuel costs. Since the exhaust gas control law specifies the test range as low and medium engine speeds, only the high engine speed range is a concern for fuel optimization.

FIG. 1 schematically shows a distributor fuel injection pump. A plunger 3 operates within the cylinder bore 2 of the casing 1. This plunger 3 is brought into reciprocating and at the same time rotational movement by means shown schematically against the force of a return spring, not shown. The pump working chamber 4 of the pump includes a vertical groove 5 arranged on the peripheral wall of the plunger 3 and a casing 1.
Fuel is supplied from a suction chamber 7 via a passage 6 extending therein. This fuel supply is performed while the plunger 3 is performing a suction stroke and is located at the bottom dead center. As soon as the passage 6 is closed at the beginning of the compression stroke and after a corresponding rotation of the plunger 3,
The fuel present in the pump work chamber 4 is conveyed to a longitudinal passage 8 extending through the plunger 3. From this vertical passage 8, the fuel is further transferred to a plurality of pressure conduits 1 via branching radial holes 9 and distribution longitudinal grooves 10 (see broken lines) disposed on the outer circumferential surface of the plunger 3.
1. The number of pressure lines 11 corresponds to the number of engine cylinders to be supplied with fuel, and the pressure lines 11 are distributed accordingly around the cylinder bore 2. Each pressure conduit 11 is provided with a check valve 12 that opens in the conveying direction.

Fuel is supplied to the suction chamber 7 from a fuel tank 14 via a feed pump 13. The feed pump 13 is driven at a rotational speed proportional to the engine rotational speed, and is formed as a positive displacement pump, and the discharge amount increases as the rotational speed increases. The pressure in the suction chamber 7 is controlled by controlling a portion of the discharge amount to flow out as will be described in detail later.

A ring slide 16 is assigned to the plunger 3 and operates along it. This ring slider 16 controls the opening of a radial hole 17 connected to the longitudinal passage 8 during the pressure stroke of the plunger 3 and thereby controls the end of the discharge, that is, the amount of fuel transferred from the plunger 3 to the pressure conduit 11. stipulate. The fuel flowing out after the opening control is returned to the suction chamber 7.

The ring slider 16 is moved via an intermediate lever 18. This intermediate lever 18 is pivotable about a shaft 19 inserted immovably into the housing 1 and engages at one end via a head 20 in a recess 21 of the ring slide 16. A centrifugal speed governor (not shown) acts on the other arm of the intermediate lever 18 and serves as a rotational speed signal generator. This intermediate lever 1
8 is furthermore associated with a spring which allows the preload to be easily varied and which acts against the centrifugal force. The fuel consumption determined by the position of the ring slider 16 is determined by the engine speed and the arbitrarily set spring force.

Plunger 3, which acts as a dispensing piston, is attached to pin 2
It is connected to a cam disk 24 via 3, and a protrusion 25 is provided on the lower side of the cam disk 24. The cam disk 24 is rigidly connected to a drive shaft 26 which is driven at a rotational speed synchronous with the engine rotational speed. The cam disc is the roller 2 of the rim 28 with rollers.
7, by means of which the plunger 3 performs a reciprocating movement as already mentioned during rotation of the cam disk 24. The number of protrusions 25 is selected in such a way that, when the cam disk 24 rotates, the plunger 3 has the same number of working plays as the number of cylinders of the internal combustion engine that are supplied with fuel by the fuel injection pump. The roller rim 28 is rotatably supported within the casing 1 and is connected to the injection start timing adjusting piston 30 via the piston rod 29, so that the roller attachment can be adjusted by moving the injection start timing adjusting piston 30. The rim 28 is rotated. As a result, the position of the roller 27 relative to the protrusion 25 changes, and as a result, the discharge start timing, that is, the compression stroke of the plunger 3 relative to the rotation angle of the drive shaft 26 changes, and thus the fuel injection start timing changes. The injection start timing adjusting piston 30 is loaded by the fuel pressure in the suction chamber 7 . In other words, this fuel pressure is transferred to the piston 3 via the passage 31.
It also controls the upper chamber 32 of 0. Depending on the level of pressure, the injection timing adjustment piston 30 is moved more or less against the force of the return spring 33, so that the injection timing can be changed accordingly in each case. The chamber 34 accommodating the return spring 33 is connected to the fuel tank 14 by a pressure relief passage 35.
or to the suction conduit 36 of the feed pump 13.

As mentioned above, the draining of a portion of the delivery volume takes place via the pressure control valve 38. This pressure control valve 38 is controlled by a control slide 39 which is moved against a return spring 40 by the discharged fuel.
It is operated by. In other words, this control slider 3
By moving 9, the outflow opening is controlled to be opened larger or smaller. From this outlet opening, which will be described in more detail with reference to FIGS. 3 and 4, a return passage 42 leads to the suction conduit 36 of the feed pump 13. The feed pump 13 has a pressure line 53 which opens into the suction chamber 7 and which leads to a pressure control valve 3.
A control conduit 44 leading to 8 branches off.

In the diagram shown in FIG. 2, the vertical axis shows the pressure p, which is a reference for injection adjustment, and the horizontal axis shows the engine speed n. The illustrated characteristic line corresponds to the above-mentioned course of the desired injection timing adjustment, which has an inflection point. Until the rotational speed n1 is reached, only a pressure p1 is available which increases relatively little with the rotational speed and causes an early adjustment. Above this rotational speed n1, the pressure then rises relatively steeply, so that the above-mentioned fuel consumption optimization can be achieved by an early regulation that increases rapidly with rotational speed.

FIG. 3 shows an exemplary embodiment of the pressure control valve 38 in a longitudinal section, and FIG. 4 shows the casing 43 shown in FIG. 49 as seen from the inside.

As shown in FIG.
has a longitudinal bore 49 for receiving a control slide 39 and a return spring 40. control slider 39
A pushed-in ring 45 serves as a stop for the starting position. The return spring 40 is supported on the side opposite the control slide 39 in a sleeve 46 which is likewise pushed in. The fuel passes through the ring 45 in the direction of arrow K and reaches the control slider 3.
9, a portion of the fuel then exits through a hole 47 provided in the center of the control slide 39.

As can be seen in particular from FIG. 4, the two outlet openings 50 are arranged at right angles to the travel direction of the control slide 39, and the two outlet openings 51 are arranged parallel. With this type of arrangement, until the rotational speed n1 is reached, that is to say in the course of the first section of the characteristic line shown in FIG. The opening is controlled in relation to. After this process, control slider 3
If 9 is moved further, the outflow cross section of the pressure control valve increases by the additional cross section of the outflow opening 51. In this case, the pressure control characteristic line shows that from this point on, the pressure p increases significantly as the rotational speed n increases. This corresponds to the second section of the characteristic line shown in FIG.

The objective is to make relatively weak early adjustments to the engine speed in the first category for exhaust gas optimization, and later to make strong early adjustments to the engine speed for fuel consumption optimization. To achieve this, it is also possible to choose other cross-sectional shapes of the outflow openings, for example triangular, diamond-shaped, etc.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a fuel injection pump equipped with an injection adjustment device and a pressure control valve, FIG. 2 is a diagram showing injection adjustment characteristic lines, and FIG. 3 is a longitudinal section showing one embodiment of the pressure control valve. FIG. 4 is a developed view of the valve cylinder portion in which the outflow opening is arranged. 1...Casing, 2...Cylinder hole, 3...
plunger, 4...pump working chamber, 5...vertical groove,
6... Passage, 7... Suction chamber, 8... Vertical passage, 9
... Radial hole, 10 ... Distribution vertical groove, 11 ... Pressure conduit, 12 ... Check valve, 13 ... Feed pump, 14 ... Fuel tank, 16 ... Ring slider, 17 ... Radial hole, 18... intermediate lever,
19...Shaft, 20...Head, 21...Notch,
23...Pin, 24...Cam disc, 25...Protrusion, 26...Drive shaft, 27...Roller, 28...
Rim with roller, 29... Piston rod, 30...
...Injection start timing adjusting piston, 31...Passage, 3
2... Chamber, 33... Return spring, 34... Chamber, 35
... Pressure relief passage, 36 ... Suction conduit, 38 ... Pressure control valve, 39 ... Control slider, 40 ... Return spring, 42 ... Return passage, 43 ... Casing,
44... Control conduit, 45... Ring, 46... Sleeve, 47... Hole, 49... Vertical hole, 50, 51
...Outflow opening, 53...Pressure conduit, p...Pressure,
n...engine speed, K...arrow.

Claims (1)

[Scope of Claims] 1. A fuel injection pump for an internal combustion engine, which includes a plunger 3 operated by cam drive devices 24 to 28, and injection start timing adjustment devices 29 to 32 that act on the cam drive device. The injection start timing adjustment device is provided with a return spring 33 depending on the fuel pressure.
It has an injection timing piston 30 which can be adjusted against the force of the fuel injection pump, in which case the fuel pressure is dependent on the rotational speed by means of a feed pump 13 which is driven synchronously with respect to the fuel injection pump. and change,
and is additionally controllable by a pressure control valve 38 which is exposed to the fuel pressure on its end side and has a control slide 39 movable in a bore 49 against the force of a spring 40. A connection hole 47 is provided which constantly connects the pressure relief chamber receiving the spring 40 of the control slider with the fuel pressure on the end face side of the control slider. On the circumference of the hole 49 accommodating the slider 39, an outflow opening leading from the hole to the return passage 42 is provided, the cross-section of which extends into the control slider 39.
The bore 49 accommodating the control slide 39 is of the type such that the control edge of the control slide gradually opens towards the fuel pressure side during sliding of the control slide against the force of the spring 40. A plurality of outflow openings 50, 51 having different shapes are provided, at least one outflow opening 51 of these outflow openings being connected to the control slider 39.
has a cross section extending in the sliding direction of the control slide 39, which cross section extends beyond the cross section of the other outlet opening 50 in the sliding direction against the force of the spring 40 of the control slide 39. A fuel injection pump for an internal combustion engine, characterized by: 2 the outflow openings have a rectangular cross-section, and a portion 50 of these outflow openings is connected to the control slide 3
9 are arranged perpendicularly to the sliding direction and a part 51 is arranged parallel to the sliding direction, and when the control slider is shifted with increasing rotational speed, the first part 51 is arranged perpendicularly to the sliding direction. The fuel injection pump according to claim 1, wherein the outflow opening 50 is controlled to be gradually opened, and when the fuel pressure is equal to or higher than a predetermined rotation speed n1, only the outflow opening 51 extending in parallel is controlled to be gradually opened. .