JPH02241974A - Constant pressure bypass valve for fuel injection device - Google Patents

Abstract

PURPOSE: To provide a two-way delivery relief valve which can be manufactured in a remarkably simple manner, and for which a quality during the manufacture can be ensued or enhanced, by fixing a casing sleeve through deformation of a valve element body, and by forming a valve element body and a valve seat member from hard materials, and the casing sleeve from a soft material. CONSTITUTION: A casing sleeve 6 is made into contact with a step part 8 while is pressed and slipped by an enlarge section 16 through the intermediary of a valve element body 5, and embossing is carried out in an annular groove 17 for fixing the valve element body 5. The casing sleeve 6 is made of a material which is soft and which can be easily subjected to embossing in order to prevent the sleeve casing 6 from being directly exposed to mechanical load. Further, a valve seat member 12 in the isobaric relief valve is fastened and fixed by deforming the casing sleeve 6. Thus, the manufacture of the relief valve can be remarkably simplified, and the quality thereof during manufacture can be ensured or improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an isobaric relief valve for installation between an injection nozzle and an injection pump pressure chamber in a fuel pressure passage of an injection device for an internal combustion engine, the pressure connecting the fuel pressure channel downstream and upstream of the pressure valve seat with a pressure valve member that is open in the conveying direction against the force of a valve spring and cooperates with the pressure valve seat of the pressure valve member by means of a valve member body; a relief passageway extending within the pressure valve member;
a relief valve which is opened against the direction of conveyance and has a relief valve member, which controls the relief passage, and which jointly defines the opening pressure of the relief valve, acting on the relief valve member on the one hand and on the relief valve member on the other hand; a coil spring supported on opposing support surfaces;
a valve seat member supporting a valve seat of the relief valve member; and a casing sleeve disposed on the valve member body of the pressure valve member, the free end of the casing sleeve for securing the valve seat member to the valve member body. Relates to a type that is deformed in the radial direction.

PRIOR ART Isobaric relief valves of the type described above are used in order to always obtain the same pressure conditions before each new conveyance of fuel from the fuel injection pump to the injection nozzle in the pressure line, i.e. in accordance with engine speed and load. is used in order to obtain the same pressure conditions irrespective of the fuel delivery rate and the delivery quantity, in particular also for large delivery quantities per unit time, such as in the case of full load. In particular, during injection pauses, the after-injection of fuel into the combustion chamber, for example due to pressure waves, must be interrupted by reducing the pressure in the line to a constant constant pressure between the relief valve and the injection nozzle.

In order to obtain such an unchanging steady-state pressure upstream of the injection nozzle during injection pauses, the opening force must be the same in all mass-produced valves, and the said steady-state pressure obtained by the relief also remains constant after a long period of operation. But it must remain unchanged. This is because the injection nozzle opening pressure and the steady-state pressure must be matched very precisely for a particularly accurate injection start. Such fluctuations in the relief pressure can occur, for example, due to changes in the spring force, e.g. because the movable valve member plunges into the valve seat after a long operation and thereby lengthens the spring travel, or due to manufacturing errors that occur during machining. This is caused by an error in the spacing between the spring support and the movable valve cuticle during manufacturing due to tool wear, etc. Even small stroke errors can result in significant valve opening or closing pressure differences and therefore different steady-state pressures for the same spring. Since double-cylinder internal combustion engines are almost always used, different steady-state pressures occur in the respective pressure lines in the engine. The variation in the injection timing results in different combustion characteristics with unnecessarily high fuel consumption and unnecessarily high pollutants of the exhaust gas. Therefore, isobaric relief valves are extremely important for the injection characteristics.

In the case of the known isobaric relief valve of the above type (EP-OS No. 0
143296), in order to reverse the flow of fuel for pressure compensation, the relief valve member is appropriately applied to the force of the coil spring after injection by the fuel present between the isobaric relief valve and the injection nozzle during pressure relief. It is resisted and released. In this case, the valve seat part of the relief valve is made of a hard material in order to avoid undesirable wear during operation and to avoid a change in the effective stroke length of the helical spring due thereto. The valve member body is also usually
Constructed from a hard material to allow long-term use for a rigid pressure valve body. In order to be able to fix the valve seat part on the valve member body by radial deformation of the casing sleeve, the casing sleeve is designed to be flexible in its end region. This requires additional working steps, e.g. full annealing. In this case,
This creates the risk of additional manufacturing errors.

In case of another known isobaric relief valve (DE-O3 No. 3807
572) The casing sleeve is formed in one piece with the valve seat member of the relief valve, and the end section of the casing sleeve facing the hardened valve member body is fixed to this end section by radial deformation. . In this case, the same problem arises as in the case of the isobaric relief valve mentioned at the outset, namely that the radially deformable section of the housing sleeve has to be made of soft material, and thus the above-mentioned additional The problem arises that a detailed work process is required.

In an embodiment of the invention, the housing sleeve is likewise fixed to the valve member body by radial deformation on the side facing the valve member body, in which case the valve member body and the valve seat member are made of a hard material. In contrast, the casing sleeve is made of a deformable, soft material.

Advantages of the Invention The advantage of the isobaric relief valve according to the invention is that the production of such an isobaric relief valve is significantly simplified and at the same time quality assurance or quality improvement is achieved during manufacturing.

In an advantageous embodiment of the invention, a step is provided in the valve member body as an axial stop for the housing sleeve, and a shoulder is provided in the housing sleeve as an axial stop for the valve seat member. According to the invention, therefore, when the valve is assembled with the relief valve member and the helical spring, the casing sleeve is embossed into a suitable undercut of the valve member body and at the other end of the casing sleeve. After bending the part over the end of the valve seat part, a positive-fit connection between the valve member body and the valve seat part is created.

As is well known, due to only slight variations during manufacturing and hardening, the coil springs have different forces for the same stroke, and therefore, according to the invention, in order to precisely adjust the opening force of the relief valve, the coil springs can be preselected. Washers of different thicknesses can be inserted between the coil spring and the support surface of the coil spring. This also makes it possible to correct small error differences or spring force differences.

This is because the individual spring lengths as well as the spring forces and other production dimensions can be measured very precisely. In this case, the components produced by a selection/selection method known per se can be arranged with respect to each other and selected in such a way that extremely precise opening and closing forces of the individual isobaric relief valves are obtained. .

According to another advantageous refinement of the invention, the travel of the relief valve element can be defined by a stop pin arranged inside the helical spring, said stop pin being on the side opposite the relief valve element. is supported on the bottom surface of the blind hole of the valve member body which receives the valve member on one side. Due to the stroke limitations of the relief valve element, the relief valve element is opened only as far as is absolutely necessary, ie by the same stroke in each injection cycle. As a result, a steady pressure is maintained almost constant with rotational speed. In this case, the helical spring is also advantageously displaced by the predetermined distance, so that the same closing force always occurs. Furthermore, the maximum open cross section defined by the stroke limit acts as a throttle, so that the relief valve acts as a regulating valve, which reduces the amount of fuel as the rotational speed increases and the conveying time correspondingly decreases. It has the function of causing only a part of the flow to flow backwards, and also has the effect of changing the injection start point, that is, advancing the injection start as the rotational speed increases.

In the case of known isobaric relief valves that work without such a stroke, the opening stroke of the relief valve member changes depending on the amount of backflow, so the closing force can also be varied depending on the spring characteristics, which makes it easier to operate. Slight differences will occur. Although this difference is slight, it can lead to disadvantageous effects, particularly in relation to speed and load.

In a further embodiment of the invention, the stop pin is designed in a stepped manner, and the shoulder formed thereby serves as a stop surface for the coil spring. In this way, the pin is firmly pressed against the bottom surface of the valve member body with which it cooperates.

In a further development of the invention, discs of different thickness can be inserted between the bottom surface in the valve seat body and the stop pin for stroke adjustment. As is well known, when manufacturing coil springs and turned parts, dimensional errors occur in the travel direction due to spring installation and tool wear, which must be compensated for.
Length errors of the individual components, which were previously measured before constructing such a pressure valve, are suitably compensated for by said discs of different thicknesses. Manufacture is suitably simplified by the inventive design of the component arranged between the valve seat member and the valve member body of the relief valve and of the sleeve cooperating with this component. By inserting the washer, no additional machining of the stop pin is therefore necessary, and the opening force as well as the opening stroke can be adjusted independently of each other.

Advantageous developments of the invention are specified in the further claims.

The exemplary pressure valve member I cooperates with the pressure valve body 2, in which case a high-pressure flow occurs in the direction of the arrow I, whereas a relief flow occurs in the direction of the arrow H. The pressure valve member l is loaded in the closing direction by a pressure valve spring 3. For this purpose, the pressure valve spring acts on the shoulder 4 of the pressure valve member 1.

The pressure valve member I has a valve member body 5 on which a step 8 is arranged as an axial stop for the housing sleeve 6. A stopper pin 7 formed in a step shape is inserted into the inside of the casing sleeve 6.
This results in a stop surface 10 for the coil spring 9 of the relief valve.
The shoulders are formed. At its other end, the coil spring 9 acts on a movable relief valve element 11 whose travel (2) is limited by the stopper pin 7. The valve seat of the relief valve is arranged in a valve seat member 12 which is fixed to the casing sleeve 6.

The relief flow (1) passes through the hole 13 in the valve seat member 2 and through the relief valve member 11 into the interior of the casing sleeve 6 and from there through the hole 14 extending in the stopper pin 7 into the center of the valve member body 5. It flows into the hole 15.

The casing sleeve 6 contacts the step 8 and the enlarged section 16
is pushed through the valve member body 5 and embossed in the valve member body into an annular groove 17 for fixing thereto.

The housing sleeve 6 is made of a soft and therefore easily embossable material. This is because the housing sleeve 6 is not exposed to direct mechanical loads. The valve seat member 12 of the relief valve also has a casing sleeve 6.
The clamping is fixed by the deformation, in which case the free end 18 of the housing sleeve 6 holds the valve seat part 12 with its upper edge and is beveled for this purpose. In order to provide a suitable support for the valve seat part, the housing sleeve 6 is enlarged in this area, in which case a shoulder 19 is formed which serves as a support.

Washers 21 of different thicknesses can be inserted between the coil spring 9 and the bearing surface of the stop pin 7 in order to achieve the desired adjustment. This defines the opening pressure of the relief valve. Furthermore, in this case, the opening stroke (2) is defined by a washer 22, which is placed between the lower end face of the stopper bin 7 and the bottom face 23 facing this, that is, between the bottom face 23 of the blind hole 24 of the valve member body 5. It can be inserted between. The diameter of the bottom corresponds approximately to the maximum diameter of the stopper pin 7.

When producing the pressure valve element, the valve seat element 12 is immovably fixed in the housing sleeve 6 by edge bending. The relief valve member 11 and the coil spring 9 are then inserted into the casing sleeve 6. In this case, a washer is inserted into the blind hole 24 in accordance with the desired opening stroke (1), on which the stopper pin 7 is then placed and the washer 2 is then placed on the stopper pin in accordance with the desired opening pressure.
1 is covered. To produce the pressure valve member, the housing sleeve 6 is then pushed onto the valve member body by means of the enlarged section 16 and fixed by embossing in the annular groove 17 of the valve member body 5 with the enlarged section 16.

In this case, a fixed contact at step 8 is provided for the desired seal.

Instead of embossing in the circumferential area, the end of the housing sleeve can also be embossed in the groove, in which case the clamping is preferably performed in order to obtain an advantageous state of fastening or sealing force. After embossing, the annular groove surface partially covered by the sleeve extends obliquely inward.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view of an isobaric relief valve according to the invention. ■...Pressure valve member, 2...Pressure valve body, 3...Pressure valve spring, 4.19...Shoulder, 5...Valve member body, 6...
・Casing sleeve, 7...Stock six pin, 8...
・Stepped portion 9...Coil spring, 10...Support surface, 11.
...Relief valve member, 12...Valve seat member, 13.14.1
5... Hole, 16... Enlarged section, 17... Annular groove,
18...Free end, 21.22...Washer, 23...
・Bottom surface, 24...blind hole, ■...stroke

Claims (7)

[Claims] 1. An isobaric relief valve for installation between an injection nozzle and an injection pump pressure chamber in a fuel pressure passage of an injection device for an internal combustion engine, the valve being opened in the conveying direction against the force of a pressure valve spring and comprising a valve member. a pressure valve member cooperating with a pressure valve seat of the pressure valve body by a body, a relief passage extending within the pressure valve member connecting the fuel pressure passage downstream and upstream of the pressure valve seat, and controlling the relief passage; a coil spring acting on the relief valve element on the one hand and supported on a support surface facing the relief valve element on the other hand, which opens against the conveying direction and together defines the opening pressure of the relief valve with the relief valve element; a valve seat member supporting a valve seat of the relief valve member; and a casing sleeve disposed on the valve member body of the pressure valve member, the free end of the casing sleeve securing the valve seat member to the valve member body. In the version in which the casing sleeve (6) is radially deformed in order to characterized in that the body (5) and the valve seat part (12) are made of hard material, whereas the casing sleeve (6) is made of a deformable soft material,
Equal pressure relief valve for fuel injectors. 2. A step (8) is provided on the valve member body (5) as an axial stop for the casing sleeve (6) and a shoulder (19) is provided in the casing sleeve (6) as an axial stop for the valve seat member (12). 2. The isobaric relief valve of claim 1. 3. The casing sleeve (6) is attached to the valve member body (5) or the valve seat member (12) by bevelling or by embossing into a suitable groove (17) through a suitable edge of the valve member body (5) or valve seat member (12). Or valve seat part (12)
3. An isobaric relief valve according to claim 1 or 2, wherein the isobaric relief valve is coupled to. 4. The opening force of the relief valve is defined by a washer (21), which is connected to the helical spring (9) and the associated support surface (10).
4. The isobaric relief valve according to claim 1, wherein the isobaric relief valve is insertable between one of the following. 5. The stroke (III) of the relief valve member (11) is defined by a stopper pin (7) arranged inside the coil spring (9), and this stopper pin
) on the bottom surface (23) of the blind hole (24) of the valve member body (5) receiving the stopper pin on one side. Pressure relief valve. 6. 6. The isobaric relief valve according to claim 5, wherein the stop pin (7) is configured in a stepped manner, and the shoulder formed thereby serves as a support surface (10) for supporting the helical spring (9). 7. In order to define the opening stroke (III) of the relief valve, disks (22) of different thicknesses are inserted between the stopper pin (7) and the bottom surface (23) in the valve member body (5) facing this stopper pin. 7. Isobaric relief valve according to claim 1, which is possible.