EP2205855A1

EP2205855A1 - Compact injection device

Info

Publication number: EP2205855A1
Application number: EP08804690A
Authority: EP
Inventors: Joerg Heyse
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-10-23
Filing date: 2008-09-24
Publication date: 2010-07-14
Anticipated expiration: 2028-09-24
Also published as: EP2205855B1; DE102007050547A1; ATE513124T1; WO2009053201A1; CN101835971A

Abstract

The present invention relates to an injection device, comprising a fuel pump (20a), a pressure regulator (20b), an injector (20c), and an air actuator (20d), characterized in that the fuel pump (20a), the pressure reducer (20b), the injector (20c), and the air actuator (2Od) are integral parts of an injection module (2) and the injection device further comprises a suction jet pump (40), via which fuel is fed, wherein the suction jet pump (40) is connected to a tank (6) and the fuel pump (20a).

Description

description

title

Compact injector

State of the art

The present invention relates to an injection device with a fuel pump, a pressure regulator, an injector, an aerator and a suction jet pump in a compact design.

Injectors are known in the prior art in various configurations. Especially for cost and space reasons require small internal combustion engines, which have only one or only two cylinders and a small displacement, independent solutions. Areas of use of such small internal combustion engines are, for example, two-wheelers, tricycles or lawnmowers, etc. Known injection devices usually comprise in a tank a high-pressure pump with a pressure regulator, wherein the high-pressure pump injects fuel at a predetermined pressure into a duct, e.g. a rail o.a., promotes. At the end of the line an injector is arranged, which injects controlled by a control device fuel into a suction pipe or directly into a combustion chamber. However, such injectors are very expensive and especially expensive, so that they also make small internal combustion engines very expensive.

From EP 1 340 906 B1 a fuel injection device with electronic control is known in which an injector is arranged close to a pump piston. Further, in this case, a pre-pressure valve is provided for exerting an admission pressure on the fuel in an initial phase of a pressure stroke of the piston in the return line of the fuel to the tank. The admission valve evacuates a part of the fuel located in a pressure chamber in the return line. In this way, in particular the formation of vapor bubbles in the injector can be reduced. However, the structure is relatively complicated and the device takes up a large amount of space.

Alternatively, it is also possible to use a suction jet pump for filling a pot, which is connected upstream of a fuel pump. Here, the fuel by means of

Suction jet pump from the tank into the pot. The suction jet pump is driven by a outgoing from the pressure side of the fuel pump return flow. Here is the Liquid level in the pot raised to a liquid level in the tank, so that when sucking the fuel from the pot, there is a higher inlet pressure in the intake pipe. This reduces the risk of vapor bubble formation in the supply line to the fuel pump. However, this solution is also very expensive and expensive.

Therefore, the known solutions to avoid vapor bubbles due to their manufacturing costs are not suitable for use in low-cost small vehicles.

Advantages of the invention

The injection device according to the invention with the features of claim 1 has the advantage that it has a very compact structure. Furthermore, the injection device according to the invention can be produced in a particularly simple and cost-effective manner and the formation of vapor bubbles in the fuel supply line can be avoided. As a result, the injection device according to the invention can be used in particular in small internal combustion engines, e.g. at

Two-wheeled or lawn mowers or similar, are used. This is inventively achieved in that the injection device comprises a fuel pump, a pressure regulator for controlling an injection pressure, an injector, an aerator and a suction jet pump, consisting of a motive nozzle and a diffuser. The fuel pump, the pressure regulator, the injector and the air actuator are an integral part of an injection module. The injection module is very compact and physically small and can be completely pre-assembled. As a result, the suction jet pump only has to be connected to the corresponding connection of the injection module. The four integral components of the injection module are preferably arranged in a common housing of the injection module. The suction jet pump ensures that in the injection module, the formation of vapor bubbles is prevented, so that damage to the injection module and the metering of incorrect amounts of fuel can be avoided. Thus, the injection device according to the invention has a compact injection module and in addition an ejector pump, so that a trouble-free operation of the fuel-conveying components is ensured and the formation of vapor bubbles can be avoided.

The dependent claims show preferred developments of the invention.

Particularly preferably, the suction jet pump is also an integral part of the injection module. Thus, the compact injection module comprises five components, namely the fuel pump, the pressure regulator, the injector, the aerator and the ejector. As a result, a space requirement for the injection module can be minimized and the complete injection module can be mounted in advance. The suction jet pump can be particularly easily integrated be that the diffuser and the motive nozzle are arranged completely in the housing of the injector.

Preferably, the injection device comprises exactly one actuator, which simultaneously actuates the fuel pump and the aerator. As a result, in particular a separate actuator for the aerator or the fuel pump can be dispensed with, so that the number of components is significantly reduced. Of course, this also results in a cost reduction. Thus, the only actuator of the injector assumes the function of the pump drive and, secondly, the function of the actuator for the air actuator.

The only actuator of the injection device is preferably a magnetic actuator with exactly one coil and exactly one armature. This allows a particularly simple and inexpensive construction can be realized.

Preferably, the tank is disposed in the vehicle at a higher position than the suction jet pump. As a result, a higher pressure level in the suction jet pump can also be realized.

According to a further preferred embodiment of the present invention, the injection device comprises a return line which recirculates pressurized fuel from a pressure space to the ejector pump, more precisely to the motive nozzle. The pressure chamber may be a pumping chamber of the piston pump or a pre-pressure chamber.

Particularly preferably, the fuel pump comprises an antechamber, which is arranged after the suction jet pump. In the pre-chamber, the fuel is pressurizable to a predetermined value.

Particularly preferably, a check valve is arranged between the admission pressure chamber and the suction jet pump. The check valve opens only when a predetermined opening pressure is reached by the suction jet pump. Furthermore, the check valve ensures that fuel can not flow from the admission pressure chamber back into the suction jet pump.

According to a further preferred embodiment of the present invention, the fuel pump comprises a piston, which is designed as a stepped piston with a first piston surface and a second piston surface. The first piston area is larger than the second

Piston area. As a result, the stepped piston can generate different pressures in two different chambers. - A -

Preferably, the first piston surface is arranged in the pre-chamber and the second piston surface is arranged in the pumping chamber.

According to a further preferred embodiment of the present invention, a through hole is arranged in the piston of the fuel pump, which connects the front pressure chamber with the pumping chamber. In the through hole while a check valve is arranged, which prevents backflow of the fuel from the pumping chamber into the admission pressure chamber. This configuration of the piston, in particular, the number of parts of the fuel pump can be significantly reduced because no separate line or no additional housing for a check valve is necessary because everything is integrated in the piston.

According to another preferred embodiment of the present invention, the fuel pump comprises a first piston member, a second piston member and a diaphragm. The membrane is arranged in the direction of movement of the piston elements between the first and second piston element. The two piston elements are arranged on a common axis. Furthermore, the membrane forms a wall region of the admission pressure chamber. This allows a simple structure.

In order to realize the most cost-effective manufacturability of the suction jet pump, the suction jet pump is preferably made of a plastic material. As a result, the suction jet pump can be produced for example by means of injection molding and also simultaneously with other components of the injection device, e.g. the housing by injection molding, are produced.

According to a further preferred embodiment of the present invention, a compressible pressure buffer device, for example a bubble filled with gas, is arranged in the admission pressure chamber. By the pressure buffer medium in the pressure buffer device, a pressure increase can be held in the pre-pressure chamber. As a pressure buffer medium, for example, a compressible medium disposed in the bubble, e.g. Air, serve.

drawing

Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is: Figure 1 is a schematic view of a small motor with an injection device according to a first embodiment of the invention, Figure 2 is a schematic sectional view of an injection module with a Saugstrahlpumpe according to the first embodiment, and Figure 3 is a schematic sectional view of an injection module with a suction jet pump according to a second embodiment of the invention.

Preferred embodiments of the invention

Hereinafter, a small motor 1 with an injection device according to the invention according to a first embodiment will be described in detail with reference to Figures 1 and 2.

Figure 1 shows schematically the structure of the small motor 1, which is designed as a single-cylinder engine. The small engine 1 comprises a cylinder 3, a reciprocating piston 4, a control unit 5 and a tank 6. The tank 6 is connected to an injection module 2 via a fuel supply line 6a. At the end of the fuel supply line, a suction jet pump 40 is arranged directly on the injection module 2. A return line 32 goes from the injection module 2 back to the suction jet pump 40. As can be seen schematically from FIG. 1, the tank 6 is arranged above the injection module 2. As a result, the fuel passes through the fuel supply line 6a due to gravity to the injection module 2, so that thereby already a slight increase in pressure takes place at the suction jet pump. The injection module 2 is shown very schematically and comprises a fuel pump, a pressure regulator, an injector and an air actuator, so that the injection module 2 is constructed very compact.

The small engine 1 further comprises a throttle valve 7, which is arranged in a suction pipe 8. On the cylinder 3, a spark plug 9, an intake valve 10 and an exhaust valve 11 is further arranged. The reference numeral 12 designates a bypass line for air, which branches off from the intake manifold 8 air from a region in the flow direction of the air in front of the throttle valve 7 and leads directly to the integrated into the injection module 2 aerator. An outlet of the bypass line 12 lies directly adjacent to the injector of the injection module. 2

The small engine 1 further comprises an exhaust pipe 13, which is released or closed by the exhaust valve 11. Further, an oxygen sensor 14 is provided on the exhaust pipe 13 which is connected to the control unit 5 and the control unit 5 is further provided with a

Cooling water sensor 15, an oil temperature sensor 16 and a sensor unit 17 for the detection a throttle position, a temperature in the intake manifold 8 and a pressure in the intake manifold 8. The control unit 5 controls the injection device 2 on the basis of the received signals.

The injector according to the invention thus comprises, as shown in Figure 2, an injection module 2 with a fuel pump 20a, a pressure regulator 20b, an injector 20c and an aerator 2Od, which are arranged in a common housing 25, and can be designed to be particularly compact and physically small. Furthermore, the injection device according to the invention can be produced very inexpensively and in particular be pre-assembled in advance as a complete injection module 2, so that it only needs to be installed in the small engine 1 as a compact assembly. By integrating the four parts

Fuel pump, pressure regulator, injector and air actuator is thus a simple and inexpensive manufacturability guaranteed. The fuel pump and the air actuator are actuated by a common actuator. In addition, a suction jet pump 40 is provided. As a result, the injection device 2 according to the invention can be used, for example, in small motors for two-wheelers or lawn mowers.

As shown in FIG. 2, the injection module comprises a coil 21 and an armature 22 cooperating with the coil 21. As can be seen in FIG. 2, the armature 22 is fixedly connected to a first piston part 23 and a second piston part 24. As a result, in a movement 22, the two piston parts 23, 24 are moved together. The first piston part 23 is assigned to the air actuator 2Od and releases a cross section of the bypass line 12 at a seat 12a or closes the bypass line 12.

As can be seen further from FIG. 2, the injection module 2 comprises a housing 25, which is manufactured from a plurality of individual parts 25a, 25b, 25c, 25d. For cost-effective production, the individual parts of the housing take on different functions. For example, the seat 12a is formed on the item 25 of the housing. Furthermore, the injection module comprises a first admission pressure chamber 26, a second admission pressure chamber 27 and a pumping chamber 28. The first admission pressure chamber 26 and the pumping chamber 28 are in contact with the second piston part 24. The second piston part 24 forms a part of the fuel pump 20a. As can be seen from FIG. 2, the second piston part 24 is designed as a stepped piston and has a first piston surface 24a and a second piston surface 24b. The first piston surface 24a is in contact with the fuel in the first admission pressure chamber 26 and the second piston surface is in contact with the fuel in the pumping chamber 28. The second piston part 24 is guided by guide areas, which are formed on the housing parts 25 c and 25 d. The first admission pressure chamber 26 is connected via a line 30 to the second admission pressure chamber 27, wherein a first check valve 29 is arranged in the line. Furthermore, the second admission pressure chamber 27 is connected to the pumping chamber 28 via a second check valve 31. In a known manner, fuel can then be injected into the suction pipe 8 from the pumping chamber 28 via a check valve of the injector 20c.

The second pre-return chamber 27 is further connected via a line 32 to the suction jet pump 40. In this case, the pressure regulator 20b is arranged in the line 32. The pressure regulator 20b of this embodiment includes a throttle 35. Alternatively, instead of the throttle and a check valve may be provided. The suction jet pump 40 is arranged in the supply line 6a from the tank 6. As can be seen from FIG. 2, the suction jet pump 40 comprises only one motive nozzle 41 and one diffuser 42. As a result, the ejector pump 40 can be provided very simply and cost-effectively, for example as a plastic injection-molded part. In this case, the suction jet pump 40 is arranged in a curved line section 6a ', so that the fuel emerging from the motive nozzle 41 exits the tank 6 parallel to the flow direction of the fuel. As further seen in Figure 2, the end of the diffuser 42 is connected to the first pre-pressure chamber 26, wherein between the first pre-pressure chamber 26 and the diffuser 42 is still a third check valve 43 is arranged. The suction jet pump 40 is arranged directly on the housing.

The second piston part 24 is reset by means of a return spring 34, which is supported on a chamber wall 33 of the first admission pressure chamber 32 and presses against the first piston surface 24a. Further, reference numeral 36 denotes an air-filled cavity. It should be noted that the cavity 36 need not necessarily be provided, but it is also possible that, for example, the return element for the second piston member 24 may be disposed in the cavity, so that the return element is not located in the fuel.

The function of the injection device according to the invention according to the first embodiment is as follows. When fuel is to be injected into the suction pipe 8, the coil 21 is energized, so that the armature 22 moves in the direction of the arrow A. Since the armature 22 is fixedly connected to the first piston part 23 and the second piston part 24, the two move

Piston parts simultaneously with the armature 22 in the direction of arrow A. This opens the air actuator 2Od. At the same time, an increase in pressure takes place in the first admission pressure chamber 26, since the first piston surface 24a is moved further into the first admission pressure chamber 26. Due to this increase in pressure, the first check valve 29 opens so that pressurized fuel flows into the second admission pressure chamber 27. Furthermore, the fuel located in the pumping chamber 28 is pressurized via the second piston surface 24b, with the injector 20c automatically opening from a predetermined pressure level and injecting fuel into the intake manifold 8. There Further, the second pre-pressure chamber 27 is connected via the line 32 to the suction jet pump 40, fuel is at a predetermined pressure to the suction jet pump 40 at.

After completion of the injection, the energization of the coil 21 is released again and the armature 22 by means of the return spring 34 which resets the second piston member 24, also returned to its original position. Of course, this also applies to the first piston part 23 fixedly connected to the armature 22, so that the air actuator 2Od is also closed. The provision of the second piston member 24 simultaneously causes a suction of new fuel. On the one hand, fuel is sucked from the second admission pressure chamber 27 via the second check valve 31 into the pumping chamber 28 and on the other hand, fuel is released by opening the third

Check valve 43 sucked from the tank 6. In order to avoid vapor bubbles in this suction, the suction jet pump 40 is provided. The suction jet pump 40 provides the drive of the suction jet pump via the drive nozzle 41. The propulsion jet from the motive nozzle 41 serves as the drive. To this end, an additional volume flow via the motive nozzle 41 still arrives at the volume flow of the fuel coming from the tank. The motive nozzle 41 is thereby submerged

Pressure fuel supplied from the second pre-pressure chamber 27 via line 32. The fuel from the motive nozzle leaves it at a higher speed and due to internal friction results in a turbulent flow, which enters the diffuser 42. In the diffuser there is a steady pressure increase, so that it can be avoided that vapor bubbles can arise in the fuel. At a certain pressure level, the third check valve 43 opens, so that the fuel can be supplied to the first admission pressure chamber 26. As can be seen from FIG. 4, the end of the diffuser is arranged directly on the housing 25. It should be noted that in principle it is also possible for the suction jet pump 40 to be arranged completely in the injection module 2. This allows an even more compact design can be realized. It should also be noted that the drive nozzle 41, the diffuser 42 and the 90 ° curved line section 6a 'can be made of a plastic material in one step, for example by plastic injection molding. As a result, the suction jet pump 40 can be provided in a particularly cost-effective manner.

Thus, in addition to the usable flow rate for injection, the injection valve additionally has to circulate the volume flow necessary for driving the suction jet pump 40 via the line 32. The pressure energy transferred to this additional volume flow is then used to raise the pressure in the intake area above the tank pressure so that the formation of vapor bubbles in the intake area can be avoided with certainty. For further pressure increase, the tank 6 is additionally arranged slightly above the injection module 2, so that this also results in a certain pressure increase in the intake area. A particularly high pressure in the first admission pressure chamber 26 is achieved if a ratio of the injected volume flow to the intake volume flow (circulated volume flow plus injected volume flow) is relatively small. That is, the recirculated volume flow is much larger than the injected volume flow. Alternatively, a diameter in the driving nozzle 41 can be selected to be relatively small in order to achieve a high pressure in the first admission pressure chamber.

Hereinafter, with reference to Figure 3, an injection device with a

Injection module 2 according to a second embodiment described in detail. Identical or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

In contrast to the first embodiment, the injection module of the second embodiment is even more compact. In particular, can be dispensed with in the second embodiment, a second pre-pressure chamber and a separate line. As shown in FIG. 3, the fuel pump 20 a of the second embodiment comprises a diaphragm 50 and a piston 51 exposed in a cylinder. In the exposed piston 51, there is provided a through hole 52 having a pilot pressure chamber 26

Pumping chamber 28 connects. In the through hole 52, a first check valve 29 is arranged. The membrane 50 is firmly fixed to the housing 25 of the injection module and forms a chamber wall of the pre-chamber 26. Further, the fuel pump 20a of the second embodiment comprises a plunger 53 which is fixedly connected to the armature 22. The plunger 23 and a piston part 23 of the Luftstellers 2Od are firmly connected to the armature 22 and therefore move together. To return the armature 22, a return spring 54 is also provided.

The function of the injection module 2 according to the second embodiment is as follows. If an injection of fuel to be made, the coil 21 is energized, so that the armature 22 moves together with the plunger 53 and the piston member 23 in the direction of arrow A. As a result, the plunger 53 comes into contact with the diaphragm 50, which is pressed into the admission pressure chamber 26. This results in an increase in pressure in the pre-pressure chamber 26, wherein an upper limit of the pressure is defined by the first check valve 29. When the diaphragm 50 has traveled a small distance in the direction of the arrow A, it comes into contact with a contact region 51a on the exposed piston 51, so that the membrane is moved together with the exposed piston 51. As a result, the piston 51 is moved against the spring force of the return spring 34, and the pressure in the pumping chamber 28 increases. As soon as a predetermined pressure level is reached, the injector 20 c opens, so that fuel can be injected into the suction pipe 8, as indicated by the arrow B. As in the first embodiment, a part of the volume flow is not injected into the suction tube, but guided via the line 23 to the suction jet pump 40. The suction jet pump 40 functions as in the first embodiment, so that by the pressure return and the suction jet pump formation steam bubbles in the intake of the fuel pump is avoided. The second embodiment thus has a reduced number of parts and can be provided very compact and small-sized. This makes it particularly suitable for small machines.

For all described embodiments, it should be noted that a common actuator simultaneously actuates both the fuel pump 20a and the aerator 2Od. Thus, in particular, only one electrical connection for the actuator must be provided, which according to the invention always simultaneously actuates the air actuator 2Od and the fuel pump 20a. As a result, an additional air supply via the bypass line 12 is always achieved simultaneously with the fuel injection, so that a better mixing of the fuel in the supplied air is achieved in the mixture preparation in the intake manifold 8. Further, the provision of the suction jet pump 40 surely allows the occurrence of vapor bubbles in the suction region of the fuel pump in operation.

Claims

claims

An injection apparatus comprising a fuel pump (20a), a pressure regulator (20b), an injector (20c) and an aerator (20d), characterized in that the fuel pump (20a), the pressure regulator (20b), the injector (20c) and the aerator (20d) are an integral part of an injection module (2) and the injector further comprises an ejector (40) through which fuel is supplied, the ejector (40) being connected to a tank (6) and the fuel pump (20a) is.

2. Injection device according to claim 1, characterized in that the suction jet pump (40) is an integral part of the injection module (2).

3. Injection device according to one of the preceding claims, comprising exactly one actuator (21, 22) which simultaneously actuates the fuel pump (20a) and the air actuator (2Od).

4. Injection device according to one of the preceding claims, characterized in that a tank (6) via the suction jet pump (40) is arranged.

5. Injection device according to one of the preceding claims, characterized in that a return line (32) leads fuel from a pressure range of the fuel pump (20a) to the suction jet pump (40).

6. Injection device according to claim 5, characterized in that in the return line (32) a throttle (35) or a check valve is arranged.

7. Injection device according to one of the preceding claims, characterized in that in the flow direction after the suction jet pump (40) a Vordruckkamer (26) is arranged, in which the fuel is temporarily stored on a predetermined form.

8. Injection device according to claim 7, characterized in that between the suction jet pump (40) and the pre-pressure chamber (26) a check valve (43) is arranged.

9. Injection device according to one of the preceding claims, characterized in that a piston (24) of the fuel pump (20a) as a stepped piston with a first piston surface (24a) and a second piston surface (24b) is formed, wherein the first piston surface (24a) larger as the second piston surface (24b).

10. Injection device according to spoke 9, characterized in that the first piston surface (24a) in the predracking chamber (26) is arranged and the second piston surface (24b) in a pumping chamber (28) is arranged.

11. Injection device according to one of claims 7 to 10, characterized in that in the piston (51) of the fuel pump (20 a) a through-bore (52) is arranged, which connects the pre-racking chamber (26) with the pumping chamber (28), wherein in the Through hole (52) a check valve (39) is arranged.

12. Injection device according to one of the preceding claims 7 to 11, characterized in that the fuel pump (20 a) comprises a membrane (50) and a first piston (53) and a second piston (51), wherein the membrane (50) between the first and second pistons is arranged and forms a wall portion of the pre-racking chamber (26).

13. Injection device according to one of the preceding claims, characterized in that the suction jet pump (40) is made of plastic.

14. Injection device according to one of the preceding claims, characterized in that in the predracking chamber (26) of the fuel pump (20a) is arranged a compressible Drackpuffereinrichtung, in particular a gas-filled bladder.

15. Internal combustion engine comprising exactly one or exactly two cylinders and an injection device according to one of the preceding claims.