WO2012089511A1

WO2012089511A1 - Pressure control arrangement of a fuel injection system having a valve which is arranged on the pressure side of a pump

Info

Publication number: WO2012089511A1
Application number: PCT/EP2011/072829
Authority: WO
Inventors: Siamend Flo; Frank Nitsche; Alexander Schenck Zu Schweinsberg; Thorsten Allgeier; Juergen Arnold; Peter Schenk; Michael Bauer
Original assignee: Robert Bosch Gmbh
Priority date: 2010-12-27
Filing date: 2011-12-14
Publication date: 2012-07-05
Also published as: EP2659125A1; EP2659125B1; CN103270289B; DE102010064219A1; CN103270289A

Abstract

In a pressure control arrangement of a fuel injection system which is operated by way of a pump (12, 100) for an internal combustion engine (32), having a valve (76) which is arranged on the pressure side of the pump (12, 100) for discharging fuel under pressure from the pressure side of the pump (12, 100) to the suction side of the pump (12, 100), a variable restrictor (78) with a modifiable restrictor action is provided on the suction side of the pump (12, 100), in order to restrict the fuel quantity which is fed to the pump (12, 100).

Description

description

title

Pressure control arrangement of a fuel injection system with a valve arranged on the pressure side of a pump

State of the art

The invention relates to a pressure regulating arrangement of a pump-operated fuel injection system for an internal combustion engine, with a valve arranged on the pressure side of the pump for discharging fuel under pressure from the pressure side of the pump to the suction side of the pump. Furthermore, the invention relates to a fuel injection system with such a pressure regulating arrangement.

Today's fuel injection systems of internal combustion engines or internal combustion engines, especially in gasoline engines, work as so-called direct injection with injection pressures of up to 200 bar. The pressure is generated by means of a pump, a so-called high-pressure pump, which is mechanically driven by the internal combustion engine or engine in known fuel injection systems. An electromechanical, in particular electromagnetic, quantity control valve controls the quantity of fuel delivered by the pump per unit of time into a high-pressure region, a so-called rail. Together with a high pressure signal measured by a high-pressure sensor, an engine control unit thus regulates the pressure in the high-pressure range to the desired level by means of the quantity control valve. The control of injection valves on the internal combustion engine takes place on the basis of the measured pressure signal.

Disclosure of the invention

According to the invention, there is provided a pressure regulating arrangement of a fuel injection system operated by a pump for an internal combustion engine, having a valve for discharging fuel arranged on the pressure side of the pump under pressure from the pressure side or high pressure side of the pump to the suction side or low pressure side of the pump. On the suction side of the pump, a variable throttle is provided with a variable throttle effect, which serves to throttle the amount of fuel supplied to the pump.

According to the invention, a purely self-sufficient pressure regulation is created on the pump of a fuel injection system via purely mechanical components. On the other hand, electrical, electrohydraulic or electronic components can be dispensed with. The invention combines two pressure control methods, namely the method of pressure control by means of the valve from the pressure range to the suction region of the pump and the method of suction throttling the pump. The suction throttling is preferably carried out by means of a proportional valve, which opens and closes in proportion to the applied pressure.

The advantages of the solution according to the invention are particularly low system costs, in particular due to the elimination of otherwise required electromagnetic components. Thus, particularly preferred is no electromechanical quantity control valve, as is the case with known fuel injection systems. Furthermore, the energy requirement for the fuel injection according to the invention and thus the fuel consumption of the entire system due to the lack of electrical components is lower.

The valve is advantageously functionally coupled to the variable throttle. With the functional coupling of the valve with the variable throttle, not only the pressure regulation but also the suction throttling of the pump takes place as a function of the pressure from the high-pressure region. The pressure from the high pressure area thus controls the valve and the variable throttle and their throttle effect.

The functional coupling of valve and variable throttle is preferably realized mechanically. For the mechanical coupling, the pressure or overpressure generated by the pump is advantageously applied to the valve. This means that the valve opens in particular from a certain overpressure. With the opening movement of the valve, the mechanically coupled variable throttle is also adjusted. As a result of the mechanical coupling of the valve and throttle, the pressure thus acts on the variable throttle and adjusts it. The valve is preferably realized as a slide valve. It advantageously captures pressure peaks coming from the high pressure area. The control with the variable throttle is thereby smoothed. Thus, a pressure damper function is integrated in the pressure control arrangement and it can be achieved a better control quality.

The valve, the constant throttle and the variable throttle are preferably combined in an assembly, in particular in the pump itself. Such integration of these sub-functions of the solution according to the invention in only one assembly, preferably in the pump or high-pressure pump, brings a space saving with it. The conduction paths can be kept very short, which improves the dynamics of the system and at the same time saves costs. Furthermore, the weight is also reduced as compared with conventional systems. Finally, the assembly is easier and cheaper.

For a mechanical coupling of the valve with the variable throttle preferably the valve and the variable throttle are realized with a single closure body. Here, the valve and the variable throttle are preferably combined in one unit. The function of the valve and the variable throttle are then integrated into a single hydraulically controlled valve unit, in particular a proportional valve unit. Advantageously, the valve unit is designed as a piston slide valve with two control slots or control slide pairs on an associated cylinder, the function of the valve and the variable throttle being designed here in each case with a control slot.

The closure body is preferably a piston which is resiliently biased against the pressure coming from the direction of the pump or high-pressure pump. The piston is in the cylinder accordingly depending on the height of the

Pressure of the high pressure pump moves. As a result, depending on the position of the piston, the control slots can be opened or closed. In this way, the function is provided as a variable throttle and valve in the smallest space with only a few components. The closure body preferably completely covers either a first control slot or a second control slot on the cylinder. The control slots, which take over the function of the valve and the variable throttle, are arranged offset on the cylinder of the spool valve in the axial direction. 5 The closure body is thus preferably designed such that it can completely close only one of the two control slots, or - depending on the embodiment - at most partially covers both control slots. Thus, due to overpressure on the pressure side of the pump, the closure body is displaced so that the control slot which forms the valve, opens. The opening movement simultaneously closes the control slot which maps the variable throttle. As the overpressure decreases, the piston closes the control slot that forms the valve and at the same time opens the second control slot, which forms the variable throttle. An important aspect of the design according to the invention is advantageous in that the throttle effect of the variable throttle can be varied by the pressure generated by the pump. The change in the throttling effect is preferably carried out in such a way that, as the pressure increases, the control slot forming the variable throttle is further closed. With the thus reduced o passage area at the variable throttle that of the high pressure pump of

Fuel injection system per unit time supplied amount of fuel reduced. The pump can draw less fuel, unnecessary pumping of the high-pressure pump is avoided. The pressure regulating arrangement designed in accordance with the invention can advantageously also be developed to have an accumulator function. For this purpose, preferably, the closure body and the control slots are designed and arranged such that the volume which releases the closure body in its movement from its rest position to reach a control slot, 0 can absorb the amount of fuel at least one cold start injection. Such a design realizes an axial free travel of the closure body in the pressure control valve between a closure body stop in its rest position and the beginning of the control opening for pressure control. While in conventional fuel injection systems, especially at low Raiivolumina, 5 due to the very large in the cold start (eg at - 30 ° C) required injection quantity and increased in the cold E modulus of the fuel, the rail pressure would strongly break, such pressure control arrangement according to the invention prevents too large a pressure drop through the fuel storage function. The storage of the fuel is particularly advantageous in cold start injection and even lower pump speed and makes the system according to the invention independent of electrical power amplifiers for maintaining the system pressure when stopping the engine, especially in start / stop systems. Performs at cold start at low pump speed after the pressure build-up one

Fuel injection, the closure body moves back in the direction of its stop and replaces this amount of fuel, even if the pump has not nachgefördert. The fuel pressure drops only insignificantly, depending on the spring design. After starting the engine and starting the pump, fuel is stored in the pressure control arrangement, which is elastically stored by the spring force and the specially selected low spring rate. The geometries (diameter and stroke of the closure body, spring rate) of the pressure control arrangement are designed so that the storage volume is sufficient to store at least one cold start injection quantity.

The invention is in contrast to known methods for mechanical / hydraulic pressure control. These methods are firstly the so-called (pure) pressure relief via a pressure regulating valve and secondly the so-called (pure) suction throttling.

The pressure relief via a pressure control valve takes place when exceeding a predetermined pressure level. With this concept, the pressure rises in principle with the amount to be eliminated. Due to the coupling of the pump speed and thus the flow rate to the engine speed, therefore, the pressure increases with the speed and falls with increasing load on the engine. Energetically, this concept is in need of improvement, since the delivery rate of the pump is not reduced as needed and therefore higher drive performance (fuel consumption) and higher heat development is expected, especially at high speeds and low engine load (fuel cut). The quality of the control also has a negative effect, especially in the case of pumps with discontinuous rather full delivery in a short time large quantities must be diverted and therefore high-pressure pulsations can be stimulated.

In the suction throttling, the supply to the pump is throttled, the higher the pressure level, so as to prevent further increase of the pressure by further pumping the pump. Since the high-pressure level is used to actuate the Saugdrosselung, relatively large forces occur on the associated variable throttle, which cause high restoring forces in the design of the throttle and therefore also lead to large return means (usually springs). The control quality is due to the existing dead times due to the volumes between the suction throttle and the pump, in principle, less good than the system of a pressure regulator with pressure control valve.

The solution according to the invention makes it possible to design such fuel injection systems more cost-effectively with the same or almost the same function and to avoid the disadvantages mentioned. In particular, with the invention, the function of said pressure control valve and the suction throttling can be combined.

Exemplary embodiments of the solution according to the invention will be explained in more detail below with reference to the attached schematic drawings. It shows:

1 shows a fuel injection system with a pressure control according to the prior art,

2 shows a longitudinal section of a pressure-regulating arrangement according to the invention designed as a structural unit,

Fig. 3 is a longitudinal section of the assembly of FIG. 2 and their positioning in a high-pressure pump

Fig. 4 shows the assembly of FIG. 3 in an enlarged view and

5 is a hydraulic circuit diagram of the assembly according to FIGS. 2 to 4.

In Fig. 1, a fuel injection system 10 is shown with a pump 12. In such fuel injection systems, the region on the suction side of the pump 12 is referred to as the low-pressure region and the region on the pressure-side of the pump 12 as the high-pressure region. In the low-pressure region, fuel is pumped from a tank 14 through an electric fuel pump 16 at a pressure of about 5 bar through a fuel filter 18 to a line 20.

A pressure relief valve 22 may direct fuel from the fuel pump 16 back into the tank 14. On line 16, a low pressure damper 24 is arranged.

In the line 20, the fuel delivery rate of the pump 12 is regulated by a quantity control valve 26. The pump 12 generates a pressure of up to about 200 bar, with which the fuel is conveyed through a Raildrossel 44 in a rail 28. This high pressure defines the already mentioned high-pressure region on the pressure side of the pump 12. From the rail 28, the fuel can be injected via injection valves 30 into an internal combustion engine 32.

In the event of an error or a pressure overshoot in the so-called hot soak a possible overpressure of the pump 12 is derived from the high pressure area in the pump 12. For this purpose, on the pressure side of the pump 12 branches off from the high-pressure region from a return line 34, which leads back into the delivery chamber of the pump 12. A check valve 36 mounted on the pressure side of the pump 12 forms the outlet valve of the pump 12 and prevents fuel from flowing in the opposite direction to its delivery direction. Another, arranged in the return line 34 check valve 38 ensures that only fuel is returned under pressure in the pump 12.

In addition, as mentioned in the low pressure range, the amount of fuel delivered by the pump 12 can be metered by the quantity control valve 26, so that the pump 12 ideally generates the setpoint control pressure. The pumped amount of fuel is regulated by means of a comparatively complex electromechanical system. On rail 28, a high pressure sensor 40 measures the pressure applied there. A controller 42 receives the information regarding the rail pressure from the high pressure sensor 40 and processes it. According to the programming of the control unit 42, the quantity control valve 26 is activated. Thus, the quantity control valve 26 regulates the fuel delivery rate of the pump 12 due to the fuel pressure occurring and measured in the rail 24. In Fig. 2, a structural unit 72 is shown with an embodiment of the invention. The assembly 72 comprises an inner housing 74 on which a control slot 76, a control slot 78 and an inlet bore 80 are formed as a valve. The control slots 76, 78 and the inlet bore 80 are openings in the inner housing 74 which allow fuel flow into or out of the inner housing 74. The shape of the openings of the control slots 76, 78 preferably deviates from a rectangular or circular shape. The shape is preferably substantially triangular with not curved inside legs, whereby the characteristic for the pressure regulating arrangement is favorably influenced.

In the inner housing 74 designed as a piston or spool closure body 84 is slidably mounted. The closure body 84 is urged by a plunger 82 with respect to FIG. 2 to the left. The plunger 82 is formed with an intermediate portion 86 and a main portion 88. In this case, the diameter of the intermediate region 86 acting as a tappet tip or push rod is smaller than that of the closure body 84.

The inner housing 74 is designed stepped and adapted in particular with its inner diameter to the diameter of the closure body 84. In this way, the closure body 84, the control slot 76 and / or the

Close control slot 78 completely or partially in a fluid-tight manner.

Since the two control slots 76, 78 are not located on a common plane, but offset in the axial direction of the inner housing 74, the closure body 84 can close both control slots 76, 78 at the same time. By means of a selection of the spacing of the control slots 76, 78 and the length of the closure body 84, any overlapping or purely serial triggering of the suction throttling with the pressure relief can be achieved. Thus, the control quality can be optimally adjusted.

In order to avoid hysteresis effects by friction of the moving parts, as explained, the closure body 84 and the intermediate region 86 are made in two parts. By a convex, so an outwardly arched execution of the end of the

Intermediate portion 86 toward the closure body 84, the transmission of a Transverse force that would increase the friction between the closure body 84 and the inner housing 74 prevents. By a precise pairing of the closure body 84 and the associated region of the inner housing 74, in which the closure body 84 is guided, the leakage is kept low.

The closure body 84 is biased in the inner housing 74 via the plunger 82 with a spring 90 frontally against an opposite return opening 92. The spring geometry of the spring 90 is dimensioned so that the transverse force minimized to the spring and thus buckling of the spring 90 is prevented. At the return opening 92, a seal 94 is formed in the form of a seat seal.

Further, a flow chamber 96 is formed in the inner housing, which is initially connected to the two control slots 76, 78, and the inlet bore 80. Depending on the respective displacement of the closure body 84 in the inner housing 74, this flow space 96 can be increased or reduced voluminously. In addition, the control slot 76 is connected by a parallel line 98 with the flow space 96 or the parallel line 98 can be considered as part of the flow space 96.

FIG. 2 shows in simplified form a coupling of a pump 100, which may be driven electrically or, as is preferred, mechanically driven. With the pump 100 fuel is passed under high pressure through a pressure line 102 to a rail 104.

Via a branch 106 in the pressure line 102, the fuel also reaches the return opening 92. Since the closure body 84 is biased against the return opening 92, initially no fuel flows into the inner housing 74. However, if the pressure which the pump 100 generates becomes too high , So this generates overpressure, the pressure force is higher than the counter-pressure force of

2, the closure body 84 releases the return opening 92 and fuel can flow into the inner housing 74. The inflowing fuel is stored in the inner housing 74 (pressure accumulator function the arrangement). In addition, the closure body 84 releases the control slot 78 during this time. As a result, fuel, conveyed by a fuel pump 108, flows via the inlet bore 80, a flow chamber 96 and the control slot 78 into a suction line 110, which leads to the pump 100.

5

If the pressure rises above a defined target pressure, the closure body 84 successively closes the control slot 78 and opens the control slot 76. Through the control slot 76 the fuel flows through a parallel line 98 into the flow space 96, where it mixes with the fuel from the low pressure range lo and led to the pump 100.

In other words, in this embodiment, the control slot 76 performs the function of a valve or a pressure control valve for pressure control and the control slot 78, the function of a variable throttle or a suction throttle 15.

From a certain amount of recirculated fuel from the high pressure region of the prevailing overpressure decreases again, so that the spring force is greater again than the force acting against the spring 90 compressive force. Thus, the closure member 84 moves toward the return opening 92 and ultimately closes it. The seal 94 reduces potential leakage in this area.

The closure body 84 and the control slots 76, 78 are furthermore preferably

25 art designed and arranged that the volume, which is the closure body

84 in its movement from its rest position at the return opening 92 until it reaches a control slot 76, 78 releases, the amount of fuel can receive at least one cold start injection. The design of this type realizes an axial free travel of the closure body 84 in the inner housing 74 between

30 see a closure body stop in its rest position and the beginning of a control slot 76, 78 for pressure relief or suction throttling. Thus, the pressure control valve according to the invention prevents a possible, too large pressure drop by the fuel storage function, especially for large injection quantities in the cold start.

35 The geometries (diameter and stroke of the closure body 84, spring rate of the spring 90) of the pressure regulating arrangement are designed so that the storage volume is sufficient to store at least one cold start injection quantity.

In Fig. 3, the assembly 72 of Fig. 2 in an integrative construction with the pump 100 is shown. The pump 100 is positioned below the assembly 72 in a common housing. By such a design short cable routes are possible. Consequently, in this case the weight and the volume of the pressure regulating arrangement is particularly low and improves the quality of control by reducing dead times.

4 shows an enlarged detail of FIG. 3. In particular, the course of the fuel flow is shown here. With a dashed arrow line, the fuel flow from the fuel pump 108, through the inlet bore 80 into the flow chamber 96, and from there again through the control slot 78 in the direction of the pump 100 shown (suction pressure, low pressure region). In addition, the fuel flow is shown with a solid arrow line, which is first performed by the pump 100 to the rail 104 (high-pressure area). A positive pressure is passed through the branch 106 to the return opening 92 and displaces the closure body 84. The return opening 92 is opened and the fuel continues to the control slot 76, and from there through the parallel line 98 to the flow space 96. In the flow space 96, the recirculated fuel unites with the from the inlet of the fuel pump 108. If the pressure drops below the setpoint control pressure again, then the closure body 84 shifts to the left with respect to the figure and opens the control slot 78 for suction throttling and closes the control slot 76 for pressure control. Or, in other words, as soon as the force of the spring 90 is sufficient to push the closure body 84 back against the decreasing force of the overpressure.

In Fig. 5, this function is shown again simplified with the associated components.

Claims

Pressure control arrangement of a fuel injection system for an internal combustion engine (32) operated with a pump (12, 100), with a valve (76) arranged on the pressure side of the pump (12, 100) for discharging fuel under pressure from the pressure side of the pump (12, 100 ) to the suction side of the pump (12, 100),

characterized in that a variable throttle (78) with a variable throttling effect is provided on the suction side of the pump (12, 100) for throttling the amount of fuel supplied to the pump (12, 100).

Pressure control arrangement according to claim 1,

characterized in that the valve (76) is functionally coupled, in particular mechanically coupled, to the variable throttle (78).

Pressure control arrangement according to claim 1 or 2,

characterized in that the valve (76) and the variable throttle (78) are integrated into a structural unit, in particular in the pump (12, 100).

Pressure control arrangement according to one of claims 1 to 3,

characterized in that the function of the valve (76) and that of the variable throttle (78) are implemented with a single closure body (84).

Pressure control arrangement according to claim 4,

characterized in that a first and a second control slot (76, 78) are provided, of which either the first control slot (76) or the second control slot (78) is completely closed in different positions of the closure body (84).

6. Pressure control arrangement according to one of claims 1 to 5,

characterized in that the throttling effect of the variable throttle (78) can be changed by the pressure generated by the pump (12, 100).

7. Pressure control arrangement according to one of claims 1 to 6,

characterized in that a pressure storage function is integrated into this.

8. Pressure control arrangement according to one of claims 1 to 7,

characterized in that a pressure damper function is integrated into this.

9. Pump-operated fuel injection system (10) with a pressure control arrangement according to one of claims 1 to 7.