WO2017118562A1 - Switching valve for a fuel injection system, high-pressure fuel pump for a fuel injection system, and control method for controlling a switching valve in a high-pressure fuel pump - Google Patents

Abstract

The invention relates to a switching valve (16) for a fuel injection system (10) having a closing element (22) prestressed by a spring (28), wherein the spring force (F_F) of the spring (28) is reversibly variable by means of an adjusting device (54). The invention further relates to a high-pressure fuel pump (12) having such a switching valve (16), and to a control method, by way of which said switching valve (16) can be controlled.

Description

description

Switching valve for a fuel injection system, fuel ^¬ high-pressure pump for a fuel injection system as well as on tax method for driving a switching valve in a high-pressure fuel pump.

The invention relates to a switching valve for a fuel ^¬ injection system of an internal combustion engine, a high-pressure fuel pump for such a fuel injection system, which in particular has a corresponding switching valve, and a drive method for driving such a switching valve, which is arranged in a high-pressure fuel pump. In fuel injection systems, the fuel is usually compressed to a high pressure, for example to a pressure between 1500 bar and 3000 bar with diesel as fuel or a pressure between 150 bar and 500 bar with gasoline as

Fuel in order to be able to meet requirements, for example, for legally prescribed emission values. The pressurized with such a pressure fuel is then injected via injectors in combustion chambers of the internal combustion engine.

In the fuel injection system can be provided at various Po sitions of the path that takes the fuel from a tank to the injectors, valve arrangements, and in particular switching ^¬ valves, for example as inlet or off ^¬ outlet valves of a pressure chamber in which the fuel with the above high pressure is applied. It is also possible to provide such switching valves as relief valves at different positions of the fuel injection system, for example on a common rail, which is connected upstream of the injectors. Currently on the market switching valves that are used in ^¬ example as intake valves in high-pressure fuel pumps, are often controlled by an actuator, such as a solenoid to the flow through the high-pressure fuel pump. When the case of the zero delivery, the medium is, that is, the fuel sucked into the pressure chamber of the high-pressure fuel pump through the Abwärtsbe ^¬ movement of a piston. In the compression phase, the switching valve z. B. is designed as an inlet valve, via a spring, such as a compression spring, as long as kept open until the fuel from a high pressure area can be promoted back into a low pressure region of the fuel injection system. This is called zero promotion. The design of the spring takes place as a function of the flow rate at a maximum rotational speed value of the drive region, which drives the piston in the high-pressure fuel pump. However, this maximum speed value is rarely reached in reality. This causes that even at lower retrieved

Flow through the actuator must overpress the spring force of the spring designed for maximum conditions

Close switching valve. This results in a high energy consumption and additionally results in a high noise emission, caused by higher impact pulses in the

Actuator area.

The object of the invention is therefore to provide an improved switching valve for a fuel injection system of an internal combustion engine.

This object is achieved with a switching valve having the features of independent claim 1.

A high-pressure fuel pump having such a switching valve, as well as a driving method for driving such a switching valve, are the subject of the independent claims.

Advantageous embodiments of the invention are the subject of the dependent claims.

A switching valve for a fuel injection system of an internal combustion engine has a valve region with a Closing element and with a valve seat, which cooperate in operation for closing the switching valve. Furthermore, a spring is provided with a spring force acting along a spring force acting axis in a spring force acting direction for biasing the closing element into an open or closed position and an actuator area for moving the closing element in an actuating force direction opposite to the spring force acting direction. In addition, the switching valve comprises an adjusting device for reversibly changing the spring force of the spring.

As a result of the adjusting device, the spring force of the spring can be actively set for each operating time of the switching valve and thus adapted to a load case in the fuel injection system specific to the respective point in time. Therefore, the adjusting device opens up new, more flexible ways to control the Aktuatorbereiches, which regulates the flow of high-pressure fuel pump for example with an inlet valve of a fuel high-pressure pump ^¬. By the load-specific adaptation of the spring force of the spring, for example, the energy consumption of the actuator area can be reduced. If, for example, the actuator area is also activated in an optimized manner, there are also positive effects on the impact of components in the actuator area during the switching of the switching valve in the form of a reduced pulse, so that the noise emissions of the switching valve can be reduced.

In an advantageous embodiment, the closing element is formed, for example, as a plate-shaped element, which cooperates with a valve plate as a valve seat and is be ^¬ less the valve plate on an opposite side of the spring. Advantageously, the spring biases the closure member before the Öff ^¬ planning position, so that the switching valve must only be operated via the actuator area if it is to be closed. This is energetically cheaper than a preferred one Switching valve, which must open actively, since in the example of the above-described zero promotion, the switching valve must be kept open for a longer period than it remains closed.

Preferably, the spring has a spring length extending along the spring force axis, wherein the verse ^¬ dividing device is designed for reversibly changing the spring length.

It is physically known that the larger the spring length of a spring and thus its spring travel is at a constant spring constant, the smaller is its spring force. If, for example, the spring length is reduced, the executable spring travel of the spring is also reduced and the spring force increases.

Preferably, therefore, a compression device is provided for compressing the spring along the spring force axis, wherein the compression device is in particular formed by a spring force axis along the movable compression piston, on which the spring is supported with a first spring end. The fact that the spring can be supported on the compression device, components for supporting the spring can be saved. Preferably, the adjusting device has a drive unit for driving the compression device, wherein the drive unit comprises an electromechanical actuator and / or an electromagnetic actuator and / or a thermal actuator and / or is formed by a hydraulic transmission. The drive unit is advantageously controllable via a control device, so that the adjusting device can be selectively brought into the desired position as a function of external factors. Advantageously, the adjusting device to a force Determined ^¬ averaging means for determining an oppositely acting upon the closing member to the spring force acting means counterforce. The adjusting device is for changing the Spring force designed such that the spring force during operation of the switching valve at any time greater than the determined counterforce. The counterforce acts from the opposite side to the closing element as the spring force. The counterforce is applied in the example of the high-pressure fuel pump by the hydraulic force on the closing element, which acts on the closing element during the ejection / compression phase of the high-pressure fuel pump. The spring force is preferably at least in the case of the high-pressure fuel pump to keep the closing element in the open position to allow zero delivery. For this reason, during operation the spring force is advantageously greater than the determined counterforce at any time.

The force-determining device preferably has a detection device for detecting a rotational speed of a pump drive of a high-pressure fuel pump of the fuel injection system and a calculation device for calculating the counterforce from the determined rotational speed. To this end, the calculation device advantageously has a conversion device which can convert the determined rotational speed into a pressure value, for example with the aid of a stored characteristic map, wherein the corresponding counterforce can then be calculated from this pressure value.

Preferably, the adjusting device for reversibly changing an actuator force of the actuator region is designed such that during operation of the actuator region

Actuator force is applied, which is greater than the present at the time of operation of the actuator range spring force of the spring. The adjusting device is accordingly not only designed for reversibly changing the spring force of the spring itself, but additionally advantageously also designed to specifically control the actuator region in order to be able to save energy here. Accordingly, the actuator area is controlled at each operating time of the switching valve exactly that the spring force of the spring can be suppressed when the valve is to perform a counter to the spring force acting direction aligned movement. For this purpose, it is advantageously predefined that always the controlled actuator force of the actuator area is adjusted via the adjusting device so that the present spring force can be suppressed at the respective time.

Preferably, the switching valve is designed as an electromagnetic valve, wherein the actuator region a in

Actuator force acting movable armature, a fixed pole piece and a coil, wherein the spring is arranged in particular between the armature and the pole piece and is supported with a second spring end to an anchor surface. The actuation portion is thereby advantageous from a Neten electromagnets, that is, via the coil, driven, which is supplied with ent ^¬ speaking voltage and thus can also be easily controlled via the control device.

Preferably, the armature for transmitting the actuator force is connected to the closing element for moving the closing element into the Aktuatorkraftwirkrichtung or has at least contact. In particular, a pin for connecting or contacting the armature and closing element is provided. If the closing element is formed, for example, as a plate-shaped element, this plate-shaped element is then held by the preferred pin, which in turn is secured to the anchor.

A high-pressure fuel pump for a fuel injection system of an internal combustion engine has a pressure chamber and a switching valve described above. The switching valve comprises a closing element cooperating with a valve seat and a spring biasing the closing element in a spring force acting direction. The switching valve is designed in particular as an inlet valve for admitting a fuel in the pressure chamber. The spring is designed to hold the closing element open against a counterforce acting on the closing element from the pressure chamber, in particular a hydraulic force. In a driving method for driving the switching valve described above, which is preferably arranged in a fuel high-pressure pump ^¬, the following steps are performed:

- Providing a high-pressure fuel pump as described above, having a pressure chamber and a switching valve as an inlet valve for introducing fuel into the pressure chamber, wherein the switching valve, a closing element and a spring with a spring force for biasing the

 Has closing element in an open position;

 Determining a force acting on the closing element from the pressure chamber opposite to the spring force counterforce; Adjusting the spring force so that the spring force is greater than the determined counterforce.

Preferably, when determining the opposing force, a rotational speed of a pump drive of the high-pressure fuel pump is detected and from this rotational speed the opposing force is calculated, in particular with the aid of a conversion factor, which converts the rotational speed into a corresponding pressure value. For this purpose, a map is advantageously stored, which brings the determined speed with a pressure value or the opposing force in connection.

Preferably, the spring force is adjusted so that the spring force is reversibly adjusted. That means the

Spring force can be increased or decreased again after setting.

For example, the spring force is adjusted such that a spring length of the spring is changed, for example by upsetting and relieving the spring. For this purpose, for example, a compression device can be driven with a corresponding drive unit. In addition to adjusting the spring force, it is also possible to adapt an actuator force of an actuator region which actuates the switching valve, to the determined counterforce, in such a way that the Aktuatorkraft, when exercised, at any time greater than the spring force. An advantageous embodiment of the invention will be explained in more detail with reference to the accompanying drawings. It shows:

Fig. 1 is a schematic sectional view of a Teilbe ^¬ riches a fuel injection system with a high-pressure fuel pump, as the inlet valve

Switching valve comprising a spring; and

Fig. 2 is a diagram illustrating a spring characteristic of a compression spring.

Fig. 1 shows a schematic representation of a portion of a fuel injection system 10, which provides a Brennkraftma ^¬ machine with highly pressurized fuel is available, namely the portion of the fuel injection system 10 in which a high-pressure fuel pump 12 is located.

The high-pressure fuel pump 12 has a pressure chamber 14, in which the fuel is subjected to a high pressure during operation, and a switching valve 16, which is formed in the present embodiment as an inlet valve 18 to fuel from a low pressure region 20 of the fuel ^¬ injection system 10 in the Pressure chamber 14 of the high fuel ^¬ pressure pump 12 engage. The switching valve 16 has in a valve region 21 a closing element 22, which as

platelet-shaped element is formed and cooperates with a valve seat 24 formed by a valve seat 26 to hold the switching valve 16 in a closed position. The

Closing element 22 is arranged on the side of the valve plate 24 which faces the pressure chamber 14. On the ge ^¬ opposite side of the valve plate 24, that is, on the side facing away from the pressure chamber 14, there is a spring 28, which is in particular formed as a compression spring, and, indirectly, the closing member 22 holds on its spring force F _F in an open position , In Fig. 1, only one particular embodiment of the switching valve 16 is shown, in which the spring 28 is arranged so that it holds the closing element 22 in the open position about its spring force F _F , but it is also possible to provide a switching valve 16 which is held by the spring 28 in the closed position, for example by a tension spring is provided instead of a compression spring. In the present case, however, the closing element 22 along a Federkraftwirkachse 30 of the spring 28 in a Federkraftwirk ^¬ direction 32, shown by the arrow, biased in the open position.

During operation of the high-pressure fuel pump 12, a piston 34 moves up and down in the pressure chamber 14 and compresses an existing in the pressure chamber 14 medium, such as the

Fuel. This results in the medium, a hydraulic force F _H , which, as shown by the arrow, acts as a counter force F _G from the pressure chamber side on the closing element 22 and forces it in the direction of the closed position. This counteracts the spring force F _{F of} the spring 28, since it is designed at each operating time of the high-pressure fuel pump 12 so that the Fe ^¬ derkraft F _{F is} greater than the respective counterforce F _G from the pressure chamber 14 ago.

In order to be able to close the switching valve 16 nevertheless, an actuator region 36 is provided which engages with an actuator force F _A acting opposite to the spring force F _F

Actuator force acting direction 37, the spring force F _{F can} overpressure, and thus allows the closure member 22 can move to the closed position.

The switching valve 16 is formed in the present embodiment as an electromagnetic valve 38, and has a movable armature 40, a fixed pole piece 42 and a coil 44. When the coil 44 is energized, the armature 40 moves in the direction of the pole piece 42. Since the armature 40 is in contact with the closing element 22 via a pin 46, tightening the armature 40 allows closing of the closing element 22. Depending on the arrangement of the armature 40, that is, with respect to the pole piece 42 on the side facing the valve plate 24 is directed towards, or is arranged away from the switching valve 16 is normally closed or de-energized opened valve formed because the armature 40 in the one position the closing element 22 during its movement

Closed position, and in its other position, the opening position allows.

The coil 44 is driven from outside the fuel high ^¬ pressure pump 12 via a voltage contact 48, the controlled by a control device 50 applies a predetermined voltage to the coil 44 so as to move the armature 40 in the desired manner. The voltage is variable and dependent on the force from the armature 40 on the

Closing element 22 is to be exercised.

The switching valve 16 further comprises an adjusting device 54, with which the spring force F _{F of} the spring 28 can be adjusted. This adjusting device 54 comprises a compression device 56, in the present embodiment, for example, as

Upset piston 58 is formed, which is movable along the spring force axis 30, and on which the spring 28 is supported with a first spring end 60. The spring 28 is in the present

Embodiment arranged in corresponding recesses in the pole piece 42 and the armature 40 and is supported by a second spring end 61 on an anchor surface 52 from. By Be ^¬ mobility of the compression piston 58 along the spring force acting axis 80, the spring can be changed in their extending along the spring force acting axis 30 spring length L _F 28, for example compressed or relaxed.

This change in the spring length L _F is reversible.

2 shows a diagram illustrating the spring force F _{F of} a spring 28 as a function of a spring travel S for different spring lengths L _F. This known as a spring characteristic diagram is particularly applicable to linear compression springs, but also applies to progressive or degressive springs.

As can be seen from the diagram, a compression spring in the untensioned state has an initial length L0. If the spring force F _F Installed on an installation length L _F i, it receives a force Fi at L _F i via its spring rate. If the spring 28 is further compressed on the spring length L _F 2, it has been ascended force F ₂ at this length L _f 2. If the working range is shifted in the direction of LO, that is, in the direction L _F i _* , the spring force F _{F is} reduced further and, as a result, also the required actuator force F _A to overpress the spring force F _F and the switching valve 16 to move. On this basis, the upset piston 58 is adjusted so that the spring force F _{F of} the spring 28 is just sufficient, the

Closing member 22 in the present embodiment to keep against the force acting from the pressure chamber 14 ago counterforce F _G in the Öff ^¬ tion position.

The adjusting device 54 has, in addition to the compression device 56, a drive unit 62 with which the compression device 56 can be actively driven. The drive unit 62 can be realized by various systems and is shown here only schematically, it may be an elekt ^¬ romagnetischen actuator, an electromechanical

Actuator, a thermal actuator or a hyd ^¬ raulische translation act. Of the adjusting device 54, the spring force F _{F of} the spring 28 is ideally biased so as to be greater in each specific load case than the associated hydraulic force F _H , that is, the opposing force F _G. The drive unit 62 is thereby, also controlled by the control ^{¬ device} 50 targeted. To control the correlation between a speed of a pump drive, not shown, of the high-pressure fuel pump 12, which drives the piston 34, and the associated flow is used to form the basis for the load-specific hydraulic force F _H , that is, the counterforce F _G in the return ^¬ promote from the pressure chamber 14 in the low pressure region 20 to determine. This counterforce F _G engages the closing element 22 of the switching valve 16 and wants to press the closing element 22 in the closed position.

In order to determine the reaction force F _G acting from the pressure chamber 14 forth on the closure member 22, has the verse section ^¬ means 54 to a force detecting means 64th The force-determining device 64 in turn comprises a detection device 66, which detects a rotational speed of the mentioned pump drive of the high-pressure fuel pump 12. Furthermore, the force-determining device 64 comprises a calculation device 68, by means of which, based on the determined rotational speed, the counterforce F _G can be calculated. For example, a map may be stored in the control device 50, which brings the determined speed directly in connection with the counterforce F _G , but it is also possible to detour over a

Conversion device to go, which first converts the determined speed into a general pressure value.

Depending on the determined counterforce F _G , the spring length L _{F of} the spring 28 and thus its spring force F _F are then changed via the drive unit 62 or the upsetting device 56.

When the spring force F _{F of} the spring 28 is reduced, even a large actuator force F _{A is} no longer absolutely necessary in order to be able to overpress the spring force F _F. Therefore, based on the determined opposing force F _G , a signal is also output from the control device 50 to the voltage contact 48 in order to apply a lower voltage to the coil 44. Overall, therefore, the switching valve 16 is adapted load-specific, on the one hand with respect to the spring force F _{F of} the spring 28 and on the other hand with respect to the Aktuatorkraft F _A , which is determined by the energization of the coil 44. In addition to a general saving of energy, which is thereby possible, there are also positive effects, since the impact of armature 40 and pole piece 42 when switching the switching valve 16 results in a reduced pulse, so that reduce the noise emissions of the switching valve 16 and thus also the entire high-pressure fuel pump 12.

Claims

claims A switching valve (16) for a fuel injection system (10) of an internal combustion engine, comprising:  a valve portion having a closure member (22) and a valve seat (26) cooperating in operation to close the switching valve (16); a spring (28) having a spring force (F _F ) acting along a spring force acting axis (30) in a spring force acting direction (32) for biasing the closure element (22) into an open or closed position;  an actuator region (36) for moving the closure element (22) into an actuator force action direction (37) opposite the spring force action direction (32); and an adjusting device (54) for reversibly changing the spring force (F _F ) of the spring (28). 2. switching valve (16) according to claim 1, characterized in that the spring (28) has a along the spring force axis (30) extending spring length (L _F ), wherein the adjusting device (54) for reversibly changing the spring length (L _F ) is formed, in particular a compression device (56) for compressing the spring (28) along the spring force active axis (30) is provided, wherein the compression device (56) in particular by a along the Federkraftwirkachse (30) movable compression piston (58) is formed, on which the spring (28) with a first Spring end (60) supported. 3. switching valve (16) according to claim 2, characterized in that the adjusting device (54) has a drive unit (62) for driving the compression device (56), wherein the drive unit (62) an electromechanical actuator and / or an electromagnetic Actuator and / or comprises a thermal actuator and / or is formed by a hydraulic transmission. 4. switching valve (16) according to one of claims 1 to 3, characterized in that the adjusting device (54) has a force detecting means (64) for determining a force acting on the closing element (22) opposite to the Federkraftwirk ^¬ direction (32) counterforce (F _G ), wherein the adjusting device (54) for changing the spring force (F _F ) is formed such that the spring force (F _F ) during operation of the switching valve (16) at any time greater than the he ^¬ averaged counterforce (F _G ). 5. switching valve (16) according to claim 4, characterized in that the force-determining device (64) has a detection device (66) for detecting a rotational speed of a pump drive of a high-pressure fuel pump (12) of the fuel injection system (10) and a calculation device (68) for calculating the counterforce (F _G ) from the determined rotational speed. 6. switching valve (16) according to one of claims 1 to 5, characterized in that the adjusting device (54) for reversibly changing a Aktuatorkraft (F _A ) of the actuator region (36) is designed such that during operation of the Actuator area (36) an actuator force (F _A ) is exerted, which is greater than the spring force (F _F ) of the spring (28) present at the time of operation of the Ak ^¬ tuatorbereiches (36). 7. switching valve (16) according to one of claims 1 to 6, characterized in that the switching valve (16) as an electromagnetic valve (38) is formed, wherein the actuator region (36) in a Aktuatorkraftwirkrichtung (37) movable armature (40), a fixed pole piece (42) and a Coil (44), wherein the spring (28) in particular between the armature (40) and the pole piece (42) is arranged and is supported with a second spring end to an armature surface (52). 8. switching valve (16) according to claim 7, characterized in that the armature (40) for transmitting the actuator force (F _A ) is connected to the closing element (22) for moving the closing element (22) into the actuator force acting direction (37), in particular a pin (46) for connecting or contacting of armature (40) and closing element (22) is provided. 9. High-pressure fuel pump (12) for a Kraftstoffein- injection system (10) of an internal combustion engine, comprising a pressure chamber (14) and a switching valve (16) according to one of claims 1 to 8, which cooperates with a valve seat (26) closing element (22) and a spring (28) biasing the closing element (22) into a spring force acting direction (32), the switching valve (16) being designed in particular as an inlet valve (18) for introducing a fuel into the pressure space (14), the spring (28 ) to keep open the Closing element (22) against one of the pressure chamber (14) on the closing element (22) acting counterforce (F _G ), in particular a hydraulic force (F _H ) is formed. 10. A driving method for driving a switching valve (16) in a high-pressure fuel pump (12) with the steps:  Providing a high-pressure fuel pump (12) according to claim 9 having a pressure chamber (14) and a switching valve (16) as an inlet valve (18) for introducing fuel into the Pressure chamber (14), wherein the switching valve (16) has a closing element (22) and a spring (28) with a spring force (F _F ) for biasing the closing element (22) in an open position; Determining a of the pressure chamber (14) on the closing element (22) opposite to the spring force (F _F ) acting counterforce (F _G ); Adjusting the spring force (F _F ) so that the spring force (F _F ) is greater than the determined counterforce (F _G ).