EP0960275B1 - High pressure pump for supplying fuel in fuel injection systems of internal combustion engines - Google Patents

Description

State of the art

The invention relates to a high pressure pump according to the Preamble of claim 1.

With conventional fuel injection systems, the advance described type is usually independent of need a constant fuel flow through the pre-feed pump in Individual elements of the high pressure pump are promoted. The individual elements of the high pressure pump can, for example be several cylinders, each with a piston back and forth is moved to suck in the fuel and with To apply high pressure. If regardless of need constant speed-dependent fuel flow from the High pressure pump pumped into the common manifold , it means that the power consumption of the High pressure pump is constant even when demand drops. The affects the overall efficiency of the Internal combustion engine. Furthermore, the excess, fuel quantity compressed to high pressure again from the High pressure pump can be shut down, too Temperature increases in the fuel leads.

To improve the overall efficiency of the Internal combustion engine has been proposed to use regulated, electric low pressure feed pump, to the fuel flow to the individual elements of the Control high pressure pump. This solution has among other things however, the disadvantage that the suction stroke of the High pressure pump for damage due to cavitation can come.

From US 5,626,114 is a radial piston high pressure pump where a high pressure side pressure control for everyone Pump elements through a pressure control valve of a valve unit is made. This valve unit consists of a 2/2-way valve with an upstream throttle and a pressure control valve arranged in parallel. This valve unit is on the high pressure side Distribution rail (common rail) and a bypass line of Distribution board connected. The low pressure side is the Valve unit with an unpressurized return line connected.

The 2/2-way valve is at the start of the engine opened so that the high pressure area of the Fuel injection system with the pressure of the pre-feed pump is applied. As soon as the internal combustion engine is running, the 2/2-way valve is closed. In closed The state of the 2/2-way valve takes over in parallel switched pressure control valve the pressure control of the Rail. This means that the high pressure pump always against the one prevailing in the distribution strip High pressure promotes what the aforementioned disadvantages in terms of overall efficiency and fuel heating Has.

EP 0 459 429 A1 describes a high-pressure pump with a Pump element known between the high pressure side and Low pressure side of the pump element a flow valve is provided. This flow valve is controlled so that the desired flow rate to the high pressure side is promoted. The excess fuel is over the Low pressure side returned to the fuel tank. The disadvantage of this flow rate regulation is that for each pump element requires a flow valve, and that the excess fuel in the pump element first pressurized and then in the flow valve is relaxed. This leads to undesirable warming of the fuel and deteriorates the efficiency of the High pressure pump.

A high pressure pump is also included in EP 0 481 964 A2 a pump element has been proposed in which the Filling the pump element and thus also its Flow rate is controlled by a 2/2-way solenoid valve. The 2/2-way valve can do the hydraulic connection between the low pressure side of the high pressure pump and the Release or close the pump element and thereby the Set the delivery rate of the high pressure pump. This Flow control is only possible on high pressure pumps transferable to several pump elements, if for each Pump element a 2/2-way valve is provided. Thereby the costs for the flow rate regulation increase with the Number of pump elements strongly.

The invention is therefore based on the problem of a Provide high pressure pump which the above overcomes disadvantages mentioned. In particular, should Damage to the individual elements of the high pressure pump in the Operation can be avoided. In addition, one should be simple built high pressure pump can be created, the high Security requirements met and still inexpensive can be manufactured.

The problem is solved by those in the independent Disclosed claim high pressure pump solved. Special Embodiments of the invention are in the subclaims disclosed.

The directional valve arranged according to the invention allows the Flow control of a high pressure pump with several Pump elements through a directional valve. This will cost saved in the manufacture of the high pressure pump. moreover the space of the high pressure pump is advantageous limited.

It is also possible with a suitable Control strategy the pressure in the common manifold to regulate to a desired setpoint. The The high pressure pump serves as an actuator in the pressure control loop.

The delivery rate control according to the invention also bears to improve overall engine efficiency because the The power consumption of the high-pressure pump drops as a result. The Demand quantity control according to the invention of the High-pressure pump-supplied fuel flow delivers about it furthermore the advantage that a partial filling of the individual pump elements of the high pressure pump, as in suction control occurs, is avoided. Thereby the risk of cavitation is reduced.

The invention is characterized in that the directional valve is a 3/2-way valve which is installed in the common channel and the common channel in a first valve position with the common manifold and in a second Valve position with the low pressure part of the Fuel injection system connects. In the second Valve position, the fuel flow is depressurized again in the low pressure part of the fuel injection system without to be pressurized. The fuel flow can either be in the fuel tank or in the Connection line between the pre-feed pump and the High pressure pump can be returned. Because the total fuel flow conveyed through the high pressure pump can be divided into a flow and a Lubrication flow in the low pressure part is eliminated.

A special embodiment of the invention is characterized in that between the directional valve and the common check manifold arranged a check valve is. The common channel is in the first valve position connected to the common manifold. By the between the directional valve and the common manifold arranged check valve is achieved that the Fuel from the individual elements of the high pressure pump until the desired pressure is reached is. When the desired pressure is reached, that opens Check valve and the fuel flows into the common manifold. So the fuel will only then pressurized with high pressure in the high pressure pump if the directional control valve is in the first valve position.

Another special embodiment of the invention is characterized in that the directional valve is magnetic can be actuated. By the magnetic actuation of the Directional control valve can achieve short switching times.

Another special embodiment of the invention is characterized in that the high pressure pump a Radial piston pump is one in a pump housing mounted drive shaft, which is eccentric or has cam-like elevations in the circumferential direction, and preferably several radial with respect to the drive shaft comprises pistons arranged in a respective cylinder space, by rotating the drive shaft in each Cylinder space can be moved back and forth in the radial direction are. Such radial piston pumps are especially for Suitable for common rail injection systems. When going back and forth Moving the pistons first, Kaftstoff is sucked in and then condensed.

The present invention generally has the advantage that it can be implemented simply and inexpensively. The The basic idea of the present invention can also be found in simple way on conventional high pressure pumps be used because known components conventional high pressure pumps can be used. This increases the development effort and the cost risk kept low.

Figur 1

zeigt eine schematische Darstellung eines Kraftstoffeinspritzsystems mit einer Hochdruckpumpe und einem Wegeventil in einer ersten Ventilstellung;

Figur 2

zeigt eine schematische Darstellung des Kraftstoffeinspritzsystems aus Figur 1 mit dem Wegeventil in einer zweiten Ventilstellung; und

Figur 3

zeigt eine Ausführungsform einer erfindungsgemäßen Hochdruckpumpe.

Further advantages, features and details of the invention emerge from the subclaims and the following description, in which an exemplary embodiment is described in detail with reference to the drawings. One way of carrying out the claimed invention is explained in detail below with reference to the drawings.

Figure 1

shows a schematic representation of a fuel injection system with a high pressure pump and a directional valve in a first valve position;

Figure 2

shows a schematic representation of the fuel injection system from Figure 1 with the directional control valve in a second valve position; and

Figure 3

shows an embodiment of a high pressure pump according to the invention.

Figure 1 shows a schematic representation of a Fuel injection system with an inventive High pressure pump, which is denoted overall by 1. A Pre-feed pump 2 delivers fuel 4 from a tank 3 through a fuel line 5 to the high pressure pump 1. Die High pressure pump 1 comprises three elements 6, 7, 8. The elements 6, 7, 8 are each formed by a cylinder in which a piston can move back and forth. If the in Figure 1 shown moving piston down Fuel drawn through the fuel line 5. If If the pistons move upwards, the Compressed fuel contained in cylinders and into one joint channel 10 promoted.

In the common channel 10 is a magnetically controlled 3/2-way valve 12 installed. In the shown in Figure 1 Position of the directional valve 12, the fuel passes from the common channel 10 via a return 15 in the Fuel line 5.

In Figure 2 is the same fuel injection system as in Figure 1 shown. The only difference is that the valve is in a different position. In the Position of the directional valve 12 shown in Figure 2 arrives the fuel from the common channel 10 into a channel 11, in which a check valve 13 is attached. in the Operation of the high-pressure pump 1 will continue to run out of fuel promoted the elements 6, 7, 8 in the channel 11 until the Pressure is so great that the check valve 13 opens. Then the high pressure fuel passes through a Line 14 in a common, not shown Rail.

The high pressure pump shown in FIG. 3 is a radial piston pump for high-pressure fuel supply in fuel injection systems of internal combustion engines. The radial piston pump comprises one in a pump housing 20 mounted drive shaft 21 with an eccentric trained shaft section 22. On the eccentric A shaft 23 is provided opposite the shaft section 22 which the shaft section 22 is rotatable. The ring 23 includes several staggered flats against each other one piston 24 is supported. The pistons 24 are each in a cylinder space 25 to the drive shaft 21 in a radial Direction back and forth recorded. The foot of the Piston 24 is designed as a plate 26 on the ring 23 is present. The plate 26 is in each case by a cage 27 attached to the piston 24 and is supported by a spring 28 pressed against the ring 23.

When the drive shaft 21 is rotated, caused the eccentricity of the shaft portion 22 that the piston 24 are moved back and forth in the cylinder rooms 25. If the piston 24 moves toward the drive shaft 21 Fuel from a fuel line 5 in the Cylinder chamber 25 sucked in. If the piston 24 of the Drive shaft 21 is moved away, in the cylinder chamber 25 located fuel via channels 30, 31, 32 in one joint channel 10 promoted. In the common channel 10 the fuel from all cylinder rooms promoted. In the sectional view shown in Figure 3 only one cylinder chamber 25 can be seen, but as a rule are a plurality of cylinder spaces 25 radially to the drive shaft 21 arranged.

During the delivery stroke, a check valve 35 ensures that that the fuel is not from the cylinder chamber 25 in the Fuel line 5 is promoted. Accordingly ensures a check valve 36 during the suction stroke for the Do not fuel from the common channel 10 in the Cylinder chamber 25 is sucked.

In the common channel 10 there is a 3/2-way valve 12 appropriate. The directional control valve 12 has a cylindrical shape Body 41 with a trumpet-shaped closure element 44. Openings 42, 43 are provided in the cylindrical body 41 intended. In the position shown in Figure 3 Directional control valve 12 can fuel from the common Channel 10 through openings 42, 43 in valve body 41 get into a channel 11. In channel 11 is a Check valve 13 attached.

If the pressure in the channel 11 is the so-called rail pressure reached, the check valve 13 and opens with High pressure fuel passes through a Channel 50 via a high pressure line to a common Distribution rail, which is called common rail and in Figure 3 is not shown. In the shown in Figure 3 Position of the 3/2-way valve 12 is therefore at high pressure loaded fuel into the common rail promoted. When fuel is no longer needed, switches the 3/2-way valve to its second position.

In the second position of the 3/2-way valve, not shown is the cylindrical valve body 41 after moved above that it closes channel 11. At the same time, the trumpet-shaped closure element 44 lifts from its seat so that the fuel from the channel 10 comes into a room 51, which with a not shown Return is connected. In the second valve position the unneeded fuel is therefore not under high pressure applied.

Claims (4)

1. High-pressure pump for a fuel injection system of an internal combustion engine, in particular a common-rail fuel injection system, with a high-pressure pump (1) conveying fuel out of a low-pressure part of the fuel injection system, the said low-pressure part containing a fuel tank (3) and a prefeed pump (2), into a common distributor rail of the fuel injection system, an on-demand quantity control (12) for controlling the fuel stream conveyed by the high-pressure pump (1) being integrated into the high-pressure pump (1), the high-pressure pump having a plurality of pump elements (6, 7, 8), the plurality of pump elements (6, 7, 8) conveying fuel into a common duct (10), and the on-demand quantity control comprising a directional valve (12) which delivers the fuel stream conveyed by the high-pressure pump (1), on demand, either to the common distributor rail or to the low-pressure part of the fuel injection system, characterized in that the directional valve is a 3/2-way valve (12) which is mounted in the common duct (10) and which connects the common duct (10) to the common distributor rail in a first valve position and to the low-pressure part of the fuel injection system in a second valve position.
2. High-pressure pump according to Claim 1, characterized in that a non-return valve (13) is arranged between the directional valve (12) and the common distributor rail.
3. High pressure pump according to one of the preceding claims, characterized in that the directional valve (12) can be actuated magnetically.
4. High pressure pump according to one of the preceding claims, characterized in that the high-pressure pump is a radial piston pump which has a drive shaft (21) mounted in a pump casing (20), is designed eccentrically or has cam-like elevations in the cirumferential direction, and comprises preferably a plurality of pistons (24) which are arranged in a respective cylinder space (25) radially in relation to the drive shaft (21) and which can be moved back and forth in the radial direction in the respective cylinder space (25) as a result of the rotation of the drive shaft (21).

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