DE10210300B4 - Pump element for a high-pressure pump and high-pressure pump with controllable flow rate - Google Patents

Abstract

pump element for one High-pressure pump (1) with a in a cylinder bore (15) oscillating Pump piston (17), wherein the cylinder bore (15) and the pump piston (17) a pump room (19) limit, wherein the pump piston (17) is a fluid, in particular Fuel, over sucks a low pressure port (23) in the delivery chamber (19) and in promotes a high pressure port (31), and with a pressure accumulator (35), characterized in that the delivery chamber (19) is permanently in hydraulic communication with the accumulator (35), and that the holding pressure of the pressure accumulator for adjusting the flow rate is controllable.

Description

State of the art

The The invention relates to a pump element for a high-pressure pump the preamble of claim 1 and a high-pressure pump after the sibling Claim 8.

at positive displacement or pumps - too called volumetric pumps - is a delivery room, the z. B. from a cylinder and a piston oscillating therein is limited while he enlarges himself with a low pressure connection connected (suction stroke) and sucks on this Way to promote that Fluid on. If the delivery room shrinking again (delivery stroke), will be located in the pump room Fluid pushed out into a high-pressure channel. This occurs before everything in the high-pressure channel pressure surges, what is disadvantageous.

adversely on many positive displacement machines in addition, that their delivery rate at constant speed is not adjustable. For controlling the flow rate of piston pumps it is known, arranged in a low-pressure connection Inlet valve and / or arranged in the high-pressure passage exhaust valve head for. For example, at the beginning of the delivery stroke a pump element, the inlet valve are turned on, so that that from the pump room funded Fluid not in the high-pressure channel, but back into the low pressure port flows. When the remaining to the top dead center of the piston flow the desired output corresponds, the inlet valve is closed and the pumped from the pumping chamber fluid enters the high-pressure channel. By varying the length of time, while the intake valve is kept open, can in this way the from the displacer machine funded Volume flow adjusted between 0% to 100% of the maximum possible volume flow become.

adversely on this type of flow control is that the inlet valve between the dead centers of the working piston is closed, so that the pump piston at this time already a has considerable speed. As a result, with the Shut down the intake valve of the piston and its drive, consisting for example from a drive shaft with an eccentric, a sudden Exposed to stress. Furthermore leads the erratic change the flow rate in the high pressure passage to a surge in the high pressure passage, which the pressure control in the high-pressure channel and in the adjoining components difficult and possibly the function of components, such as injectors or injectors, at least impaired.

From the DE 195 23 282 A1 An axial piston pump is known in which the swivel angle of the swash plate is adjustable so that the delivery stroke of the pump piston driven by the swash plate can be adjusted. This axial piston pump, in particular its drive via an adjustable swash plate, is relatively expensive to manufacture and can only be used to a limited extent for highest pressures above 1500 bar.

From the DE 1 528 398 A An axial piston pump is also known, in which the flow rate is controlled via the pivot angle of a swash plate. In order to mitigate the pressure surges created during the control of the high-pressure line, the delivery chamber of each pump element is previously connected hydraulically to a pressure accumulator whose holding pressure corresponds to the pressure in the high-pressure line.

From the DE 33 18 236 C2 a fuel injection pump for internal combustion engines is known, the flow rate control is the suction side by a through a solenoid valve. In this fuel injection pump, an accumulator is present, which is hydraulically connected to the delivery chamber from a maximum delivery stroke and is adapted to receive the remaining amount of fuel pumped by the pump piston.

From the DE 2 157 020 A a high-pressure pump is known in which a pressure accumulator is present in the high-pressure line and separated by a check valve from the delivery chamber. With the help of the pressure accumulator, the suction capacity of the high-pressure pump should be improved during commissioning or after a longer standstill.

From the DE 1 948 680 A a high-pressure piston pump is known in which provided to avoid pressure peaks on the pressure side of a pump element, a pressure accumulator.

Of the Invention is based on the object, a pump element for a high-pressure pump and to provide a high-pressure pump whose flow rate in a simple manner is controllable and even at the highest Delivery pressures of over 1500 bar is used. About that In addition, the pressure surges induced by the high pressure pump should be in the high pressure range the fuel injection system can be minimized.

This object is achieved with a pump element for a high-pressure pump according to the preamble of claim 1, characterized in that with a cylinder bore oscillating in a pump piston, wherein the cylinder bore and the pump piston limit a delivery chamber, and wherein the pump piston, a fluid, in particular special fuel, sucks in a low pressure port into the pumping chamber and promotes in a high-pressure channel, and with a pressure accumulator, achieved in that the delivery chamber is permanently in communication with the accumulator hydraulically, and that the holding pressure of the accumulator for adjusting the flow rate is controllable.

Advantages of the invention

at This pump element can the maximum pressure in the pump room be limited by the fact that the holding pressure of hydraulically with the delivery chamber corresponding pressure accumulator is controlled accordingly. As a result, the pressure in the high pressure passage is also limited. By a suitable vote of the holding pressure in the accumulator on the pressure prevailing in the high-pressure channel pressure, the flow rate of the pump element to any value between 0% and 100% set the maximum flow become. There are no impulsive loads on the pump element and pump drive, consisting for example of an eccentric shaft, a polygon ring and roller tappets. In addition, will the unwanted ones Pressure surges in the high-pressure channel degraded as far as possible. This results in a better control quality of the pressure in the high-pressure channel and with the high-pressure channel hydraulically in Connecting components. Also the function of the pump element supplied with high pressure fluid, especially fuel Components will not be affected by the flow control impaired. After all can the pressure energy stored in the pressure accumulator on the next suction stroke be recovered, which improves the pump efficiency.

variants of the invention provide that the pressure accumulator as a piston accumulator, in particular as a spring-loaded piston accumulator, is executed, and / or that the piston accumulator a sealingly guided in a bore accumulator piston having a first end face of the accumulator piston with the pressure of the fluid from the pumping chamber acted upon is, and that acting on a second end face of the accumulator piston Pressure is controlled by a pressure control valve. By this arrangement The holding pressure of the accumulator can be easily adjusted or regulated. Due to the storage effect of the piston accumulator can at least part of the delivery room promoted in the accumulator Fluids during the suction stroke of the pump element back flow back into the delivery chamber, so that minimizes the energy losses in the flow control become.

One another embodiment the pump element according to the invention provides that the second end face of the accumulator piston via a throttle is hydraulically connected to the high pressure passage, so that a static pressure equalization between the high pressure channel and the second end face of the accumulator piston can take place. Especially if the accumulator designed as a spring-loaded piston accumulator can during this static pressure equalization of the accumulator piston by the spring force on a sealing seat in the housing of the pressure accumulator are pressed, so that the pressure of the conveying space applied area the first face of the accumulator piston smaller than the second end face of the Accumulator piston is. This is until reaching a ratio of the pressurized surfaces the first face and the second end face the accumulator piston and the spring force of the compression spring dependent pressure difference the accumulator piston is lifted off the seat and according to the dynamic Balance between the pressure in the high pressure port or the delivery chamber and the on the second end face of the accumulator piston acting hydraulic force as well as on The spring acting on the storage piston pressure in the delivery chamber set.

By the appropriate tuning of the spring rate and biasing force of the compression spring, the size of the first face and the second end face of the accumulator piston, as well as the diameter of the sealing seat can the response and closing behavior of the pressure accumulator within wide limits to the respective conditions of use be adapted.

Around a backflow of the Can prevent fluids from the high pressure passage in the delivery chamber, can be provided that between the delivery chamber and throttle a first check valve is arranged.

The The object mentioned at the outset is likewise achieved by a high-pressure pump, which one or more pump elements according to one of the preceding Having described pump elements, and that each pump element an accumulator is assigned. This high pressure pump has the previously mentioned advantages of the pump elements according to the invention.

Further Embodiments of the high-pressure pump according to the invention provide that on the second end faces of the several pump elements associated pressure accumulator acting pressure from a common Pressure control valve is regulated, so that the construction cost is reduced and the control quality is improved in the high pressure area.

The high pressure pump according to the invention can be constructed as a series pump, radial piston pump, axial piston pump or as a distributor pump. It can be used in particular as a high-pressure pump for fuel injection systems of internal combustion engines with or without common rail, in particular for gasoline and diesel engines are used. Alternatively, the pump can also be used for water jetting or water jet cutting.

Further Advantages and advantageous embodiments of the invention are the subsequent drawing, the description and the claims can be removed.

drawing

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

Description of the embodiment

The invention will be described below with reference to a series pump 1 with two pump elements 3 explained. This series pump 1 can be used in injection systems of internal combustion engines, in particular common-rail injection systems. In the embodiment according to 1 this is also assumed. However, the invention is not limited to use in force injection systems, but can be used anywhere advantageous where liquid media must be promoted under highest pressures. One possible application example is the use in high-pressure hydraulic systems or systems for water-jet cutting or high-pressure cleaning with water.

The row pump 1 has a housing 5 on, in which a drive shaft 7 is rotatably mounted. The bearings are in the figure by the reference numeral 9 characterized. A radial shaft seal 11 seals the interior 13 of the housing 5 against the environment.

In the case 5 are two cylinder bores 15 a pump element 3 incorporated. In the cylinder bores 15 is ever a pump piston 17 fitted so that the pump piston 17 can oscillate in the cylinder bore and the leakage between a delivery chamber 19 and the interior 13 is minimized. The oscillating movement of the pump pistons 17 is through eccentric sections 21 the drive shaft 7 on the pump piston 17 transfer. In 1 are the two pistons 17 shown out of phase by 180 °. The in 1 left piston 17 is at top dead center (TDC), which is in 1 right pistons 17 is at bottom dead center (UT). When the drive shaft is rotated 180 ° (not shown), the right piston is in TDC and the left piston is in TDC.

The cylinder bores 15 and the pump pistons 17 limit, as already mentioned, a pumping room 19 , In the suction phase, ie when the pump piston 17 From the TDC to the UT moves, the pump piston sucks fuel from a low pressure port 23 in the pump room 19 , This is done via a first low-pressure line 25 , In the first low pressure line 25 is for each pump element 3 a trained as a check valve inlet valve 27 built-in. The intake valves 27 prevent the backflow of fuel or other fluid from the pumping chamber 19 in the first connection line 25 during the delivery stroke of the pump elements 3 ,

Via second connecting lines 29 stand the delivery rooms 19 with a high pressure connection 31 hydraulically connected. The high pressure connection 31 is in 1 shown only as a dot. To him, for example, a common rail (not shown) with injectors for each cylinder of the internal combustion engine (also not shown) are connected. Alternatively, injectors or other hydraulic consumers that need to be supplied with a highly pressurized fluid may also be connected.

To the backflow of fuel to the high pressure port 31 in the pumping rooms 19 to prevent is in the second connecting lines 29 just before entering the pumping rooms 19 an outlet valve 33 per pump element 3 arranged. The intake valves 27 and exhaust valves 33 have the function of check valves and can in any known from the prior art embodiment of a pump element according to the invention 3 be used. Up to this point, the functioning of the pump elements corresponds 3 the known from the prior art pump elements.

The delivery rate per revolution of the drive shaft 7 is almost constant over the entire operating range of the high-pressure pump, since, apart from leakage losses between delivery chamber 19 and interior 13 and other losses, always the entire delivery volume 19 during the delivery stroke in the high-pressure connection 31 is encouraged.

In order to control the flow rate of the high pressure pump at a constant speed, each pump element 3 a designed as a piston accumulator hydraulic pressure accumulator 35 assigned. The accumulators 35 consist of a storage piston 37 in a hole 39 is guided sealingly. The seal between bore 39 and storage piston 37 takes place at the in 1 illustrated embodiment via a respective sealing ring 41 ,

The storage piston 37 have a first end face 43 and a second end face 45 on. The holes 39 are at the in 1 shown embodiment as well as the cylinder bores 15 in the case 5 incorporated. The Druckspei They can also be outside the case 5 to be ordered. At the in 1 lower end of the holes 39 is a sealing seat 47 incorporated, on which the pump piston 37 with his first face 43 can sit up. Between the case 5 and the second end face 45 the accumulator piston 37 is a compression spring 49 clamped. The compression spring 49 serves to the storage piston 37 on the seal seat 47 to press.

Between one of the first face 43 of the accumulator piston 37 and the hole 39 limited first pressure room 51 of the accumulator 35 and the pump room 19 the associated pump element 3 is a hydraulic connection via a third connecting line 53 intended. The mouth of the third connection line 53 in the first pressure room 51 is from the sealing seat 47 surrounded, so if the storage piston 37 on the seal seat 47 rests, only those from the sealing seat 47 enclosed partial surface of the first end face 43 of the accumulator piston 37 with the pressure from the pump room 19 is charged. More details will be given later.

A second pressure room 55 from the second end face 45 and the hole 39 is limited, is via a fourth connection line 57 with a pressure control valve 59 connected. The pressure control valve 59 is so controllable that the pressure in the second pressure chambers 55 corresponds to a desired setpoint.

Via a fifth connection line 61 is a hydraulic connection between the second connection line 29 and thus also the delivery rooms 19 and the second pressure chambers 55 produced. In the fifth connection line 61 is a throttle 63 arranged a static pressure equalization between the in the second connecting line 29 and the second pressure chamber 55 prevailing pressure allows. However, the throttle prevents 63 in that the total flow rate of the pump elements 3 in the fourth connecting lines 57 and the second pressure chambers 55 can flow. The compression springs 49 are dimensioned so that at a pressure increase in the delivery rooms 19 the exhaust valves 33 open and thus a hydraulic connection between delivery chambers 19 and high pressure connection 31 allow before the storage piston 37 from the sealing seat 47 take off.

The function of a pump element according to the invention on the in 1 right pump element explains:

Operating case 1: The pressure in one to the high pressure connection 31 connected common rail should be increased (maximum flow):

With the pressure relief valve 59 a control pressure is set, which corresponds to the pressure to be reached in the common rail, not shown. The pressure at the high-pressure connection 31 , on the second connection line 29 , the fourth connection line 57 and the second pressure chambers 55 is the same because over the fifth connection line 61 a pressure equalization is possible. At the beginning of a delivery stroke, ie when the pump piston 17 in UT begins to move towards OT, is the storage piston 37 with his first face 43 on the seal seat 47 on. The closer the pump piston 17 the OT comes, the greater the pressure in the delivery room 19 until finally the exhaust valve 33 opens and the delivery room 19 with the high pressure connection 31 combines. Since the pressure relief valve 59 set holding pressure above the opening pressure of the exhaust valve 33 is, the storage piston remains 37 pressure compensated and retains due to the pressure spring 49 his strength on his seat 47 at. As a result, the entire delivery volume of the pump element via the outlet valve 33 in the high pressure connection 31 promoted. After reaching the TDC, the movement of the pump piston is reversed 17 um, the inlet valve 27 opens and the fluid to be delivered can from the low pressure port 23 in the now increasing delivery room 19 be sucked.

Operating case 2: The pressure in a connected common rail is to be reduced be (per promotion):

With the pressure relief valve 59 is set a control pressure, the reduced pressure in one to the high pressure port 31 connected common rail (not shown) corresponds. Because the pressure in the high pressure port 31 above the pressure relief valve 59 If the pressure is set, fluid flows out of the high-pressure connection 31 over the throttle 63 and the fourth connection line 57 through the pressure relief valve 59 in the first connection line 25 , which with the low pressure connection 23 connected is. Alternatively, the output of the pressure relief valve 59 also lead to a leakage line, not shown. The through the pressure relief valve 59 flowing fluid depends on the size of the throttle 63 from.

Because of the throttle 63 adjusting pressure difference is the pressure in the second pressure chamber 55 of the accumulator 35 lower than the pressure at the high pressure port 31 , At the beginning of a delivery stroke, ie in the illustrated position of the right pump piston 17 in 1 , the poet writes accumulator piston 37 with his seal seat 47 and the sealing ring 41 the first pressure room 51 against the second pressure chamber 55 of the accumulator 35 from. As a result, the pressure in the delivery chamber increases with increasing delivery stroke 19 and therefore also in the first pressure chamber 51 of the accumulator 35 at. When the pressure in the delivery room 19 sufficient to the accumulator piston 37 against the pressure in the second pressure chamber 55 , on the second end face 45 of the accumulator piston 37 acts, and that of the compression spring 49 To exert exerted force lifts the accumulator piston 37 from the seal seat 47 off and from the pump room 19 can fluid over the third connection line 53 in the first pressure room 51 of the accumulator 35 stream. The volume of the first pressure chamber corresponds to this 51 from the pump room 19 in the first pressure room 51 funded amount of fluid. The outlet valve 33 stays closed, so no promotion from the pump room 19 in the high pressure connection 31 he follows. As a result of the leakage flow through the throttle 63 and optionally connected consumers (eg connection valves, not shown), the pressure in the connected common rail (not shown) decreases. After reaching top dead center, the direction of movement of the pump piston is reversed 17 around and the fluid can from the first pressure chamber 51 of the accumulator 35 and from the low pressure port 23 in the now increasing delivery room 19 be sucked.

Operating Case 3: The pressure in a common rail should be held at low flow:

With the pressure relief valve 59 a new pressure is set, which corresponds to the target pressure in the common rail. The pressure at the high-pressure connection 31 and the second pressure chamber 55 the accumulator 35 is because of the static pressure compensation via the throttle 63 equal. At the beginning of a delivery stroke seals the accumulator piston 37 with the sealing seat 47 and the sealing ring 41 the first pressure room 51 that with the pressure from the delivery room 19 is acted upon, against the second pressure chamber 55 from. As the delivery stroke increases, the pressure in the delivery chamber increases 19 until the exhaust valve 33 opens and a promotion takes place in the high-pressure connection. Because of the second end face 45 of the accumulator piston 37 taking hydraulic forces and of the compression spring 49 on the storage piston 37 exerted spring force, the accumulator piston initially retains its position on the sealing seat 47 at. When the exhaust valve 33 is open, fluid can from the pump room 19 in the high pressure connection 31 be further promoted in the common rail, not shown. This increases the pressure in the common rail and in the delivery chamber 19 , The pressure in the second pressure chamber 55 the accumulator 35 but increases because of the throttle 63 and the holding pressure of the pressure relief valve 59 Not. As soon as the pressure in the pump room 19 so far has risen that on the first face 43 acting hydraulic force is greater than the force of the compression spring 49 and the on the second end face 45 acting hydraulic forces, lifts the accumulator piston 37 from the seal seat 47 off, the exhaust valve 33 closes and the fluid gets out of the pumping chamber 19 in the first pressure room 51 promoted. Thus, only a small amount of fluid to the high pressure port 31 sufficient to cover leakages and the needs of common-rail injectors or other consumers. After reaching top dead center, the movement of the pump piston is reversed 17 around and the fluid can from the first pressure chamber 51 and from the low pressure port 23 in the now increasing delivery room 19 flow.

The flow rate control according to the invention can without pressure surges in the high pressure port 31 a continuous flow control of the pump elements at a constant speed of the drive shaft can be realized in a simple manner. For a plurality of pump elements 3 is just a common pressure control valve 59 necessary, which reduces the manufacturing and assembly costs and improves the quality of control. When the pressure control valve 59 is closed without power, even with a defective control of the pressure control valve, the functionality of the pump elements - but without flow control - are maintained.

Claims (13)

Pump element for a high-pressure pump ( 1 ) with one in a cylinder bore ( 15 ) oscillating pump pistons ( 17 ), wherein the cylinder bore ( 15 ) and the pump piston ( 17 ) a delivery room ( 19 ), the pump piston ( 17 ) a fluid, in particular fuel, via a low-pressure connection ( 23 ) in the delivery room ( 19 ) and into a high-pressure connection ( 31 ), and with an accumulator ( 35 ), Characterized in that the feed chamber ( 19 ) permanently with the accumulator ( 35 ) is hydraulically in communication, and that the holding pressure of the pressure accumulator for adjusting the flow rate is controllable. Pump element according to claim 1, characterized in that the pressure accumulator ( 35 ) as a piston accumulator, in particular as a spring-loaded piston accumulator with a on a storage piston ( 37 ) acting spring element ( 49 ) is executed. Pump element according to claim 2, characterized in that the piston accumulator one in a bore ( 39 ) sealingly guided accumulator piston ( 37 ), that a first end face ( 43 ) of the accumulator piston ( 37 ) with the pressure of the fluid from the delivery room ( 19 ) is applied, and that on a second end face ( 45 ) of the accumulator piston ( 37 ) acting pressure from a pressure regulating valve ( 59 ) is regulated. Pump element according to claim 3, characterized in that the pressure accumulator ( 35 ) a sealing seat ( 47 ), that the first end face ( 43 ) of the accumulator piston ( 37 ) with the sealing seat ( 47 ) and that of the sealing seat ( 47 ) limited part of the first end face ( 43 ) with the pressure from the delivery chamber ( 19 ) is also applied when the accumulator piston ( 37 ) on the sealing seat ( 47 ) rests. Pump element according to claim 3 or 4, characterized in that the second end face ( 45 ) of the accumulator piston ( 37 ) via a throttle ( 63 ) with the high-pressure connection ( 31 ) communicates hydraulically. Pump element according to one of the preceding claims, characterized in that a drain ( 57 ) of the pressure regulating valve ( 59 ) with the low pressure connection ( 23 ) or a leakage line is hydraulically connected. Pump element according to one of the preceding claims, characterized in that between pumping space ( 19 ) and throttle ( 63 ) an exhaust valve ( 33 ) is provided. High-pressure pump for conveying fluids, in particular fuel or water, characterized in that the high-pressure pump at least one pump element ( 3 ) according to one of the preceding claims, and that each pump element ( 3 ) an accumulator ( 35 ) assigned. High pressure pump according to claim 8, characterized in that on the second end faces ( 45 ) of the plurality of pump elements ( 3 ) associated pressure accumulator ( 35 ) acting pressure from a common pressure control valve ( 59 ) is regulated. High-pressure pump according to one of claims 8 or 9, characterized in that the high-pressure pump ( 1 ) is constructed as a series pump, axial piston pump or radial piston pump. High-pressure pump according to one of claims 8 or 9, characterized in that the high-pressure pump ( 1 ) is constructed as a distributor pump. High-pressure pump according to one of claims 8 to 11, characterized in that the high-pressure pump ( 1 ) is a high-pressure fuel pump for injection systems of internal combustion engines, in particular gasoline and diesel engines, is. High-pressure pump according to one of claims 8 to 12, characterized in that the high-pressure pump ( 1 ) is a high-pressure fuel pump for common-rail injection systems of internal combustion engines, in particular gasoline and diesel engines, is.