Patent Publication Number: US-2007107696-A1

Title: Two-stage distribution device of actuating fluid for hydraulically driven pump-injector for internal combustion engines

Description:
TECHNICAL FIELD  
      Present invention relates to the field of internal combustion engines, specifically to diesels and, more specifically, to their hydraulically driven pump-injectors. The proposed distribution device can also be used in other equipment where cyclic delivery of actuating fluid to actuating mechanism is required.  
     BACKGROUND ART  
      A comprehensive technical solution allowing for increasing fuel efficiency and durability, while decreasing noise and especially emission levels in the entire operational envelope of the engine requires a considerable increase in injection pressure (up to 2500 bar) and flexible control of the injection characteristic (2-phase and multiphase injection, and “rate shape”). This problem cannot be efficiently solved by conventional fuel systems with power piston driven by a cam mechanism, whose frequency is directly linked to the rotational speed of the engine&#39;s crankshaft that varies in the course of its operation. This does not allow for optimizing injection parameters in a wide range of operating modes.  
      Modem diesel engines require a highly sophisticated Fuel Injection System (FIS) delivering an ultra high injection pressure, while maintaining split injections per shot with full flexibility and decoupled from engine&#39;s speed and load. Hydraulically driven and electronically controlled pump-injectors with pressure intensification allow for achieving said parameters throughout the entire engine&#39;s operational envelope.  
      For controlling the operation of a hydraulically driven pump-injector, a distribution device is used which enables cyclic delivery of the actuating fluid to the power piston of the pressure intensifier and subsequent removal of the exhaust fluid from the above-piston cavity after the end of the working stroke of the power piston and pumping plunger.  
      In relatively small cylinder displacement diesel engines with relatively low volume fuel delivery, the injection of fuel can be controlled by a distribution device with a single control stage, for instance, a slide or conical valve with electromagnetic or another type of drive.  
      In high-power diesels, used, for instance, in locomotives, off road heavy vehicles, marine applications, and stationary power generation systems, a one-stage distribution device cannot ensure the sufficient flow of the fuel delivered to the hydraulically driven pump-injectors. In hydraulically driven pump-injectors of this class the actuating fluid must be supplied at high rate (up to 1.5×10 4  cm 3 /s). Therefore, even when the speed of the actuating fluid does not exceed 50 m/s (in order to avoid significant losses of the fluid pressure and thus decrease of the pump-injector efficiency), the open-flow cross sectional area of the valve of the distribution device must be at least 3 cm 2 . Such open-flow cross sectional area cannot be practically achieved in a one-stage electronically controlled distribution device of acceptable dimensions and reasonable power consumption of the valve drive. In addition, it is extremely difficult to obtain “rate shape” in a one-stage distributing device. Therefore, in pump-injectors for high-power diesels, two-stage distributing devices must be used, comprising the first stage made as slide, conical or spherical valve with relatively small open-flow cross sectional area and having electromagnetic or another type of drive, and the second stage, having a hydraulic drive controlled by the first stage and thus controlling the supply of the actuating fluid to the above-piston cavity of the power piston of the pressure intensifier.  
      Two-stage distribution device allows for achieving large open-flow cross sectional areas through which the actuating fluid from the accumulator (rail) is introduced into the working cavity of the power piston allowing at the same time for acceptable dimensions of the device and relatively low power consumption for the valve drive of the distribution device. The design of such a distribution device is the subject of the present invention.  
     DISCLOSURE OF INVENTION  
      One of the main design characteristics of the two-stage distribution device according to the invention is that the operation of the second-stage valve (i.e. achieving its reciprocating motion), which in turn controls the operation of the power piston, is controlled by pushrods whose ends are set against the valve ends and whose diameters are considerably smaller than the diameter of the second stage valve. The pushrods have different diameters, and the working cavity of the pushrod of the larger diameter is connected by a channel to the first stage of the distributing device. Controlling the valve by pushrods allows for increasing the diameter and, consequently, the open-flow cross sectional area of the second stage valve so as to allow the required supply to the power pistons and at the same time to decrease the required carrying capacity and power consumption of the electronically controlled valve of the first stage, which in turn controls the operation of said pushrods. All this significantly decreases the dimensions of the distribution device and reduces the power consumption of the first stage drive.  
      In the distribution device in accordance with the invention, two-way valves with conical or spherical sealing surfaces (although slide valves are also possible) in both first and second stages should be preferably used. In conical or spherical valves, compared to slide valves, it seems to be easier to ensure reliable sealing of the working cavities. However, in two-way valves with conical or spherical seat surfaces, good coaxiality between said surfaces and seats of the bearing elements of the device must be provided, in order to facilitate the sealing of the working cavities of valves and pushrods when sealing surfaces of the valve contact said seats. In order to solve this problem, in the distribution device in accordance with the invention the valves are made of one piece or composite and consist of two parts—main section and tail section, divided by a cylindrical protrusion on which sealing conical or spherical surfaces are located concentrically with the valve axis and facing each other, said cylindrical protrusion being disposed in the distributing cavity formed in the valve body, the main section being centered and moving in the body orifice, in which one of the seats is formed, and the tail section moving inside a bushing in which the second bearing edge is formed, said bushing being centered with said tail section of the valve and being freely mounted in said valve body.  
      The distribution device in accordance with the invention allows for controlling the injection characteristics (“rate shape”). To achieve this, the larger-diameter pushrod has a groove and communicates via a channel with the drain cavity, said channel having a jet, and the groove being disposed in such a way that at a given moment of the initial phase of the working stroke of the pushrod with the second stage valve, it is connected with said working cavity of the pushrod.  
     SUMMARY OF THE INVENTION  
      Summary of the invention is provided with regard to hydraulically driven fuel pump-injectors for diesel engines. 
    
    
      In  FIGS. 1, 2 ,  3 ,  4 ,  5 , several embodiments of the invention are shown.  
       FIG. 1  shows an embodiment of a distribution device with a conical (spherical) two-way valve in the first stage and a cylindrical slide valve in the second stage.  
       FIG. 2  shows an embodiment of a distribution device with conical (spherical) two-way valves in both first and second stages  
       FIG. 3  shows a detailed diagram of a conical (spherical) two-way valve of the first stage.  
       FIG. 4  shows a detailed diagram of a conical (spherical) two-way valve of the second stage.  
       FIG. 5  shows a detailed diagram of the larger-diameter pushrod of the second stage valve. 
    
    
      In  FIGS. 1, 2 ,  3 ,  4 , and  5 :  
       1 —first stage valve;  1   a —main section of the first stage valve;  1   b —tail section of the first stage valve;  1   c —disk-like extension on the first stage valve (armature of the electromagnet);  2 —cylindrical protrusion of the first stage valve;  3 —body of the first stage;  4 —return spring of the first stage valve;  5 —first sealing surface of protrusion  2  of the first stage valve;  6 —sealing annular seat of body  3  in the first stage;  7 —groove (cavity) on the first stage valve;  8 —second stage valve;  8   a —main section of the second stage valve;  8   b —tail section of the second stage valve;  9 —larger-diameter pushrod causing valve  8  to perform a working stroke;  10 —body of the second stage valve;  11 —smaller-diameter pushrod causing valve  8  to perform a return stroke;  12 —return spring of the second stage valve (FIGS.  2 ,  4 );  13 —end of valve  8 ;  14 —cylindrical protrusion on valve  8 ;  15 —the first sealing surface of protrusion  14  of valve  8 ;  16 —bearing edge in body  10  of valve  8 ;  17 —channel through which actuating fluid is fed into groove  7  of valve  1 ;  18 —distributing cavity of the valve of the first stage;  19 —working cavity of pushrod  9 ;  20 —channel through which the distributing cavity of valve  1  is communicating with the working cavity of pushrod  9 ;  21 —channels, through which distributing cavity  18  of the first stage is communicating with groove  22  of valve  1 ;  22 —groove of valve  1 , through which the actuating fluid is introduced via channels  21  to channel  23  connected to the drain tank;  23 —channel in body  3  connected to the drain tank;  24 —drain cavity of the lower end of pushrod  9 ;  25 —drain cavity of the upper end of pushrod  11 ;  26 —channel connecting drain cavity  24  of pushrod  9  with the drain tank;  27 —channel connecting drain cavity  25  of pushrod  11  with the drain tank;  28 —working cavity of the smaller-diameter pushrod  11 ;  29 —channel connecting the working cavity  28  of pushrod  11  via jet  30  with the source of the actuating fluid (accumulator);  30 —jet;  31 —distributing cavity of valve  8  of the second stage;  32 —drain channel in body  10 , connecting the distributing cavity  31  of valve  8  with the drain tank;  33 —channels in tail section  8   a  of valve  8 , through which the exhausted actuating fluid is introduced from distributing cavity  31  via groove  34  to the drain channel  32 ;  34 —annular groove in tail section  8   c  of valve  8 , connecting distributing cavity  31  with channels  33 ;  35 —channel connecting distributing cavity  31  of valve  8  with the working cavity  36  of power piston  37 ;  36 —working cavity of power piston  37 ;  37 —power piston;  38 —pumping plunger;  39 —bushing, in which tail section  1   b  of the first stage valve is disposed;  40 —bushing, in which tail section  8   b  of the second stage valve is disposed;  41 —electromagnet of the valve of the first stage;  42 —the second sealing surface of the first stage valve;  43 —annular sealing bearing edge of bushing  39  of the first stage valve;  44 —channel through which distributing cavity  31  of the second stage is connected with the source of the actuating fluid (accumulator) when slide valve  8  is in the extreme lower position (see  FIG. 1, 2  and  4 );  45 —the second sealing surface on protrusion  14  of valve  8 ;  46 —annular sealing bearing edge on bushing  40  of the second stage ( FIG. 4 );  47 —groove (cavity) on valve  8  of the second stage;  48 —axial channel of pushrod  9 , connecting radial channels  49  with jet  51  (here and below in  FIG. 5 );  49 —radial channels of pushrod  9 , connecting groove  50  with axial channel  48 ;  50 —annular groove of pushrod  9 , connecting radial channels  49  with working cavity  19  of pushrod  9 ;  51 —jet, through which actuating fluid is introduced from axial channel  48  into drain cavity  24  of pushrod  9 ;  52 —upper edge of groove  50 ;  53 —lower end of the drain cavity  19  of pushrod  9 .  
      Distribution device in accordance with the invention operates as follows (see  FIGS. 1, 2 ,  3 ,  4 , and  5 ). Between the working strokes (in the dwell position), valve  1  ( FIGS. 1, 2 , and  3 ), having main section  1   a  and tail section  1   b  separated by cylindrical protrusion  2  and disk-like extension  1   c , serving as the armature of electromagnetic drive of the first stage valve, installed in body  3 , is moved to the extreme lower position by spring  4 . At the same time conical or spherical sealing surface  5  of protrusion  2  of the valve is set against the sealing bearing annular edge  6  of body  3 , and seals cavity (groove)  7  formed in valve  1 . In the same dwell period, slide valve  8  ( FIG. 1  or  FIG. 2 , if conical or spherical valve is used), with the larger-diameter pushrod  9  disposed in body  10 , is moved into the extreme upper position by the smaller-diameter pushrod  11  ( FIG. 1 ) or return spring  12  ( FIGS. 2 and 4 ). In case of a slide valve ( FIG. 1 ), it rests against body  10  with its end  13 , and in case of a conical (spherical) valve ( FIG. 4 ), sealing surface  15  of protrusion  14  of valve  8  is pressed to sealing annular bearing edge  16  formed in body  10  of valve  8 . At the same time, the actuating fluid through channel  17  ( FIG. 3 ) is introduced into said annular groove  7  of valve  1 , distributing cavity  18  of the first stage and working cavity  19  of pushrod  9  formed in body  10  near the upper end of pushrod  9  and connected with distributing cavity  18  by channel  20  ( FIGS. 1 and 2 ) are connected via channels  21  and groove  22  ( FIG. 3 ) of valve  1  and channel  23  in body  3  with the drain tank. At the same time, in the second stage ( FIG. 1 ) of the distribution device formed in body  10 , drain cavity  24  near the lower end of pushrod  9  and drain cavity  25  near the upper end of pushrod  11 , respectively, are connected via channels  26  and  27  with the drain tank, and working cavity  28  of the smaller-diameter pushrod  11  is constantly connected with the source of the actuating fluid (accumulator) via channel  29  and jet  30 .  
      In addition, in the dwelling period ( FIG. 1 ), annular groove  47  of valve  8 , bounded by the groove formed on valve  8 , and body  10 , is connected via channel  32  with the drain tank. In the case of a conical (spherical) valve ( FIGS. 2, 4 ), distributing cavity  31  is connected with the drain tank via channels  33  and annular groove  34  of tail section  8   b  of valve  8 ; it is also constantly connected with the drain tank via channel  32  in body  10 , and via channel  35  with working cavity  36  of power piston  37  driving pumping plunger  38 . At the same time, annular groove  47  on valve  8  is constantly connected via channel  44  with the accumulator of the actuating fluid.  
      The design of the distribution device in accordance with the invention is characterized by the fact that conical (spherical) valve  1  (of the first stage) and valve  8  (of the second stage,  FIGS. 2, 3 , and  4 ) are centered and move, respectively, in bushings  39  and  40  ( FIGS. 3, 4 ), with which they form precision-built pairs. Bushings  39  and  40  are freely mounted in bodies  3  and  10 , respectively. When electromagnet  41  is energized, the extended disk section  1   c  of the valve that serves as an armature, is pulled towards the electromagnet, valve  1  due to the electromagnet attraction overcomes the force of spring  4  and travels into extreme upper position, the second sealing surface  42  ( FIG. 3 ) facing sealing surface  5  of said protrusion  2  is pressed to the annular sealing bearing edge  43  of said bushing  39 , and distributing cavity  18  is disconnected from the drain tank. At the same time, the actuating fluid from groove  7  connected by channel  17  with the source of the actuating fluid (accumulator) is introduced into distributing cavity  18  of the first stage valve, and into working cavity  19  of pushrod  9 , via the slot formed between surface  5  and bearing edge  6 . Moved by the pressure of the actuating fluid, pushrod  9  with valve  8  overcomes the force of pushrod  11  ( FIG. 1 ) or spring  12  ( FIG. 2 ) and travels into extreme lower position. At the same time, distributing cavity  31  of valve  8  is disconnected from drain channel  32  ( FIGS. 2 and 4 ) and is connected via channel  44  (in case of a slide valve) with the source (accumulator) of the actuating fluid, which is introduced into working cavity  36  of power piston  37  through channel  35 .  
      If a conical (spherical) valve is used in the second stage ( FIGS. 2 and 4 ), then during the travel of valve  8  downward, the second sealing surface  45  disposed on protrusion  15  facing the first surface  14 , is set against the annular sealing bearing edge  46  formed in bushing  40 , and disconnects distributing cavity  31  from drain channel  32 . At the same time the actuating fluid from the accumulator via channel  44  ( FIGS. 2 and 4 ) is introduced via the slot formed between bearing edge  16  of body  10  and sealing surface  14  of valve  8  into groove  47  of the valve, and then into distributing cavity  31  of the second stage and further via channel  35  into working cavity  36  of power piston  37  that moves pumping plunger  38 , evacuating the fuel via a sprayer unit into the engine&#39;s cylinder head (when the distribution device is used in hydraulically driven pump-injectors).  
      When electromagnet  41  of the first stage valve is de-energized, valve  1  ( FIG. 3 ) moved by spring  4  travels into the extreme lower position, and sealing surface  5  of valve  1  is set against bearing annular edge  6  of body  3 . At this time, distributing cavity  18  of valve  1 , and consequently also working cavity  19  of pushrod  9  are disconnected from cavity  7  (and consequently also from the accumulator) and are connected via the slot formed between the second sealing surface  42  of valve  1  and bearing edge  43  of bushing  39 , and also via channels  21 , annular groove  22  and channel  23  with the drain tank. Due to the pressure drop in working cavity  19 , valve  8  forced by pushrod  11  (in case of a slide valve as shown in  FIG. 1 ) or moved by the spring (when conical or spherical valve is used for the second stage as shown in  FIGS. 2 and 4 ), returns into extreme upper position, ending the working cycle in the device.  
      If the distribution device in accordance with the invention is predominantly used in hydraulically driven pump-injectors with pressure intensifier, the cyclic fuel delivery is controlled by the time that valve  1  stays in the open extreme upper position, which in turn is controlled by the duration of the electrical signal fed to the electromagnet of valve  1 . In order to use the distribution device in accordance with the invention more efficiently, we must control the speed of pushrod  9  in the initial phase of the working stroke of pushrod  9  with valve  8  of the second stage, which allows for changing the rate of the introduction of the actuating fluid into working cavity  36  of power piston  37 , and thus helps decrease the rate of the pressure increase in the initial stage of the injection (i.e., achieve the “rate shape”), and, as mentioned above, helps increase the engines&#39; durability and life, lower its noise and decrease the formation of the toxic nitric oxides in the exhaust gases.  
      To achieve this (see  FIG. 5 ), in pushrod  9 , axial  48  and radial  49  channels and groove  50  are made, and also jet  51 , through which working cavity  19  of pushrod  9  in the beginning phase of its working stroke is connected with drain cavity  24  of pushrod  9 . At the same time, said groove  50  is made in such a way that its upper edge  52  is disposed above the lower end  53  of cavity  19  by the a given value “h” when pushrod  9  is in extreme upper position.  
      As a result, in the beginning of the pushrod&#39;s motion, working cavity  19  of pushrod  9  will be connected with the drain cavity  24  via jet  51 , decreasing the speed of the pushrod moved by the actuating fluid flowing into cavity  19  through channel  20 .  
      It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respect as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.  
     BEST MODE FOR CARRYING OUT THE INVENTION  
      In the proposed distributing device, slide ( FIG. 1 ) or conical (spherical) valves ( FIGS. 1, 2 ,  3 , and  4 ) can be used in both first and second control stages. However, in the preferred embodiment, two-way conical or spherical valves ( FIGS. 2, 3  and  4 ) should be used both in the first and in the second stages.  
      When such a valve is used in the first stage, it seems to be feasible to considerably decrease the stroke of the valve (to 0.08-0.15 mm); this simplifies the design and decreases the dimensions of electromagnet or other valve drives, allowing for reducing the actuation time and improving the response and control of the distribution device, especially when it is used for controlling fast (cyclic) actuating mechanisms, for example, for controlling the operation of the pressure intensifier in hydraulically driven pump-injectors.  
      When using a two-way conical (spherical) valve in the second stage of the distributing device, leakage of the actuating fluid in the closed position of the valve considerably decreases, because the sealing is achieved by tight gapless contact of its sealing surface with the annular bearing edge of the body. When a slide valve is used, the sealing is achieved along the small length of the annular slot formed at the two joining cylindrical surfaces (of the valve and of the body) and through which the actuating fluid from the accumulator is constantly flowing into the drain cavity (even if the valve is connected to the body as a precision pair). Increased leakage of the actuating fluid requires the use of a supply system of the pressure intensifier of large-capacity pumps, which increases the cost of the system and decreases its efficiency.  
      In order to facilitate the assembling of the valve, the disk-like extension (the armature of the electromagnet  1   c  in  FIG. 3 ) is made as a separate unit and is fixed to the tail section of the valve by a thread or another joint. In order to ensure the concentricity between the conical bearing surface of said disk  1   c  and the tail section of valve  1   b , these sections must be processed together after connecting said disk to said tail section.  
      As mentioned above, the distribution device in accordance with the invention can be disposed in an autonomous body or in the body of the actuating mechanism. If the distribution device is used for controlling the operation of the pressure intensifier of hydraulically driven pump-injectors, it is advisable to dispose the second stage directly in the body of the pump-injector, because it allows for reducing the dimensions of the pump-injectors, facilitates their installation in the cylinder head, and shortens the distances connecting the distribution device with the pump-injector. All this increases the reliability of pump-injectors and improves control of the injection process.  
      The proposed distribution device can operate without jet  51  and channels  48  and  49  ( FIG. 5 ). This leads to increased speeds of the second stage valve during the working stroke and in case of hydraulically driven pump-injectors it leads to a sharp increase in the pressure in the beginning phase of injection. If we install said jet  51  and channels  48  and  49  ( FIG. 5 ), the speed of the second stage valve during the working stroke will decrease, and when the distribution device is used in hydraulically driven pump-injectors, the speed of the travel of the power piston with the pumping plunger in the beginning phase of the injection will also decrease, as well as the pressure rise in the forefront of the injection characteristic. As a result, we will achieve the “rate shape” which is required, as mentioned above, for increasing the diesel&#39;s life, decreasing noise and reducing emission levels.  
      The control of the forefront injection characteristic can be further improved if we make groove  50  and channels  48  and  49  in pushrod  9  ( FIG. 5 ) in such a way that the actuating fluid from working cavity  19  of pushrod  9  will flow only during some part of the working stroke of pushrod  9  with the second stage valve  8 , and thus control the duration of the low-intensity phase of the travel of pushrod  9  with valve  8  and better adapt the distributing device, and consequently the pump-injector to the requirements of a specific engine.  
     INDUSTRIAL APPLICABILITY  
      The proposed distribution device is designed primarily for use in hydraulically driven pump-injectors with pressure intensifier. However, the distribution device in accordance with the invention can also be used in other mechanisms and machines where cyclic delivery of the actuating fluid to the actuating mechanism is required. Preferably, two-way distribution device of the actuating fluid should be used in hydraulically driven pump-injectors for diesels with relatively high volume fuel deliveries used for example in heavy off roads and other vehicles, locomotives, marine applications, and as stationary power generators.  
      In pump-injectors for such diesels, the actuating fluid must be supplied to the power piston of the pressure intensifier at high volume rate, achievable only when a two-stage distribution device is used that represents the subject of the present invention.