Abstract:
An injector for injecting fuel in a combustion chamber of an internal combustion engine has an injector housing, 2/2-way double valves received in the injector housing and coupled with one another for joint vertical movements, a hydraulic multiplier associated with the 2/2-way-control valves, a nozzle chamber which surrounds a nozzle needle and supplied with high pressure fuel by the hydraulic multiplier, the 2/2-way control valves in the housing being turned relative to one another and have valve bodies and guiding elements which surround the valve bodies.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a pressure/stroke controlled injector with a hydraulic convertor or multiplier. 
     In fuel injection systems for injection of fuel in combustion chambers of internal combustion engines nowadays electrically controlled injectors are utilized. Injection start and injection end are adjusted with them. The injectors are mounted preferably by clamping devices on a cylinder head of an internal combustion engine. Thereby injectors which are loaded via a high pressure collecting chamber (common rail) can be mounted on the cylinder head of the internal combustion engines without substantial changes. 
     German patent document DE 198 235 494 discloses a pump-nozzle unit which operates for the fuel supply in combustion chambers of direct-injection internal combustion engines. For providing a pump-nozzle unit, which has a simple construction, a small size and in particular a short response time it is proposed to form the valve actuator as a piezo electric actuator. 
     The pump-nozzle unit disclosed in this document has a hydraulic convertor or multiplier device which performs various functions. First, it represents a rigid connection between the valve actuating unit and the control valve and ensures therefore a secure and reliable transmission of the expansion movement of the piezo-electric actuator to the A-valve. Moreover, the expansion movement of the valve actuating unit is deviated by the hydraulic multiplier device into a differently directed valve actuating movement. In the shown example the downwardly oriented expansion movement of the piezo-electric actuator is converted into an upwardly oriented valve actuating movement, or in other words the valve actuating movement oriented in an opposite direction. Moreover, by a respective selection of the surfaces of the valve actuating unit which cooperate with the hydraulic multiplier device on the one hand and the control valve on the other hand, a desired multiplication ratio between the expansion movement of the piezo-electric actuator and the valve actuating movement is provided. Relatively small expansion movements of the piezo-electric actuator can be converted into relatively great valve actuating movements. 
     Finally, the hydraulic multiplier device serves also as a thermal compensation element between the valve actuating unit and the control valve. In this function, the hydraulic multiplier device compensates the action of various temperature coefficients of the piezo-electric actuator on the one hand and the A valve on the other hand. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of present invention to provide a pressure/stroke controlled injector which avoids the disadvantages of the prior art. 
     More particularly, it is an object of the present invention to provide a pressure/stroke controlled injector which is actuatable by a single control element. 
     In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a combustion chamber of an internal combustion engine, comprising an injector housing; 2/2-way double valves received in said injector housing and coupled with one another for joint vertical movements; a hydraulic multiplier associated with said 2/2-way-control valves; a nozzle chamber which surrounds a nozzle needle and supplied with high pressure fuel by said hydraulic multiplier, said 2/2-way control valves in said housing being turned relative to one another and have valve bodies and guiding elements which surround said valve bodies. 
     With the proposed solution, a hydraulic multiplier is realized, which is completely forced-compensated, so that the utilized control element must apply small control forces for providing an actuation of the parallel connected 2/2-way control valves. When however such low control forces are required, the inventive injector can be connected with a magnet. With magnets as actuating units, a lasting operation of the injector over the service life of the fuel injection system is ensured. 
     The force compensation unit of the 2/2-way valves with the hydraulic multiplier is provided by the turning relative to one another with respect to their opening direction. For obtaining the force compensation in the valve body of the 2/2-way valves, the both valve bodies are formed symmetrically, but turned relative to one another. The valve bodies which are movable in the housing of the injector in the vertical direction up and down have a first diameter, while guiding sleeves are received on them and have a second diameter which exceeds the first diameter. The guiding sleeves which have the second diameter are provided with ring-shaped abutment surfaces which limit the maximum vertical covered path of the valve body. Each valve body which operates as the 2/2-way valve is loaded with a spring element which, with the complete force compensation unit of the valve, applies the force to be overcome by the actuating unit. 
     An overflow connection between both valve chambers is provided between the both parallel actuated, pressure-compensated 2/2-way control valves. An inlet to a hydraulic multiplier branches from the above mentioned overflow connection. It fills the nozzle chamber which surrounds an injection nozzle in the region of a pressure stage, with fuel under high pressure. A closing piston is formed on the nozzle needle and cooperates with a control chamber volume enclosed in a control chamber. The pressure release in the control chamber leads to an outside movement of the nozzle needle from its seat and thereby to a release of the injection openings in the combustion chamber of the internal combustion engine. The control chamber in turn can be pressure loaded with an outlet nozzle released by an actuator. 
     The parallel connection of the 2/2-way control valve allows a control of the valve body so that during a release of the sealing seat one seat of one of the valve bodies of the 2/2-way control valve, the other moves to its sealing seat and vice versa. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing a longitudinal section of an injector housing in accordance with the present invention which receives two neighboring 2/2-way control valves, a hydraulic multiplier as well as a needle nozzle provided with a closing piston. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An inventive injector is shown in a longitudinal section in FIG.  1 . Two 2/2-way control valves  8  and  38  are accommodated in a housing of the injector. Under the both 2/2-way control valves  8  and  31 , a hydraulic multiplier  26  which is loaded with them for pressure multiplication is located. A needle nozzle  31  provided with a closing piston projection  34  is also located near the multiplier. 
     The valve bodies  17  and  41  of the both 2-2/way control valves  8  and  38  located near one another are controlled through a common bridge  4 . The bridge  4  is a part of a magnetic armature  2  which is controlled by a ring magnetic  1  schematically represented as a magnetic coil. An axial  3  which simultaneously loads the both valve members  17  and  41  is located under the magnetic armature  2 . Reference numeral  5  identifies corresponding lines of symmetry both of the axial  3  and of the both valve bodies  17  and  41  located in the injector housing. In the upper region the both valve bodies  17  and  41  of the both 2/2-way control valves have a first diameter  11  and extend through a fixing disc which is provided with openings  7 . 
     A constriction  14  is formed in a first 2/2-way control valve  8  which faces the inlet, on the valve body  17  in the region of the inlet  13  from a high pressure collecting chamber (common rail). The constriction  14  runs of the valve body  17  of the first 2/2-way control valve  8  from a seal diameter  15  which cooperates with a sealing seat provided in the housing. The conical expansion of the valve body  17  connected with the diameter  15  extends to a downwardly extending valve chamber  16 . Under the valve body portion which has an increased diameter and which follows the conical extension of the valve body  17 , the valve body  17  again assumes the first diameter  11 . 
     The valve body  17  is surrounded inside the valve chamber  16  by a guiding sleeve  23 . The guiding sleeve  23  extends with a sealing edge under the sealing action outwardly, into the valve chamber  16  of the housing of the inventive injector. The guiding sleeve  23  has a second diameter  12  which exceeds the first diameter  11  of the valve body  17 . The guiding sleeve  23  is secured in the housing of the injector by a screw insert  24 . The valve body  17  extends through the guiding sleeve  23  received in the housing with its diameter  11 , and at an end surface is provided with a pin-shaped projection  19  which coincides with the upper ring surface of the guiding sleeve  23 . The pin-shaped projection  19  is surrounded by a spring  20  which acts on the pin-shaped projection  19  and the lower ring-shaped end surface of the valve body  17 . The spring element  20  biases the valve body  17  of the first 2/2-way control valve in a vertical direction upwardly toward the ridge  4 . 
     A transverse opening  21  extends from the valve chamber  16  of the first 2/2-way control valve  8  into a valve chamber  16  of the second 2/2-way control valve  38  in the housing of the inventive injector. A valve body  41  which is movable parallel to the first valve body  17  is received in the valve chamber  16  of the second 2/2-way control valve  38 . It is turned relative to the first valve body  17  of the first 2/2-way control valve  8 . The valve body  41  formed with the first diameter  11  is surrounded in its upper region by a guiding sleeve  9  which has the second diameter  12 . It is extends with a sealing edge  10  outwardly sealingly in the housing of the inventive injector. The guiding element  9  is fixed with the housing, so that the valve body  41  moves parallel to the valve body  17  of the first mentioned 2/2-way control valve engine in the injector housing, through the bridge  4  which acts on both valve bodies. The sealing seat  39  on the valve body  41  is formed opposite to the sealing surface  15  on the first valve body  17 . It has conically downwardly reducing sealing surface, while the conical region on the valve body  17  is oriented upwardly. 
     A constriction  42  under the conical sealing region is provided in the second valve body  41  and extends in the sealing diameter  39 . Before the valve body  41  of the second 2/2-way control valve  38  it extends again into the first diameter  11 . It is loaded by a spring element  43  at the lower end side of the valve body  41  of the second 2/2-way control valve  38 , so that the valve body  41  is biased vertically upwardly. In the region of the constriction  42 , for opening or closing by the conical sealing surface  39 , a control chamber inlet  37  extends to the control chamber  35 . A pressure is applied to it by a closing piston  34  of the nozzle needle  31 . The control chamber  35  provided in the injector housing is variable via an outlet throttle  36  with respect to the pressure acting in the control chamber  35 . The closing piston  34  of the nozzle needle  31  is displaceable in a hollow chamber inside the housing of the injector and, depending on the pressure change in the control chamber  35 , is movable vertically upwardly or downwardly. A sealing spring element  32  acts on the nozzle needle  31  on a ring surface. 
     An inlet line  22  to a hydraulic multiplier  26  extends from the both valve chambers  16  of the both 2/2-way control valves  8  and  38  at the inlet and outlet side. The hydraulic multiplier  26  includes a piston-shaped element  27  which is biased by spring  28 . When the inlet line  22  to the hydraulic multiplier  26  is loaded, a nozzle chamber inlet  29  is loaded with fuel volumes under high pressure, which therefore occurs in a nozzle chamber  30 , surrounding the nozzle needle  31  in the region of the pressure stage  36 . When the nozzle space inlet  29  is loaded, then the high pressure which acts in the nozzle chamber  30  provides through the pressure stage  33  a vertical outward movement of the nozzle needle  31  against the action of the sealing spring  32 , and thereby the upper end side of the closing piston  33  moves inwardly into the surrounding control chamber  35  in the housing of the injector. 
     A first 2/2-way control valve  8  at the primary side and the second 2/2-way control valve  38  at the outlet side are completely force compensated because of the two identical guiding elements  9  which have both the second diameter  12  as well as because of the valve body  17  and  41  which have the identical diameter  11 . The both guiding sleeves  9  and  23  are formed so that on the one hand they are arranged fixed in the housing and on the other hand a sealing action is deployed outwardly. The provided hydraulic diameter in the both valve chambers  16  of the first and the second 2/2-way control valves  8  and  38  are identical. 
     When the ring magnet  11  is energized, the armature bridge  2  moves in a vertical direction downwardly. Thereby the both valve bodies  17  and  41  of the first and the second 2/2-way control valves  8  and  38  move downwardly. At the inlet side, the vertical downward movement of the conical sealing seat on the valve body  17  provides an opening of the inlet  13  to the high pressure collecting chamber (common rail). The transverse opening  21  is supplied with fuel which is supplied under high pressure in the valve chamber  16  of the 2/2-way control valve located at the inlet side, so that the high pressure fuel volume enters also the valve chamber  16  of the 2/2-way control valve  38  at the outlet side. There the vertical downward movement of the valve body  41  provides the opposite effect. The conical sealing surface  39  on the valve body  41  of the 2/2-way control valve  38  at the outlet side provides a closing movement of the valve body  41  in its sealing seat on the housing of the inventive injector. 
     During the overflow process through the transverse opening  21  from the valve chamber  16  at the inlet side to the valve chamber  16  at the outlet side fuel with high pressure acts on the hydraulic multiplier  26  through the inlet  22 . The piston  21  of the hydraulic multiplier  26  acts on the control volume provided in a control chamber, so that it is provided under high pressure via the nozzle chamber inlet  29  on the nozzle chamber  38  which surrounds the nozzle needle  31 . Through the pressure stage  33  on the needle nozzle  31 , the needle nozzle  31  moves against the action of the sealing spring  32 . The closing piston  34  moves into the control chamber  35 , so that with an available stroke path  40  a pressure-controlled injection can be performed. 
     Since the conical sealing surface  39  on the valve body  41  makes possible covering a stroke way  40 , therefore after a first pressure-controlled injection via the hydraulic multiplier  2  a post injection is possible. The stroke-control post injection is made possible by the 2/2-way control valve  38  provided at the outlet side whose conical sealing surface makes possible covering a stroke path  40 . For performing a post-injection, the conical sealing region  39  of the valve body  41  of the second 2/2-way control valve remains in an opening releasing position which corresponds to the stroke path  40 , so that the control volume can flow out of the control chamber  35 . With the highest pressure produced simultaneously in the nozzle chamber, transmitted through the nozzle chamber inlet  29  from the hydraulic multiplier  26 , the nozzle needle  31  can open for a short time for performing a post injection. 
     With the completely pressure equalizing unit of the both 2/2-way control valve  8  and  38  which are received near one another in the injection housing, spring forces transmitted through the restoring springs  20  and  43  are applied to the valve bodies  17  and  41 . Hydraulic forces do not have to be overcome by the control element  1  which is common for both 2/2-way control valves  8  and  38 . Thereby the injector shown in FIG. 1 can be provided with a magnet, whose longevity is in the region of the service life of a fuel injection system. As for the use of the same components, it is especially advantageous when sleeve elements  9  and  23  which correspond to one another can be used on the valve bodies  17  and  41  of the both 2/2-way control valves. For optimization of manufacture it will be ideal when in the inventive injector the same identical valve body  17  and  41  can be used, which have identical diameters  11  with conical sealing surfaces formed opposite to one another. It should be further mentioned that the constrictions  14  and  42  on both valve bodies  17  and  41  which are displaceable vertically in the injector housing are provided opposite to one another. In FIG. 1 a magnet armature  2 , in bridge  4 , which is connected with magnet armature  2  are shown schematically. The mechanical connection of the vertical upward movement produced by the control of an energized actuating unit  1  can be performed in a different way. It is important however that the vertical upward or the vertical downward movements of the valve body  17  and  41  of the control valve 2/2-way  8  at the inlet side and the 2-2/way control valve  38  at the outlet side are performed parallel to one another and with the same stroke path. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in pressure/stroke controlled injector with hydraulic multiplier, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
     What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.