Abstract:
A cylinder head for a compressor includes a closure device that can be adjusted between an unactuated position (off-load) in which the compressor delivers air and an actuated position (off-load) in which the compressor is running in an idle mode, a pneumatic control device having a control cylinder and a control piston that can be moved in the control cylinder, a spring device that prestresses the closure device into the unactuated position (on-load), and a driver configured to couple the control piston to the closure device. The closure device closes a compressed air passage in the unactuated position (on-load) and clears the compressed air passage in the actuated position (off-load), and the driver is permanently connected to the closure device and can be driven by the control piston.

Description:
FIELD OF THE INVENTION 
     The invention generally relates to a cylinder head for a compressor, such as of the type used in a utility vehicle. 
     BACKGROUND OF THE INVENTION 
     Compressors for utility vehicles are generally mounted directly on the motor shaft and driven by the motor. Such compressors deliver compressed air for vehicle-internal compressed air systems, for example, for pneumatic brakes, ride level control systems and other systems. 
     A compressor of the general type under consideration is embodied as a reciprocating piston compressor (reciprocating compressor), and has a compressor casing and a cylinder head that closes the upper side of the compressor casing. A cylinder head gasket is provided between the cylinder head and a cylinder casing. One or more cylinders with pistons that are driven by the motor shaft are formed in the cylinder casing. 
     The compressor is pumping during delivery phases (on-load), while during rest phases and regeneration phases the compressor generally does not deliver any air (off-load). In many utility vehicles, the compressor is rigidly arranged on the motor shaft with the result that at least one piston continues to be moved up and down in the cylinder (reciprocating movement) even during the rest phases and regeneration phases. In order to keep the energy absorption of the piston compressor low, an idling circuit is generally set in which air is merely fed to and fro without being appreciably compressed. Generally, for this purpose, for compressors with only one cylinder, the cylinder space, the volume of which is reduced in the delivery phase, is connected via an air passage to an intake space arranged upstream or a connection space. For compressors with two or more cylinders with movements in opposite directions, cylinder spaces can be connected to one another via an air passage. 
     In order to close and open the air passage, a closure device, which is embodied, for example, as a lamella (leaf), is generally provided in the cylinder head. In its unactuated position (on-load), the closure device closes the air passage, with the result that the compressor can deliver air. In its actuated position (off-load), the closure device opens the air passage, with the result that the compressor runs in the idling mode. 
     The closure device is in turn moved between its actuated position (off-load) and unactuated position (on-load) by a pneumatic control device. For this purpose, the control device receives a pneumatic input signal, generally from a governor. The pneumatic control device generally has a control cylinder that runs in the cylinder head, for example, in a transverse direction, and in which a control piston, on which compressed air coming from the governor acts, is adjustably guided. The cylinder head also includes a spring device. While the spring device is in an unactuated position (on-load), the piston is in a position of rest and the closure device is closed. When compressed air is applied by the governor, the control piston is actuated (off-load) in order to open the closure device. 
     The connection between the control piston and the closure device is generally brought about by a driver, which is attached in the piston and extends through a slot in the cylinder head into the cylinder space. The driver is loosely inserted into a suitable opening in the closure device, with the result that it drives the closure device during the to and fro movement of the piston. 
     During assembly, the control piston is inserted, generally together with the spring device, into the control cylinder. The driver is pressed or screwed into the piston through the slot, with the result that it projects downwardly to the lower side through the slot. The closure device can then be hooked by its hole into the driver from the underside of the cylinder head. 
     Such an assembly, however, does not provide for easy disassembly. This is because the driver, which is permanently connected to the control piston, prevents the control piston from being pulled out of the control cylinder. Thus, removal of the driver from the control cylinder often requires destroying the control piston. 
     Furthermore, although reliable operation and reliable actuation of the closure device is generally possible, the return of the closure device to its unactuated position (on-load) for the loading of the compressor by the spring device can be problematic. According to Hooke&#39;s Law, the force applied by the spring device increases continuously when it is moved by the piston. During the return, the force applied by the spring device in turn decreases linearly, with the result that it becomes ever smaller at the end of the movement during which the closure device is intended to completely close the compressed air passage. In this context, although the spring device can be somewhat prestressed in its unactuated position (on-load), with the result that the spring device still has a residual force for closing the closure device at the end of the movement, the force is still smallest in this part of the movement. For this purpose, compressed air assistance of the spring device can be advantageous. In such a configuration, both compressed air and the spring device act on the piston during the return of the piston. Compressed air can be fed to the piston via a gap, but there can be air leakage for such configurations. 
     SUMMARY OF THE INVENTION 
     Generally speaking, it is an object of the present invention to provide a cylinder head having a driver for coupling a control piston to a closure device, where the closure device closes a compressed air passage in an unactuated position (on-load) and clears the compressed air passage in an actuated position (off-load). 
     The driver can be held firmly in the closure device and can be grasped by the control piston and entrained during the to and fro movement thereof. The driver can therefore be inserted loosely, into the control piston. 
     According to one embodiment, the control piston has a circumferential groove in which the driver is loosely held. 
     According to another embodiment, the driver is positively locked in the closure device. In some embodiments, the driver can be a rivet or rivet pin. 
     According to yet another embodiment, the driver can be disconnected from the control piston by pulling out in a removal direction, where the removal direction is different from the movement direction of the control piston. 
     According to a further embodiment, the closure device is pivotably coupled to a joint, where the closure device can be released from the joint in the removal direction. 
     According to another embodiment of the present invention, a pocket pivotably holds the closure device. The pocket can be formed on the underside of the cylinder head, and can define the pivoting travel of the closure device. The pneumatic control device can be provided above the pocket in the cylinder head. In this context, the cylinder head can be a bearing face for bearing against a cylinder casing, where the bearing face surrounds the pocket. 
     According to a further embodiment, a wall region of the cylinder head is formed between the pocket and the control cylinder, where a gap through which the driver projects is formed in the wall region, and where the driver can be moved in the gap during the movement of the control piston. 
     According to yet another embodiment, the control piston has a piston face and an opposing piston face that lies opposite the piston face. In addition, the control cylinder can have a control space for applying compressed air to the piston face of the control piston in order to actuate the control piston, and a piston space for applying compressed air to the opposing piston face. The control space can have a compressed air connection for feeding in compressed air in order to apply compressed air to the piston face, and for outputting compressed air in order to reset the control piston into the unactuated position (on-load). In addition, when the compressed air is applied, the opposing piston face can assist the spring device in moving the control piston into the unactuated position (on-load), thereby moving the closure device to a closed state. Furthermore, in at least an end part of the closing movement of the closure device, the opposing piston face can be connected to the gap such that compressed air can be applied to the opposing piston face. 
     According to another embodiment, the gap can have an enlarged width in certain regions in order to enlarge the passage area for compressed air in the final part of the closing movement of the closure device. 
     According to a still further embodiment, a free space can be formed in the closure device, where the free space can bear against the gap in the final part of the closing movement in order to permit compressed air to pass through. As a result, the operation of the compressor can be improved. The gap through which the driver projects can be embodied according to the invention in a selective fashion such that the air through-flow is increased in order to improve the resetting of the control piston during its final movement. For this purpose, the gap can be widened in certain regions. The driver therefore does not close the gap entirely at the end of its reset. Furthermore, the feeding in of compressed air for assisting the closing movement is improved. 
     Also, the free space can bear, in the final part of the movement of the closure device, against the gap, with the result that a significant increase in the passage of air, and therefore assistance of the spring device, is selectively brought about. Moreover, when the closure device is in other positions, the free space does not present problems because it does not bear against the gap nor is it aligned with the gap. 
     In accordance with exemplary embodiments of the invention, the cylinder head can be manufactured by inserting the control piston into the control cylinder to form the pneumatic control device, providing the closure device to which the driver is permanently attached, and inserting the closure device into a pocket in the cylinder head in the mounting direction, whereby the driver is guided through a gap between the pocket and the control cylinder and is engaged in a removable fashion in the control piston, and when the closure device is inserted in the mounting direction, an articulated holder for the closure device is formed in the pocket. Disassembly can be accomplished by reversing the order of these steps. 
     It will be appreciated that the inventive embodiments provide a number of advantages. For example, the driver can be easily connected to the control piston, and can also be easily removed from the control piston. Accordingly, system assembly is improved. Furthermore, disassembly is possible with a small amount of expenditure without destroying the control piston. 
     Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification. 
     The present invention accordingly comprises the features of construction, combination of elements, and arrangement of parts as well as the various steps and the relation of one or more of such steps with respect to each of the others, all as exemplified in the following disclosure, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  shows a cylinder head with gaskets for connecting to a cylinder casing in accordance with an embodiment of the present invention; 
         FIG. 2  is a perspective, sectional view of the cylinder head of  FIG. 1 ; 
         FIG. 3  shows a cylinder head without gaskets in accordance with an embodiment of the present invention; and 
         FIG. 4  is a perspective sectional view of a control cylinder in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawing figures,  FIG. 1  shows a cylinder head  1  in a perspective view from below. A cylinder head gasket  2  and an intake valve gasket  3  are fitted onto an underside  1   a  of cylinder head  1 , and are centered, and positioned, for example, by means of centering pins  4 , which protrude from underside  1   a  of cylinder head  1 . A cylinder casing (not shown in  FIG. 1 ) is fitted onto underside  1   a  of cylinder head  1 . An entire compressor can therefore be formed by the cylinder casing and cylinder head  1 , which is fitted on the cylinder casing. One or more cylinders with pistons for compressing air are formed in the cylinder casing. The entire compressor can be connected, for example directly, to the engine shaft of an internal combustion engine of the vehicle. Alternatively, the entire compressor can be in engagement with the internal combustion engine, and therefore be continuously driven when the engine is running. 
       FIG. 2  shows a more detailed, sectional view of the configuration underneath gaskets  2  and  3  ( FIG. 1 ). A pocket  1   b  is provided in cylinder head  1 , in which a closure device  8  can be accommodated such that it can pivot about a joint pin  10  that extends into pocket  1   b . As shown in  FIG. 2 , a lamella can serve as closure device  8 . Persons skilled in the art will appreciate that the closure device need not be limited to a lamella and other suitable structures can serve as closure device  8 . 
     Pocket  1   b  can be formed on underside  1   a  of cylinder head  1 . Cylinder head  1  can be a bearing face for bearing against a cylinder casing, where the bearing face surrounds pocket  1   b . That is, the portion of under side  1   a  exclusive of pocket  1   b  can be considered the bearing face. Joint pin  10  can be aligned, for example, in a flush fashion, with underside  1   a . Pocket  1   b  therefore defines the pivoting travel of the pivotable closure device  8 .  FIG. 2  shows the position of rest in which closure device  8  is in its unactuated (e.g., closed) position (on-load), which constitutes its right-hand position in this view. 
       FIG. 3  shows closure device  8  in its unactuated position (on-load). In  FIG. 3 , a compressed air passage  12  that is concealed by closure device  8  and formed in pocket  1   b  is indicated by dashed lines. When closure device  8  is in the unactuated position (on-load), closure device  8  closes compressed air passage  12 , with the result that the compressor runs in a load mode. Correspondingly, when closure device  8  is in an actuated (off-load) (e.g., idling) position, closure device  8  opens compressed air passage  12 , with the result that the compressor runs in an idling mode. Persons skilled in the art will appreciate that although compressed air passage  12  is shown as having two parts in  FIG. 3 , passage  12  can also have one part. A free space  39  (e.g., slot) is formed in closure device  8 . 
     When closure device  8  is pivoted towards the left from the unactuated position (on-load) into its actuated position (off-load), it opens the compressed air passage  12 , with the result that air can flow from a cylinder space formed in the cylinder casing and through compressed air passage  12  in order to permit an idling operation of the compressor. The compressor therefore operates with relatively low energy consumption without delivering compressed air in an idling operation. 
     Referring back to  FIG. 2 , the adjustment from the shown unactuated position of closure device  8  (on-load) into its actuated position (off-load) is carried out by a control piston  14 , which is guided in a longitudinally adjustable fashion in a control cylinder  16 , where control cylinder  16  is formed underneath pocket  1   b  in cylinder head  1 . Control cylinder  16  and control piston  14 , which can be moved in control cylinder  16 , can be jointly referred to as a “pneumatic control device”. 
     Control piston  14  has a piston face  14   a  to which compressed air is applied in order to actuate control piston  14 . For this purpose, control piston  14  rests, in the basic position or position of rest shown in  FIG. 2 , against a stop  18 , which is screwed into control cylinder  16 . Control piston  14  is sealed in the control cylinder  16  by means of two O-ring seals  14   b ,  14   c , and acts against a helical spring  20 , which is guided on a spring guide  22 . Spring guide  22  is attached in the cylinder head  1 . In the embodiment shown, helical spring  20  is guided into control piston  14  in order to avoid buckling. 
     A wall region  17  of cylinder head  1  is formed between pocket  1   b  and control cylinder  16 . A gap  24 , through which a connection pin  26  projects, is formed in wall region  17 . As shown in  FIG. 2 , a connection pin can be provided as driver  26 . Driver  26  can be embodied, for example, as a rivet (rivet pin) that has a circumferential channel  26   a  with which driver  26  is held in closure device  8 . Driver  26  extends from pocket  1   b  through gap  24  and into control cylinder  16 . Driver  26  further extends into a circumferential groove  28  of control piston  14 . Circumferential groove  28  can disposed around control piston  14 . Driver  26  is therefore entrained (e.g., pulled along) during the longitudinal adjustment of control piston  14 , and, as a result, closure device  8  is pivoted. Driver  26  can be held firmly (e.g., in a positive locking fashion) in closure device  8 . By contrast, driver  26  can rest loosely (e.g., without a clamping effect) in circumferential groove  28  of control piston  14 . 
     Piston face  14   a  is located in a control space  30  which can be filled with compressed air and emptied through a compressed air connection  32 , where compressed air connection  32  can be connected via corresponding valves. By applying compressed air via compressed air connection  32 , control piston  14  can be moved to the left, counter to the effect of helical spring  20  of  FIG. 11   n  the process, control piston  14  entrains driver  26 , with the result that the closure device  8  is pivoted to the left into its actuated position (off-load) from the unactuated position (on-load) (shown in  FIG. 2 ). 
     Consequently, as shown in  FIG. 4 , compressed air passage  12  can be opened. Referring back to  FIG. 2 , control cylinder  16  can also have a spring space  31  to the left of driver  26 . Helical spring  20  can be guided in spring space  31 . An opposing piston face  14   d  can be formed in spring space  31 . 
     As shown in  FIG. 3 , free space  39 , which is formed in closure device  8 , is located next to a widened portion  24   a  (e.g., bend) in gap  24  while closure device  8  is in the actuated position (off-load). As a result, no air can flow through free space  39  into gap  24 . The precise embodiment of widened portion  24   a  of the gap is shown in more detail in the illustration in  FIG. 4 . 
     After the application of compressed air has ended, the venting via compressed air connection  32  can take place. Helical spring  20  therefore relaxes and presses the control piston  14  back (e.g., to the right in  FIG. 2 ). For example, helical spring  20  can press against an end of control piston  14  that lies opposite piston face  14   a . As a result, control piston  14  outputs the air from control space  30  to compressed air connection  32 . As closure device  8  is pivoting back to the right to the unactuated position (on-load), free space  39  overlaps with widened portion  24   a  of gap  24  ( FIG. 4 ). As a result, compressed air now passes from the compressor into pocket  1   b  through free space  39 , and into spring space  31  through widened portion  24   a  of gap  24 . Compressor air can therefore be applied to opposing piston face  14   d , which assists in the closing movement of control piston  14 . 
     The unactuated position (on-load) of closure device  8  is advantageously not defined by a stop in pocket  1   b  but rather by stop  18  of control piston  14 . 
     For the purpose of assembling the arrangement shown in  FIG. 2 , closure device  8  is firstly connected to driver  26 , for which purpose driver  26  is embodied as a rivet with widening end regions. Persons skilled in the art will appreciate that driver  26  can also be embodied, for example, as a screw and/or a nut. Furthermore, spring guide  22  is attached to control cylinder  16 , and control piston  14  and spring  22  are introduced laterally into control cylinder  16  in an axial direction shown by an arrow A. Then, control cylinder  16  can be closed by stop  18 . 
     As shown in  FIG. 2 , closure device  8  together with driver  26  can be inserted from above in a mounting direction shown by an arrow M (e.g., in an installation position of the entire compressor from below), in such a way that closure device  8  is held in (e.g., pivotably coupled to) joint pin  10 . Driver  26  can project into circumferential groove  28  of control piston  14 . 
     For the purpose of disassembly, closure device  8  together with driver  26  can be pulled out, in accordance with a reverse order, from joint pin  10  and control piston  14  in a removal direction counter to the mounting direction. Stop  18  and control piston  14  together with helical spring  20  can then be removed from control cylinder  16  counter to the axial direction. 
     It is to be understood that the present invention is suitable for all types of gas compressor designs, whatever the principle of operation in any individual case. The invention is also suitable for all types of gases. Only as an example, the air compressor using piston construction, such as the one normally used in automotive engineering, is mentioned as a special area of application. 
     It will be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.