Abstract:
The invention relates to a valve arrangement with a pressure limiting valve and a flow regulator valve, which comprises a flow regulator piston, having at least one first hydraulic resistor, distinguished in that the flow regulator valve&#39;s ( 5 ) flow regulator piston ( 15 ) has a split pressure return surface and in that the first part (ring surface ( 45 )) of the pressure return surface is capable of working at a pressure p 1  and a second part (annulus surface ( 31 )) of the pressure return surface is capable of working at a pressure p 2.

Description:
DESCRIPTION  
         [0001]    The invention relates to a valve arrangement in accordance with the preamble of claim  1 , and a pump for a gear system in accordance with the preamble of claim  23 .  
           [0002]    Valve arrangements of the type detailed here are well known. They have a pressure limiting valve which acts as a pilot valve stage, and are fitted with a valve body which is adjustable against a spring force, they also have an flow regulator valve which contains a control piston that is located in a hollow and adjustable against a spring force, this regulator valve acts as a main stage. These serve to influence a stream of a volume of fluid supplied, for example, by a pump, and also the pressure of this liquid.  
           [0003]    The pump supplies, for example, the gear system of a motor vehicle particularly a revolution-torque converter, an automatic or CVT gear system and/or a power steering system the system of liquid supplied to the consumer must be set to a certain amount. To this ends the main stage, the flow regulator valve, is used. The pressure limiting valve, which is also described as a pressure pilot, is used to set the maximum pressure of the medium supplied from the pump. It has emerged that the construction of the valve arrangement is, in many cases, costly and space-intensive. Often, different demands are made of the spatial arrangement of the pressure and suction connections of a pump containing a valve arrangement of the type discussed here. There are, for example in automatic gear system, tight spatial relations and/or there are mounting positions which are difficult to access. In addition, the connections and the main oil flow mechanism are pre-set in many cases. Moreover, in automatic gear systems, the valves are some distance away from the pump, meaning that the charging of the pump is poor, and the proportion of air in the oil is also large.  
           [0004]    Therefore the aim of the invention is to create a valve arrangement of the type named at the beginning which does not exhibit these disadvantages.  
           [0005]    In order to resolve this problem, a valve arrangement is proposed which demonstrates the features named in claim  1 . The valve arrangement is characterised in that the flow regulator valve has a flow regulator piston with an initial hydraulic resistor which has a split pressure return surface. The first part of the surface of the pressure return surface is impacted with a pressure p 1 , and the second with the pressure p 2 . The split pressure return surface allows the main oil flow to flow through the flow regulator valve and also gives it a pressure limiting function, which would preferably be as a result of the pressure p 2 . This not only simplifies the guiding of the flow of medium, but also reduces the size of the pressure limiting valve. This means that the valve arrangement and a pump can be arranged within a single casing in confined spaces  
           [0006]    An embodiment of the valve arrangement is preferred which is characterised in that the two parts of the surface of the pressure return surface are separated by a second hydraulic resistor, which can be arranged after the first hydraulic resistor—in the direction of flow and integrated into the flow regulator piston. Alternatively, the second hydraulic resistor can also be within the casing. This means that the structure is very compact and the guiding of the medium within the pump is simplified. In the preferred embodiment, the hydraulic resistors take the form of baffles.  
           [0007]    In a particularly preferred example embodiment of the valve arrangement, the clutch mechanism takes the form of a plug which is inserted into a socket in the gear system. Preferably it is ensured that the clutch mechanism, i.e. the plug and the socket, is cylindrical in form. In particular, it is ensured that the outer diameter of the plug is chosen so that it is only very slightly less than the internal diameter of the socket, which means that the valve arrangement or the pump can be positioned particularly simply and precisely in relation to the gear system.  
           [0008]    A particularly preferred embodiment is characterised in that the sleeve surface of the cylindrical plug and/or the inner walls of the socket has/have a circular seal. This means that a seal can be achieved which is independent of the external characteristics of the housing of the valve arrangement or the pump and the housing or the flange of the gear system. Therefore the seal of the connection between the valve arrangement and the gear system is independent of the size of the gap between the flange of the gear system and the housing of the valve arrangement.  
           [0009]    The invention also relates to a pump for a gear system, particularly an automatic gear system, where the pump, a gear control system, a revolutions/torque conversion unit and a valve for limiting the volume flow and/or limiting pressure and/or pressure modulation of the system pressure of the working medium of the leading system are arranged within a common gear system casing. According to claim  24 , the invention provides the valve allocated to the pump, specifically integrated within the casing of the pump. This is advantageous inasmuch as the particularly close arrangement between the pump and the valve allows short connections between these two components, which means that high volume flows can be supplied in the pump with a low level of loss. Oil flowing from the valve mechanism can also be used to charge the pump better, as the oil is returned directly via short routes.  
           [0010]    For example, a flow regulator valve to limit flow volume and/or a pressure limiting or safety valve to limit pressure and/or a ‘main pressure valve’ to modulate pressure can be used as the valve which as allocated to the pump. This valve or valves can also be externally influenced by an active component. What is known as a proportional valve should be mentioned specifically here, this can provide a modulated pre-control pressure for the valve, so that what is known as a pre-control circuit is formed. Alternatively, it can also be arranged so that the valve can be influenced by a magnet, a spring or any number of pressures present in the hydraulic system. This means that the line of the flow volume course can be set to be adjusted or influenced according to the operational states of the gear system.  
           [0011]    Particularly preferred is an example embodiment of the gear pump where the valve arrangement in accordance with one or more of claims  1  to  22  is used for the valve. Alternatively or additionally, what is known as a main pressure valve can be used.  
           [0012]    In a particularly preferred embodiment, the gear pump takes the form of a wing cell pump or a roller cell pump, which is at least one stroke, i.e. has one suction chamber and one pressure chamber each. This type of wing cell pump and roller cell pump is characterised by a stroke ring which influences the inward and outward motion of the wings or rollers. At least one suction channel of the pump is adjacent to a hollow in the stroke ring, so that the cross section of the suction channel is extended. This is a simple way of ensuring that the suction resistance for the working medium is reduced, so that there are slight low pressure in the pump area.  
           [0013]    Particularly preferred is an embodiment where the hollow is open at the edges and where the open side is arranged opposite a suction pocket which can be formed, for example, in what is known as a pressure plate Therefore the mouth of the hollow is in a lateral surface of the stroke ring, meaning that the cross section of the suction channel in the area of the suction pocket and the hollow is increased  
           [0014]    In a particularly preferred embodiment, the hollow which is open at the sides has a rounded section on at least one of the areas between its mouth and its limiting walls at the sides. Preferably, the area between the mouth and a side wall which lies within the large circle of the stroke ring should be chosen. It is particularly advantageous if—going from the mouth towards the side wall—there are two cut-out sections, so that the mouth continually climbs into the first section via an area, in order then to pass into a smaller rounded section. The transfer areas formed in accordance with the invention do not have any major influence on the stability of the stroke ring itself, as the notching effect is low here  
           [0015]    Further embodiments are given be the remaining subordinate claims 
       
    
    
       [0016]    In the following, the invention is explained in more detail with the aid of the drawings  
         [0017]    [0017]FIG. 1 Shows a top view of a partial section of a valve arrangement integrated into a pump  
         [0018]    [0018]FIG. 2 a  Shows the pump shown in FIG. 1 as a longitudinal section  
         [0019]    [0019]FIG. 2 b  Shows a section of a pump modified from that shown in FIG. 1 
         [0020]    [0020]FIG. 3 a  Shows a basic connections diagram for the pumps shown in FIGS. 1 and 2 
         [0021]    [0021]FIG. 3 b  Shows a block connections diagram for a gear system  
         [0022]    [0022]FIG. 4 Shows a second embodiment of a pump allocated to the valve mechanism shown in FIG. 1  
         [0023]    [0023]FIG. 5 Shows a side view of a stroke ring from a wing cell pump or a roller cell pump  
         [0024]    [0024]FIG. 6 Shows a section view along line VI-VI in FIG. 5  
         [0025]    [0025]FIG. 7 Shows a section view along line VII-VII in FIG. 5 
     
    
       [0026]    For the following description the basis premise is made, purely as an example, that the valve arrangement is working in conjunction with a pump. Generally, the valve arrangement can also be used for hydraulic controls, particularly of a gear system  
         [0027]    The top view, as shown in FIG. 1, shows a partial section of a pump  1 . From this drawing, it can be recognised that the pump  1  is integrated in a valve arrangement  2  within a housing  3 , this valve arrangement  2  includes a flow regulator valve  5  and a pressure limiting valve  7  The pressure limiting valve  5  is set in a opening  9  which goes through the housing  3 , this opening is closed off on one side with a stopper  11  and forms a first pressure chamber  13  with this stopper  11  in the opening  9 , which takes the form of a stepped opening there is a flow regulator piston  15 , which is positioned to be adjustable against the force of an elastic element which takes the form of a screw spring  17 . The flow regulator piston  15  is pierced by a opening, which preferably runs concentric to the outer diameter of the flow regulator piston  15  and forms an opening  19 . This has a first baffle, specifically a measuring baffle  21 , the flow diameter of which is less than that of the opening  19 . This baffle, which acts as a first hydraulic resistor  21 ′ determines the consumer oil flow and is integrated into the flow regulator piston  15  in the preferred embodiment.  
         [0028]    At the opposite end of the opening  9  to the stopper  11  is a pressure connection  23  which leads to a consumer which is not shown here.  
         [0029]    At the opposite end of the housing  3  to the pressure connection  23  is a suction connection  25 .  
         [0030]    The representation in FIG. 1 also shows a shaft stump  27 , via which the drive moment can be transferred to a pump unit in the housing  3 . The shaft stump  27  is here on the side of the pressure connection  23 , in order to guarantee both in extremely compact construction of the pump and secure pressure seal towards the outside. The flow regulator piston  15  divides the first pressure chamber  13  from a second pressure chamber  29  the diameter of which is here only smaller than the diameter of the first chamber  13  as an example. The second pressure chamber  23  is closed on one side by a annulus surface  31  of the pressure regulator piston  15  which faces away from the first pressure chamber  13  and on the other side by a shoulder  33 , which is formed by a step in the opening  9  and forms a transition to a third pressure chamber  35 , which is sealed by an extension  37  of the flow regulator piston  15  opposite the second pressure chamber  29  and is connected to the first pressure chamber  13  via the opening  19 .  
         [0031]    The first pressure chamber  13 , which lies between the stopper  11  and the flow regulator piston  15 , is sealed off from the opening  19  when the flow regulator piston is in the functional position shown in FIG. 1. This is because the stopper  11  preferably has a projection  41  which runs concentric to the central axis  39  of the opening  9  and seals the mouth of the opening  19  or its measuring baffle  21  if the pressure regulator valve  15  is forced to the right by the force of the screw spring  17  and hits the projection  41 . It would also be possible to plan a different impact which would not have a sealing function.  
         [0032]    A pressure p 0  in the first pressure chamber  13  is exerted on the right front side  43  of the flow regulator piston  15  The surface of the front side  43 , which is effective hydraulically, is largely formed from the cross-section surface of the flow regulator piston  15  minus the flow cross section of the measuring baffle  21 . The pressure p 1  in the third pressure chamber  35  is exerted on a stepped, proposed ring surface  45  of the flow regulator piston  15  which runs vertically to the central axis  39  of the flow regulator piston and is limited by the outer diameter of the pressure chamber  35  and the outer edge or outer diameter of the measuring baffle  21 . Parts of the ring surface  45  are formed by the ring surfaces  45 ,  45 ″ and  45 ′″. The pressure p 2  in the second pressure chamber  29  is exerted from the left onto the annulus surface  31 , the width of which, measured in a radial direction to the central axis  39 , corresponds to the width of the shoulder  33 , measured in a radial direction, and is determined by the difference in the radii of the opening  9  in the area of the second pressure chamber  29  and in the area of the third pressure chamber  35 . The annulus surface  31  would preferably be about the same size as the proposed stepped ring surface  45 . However, it is possible to vary the relationship between the two surfaces (annulus surface  31  and ring surface  15 ). This makes it possible to influence, for example, the vibration absorption of the flow regulator valve  5 . In addition, it can also vary the behaviour of the pressure regulation. The annulus surface  31  and the ring surface  45  form a resulting surface, which should preferably be exactly the same size as the front side  43  However, it is also possible to make the resulting surface and the front side different sizes. This means that the system pressure can be adjusted depending on the amount to be regulated.  
         [0033]    [0033]FIG. 1 shows that the second pressure chamber  29  takes the form of a ring chamber which is concentric to the opening  19  and that the extension  37  of the flow regulating piston  15  separates the second pressure chamber  29  from the opening  19  hydraulically, whatever functional position the flow regulator piston  15  is in. In the wall of the extension  37 , there is at least one opening, which preferably runs radial to the central axis  39  and acts as a baffle  47 , i.e. as a second hydraulic resistor. This is therefore integrated into the flow regulator piston  15 , so that the flow regulator valve is very compact in construction.  
         [0034]    Therefore the second pressure chamber  29  is connected to the opening  19  hydraulically via the second baffle  47 , the diameter of which is considerably less than that of the measuring baffle  21 . The second baffle  47  comes after the measuring baffle  21 —looking from the first pressure chamber  13 .  
         [0035]    The first pressure chamber  13  is impacted with the medium supplied from the pump unit. This passes via the measuring baffle  21  and the opening  19  to the third pressure chamber  35  and the pressure connection  23 .  
         [0036]    There is a fluid connection leading from the second pressure chamber  29  to a pressure chamber  51  in the pressure regulator valve  7  which is selected by a valve body  55  impacted by the force of a screw spring  53 . If the valve body  55  shifts to the left from the position shown in FIG. 1, a fluid connection from the pressure chamber  51  to a lower pressure level, for example to a tank, is released.  
         [0037]    The basic functionality of a flow regulator valve and a pressure limiting valve is known, therefore it is not detailed here. It must only be stated that the flow regulator valve  5  serves to regulate the flow volume supplied by the pump unit via tho pressure connection  23  to the consumer to a pre-set value where possible. The pressure limiting valve  7  serves to limit the maximum pressure with the pump. Maximum pressure can be reached when, for example, the fluid connection to the consumer is broken.  
         [0038]    [0038]FIG. 2 a  shows a longitudinal section of the pump shown in FIG. 1 The same parts are given the same numbers, therefore there is no need to describe them further, as the explanation of FIG. 1 can be referred to  
         [0039]    The pump unit  57  mentioned above can be seen in FIG. 2 a.  Its construction is of no importance for the fitting and arrangement of the flow regulator valve  5  and the pressure limiting valve  7  Here, for example, a wing cell pump is shown which is driven by a shaft  59 , to the shaft stump  27  of which can be attached a belt pulley  61  or something similar, in order to transfer a drive moment to the pump  1 . The shaft is positioned in the housing  3  of the pump  1  using a special bearing  63  The free end of the shaft meshes with a rotor  65 , which has slots which run in a radial direction to a turning axis  67  of the shaft  59 , these slots have radially adjustable wings  69  The rotor  65  turns within a stroke ring  71  which has an inner surface which is almost elliptical and which the outer edges of the wings  69  slide against when the rotor  65  turns, forming part chambers of different volumes and therefore suction and pressure chambers.  
         [0040]    To the right and left of the rotor  65 , there are pressure plates  73  and  75  which seal the suction and pressure areas and which are pressed together with a spring  77 . This comes into contact with a cold start plate  79  which lies on a surface of the pressure plate  75  which faces away from the rotor and forces the cold start plate against the pressure plate  75 .  
         [0041]    The function of a wing cell pump is basically known, therefore it is not detailed here.  
         [0042]    The pump unit  57  sucks the medium to be pumped, for example hydraulic oil, via a tank connection  80 —which has a fluid connection to the suction connection  25  and which is located close to the central axis of the pressure limiting valve  7  (FIG. 1)—and via a suction chamber  81  into a fourth pressure chamber  83 , which passes into the first pressure chamber via a special fluid connection. For production reasons, this fluid connection is formed by openings  85  and  87 , which run largely parallel to one another and cut another. Alternatively, the openings  85  and  87  can run towards one another at an obtuse angle In this case it is important that the two openings  85  and  87  cut each other in such a way that a medium connection is made which allows the hydraulic oil pumped by the pump  1  to flow practically unhindered Therefore a medium connection is made which largely has the same flow cross-section as openings  85  and  87   
         [0043]    Here, the housing  3  is made up two parts, a basis body  3 ′ and a cover  3 ″ which includes the bearing  63  The basic body  3 ′ contains a hollow  89  which houses the pump unit  57 . The first opening  85  can be inserted in the basic body  3 ′ using the hollow  89 , the second opening  87  using opening  9 , if stopper  11  has not yet been set. This means that both openings  85  and  87  can be inserted into the housing  3  of the pump  1  in such a way that separate sealing stoppers are not required. A compact fluid connection between the fourth pressure chamber  83  and the first pressure chamber  13  can then be made easily  
         [0044]    From FIG. 2 a  it can be seen that the flow regulator valve  5  is arranged in a fluid path, on one side of which is the inflow of the medium pumped by the pump  1  and on the other side or which is the pressure connection  25  for the consumer In between the two is the outlet through which the medium can flow out if the pressure regulator valve  5  is activated.  
         [0045]    In FIG. 2 a,  there is, for example, a continuation  91  is marked which emerges from the projection  41  of the stopper  11 , goes through the measuring baffle  21  and has a variable outer diameter. If the flow regulator piston  15  moves position, the measuring baffle  21  is made tighter to a greater or lesser degree by the continuation  91 , depending on its outer diameter, so that variable courses of the volume flow pumped can be achieved via the revolutions n of the pump  57  Continuations of the type discussed here are well known, therefore are not detailed further  
         [0046]    In the representation shown in FIG. 2 a , the flow regulator piston  15  has shifted from the its initial position, shown in FIG. 1, against the force of the screw spring  17  to the left, so that its front side  43  is arranged at a distance from the projection  41 . In the functional position of the pressure regulating piston  14  of the pressure regulating valve  5  shown in FIG. 2 a , there is a fluid connection from the fourth pressure chamber  83  to the third pressure chamber  35 , and therefore to the pressure connection  23 , via the openings  85  and  87 , the first pressure chamber  13 , the measuring baffle  21  and the opening  19 . There is also a fluid connection between the opening  19  and the second pressure chamber  29  via the second baffle  47 .  
         [0047]    [0047]FIG. 2 b  shows a section of an embodiment of a pump  1  which has been modified from that shown in FIG. 1 in the area of the flow regulator valve  5  Where they are shown, the same parts are given the same numbers as in FIG. 1, and a description of these parts is not necessary. It can be seen that a opening  9 , which takes the form of a stepped opening, has a shoulder  33   a,  which is formed by another step in the opening  9 . The flow regulator piston  15  has a ring step  15   a  on that an area with a larger diameter of the flow regulator piston  15  is introduced to an area greater than the opening  9  in diameter and an area with a smaller diameter of the flow regulator piston to an area smaller in diameter than opening  9 . This staggering means that the annulus surface  31  is reduced in size compared to the embodiment shown in FIG. 1. This means that the resulting surface with the ring surface  45  (FIG. 1) and the annulus surface shown in FIG. 2 b  are smaller. This makes this resulting surface smaller than the front surface  43 . The system pressure p 0  is exerted on the difference area between the two surfaces (resulting surface and front surface  43 ). As already described in conjunction with FIG. 1, the amount regulated can be adjusted according to the system pressure, depending on the size of the difference area This means that the beginning of the regulation can be varied using the size of the difference area.  
         [0048]    There is, a pressure in the suction area  81  and the outlet opening  97  which is exerted on one surface  15   b  of the ring stage  15   a,  but this pressure is low relative to the system pressure p 0 . This pressure generates a force which is exerted to the right in FIG. 2 b,  and works against the force generated by the system pressure p 0  and represents an error value which does not, however, affect the regulator function of the flow regulator piston  15  significantly.  
         [0049]    The way that the pump  1  and the flow regulator valve  7  function can be seen in the main connections diagram shown in FIG. 5 a . Parts that have been explained for FIGS. 1 and 2 are given the same number here For these the descriptions of FIGS. 1 and 2 should be referred to.  
         [0050]    The pump unit  57  of the pump  1 , which is marked by a square of dashed lines, is driven by the shaft  59  The valve unit  3  is surrounded by dashed lines. A medium, for example hydraulic oil, is introduced into the pump unit from a tank  93  via a pipe L 1  and, from here, supplied to the pressure connection  23  via a pipe L 2 . The flow volume is labelled Q, the pressure supplied p.  
         [0051]    In pipe L 2  is a measuring baffle  21 . Before the measuring baffle, a pipe L 3  branches off from the pipe L 2 . This leads the pressure in the pipe L 2  before the measuring baffle to the right hand side  43  of the flow regulator piston  15 . In the position shown in FIG. 3 a , which corresponds to the position shown in FIG. 1, a connection pipe L 4 , which branches off from the pipe L 3  and leads to pipe L 1  via the flow regulator piston  15 , is broken off. Before the measuring baffle  21 , a pipe L 5  branches off from pipe L 2 , which leads to the left side of the flow regulator piston  15  of the flow regulator valve and is impacted with the pressure p 1  which is in the third pressure chamber  35  and exerted on the left ring surface of the flow regulator piston  15  Another pipe L 6  branches off from L 2  and leads to the left side of the flow regulator piston  154  via the second baffle  47 . In the section of the pipe L 6 ′ after the baffle  47 , there is the pressure p 2 , which is exerted on the annulus surface  31  In FIG. 3 a,  the screw spring  17  is also shown, which also exerts force from the left onto the flow regulator piston  15  of the flow regulator valve  5   
         [0052]    After the baffle  47 , a pipe L 7  branches off from the section of pipe L 6 ′ which leads to the tank  93  via the pressure limiting valve. The basic connection diagram shown in FIG. 3 a  shows the valve body  55  of the pressure limiting valve  7  which seals the pipe L 7  when in the position shown in FIG. 3 and is impacted from one side by the force of a screw spring  53  and on the other side by the pressure in the pipe L 7  via a control or return pipe L 8   
         [0053]    The following goes into the flow regulation function of the flow regulator valve  5  in more detail.  
         [0054]    The flow volume Q which is pumped from the pump unit  57  to the pressure connection  23  via the pipe L 2 , flows through the measuring baffle  21 . Here it encounters a reduction in pressure The pressure p 0  before the measuring baffle  21  is also present in the first pressure chamber. It is exerted, via the pipe L 3 , on the wopening right hand side  43  of the flow regulator piston  15  of the flow regulator valve  5 . It exerts a force to the left in FIGS.  1  to  3   a.  The pressure in pipe L 2  after the measuring baffle  21  corresponds to the pressure p 1  in the opening  19  and in the third pressure chamber  35  or at the pressure connection  28 . This pressure p 1  is exerted on the left ring surface  45  of the flow regulator piston  15  of the flow regulator valve  5 , the overall surface of which is less than that of the front surface  45 .  
         [0055]    The pressure in the pipe L 2  after the measuring baffle  21  is also exerted on the left annulus surface  31  via the pipe L 6 , the pipe section L 6 ′ and the second baffle  47 . This pressure p 1  produces a force which is exerted towards the right on the flow regulator piston  15  of the pressure regulator valve  5 . The ring surface  45  and the annulus surface  31  together should preferably be exactly the same size as the front side  43  of the flow regulator piston  15 . Therefore there is an equilibrium of forces between the force of the pressure on the right side of the flow regulator piston  15  and the sum of the two pressure forces which are exerted on the left side of the piston, i.e. on the annulus surface  31  and on the ring surface  15 , and of the force of the screw spring  17 .  
         [0056]    The difference in force caused by a difference between the pressures acting on the right and left sides of the piston is dependent on the flow volume Q pumped by the pump unit  57  If the flow volume Q, and thus the pressure difference (p 0 −p 1 ) increases at the measuring baffle  21 , the pressure regulator piston  15  moves against the force of the screw spring  17  to the left It can be seen from FIG. 2 a , that, if this sort of movement is made, the right front side  43  will end up revealing the mouth of the outlet  93 , which produces a ‘short circuit’ between the first pressure chamber  13 , the suction chamber  81  and the tank connection  80 . The connection which creates the short circuit, which generally serves to charge the pump on the suction side, is marked as pipe L 4  in FIG. 3 a  From this diagram it can also be seen that if the flow regulator piston  15  shifts to the left, the block in the pipe L 4  will end up being removed, creating a hydraulic connection between the pressure and the suction chamber of the pump unit  57 .  
         [0057]    If the flow regulator piston  15  allows hydraulic oil to flow into the suction chamber  81 , the volume of oil flowing through the measuring baffle  21  does not increase further This means that the pressure drop at the measuring baffle  21  does not drop any further, meaning that the pressure difference between the pressure p 0  in the first pressure chamber  13  and the pressure p 1  to the left of the measuring baffle  21  in the opening  19  reaches an almost constant level.  
         [0058]    In this way a pressure balance is achieved which, in conjunction with the screw spring  17 , limits the maximum flow volume of the pump  1 .  
         [0059]    The design of the continuation  91  of the projection  41  which projects into the measuring baffle  21  means that the surface of the resulting measuring baffle  21  can be varied in connection with the opening stroke of the flow regulator piston  15  and therefore the volume regulated can also be adjusted. This allows increasing and decreasing flow volume lines with different courses to be drawn up.  
         [0060]    For the pure flow regulation function of the flow regulator valve  5 , it is important that the pressure limiting valve  7  is closed. Therefore, for this function, no oil flows through out the fluid connection  49  and the pressure limiting valve  7  The pressure p 2  in the second pressure chamber  29 , when stationary, corresponds to the pressure p 1  in the third pressure chamber  35 . The second baffle  47  then generates no difference in pressure between the second pressure chamber  29  and the third pressure chamber  35 . If it is dynamic, i.e. if the control piston is moving regularly, the second baffle  47  acts as an absorption element and influences the vibration behaviour of the flow regulation piston  15   
         [0061]    The following goes into the pressure limiting function of the flow regulator valve  5  in more detail.  
         [0062]    If the operational pressure exceeds the value set be the pressure limiting valve  7 , for example if the pipe leading to the consumer is blocked, the pressure limiting valve  7  opens. This means that the valve body  55  is shifted to the left with the force of the screw spring  53  (see FIG. 1) or is shifted down according to the representation in FIG. 3 a.  This frees a connection to the tank  93  meaning that hydraulic oil can flow from the second pressure chamber  29  to the tank via the fluid connection (see FIG. 1). In the representation shown in FIG. 3 a , the hydraulic oil pumped by the pump unit  57  can flow into the tank  93  via the measuring baffle  21 , the pipe L 2 , the pipe L 6 , the second baffle  47  and the pipe L 7  (which is the same as the fluid connection  49 ) and the open pressure limiting valve  7 . The pass-through diameter of the second baffle  47  is very much smaller than the pass-through diameter of the measuring baffle  21 . Therefore there is a more significant difference in pressure (p 1 −p 2 ) here. Because of the effects of the baffles, there is less pressure at the left annulus surface  31  than at the left ring surface  45  and at the right hand side  43 . The pressure p 0  provided by the pump unit  57 , which is called the system pressure, increases until the pressure drop at the baffle  47  caused by the flow volume flowing out through the pressure limiting valve  7  is so large that the pressure balance, i.e. the force relationship between the forces exerted on the left and right sides of the flow regulator piston  15 , shifts the flow regulator piston  15  to the left and the flow volume from the first pressure chamber  13  is led directly to the suction chamber  81  of the pump unit  57  via the outlet  97   
         [0063]    It has also been proved that, because of the split pressure return surfaces of the flow regulator piston  15 , which are made up of the annulus surface  31  and the ring surface  45 , the flow regulator valve  5 , through the piston  15  of which the regulated oil stream flows, also has a pressure regulating function. Because of the pressure limiting valve  7 , an equally low volume of oil must flow through the second baffle  47 . The resulting difference in pressure shifts the flow regulator piston  15  or opens up a connection between the first pressure chamber  13  and the outlet  97 , this short circuit connection is marked as L 4  in FIG. 3 a  In this function position, a large controlled volume can flow through the flow regulator piston  15 , meaning that the system pressure cannot increase further.  
         [0064]    This all makes it clear that the pump is relatively simple and compact in structure. It is possible to arrange the flow regulator piston parallel to the shaft  59  and have the pressure outlet  23  on the side of the shaft stump  27 . The flow volume provided by the pump  1  flows through the flow regulator valve  5  in a straight line, meaning that the flow paths are short. This is made possible by the fact that the measuring baffle  21  is integrated into the control piston  15 , meaning that the main flow volume Q can pass through the flow regulator valve  15 . In addition, the flow regulator valve  5 , in conjunction with the annulus surface  31 , allows the pressure limiting valve to act as a pilot stage. It is possible to lead the fluid connection between the pressure outlet of the pump unit  57 , i.e. the fourth pressure chamber  83 , and the first pressure chamber  13  through the opening  85  and  87 , which are completely within the housing. This is another factor in the simple, compact construction of the pump  1   
         [0065]    [0065]FIG. 3 b  shows a block connection diagram of a gear system  100 , which would preferable be an automatic gear system. A housing  101  of the gear system  100  is shown in dashed lines, the housing  101  contains both the pump  1  and the valve arrangement  2 . In addition, a control unit  102  is also housed in the housing  101 , this serves to control a consumer V, particularly a revolutions/torque converter  103 . The control unit  102  is connected to the pressure connection  23  of the valve arrangement  2  via a pipe  1 , meaning that the main flow volume Q can be moved on to the converter  103  by the control unit  102 , depending on the status of the control unit  102 . It is particularly planned that the pump  1  and the valve arrangement  2  should be attached to a flange  104 , which can form a part of the housing for the control unit  102 , as shown in FIG. 4. However, the pump  1  or the valve arrangement  2  can also be connected to the control unit  102  via pipes in the gear system housing  101  or via hollow pipes. Parts which are the same as those in FIGS.  1  to  3   b  are given the same number in FIG. 4, therefore explanations are only made in the following where there are differences.  
         [0066]    There is a clutch mechanism  105  at the pressure connection  23 , this can take the form of a cylindrical plug  106 . The plug  106  is inserted into a socket  107  located in the flange  104 . The socket  107  is also cylindrical in form and has an internal diameter which is slightly greater than the external diameter of the plug  106 . In the sleeve surface of the plug  106 , there is a circular nut which contains a seal  108 , meaning that working medium flowing out of the pressure connection  23  cannot flow over the socket  107 . Of course there can also be a seal on the internal walls of the socket  107 . The clutch mechanism  105 , or the plug  106 , is hollow in form so that a supply channel  109  with its mouth in a channel  110  can be realised, this leads to the control unit  102  of the gear system  100   
         [0067]    The housing  3  of the pump  1  also has a continuation  111  with a seat  111 ′, through which the shaft  59  for the pump unit  57  runs. The continuation  111  and the seat  111 ′ are preferably cylindrical in form and run through a gap  112  of an appropriate cross-section in the flange  104 . The continuation  111  and the clutch mechanism  105  allow the pump  1  or the valve arrangement  2  to be positioned exactly relative to the flange  104 . They also form security against twisting.  
         [0068]    As the valve arrangement  2  is directly adjacent to the pump, the pipe sections between the pressure chamber  83  (FIG. 2 a ) and the first pressure chamber  12  of the valve arrangement  2  are shorter In addition, the outlet opening  97  is relatively short meaning that the hydraulic oil contained in the outlet opening  97  can better be used to charge the pump  1 . Also, the relatively short pipes between the pump  1  and valve arrangement  2  mean that there is little hydraulic resistance and high flow volumes cans be used to charge the pump  1  with low loss levels.  
         [0069]    Instead of the valve arrangement  2 , the pump  1  can, for example, be allocated a separate flow regulator valve to limit the flow volume Additionally or alternatively, a pressure limiting or safety valve and/or a main pressure valve to modulate the pressure of the main flow volume Q can be used. What is decisive is that—irrespective of the valve types used—there are short pipes between the pump and the valve or valve arrangement, so that high flow volumes can be supplied with low loss levels and the oil flowing in the outlet opening  7  can be used to charge the pump  1  better  
         [0070]    The pump  1  is specifically designed to be used in a gear system as a wing cell pump or roller cell pump. Pumps of this type are generally know, therefore known parts are not detailed further here.  
         [0071]    The pump  1  has a stroke ring  71 , on the inside of this there is a rotor  65  (FIG. 2 a ). The rotor houses the wings in wing cell pumps and the rollers in roller cell pumps, these slide alone the inside  113  of the stroke ring  71 . What are known as pressure plates can be allocated to the side surfaces of the stroke ring  71 , forming a pump chamber  114 . Suction pockets which are known in themselves, can be housed in the pressure plates, the working medium can be sucked through a suction channel in these from a tank when the rotor is turning.  
         [0072]    In the stroke ring  71  there are two hollows  115  opposite one another which are allocated to a suction pocket and therefore to the suction chamber of the pump. The hollows  115  mean that the cross section of the suction channel in question is increased, improving the known injector effect of the pump. In addition, the hollows  115  reduce the suction resistance of the pump. There is also a relatively large amount of air in the working medium in gear system pumps, so the increased cross section of the suction channel means that sufficient oil or the required amount of the working medium can be pumped through anyway.  
         [0073]    Preferably each side surface  116  or  117  of the stroke ring  71  (FIG. 6) should have two hollows  115  for two-stroke pumps, although in FIG. 6 the position of the section line means that only the bottom hollows  115  are shown. The sides of each hollow  115  are open relative to the side surface  116  or  117  allocated to it and has an indentation  118  and lateral walls  119 .  
         [0074]    According to FIG. 7, the hollows  115  have a passage  120  and  121  between the indentation  118  and the lateral walls  119  it has proved particularly advantageous it the passage  120  has a rounded section  123  in what is known as the large circle area  122  of the stroke ring  71 , the radius of this rounded section R 1  is between 0.6 mm and 0.8 mm It has proved to be particularly advantageous if the radius is 0.7 mm, as the notching effect in the passage  120  is low. The rounded section  123  adjoins the wall  119 , and is adjoined by an area B which goes down to the indentation  118 . It is particularly planned that there is also a rounded section in the area B, the radius R 2  of which can be about 17 mm. The area B adjoins the indentation  118  of the hollow  115  Therefore it is possible that—going from the indentation  118  in the direction of a limiting wall  119 —there are two cut-out sections, where the first cut-out section A continually increases over the area B, and then passes into a second cut-out section in the rounded section  123  with the radius R 1 , which then passes into the limiting wall  119  in the passage  120 . The cut-out section A can either have a radius R 2  in the area B or can go up in a straight line.  
         [0075]    In the preferred embodiment, the other passage  121  between the limiting wall  119  and the indentation  118  has a radius R 3  which is preferably 1 mm. This passage  121  is located in what is known as small circle area  124  of the stroke ring  71 .