Abstract:
A control device for and a method of controlling a gearbox having a pressure-limiting device connected to a pressure medium source. A first controllable valve device is connected downstream of the pressure-limiting device and an actuating device is connected further downstream and adjusts the gearbox. A second controllable valve device is connected directly to the pressure medium source, via a supply line, and another actuating device is connected downstream of the second controllable valve device. An electric control device is provided for actuating the controllable valve devices and a sensor is connected to the electric control device for measuring pressure of the pressure medium in the supply line. The electric control device is connected to the second controllable valve device such that the second controllable valve device and the further actuating device are controlled by the pressure of the pressure medium in the supply line.

Description:
This application is a National Stage completion of PCT/EP2007/061844 filed Nov. 5, 2007, which claims priority from German patent application serial no. 10 2006 054 032.8 filed Nov. 16, 2006. 
     FIELD OF THE INVENTION 
     The present invention relates to a control device for a gearbox featuring a pressure medium source, a pressure-limiting device connected to the pressure medium source downstream, at least one first controllable valve device connected downstream to the pressure-limiting device, and at least one actuating device connected downstream to the first controllable valve device, at least one second controllable valve device, which is connected via a supply line directly to the pressure medium source, and at least one further actuating device connected downstream to the second controllable valve device, an electric control device to actuate the first and second controllable valve device, and a sensor device connected to the electric control device to measure the pressure of the pressure medium in the supply line. The present invention further relates to a method of controlling the gearbox. 
     BACKGROUND OF THE INVENTION 
     A device of this type for controlling a gearbox is known from DE 199 31 973 A1. The known control device includes a pressure medium source, which is connected to a pressure limiting valve via a supply line. A first controllable valve device is connected to the pressure limiting valve, and is followed again by an actuating device to adjust the gearbox. The first controllable valve device includes two 3/2-way valves, which on one side are connected to the pressure limiting valve and on the other to the actuating device to adjust the gearbox. The pressure limiting valve as well as the first controllable valve device is actuated as a function of the pressure in the lines between the pressure-limiting valve on the one side and the 3/2-way valves on the other. In order to ascertain this pressure, the indicated document suggests arranging a pressure sensor inside the pressure medium line extending from the pressure-limiting valve to the first controllable valve device. Further, a second controllable valve device is provided, which serves to control a further actuating device. The second controllable valve device is connected directly to the pressure medium source, whereby this is again via the above-mentioned supply line. A further pressure sensor is provided in the supply line and serves to monitor the supply pressure. The pump allocated to the pressure medium source is actuated on the basis of the supply pressure ascertained, so that a constant supply pressure is assured inside the supply lines. 
     SUMMARY OF THE INVENTION 
     Proceeding from this state of the art, the object of the present invention is to create a control device for a gearbox which allows especially simple and assured control or regulation of the further actuating device, whereby the structure of the control device must be especially simple. Further, it is the object of the present invention to provide an especially simple method of controlling a gearbox, which in particular provides assured control and regulation of the further actuating device. 
     The control device, in accordance with the invention, for a gearbox features first of all a pressure medium source. A pressure medium source can be understood, for example, as a pump in combination with a pressure medium storage device. The pressure medium can be air or oil, for example, so that this can be a pneumatic or a hydraulic device. A pressure-limiting device connected to the pressure medium source is provided downstream from the pressure medium. Here and below, downstream means that the pressure medium flows in this direction to an actuating device in order to effect adjustment there. Downstream of the pressure-limiting device is a first controllable valve device, which is connected to the former. The first controllable valve device can comprise several valves, for example. Further, at least one actuating device, connected downstream to the first controllable valve device is provided to adjust the gearbox. The actuating device to adjust the gearbox can be a double-action cylinder, for example, whose pressure chambers are connected to the valves of the first controllable valve device. The control device for a gearbox further features at least one second controllable valve device, which is connected directly to the pressure medium source via a supply line. This means that the second controllable valve device is not downstream of the pressure-limiting device, as is the case with the first controllable valve device. Downstream of the second controllable valve device is a further actuating device, which is connected to the second controllable valve device. The further actuating device can for example be an actuating device of a clutch associated with the gearbox, or an actuating device for a gear brake. Further, an electric control device to actuate the first and second controllable valve device is provided. Further, a sensor device is connected to an electric control device to measure the pressure of the pressure medium in the supply line. In accordance with the invention, the electric control device is actively connected to the second controllable valve device in such a way that the second controllable valve device and thus the further actuating device can be actuated as a function of the pressure of the pressure medium measured in the supply line. 
     Thus in accordance with the invention, the pressure of the pressure medium in the supply line is not only ascertained, but this ascertained pressure is also the basis for control of the second controllable valve device, and hence of the further actuating device. Thus the invention allows better adaptive controllability of the second controllable valve device and hence of the further actuating device. This is especially advantageous when the actuating device is a clutch actuating device and/or a gear brake actuating device. 
     In a preferred embodiment of the control device in accordance with the invention, the actuating device, which is connected to the second controllable valve device, is a clutch actuating device and/or a gear brake actuating device. The first actuating device is thus an actuating device for a clutch associated with the gearbox, and/or an actuating device for a gear brake associated with the gearbox. In the case of a gear brake actuating device, therefore, for the first time good adaptive controllability of the gear brake is also possible. 
     In a further preferred embodiment of the control device in accordance with the invention, a second sensor device connected to the electric control device downstream behind the pressure-limiting device measures the pressure of the pressure medium. The electric control device is actively connected to the first controllable valve device in such a way that the first controllable valve device and hence the actuating device for adjusting the gearbox can be actuated as a function of the measured pressure of the pressure medium behind the pressure-limiting device. The second sensor device to measure the pressure of the pressure medium can again include a pressure sensor, for example, which measures the pressure inside the pressure line between the pressure-limiting device on one side and the actuating device for adjusting the gearbox on the other. 
     In a further preferred embodiment of the control device in accordance with the invention, the pressure-limiting device can be actuated by the electric control device as a function of the pressure of the pressure medium measured behind the pressure-limiting device. Thus the pressure-limiting device can be formed by a pressure limiting valve, for example, which is operated by a pulse-width-modulated signal from the electric control device to produce various pressures behind the pressure-limiting device. 
     In a further preferred embodiment of the control device in accordance with the invention, the pressure-limiting device is a pressure-limiting valve. 
     In an especially preferred embodiment of the control device in accordance with the invention, the further actuating device is a clutch actuating device. A pressure medium feed line is provided between the second controllable valve device and the clutch actuating device. In this embodiment, no check valve is provided inside the pressure medium feed line. Thanks to actuation of the second controllable valve device based on the ascertained pressure medium pressure in the supply line, a check valve can be dispensed with in the pressure medium feed line. Thus, the second controllable valve device can be closed, for example, when a pressure drop is measured in the supply line, so that backflow of the pressure medium into the supply line is prevented even when no control device is provided in the pressure medium feed line. In this way, an especially simple structure of the control device in accordance with the invention is achieved. 
     For the above-mentioned reasons, in an advantageous embodiment of the electric control device in accordance with the invention, the electric control device is actively connected to the second controllable valve device in such a way that the pressure medium cannot flow back from the pressure medium feed line into the supply line when the measured pressure of the pressure medium in the supply line goes below a set minimal value. As already explained above, solely through actuation of the valves of the second controllable valve device, maintenance of pressure inside the pressure medium feed line can be assured without an expensive check valve being required. 
     The method in accordance with the invention for controlling a gearbox includes the method steps indicated below: Preparation of a control device for a gearbox with a pressure medium source, a pressure-limiting device connected downstream to the pressure medium source, at least one first controllable valve device connected downstream to the pressure-limiting device, and at least one actuating device connected downstream to the first controllable valve device to adjust the gearbox, at least one second controllable valve device which is connected, via a supply line, directly to the pressure medium source, and at least one further actuating device connected downstream to the second controllable valve device; measurement of the pressure medium pressure in the supply line and actuation of the second controllable valve device and thus the further actuating device as a function of the measured pressure medium pressure in the supply line. With regard the advantages of the method in accordance with the invention, reference is made to the indicated advantages of the control device in accordance with the invention. 
     In a preferred embodiment of the method in accordance with the invention, the control device for a gearbox features as a further actuating device a clutch actuating device and/or a gear brake actuating device. 
     Further, an especially preferred embodiment of the method in accordance with the invention includes the method steps measurement of the pressure of the pressure medium downstream behind the pressure-limiting device and actuation of the first controllable valve device and thus of the actuating device to adjust the gearbox as a function of the measured pressure of the pressure medium downstream behind the pressure-limiting device. 
     In an advantageous embodiment of the method in accordance with the invention, further, the method step of actuating the pressure-limiting device as a function of the measured pressure of the pressure medium downstream behind the pressure-limiting device is provided. 
     In a further advantageous embodiment of the method in accordance with the invention, further, the method step of actuating the second controllable valve device is conducted in such a way that the pressure medium cannot flow back from the further actuating device into the supply line when the measured pressure of the pressure medium in the supply line goes below a set minimal value. Thus for example, when there is a pressure drop in the supply line, the second controllable valve device can be actuated in such a way that it is closed and thus prevents backflow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention is explained in more detail below with reference to an exemplary embodiment and the associated drawing. The single drawing shows a schematic representation of an embodiment of the control device for a gearbox in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The single drawing shows a schematic representation of an embodiment of the control device  1  for a gearbox in accordance with the invention. The control device  1  features first of all a pressure medium source  2 , which includes both a pressure medium pump  3  and a pressure medium storage device  4 . The pressure medium can be air or oil, for example. The pressure medium pump is connected at its suction end to the pressure medium line  5 , whose end extends into a pressure medium drain  6 . A supply line  7  is connected to the other end of the pressure medium pump  3 , which is also provided with the pressure medium storage device  4 . 
     Downstream of the pressure medium source  2 , a pressure-limiting device  8  is provided, which is connected to the supply line  7  and thus to the pressure medium source  2 . The pressure-limiting device  8  includes in the present example a pressure limiting valve  9 , which is configured as a 2/2-way valve. The pressure limiting valve  9  here has a pressure medium inlet  10 , which is connected to the supply line  7 , and a pressure medium outlet  11 . The control of the pressure limiting valve  9 , which is configured as a magnetic valve, takes place by means of an electromagnet  12  which is connected via a control line  13  to an electric control device  14 , which is explained in more detail below. Downstream of the pressure-limiting device  8 , a first controllable valve device  15  is connected to the pressure-limiting device  8 . For this purpose, a further pressure medium line  16  is connected to the pressure medium outlet  11  of the pressure limiting valve  9 , and then splits into two further pressure medium lines  17  and  18 . 
     The first controllable valve device here includes a first 3/2-way valve  19  and a second 3/2-way valve  20 , whereby the pressure medium line  17  leads to the first 3/2-way valve configured as a magnetic valve, and the pressure medium  18  to the second 3/2-way valve configured as a magnetic valve. The two 3/2-way valves  19  and  20  can again be actuated via an electromagnet  21 ,  22 , which is connected via a control line  22 ,  23  to the electric control device  14 . Each of the two valves  19  and  20  features a pressure medium inlet  24 , which is connected in the case of the valve  19  to the pressure medium line  17 , and in the case of the valve  20  to the pressure medium line  18 . Further, each valve  19 ,  20  features a pressure medium output  25 , which is connected via a compound outlet line  26  to the pressure medium drain  6 . The valves  19 ,  20  further feature a pressure medium outlet  27 , which leads via further pressure medium lines  28  to a downstream actuating device  29 . 
     The actuating device  29  includes a double-action cylinder  30 , in which a movable piston  31  is disposed. A piston rod  32  is coupled to the movable piston  31 , projects from the cylinder  30 , and is thus suited as an actuating element for adjusting the gearbox. The piston  31  divides the interior space inside the cylinder  30  into a first pressure medium chamber  33  and a second pressure medium chamber  34 . Here the first pressure medium chamber  33  is connected, via the pressure medium line  28 , to the pressure medium outlet  27  of the first valve  19 , while the second pressure medium chamber  34  is connected via the pressure medium line  28  to the pressure medium outlet  27  of the second valve  20 . In order to fill or empty the pressure medium chambers  33 ,  34  with pressure medium, only the two valves  19 ,  20  and the pressure limiting valve  9  have to be accordingly actuated by the electric control device  14  via the control lines  13 ,  22 , and  23 . 
     The control device  1  further features a second controllable valve device  35 . The second controllable valve device  35  is connected via the supply line  7  directly to the pressure medium source  2 , that is, the second controllable valve device  35  is not provided downstream of the pressure-limiting device  8 , but is supplied with pressure medium from the supply line  7 . This medium is under pressure corresponding to the supply pressure of the pressure medium source  2 , and is not reduced by the pressure-limiting device. 
     The second controllable valve device  35  includes a first valve  36  and a second valve  37 , whereby both valves are configured as 2/2-way valves and can be activated by means of the electromagnets  38  and  39 . The electromagnets  38 ,  39  are again actuated by means of the control lines  40 ,  41 , which lead to the electric control device  14 . The pressure medium inlet  42  of the first valve  36  is connected directly to the supply line  7 , while the pressure medium outlet  43  of the first valve  36  is connected to a pressure medium feed line  4 . The pressure medium inlet  45  of the second valve  37  is again connected to the pressure medium feed line  44 , whereas the pressure medium outlet  46  of the second valve  37  is connected to the outlet line  26 , which leads to the pressure medium drain  6 . Downstream of the second controllable valve device  35 , a further actuating device  47  is provided, which is connected via the pressure medium feed line  44  to the second controllable valve device  35 . 
     The further actuating device  47  is configured in the present embodiment as an actuating device for a clutch (not shown) or an actuating device for a gear brake (not shown). Preferably, still further actuating devices of this type are provided which then are actuated by the particular further second controllable valve devices. The actuating device  47  features a cylinder  48  in which a piston  49  is guided. Further a piston rod  50  is disposed on the piston  49 , the rod projecting from the cylinder  48  and serving as an actuating element for the clutch or the gear brake. The piston  49  divides the interior space of the cylinder  48  into a chamber  51  and a pressure medium chamber  52 . Here the piston is prestressed by means of a spring  53  in the direction of the pressure medium chamber  52 . The pressure medium feed line  44 , which in the present case removes the pressure medium, empties into the pressure medium chamber  52 . 
     The control device  1  further features a first sensor device  54  for measurement of the pressure medium pressure in the supply line  7 . In the present example, the sensor device  54  comprises a pressure sensor  55 , which is connected, via a measurement line  56 , to the electric control device  14 . Further, a second sensor device to measure the pressure of the pressure medium is provided, which measures the pressure of the pressure medium at the branch point between the pressure medium line  16  on one side, and the pressure medium lines  17  and  18  on the other. The second sensor device  57  again features a pressure sensor  58 , which is connected by means of a measurement line  59  to the electric control device  14 . 
     The electric control device  14  is actively connected, via the control lines  40 ,  41 , to the second controllable valve device  35 , that is, to the first and second valve  36 ,  37 , in such a way that the second controllable valve device  35  and thus the further actuating device  47  can be actuated as a function of the measured pressure medium pressure in the supply line  7 . For example, if the pressure dominating in the supply line  7  should drop below a set minimal value, which could be caused by a leak, for example, this is detected by means of the pressure sensor  55  of the first sensor device  54 , and is transmitted, via the measurement line  56 , to the electric control device  14 . The electric control device  14  can then act, via the control lines  40 ,  41 , on the first and second valve  36 ,  37  of the second controllable valve device  35  in such a way that the valves  36 ,  37  are set in the closed position as indicated in the drawing. With this setting, the pressure medium cannot flow back from the pressure medium chamber  52  of the further actuating device  47  via the pressure medium feed line to the supply line  7  or the outlet line  26 . The pressure in the pressure medium chamber  52  can thus be maintained without the need for a check valve in the pressure feed line, so that such a check valve can be dispensed with in the shown embodiment. 
     Further, the electric control device  14  is actively connected via the control lines  22 ,  23 , to the first controllable valve device  15  such that the latter and thus also the actuating device  29  can be actuated to adjust the gearbox as a function of the pressure of the pressure medium measured by the second sensor device  57 . Also, the pressure-limiting device  8  or its pressure limiting valve  9  can be actuated, via the control line  13 , by the electric control device  14  as a function of the pressure of the pressure medium ascertained by the pressure sensor  58 . Thus for example, the pressure limiting valve  9  can be acted on by a pulse-width-modulated signal from the electric control device so that the pressure of the pressure medium is reduced in the downstream pressure medium line  16  with respect to the supply pressure in the supply line  7 . 
     REFERENCE NUMERALS 
     
         
           1 . Control device 
           2 . Pressure medium source 
           3 . Pressure medium pump 
           4 . Pressure medium storage device 
           5 . Pressure medium line 
           6 . Pressure medium drain 
           7 . Supply line 
           8 . Pressure-limiting device 
           9 . Pressure limiting valve 
           10 . Pressure medium inlet 
           11 . Pressure medium outlet 
           12 . Electromagnet 
           13 . Control line 
           14 . Electric control device 
           15 . First controllable valve device 
           16 . Pressure medium line 
           17 . Pressure medium line 
           18 . Pressure medium line 
           19 . 3/2-way valve 
           20 . 3/2-way valve 
           21 . Electromagnet 
           22 . Control line 
           23 . Control line 
           24 . Pressure medium inlet 
           25 . Pressure medium output 
           26 . Outlet line 
           27 . Pressure medium outlet 
           28 . Pressure medium line 
           29 . Control device to adjust the gearbox 
           30 . Double-action cylinder 
           31 . Piston 
           32 . Piston rod/actuating element 
           33 . First pressure medium chamber 
           34 . Second pressure medium chamber 
           35 . Second controllable valve device 
           36 . First valve 
           37 . Second valve 
           38 . Electromagnet 
           39 . Electromagnet 
           40 . Control line 
           41 . Control line 
           42 . Pressure medium inlet 
           43 . Pressure medium outlet 
           44 . Pressure medium feed line 
           45 . Pressure medium inlet 
           46 . Pressure medium outlet 
           47 . Further actuating device 
           48 . Cylinder 
           49 . Piston 
           50 . Piston rod 
           51 . Chamber 
           52 . Pressure medium chamber 
           53 . Spring 
           54 . First sensor device 
           55 . Pressure sensor 
           56 . Measurement line 
           57 . Second sensor device 
           58 . Pressure sensor 
           59 . Measurement line