Abstract:
The invention relates to a PTO brake control system. There is a need for an improved and safe PTO brake control system. A PTO may be put into a driven and a non-driven condition an is braked by a PTO brake. A PTO brake control system includes a vehicle speed sensor and an ECU for controlling the PTO brake. The ECU deactivates the PTO brake when the vehicle is stationary and the PTO is not driven. This allows the PTO to be manually rotated to facilitate coupling of the PTO to an implement.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a control system for controlling a power take-off (PTO) brake of agricultural vehicle. 
       BACKGROUND OF THE INVENTION 
       [0002]    Agricultural vehicles, such as tractors or agricultural draft vehicles, which have a PTO transmission or a PTO for driving mounted or towed working equipment are conventionally equipped with PTO brakes which are intended to prevent unintentional rotation of the PTO, for example by the PTO drive itself or by the working equipment. For example, when the vehicle is stationary with the engine running and a PTO speed pre-selected, the PTO is switched off, or put into a non-driven condition. At the same time, the PTO brake is activated. When the PTO is switched on again, the PTO brake is disconnected or deactivated. 
         [0003]    Conventionally, a PTO speed is pre-selected. Although it is possible to set a neutral position for the PTO or to put the PTO speed to “neutral”, it is often the case that a operator forgets to do this, and so the PTO brake is activated when the operator leaves the driver&#39;s cab of the vehicle while the engine is running, for example to hook up working equipment and connect it to the PTO. In this case, it is not usually possible to insert the PTO when the working equipment is hooked up, because the PTO or a PTO journal cannot be manually rotated in order to put it in a suitable insertion position with the PTO brake activated. To insert the PTO, the operator must first switch the PTO speed to “neutral” again, inside the vehicle, so that the PTO is deactivated. This can be awkward and unproductive, because the devices mounted are becoming heavier and heavier, and because this disrupts and interrupts hooking up operation. 
       SUMMARY OF THE INVENTION 
       [0004]    Accordingly, an object of this invention is to provide an improved PTO control system. 
         [0005]    This and other objects are achieved by the present invention, wherein a PTO control system operates so that when the vehicle is stationary and the PTO is not driven, the PTO brake is deactivated, with the result that the PTO can be rotated manually in the non-driven condition and when the vehicle is stationary. As soon as the operator leaves the vehicle cab, with the vehicle stationary and preferably with the engine running, in order to hook up working equipment, the PTO brake is automatically deactivated by the electronic control unit (ECU), with the ECU detecting vehicle motion (such as with an engine speed sensor or a drive line rotational speed sensor) with the engine running. Corresponding control signals from these or other sensors which sense or detect a vehicle condition of this kind are used by the ECU to generate the appropriate switching signals for the PTO brake. 
         [0006]    Preferably, a further sensor senses the PTO angle of rotation when the vehicle is stationary and the PTO is not driven and the PTO brake is deactivated, with the ECU activating the PTO brake when a pre-settable value of the angle of rotation is reached. If, for example, the PTO is manually rotated beyond a certain angle of rotation, this is interpreted as a misuse and the PTO brake is reactivated. This prevents the PTO from rotating beyond a permitted angle of rotation when the vehicle is stationary and preferably with the engine running, when it is rotated for example by the PTO gear or any incorrect switching in the vehicle or for any other uncontrolled reasons. This permitted angle of rotation may be freely selected, depending on the PTO journal or the number of teeth of the PTO (e.g. six teeth around the periphery). For example, manual rotation of the PTO about an angle of rotation of 60° would be sufficient, with six teeth around the periphery, to reach a usable insertion position for the PTO or the PTO journal when the operator hooks up working equipment by inserting the PTO. 
         [0007]    The ECU also may operate to activate the PTO brake once a pre-settable time since the PTO has been deactivated has elapsed. This ensures that the PTO would be locked again automatically as soon as a time period is exceeded, with the result that, if working equipment is hooked up unintentionally and the vehicle is left with the engine running by the operator, there is the safety function that deactivation of the PTO brake is cancelled again after a brief (pre-settable) period and the PTO is braked actively again by the PTO brake. To operate the working equipment once hooking up or mounting is complete and the PTO has been inserted, it may be provided that, as soon as the PTO is switched on from the driver&#39;s cab or from a switch mounted outside the driver&#39;s cab, a PTO speed must be selected using a further switch arranged in the driver&#39;s cab or outside the driver&#39;s cab first. 
         [0008]    Furthermore, the control system may include an operator presence sensor, and the ECU may be programmed to deactivate the PTO brake depending upon this sensor. Preferably, the PTO brake is not deactivated at the outset if the sensor signals that the driver has not left the driver&#39;s cab. This provides a safety function, with the result that, for example, misuse by a driver in cab is prevented if mounting work is carried out near the PTO by a second person. 
         [0009]    The ECU activates the PTO brake when the vehicle is in motion and the PTO is in a non-driven condition, and deactivates the PTO brake when the vehicle is stationary and the PTO is in a non-driven condition. The ECU controls the PTO brake in response to sensors for vehicle speed, engine speed and PTO rotational speed, and generates control signals for the PTO brake. 
         [0010]    The ECU may also operate to activate the PTO brake, if, with the vehicle stationary and the PTO brake deactivated, a predetermined angle of rotation of the PTO is reached. This prevents misuse or the PTO rotating in an uncontrolled or undesirable manner. Thus, beyond a certain predetermined angle of rotation, the PTO brake is activated automatically and the PTO is locked again. Typically, it is sufficient for the PTO to be rotatable about only a fraction of a revolution in order to couple it to a working implement. It is sufficient merely to overcome a difference in the alignment between the teeth of the PTO and the gaps in the teeth of the implement, so that the teeth are aligned with the gaps on insertion. With a PTO shaft with six teeth, this is possible with a maximum angle of rotation of 60°. With a larger number, the angle of rotation would be even smaller. Thus, for example, a maximum size of 60° for the angle of rotation at the PTO with the PTO deactivated and with the vehicle stationary with the engine running is typically sufficient. 
         [0011]    Furthermore, the ECU can also operate to activate the PTO brake if a predetermined time is exceeded when the vehicle is stationary and the PTO brake is deactivated. Thus, for safety reasons the PTO brake is only deactivated for a specific, pre-settable length of time. As soon as this time period expires, the PTO brake is reactivated. Moreover, the ECU can also operate so that, as soon as the PTO is switched on from the cab (or from a switch mounted outside the cab) a PTO speed must first be pre-selected before the working equipment can be put in operation. 
         [0012]    The ECU can also prevent deactivation of the PTO brake at the outset if a sensor signals that the driver has not left the cab. This ensures that no one, neither driver nor assistant, is inside the cab could cause the PTO to rotate by an erroneous actuations of a switch performed from the driver&#39;s cab while work, settings or mounting are being carried out near the PTO. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a diagrammatic side view of an agricultural vehicle; 
           [0014]      FIG. 2  is schematic diagram of a PTO control system for the vehicle of  FIG. 1 ; and 
           [0015]      FIGS. 3A and 3B  are a logic flow diagram of an algorithm executed by the ECU of  FIG. 2 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    In  FIG. 1 , an agricultural vehicle  10 , such as an agricultural draft vehicle or tractor, includes a frame  12  which is carried by a front axle  16 , connected to front wheels  14 , and a rear axle  20 , connected to rear wheels  18 . The vehicle  10  further includes a body  22  which is set on the frame  12  and has a driver&#39;s cab  24  and an engine bonnet  26 . 
         [0017]    Referring now to  FIG. 2 , the vehicle  10  also includes a drive motor  28 , a drive clutch  30 , a transmission  32 , drive components  34 , a PTO clutch  36 , a PTO transmission  38 , a PTO brake  40  and a PTO  42 . The drive clutch  30  is between the transmission  32  and the drive motor  28 . The drive components  34  branch off from the transmission  32 . The term “drive components” is intended to include the drive shafts, terminal gears and the other drive components (not shown) which drive the wheels  14 ,  18 . 
         [0018]    The PTO line includes the PTO clutch  36 , the PTO transmission  38 , the PTO brake  40  and the PTO  42 , and branches off from the transmission  32 , with the PTO clutch  36  being arranged between the transmission  32  and the PTO transmission  38 , and the PTO brake  40  being arranged downstream in the direction of drive behind the PTO transmission  38 , between the PTO brake  38  and the PTO  42 . The PTO transmission  38  may be an integrated gear branch of the transmission  32 , and/or the PTO clutch  36  may be arranged downstream in the direction of drive, behind the PTO transmission  38 , in which case the PTO brake  40  is arranged between the PTO clutch  36  and the PTO  42 . 
         [0019]    The PTO clutch  36 , the PTO transmission  38  and the PTO brake  40  are controlled by an ECU  44 . Alternatively, the PTO clutch  36  and the PTO transmission  38  may be controlled by a separate switching means or control means (not shown) arranged in the driver&#39;s cab  24 . 
         [0020]    A rotational speed sensor  46  senses the engine speed, a speed sensor  48  and a rotational speed sensor  50  senses the PTO speed, and are connected to the ECU  44 . 
         [0021]    Switching or control means  54  are arranged in the driver&#39;s cab  24 , and are used by a vehicle driver or operator to generate operator command signals, for example to switch the PTO on and off or to pre-select a PTO speed, and to predetermine other variables relevant to the control. 
         [0022]    The ECU  44  receives signals from the sensors  46 ,  48 ,  50  and uses them to generate control signals for the PTO brake  40 . The ECU is programmed with a control algorithm stored in the ECU  44  so that when the vehicle  10  is stationary (when the speed sensor  48  signals a speed of zero) and when the drive motor  28  is running (when the rotational speed sensor  46  signals a speed greater than zero), the PTO brake  40  is disconnected or deactivated. The control signal for the PTO brake  40  may also depend on the signal from an operator presence sensor  58  positioned at a driver&#39;s seat  56  in the cab  24 . If the sensor  58  signals that a driver has not left the driver&#39;s seat  56 , and therefore has presumably not left the driver&#39;s cab either, no deactivation of the PTO brake  40  is performed. The sensor  58  may be a simple contact switch or contact sensor, or a pressure sensor or a light barrier. 
         [0023]    The ECU  44  operates to activate the PTO brake  40  when the vehicle  10  is moving and the PTO  42  is in a non-driven condition. Furthermore, the ECU is programmed to deactivate the PTO brake  40  when the vehicle  10  is stationary and the PTO  42  is disengaged. The ECU  44  detects and responds to a disengaged PTO  42  when the ECU  44  performs a control action on the PTO clutch  36  and receives a corresponding response signal from the PTO clutch  36  or a clutch sensor (not shown). When the PTO brake  40  is deactivated, the operator may rotate the PTO and bring it into alignment with an implement connector. Although the PTO can only be rotated within a pre-settable angular range, the angle of rotation should, however, be sufficient to enable the required mounting work or coupling, insertion or connection work to be carried out. The angle of rotation is preferably detected by the rotational speed sensor  50 . Alternatively, a further sensor (not shown) may be provided which offers higher resolution and detects the precise angle of rotation of the PTO  42  within a revolution. As soon as a pre-set angle of rotation is exceeded, the PTO brake  40  is activated again to prevent misuse, although this restriction is optional. The angle of rotation may be pre-set by the switching or control means  54  in the cab  24 , or it could be pre-set by the ECU  44 . 
         [0024]    Preferably, the PTO brake  40  is deactivated only within a predeterminable period, so that the driver must respond and manually rotate the PTO within this period. In this case the ECU is programmed so that the PTO brake  40  is activated as soon as this period is exceeded. This period may also be pre-set by a switching or control means  54  in the cab  24 , or by the ECU  44 . 
         [0025]    The ECU  44  executes an algorithm  300  represented by  FIGS. 3A and 3B . The algorithm begins at step  302  in response to the operator switching an Auto_Neutral switch (not shown) to its ON position. Then in steps  304 - 312  the algorithm checks the following conditions: 
         [0000]    1. Is the Auto_Neutral switch in ON position?
 
2. Is the PTO deactivated by switching the PTO switch (not shown) in OFF position?
 
3. Is the PTO speed equal zero (PTO speed sensor ( 50 ) signalizes 0)?
 
4. Is the wheel speed equal zero (wheel speed sensor ( 48 ) signalizes 0)?
 
5. Is the vehicle transmission ( 32 ) in park position?
 
         [0026]    If all of these conditions 1 to 5 are true then in step  314  the PTO transmission will be automatically switched into neutral due to a “PTO gear_auto_neutral control ON” command, which is sent by the controller ( 44 ), and the PTO clutch will be opened (disabled). 
         [0027]    Otherwise, if one of the above conditions is not true, the automatic switching of the PTO gear into neutral position will not take place and the normal PTO operation mode takes place by closing the PTO clutch (PTO clutch enabled) at step  328 . 
         [0028]    If the automatic switching of the PTO gear into neutral position takes place, in steps  316 - 320  the ECU  44  checks the following conditions: 
         [0000]    6. Has been the Auto_Neutral switch meanwhile switched into OFF position?
 
7. Has been the PTO meanwhile activated by switching the PTO switch in ON position?
 
8. Is the vehicle transmission  32  not in park position anymore?
 
         [0029]    If one of the conditions 6 to 8 are true then the PTO transmission  38  will be prepared for engagement by starting a timer (wind up timer) in step  322 , while in step  324  the ECU  44  sends a “PTO gear_auto_neutral control OFF” command, but not enabling the PTO clutch  36  yet (the clutch is still disabled). Due to a decrementation of a counter the timer will count down until the timer elapsed. When the timer elapsed (step  326 ) the normal PTO operation mode takes place and the clutch  36  will be enabled (step  328 ). 
         [0030]    During the normal PTO operation mode steps  330 - 338  check conditions 1-5 again. If all of the conditions 1 to 5 are true then in steps  340 - 344  operate so that the PTO transmission  38  will be prepared for automatically switching into neutral position by starting a timer (wind up timer), while the controller is still sending a “PTO gear_auto_neutral control OFF” command and the PTO clutch ( 36 ) keeping enabled. Due to the decrementation of a counter the timer will count down until the timer elapsed. 
         [0031]    During decrementation of the timer steps  346 - 354  check the following conditions: 
         [0000]    9. Is the Auto_Neutral switch in OFF position?
 
10. Is the PTO activated by switching the PTO switch in ON position?
 
11. Is the PTO speed greater then zero (PTO speed sensor ( 50 ) signalizes&gt;0)?
 
12. Is the wheel speed greater then zero (wheel speed sensor ( 48 ) signalizes&gt;0)?
 
13. Is the vehicle transmission  32  not in park position?
 
         [0032]    When one of the conditions 9-13 is true, then the ECU  44  keeps the normal PTO operation mode by starting a new cycle with checking again conditions 1-55 (steps  328 - 338 ), start decrementing the timer and checking conditions 9-13 (steps  340 - 354 ). The ECU  44  keeps the normal PTO operation mode until the timer elapsed and all of the conditions 9-13 are not true. 
         [0033]    If the timer elapsed and all of the conditions 9-13 are not true, then in step  342  the PTO transmission  38  will be automatically switched into neutral position due to a “PTO gear_auto_neutral control ON” command sent by the ECU  44  and the PTO clutch will be opened (disabled). Since the ECU  44  is sending a “PTO gear_auto_neutral control ON” command, the ECU  44  follows the procedure as described above when automatic switching of the PTO transmission  38  into neutral takes place. 
         [0034]    While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.