Abstract:
For a cement mixer installed on a vehicle, a vehicle controller area network is modified to develop from engine speed, hydraulic power take-off system pressure and programmed data on power take-off pump capacity estimates of rotational speed and barrel rotational count. The network can also maintain a constant barrel rotational speed during transportation.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
       [0001]    The invention relates to the control of hydraulic power take-off systems for motor vehicles and more particularly to application of such control to hydraulic power take systems for a vehicle mounted cement mixer drum. 
       2. Description of the Problem 
       [0002]    Contemporary trucks are often equipped for power takeoff operation (PTO). PTO is used with auxiliary systems such as hoists, lifts, and pumps that are directly or indirectly powered by the vehicle&#39;s engine. Indirectly powered systems, such as hydraulic systems, are among the most popular. Power for an auxiliary hydraulic system is converted from engine output by an engine driven hydraulic pump. The hydraulic pump draws working fluid from a tank and supplies fluid to a hydraulic valve manifold which can divert the working fluid to a cylinder or impeller used to move a target load. 
         [0003]    Original vehicle manufacturers have long supplied general purpose hydraulic pumps with their vehicles which are suitable for supporting hydraulic power take off operation. In the past the provision of controls and hydraulic lines was generally left to after market specialists. Retrofitted controls have sometimes left something to desired in terms of integration of the new wiring and hydraulic lines required. 
         [0004]    Vehicle system integrated hydraulic power take-off systems utilizing modular components and requiring minimum modification of the vehicle have been recently developed as described in U.S. Patent Publication 2005/0206113, which is assigned to the assignee of the present invention and incorporated herein by reference. The Patent Publication teaches a system which includes a hydraulic fluid tank, a hydraulic valve manifold, an engine driven pump, and a switch and instrument panel. The system is suitable for a variety of applications. The control aspects of these systems, which are integrated with a vehicle controller area network (CAN), are of particular interest. These systems include a hydraulic valve controller and an auxiliary gauge and switch controller for connection to the vehicle controller area network and which provide integration of control over hydraulic system operation with vehicle operation. Control protocols are adapted from standard SAE J-1939 bus signals. Other vehicle controllers are monitored for standard signals for implementing interlocks as required and signals relating to engine controller control over the engine are readily invoked. 
         [0005]    Operators of cement mixers need to know the mixer barrel rotation count and the rotational velocity of the mixer barrel to ensure mixing the cement properly. For a cement mixer mounted on a vehicle the rotational velocity of the mixer barrel must be monitored and kept at a constant rate while a charge is transported. Current mixer systems monitor mixer barrel speed using a speed sensor system that is mounted to the barrel. The sensor system requires an additional sensor and a tone ring to implement which raises reliability issues and which add to cost. Rotational velocity information is displayed to the driver/operator who must make the adjustments required to keep the operation within defined limits. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the invention there is provided a vehicle system integrating control of over a power take-off driven, vehicle mounted cement mixer with a vehicle controller network to monitor vehicle operating variables which are used in turn to determine cement mixer barrel rotational speed and barrel rotation count. There is no need to use direct sensing of barrel operation. The system also provides for maintaining barrel rotation at a constant speed during transportation. 
         [0007]    Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a side elevation of a truck with a cement mixer installed for hydraulic power takeoff operation. 
           [0010]      FIG. 2  is a schematic illustration of the hydraulic and electronic control systems used for a hydraulic power take-off vehicle mounted cement mixer. 
           [0011]      FIG. 3  is a front elevation of an application control panel for a cement mixer barrel control system. 
           [0012]      FIG. 4  is a data flow diagram. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring now to the figures and particularly to  FIG. 1 , a truck  100  is depicted having a chassis  120  on which a cement mixer barrel  110  is mounted for rotation. In accordance with the teachings of the invention an integrated hydraulic power take-off system tracks mixer barrel  110  rotation velocity and the number of rotations made by the barrel. 
         [0014]      FIG. 2  illustrates a vehicle hydraulic PTO system  44  and a vehicle electrical control system  10  which are used to monitor and control the cement mixer barrel  110 . Hydraulic PTO system  44  rotates the cement mixer barrel  110  using pressurized oil/hydraulic fluid supplied by a pump  50 . Hydraulic fluid is selectively delivered to a hydraulic motor  48  which turns barrel  110  through a valve pack manifold  34 . Valve pack manifold  34  allows pressurized hydraulic fluid to be delivered to hydraulic motor  48  as part of a circulating hydraulic fluid circuit, hydraulic PTO system  44 , and provides for directional control as well as control over barrel  110  as well as control over the barrel&#39;s rotational speed. Hydraulic fluid circulates through the hydraulic circuit or PTO system  44  from valve pack manifold  34  to return filter  36 , then to a tank or reservoir  30  from which fluid is drawn and pressurized by a pump  50  for return to the valve pack manifold. Valve positions in valve pack manifold  34  are controlled by a valve system controller  40 . The valve system controller/hydraulic electronic control unit  40  includes (or controls) solenoids which physically move the valves in the pack manifold  34 . Valve system controller  40  monitors a number of system operating variables. Controller  40  monitors the hydraulic fluid level (LEVEL) in reservoir  30 , the system oil pressure (P R ) and the temperature (TEMP) from manifold  34 . Return filter  36  condition is indicated by the pressure drop (N) across the filter which is reported by a sensor to valve system controller  40 . The valve system controller  40  is connected to CAN bus  60  for data communication with other vehicle controllers including data relating to the operating system variables. 
         [0015]    Pump  50  is powered by vehicle engine  52  through a mechanical linkage  54  to the engine crankshaft (not shown). PTO operation may be enhanced by utilizing an engine control unit (ECU)  58  which monitors engine operating variables using engine sensors  56 . While engine sensors  56  are illustrated as being direct intermediaries between ECU  58  and engine  52 , related instruments, such as a tachometer, may in fact be connected to the transmission  65 , with the resulting signal provided directly to the ECU or indirectly to the ECU through a transmission controller  64  over controller area network (CAN) bus  60 . Integration of the components is preferably provided by a program resident on and executed by an electrical system controller (ESC)  62  and communicating with other controllers over CAN bus  60 . CAN bus  60  preferably conforms to the SAE J1939 standard. Communication between the valve system controller  40  and an auxiliary gauge and switch package (AGSP)  68  to an operator interface (i.e. panel  18 ) is provided by CAN bus  60 . CAN bus  60  typically provides a physical backbone comprising a twisted pair (either shielded or unshielded) cable operating as a data link or serial data bus. ESC  62  manages the assorted vocational controllers (e.g. valve system controller  40  and ECU  58 ) connected to bus  60  as nodes. Based on data received from the valve pack manifold  34  and passed to the ESC  62 , coupled with knowledge about the capacity of pump  50  (pump  50  typically is an engine driven pump providing 12 gallons per minute flow at 3000 psi at a given engine speed), the ESC  62  can estimate the rotational velocity and rotation count of barrel  110 . 
         [0016]    The SAE J1939 protocol defines a number of messages which may be readily adapted to serve the requirements of a hydraulic PTO system. The auxiliary gauge and switch pack controller  68  allows hydraulic system information to be easily and conveniently displayed to the operator. Since present on the CAN bus  60 , the data can be read by ESC  62 , which uses the data in conjunction with engine speed data form the ECU  58  or transmission controller  64  to calculate rotational speed of and rotation count for barrel  110 . 
         [0017]    Referring now to  FIG. 3 , a control and instrument panel  18  suitable for implementing control over a hydraulic power takeoff operation system and associated vehicle auxiliary system is illustrated. While panel  18  is typically mounted on a vehicle, it may be installed on a radio controlled remote unit. Three gauges are provided including a system pressure gauge  70 , an hydraulic fluid temperature gauge  72  and an hydraulic fluid level gauge  74 . The gauges may incorporate warning lights to draw operator attention to out of norm operating conditions. Six three way rocker switches  76 ,  78 ,  80 ,  82 ,  84  and  86  are also provided, which may be labeled as required for the particular application of the system. In general, the association of the switches with a particular function is implemented in software and labeling of the switches as desired will typically follow. For a cement mixer switch  76  may be an enable switch. Switch  78  may be used for clockwise rotation and switch  80  for counterclockwise rotation. The remaining switches may be reserved for chute positioning. An optional reset button  94  is shown and two counters  90 ,  92  provided indicating current barrel  110  rotation velocity and the rotation count are provided. Each switch may incorporate a light, the operation of which may be programmed to indicate system availability or state of the switch. 
         [0018]      FIG. 4  illustrates the flow of data used to implement the invention. The control algorithm  404  determines barrel speed based on engine speed  402 , hydraulic system operating variables (pump speed) and system parameters  400 , such as pump displacement, which is known. Pump speed may be a linear function in engine speed. Because hydraulic fluid is essentially incompressible barrel speed is locked to flow (displacement X speed) produced by the pump. Barrel speed over time produces a count of barrel rotations. Barrel speed and rotation count are passed as data  406  for display. 
         [0019]    The invention provides improved reliability and reduced cost by elimination of conventional physical sensors used for monitoring barrel operation, and by estimating the required results by indirect means from existing data. 
         [0020]    While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.