US 5,474,147 A · Slip control in a machine for matching hydraulic pump fluid flow to pump driven supplementary front wheel drive motor fluid flow

Abstract

A method is provided for controlling hop in an all wheel drive machine having a torque control lever and a pump for supplying pressurized fluid to wheel motors for effecting all wheel drive. The method includes monitoring machine speed and motor pressure, sensing a first motor pressure fluctuation and subsequent motor pressure fluctuations indicative of a hop, determining desired pump pressure based upon machine speed, and overriding the torque control lever and holding pump pressure constant at desired pump pressure for a preselected time in response to detecting a predetermined number of hops occurring at a predetermined frequency.

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Drawings

Claims20

Dependent claims

A method for controlling slip in a machine having a pump for supplying pressurized fluid to first and second supplementary front wheel drive motors for effecting all wheel drive and having a torque control lever movable between positions of minimum and maximum lever travel for controlling pump pressure, said torque lever position being expressed as a percentage of maximum lever travel, said method comprising the steps of:

monitoring machine speed;
monitoring motor pressure;
searching for a first motor pressure fluctuation and subsequent motor pressure fluctuations indicative of a hop, where a hop is a pressure fluctuation characterized by a difference between a minimum pressure and a maximum pressure of at least a predetermined amount occurring within a predetermined cycle time;
determining desired pump pressure based upon machine speed;
and
overriding the torque control lever and holding pump pressure constant at desired pump pressure for a preselected time in response to detecting a predetermined number of hops occurring at a predetermined frequency.

3 more elements

monitoring ground speed of said machine;
monitoring motor pressure;
searching for a first set of n hops, where n is an integer greater than 2 and a hop is a fluctuation in wheel motor pressure characterized by a difference between a minimum pressure and a maximum pressure of at least a predetermined amount occurring within a predetermined cycle time;
determining whether a predetermined time has elapsed since said first set of n hops was detected;
restarting search for hop 1 if said predetermined time has elapsed since the first set of n hops was detected and resetting a hop counter;
searching for hop 1, if said predetermined time has not elapsed since the first set of n hops was detected, by locating a hop 1 minimum pressure and a hop 1 maximum pressure exceeding the minimum pressure by more than said predetermined amount;
restarting search for hop 1 if hop 1 maximum pressure does not exceed hop 1 minimum pressure by more than said predetermined amount, and resetting the hop counter;
after locating hop 1, searching for subsequent hops, including hop (n-1), hop (n) and hop (n+1) minimum pressure, when said predetermined time has not elapsed since the first set of n hops was detected;
incrementing the hop counter, when hop (n) maximum pressure exceeds hop (n+1) minimum pressure by more than said predetermined amount and hop (n) minimum pressure and hop (n+1) minimum pressure occur at a predetermined frequency;
after incrementing the hop counter, determining a desired pump pressure based upon machine ground speed when the hop counter counts less than 3 sets of hops, and overriding the torque control lever to hold the pump pressure constant at the desired pump pressure for a preselected time before resuming searching for a first hop;
recording a current torque control lever position, expressed as a percentage of torque control lever travel, minus a predetermined amount as a modified torque lever position when the hop counter counts 3 sets of hops, and continuing searching for hops;
resuming searching for hop 1 when the actual torque control lever position is less than said modified torque lever position, and resetting said hop counter;
resuming searching for hop 1 when the actual torque control lever position is not less than said modified torque lever position and the difference between hop maximum pressure and hop minimum pressure is not greater than a predetermined amount, and resetting the hop counter;
and
resuming searching for hop 1 and resetting the hop counter when the actual torque control lever position is not less than said modified torque lever position, the difference between hop maximum pressure and hop minimum pressure is greater than said predetermined amount, and hop frequency is not greater than said predetermined frequency.

12 more elements

A method for controlling slip in a machine having a current driven pump for supplying pressurized fluid to first and second supplementary from wheel drive motors for effecting all wheel drive and having a torque control lever movable between positions of minimum and maximum lever travel for controlling pump pressure, said torque lever position being expressed as a percentage of maximum lever travel, said method comprising the steps of:

monitoring ground speed of said machine;
monitoring motor pressure;
searching for a first set of 3 hops, where a hop is a fluctuation in wheel motor pressure characterized by a difference between a minimum pressure and a maximum pressure of at least 8,000 kPa occurring within a time interval not greater than 1 second;
determining whether 20 seconds has elapsed since said first set of 3 hops was detected;
restarting search for hop 1 if 20 seconds has elapsed since the first set of 3 hops was detected and resetting a hop counter;
searching for hop 1, if 20 seconds has not elapsed since the first set of 3 hops was detected, by locating said hop 1 minimum pressure and hop 1 maximum pressure exceeding the minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 1 maximum pressure does not exceed hop 1 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
searching for hop 2 minimum pressure after locating hop 1 if 20 seconds has not elapsed since the first set of 3 hops was detected and determining whether hop 1 maximum pressure exceeds hop 2 minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 1 maximum pressure does not exceed hop 2 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
restarting search for hop 1 if hop 1 maximum pressure exceeds hop 2 minimum pressure by more than 8,000 kPa and a time lapse greater than 0.5 seconds occurs between hop 1 minimum pressure and hop 2 minimum pressure, and resetting the hop counter;
searching for hop 2 maximum pressure, when hop 1 maximum pressure exceeds hop 2 minimum pressure by more than 8,000 kPa and a time lapse not greater than 0.5 seconds occurs between hop 1 minimum pressure and hop 2 minimum pressure, if 20 seconds has not elapsed since the first set of 3 hops was detected, and determining whether hop 2 maximum pressure exceeds hop 2 minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 2 maximum pressure does not exceed hop 2 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
searching for hop 3 minimum pressure after hop 2 if 20 seconds has not elapsed since the first set of 3 hops was detected and determining whether hop 2 maximum pressure exceeds hop 3 minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 2 maximum pressure does not exceed hop 3 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
restarting search for hop 1 if hop 2 maximum pressure exceeds hop 3 minimum pressure by more than 8,000 kPa and a time lapse greater than 0.5 seconds occurs between hop 2 minimum pressure and hop 3 minimum pressure, and resetting the hop counter;
searching for hop 3 maximum pressure, when hop 2 maximum pressure exceeds hop 3 minimum pressure by more than 8,000 kPa and a time lapse not greater than 0.5 seconds occurs between hop 2 minimum pressure and hop 3 minimum pressure, if 20 seconds has not elapsed since the first set of 3 hops was detected, and determining whether hop 3 maximum pressure exceeds hop 3 minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 3 maximum pressure does not exceed hop 3 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
searching for hop 4 minimum pressure after locating hop 3 if 20 seconds has not elapsed since the first set of 3 hops was detected and determining whether hop 3 maximum pressure exceeds hop 4 minimum pressure by more than 8,000 kPa;
restarting search for hop 1 if hop 3 maximum pressure does not exceed hop 4 minimum pressure by more than 8,000 kPa, and resetting the hop counter;
restarting search for hop 1 if hop 3 maximum pressure exceeds hop 4 minimum pressure by more than 8,000 kPa and a time lapse greater than 0.5 seconds occurs between hop 3 minimum pressure and hop 4 minimum pressure, and resetting the hop counter;
incrementing the hop counter, when hop 3 maximum pressure exceeds hop 4 minimum pressure by more than 8,000 kPa and a time lapse not greater than 0.5 seconds occurs between hop 3 minimum pressure and hop 4 minimum pressure;
after incrementing the hop counter, determining a desired pump pressure based upon machine speed when the hop counter counts less than 3 sets of hops, and overriding the torque control lever to hold the pump pressure constant at the desired pump pressure for a preselected time before resuming searching for a first hop;
recording current torque control lever position minus a predetermined amount as modified torque lever position when the hop counter counts 3 sets of hops, and continuing searching for hops;
resuming searching for hop 1 when the actual torque control lever position is less than said modified torque lever position, and resetting said hop counter;
resuming searching for hop 1 when the actual torque control lever position is not less than said modified torque lever position and the difference between hop maximum pressure and hop minimum pressure is not greater than 8,000 kPa, and resetting the hop counter;
resuming searching for hop 1 when the actual torque control lever position is not less than said modified torque lever position, the difference between hop maximum pressure and hop minimum pressure is greater than 8,000 kPa, and hop frequency is greater than 2 Hertz, and a time lapse not greater than 0.5 seconds occurs between consecutive hop minimum pressures.

23 more elements

Dependencies are inferred from the claim text.

Description4,366 words

Summary657 words

#The present invention pertains to an all wheel drive machine, and, more particularly, to a method for controlling hopping of the front wheels wherein hopping is a form of wheel slip caused by a mismatch of fluid flow from a supply pump to the pump driven front wheels that can cause the front wheels to lose physical contact with the ground.

#Earth moving equipment, such as a motor grader for example, often must operate in environments with poor footing conditions. Some earth moving machines are equipped with an all wheel drive system so that the front wheels of the machine, normally used for steering, are driven to help propel the machine in these poor footing conditions. Normally, only the rear wheels are driven, but when poor footing conditions are encountered causing excessive wheel slip, the front wheels of an all wheel drive machine can be driven to increase traction of the machine thereby reducing slip and maintaining directional control. When all wheels are in poor footing conditions, such as working on side slopes, or maximum traction is desired, the machine can be operated in an all wheel drive mode. Operating a motor grader in an all wheel drive mode for maximum traction may be desirable when the motor grader is performing a cutting operation, such as cutting a new road or grading on a side slope. The all wheel drive mode is also useful when a motor grader is used for removing snow from a roadway.

#On a motor grader, a hydraulic pump is used to supply pressurized fluid to pump motors which drive the front wheels in the forward and reverse directions. A torque control lever is used in the all wheel drive mode to control the pressure and therefore the rim pull delivered to the front wheels.

Brief description of the drawings6 figures

#These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.

#FIG. 1 is a diagrammatic side elevational view of a preferred embodiment of a motor grader constructed for operation in accordance with the present invention.

#FIG. 2 is a schematic block diagram of the transmission controller of the motor grader of FIG. 1 showing inputs and outputs.

Detailed description3,537 words

#Referring to FIGS. 1 and 2, a motor grader 10 has an engine 12 driving a main drive 14. The main drive 14 includes tandem amounted rear wheels 16, 18 driven by the engine 12 through an electronically controlled and hydraulically actuated transmission 20, and a rear differential 22. The transmission 20 is responsive to a gear shift lever 24 located in an operator's compartment 26 along with an all wheel drive switch 34, and a torque control lever 36. The transmission is preferably a countershaft transmission with an output shaft whose rotation is sensed by a transmission output shaft (TOS) sensor 38. The motor grader blade 40 is attached to the frame of the motor grader 10 between the rear wheels 16 and front wheels 42. In the all wheel drive mode of operation, the front wheels 42 are supplementing drive wheels that are, driven by wheel motors 44 that receive pressurized fluid from a hydraulic pump 46. Electronic transmission controls 48 are located in the cab 26 under the operator's seat and an electronic all wheel drive controller 50 is in front of the operator's cab.

#The transmission controller 48 receives inputs from the transmission shift lever 24, the inching pedal 28 and the TOS sensor 38. The controller 48 provides outputs to the all wheel drive controller 50 and the transmission solenoids 52 which operate the hydraulic control module 54 to shift the transmission through its eight forward and six reverse gears. The transmission solenoids 52, control the transmission clutches and determine the actual gear in which the transmission operates. Another output from the transmission controller 48 is an input to the all wheel drive controller 50. Other inputs to the all wheel drive controller 50 include an input from the all wheel drive switch 34, the torque control lever 36, and a motor grader ground speed sensor, such as radar ground speed sensor 56. While other methods of determining machine speed may be used, the radar is preferred because it gives an indication of ground speed that is independent of the wheels and therefore is not as susceptible to errors caused by wheel slip.

#Referring now to FIGS. 3 and 4, a control valve 58 is preferably located on the motor grader frame directly above the front axle. The control valve 58 contains a displacement solenoid 60 which controls spool shifting for motor displacement, a freewheel solenoid 62 which controls a freewheel spool 64 for freewheel mode activation, and a charge solenoid 66 which controls a charge spool 68 for charge circuit engagement. The all wheel drive hydraulic system schematic of FIG. 4 shows the wheel motors 44L, 44R, control valve 58, flushing valve 70 and pump 46 that are the primary mechanical system components. Located directly in front of the cab 26 is the flushing valve 70. Its function is to maintain system charge pressure and connect the low pressure side of the drive loop 72, which is determined by the direction of travel, to the charge circuit 74. The charge pump 76 is located under the cab 26 of the motor grader 10 and is preferably mounted on the hydraulic implement pump. It supplies system charge flow and any additional makeup flow required in the drive loop of the all wheel drive system. The all wheel drive system preferably shares the same hydraulic reservoir as the implements.

Facts

Application

08/276,081Filed 15 Jul 1994

Granted

12 Dec 1995

Term ended

15 Jul 2014

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification2 codes

B60K 17/356
For driving both front and rear wheels, e.g. four wheel drive vehicles: having fluid or electric motor, for driving one or more wheels
B60K
Arrangement or mounting of propulsion units or of transmissions in vehicles

Slip control in a machine for matching hydraulic pump fluid flow to pump driven supplementary front wheel drive motor fluid flow

Life of this patent

Slip control in a machine for matching hydraulic pump fluid flow to pump driven supplementary front wheel drive motor fluid flow

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims20

Description4,366 words

Drawings

Classification2 codes

Life of this patent

Description4,366 words