JPH0814525B2 - How to monitor work vehicle suspensions - Google Patents

Description

TECHNICAL FIELD The present invention generally relates to a method for accurately determining the state of a suspension (suspension device) of a work vehicle, and more particularly to a method for detecting a sunk strut by monitoring strut pressure.

BACKGROUND ART For example, in the field of off-road trucks used in mining operations, it is desirable to accurately record the amount of mining raw materials carried out from the mining site. This information helps in calculating mine and truck productivity, and in predicting profitability and work schedules.

Conventional approaches, such as those disclosed in U.S. Pat. No. 4,635,739, show that strut pressure can be an accurate indication of payload. The device disclosed in the patent application monitors each strut pressure, compensates for various inaccuracies caused by load distribution and vehicle attitude, and correlates the information thus obtained with the actual payload. including. However, proper operation of the payload monitor requires that all struts be in good working condition. For example, theoretical calculations for a particular group of struts show that a loss of 150 ml from a single strut results in a 22% error in the calculated load. There was no provision for monitoring the condition of the struts and displaying the condition of the bad struts.

In the conventional method, the driver of the vehicle relied on visual inspection of each strut before the start of driving.
This practice has caused a considerable degree of subjectivity in conventional schemes, which has tended to result in vehicles operating with struts partially or fully submerged. Both driver inattention and inability to recognize sunk struts are factors that cause erroneous driving. However, even with proper inspection, the struts may sink during driving. In large off-road trucks, the sinking of one strut does not significantly affect the "driving sensation" of the truck and is easily overlooked by experienced drivers.

Driving a vehicle with the struts submerged changes the relationship between strut pressure and payload, which adversely affects the accuracy of the load monitor. There are other important consequences of operating in this state. For example, by driving for a long time with the sunk struts,
This has the undesirable consequence of uneven wear on the tire. Tires are a significant off-road truck operating cost, and increased tire replacement schedules will have a significant impact on profitability. In other words, sunken struts can have economic consequences other than replacing damaged struts. In addition, fully submerged struts can result in repeated metal-to-metal contact, ultimately resulting in significant structural failure. In other words, the body frame is damaged in a relatively short operating period, and as a result, the necessary repair cost becomes huge.

The present invention overcomes one or more of the problems set forth above.

DISCLOSURE OF THE INVENTION A method of the present invention for periodically detecting sunken struts of a work vehicle having a plurality of left and right strut mounted wheels comprises:
Periodically detecting the internal pressure of the selected strut,
Outputting a plurality of first signals each having a magnitude correlated with the internal pressure of the selected strut. The method further includes a first pair of selected struts, eg, diagonally opposing struts, for obtaining an indication of the state of each strut in response to the selected strut pressure.
Calculating a ratio of the signals and comparing the ratio of the pressure signals to upper and lower set points and outputting a second signal if at least one of the ratios is outside the upper and lower set points. , A third indicating a depressed strut in response to receiving the second signal
The step of outputting a signal is included.

According to another feature of the present invention, a method of detecting one of a sunken strut and an air-deficient tire of a work vehicle having a plurality of left and right strut-mounted wheels includes a step of periodically detecting the internal pressure of a selected strut, and Outputting a plurality of first signals each having a magnitude correlated with the internal pressure of the strut. The method further comprises storing a second set of periodically output first signals in response to the first signal remaining substantially stable at the first magnitude for a predetermined duration. Calculating the stiffness of each strut according to the magnitude difference between the first and second sets of periodically output first signals, and the stiffness of each strut to the stiffness of another selected strut. Comparing and outputting second signals each having a magnitude correlated with the difference in stiffness. In response to the difference exceeding a predetermined set point, a signal indicative of a sunken strut is output.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of an off-road truck and the layout of the main suspension components.

FIG. 2 shows a block diagram of the suspension monitor device.

FIG. 3 shows a flowchart of the operation of the tire suspension monitor device when the truck is stationary.

FIG. 4 shows a flow chart of the operation of the tire suspension monitoring device during truck loading.

FIGS. 5A and 5B show a flowchart of the operation of the tire suspension monitor device while the truck is traveling on the road.

BEST MODE FOR CARRYING OUT THE INVENTION Referring now to the drawings illustrating a preferred embodiment of the apparatus 10, FIG. 1 shows a work vehicle 12, such as an off-road truck 14. The truck has at least one respective front and rear strut 16, 18 arranged in a relationship supporting a load bearing portion 20 of the work vehicle 12. The preferred embodiment has two front and rear struts 16 each.
L, 16R, 18L, 18R, which are commonly known in the art and are gas filled above liquid,
It will not be described in detail here. In understanding the device 10, it is normal that the fluid pressure supports the magnitude of the load applied to the struts 16 and 18, and the strut pressure fluctuates in a wide range. It is sufficient to recognize that this will also occur. Further, in the strut that lost the pressure and sank, the change in the strut pressure was remarkably small, and there was almost no change in "road driving". Conversely, an air-deficient tire increases the frequency of strut pressure changes within the struts that support the tire. That is, under-inflated tires have lower spring constants than air-relevant tires, thus enhancing the vibration response characteristics of the suspension to changes in strut pressure.

The load support unit 20 includes a vehicle frame 22 and a dump body 24. The dump body 24 includes a pivot pin 26 and a hydraulic cylinder 28.
Coupled to the frame 22 by the contents of the dump body 24, controllably pressurizing the hydraulic cylinder 28 and pivot pin
It can be discharged by rotating the dump main body 24 around 26. In the transport mode, the hydraulic cylinder 28 is not pressurized and the weight of the dump body depends on the pivot pin 26 and the frame.
It is transmitted to the frame via the support pad 30 fixed to 22.

Work vehicle 12 further includes a ground engaging portion 32, such as a tire, and suspension means 34 for supporting load bearing portion 20 to provide vibration damping between ground engaging portion 32 and load bearing portion 20. The suspension means 34 includes a rear axle housing 36 and an A-frame moment arm 38. The A-frame moment arm 38 has a first end 40 pivotally coupled to the vehicle frame 22 by a socket 42 and a first end 44 fixedly connected to the rear axle housing 36. First end 40 of moment arm 38 of A-type frame
Is a generally spherical Kingbolt structure and is held against lateral movement by a socket 42. The rear strut 18 is a first rotatably connected to a vehicle frame 22.
End 46 of the second side of the moment arm 38 of the A frame
The end 44 has a second end 48 pivotally coupled thereto.

When the truck is loaded, the load support 20 is displaced toward the ground engaging portion 32 as the payload increases. That is, the rear strut 18 begins to compress and the moment arm 38 pivots about its first end 40. The distance L2 is defined as the distance between the pivot point of the first end 40 and the pivot point of the second end 44 of the arm 38. The amount of change in the rear strut pressure is a function of the suspension means 34. The amount of change in the rear strut pressure is also related to the reaction force R between the work surface and the ground engaging portion 32. The force S applied to the rear strut 18 can be determined by measuring the internal pressure of the strut 18, subtracting the rear strut pressure corresponding to the unloaded truck, and multiplying the differential pressure by the area of the strut 18. It can be considered that the reaction force R is proportional to the payload of the vehicle 12, acts through the center of the rear housing 36, and the sum of the moments about the king bolt pivot point is given by:

(Formula 1.1) R = S * L2 / L3 However, the pivot point of the first end and the rear axle housing 36
Is defined as L3.

Similarly, the forward strut 16 also compresses as the load increases. However, the front struts are directly connected between the frame 22 and the front axle housing 50. There is a simpler relationship here and the force F on the front strut 16 is determined by multiplying the area of the strut 16. The reaction force F between the work surface and the surface of the ground engaging portion 32 is substantially equal to the force F applied to the front strut 16.

The device 10 shown in FIG. 1 shows the relationship between the work vehicle 12 and the position of the device 10. A more detailed block diagram of the device 10 is shown in FIG. 2 and includes means 52 for periodically sensing the pressure of each strut 16, 18 and outputting a plurality of signals, each correlating to the internal pressure of each strut. Shows. This means 52 comprises a plurality of pressure sensors 54, 56, 58, 60 of the type sold by Dynisco under the part number PT306. The pressure sensors 54, 56, 58 and 60 are attached to the two front struts 16L and 16R and the two rear struts 18L and 18R, respectively. The pressure sensors 54, 56, 58, 60 generate analog signals proportional to the pressure levels of the struts 16L, 16R, 18L, 18R, and the analog / digital converters (A / D) 62, 64, 66, respectively. , 68 to output. A / D62, 64, 66, 68
Is a model sold by Analog Devices under the part number AD575A. Other types of A / D converters can be used, and specific A / D
The choice is only a matter of designer discretion. It is particularly suitable for the environment of the digital microprocessor disclosed herein to choose a device that provides an analog / digital frequency output, although other similar devices could be used instead without departing from the spirit of the invention.

A Motorola Programmable Interface Array (PIA) 70 receives the digital frequency outputs from the A / D converters 62, 64, 66, 68 and outputs these signals to a microprocessor 72 under software control. In the preferred embodiment, microprocessor 72 is a Motorola.
Company part number 6809. The apparatus 10 also includes means 74 for receiving the control signal and outputting an indication of the size of the work vehicle payload in response to the magnitude of the control signal. The instruction means 74 is
A pair of individually energizable white lamps via a drive circuit 78
Includes another PIA76 connected to 80,82. These lamps 8
0, 82 are used to give instructions to the truck driver and the operator of the loader about the condition of the load against the rated truck capacity.

The third white lamp 84 is connected to the PIA 76 via the drive circuit 78. The third ramp 84 is addressable from the microprocessor 72 and indicates a sunk strut or deflated tire and is primarily visible to the truck driver.

3, 4 and 5, each subroutine is schematically illustrated in the form of a flow chart representing a software routine for detecting sunken struts of a work vehicle having a plurality of left and right struts mounted on wheels. There is. Each routine corresponds to a particular stage of vehicle operation and is only executed when it is detected that the vehicle is operating in a predetermined manner. For example, off-road trucks are known to work in specific routines, at any given time, stationary, waiting to be loaded or dumped, loading actually receiving load. Alternatively, it can be estimated that the vehicle is driving on a road between the loading place and the dumping place.

In the quiescent subroutine of FIG. 3, the software first determines by checking if all subroutines have been executed and if each subroutine has detected a sunk strut. If all routines match in that the struts are sunk, control returns to the main control routine without further processing. Thus, microprocessor time is retained for execution of the main control routine. At decision block 86, the value of variable R is checked. R = 0 indicates that it is not all routines that detected a sunk strut, but it is desirable to execute at least one subroutine. Control proceeds to decision block 88, which checks and determines if each subroutine has been executed.
Upon successful completion of the stationary, loading and road driving subroutines, variables F11, F22 and F33 are each set to the value "1". If all subroutines have been executed, control passes to decision block 90. If the subroutine has not been executed, decision block 92 is chosen and decision block 90 is bypassed. In decision block 90, variables F1, F2, and F3
Is compared to the value "1". These variables "1" indicate that the sunken struts were detected by the stationary, loading and road driving routines, respectively.

If the condition F1 = F2 = F3 = 1 is met, the variable R is set to 1 and control returns to the main routine via blocks 94,96. Thereafter, execution of the control routine transfers control to decision block 86 or block 98, where no subroutines are executed and control is immediately returned to the main routine.

If it is not all subroutines that have detected the sunk struts, then control transfers to decision block 92. In the main control routine, the road running flag is set in accordance with the fluctuation input of a predetermined magnitude or frequency of the speedometer or strut pressure, which is an instruction that the vehicle is actually running on the road. Road flag value "1"
Then, the control proceeds to the road traveling routine shown in FIG. Alternatively, if the value of the road driving flag is zero and the vehicle is stationary,
Control proceeds to block 100, where the variables COUNTER, TURN and F333 are all set to zero. All these variables are used in the road cycle and are reset here in anticipation of the next road cycle. Control then passes to decision block 102, where the variable PASS is checked to determine if the quiescent subroutine is the first cycle in the initial run. Not the first cycle
If the variable PASS equals the value 0, control passes to the loading routine of FIG. If it is the first cycle of the quiescent subroutine, control proceeds to block 104 where variable F11 is set to 1 as an indication that the quiescent subroutine has been performed. Thereafter, at block 106, the pressure ratios for the diagonally corresponding vehicle struts 16L, 16R, 18L, 18R are calculated. For example, left anterior strut 16L and right posterior strut 18R correspond to pressures P1 and P4 sampled in the main control routine, respectively. Similarly, the right front strut
The pressures on the 16R and the left rear strut 18L correspond to P2 and P3, respectively. The use of diagonal pressure ratios is to enhance the pressure differential created by the sunken struts. That is, a sinking left front strut affects the corresponding right rear strut pressure. Therefore, if the pressure difference of the submerged left front strut can be detected, the pressure difference of the ratio of left front to right rear is more significantly affected and can be easily detected accordingly. Similar reasoning applies to each strut and each corresponding diagonal pressure ratio.

Control then proceeds to decision block 108 where it is determined during the initial start-up phase of the vehicle's driving history whether the software is performing the first pass through the quiescent routine. The variable P is initially set to the value "1" in the initial setting of the vehicle. That is, in the first pass, control transfers from decision block 108 to block 110 where the upper and lower limits of the diagonally related pressure ratio are set. The upper diagonal limit is set to 125% of the previously calculated value, while the lower limit is set to 75% of the previously calculated value. Further, the variable P is set to the value "2". After that, since the variable P is set to 2, the upper and lower limits of the relative pressure ratio remain at the values calculated initially, and the decision block 108 does not proceed to the block 110.
After execution of block 110, block 112 returns control to the main control routine.

At the next iteration of the quiesce subroutine, decision block 10
8 directs control to a series of decision blocks 114, 116, 118 and 120, where each diagonal relationship pressure ratio exceeds their upper and lower limits, control passes to block 122, where the variable PASS Set to the value "2" to prevent the quiesce routine from re-executing via block 102. Also, the variable F1 is set to the value "1", indicating that the rest routine has detected a sunk strut. Control then passes to block 124.
And control returns from there to the main control routine. If, on the other hand, none of the diagonally related pressure ratios is found to exceed the corresponding upper and lower limits, control proceeds to block 126, where the variable PASS is set to the value "2" and then block 128. Return to control routine.

Referring now to FIG. 4 which illustrates the loading subroutine, first the variable PASS is set to the value "2" and then control enters this subroutine. The variable F222 is checked at decision block 129 to determine if its value is equal to the value "1". The variable F222 is set to the value "1" at the completion of the loading routine and reset by the road driving subroutine. If the variable F222 is equal to the value "1", then "knows" that only the loading sub-routine is executed without the road-running sub-routine afterwards and it is not worth re-executing the loading sub-routine. Therefore, control transfers to block 130 from which the main control routine is returned.

If the variable F222 is equal to the value zero, control passes to decision block 13
Move to 1. At block 131, the variable VARIABLE is compared to the value zero to determine if this cycle is the first of a particular loading cycle. If the load is the first iteration of a particular load cycle and VARIABLE equals the value zero, then at block 132 the variable PCLR is set equal to LR,
The variable PCRR is set equal to the variable RR. Variables PCLR and PC
The RRs each represent the previously calculated left and right posterior strut pressures corresponding to the strut pressures at the beginning of a particular loading cycle. At block 134 VARIABLE is reset to the value "1" to maintain PCLR and PCRR at the corresponding values at the beginning of the loading cycle and at block 136 control is returned to the main control routine.

During subsequent loading subroutine iterations, VARIAB
Since LE has been reset to the value "1", block 131 directs control to decision block 138 where the earliest strut pressure LR, RR is compared to the initial strut pressure PCLR, PCRR. In the example shown, if the difference is less than 30 psi,
Control returns to the main control routine via block 140. It will be appreciated that the values used here are for illustrative purposes only and will vary with vehicle type as is well known. Decision block 138 ensures that a bucket load of mineral feedstock is applied to the vehicle and that slight changes in rear strut pressure are not due to small vibrations in the vehicle suspension. If the currently calculated aft strut pressure exceeds the initial aft strut pressure by 30 psi, control transfers to decision block 142 where the aft differential pressure is compared to a 100 psi differential set point. If the difference is greater than 100 psi on any of the aft struts, control transfers to block 144 and the variable INC is incremented by the value "1". Decision block 146 takes control from decision block 144 and compares variable INC with the value 100 to see if the received pressure value is stable. Any posterior strut differential pressure of 100 during 100 iterations of differential loading
Once psi is exceeded, control determines that the recorded pressure is stable and moves to block 148. In block 148, the variable F2
After the 2 is set to the value "1" to indicate that the loading subroutine has completed successfully, control transfers to block 150. If the variable INC is less than 100, the control determines that the pressure is not stable and returns control to the main control routine via block 152. If none of the differential pressures is greater than 100 psi, the control determines that the data is taken when the bucket load of the mineral raw material is being injected into the vehicle, which causes the vibration with large differential pressure to appear. Therefore, control passes to block 154.
, Where both variables INC and VARIABLE are reset to the value zero. Control then returns to the main control routine via block 156.

At block 150, the variable LOTEST is calculated as a function of the ratio of the left and right posterior strut differential pressures. Also, between the relative stiffness (k) of each strut and the strut differential pressure,
It has been shown that a relationship exists. This relationship is defined as: k = P2 ** 2 / (P2-P1) where P2 corresponds to the current strut pressure and P1 corresponds to the total strut pressure.

Since the strut stiffness is dynamic throughout the range of strut movement, it is difficult to determine if the calculated stiffness is within the acceptable range. However, each aft strut can be presumed to respond similarly to additional loading and is, in fact, within the same range of travel. As such, each strut has a stiffness similar to other struts, and the ratio of both yields a value of about 1. The equation for this relationship is expressed as: kRR / kLR = [(LR-PCLR) * (RR ** 2)] / [(RR-PCRR) * (LR * 2)] where the strut stiffness ratio Corresponds to the variable LOTEST.

The load distribution has some effect on the range of movement of the struts, but it is recognized that there is an upper limit to this effect. LOTEST exceeds 30% difference in strut stiffness
The values are compared to the range of 0.7-1.3 at blocks 158 and 160 as they can be attributed to sinking struts.
If the value is outside this range, control passes to block 162 and variable F2 is set to the value "1" as an indication of the sunk strut. Control then proceeds to block 164 where the variable F222 is set to the value "1" to prevent the loading subroutine from being re-executed when there are no intervening road driving cycles. Furthermore, both variables INC and VARIABLE are also reset to zero in anticipation of the next loading cycle. Then block
166 receives control and transfers it to the main control routine.

Referring now to FIG. 5, first, in response to the road running flag being set to the value "1" via decision block 92,
Control enters a subroutine. In decision block 168 of this road subroutine, the variable F333 is compared to the value zero, and if it is not equal to zero, control passes to block 170,
From there it returns to the main control routine. The variable F333 is initially set to the value "1" by the main control routine and reset to the value zero during the quiesce subroutine. That is, decision block 168 prevents execution prior to execution of the quiesce subroutine. The variable F333 is set to the value zero in the quiesce subroutine to allow the loading cycle to be performed during the next loading cycle.

Variable counter COUNTE as an indication of road travel route time
R is advanced at block 172. Since the execution loop time of the subroutine is consistent, the actual value of the variable counter indicates the elapsed time. For example, a counter value equal to 40,000 corresponds to a road travel elapsed time of about 6 minutes and 40 seconds. Therefore, in decision block 174, the variable counter is compared to 40,000, and if the elapsed time is less than 6 minutes and 40 seconds, control is passed to decision block 17
Moving to 6, the variable TURN is compared with the value zero. Variable T
If URN equals the value zero, the control determines that this routine is the first cycle of the road driving subroutine and moves to block 178 where the variables TLF, TRF, TLR and TRR are set to LF, RF, LR and RR respectively. Loaded with the pressure detected before. In addition, the variable TURN is set to the value "1" and control returns to the main control via block 180. As a result of the variable TURN being set to the value "1", control passes from decision block 176 to decision block 182 in subsequent iterations of the road driving routine.

At decision block 182, the left anterior strut pressure is compared to the previous left anterior strut pressure, and if the difference is greater than 30 psi, the variable CLF is advanced by the value "1". Left front pressure difference is 3
If 0 psi is not exceeded, block 184 is bypassed and variable CLF is not advanced. Similarly, if the LF pressure is zero, the judgment block
183 bypasses block 184 and variable CLF is not advanced.
This scheme prevents the variables from being advanced if the struts suddenly lose pressure and sink. Allowing the variable to advance when the strut sank reduces the count difference,
There is an increased chance that a sunken strut will go undetected. At the end of the 6 minute 40 second period, the variable CLF contains a count of the number of times the difference between two successive pressure readings of the left strut exceeds 30 psi.

Control then proceeds to blocks 186, 188 and 190 where similar actions are taken for each remaining strut pressure. The variables CLF, CRF, CLR and CRR each contain a count value corresponding to the number of times the successive pressure readings exceeded the difference of 30 psi for the strut and 60 psi for the posterior strut, respectively. At decision block 192, the previous pressure readings TLF, TRF, TLR, and TRR are updated with the latest pressure reading. Control then returns to the main control routine via block 194.

The above process is repeated until the time of the road driving difference counter variable value exceeds 40,000. At that time, control transfers to block 196 where variable F33 is set to the value "1" as an indication of the completion of the road driving subroutine. Control then passes to block 198, where variable CLF is used.
RF is set equal to the ratio of the left front count value CLF and the right count value CRF. If the count ratio is within the range of 0.5-2, the road running subroutine determines that both struts in front of the left and right struts have responded similarly to similar road conditions and are not sunk. However, if the count ratio is outside the above range, decision blocks 200 and 202 block control.
At 204, the variable F3 is set equal to the value "1" as a sunk strut indication. Similarly, the count ratio of the left and right rear struts is stored at block 206 as the variable CLRRR. A backward count ratio of 0.5 at blocks 208 and 210
~ 2 range. If the count ratio is outside this predetermined limit, control again passes to block 204 and variable F3 is set to the value "1". If the backward count ratio is within the predetermined limit, control bypasses block 204 and goes directly to block 2
Moving to 12, the variable F333 is set to the value "1". F3
33 prevents the road driving subroutine from being re-executed in the absence of an intervening loading cycle. Control then passes to block 214 and finally returns to the main control routine.

INDUSTRIAL APPLICABILITY During the entire movement of the off-road truck 14, the vehicle 12 is not driven for the first time during its production history, but in the usual way, including stationary, loading and roadside parts of the normal haul cycle. It is assumed that it has been used before. At start-up, when the vehicle is first turned on for daily driving, the main control routine begins with each strut 16L, 16R, 18L, 1
Read the 8R pressure and store these values as variables P1, P2, P3, P4. The main control routine then calls the quiescent subroutine to determine if none of the subroutines detected a sunk strut. On the first pass through the quiesce subroutine, the diagonal relationship ratios LFRR, RFLR
Is calculated and compared with the upper and lower bounds of the diagonal relation ratio calculated previously. If either of the diagonally related pressure ratios LFRR, LFLR is outside the upper and lower limits, the variable F1 is set to the value "1", indicating that the struts are sinking. 1 at the first startup each day
Only once, the diagonal pressure ratio is calculated and compared to the upper and lower limits.

While the vehicle driver is waiting for the vehicle to reach its operating temperature and pressure, the main control routine periodically samples the strut pressure and calls the quiescent subroutine. After the initial cycle of the quiesce subroutine, the loading subroutine is called. On the first iteration of the loading routine, the variables PCLR and PCRR are set to the left and right rear strut pressures corresponding to empty trucks, respectively. Subsequent iterations of the loading routine will update the latest strut pressure to the variable PCLR.
And the strut pressure of the empty truck stored as PCRR. A differential pressure greater than 100 psi is used to indicate that a mineral feed load has been applied to the off-road truck. To prevent unstable pressure from being remembered,
The loading subroutine does not calculate the rear strut stiffness ratio until after the vehicle has stabilized. The loading subroutine requires the differential pressure to stay above 100 psi for a total of 100 iterations. Here, the responses of the left and right rear struts to the additional load are compared with each other, and if they are significantly different, the struts are considered to be in a sunk condition and the flag F2 is set to the value "1". The variable F222 is also set to the value "1" regardless of whether a sunk strut is detected, preventing the loading subroutine from re-executing before the intervening road driving subroutine.

However, in this example, the driver is only waiting for the vehicle to reach a driving state, so at this point he does not anticipate loading the truck bed. Therefore, the loading routine is called periodically, but the differential pressure does not exceed the required 100 psi. In the next driving cycle part where the driver drives the vehicle to the loading place, the main control routine recognizes that the vehicle is driving on the road, but there is no intervening loading cycle and the road running flag is Not set. Therefore, the main control routine continues sampling the strut pressure at predetermined intervals and calls the quiescent subroutine. The quiesce subroutine responds to the absence of the road flag and calls the loading subroutine until the actual loading cycle has taken place.

When the vehicle reaches the loading place, it stops traveling on the road. Inevitably when the vehicle is loaded, the rear strut pressure is 100 psi as the mineral material is loaded onto the truck.
Expected to respond to greater differential pressure. This 100p
Once a differential pressure of si or greater is detected and deemed stable, the loading subroutine calculates the stiffness of diagonally facing struts and compares them to the controls described above.

After the loading cycle is complete, the driver envisions the vehicle on the road to the unloading location, during which the road-running subroutine is repeatedly called to determine the condition of the struts. And during this period, a count is maintained for each strut that indicates the number of times the successive pressure readings have exceeded a predetermined value for each strut. At the end of this period,
The counts for the anterior struts are compared to each other and are used as an indication that the anterior struts are in a sunk condition if the counts are significantly different. Similarly, the counts of the posterior struts are compared to each other and, if the counts are significantly different, are used as an indication that the posterior struts are in a depressed condition. For example, a vehicle with properly filled struts would be expected to respond to road driving and loading conditions with each strut in a similar manner to struts on the same axle. Also, if one of the struts on the axle is partially submerged, a significantly smaller magnitude pressure change is expected. Thus, for an axle with partially submerged struts, the count for the submerged struts will be significantly smaller and the corresponding difference between struts on that axle will be greater.

At the unloading location, the stationary subroutine periodically transfers control to the loading subroutine after completion of the road cycle. However, the loading subroutine is not executed until the driver returns to the loading location and the next loading cycle begins. After that, the control including the road traveling and the loading cycle is repeated.

Other features, objects, and advantages of the invention will be set forth in the drawings,
It will be gained by studying the disclosure content and the appended claims.

Front Page Continuation (72) Inventor Gudad Adam Jay 61526 Edelstein Rural Route 1 Box 66 A (56) References US Patent 3900828 (US, A) US Patent 4317105 (US, A) US Patent 2638777 (US) , A)

Claims (13)

[Claims] 1. A sunken strut (16L, 16R, 18L, 1) of a work vehicle (12) having a plurality of left and right strut mounting wheels.
8R): a method of detecting the internal pressure of each strut (16L, 16R, 18L, 18R) periodically, and having a magnitude correlated with the internal pressure of each strut (16L, 16R, 18L, 18R) Outputting a plurality of first signals; calculating a ratio of the first signals of the selected pairs of struts; comparing the magnitude of each ratio with upper and lower set points, at least one of said ratios Second depending on being out of set point
Outputting a signal; and struts (16L, 1L) sunk in response to receiving the second signal.
Outputting a third signal indicative of 6R, 18L, 18R). 2. The step of calculating the ratio calculates the ratio of the first signals of the left front strut (16L) and the right rear strut (18R), and the right front strut (16R) and the left rear strut. A method according to claim 1 comprising calculating the ratio of the (18L) first signal. 3. A pair of selected struts (16L, 16R, 18).
L, 18R) first signal ratio calculating step calculates the ratio of the selected forward strut (16L, 16R) first signal to the selected posterior strut (18L, 18R) first signal. The method according to claim 1, wherein 4. The comparing step compares the larger ratio of the corresponding pair ratios to the upper and lower set points, and second in response to at least one of the ratios being outside the upper and lower set points. The method of claim 1 including outputting a signal. 5. At the beginning of use of the work vehicle (12), increasing the calculated value of the ratio of the first signals by a predetermined percentage and storing this value as the respective upper set point of each ratio, The method of claim 4 including the step of calculating an upper set point as a function of each ratio. 6. By reducing the calculated value of the ratio of the first signal by a predetermined percentage at the beginning of use of the work vehicle (12) and storing the lowered value as the respective lower set point of each ratio. The method of claim 4 including the step of calculating a downset point corresponding to each ratio. 7. The method of claim 1 including the step of stopping the calculation of the ratio in response to movement of the work vehicle (12). 8. The first vehicle according to movement of a work vehicle (12).
The method of claim 1 including the step of stopping the calculation of the ratio of signals. 9. A sunken strut (16L, 16R, 18L, 1 of a work vehicle (12) having a plurality of left and right strut-mounted wheels.
8R) in the method of detecting: select a predetermined number of struts from the struts,
Outputting a plurality of first signals each having a magnitude correlated with the internal pressure of the selected strut (18L, 18R); the first signal being substantially stable at the first magnitude for a first predetermined duration Storing a first set of periodically output first signals in response to remaining at the first signal; said first signal being substantially stable to a second magnitude for a second predetermined duration. Storing a second set of cyclically output first signals in response to remaining stationary; a difference in magnitude between the first and second sets of cyclically output first signals; Struts (18L, 18
R) to calculate the stiffness for each; for each of the selected struts (18L, 18R),
Struts whose stiffness is selected above (18L, 18R)
Outputting a second signal each having a magnitude that is correlated to the difference in the stiffness of the other strut of the strut; and sunk in response to the second signal exceeding a predetermined set point. Outputting a signal indicating a strut (16L, 16R, 18L, 18R). 10. The method of claim 9 wherein said comparing step comprises comparing the stiffness of only the left and right posterior struts (18L, 18R). 11. The method according to claim 10, wherein the comparing step includes calculating a stiffness ratio of the left and right rear struts (18L, 18R) and outputting a second signal in accordance with the magnitude of the ratio.
The method described in the section. 12. The sunken strut (16L, 16R, 18
12. The method of claim 11, wherein the step of outputting a signal indicative of L, 18R) comprises comparing the ratio to a predetermined range. 13. The method of claim 12 wherein said predetermined range is 0.7 to 1.3.