US-12624506-B2 - Asphalt distributor with multispeed motor

US12624506B2US 12624506 B2US12624506 B2US 12624506B2US-12624506-B2

Abstract

An asphalt distributor has a multispeed hydraulic motor mechanically driving an asphalt pump. The asphalt distributor has a controller for controlling the flow rate of asphalt being sprayed. The controller has a gain for controlling the flow rate. During a transition when the speed of the multispeed hydraulic motor changes, the gain has a value for the transition. Beneficially, the asphalt distributor has a wider than conventional asphalt spraying flowrate over which it provides a consistent spray. A method for controlling the flowrate involves adjusting, preferably dynamically, the value of the gain during the transition.

Inventors

Tyler Braun
Nick Frohmader

Assignees

E.D. ETNYRE & CO.

Dates

Publication Date: 20260512
Application Date: 20220823

Claims (20)

1 . An asphalt distributor for spraying asphalt onto the ground at a variable flowrate, the asphalt distributor comprising: a multispeed hydraulic motor having a first speed, a second speed, and an adjustable swashplate, the adjustable swashplate having a first position corresponding to the first speed and a second position corresponding to the second speed, an asphalt pump mechanically driven by the multispeed hydraulic motor, and a controller for controlling the flow rate of asphalt being sprayed, the controller having a gain for controlling the flow rate, a first mode in which the adjustable swashplate is in the first position, a second mode in which the adjustable swashplate is in the second position, and a transition mode for the movement of the adjustable swashplate between the first position and the second position, the first mode having a first flowrate range, the second mode having a second flowrate range different from the first flowrate range and overlapping at its lower end with the first flowrate range, the gain having a value for the first mode, a value for the second mode, and a value for the transition mode, the value for the transition mode being different from the value for the first speed and the value for the second speed, the controller entering into the transition mode when the motor switches between first speed and second speed.
2 . The asphalt distributor of claim 1 further comprising an engine and a hydraulic pump driven by the engine wherein the controller changes the flow rate of hydraulic fluid pumped by the hydraulic pump for achieving a desired asphalt flow rate.
3 . The asphalt distributor of claim 1 wherein the transition mode has a predetermined duration.
4 . The asphalt distributor of claim 1 wherein the transition mode ends when an absolute relative error is calculated by the controller to below 5%, the absolute relative error being the absolute difference between the flow rate and a desired flow rate divided by the desired flow rate.
5 . The asphalt distributor of claim 1 wherein the gain is selected from a proportional gain, an integral gain and a derivative gain.
6 . The asphalt distributor of claim 1 wherein the value of the gain during the transition mode is dynamically adjusted.
7 . The asphalt distributor of claim 6 wherein the dynamic adjustment of the gain comprises an increase in the proportional gain of the controller.
8 . The asphalt distributor of claim 7 wherein the increase in the proportional gain is a function of an absolute relative error and the increase increases as the absolute relative error increases, the absolute relative error being the absolute difference between the flow rate and a desired flow rate divided by the desired flow rate.
9 . The asphalt distributor of claim 6 wherein the dynamic adjustment of the gains comprises a decrease in an integral gain of the controller.
10 . The asphalt distributor of claim 9 wherein the decrease in the integral gain is a function of an absolute relative error and the decrease increases as the absolute relative error decreases, the absolute relative error being the absolute difference between the flow rate and a desired flow rate divided by the desired flow rate.
11 . The asphalt distributor of claim 1 wherein the controller is a PI or PID controller having a proportional gain and an integral gain, the value of the proportional gain for the transition mode being the same as a proportional gain for the second mode and the value of the integral gain for the transition mode being zero when the transition mode is for a switch from the first speed to the second speed.
12 . The asphalt distributor of claim 1 wherein the controller is a P, PI or PID controller having a proportional gain, the controller dynamically adjusting the proportional gain in transition mode, the adjusted proportional gain being the mathematical product of a base proportional gain and an adjusting function for the proportional gain, the adjusting function for the proportional gain being a linear function of the absolute relative error, and the adjusting function for the proportional gain having a value of 1 when the absolute relative error is zero.
13 . The asphalt distributor of claim 12 wherein the base proportional gain is the proportional gain for the mode corresponding to the speed that was switched to.
14 . The asphalt distributor of claim 13 wherein the controller is a PI or PID controller having an integral gain, the controller dynamically adjusting the integral gain in transition mode, wherein the adjusted integral gain is the mathematical product of a base integral gain and an adjusting function for the integral gain, the adjusting function for the integral gain being a linear function of the absolute relative error, and the adjusting function for the integral gain having a value of 0 when the absolute relative error is zero.
15 . The asphalt distributor of claim 14 wherein the base integral gain is the integral gain for the mode corresponding to the speed that was switched to.
16 . A method of controlling the flow rate of an asphalt pump driven by a multispeed hydraulic motor during a transition for a speed change of the motor, the method comprising: changing the speed of the hydraulic motor by adjusting a swashplate in the hydraulic motor, and during the transition for the speed change, dynamically adjusting a proportional gain and an integral gain of a PI or PID controller controlling the flow rate during the transition as a function of the absolute relative error, the absolute relative error being the absolute difference between the flow rate and a desired flow rate divided by the desired flow rate, the adjustment of the proportional gain being different from adjustment of the integral gain.
17 . The method of claim 16 wherein the adjusted proportional gain is the mathematical product of a base proportional gain and an adjusting function for the proportional gain, the adjusting function for the proportional gain being a linear function of the absolute relative error, and the adjusting function for the proportional gain has a value of 1 when the absolute relative error is zero.
18 . The method of claim 17 wherein the base proportional gain is the proportional gain for the speed that the speed was changed to.
19 . The method of claim 16 wherein the adjusted integral gain is the mathematical product of a base integral gain and an adjusting function for the integral gain, the adjusting function for the integral gain being a linear function of the absolute relative error, and the adjusting function for the integral gain has a value of 1 when the absolute relative error is zero.
20 . The method of claim 19 wherein the base integral gain is the integral gain for the speed that the speed was changed to.

Description

FIELD OF THE INVENTION The invention relates to asphalt distributors. BACKGROUND Asphalt distributors are used in building and maintaining roadways, particularly using the chip and seal technique. In the chip and seal technique, asphalt is first sprayed often onto existing paving by an asphalt distributor. The sprayed asphalt is then covered with “chips,” typically aggregate. The asphalt binds the chips so they stay in place. Asphalt distributors have a number of discrete sprays arranged typically substantially linearly so that asphalt can be sprayed across a width of the roadway that is often wider than the asphalt distributor. An exemplary asphalt distributor is described in U.S. Pat. No. 4,817,870. Problems arise if too little or too much asphalt is applied. If too little is applied, the chips won't stay in place. If too much is applied, the asphalt will puddle on the surface of the roadway and the asphalt will spread onto vehicles driving on the roadway. Uneven applications of asphalt will contribute to inconsistent road surfaces, creating bumps and ridges. Therefore it is important to maintain an even application rate (e.g., volume per area) over the entire area being coated in asphalt. Conventional asphalt distributors are designed to have an even application rate and can achieve this for relatively straight roadways. Conventional asphalt distributors have trouble maintaining the application rate when the width of spray is much less than the width of the asphalt distributor, i.e., few sprays are being used, and the asphalt spraying flowrate becomes small. Commonly, this occurs when applying asphalt is sprayed in turnarounds, intersections and shoulders. Alternatively, because of the difficulty in maintaining accurately a low flow rate, a higher flowrate may be used by deliberate overspraying, i.e., spraying where asphalt is not needed. A need therefore exists for an asphalt distributor that can maintain an even application rate across a wide range of flowrates or in all applications that an asphalt distributor is likely to be used. Asphalt distributors having an even application rate across a wide flowrate range have been attempted. Theoretically, an asphalt distributor having a two-speed hydraulic motor driving the asphalt pump could provide a wide flowrate range. However, in practice when the speed on the hydraulic motor changes, the spray fluctuates visibly. The fluctuation may cause the spray from the sprayers to not overlap properly or for the spray to surge. Either type of fluctuation could cause roadway inspectors to give the paving a failing grade. A need therefore exists for an asphalt distributor having a two-or-more-speed motor that can change hydraulic motor speed while maintaining an even application rate. Historically, asphalt distributors have had manual transmissions with a clutch. As the number of drivers proficient in shifting gears with a clutch declines, the popularity of asphalt distributors with automatic transmissions increases. However, in addition to the increased cost of an automatic transmission versus a manual transmission, there is an additional cost of a drop box for an automatic transmission to drive the hydraulic system because manual transmissions are capable of operating at a higher rpm without making the distributor go faster. The added drop box adds $8,000 to $10,000 to the cost of an asphalt distributor. A need therefore exists for an asphalt distributor having an automatic transmission that is not so costly. SUMMARY OF THE INVENTION In one embodiment of the invention, an asphalt distributor for spraying asphalt onto the ground is provided. The ground is typically a prepared pavement. The asphalt distributor has a multispeed hydraulic motor having a first speed and a second speed. The multispeed hydraulic motor may have additional speeds, but two speeds are preferred. The asphalt distributor also has an asphalt pump mechanically driven by the multispeed hydraulic motor. There may be a gear box (typically non-adjustable) to change the rate of rotation between the asphalt pump and the multispeed hydraulic motor. The asphalt distributor has a controller for controlling the flow rate of asphalt being sprayed. The controller has a gain for controlling the flow rate. The gain has a value for the first speed, a value for the second speed, and a value for a transition for a change in speed between the first and second speeds. The value for the transition is different from the value for the first speed and the value for the second speed. The gain may have more than one value during the transition in which case at least one of these values is different from the value for the first speed and the value for the second speed. The asphalt distributor may also have one or more axles for supporting the vehicle on the ground, a vessel for holding the material to be spread on or into the ground, a plurality of valves for controlling the lateral extent of distribution of the material