Method of automatically changing the speed stage of a construction vehicle based on vehicle loading

• US 5,257,193 A
• Filed: 08/08/1991
• Issued: 10/26/1993
• Est. Priority Date: 02/04/1987
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Komatsu Seisakusho
• Original Assignee: Kabushiki Kaisha Komatsu Seisakusho
• Inventors: Kato, Yoshiaki, Kato, Takeo, Kaneko, Kiyoshi, Kusaka, Kohei
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US07/742,282
• Time in Patent Office: 810 Days
• Field of Search: 364/424.1, 364/426.01, 364/426.04, 364/442, 364/431.01, 364/431.07, 74/866, 123/352, 123/357, 123/358, 123/478, 180/306
• US Class Current: 701/110
• CPC Class Codes: B60W 10/04 including control of propulsion units
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 2530/16 Driving resistance
• CPC Class Codes: B60W 30/1819 Propulsion control with control means using analogue circuits, relays or mechanical links
• CPC Class Codes: B60W 30/19 Improvement of gear change, e.g. by synchronisation or smoothing gear shift
• CPC Class Codes: B60Y 2200/14 Trucks; Load vehicles, Busses
• CPC Class Codes: F16H 2059/743 using engine performance or power for control of gearing transmission input torque F16H2059/147
• CPC Class Codes: F16H 2061/0012 Transmission control for optimising power output of driveline
• CPC Class Codes: F16H 2061/0015 Transmission control for optimising fuel consumptions
• CPC Class Codes: F16H 2061/0209 with independent solenoid valves modulating the pressure individually for each clutch or brake
• CPC Class Codes: F16H 2061/026 On-off solenoid valve
• CPC Class Codes: F16H 2302/04 Determining a modus for shifting selection of shift speed modus F16H2059/0226
• CPC Class Codes: F16H 2306/44 Removing torque from current gears
• CPC Class Codes: F16H 2306/54 Synchronizing engine speed to transmission input speed
• CPC Class Codes: F16H 59/14 Inputs being a function of torque or torque demand
• CPC Class Codes: F16H 59/18 dependent on the position of the accelerator pedal
• CPC Class Codes: F16H 59/48 Inputs being a function of acceleration
• CPC Class Codes: F16H 59/52 dependent on the weight of the machine, e.g. change in weight resulting from passengers boarding a bus
• CPC Class Codes: F16H 59/54 : dependent on signals from the brakes, e.g. parking brakes
• CPC Class Codes: F16H 61/0021 : Generation or control of line pressure
• CPC Class Codes: F16H 61/0213 : characterised by the method for generating shift signals
• CPC Class Codes: F16H 61/0437 : by using electrical signals F16H61/0403 and F16H61/061 take precedence
• CPC Class Codes: F16H 61/061 : using electric control means
• CPC Class Codes: F16H 61/14 : Control of torque converter lock-up clutches
• CPC Class Codes: F16H 61/143 : using electric control means
• CPC Class Codes: F16H 61/68 : specially adapted for stepped gearings
• CPC Class Codes: F16H 61/686 : with orbital gears
• CPC Class Codes: F16H 61/70 : specially adapted for change-speed gearing in group arrangement, i.e. with separate change-speed gear trains arranged in series, e.g. range or overdrive-type gearing arrangements
• CPC Class Codes: F16H 63/502 : for smoothing gear shifts
• CPC Class Codes: Y02T 10/40 : Engine management systems
• CPC Class Codes: Y02T 10/84 : Data processing systems or methods, management, administration

Abstract

A method for automatically changing the speed of a dump truck for use as a construction vehicle which is capable of improving the fuel cost by utilizing the engine output effectively and efficiently, improving the durability of the power transmission system and giving the driver a comfortable ride. According to this automatic speed change method, a desired, optimum speed stage which meets the loading condition of the dump truck and/or the engine output condition can be selected by using controllers each having a built-in computer.

Claims

1. A method for automatically changing the speed of a construction vehicle wherein an output side of an engine is connected to a torque converter provided with a lock-up clutch, wherein an output side of said torque converter is connected to an input side of a power transmission having a plurality of hydraulically actuated clutches, and wherein an output side of the power transmission is connected through a differential gear mechanism to left and right hand drive wheels, comprising the steps of:

when the vehicle is running in a heavy load condition, determining automatic speed change timing by setting a speed change point at each speed stage at an engine speed at which a maximum engine output is developed, and when the vehicle is running in a light load condition, placing the engine in a partial output developing condition to allow said vehicle to run at a selected constant vehicle speed;

inputting the amount of fuel injected into the engine and the current engine speed when the vehicle is running at the selected constant vehicle speed, to said controller so as to compute a currently developed engine output and an engine speed which corresponds to a point of intersection of an equi-horsepower curve for the currently developed engine output and an engine characteristic curve corresponding to that developed by the engine at its maximum output condition; and

comparing the product of the computed engine speed and the speed reduction ratio at a corresponding next higher speed stage with the product of the current engine speed and speed reduction ratio at a current speed stage and if the former product is larger than the latter product, outputting a shift-up signal to said controller so that a speed stage is selected which is higher than that which would be selected by said automatic speed change in the event the vehicle was running in a heavy load condition.

2. The method as claimed in claim 1, further comprising the step of transmitting a fuel injection control signal simultaneously with said step of automatically selecting a higher speed change to enable the production of a horsepower in said higher speed stage which is equal to the horsepower being produced in said current speed stage when the input is made.

3. A method for automatically changing the speed of a construction vehicle wherein an output side of an engine is connected to a torque converter provided with a lock-up clutch, wherein an output side of said torque converter is connected to an input side of a power transmission having a plurality of hydraulically actuated clutches, and wherein an output side of the power transmission is connected through a differential gear mechanism to left and right hand drive wheels, comprising the steps of:

controlling the fuel injection amount by selectively operating a running mode changeover switch which is operatively connected with both said engine and said transmission of the vehicle, between a first position wherein the engine is enabled to produce a first maximum power output and a second position wherein the engine is enabled to produce a second limited power output amount which is less than said maximum output, and

when the vehicle is running in a heavy load condition, setting said running mode changeover switch to said first position to enable said maximum power output and setting the speed change point at each speed stage at a speed corresponding to the maximum engine power output and when the vehicle is running in a light load condition, setting said running mode changeover switch to said second position wherein said second limited power output amount is enabled and setting the speed change point at each speed stage at a speed which is lower than the speed change point selected when the vehicle is running in a heavy load condition.

4. A method for automatically changing the speed of a construction vehicle wherein an output side of an engine is connected to a torque converter provided with a lock-up clutch, wherein an output side of said torque converter is connected to an input side of a power transmission having a plurality of hydraulically actuated clutches, and wherein an output side of the power transmission is connected through a differential gear mechanism to left and right drive wheels, comprising the steps of:

inputting a signal indicative of the position of an accelerator which determines the amount of fuel which is supplied to the engine to said controller,

inputting a signal indicative of the rotational speed of the power transmission input shaft to said controller, and

inputting a signal indicative of the speed stage which the power transmission is currently conditioned to produce, to said controller,

comprising a previous rotational speed of the power transmission input shaft with the present input shaft rotation speed, and computing a vehicle deceleration value, and

pre-selecting a speed stage to which the power transmission should be shifted based on the computed deceleration value, and,

transmitting a signal indicative of the pre-selected speed stage, as an output signal to said controller when the computed vehicle deceleration reaches a predetermined deceleration value so that a speed changeover is made directly to said preselected speed stage which is optimal for the reduced vehicle speed, said speed changeover being made irrespective of whether the shift is made to the next consecutive speed stage or not.

5. The method as claimed in claim 4, further comprising the steps of:

making the computation of said deceleration when said accelerator is maintained in a full open condition wherein the supply of fuel to the engine is maximized for more than a predetermined time.

6. The method as claimed in claim 4, further comprising the steps of:

prohibiting the computation of said deceleration when one of (a) the opening of said accelerator is zero wherein the amount of fuel which is supplied to the engine is minimized and (b) a braking signal is input for more than a predetermined time.

7. A method for automatically changing the speed of a construction vehicle wherein the output side of the engine is connected to a torque converter provided with a lock-up clutch, wherein the output side of said torque converter is connected to the input side of a power transmission having a plurality of hydraulically actuated speed stage clutches, wherein the output side of the power transmission is connected through a differential gear mechanism to left and right drive wheels, and wherein a manually operable mode control switch is operatively connected with both said engine and said transmission, comprising the steps of, when the vehicle is running in a heavy load condition, setting said manually operable switch to a setting wherein the engine is enabled to produced maximum engine power and conditioning said transmission to rapidly increase the fluid pressure in a selected speed stage clutch to a predetermined value so that the selected speed stage clutch can be connected quickly, and when the vehicle is running in a light load condition, setting said manually operable switch to a setting wherein the engine is enabled to produce an amount of engine power which is less than the maximum engine power, and condition said transmission to increase the fluid pressure in a selected speed stage clutch to a predetermined value comparatively slowly so that the selected speed stage clutch may be connected comparatively slowly without causing any shocks due to a speed change.

8. A method for automatically changing the speed of a construction vehicle wherein an output side of an engine is connected to a torque converter provided with a lock-up clutch, an output side of said torque converter being connected to an input side of a power transmission having a plurality of hydraulically actuated speed stage clutches, wherein an output side of the power transmission is connected through a differential gear mechanism to left and right drive wheels, comprising the steps of:

when the vehicle is running a heavy load condition, setting the speed change point at each speed stage at a speed corresponding to the maximum output of the engine, and when the vehicle is running in a light load condition, limiting the engine output to a level lower than said maximum output to allow said dump truck to run at a fixed, constant speed;

inputting the position of a means for controlling the amount of fuel injected into the engine and the engine speed when the vehicle is running at the constant speed to said controller so as to compute the instantly developed engine torque and horsepower and then computing a number of engine revolutions and torque which corresponds to a point of intersection of an equihorsepower curve and an engine characteristic curve corresponding to that of the engine at its maximum output condition; and

comparing the product of the computed engine torque at maximum engine output and the speed reduction ratio at a next higher speed stage, with the product of the computed engine torque at current engine output and the speed reduction ratio at a current speed stage when the input is made, making an allowance for torque, and if the former product is larger than the latter product, outputting a shift-up signal to said controller so that a speed stage is selected which is higher than that which would be selected by said automatic speed change in the event that the vehicle was running in a heavy load condition.