GB2395989A - Maximising run-away resistance in a drive in a near stationary hydraulically driven vehicle - Google Patents

Maximising run-away resistance in a drive in a near stationary hydraulically driven vehicle Download PDF

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Publication number
GB2395989A
GB2395989A GB0227629A GB0227629A GB2395989A GB 2395989 A GB2395989 A GB 2395989A GB 0227629 A GB0227629 A GB 0227629A GB 0227629 A GB0227629 A GB 0227629A GB 2395989 A GB2395989 A GB 2395989A
Authority
GB
United Kingdom
Prior art keywords
travelling
hydraulic
vehicle
motor
speed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB0227629A
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GB0227629D0 (en
GB2395989B (en
Inventor
Ji Masaaki Gen
Eric Jacques
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Komatsu Ltd
Original Assignee
Komatsu UK Ltd
Komatsu Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Komatsu UK Ltd, Komatsu Ltd filed Critical Komatsu UK Ltd
Priority to GB0227629A priority Critical patent/GB2395989B/en
Publication of GB0227629D0 publication Critical patent/GB0227629D0/en
Priority to JP2003385169A priority patent/JP2004176918A/en
Priority to DE10354194A priority patent/DE10354194B4/en
Priority to FR0313606A priority patent/FR2847525B1/en
Priority to CNA2003101180516A priority patent/CN1506598A/en
Publication of GB2395989A publication Critical patent/GB2395989A/en
Application granted granted Critical
Publication of GB2395989B publication Critical patent/GB2395989B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/4157—Control of braking, e.g. preventing pump over-speeding when motor acts as a pump
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/4043—Control of a bypass valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/42—Control of exclusively fluid gearing hydrostatic involving adjustment of a pump or motor with adjustable output or capacity
    • F16H61/425—Motor capacity control by electric actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/46—Automatic regulation in accordance with output requirements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/46—Automatic regulation in accordance with output requirements
    • F16H61/462—Automatic regulation in accordance with output requirements for achieving a target speed ratio
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/36—Inputs being a function of speed
    • F16H59/44—Inputs being a function of speed dependent on machine speed of the machine, e.g. the vehicle
    • F16H2059/446—Detecting vehicle stop, i.e. the vehicle is at stand still, e.g. for engaging parking lock
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H47/00—Combinations of mechanical gearing with fluid clutches or fluid gearing
    • F16H47/02—Combinations of mechanical gearing with fluid clutches or fluid gearing the fluid gearing being of the volumetric type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/36—Inputs being a function of speed
    • F16H59/44—Inputs being a function of speed dependent on machine speed of the machine, e.g. the vehicle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H59/00—Control inputs to control units of change-speed-, or reversing-gearings for conveying rotary motion
    • F16H59/50—Inputs being a function of the status of the machine, e.g. position of doors or safety belts
    • F16H59/54—Inputs being a function of the status of the machine, e.g. position of doors or safety belts dependent on signals from the brakes, e.g. parking brakes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/21—Providing engine brake control

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Fluid Gearings (AREA)
  • Control Of Transmission Device (AREA)
  • Motor Power Transmission Devices (AREA)

Abstract

The apparatus includes a pump 12, a variable capacity hydraulic motor 13 and a transmission 14 which includes gear change control and at least two ratios, a vehicle speed detector 31 operating on a speed detecting pump/motor set 17, 18 and a controller 30 which sends a signal to the gear change control valve 16 to shift down the transmission and/or to a motor capacity control valve 26 to increase motor capacity when it is determined by the speed detector that the vehicle is almost stopped i.e. below a preset speed for a given time. Ensures that the drive automatically has maximised resistance to run-away when brought to rest.

Description

TRAVEL CONTROL APPARATUS OF HYDRAULIC
TRAVELLING VEHICLE
Technical Field
5 The present invention relates to a travel control apparatus of a hydraulic travelling vehicle.
Background Art
10 Hitherto, a hydraulic travelling vehicle, which travels by driving a variable displacement travelling hydraulic motor with pressure oil from a travelling hydraulic pump driven by an engine, includes a transmission in order to improve travel performance. Since the transmission mounted in the hydraulic 15 travelling vehicle which is a working vehicle needs to cover a speed range from a dead slow speed range for a primary operation to a normal travelling speed to travel on ordinary roads, it generally has multiple speed gears. When such a hydraulic travelling vehicle travels at high speed, a high speed 20 gear is selected as the speed gear of the transmission, and the capacity of the travelling hydraulic motor is made minimum for high speed rotation, thereby enabling high speed travelling.
However, when such a hydraulic travelling vehicle stops after travelling at high speed, the speed gear of the automatic 25 transmission remains the high speed gear, and the capacity of
the travelling motor remains minimum. When the vehicle in such a state stops in the middle of a sloping road, the vehicle is moved toward the bottom of the sloping road while the brake is not depressed, and the travelling hydraulic motor is driven by 5 the rotation of wheels. Incidentally, in the following explanation, it is defined as "reverse driving" that "the travelling hydraulic motor is driven by the rotation of the wheels due to slip-down of the hydraulic travelling vehicle or the like". When thus reversely driven, the travelling 10 hydraulic motor functions as a pump, but resistance to reverse driving force is small since its capacity is made minimum.
Accordingly, while the brake is not depressed, the vehicle descends the sloping road, thereby slip-down of the vehicle occurs, and the slip-down speed at which the vehicle slips down 15 increases fast. When a circuit connecting an inlet side and an outlet side of the travelling hydraulic motor when the travelling hydraulic motor is reversely driven is provided in order to prevent cavitation of the travelling hydraulic motor, the slip-down speed increases faster since the travelling hydraulic 20 motor is easily rotated by the reverse driving force.
Summary of the Invention
The present invention is made in view of the 25 aforementioned disadvantages, and its object is to provide a
travel control apparatus of a hydraulic travelling vehicle capable of keeping slip-down speed on a sloping road in a lower range. To attain the aforementioned object, a first constitution 5 of a travel control apparatus of a hydraulic travelling vehicle according to the present invention is characterized in that a travel control apparatus of a hydraulic travelling vehicle including a travelling hydraulic motor and a transmission whose speed gear is allowed to be fixed, includes gear change control 10 means of the transmission, vehicle speed detecting means for detecting vehicle speed of the hydraulic travelling vehicle, and a controller which sends a shift-down signal to the gear change control means to shift down the transmission when it is determined by the detected vehicle speed that the hydraulic 15 travelling vehicle is almost stopped.
According to such a constitution, the reduction ratio of the transmission is high, even if the wheels try reverse driving because the hydraulic travelling vehicle tries to slip down a sloping road. Therefore, the reverse driving force of the 20 wheels is reduced by the reduction ratio of the transmission, and force for reversely driving the travelling hydraulic motor reduces, and consequently the rotation speed of the travelling hydraulic motor lowers, and thus the slip-down speed can be kept in a lower range.
25 A second constitution of the travel control apparatus of -
the hydraulic travelling vehicle according to the present invention is characterized in that a travel control apparatus of a hydraulic travelling vehicle including a variable displacement travelling hydraulic motor, includes motor capacity control 5 means of the variable displacement travelling hydraulic motor, vehicle speed detecting means for detecting vehicle speed of the hydraulic travelling vehicle, and a controller which sends a capacity increasing signal to the motor capacity control means to increase a capacity of the variable displacement travelling 10 hydraulic motor when it is determined by the detected vehicle speed that the hydraulic travelling vehicle is almost stopped.
According to such a constitution, even if the wheels try reverse driving because the hydraulic travelling vehicle tries to slip down the sloping road, the capacity of the travelling 15 hydraulic motor is made maximum. Therefore, the travelling hydraulic motor rotates only at a low rotation speed, and besides the rotational resistance inside the travelling hydraulic motor increases, whereby the slip-down speed can be kept in a lower range.
20 A third constitution of the travel control apparatus of the hydraulic travelling vehicle according to the present invention is characterized in that a travel control apparatus of a hydraulic travelling vehicle including a variable displacement travelling hydraulic motor and a transmission whose speed gear 25 is allowed to be fixed, includes gear change control means of
s the transmission; motor capacity control means of the variable displacement travelling hydraulic motor, vehicle speed detecting means for detecting vehicle speed of the hydraulic travelling vehicle, and a controller which sends a shift-down 5 signal to the gear change control means to shift down the transmission and sends a capacity increasing signal to the motor capacity control means to increase a capacity of the variable displacement travelling hydraulic motor when it is determined by the detected vehicle speed that the hydraulic travelling 10 vehicle is almost stopped.
According to such a constitution, the wheels are driven because the hydraulic travelling vehicle tries to slip down a sloping road, and hence the travelling hydraulic motor is reversely driven through the transmission. However, since the 15 reduction ratio of the transmission is high, the reverse driving force of the wheels is reduced by the reduction ratio of the transmission, and the force for reversely driving the travelling hydraulic motor reduces. Consequently, the rotation speed of the travelling hydraulic motor lowers, and the capacity of the 20 travelling hydraulic motor is made maximum, whereby the travelling hydraulic motor rotates only at a low rotation speed.
Besides, the rotational resistance inside the travelling hydraulic motor increases, whereby the slip-down speed of the hydraulic travelling vehicle can be kept in a lower range.
25 Moreover, it is suitable that in the travel control
apparatus of the hydraulic travelling vehicle, travelling motor throttle valves be provided in a circuit connecting an inlet side and an outlet side of the travelling hydraulic motor when the travelling hydraulic motor is driven by rotation of wheels of the 5 hydraulic traveling vehicle. According to this constitution, pressure oil from the travelling hydraulic motor passes through the travelling motor throttle valves provided in the circuit connecting the inlet side and the outlet side of the travelling hydraulic motor by the reverse driving. Therefore, the 10 pressure loss of the pressure oil occurs, whereby the rotational resistance caused by the reverse driving increases, and hence the reverse rotation speed of the travelling hydraulic motor can be kept in a lower range. Accordingly, the reverse driving force of the travelling hydraulic motor, which is caused because 15 the working vehicle slips down the sloping road, becomes maximum and a large resistance, and consequently, the slip-down speed of the hydraulic travelling vehicle be kept at a sufficiently low speed.
Further, it is suitable that in the travel control apparatus 20 of the hydraulic travelling vehicle, the controller determine that the hydraulic travelling vehicle is almost stopped when the detected vehicle speed is a predetermined speed or lower for a predetermined time. According to this constitution, when the detected vehicle speed is the predetermined speed or lower for 25 the predetermined lime, it is determined that the hydraulic
travelling vehicle is almost stopped, and hence it can be certainly determined that the hydraulic travelling vehicle is almost stopped.
Furthermore, it is suitable that in the travel control S apparatus of the hydraulic travelling vehicle, the controller determines that the hydraulic travelling vehicle is almost stopped by also detecting that an accelerator pedal is not depressed. According to this constitution, the controller determines that the hydraulic travelling vehicle is almost 10 stopped by also detecting that the accelerator pedal is not depressed, and consequently it can be more certainly determined that the hydraulic travelling vehicle is almost stopped. 15 Brief Description of the Drawings
FIG. 1 is a system block diagram of a travel control apparatus according to an embodiment of the present invention.
20 Best Mode for Carrying out the Invention
A travel control apparatus of a hydraulic travelling vehicle according to an embodiment of the present invention will be explained with reference to the drawing. FIG. 1 is a 25 system block diagram of the travel control apparatus.
As shown in FIG. 1, a travelling pump 12 which is a hydraulic pump for travelling is connected to an engine 11, and the travelling pump 12 is driven by the engine 11 and discharges pressure oil. The pressure oil discharged from the 5 travelling pump 12 is fed to a travelling motor 13 which is a hydraulic motor for travelling via a travel control valve 21 and an oil pressure swivel joint 15. The travelling motor 13 is connected to an input shaft of a transmission 14 and drives the transmission 14.
10 A travelling speed detecting pump 17 is provided for the transmission 14, and it rotates in proportion to the rotation of an output shaft (not shown) of the transmission 14. Pressure oil discharged from the travelling speed detecting pump 17 is fed to a travelling speed detecting motor 18 via the oil pressure 15 swivel joint 15. The travelling pump 12 is a variable displacement hydraulic pump and has travelling pump capacity control means 12C. The travelling motor 13 is a variable displacement hydraulic motor and has travelling motor capacity control means 13C.
20 Incidentally, a working vehicle (not shown) which is the hydraulic travelling vehicle includes lower travelling equipment (not shown) and an upper revolving superstructure (not shown). The upper revolving superstructure includes a working implement (not shown), and the oil pressure swivel 25 joint 15 is provided in a connecting part of the lower travelling
equipment and the upper revolving superstructure. The engine 11 and a controller 30 are provided at the upper revolving superstructure, and the transmission 14 is provided at the lower travelling equipment.
5 The transmission 14 is connected to a gear change valve 16 being gear change control means via the oil pressure swivel joint 15. The gear change valve 16 feeds pressure oil from a transmission pump (not shown) to the transmission 14 via the oil pressure swivel joint 15. The gear change valve 16 is 10 connected to the controller 30 and sends a pressure signal responsive to a gear change signal from the controller 30 to the transmission 14. The transmission 14 has, for example, two speed gears, that is, the first and second speed gears. When the transmission 14 is put in the first speed gear, the 15 transmission 14 is put in the first speed gear by oil pressure from the gear change valve 16. Moreover, when the transmission 14 is put in the second speed gear, the transmission 14 is put in the second speed gear by the oil pressure from the gear change valve 16, whereby its speed gear 20 can be fixed.
A counterbalance valve 41 is provided between a forward travel side circuit 46F and a reverse travel side circuit 46R which are connected to the travelling motor 13. The forward travel side circuit 46F is provided with a forward travel - 25 side check valve 42F, and the reverse travel side circuit 46R is
provided with a reverse travel side check valve 42R. A circuit diverging from a point between the forward travel side check valve 42F and the travelling motor 13 is connected to a port A of the counterbalance valve 41. A circuit diverging from a 5 point between the reverse travel side check valve 42R and the travelling motor 13 is connected to a port B of the counterbalance valve 41. The counterbalance valve 41 has a neutral position 41N, a forward travel side position 41F, and a reverse travel side position 41R which are shown in the drawing.
10 In the neutral position 41N, a circuit which includes a throttle 41C and connects the port A and the port B is provided, and supplies oil from the high-pressure side to the low-pressure side when the travelling motor 13 is reversely driven, thereby preventing cavitation.
15 In the forward travel side position 41F of the counterbalance valve 41, a circuit which includes a throttle 41FC and connects the port A and a port T of the counterbalance valve 41 is provided, and in the reverse travel side position 41R, a circuit which includes a throttle 41RC and connects the port B 20 and the port T of the counterbalance valve 41 is provided.
An end portion on the forward travel side position 41F side of the counterbalance valve 41 and a point between the forward travel side check valve 42F and the travel control valve 21 are connected by a circuit including a throttle 44F. An end 25 portion on the reverse travel side position 41R side of the
counterbalance valve 41 and a point between the reverse travel side check valve 42F and the travel control valve 21 are connected by a circuit including a throttle 44R. Thus, the switching between the neutral position 41N, the forward travel 5 side position 41F, and the reverse travel side position 41R is done by the pressure oil from the travelling pump 12. Check valves 45F and 45R are valves for preventing backflow of the pressure oil from the forward travel side circuit 46F and the reverse travel side circuit 46R. The port T of the 10 counterbalance valve 41 is connected to the forward travel side circuit 46F via a forward travel nonreturn valve 43F, and connected to the reverse travel side circuit 46R via a reverse travel nonreturn valve 43R.
A travelling motor capacity control valve 26 feeds the 15 pressure oil from the transmission pump to the travelling motor capacity control means 13C via the oil pressure swivel joint 15.
The travelling motor capacity control valve 26 is connected to the controller 30 and controls the capacity of the travelling motor 13 in response to a travelling motor capacity control 20 signal from the controller 30.
A vehicle speed detecting gear 35 for producing a vehicle speed signal is provided at an output shaft of the vehicle speed defecting motor 18, and is rotated by the vehicle speed detecting motor 18. For example, a predetermined 25 number of teeth, slits, and projections and depressions are -
formed on an outer circumference of the vehicle speed detecting gear 35. A vehicle speed detecting sensor 31 is provided in close vicinity of the outer circumference of the vehicle speed detecting gear 35, and outputs pulse, which occurs, for example, 5 when the predetermined number of teeth on the outer circumference of the vehicle speed detecting gear 35 pass through a signal detecting part of the vehicle speed detecting sensor 31, as an electric signal.
The vehicle speed detecting sensor 31 as vehicle speed 10 detecting means is connected to the controller 30 and sends a vehicle speed signal to the controller 30 as an electric signal.
The controller 30 performs operation processing of the vehicle speed signal to calculate the vehicle speed. A main relief valve 24 is provided in a discharge circuit of the travelling 15 pump 12, and relieves the pressure oil to an oil tank 25 when the pressure of the pressure oil discharged from the travelling pump 12 is a predetermined value or more.
The travel control valve 21 is switched from a neutral position N to a forward travel position F or a reverse travel 20 position R and controls the direction of the pressure oil discharged from the travelling pump 12 to send it to the travelling motor 13. The travel control valve 21 is switched from the neutral position N to the forward travel position F or the reverse travel position R by receiving travelling pilot - 25 pressure being pilot pressure from a forward and reverse travel
switching valve 22 at a forward travel side pressure receiving part 21F or a reverse travel side pressure receiving part 21R of the travel control valve 21. The forward and reverse travel switching valve 22 is switched to a forward travel position FK 5 in response to a forward travel signal from the controller 30 and switched to a reverse travel position RK in response to a reverse travel signal.
An accelerator pedal 23A is depressed to operate a travelling pilot pressure valve 23 to make it generate travelling 10 pilot pressure. The travelling pilot pressure, which is depressing amount detecting means of the accelerator pedal 23A, changes according to the depressing amount of the accelerator pedal 23A, and increases at a predetermined rate as the depressing amount of the accelerator pedal 23A increases. A 15 travelling pilot pressure sensor 32 is provided in a circuit between the travelling pilot pressure valve 23 and the forward and reverse travel switching valve 22, and the travelling pilot pressure sensor 32 sends a detected travelling pilot pressure signal to the controller 30.
20 A forward travelling pressure sensor 36 is provided in a circuit between the forward and reverse travel switching valve 22 and the forward travel side pressure receiving part 21F, and a reverse travelling pressure sensor 37 is provided in a circuit between the forward and reverse travel switching valve 22 and 25 the reverse travel side pressure receiving part 21 R. The -
forward travelling pressure sensor 36 sends a forward travel signal to the controller 30 when its internal switch is turned on by the travelling pilot pressure, and the reverse travelling pressure sensor 37 sends a reverse travel signal to the controller 5 30 when its internal switch is turned on by the travelling pilot pressure. A forward and reverse travel switch 34 is connected to the controller 30 and sends a forward travel command signal or a reverse travel command signal to the controller 30.
Upon receiving the vehicle speed signal as the electric 10 signal from the vehicle speed detecting sensor 31, the controller 30 sends a signal for reducing the capacity of the travelling motor 13 to the travelling motor capacity control valve 26 so that the capacity of the travelling motor 13 can be reduced to allow higher-speed travelling according to the vehicle speed, 15 for example, according as the vehicle speed increases. In response to this signal, the travelling motor capacity control valve 26 operates the travelling motor capacity control means 13C to reduce the capacity of the travelling motor 13. Upon receiving the travelling pilot pressure signal detected by the 20 travelling pilot pressure sensor 32, the controller 30 calculates the depressing amount of the accelerator pedal 23A according to the magnitude of the travelling pilot pressure signal.
The controller 30 performs operation processing of the vehicle speed signal which is the electric signal detected by the 25 vehicle speed detecting sensor 31 to calculate the vehicle speed.
The controller 30 then performs operation processing of a variation with time of the vehicle speed, and when the vehicle speed is a predetermined speed or lower (for example, 2 km/in or lower) for a predetermined time (for example, for one second), 5 it determines that the vehicle is stopped or almost stopped.
The controller 30 then.outputs a shift-down signal to the gear change valve 16, and outputs a capacity increasing signal, for example, a capacity increasing signal for maximizing the capacity of the travelling motor 13 to the travelling motor 10 capacity control valve 26. Incidentally, when determining that the vehicle is stopped, according to need, the controller 30 may i) output the shift-down signal to the gear change valve 16, ii) output the capacity increasing signal to the travelling motor capacity control valve 26, or iii) output the shift-down signal to 15 the gear change valve 16 and output the capacity increasing signal to the travelling motor capacity control valve 26.
Moreover, according to need, the controller 30 may add a state in which the acceleration pedal 23A is not depressed to determinants. More specifically, when i) the travelling pilot 20 pressure signal detected by the travelling pilot pressure sensor 32 is a predetermined pressure or lower, or both the travelling forward pilot pressure switch 36 and the travelling reverse pressure switch 37 are off, and the accelerator pedal 23A is not depressed, and ii) the vehicle speed of the vehicle is the 25 predetermined speed or lower as described above, the controller
30 can determine that the vehicle is stopped. In such a case, the controller 30 may i) output the shift-down signal to the gear change valve 16, ii) output the capacity increasing signal to the travelling motor capacity control valve 26, or iii) output the 5 gear shift-down signal to the gear change valve 16 and output the capacity increasing signal to the travelling motor capacity control valve 26.
Next, an operation of the travel control apparatus of the hydraulic travelling vehicle of the present invention will be 10 explained. When an operator switches the forward and reverse travel switch 34 to the forward travel side, the forward and reverse travel switching valve 22 is switched to the forward travel position FK. When the operator depresses the accelerator pedal 23A, the travelling pilot pressure is exerted 15 on the forward travel side pressure receiving part 21F of the travel control valve 21, and thereby the travel control valve 21 is switched from the neutral position N to the forward travel position F. The forward travelling pressure sensor 36 sends the forward travel signal to the controller 30 when its internal 20 switch is turned on by the travelling pilot pressure.
The controller 30 first sends a forward first speed signal, which is a gear change signal, to the gear change valve 16 by the forward travel command signal of the forward and reverse travel switch 34 and a speed gear signal set by a speed gear 25 lever (not shown), for example, the first speed. The gear
change valve 16 sends an oil pressure signal of the forward first speed to the transmission 14 to change the transmission 14 to the forward first speed gear.
The travel control valve 21 feeds the pressure oil 5 discharged from the travelling pump 12 to a forward travel side port 13F on the inlet side of the travelling motor 13 via the oil pressure swivel joint 15. The pressure oil of the forward travel side circuit 46F enters the end portion on the forward travel side position 41F side of the counterbalance valve 41 via 10 the throttle 44F to thereby switch the counterbalance valve 41 from the neutral position 41N to the forward travel side position 41F. The oil pressure let out from a reverse travel side port 13R on the outlet side of the travelling motor 13 enters the port A of the counterbalance valve 41 from the 15 reverse travel side circuit 46R and returns to the oil tank 25 via the throttle 41FC, the port T. the check valve 43, the oil pressure swivel joint 15, and the travel control valve 21. The travelling motor 13 then rotates in a forward travel direction and drives the transmission 14, so that the working vehicle 20 travels forward.
When the vehicle speed increases, and the operator selects the second speed by the speed gear lever for high-speed travelling, the controller 3() sends a forward second speed signal as the gear change signal to the gear change valve 16.
25 The gear change valve 16 sends an oil pressure signal of the
forward second speed to the transmission 14 to change the transmission 14 to the forward second speed gear. When detecting that vehicle speed becomes high by a vehicle speed signal from the vehicle speed sensor 31, the controller 30 sends S a signal for minimizing the capacity of the travelling motor 13 to the travelling motor capacity control valve 26. The travelling motor capacity control valve 26 operates the travelling motor capacity control means 13C to minimize the capacity of the travelling motor 13.
10 It is assumed that the working vehicle travels at high speed, and when it travels an upward sloping road, the operator releases the accelerator pedal 23A and depresses the brake (not shown) to stop the working vehicle in the middle of the sloping road. When the brake is released for another travelling, the 15 speed gear of the transmission 14 is the second speed, and the capacity of the travelling motor 13 is made minimum.
Moreover, since the accelerator pedal 23A is not depressed, the travelling pilot pressure does not occur, and the travel control valve 21 is in the neutral position N. whereby the pressure oil is 20 not supplied to the travelling motor 13. Hence, the travelling motor control valve 41 is in the neutral position 41N.
During this time, the controller 30 detects a state in which "the travelling pilot pressure signal produced by depressing the accelerator pedal 23A and detected by the 25 trave]ling pilot pressure sensor 32" has a predetermined
pressure or lower, that is, the accelerator pedal 23A is not depressed. Further, the controller 30 performs operation processing of the vehicle speed signal which is the electric signal detected by the vehicle speed detecting sensor 31 to S calculate the vehicle speed. When, in the state in which the travelling pilot pressure signal has the predetermined pressure or lower and the accelerator pedal 23A is not depressed, operation processing of the variation with time of the vehicle speed is performed, and as a result, the vehicle speed is the 10 predetermined speed or lower (for example, 2 km/in or lower) for the predetermined time (for example, for one second), the controller 30 determines that the vehicle is stopped. The controller 30 then outputs the shift-down signal to the gear change valve 16, and outputs the capacity increasing signal, for 15 example, the capacity increasing signal for maximizing the capacity of the travelling motor 13 to the travelling motor capacity control valve 26.
The gear change valve 16 which has received the shift-down signal sends the oil pressure signal of the first speed 20 to the transmission 14 to shift down the transmission 14 to the first speed gear. The travelling motor capacity control valve 26 which has received the capacity increasing signal operates the travelling motor capacity control means 13 to maximize the capacity of the travelling motor 13.
25 The working vehicle tries to slip down the sloping road, -
thereby its wheels are driven, and hence the travelling motor 13 is reversely driven through the transmission 14. However, the reduction ratio of the transmission 14 is increased because of shift down, and in this case, it is made maximum because the 5 transmission 14 is put in the first speed gear. Therefore, the reverse driving force of the wheels is reduced by the reduction ratio of the transmission 14, and the capacity of the travelling motor 13 is made maximum, whereby the rotation speed of the travelling motor is in a lower range. Moreover, by the reverse 10 driving, the pressure oil from the travelling motor 13 passes through the travelling motor throttle valve 41C in the neutral position 41N of thecounterbalance valve 41 connecting the inlet side and the outlet side of the travelling motor 13.
Consequently, pressure loss of the oil pressure occurs, whereby 15 the rotational resistance caused by the reverse driving increases, and hence the reverse rotation speed of the travelling motor 13 can be kept in a lower range. Accordingly, the reverse driving force of the travelling motor 13, which is caused because the working vehicle slips down the sloping road, becomes maximum 20 and a large resistance, and consequently, the slip-down speed of the working vehicle can be kept at a sufficiently low speed.
When determining that the accelerator pedal 23A is not depressed and that the working vehicle is stopped, the controller 30 may only output the shift-down signal to the gear 25 change valve 16. In this case, the reduction ratio of the -
transmission is made maximum, even if the wheels try reverse driving because the working vehicle tries to slip down the sloping road, and hence the reverse driving force of the wheels is reduced by the reduction ratio of the transmission, and force 5 for reversely driving the travelling motor reduces. Therefore, the rotation speed of the travelling motor lowers, and thus the slip-down speed can be kept in a lower range. Moreover, the controller 30 may only output the capacity increasing signal to the travelling motor capacity control valve 26. Also in this 10 case, the wheels try reverse driving because the working vehicle tries to slip down the sloping road, but since the capacity of the travelling motor 13 is made maximum, the travelling motor 13 rotates only at a low rotation speed, and besides the rotational resistance inside the travelling motor 13 15 increases, whereby the slip-down speed can be kept in a lower range. When determining that the working vehicle is stopped without determining that the accelerator pedal 23A is not depressed, the controller 30 i) may only output the shift-down 20 signal to the gear change valve 16, ii) may only output the capacity increasing signal to the travelling motor capacity control valve 26, or iii) may output the shift-down signal to the gear change valve 16 and output the capacity increasing signal to the travelling motor capacity control valve 26. In any case, - 25 the same effects as above can be obtained.
Incidentally, explanation is made with the transmission 14 including two speed gears of the first and second speed gears as an example, but a transmission having three speed gears of the first, second, and third speed gears, or a transmission 5 having a plurality of speed gears more than these, for example, a transmission with four speed gears further including the fourth speed gear or a transmission with five speed gears further including the fifth speed gear is also usable. The aforementioned shift-down performed when it is determined 10 that the working vehicle is stopped may be shift-down of the speed gear in the current state by one speed gear (for example, from the third speed to the second speed), or may be direct shift-down from the third speed to the first speed at which the maximum reduction ratio is obtained. The hydraulic 15 travelling vehicle may be a vehicle without an upper revolving superstructure, and the present invention can be also applied to, for example, a wheel loader, a forklift. or other working vehicles. Incidentally, when the travel control apparatus of the present invention is applied to the vehicle without the upper 20 revolving superstructure, it is suitable to remove the oil pressure swivel joint 15.
-

Claims (6)

WHAT IS CLAIMED IS:
1. A travel control apparatus of a hydraulic travelling vehicle including a travelling hydraulic motor and a 5 transmission whose speed gear is allowed to be fixed, comprising: gear change control means of said transmission; vehicle speed detecting means for detecting vehicle speed of said hydraulic travelling vehicle; and 10 a controller which sends a shift-down signal to said gear change control means to shift down said transmission when it is determined by the detected vehicle speed that said hydraulic travelling vehicle is almost stopped.
15
2. A travel control apparatus of a hydraulic travelling vehicle including a variable displacement travelling hydraulic motor, comprising: motor capacity control means of said variable displacement travelling hydraulic motor; 20 vehicle speed detecting means for detecting vehicle speed of said hydraulic travelling vehicle; and a controller which sends a capacity increasing signal to said motor capacity control means to increase a capacity of said variable displacement travelling hydraulic motor when it is 25 determined by the detected vehicle speed that said hydraulic -
travelling vehicle is almost stopped.
3. A travel control apparatus of a hydraulic travelling vehicle including a variable displacement travelling hydraulic 5 motor and a transmission whose speed gear is allowed to be fixed, comprising: gear change control means of said transmission; motor capacity control means of said variable displacement travelling hydraulic motor; 10 vehicle speed detecting means for detecting vehicle speed of said hydraulic travelling vehicle; and a controller which sends a shift-down signal to said gear change control means to shift down said transmission and sends a capacity increasing signal to said motor capacity control 15 means to increase a capacity of said variable displacement travelling hydraulic motor when it is determined by the detected vehicle speed that said hydraulic travelling vehicle is almost stopped.
20
4. The travel control apparatus of the hydraulic travelling vehicle according to any one of Claims 1 to 3,
wherein travelling motor throttle valves are provided in a circuit connecting an inlet side and an outlet side of said travelling hydraulic motor when said travelling hydraulic motor 25 is driven by rotation of wheels of said hydraulic travelling
l vehicle.
5. The travel control apparatus of the hydraulic travelling vehicle according to any one of Claims 1 to 4, 5 wherein said controller determines that said hydraulic travelling vehicle is almost stopped when the detected vehicle speed is a predetermined speed or lower for a predetermined time. 10
6. The travel control apparatus of the hydraulic travelling vehicle according to any one of Claims 1 to 5, wherein said controller determines that said hydraulic travelling vehicle is almost stopped by also detecting that an accelerator pedal is not depressed.
GB0227629A 2002-11-27 2002-11-27 Travel control apparatus of hydraulic travelling vehicle Expired - Fee Related GB2395989B (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
GB0227629A GB2395989B (en) 2002-11-27 2002-11-27 Travel control apparatus of hydraulic travelling vehicle
JP2003385169A JP2004176918A (en) 2002-11-27 2003-11-14 Running control device for hydraulic running vehicle
DE10354194A DE10354194B4 (en) 2002-11-27 2003-11-20 Driving control device of a hydraulic vehicle
FR0313606A FR2847525B1 (en) 2002-11-27 2003-11-20 DISPLACEMENT CONTROL DEVICE FOR HYDRAULIC MOBILE VEHICLE
CNA2003101180516A CN1506598A (en) 2002-11-27 2003-11-24 Running control apparatus for oil hydraulic running vehicle

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0227629A GB2395989B (en) 2002-11-27 2002-11-27 Travel control apparatus of hydraulic travelling vehicle

Publications (3)

Publication Number Publication Date
GB0227629D0 GB0227629D0 (en) 2003-01-08
GB2395989A true GB2395989A (en) 2004-06-09
GB2395989B GB2395989B (en) 2007-02-07

Family

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GB0227629A Expired - Fee Related GB2395989B (en) 2002-11-27 2002-11-27 Travel control apparatus of hydraulic travelling vehicle

Country Status (5)

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JP (1) JP2004176918A (en)
CN (1) CN1506598A (en)
DE (1) DE10354194B4 (en)
FR (1) FR2847525B1 (en)
GB (1) GB2395989B (en)

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Also Published As

Publication number Publication date
DE10354194B4 (en) 2011-12-29
JP2004176918A (en) 2004-06-24
DE10354194A1 (en) 2004-06-09
GB0227629D0 (en) 2003-01-08
GB2395989B (en) 2007-02-07
FR2847525B1 (en) 2009-03-06
FR2847525A1 (en) 2004-05-28
CN1506598A (en) 2004-06-23

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Effective date: 20131127