Source: http://www.google.com/patents/US7613560?ie=ISO-8859-1&dq=7,177,838
Timestamp: 2014-10-23 15:26:52
Document Index: 602071173

Matched Legal Cases: ['art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 4']

Patent US7613560 - Speed control structure and method for work vehicle - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA speed control structure for a work vehicle comprises: a speed change operating element for manipulation by an operator; a device for detecting operated position of the speed change operating element; a continuously variable speed change device that receives power from an engine of the work vehicle;...http://www.google.com/patents/US7613560?utm_source=gb-gplus-sharePatent US7613560 - Speed control structure and method for work vehicleAdvanced Patent SearchPublication numberUS7613560 B2Publication typeGrantApplication numberUS 11/517,193Publication dateNov 3, 2009Filing dateSep 7, 2006Priority dateSep 30, 2005Fee statusPaidAlso published asCN1940353A, CN100501196C, US20070137338Publication number11517193, 517193, US 7613560 B2, US 7613560B2, US-B2-7613560, US7613560 B2, US7613560B2InventorsEiji Nishi, Keishiro Nishi, Atsushi Shinkai, Yasunobu NakataniOriginal AssigneeKubota CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (16), Referenced by (8), Classifications (29), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetSpeed control structure and method for work vehicleUS 7613560 B2Abstract A speed control structure for a work vehicle comprises: a speed change operating element for manipulation by an operator; a device for detecting operated position of the speed change operating element; a continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting device for detecting a speed change operation position of the continuously variable speed change device; operating device for speed-shifting the continuously variable speed change device; control device for controlling the operating means, wherein the control means: sets a target speed change operating position based on detected information by the operated position detection device and a predetermined correlation data that correlates the operated position of the speed change operating element and the speed change operation position of the continuously variable speed change device, and calculates a deviation between the target speed change operating position and of the continuously variable speed change device and the actual speed change operation position based on the set target speed change operating position and detected information from the speed change position detecting device, and sets a target operating speed for the continuously variable speed change device based on the calculated deviation and a further correlation data that correlates the deviation with an operating speed at which the continuously variable speed change device is operated, and controls the operating means such that the continuously variable speed change device is operated toward the target speed change operating position and at the target operating speed.
(a) sets a target speed change operating position based on detected information by the operated position detection means and a predetermined correlation data that correlates the operated position of the speed change operating element and the speed change operation position of the continuously variable speed change device, and
(b) calculates a deviation between the target speed change operating position of the continuously variable speed change device and an actual speed change operation position based on the set target speed change operating position and detected information from the speed change position detecting mean, and
(c) sets a target operating speed for the continuously variable speed change device based on the calculated deviation and a further correlation data that correlates the deviation with an operating speed at which the continuously variable speed change device is operated, and
(d) controls the operating means such that the continuously variable speed change device is operated toward the target speed change operating position and at the target operating speed.
2. A speed control structure according to claim 1, wherein
3. A speed control structure according to claim 1, wherein
4. A speed control structure according to claim 1, wherein
5. A speed control structure for a work vehicle comprising:
control means for controlling the operating means, wherein the control means sets a target speed change operating position based on detected information by the maintained position detecting means and detected information by the speed change position detecting means and based on correlation data that correlates the maintained position with the speed change operation position and
6. A speed control structure according to claim 5, wherein
7. A method for controlling a speed of a work vehicle, the work vehicle having a speed change operating element for manipulation by an operator, means for detecting operated position of the speed change operating element, a continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting means for detecting a speed change operation position of the continuously variable speed change device; operating means for speed-shifting the continuously variable speed change device; control means for controlling the operating means, the method comprising the steps of:
calculates a deviation between the target speed change operating position of the continuously variable speed change device and an actual speed change operation position based on the set target speed change operating position and detected information from the speed change position detecting mean, and
11. A method for controlling a speed of a work vehicle, the work vehicle having a speed change operating element that configured to automatically return to a zero speed position; means for detecting operated position of the speed change operating element; constant speed operating element configured to be able to be maintained at any operated position; means for detecting maintained position of the constant speed operating element; a continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting means for detecting a speed change operation position of a speed change operating member of the continuously variable speed change device; operating means for operating the speed change operating member; control means for controlling the operating means, the method comprising the steps of:
setting a target operating speed based on correlation data that correlates a deviation between an actual speed change operation position detected by the speed change position detecting means and the target speed change operating position, with an operating speed at which the speed change control member is operated; and
BACKGROUND OF THE INVENTION The present invention is directed to a speed control structure and the control method for a work vehicle.
Such a work vehicle usually has, among other things, a speed change operating element for manipulation by an operator, means for detecting operating position of the speed change operating element, continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting means for detecting a speed change operation position of the continuously variable speed change device; operating means for speed-shifting the continuously variable speed change device; control means for controlling the operating means.
There is a work vehicle with a mechanical servo control mechanism where the servo valve controls the servo cylinder that controls the swash plate of a variable displacement pump of a hydraulic type continuously variable speed change device to a position that corresponds to the operated position of a speed change pedal based on the pedal position detected by a valve control linkage and on the operated position of the swash plate of the pump detected by a control linkage. See, for example, JP11-91379. There is also a work vehicle with an electronic servo control where the control device controls flow of hydraulic fluid to a servo cylinder for the pump swash plate of a variable displacement pump such that the swash plate is operated to a position corresponding to the operated position of a speed change pedal based on the operated position detected by pedal sensor and the operated position of the swash plate detected by a swash plate sensor.
However, in the mechanical servo control mechanism or in the electronic servo control mechanism mentioned above, the swash plate controlled simply to move to a position corresponding to the operated position of the speed change pedal. Thus, the greater the deviation between the position corresponding to the operated position of the speed change pedal and the position of the swash plate, the greater the control delay tends to become, which results in a �feel� that may be improved and made it difficult to maintain high level of responsiveness.
SUMMARY OF THE INVENTION An object of the invention is to provide a speed control structure and method for work vehicle that facilitates improvement of performance such as responsiveness or feel.
(b) calculates a deviation between the target speed change operating position of the continuously variable speed change device and an actual speed change operation position based on the set target speed change operating position and detected information from the speed change position detecting means, and
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a tractor as an example of a work vehicle,
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The entire side view of the tractor as an example of a work vehicle is shown in FIG. 1. This tractor has a front frame 2 that supports the engine 1 via a vibration insulator, front wheels 3 supported to either side of the front frame 2, a transmission case 4 that also functions as a frame connected with the engine 1, and the rear wheels 5 provided to either side of the transmission case 4. The work vehicle has the operator's section 8 equipped with a steering wheel 6, the operator's seat 7, etc. above a transmission case 4. The tractor has several sensors as described below. These sensors are known and conventional such as rotation sensors, which can be of optical or magnetic type or otherwise, and will not be described in detail below.
Transmission case 4 is formed by connecting the four casing parts: the first casing part 4A that houses the main clutch 9 etc., the second casing part 4B that houses hydrostatic type continuously variable speed change device 10 etc., the third casing part 4C that houses operation clutch 14 etc., and the fourth casing part 4D that houses gear type speed change device 11 etc.
As shown in FIGS. 4-6, the servo control mechanism 25 has hydraulic pump cylinder 26 for continuously operating the pump swash plate 16A (an example of a operating means), a servo valve 27 which regulates flow of the hydraulic fluid to the hydraulic pump cylinder 26, a regulator valve 28 that maintains the hydraulic pressure to the serve valve 27 at a predetermined value, a pedal sensor (an example of an operation position detecting means) 29 which has a potentiometer to detect the operated position of the speed change pedal 24, and a swash plate sensor (an example of a speed change position detecting means) 30 which has a potentiometer which detects the operation position of pump swash plate 16A from the amount of operation of the pump cylinder 26, and a control device (an example of a control means) 31 which has a microcomputer to which detected information from the sensors such as the pedal sensor 29, the swash plate sensor 30, etc. are inputted.
The pump cylinder 26 is housed in the second casing part 4B with a forward travel decelerating spring 32 and reverse travel decelerating spring 33 that urge the swash plate 16A toward its neutral position. As hydraulic fluid is supplied to hydraulic chamber 34 for forward travel gear change, the pump swash plate 16A is operated to a forward travel speed-increase (or accelerating) direction against the urging force of the forward travel decelerating spring 32. As hydraulic fluid is supplied to the hydraulic chamber 35 for reverse travel speed changes, pump swash plate 16A is operated to a reverse travel speed-increase direction against the travel decelerating spring 33.
The servo valve 27 has an electromagnetic proportional valve 36 for forward travel to control a flow of hydraulic fluid to the hydraulic chamber 34 for forward travel of the pump cylinder 26 and an electromagnetic proportional valve 37 for reverse travel which controls a flow of the hydraulic fluid to the hydraulic chamber 35 for the reverse travel speed changes of the pump cylinder 26. The regulator valve 28 distributes the hydraulic fluid fed from supply pump 38 for power steering to operation clutch 14 and hydraulic power steering device 39 with pressure suitable for each operation. The supply oil path 41 to servo valve 27 is connected to the pressure port 28A of the regulator valve 28 to which the supply oil path 41 to operation clutch 14 is connected.
Control device 31 has at least a MPU, memory, and other known hardware required to perform communication function, and other functions and algorithms described in the specification. As shown in FIG. 6, the control device 31 has the map data (an example of correlation data) which correlates the operated position (or actuation position) of speed change pedal 24, with the operation position of pump swash plate 16A, and pump swash plate control means 31A which has the control program which operates pump swash plate 16A by controlling the operation of proportional valve 36 for forward travel, or proportional valve 37 for reverse travel based on the map data and detected information or signals from the pedal sensor 29, detected information from the swash plate sensor 30, etc.
That is, the servo control mechanism 25 is an electronically controlled type where the pump swash plate control means 31A controls the operation of proportional valve 36 for forward travel, or proportional valve 37 for reverse travel to operate the pump cylinder 26 in order to operate the pump swash plate 16A of the hydrostatic type continuously variable speed change device 10 based on detected information from pedal sensor 29, and detected information from swash plate sensor 30. The servo control mechanism 25 drives pump cylinder 26 directly with the output pressure of the proportional valve 36 for forward travel or proportional valve 37 for reverse travel which goes through pressure port 28A of regulator valve 28 (direct-acting type).
Each map data of the first operating speed setting means 31B correlates the deviation of pump swash plate 16A with the operating speed of pump swash plate 16A (refer to FIG. 8) such that when there is a large deviation between the actual operation position of pump swash plate 16A detected by swash plate sensor 30 and the target operation position of pump swash plate 16A determined by the pump swash plate control means 31A, the operating speed of the pump swash plate 16A becomes greater, and such that operating speed of pump swash plate 16A for a given deviation of the pump swash plate 16A in reverse travel is less than the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A in a forward travel.
The control device 31 has data change means 31C provided with the control program which changes the map data which the first operating speed setting means 31B uses. As described below, data change means 31C is set up such that the map data which the first operating speed setting means 31B uses is changed appropriately according to various situations.
The data change means 31C changes the map to be used to data which correlates the deviation of pump swash plate 16A with the operating speed of pump swash plate 16A such that the slower the operating speed of speed change pedal 24 is, the more gradually the pump swash plate 16A is operated, based on the detected information from the operating speed detection means 46 which detects the operating speed of speed change pedal 24, such that with a decrease in the operating speed of speed change pedal 24, the operating speed of the pump swash plate 16A for a given deviation of pump swash plate 16A becomes more gradual. The operating speed of speed change pedal 24 is obtained by differentiating the output of pedal sensor 29 with respect to time. Therefore, the detection means 46 is considered to have the pedal sensor 29 and the control device 31.
The data change means 31C changes the used map data which correlates the deviation of pump swash plate 16A with the operating speed of pump swash plate 16A based on the detected information from rotation sensor (an example of a load detection means) 47 which detects the engine rotational speed, and the target operation position of pump swash plate 16A set up by pump swash plate control means 31A, such that when the target operation position of pump swash plate 16A is set to the low speed side when the engine rotational speed is low, operation of pump swash plate 16A is performed quickly, such that, in response to the fall of the engine rotational speed, the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A becomes greater. The map data is changed such that when it is detected that the target operation position of pump swash plate 16A was set to the high speed side when the engine rotational speed is raising, the operation of pump swash plate 16A is performed gently so that the operating speed of pump swash plate 16A for a given deviation of the pump swash plate 16A becomes slow in response to the rise of the engine rotational speed.
The data change means 31C changes the map data which correlates the deviation of pump swash plate 16A with the operating speed of pump swash plate 16A based on detected information from the brake sensor (an example of a braking detecting means) 49 which has a potentiometer which detects the operation of brake mechanism (not shown) from the operation position of brake pedal 48 in the operator's station 8, such that when brake mechanism is carrying out the braking operation, operation to the decelerating direction of pump swash plate 16A is performed promptly such that the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A becomes greater, taking into consideration the fall of the vehicle speed by the braking operation of brake mechanism.
The data change means 31C changes the map data which correlates the deviation of pump swash plate 16A with the operating speed of pump swash plate 16A based on the detected information from the vehicle speed sensor (speed detecting means) 50 which detects the vehicle speed from the output rotational speed of gear type speed change device 11, such that when the vehicle speed is low, the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A is performed slowly so that operation of pump swash plate 16A is gradual in response to the fall of the vehicle speed.
The data change means 31C changes the map data which correlates the deviation of the pump swash plate 16A with the operating speed of the pump swash plate 16A based on detected information from the swash plate sensor 30, and the target operation position of pump swash plate 16A set by the pump swash plate control means 31A, such that when the target operation position of the pump swash plate 16A is set to the speed increase side relative to the actual operation position, operation of pump swash plate 16A is performed more gently, and such that when the target operation position of pump swash plate 16A is set to the slowdown side relative to the actual operation position, operation of pump swash plate 16A is performed promptly, and such that when the neutral position is between the target operation position of pump swash plate 16A and the actual operation position, operation of pump swash plate 16A is performed much more promptly.
The data change means 31C changes the map data which correlates the deviation of the pump swash plate 16A with the operating speed of pump swash plate 16A based on detected information from swash plate sensor 30, and the target operation position of the pump swash plate 16A set by the pump swash plate control means 31A such that at the start of the vehicle movement where the pump swash plate 16A is operated in the speed increase direction from the neutral position, the operation of pump swash plate 16A is performed gently, such that the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A becomes slower at the start of travel and such that when the vehicle is stopped where a slowdown operation of the pump swash plate 16A is carried out from a speed increase position to the neutral position, operation of the pump swash plate 16A is performed with greater speed, so that at the time of the vehicle stop, the operating speed of pump swash plate 16A for a given deviation of pump swash plate 16A becomes quicker.
Thus despite the deceleration operation of the speed change pedal 24 based on detected information from the pedal sensor 29, and detected information from the swash-plate sensor 30, when it is detected that deceleration operation of the pump swash plate 16A with the forward travel decelerating spring 32 or the reverse travel decelerating spring 33 is not performed, the pump swash plate control means 31A controls the actuation of the proportional valve 36 for forward travel or the proportional valve 37 for reverse travel on the side opposite to the side used to actuate the pump swash plate 16A to the present actuation position. Thus the pump cylinder 26 is forced to operate in the direction in which deceleration operation of the pump swash plate 16A is carried out toward the neutral position.
To solve this problem, as shown in FIG. 6, the control device 31 has the automatic pump swash plate control means 31D which changes the actuation position of the pump swash plate 16A based on the engine load.
As shown in FIGS. 6 and 9 (B), the automatic pump swash plate control means 31D has an operation program which computes the decrease amount (engine drop amount) from the set rotating speed of the engine rotational speed based on detected information from the setting rotation sensor (an example of a set-rotating-speed detection means) 52 which has a potentiometer which detects the set rotating speed of an engine 1 from the actuation position of the accelerator lever 51 in the operator's station 8, and on detected information from the rotation sensor 47, a plurality of map data (an example of correlation data) which correlates the engine rotational speed with the actuation position of the pump swash plate 16A, and, a control program which operates the pump swash plate 16A by controlling actuation of the proportional valve 36 for forward travel, or the proportional valve 37 for reverse travel based on the calculation result and the map data of the operation program.
Each map data of the automatic pump swash plate control means 31D is determined based on the engine stall performance line L. And the engine rotational speed and the actuation position of the pump swash plate 16A are correlated such that when the engine rotational speed falls to the predetermined engine rotation region h, the lower the rotation rate is, the closer the limit operation position is to the neutral position and such that the limit operation position of the pump swash plate 16A is not set at the neutral position (see FIG. 9 (B)).
To explain in more detail, as shown in FIG. 9 (B), in the first region h1 where the engine drop amount is small among the predetermined engine rotation regions, the engine rotational speed and the actuation position of the pump swash plate 16A are correlated such that the amount of change of the pump swash plate 16A is large for a given amount of change of the engine rotational speed.
The control program of the automatic pump swash plate control means 31D sets the actuation position of the pump swash plate 16A corresponding to the engine drop amount which the operation program computed as the limit operation position of the pump swash plate 16A based on the calculation result and map data of an operation program, and controls actuation of the proportional valve 36 for forward travel or the proportional valve 37 for reverse travel based on the set limit operation position and detected information from the swash-plate sensor 30, such that the limit operation position of the pump swash plate 16A comes to agreement with the actual actuation position.
The difference between FIG. 9B and FIG. 9C is that the vertical axis in FIG. 9C represents engine rotation rate. Max indicates the setting of the map data for large load and IDL indicates the setting for map data for light load.
With this control, a load control that prevents an engine stall due to overload can be performed during a loader operation where a front loader A is connected to the tractor or during a tilling operation where the tilling apparatus is connected to the tractor etc., even if the operator performs shift operation without consideration to an operation load etc. Thus, improvement in the response in the system may be expected.
The control program of the automatic pump swash plate control means 31D controls actuation of the proportional valve 36 for forward travel, or the proportional valve 37 for reverse travel such that the pump swash plate 16A is operated at the target operation speed set by the second operation speed setting means 31E. Thus, a good load control taking into consideration the rate of change of the engine rotational speed is possible. Despite changes in the rate of change of the engine rotational speed, driving comfort is maintained during a drop or increase in engine rotation speed. Moreover, deceleration operation of the pump swash plate 16A to lowering of the engine rotational speed can be performed with sufficient response, and the engine stall resulting from the actuation delay of the pump swash plate 16A can be prevented.
The rate of change detection means 53 has the rotation sensor 47, and the operation program of the second operation speed setting means 31E that computes the rate of change of the engine rotational speed based on detected information from the rotation sensor 47.
Depending on the gear ratio of the gear type speed change device 11 which is shifted to a low speed side when performing an operation with a larger load, the map data is set such that the lower the gear ratio is, the greater the operation speed of the pump swash plate 16A for a given rate of change of the engine rotational speed. Therefore, deceleration operation of the pump swash plate 16A can be promptly performed in response to a rapid reduction in engine rotational speed during an operation with a large load. As a result, the engine stall due to overload can be reliably prevented.
The switching mechanism 54 has a hydraulic cylinder 55 which operates the motor swash plate 17A, a changeover valve 56 which controls flow of the hydraulic fluid to this cylinder 55, an electromagnetic control valve 57 which operates this changeover valve 56, a high pressure selection valve 58 which enables feeding of the hydraulic fluid from the closed circuit 20 of the hydrostatic type continuously variable speed change device 10 to this control valve 57, a switching lever 59 arranged at the lower left position with respect to the steering wheel 6, a lever sensor 60 which has a switch which detects the actuation position of this switching lever 59, and motor swash-plate control means 31F which the control device 31 has as a control program which performs high-to-low switch actuation of the motor swash plate 17A based on detected information from this lever sensor 60.
When the switching lever 59 is operated to a low-speed position based on detected information from a lever sensor 60, the motor swash-plate control means 31F performs high-to-low switching control which switches the motor swash plate 17A from the high-speed position to the low-speed position, and turns on the corresponding indicating lamp 61. And, when the switching lever 59 is operated in a high-speed position, it performs low-to-high switching control which switches the motor swash plate 17A from the low-speed position to the high-speed position, and turns on the corresponding indicating lamp 62.
The motor swash-plate control means 31F stores the present actuation position of the pump swash plate 16A in the high-to-low switching control based on detected information from the swash-plate sensor 30, and calculates a slowdown target actuation position of the pump swash plate 16A, and controls actuation of the proportional valve 36 for forward travel or the proportional valve 37 for reverse travel so that deceleration operation of the pump swash plate 16A is carried out at a predetermined operation speed to the computed slowdown target actuation position. The means 31F controls the actuation of the proportional valve 36 or 37 and the control valve 57 such that after the pump swash plate 16A arrives at the slowdown target actuation position, an accelerated return of the pump swash plate 16A to the stored actuation position at the predetermined operation speed and the switch over operation of the motor swash plate 17A from the high speed position to the low speed position at a predetermined speed are perfumed simultaneously (see FIG. 10(A)).
Moreover, in the low-to-high switching control, based on detected information from the swash-plate sensor 30, the present actuation position of the pump swash plate 16A is stored, and the slowdown target actuation position of the pump swash plate 16A is computed. Actuation of the proportional valve 36 for forward travel or the proportional valve 37 for reverse travel and actuation of the control valve 57 are controlled such that deceleration operation of pump swash plate 16A to the computed slowdown target actuation position at the operation speed and switch actuation from a low-speed position to the high-speed position of the motor swash plate 17A at the operation speed are performed simultaneously. Afterward, actuation of the proportional valve 36 for forward travel or the proportional valve 37 for reverse travel is controlled so that the pump swash plate 16A is returned to the memorized actuation position at the predetermined speed. [See FIG. 10(B)]
That is, when switching the motor swash plate 17A to a low-speed position from a high-speed position, by performing not only the switching actuation but also accelerating actuation of the pump swash plate 16A simultaneously, the capacity variation in the variable capacity motor 17 generated by the switching actuation to the low-speed position of the motor swash plate 17A from a high-speed position can be offset by the capacity variation in the variable capacity pump 16 generated by accelerating actuation of the pump swash plate 16A. Moreover, when switching the motor swash plate 17A to a high-speed position from a low-speed position, by performing not only the switch actuation but also a deceleration operation of the pump swash plate 16A simultaneously, the capacity variation in the variable capacity motor 17 generated by the switching actuation to the high-speed position of the motor swash plate 17A from a low-speed position can be offset by the capacity variation in the variable capacity pump 16 generated in connection with the deceleration operation of the pump swash plate 16A. Therefore, the shift shock generated by a switching actuation of the motor swash plate 17A can be alleviated.
Also, the motor swash-plate control means 31F may be configured such that it performs the high-to-low switching control when traveling with the motor swash plate 17A switched to the high-speed position based on detected information from the pedal sensor 29, and detected information from the swash-plate sensor 30, irrespective of the deceleration operation of the speed change pedal 24, when it is detected that deceleration operation of the pump swash plate 16A with the forward travel decelerating spring 32 or the reverse travel decelerating spring 33 is not performed so that the high-to-low switching control can perform a deceleration operation if deceleration operation of the pump swash plate 16A is not carried out due to inertia during a trailer operation etc., despite the decelerating operation of the speed change pedal 24.
As shown in FIGS. 4-6, the control device 31 has an automatic motor swash-plate control means 31G as a control program. Automatic motor swash-plate control means 31G performs automatic high-to-low switching control which switches the motor swash plate 17A to the low-speed position from the high-speed position, and turns on the corresponding indicating lamp 61 when it is detected based on detected information from the pedal sensor 29 that the actuation position of the speed change pedal 24 is operated to the predetermined actuation position or the operation area, when the engine rotational speed is detected to have fallen to the low-to-high switch engine speed near a predetermined maximum torque output rotational frequency, or the low-to-high switch engine-speed region set for a given actuation position of the speed change pedal 24 based on the maximum torque output characteristic of an engine 1, and the engine drop amount computed by the operation program of the automatic pump swash plate control means 31D. The automatic motor swash-plate control means 31G also performs the automatic low-to-high switching control which switches the motor swash plate 17A to a high-speed position from a low-speed position, and turns on the corresponding indicating lamp 62, when it is detected based on an engine drop amount that the engine rotational speed went up to the low-to-high switch engine speed near a predetermined set rotating speed or the low-to-high switch engine-speed region, and when actuation of the speed change pedal 24 to the actuation position or operation area set up beforehand is detected based on detected information from the pedal sensor 29.
Also, in the low-to-high switching control of the automatic motor swash-plate control means 31G, the same control actuation as in the low-to-high switching control in the motor swash-plate control means 31F is performed, and the shift shock generated by low-to-high switch actuation of the motor swash plate 17A is alleviated. After switching the motor swash plate 17A to a high-speed position, this state is maintained for a predetermined time period (for example, for 2 seconds).
It is also possible to configure the automatic motor swash-plate control means 31G such that it performs the automatic high-to-low switching control which switches the motor swash plate 17A from the high-speed position to the low-speed position and turns on the corresponding indicating lamp 61, as the engine rotational speed is detected to have fallen to the low-to-high switch engine speed near a predetermined maximum torque output rotational speed, or to the low-to-high switch engine-speed region, based on the maximum torque output characteristics of the engine 1, and the engine drop amount computed by the operation program of the automatic pump swash plate control means 31D and such that it performs an automatic low-to-high switching control which switches the motor swash plate 17A from the low-speed position to a high-speed position, as the engine rotational speed is detected to have gone up to the low-to-high switch engine speed near predetermined set rotating speed, or to the low-to-high switch engine-speed region, based on an engine drop amount, and turns on the corresponding indicating lamp 62.
The control device 31 has mode change-over means 31H as a control program which switches the control mode performed based on actuation of the mode setting device 64 which has a normally open switch on the display panel 63. When an ON signal is inputted in connection with the pressing of the mode setting device 64, the mode change-over means 31H switches the transmission control mode between a manual-control mode, a semi-automatic-control mode, or a automatic-control mode and turns on an indicating lamps 65-67 corresponding to each control mode. In the manual-control mode, it performs the speed control using control actuation of the pump swash plate control means 31A and switching control using control actuation of the motor swash-plate control means 31F. In the semi-automatic-control mode, it performs the speed control which uses control actuation of the pump swash plate control means 31A, and a load control using control actuation of the automatic pump swash plate control means 31D, and a switching control using control actuation of the motor swash-plate control means 31F, such that priority may be given to load control as opposed to the speed control. In the automatic-control mode, the mode change-over means 31H performs a speed control which uses control actuation of the pump swash plate control means 31A, and a load control using control actuation of the automatic pump swash plate control means 31D, and the automatic switching control using control actuation of the automatic motor swash-plate control means 31G, such that priority is given to load control as opposed to speed control, and such that load control and automatic switching control are coordinated appropriately.
The pump swash plate 16A is operated based on the actuation position of the speed change pedal 24 etc., so as to arrive at the target actuation position corresponding to the actuation position of the speed change pedal 24 with target operation speed. And when a drop in engine speed occurs, based on an engine drop amount etc., it is operated so as to arrive at the limit operation position corresponding to an engine drop amount at the target operation speed, and the motor swash plate 17A is switched between the high and low positions based on actuation of the switching lever 59.
Moreover, when switch actuation to the low-speed position of the motor swash plate 17A based on actuation of the switching lever 59 is performed in the automatic-control mode, since it is impossible to perform switch actuation to the low-speed position of the motor swash plate 17A by automatic switching control, control mode switches from automatic-control mode to semi-automatic-control mode automatically.
As shown in FIGS. 6 and 11, the console panel 63 has the liquid-crystal-display device 69 where the display may be changed among a vehicle speed displaying mode, or a remaining fuel displaying mode, etc. based on actuation of the display change-over switch 68. This liquid-crystal-display device 69 displays the target actuation position 69A or the limit operation position 69B, and the current position 69C of the pump swash plate 16A which changes at every moment, when the pump swash plate position display mode is selected by actuation of the display change-over switch 68. That is, by selecting pump swash plate position display mode, the motion of the pump swash plate 16A can be checked easily.
As compared with the map data ordinarily used, the map data for implement lifting sets the actuation position of the pump swash plate 16A for a given actuation position of the speed change pedal 24 to a lower speed side. (See FIG. 7). Because the pump swash plate control means 31A uses this map data, the vehicle speed will be restricted to the low speed side and a high speed travel will be prevented when the implement is raised higher than a set height.
In addition, the element numbered 77, shown in FIGS. 4 and 12, is a link arm used in the electronics type servo control mechanism 25 as a feedback arm provided between the cylinder 26 for pumps, and the swash-plate sensor 30, and used, in the mechanical servo control mechanism 78, as an actuation/feedback combination arm provided between 4he cylinder 26 for pumps, and the operating shaft 73 to actuate the servo valve 74.
As shown in FIGS. 4 and 5, the switching mechanism 54 with the changeover valve 56, the control valve 57, and the high pressure selection valve 58 is formed as a one block unit of the control mechanism 84 by virtue of being housed by the casing 83 removably bolt-connected to the left side part of the second casing part 4B of the transmission case 4. The device can be changed from an adjustable motor specification to a fixed motor specification relatively simply by replacing the operating mechanism 84 with a plate 85 as shown in FIGS. 12 and 14 to cover connecting holes 86-91 formed in the surface with the operating mechanism 84 of the second casing part 4B and by replacing the variable capacity motor 17 in the second casing part 4B with the fixed capacity motor 92, and by removing the cylinder 55 for the motor.
As shown in FIG. 6, the end regions of the operation area of the speed change pedal 24 may be set as high-speed regions, and a region between the two ends as a low-speed region, and the motor swash-plate control means 31F may be arranged to control actuation of the control valve 57 based on detected information from the pedal sensor 29 such that when the speed change pedal 24 is operated to a low-speed region, the motor swash plate 17A switches to a low-speed position, and when the speed change pedal 24 is operated to a high-speed region, the motor swash plate 17A is located in a high-speed position to use the speed change pedal 24 also as an operating element for a high-low 2 position change-over of the variable capacity motor 17. The end regions of the operation area of the speed change pedal 24 may be set as a high-speed region, and the motor swash-plate control means 31F may be arranged to control actuation of the control valve 57 based on detected information from the pedal sensor 29 such that when the speed change pedal 24 is operated to a high-speed region, the motor swash plate 17A is switched to a high-speed position to use the speed change pedal 24 also as an operating element for a low-to-high switch of the variable capacity motor 17.
As shown in FIGS. 17 and 19, the cruise speed control means 31P has a map data which correlates the holding position of the cruise speed lever 143 with the shift operation position of the pump swash plate 16A, and a control program which controls actuation of the proportional valve 36 for forward travel based on the map data and detected information from a lever sensor 144 etc. The map data of the cruise speed control means 31P correlates the actuation position of the cruise speed lever 143 with the shift operation position of the pump swash plate 16A (refer to FIG. 19) such that the greater the operated amount of the cruise speed lever 143 from the neutral position (zero speed position) in the forward speed increase direction is, the greater the operation amount of the pump swash plate 16A from the neutral position in the direction of forward travel is.
The above-mentioned map data may be replaced with a correlation equation that correlates the actuation position of the cruise speed lever 143 with the shift operation position of the pump swash plate 16A. The control program of the cruise speed control means 31P sets the shift operation position of the pump swash plate 16A corresponding to the holding position of the cruise speed lever 143 which the lever sensor 144 detected as the target actuation position of the pump swash plate 16A based on the stored map data and detected information from a lever sensor 144, and controls the actuation of the proportional valve 36 for forward travel based on the set target actuation position and detected information from the swash-plate sensor 30, so that the target actuation position of the pump swash plate 16A come into agreement with the actual shift operation position.
As shown in FIG. 17, the control means 31 has a third operation speed setting means 31J for setting the operation speed during a speed change to the speed according to the holding position of the cruise speed lever 143. As shown in FIGS. 17 and 18, the third, operation speed setting means 31J has an operation program which computes the deviation of the target actuation position of the pump swash plate 16A, and a actual shift operation position based on the target actuation position of the pump swash plate 16A set by the cruise speed control means 31P, and detected information from the swash-plate sensor 30, a plurality of map data as correlation data which correlates the deviation of the target actuation position of the pump swash plate 16A and the actual shift operation position with the operation speed of the pump swash plate 16A, and a control program which sets the target operation speed of the pump swash plate 16A based on those map data and calculation results of an operation program.
Each map data of the third operation speed setting means 31J correlates the deviation of the pump swash plate 16A with the operation speed of the pump swash plate 16A such that when the deviation of the actual shift operation position of the pump swash plate 16A detected by the swash-plate sensor 30 and the target actuation position of the pump swash plate 16A set by the cruise speed control means 31P is large, the operation speed of the pump swash plate 16A is large, and such that the operation speed of the pump swash plate 16A by control actuation of the cruise speed control means 31P becomes slower than the operation speed of the pump swash plate 16A by control actuation of the speed change control means 31A (dashed line in FIG. 18).
The above-mentioned map data may be replaced by the correlation equation as correlation data that correlates the deviation of the target actuation position of the pump swash plate 16A and the actual shift operation position, with the operation speed of the pump swash plate 16A.
The control program of the third operation speed setting means 31J sets the operation speed of the pump swash plate 16A corresponding to the deviation of the computed pump swash plate 16A as the target operation speed of the pump swash plate 16A, based on the stored map data and the calculation result of an operation program, and outputs the set target operation speed to the cruise speed control means 31P.
The control program of the cruise speed control means 31P is arranged to control actuation of the proportional valve 36 for forward travel so that the pump swash plate 16A is operated at the target operation speed set by the third operation speed setting means 31J. With this control, the operation speed during shift operation of the pump swash plate 16A by actuation of the cruise speed lever 143 becomes slower than the operation speed when operating the pump swash plate 16A by actuation of the speed change pedal 24. As a result, while improving response in shift operation by the speed change pedal 24, rapid change in the vehicle speed by actuation of the cruise speed lever 143 can be prevented thus making cruise speed setting operation by the cruise speed lever 143 easy to perform.
As shown in FIG. 17, the control device 31 has, as control programs, actuation change-over means 31K which switches the control means to operate, notifying device change-over means 31G which switches the operating state of the notifying device 145 which has a lamp in the operator's station 8, and cruise speed control stop means 31M to stop control actuation of the cruise speed control means 31P.
The notifying device change-over means 31L performs the following control. The notifying device 145 is switched off based on detected information from the pedal sensor 29, or detected information from a lever sensor 144, etc., when the cruise speed lever 143 is detected to be located in the neutral position, and when a step in operation of the speed change pedal 24 is detected with the cruise speed lever 143 being detected to be located in the neutral position. The notifying device 145 is turned on based on detected information from the pedal sensor 29, detected information from a lever sensor 144, etc., when the shift operation position of the pump swash plate 16A corresponding to the holding position of the cruise speed lever 143 is detected to be on the acceleration side than the shift operation position of the pump swash plate 16A corresponding to the actuation position of the speed change pedal 24. The notifying device 145 is made to blink (turned on and off in succession), based on detected information from the pedal sensor 29, detected information from a lever sensor 144, etc., while the cruise speed lever 143 is detected to be located in the actuation position away from the neutral position, and the shift operation position of the pump swash plate 16A corresponding to the actuation position of the speed change pedal 24 is detected to be at the shift operation position of the pump swash plate 16A corresponding to the holding position of the cruise speed lever 143 or on the accelerating side with respect to the shift operation position.
The notifying device 145 is turned off also in this case to notify that the system is in the normal traveling condition. If a pivoting operation is pivoted in the accelerating direction of the cruise speed lever 143 with the speed change pedal 24 located in the neutral position, the pump swash plate 16A will be shifted to the shift operation position to the forward accelerating travel side corresponding to the holding position of the cruise speed lever 143, and a vehicle body will carry out a cruise speed forward travel at the speed set by the shift operation position. In this case, the notifying device 145 is turned on to notify that the system is in the cruise speed forward condition under control of the cruise speed control. means 31P.
If the cruise speed lever 143 is pivoted to the accelerating direction during a forward travel by actuation of the speed change pedal 24, the vehicle body moves forward at a speed corresponding to the actuation position of the speed change pedal 24 until the target actuation position (target actuation position of the cruise speed control means 31P) of the pump swash plate 16A set by control of the cruise speed control means 31P is on the accelerating side with respect to the target actuation position (target actuation position in the speed change control means 31A) of the pump swash plate 16A set by control of the speed change control means 31A. During this time, the notifying device 145 goes out to notify that the system is in a normal traveling condition. At this point in time, if the target actuation position in the cruise speed control means 31P is on an accelerating side rather than the target actuation position in the speed change control means 31A by a pivoting operation to the accelerating direction of the cruise speed lever 143, or the deceleration operation of the speed change pedal 24, the vehicle body moves forward at the speed according to the actuation position of the cruise speed lever 143, resulting in the cruise speed travel according to the holding position of the cruise speed lever 143.
In this case, the notifying device 145 blinks to notify that the system is in the accelerating precedence condition where priority is given to the shift operation by control of the speed change control means 31A in the cruise speed forward condition by control of the cruise speed control means 31H. At this time, if the target actuation position in the speed change control means 31A comes to be on a slowdown side with respect to the target actuation position in the cruise speed control means 31P by the deceleration operation of the speed change pedal 24, the vehicle will carry out cruise speed traveling at the speed according to the holding position of the cruise speed lever 143 again.
The normally closed switch 148 is held in the open condition by pressing operation by both bent links 149 in the non-braking state where both side brake pedals 147 are not actuated [see FIG. 20]. During the braking turning state where one of the side brake pedals 147 is pressed down, the circuit is kept open by the pressing operation by the bent link 149 connected to the side brake pedal 147 which is not actuated [see FIG. 21(A)].
In the braking state where both side brake pedals 147 are actuated, the circuit returns to a closed state due to the fact that neither of the two bent links 149 are pressing down on the switch [see FIG. 21(B)].
When shift operation of the pump swash plate 16A is performed by the electronic type servo control mechanism 25 as shown in FIG. 24, a hysteresis will occur between the actuation position of the pump swash plate 16A, and a servo pressure (operating physical force to the pump swash plate 16A). Therefore, when shift operation of the pump swash plate 16A is performed by control actuation of the speed change control means 31A based on actuation of the speed change pedal 24 without taking this hysteresis into consideration, when switching between the acceleration operation and the decelerating by the speed change pedal 24 is performed, the difference of the servo pressure at the time of the accelerating actuation to the current position of the pump swash plate 16A, and the servo pressure at the time of deceleration operation by the hysteresis causes the pump swash plate 16A to be maintained despite an actuation of the speed change pedal 24 in a current position until the difference is canceled by actuation of the servo control mechanism 25 based on actuation of the speed change pedal 24.
That is, in the shift operation of an actuation by the speed change pedal 24, the response of the pump swash plate 16A will fall, and the operator may feel the adverse effect. To this end, as shown in FIG. 17, the control device 31 has the compensation means 31Q which compensates for the difference between the servo pressure at the time of the accelerating actuation to the current position of the pump swash plate 16A and the servo pressure at the time of deceleration operation when the acceleration or deceleration operation by the speed change pedal 24.
Based on detected information from the pedal sensor 29, the operation program of the compensation means 31Q detects the current position θ of the speed change pedal 24 and computes operation speed ω and predicts the actuation position β(=θ+ωt) of the speed change pedal 24 after a fixed time from those detection results and calculation results. As the correlation data of the compensation means 31Q has a value (average value) Δi of the difference of the current value Ia supplied to a servo valve 27 at the time of accelerating actuation, and the current value Ib supplied to a servo valve 27 at the time of deceleration operation for a given actuation position of the pump swash plate 16A, which is required to compensate for the difference Δf between the servo pressure Fa at the time of the accelerating actuation and the servo pressure Fb at the time of deceleration operation for a given actuation position of the pump swash plate 16A.
The control program of the compensation means 31Q compares the predicted actuation position β, which is the calculation result of the operation program, with the current position θ, and controls actuation of the servo valve 27 so that the difference Δf of the servo pressure Fa at the time of the accelerating actuation and the servo pressure Fb at the time of deceleration operation for the current position of the pump swash plate 16A is compensated based on the correlation data, when the difference becomes beyond the predetermined setting α.
More specifically, when the switch to forward travel deceleration operation from forward travel accelerating actuation of the speed change pedal 24 is detected based on detected information from the pedal sensor 29, the current position θ of the obtained speed change pedal 24 is compared with the predicted actuation position β, which is a calculation result of the operation program. When the difference becomes greater than the predetermined value (β<θ−α), in order to decrease the servo pressure F corresponding to the current position of the pump swash plate 16A promptly from the servo pressure Fa at the time of accelerating actuation to the servo pressure Fb at the time of deceleration operation, the current is lowered at once to the current value Ib for obtaining the servo pressure Fb at the time of the deceleration operation corresponding to the current position of the pump swash plate 16A by subtracting the difference value Δi from the current value Ia for obtaining the servo pressure Fa at the time of the accelerating actuation corresponding to the current position of the pump swash plate 16A.
When the switch to the forward travel accelerating actuation from the forward travel deceleration operation of the speed change pedal 24 is detected based on detected information from the pedal sensor 29, the current position θ of the speed change pedal 24 obtained at that time is compared with the predicted actuation position β, which is the calculation result of an operation program. When the difference becomes greater than the predetermined value (β>θ−α) in order to increase the servo pressure F corresponding to the current position of the pump swash plate 16A promptly from the servo pressure Fb at the time of deceleration operation to the servo pressure Fa at the time of accelerating actuation, the current is raised at once to the current value Ia for obtaining the servo pressure Fa at the time of the accelerating actuation corresponding to the current position of the pump swash plate 16A by adding the difference value Δi to the current value Ib for obtaining the servo pressure Fb at the time of the deceleration operation corresponding to the current position of the pump swash plate 16A.
When a switch to reverse travel deceleration operation from reverse travel accelerating actuation of the speed change pedal 24 is detected based on detected information from the pedal sensor 29, the current position θ of the speed change pedal 24 obtained at that time is compared with the predicted actuation position β, which is a calculation result of an operation program. When the difference becomes greater than the predetermined setting (β<θ−α), in order to lower the servo pressure F corresponding to the current position of the pump swash plate 16A promptly from the servo pressure Fa at the time of accelerating actuation to the servo pressure Fb at the time of deceleration operation, the current is lowered at once to the current value Ib for obtaining the servo pressure Fb at the time of the deceleration operation corresponding to the current position of the pump swash plate 16A by subtracting the difference value Δi from the current value Ia for obtaining the servo pressure Fa at the time of the accelerating actuation corresponding to the current position of the pump swash plate 16A.
When switch to the reverse travel accelerating actuation from the reverse travel deceleration operation of the speed change pedal 24 is detected based on detected information from the pedal sensor 29, the current position θ of the speed change pedal 24 then obtained is compared with the predicted actuation position β, which is the calculation result of the operation program. When the difference becomes greater than the predetermined setting (β>θ−α), in order to increase the servo pressure F corresponding to the current position of the pump swash plate 16A promptly from the servo pressure Fb at the time of deceleration operation to the servo pressure Fa at the time of accelerating actuation, the current is increased at once to the current value Ia for obtaining the servo pressure Fa at the time of the accelerating actuation corresponding to the current position of the pump swash plate 16A by adding the difference value Δi to the current value Ib for obtaining the servo pressure Fb at the time of the deceleration operation corresponding to the current position of the pump swash plate 16A.
In the reverse travel accelerating actuation after switching to reverse travel acceleration from the reverse travel deceleration of the speed change pedal 24, the servo pressure Fb for the pump swash plate 16A rises promptly with actuation of the speed change pedal 24 to the servo pressure Fa at the time of the reverse travel accelerating actuation corresponding to the actuation position of the speed change pedal 24, which improves response in accelerating actuation of the pump swash plate 16A to the shift operation position for reverse travel corresponding to the actuation position of the speed change pedal 24.
The lower the temperature of the hydraulic fluid is, the greater the difference Δf of the servo pressure Fa at the time of the accelerating actuation to the actuation position of the pump swash plate 16A and the servo pressure Fb at the time of deceleration operation becomes. Accordingly, the hydraulic circuit to the cylinder 26 for pumps has the oil temperature sensor 43 which detects the temperature of the hydraulic fluid supplied to a regulator valve 28. And the compensation means 31Q takes into consideration of the fact that the lower the temperature of the hydraulic fluid supplied to a regulator valve 28 is, the greater the difference Δf of the servo pressure Fa at the time of the accelerating actuation to the actuation position of the pump swash plate 16A and the servo pressure Fb at the time of deceleration operation becomes. And the means 31Q is configured to change the difference value Δi between the current value Ia supplied to a servo valve 27 at the time of accelerating actuation and the current value Ib supplied to a servo valve 27 at the time of deceleration operation based on detected information from the oil temperature sensor 43.
To describe in more detail, the compensation means 31Q has the map data which correlates the temperature of the hydraulic fluid supplied to a regulator valve 28 with the correction coefficient which compensates the current difference value Δi. Map data correlates the temperature with the correction coefficient of hydraulic fluid such that the lower the temperature of hydraulic fluid is, the greater the value Δi of the difference of a current value becomes. And the control program of the compensation means 31Q selects the correction coefficient according to the temperature of the hydraulic fluid based on detected information from the map data and oil temperature sensor 43, and multiply the value Δi of the difference of a current value by the correction coefficient, so that the value Δi of the difference of a current value is amended to the proper value according to the temperature of the hydraulic fluid at that time.
That is, in response to the fact that, the lower the temperature of the hydraulic fluid supplied to the regulator valve 28 is, the greater the difference Δf of the servo pressure Fa at the time of the accelerating actuation to the actuation position of the pump swash plate 16A and the servo pressure Fb at the time of deceleration operation becomes. And the current difference value Δi is changed correspondingly to a larger value.
The commanding means issues a command to stop the control to the speed change control means 31A when the speed change pedal 24 is detected to be operated in the neutral position based on detected information from the pedal sensor 29, if the pump swash plate 16A is detected to have arrived at the setting position near the predetermined neutral position based on detected information from the swash-plate sensor 30, and if the vehicle speed is detected to have fallen to the low set speed set in advance, based on the output of the vehicle speed sensor (speed detecting means) 50 which detects the vehicle speed from the output rotation rate of the gear type speed change device 11.
When the pump swash plate 16A arrives at the setting position near the predetermined neutral position by this decelerating operation, it is determined whether the vehicle speed fell to the predetermined set speed. When it has not fell to a set speed, control actuation of the speed change control means 31A is continued.
And when the speed change pedal 24 arrives at a corresponding actuation position to the real neutral position of the pump swash plate 16A, the speed change control means 31A is ordered to start control. On the other hand, if it is detected that the speed change pedal 24 is operated in the direction opposite to the direction corresponding to the direction in which the real neutral position of the pump swash plate 16A is displaced with respect to the set neutral position of the pump swash plate 16A, the speed change control means 31A is ordered to initiate control. Thus, when accelerating actuation of the speed change pedal 24 is carried out in the direction corresponding to the direction in which the real zero speed position of the pump swash plate 16A is displaced with respect to the set zero speed position of the pump swash plate 16A, the pump swash plate 16A moves to the neutral position by the urging force of the forward travel decelerating spring 32 and the reverse travel decelerating spring 33 until the speed change pedal 24 arrives at the actuation position corresponding to the real zero speed position of the pump swash plate 16A.
As a result, this solves the problem that, during accelerating actuation from the zero speed position of the speed change pedal 24, the pump swash plate 16A is operated in the direction opposite to the direction corresponding to the manipulating direction of the speed change pedal 24 due to discrepancies between the pump swash plate 16A and the swash-plate sensor 30 caused by passage of time, resulting in the vehicle running in the direction opposite to the manipulating direction of the speed change pedal 24.
Other Embodiments [1] The work vehicle may be a riding type rice planting machine, a riding type mowing machine, or a wheel loader.
[5] An electric cylinder, an electric motor or a hydraulic motor, etc.
may be used as a control means 55.
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