JP4433436B2 - Work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a work vehicle for agricultural work such as a tractor and a combine, or for construction and transportation, and in particular, a control means for instructing to change the speed change position of the transmission to the deceleration side when the engine speed decreases. The present invention relates to a load control device for a work vehicle.
[0002]
[Prior art]
Conventionally, a load control device that detects a work load from a change in engine speed, etc., and outputs a change command to the speed reduction side of the transmission when the work load exceeds a predetermined value to prevent engine stall. Work vehicles equipped are known. For example, when the work load exceeds a predetermined value, the gear combination of the transmission is shifted down by one step to the side with the larger reduction ratio, and the traveling output rotation is decelerated to avoid engine stall. At this time, if the work load is not yet reduced, the change command is repeated to decelerate the transmission one step at a time. When the work load decreases and the engine returns to the original rotational speed, a speed increase command is output to the transmission to shift up the gear combination of the transmission.
[0003]
[Problems to be solved by the invention]
However, the state in which the transmission is decelerated by the work load by multiple stages is when the vehicle speed is not adapted at all, when the unloading is slow in an unforeseen work state, or when an abnormality occurs in the system, etc. Will be forced to slow down more than necessary.
[0004]
In addition, the engine of this type of work vehicle is formed so that the maximum torque point is set in the medium speed rotation region and the tenacity at low speed traveling can be exhibited. Therefore, in the medium speed rotation range, the engine rotation is reduced by the load but is rarely stalled. On the other hand, when the torque point is lower than a certain level, the engine stalls easily due to the load.
[0005]
Further, since there is a load fluctuation in each operation such as the forward / reverse switching operation of the vehicle body, the clutch connection operation, the lifting / lowering operation of the work machine, or the operation of entering the PTO, a change command is always output.
[0006]
Therefore, in a load control device for a work vehicle that outputs a change command to the speed reduction side of the transmission position when the work load exceeds a predetermined value, the engine is prevented from being stalled and the useless change command is output. Therefore, a technical problem to be solved in order to improve work efficiency is eliminated, and the present invention aims to solve this problem.
[0007]
[Means for Solving the Problems]
The present invention has been proposed in order to achieve the above object, and is configured to transmit the rotational power of the engine 13 to the rear wheels 12 via the main transmissions 46 and 48 and the auxiliary transmission 49 in the transmission case 14. The main transmissions 46 and 48 are configured to be shifted one step at a high speed side or a low speed side by the operation of a switch button 29 provided on the transmission lever 33, and the auxiliary transmission device 49 is configured to manually operate the transmission lever 33. and configured to be shifted by a, the means 20 for detecting a work load provided, with a main transmission device 46, 48 control means 50 for changing instruction to the deceleration side of the shift position of when the working load exceeds a predetermined value in the work vehicle, the limits provided from pre-stored memory shift position in the shift stages to change command to the speed reduction side, and configured to stop the change instruction that exceeds this limit, the storage variable A work vehicle position is characterized by being configured so that you can change the manual shift operation by the switch button 29, and a work vehicle upon detecting a workload exceeding the above limit, which is configured to actuate the alarm means 82, An engine speed sensor 20 is provided as means for detecting the work load, and when the engine speed continuously drops below the first limit value for a predetermined time, the change command is output, while the engine speed is working vehicle configured as when dropped into a second limit value that is lower than the first limit value immediately outputs the change command, and a vehicle body of the forward-reverse switching operation detecting means 35, a clutch connecting operation detecting means 75, a lifting / lowering motion detection means 23 of the work implement, and a PTO entering operation detection means 76 are provided, and when any of the detection means is detected, A work vehicle configured to check or delay the change command is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a tractor 10 as an example of a work vehicle. The tractor 10 has a pair of left and right front wheels 11 and 11 and rear wheels 12 and 12. An engine 13 is mounted on the front part of the vehicle body and from the central part to the rear part of the vehicle body. A mission case 14 is provided, and a working machine 16 such as a rotary is connected to the rear portion of the vehicle body by a link device 15. A driver's seat 17 is provided above the mission case 14 and a steering handle 18 is provided in front of the driver's seat 17 to steer the front wheels 11 and 11.
[0009]
The rotational power of the engine 13 is decelerated by a transmission provided in the mission case 14 and transmitted to the rear wheel 12 or the front and rear wheels 11 and 12, and is also transmitted to the PTO shaft 19 to drive the work implement 16. . The engine 13 is provided with an engine speed sensor 20 as means for detecting a work load. A lift cylinder 21 is provided in the upper part of the transmission case 14. When the lift arm 22 is rotated by the expansion and contraction of the lift cylinder 21, the link mechanism 15 moves up and down to raise and lower the work implement 16. The rotation angle of the lift arm 22 is detected by the lift arm angle sensor 23, and the controller 50 calculates the height of the work implement 16 based on the detected value. Further, a rear cover 25 is rotatably attached to the rear end of the main cover 24 of the work machine 16, and the rotation angle of the rear cover 25 is detected by the rear cover sensor 26, and the controller 50 cultivates the work machine 16 based on the detected value. Calculate depth.
[0010]
In the vicinity of the driver's seat 17, a position lever 30 for changing the height of the work implement 16, a tilling depth setting dial 31 for setting the tilling depth of the work implement 16, a load control switch 32, a transmission lever 33, and the like are provided. . The shift lever 33 is provided with a neutral return-type switch button 29. By operating the switch button 29, the gear combination of the first and second main transmissions, which will be described later, is set one step at a high speed side or a low speed side. Shifted. A handle post 34 is provided in front of the driver's seat 17, and the steering post 34 and the forward / backward switching lever 35 for selecting the forward / backward movement of the vehicle body including the steering handle 18, the working machine from the working position to the non-working position. A work implement lift lever 36 is mounted for continuously ascending or descending from the non-working position to the working position. The rotation operation of the steering handle 18 is transmitted to the steering device 37, and the front wheel 11 turns according to the steering amount. The steering amount of the front wheel 11 is detected by a steering angle sensor 38. Note that 39 is a vehicle speed sensor for detecting the traveling speed of the vehicle body, and 40 is a clutch pedal.
[0011]
2 is a diagram of a power transmission system, FIG. 3 is a hydraulic circuit diagram, and FIG. 4 is a block diagram of a load control system. The rotational power of the engine 13 is intermittently operated by the main clutch 45 in the clutch housing, and sequentially the first main transmission 46, the forward / reverse switching device 47, the second main transmission 48, and the auxiliary transmission in the transmission case 14. 49 is configured to transmit to 49.
[0012]
The first main transmission 46 outputs a signal to the Hi-Lo clutch valve 51 from the controller 50, which is a control means, by the operation of the switch button 29 provided on the shift lever 33, and the Hi-Lo clutch 52 is "high-speed". ”Or“ low speed ”to change the speed. In the forward / reverse switching device 47, a signal is output from the controller 50 to the forward / reverse clutch valve 53 by the operation of the forward / reverse switching lever 35, and the forward / reverse clutch 54 is set to any one of “forward”, “neutral”, and “reverse”. Switching is performed to change the speed.
[0013]
On the other hand, the second main transmission 48 is a synchromesh gear type transmission having four gear sets. When the switch button 29 provided on the transmission lever 33 is operated, the main shift “3-4 speed” is transmitted from the controller 50. A signal is output to the valve 55 or the main shift “1-2 speed” valve 56, and the speed is changed from “1st speed” to “4th speed” by expansion / contraction of the shift hydraulic cylinder 57 or 58 that is a shift actuator. The The sub-transmission device 49 is a sliding mesh gear type transmission device that is switched via a link mechanism by manual operation of the transmission lever 33, and has three speed positions of "low speed", "medium speed", and "high speed". ing.
[0014]
Accordingly, the first main transmission device 46 and the second main transmission device 48 are linked to each other to have an eight-stage main transmission pattern, and the sub-transmission device 49 at each of the “low speed” to “high speed” shift positions, respectively. By operating the switch button 29, eight speeds can be changed, and a total of 24 speed positions are obtained from these combinations.
[0015]
Then, the rotational power changed by the auxiliary transmission 49 is decelerated by the reduction gear 61 of the rear axle via the rear differential device 60, and the rear wheel 12 is driven. Further, the rotational power changed by the auxiliary transmission 49 is also transmitted to the four-wheel drive switching clutch 62, and after being switched to “constant speed” or “acceleration” by the four-wheel drive switching clutch 62, the front differential device. Through 63, the vehicle is decelerated by the reduction gear 64 of the front axle, and the front wheels 11 are driven. Further, the rotational power of the engine 13 is branched into the PTO system at the front stage of the main clutch 45, connected and disconnected by the PTO clutch 65, and sequentially projected through the PTO reverse rotation device 66 and the PTO transmission device 67 at the rear part of the vehicle body. It is transmitted to the PTO shaft 19.
[0016]
Here, reference numeral 70 is a lift cylinder switching valve for controlling the lift cylinder 21, 71 is a four-wheel drive switching valve for controlling the four-wheel drive clutch 62, 72 is a brake cylinder for independently braking left and right rear wheels, and 73 is A brake valve 74 for controlling the brake cylinder 72 and a PTO clutch valve 74 for controlling the PTO clutch 65 are provided. 75 is a clutch pedal sensor for detecting the depression of the clutch pedal 40, 76 is a PTO clutch sensor for detecting the on / off operation of the PTO clutch valve 74, and 77 is a Hi-Lo position sensor of the first main transmission 46. 78 is a “3-4 speed” position sensor of the second main transmission 48, and 79 is a “1-2 speed” position sensor of the second main transmission 48. A shift position of a main shift pattern obtained by linking the main transmission 46 and the second main transmission 48 is detected. 80 is a front wheel rotation sensor that detects the rotation speed of the front wheel 11, 81 is a rear wheel rotation sensor that detects the rotation speed of the rear wheel 12, and 82 is a buzzer or lamp (or a monitor display) that is a means for notifying the operator. is there.
[0017]
Next, the control procedure of the load control device of the present invention will be described with reference to FIG. First, various sensors and switches are read (step 101). If the load control switch 32 is "ON", load control is executed (step 102), and if there is a manual shift operation (step 103), then Are stored as a shift position SM (step 104). When the work load becomes large and an automatic deceleration request is generated (step 105), the number of decelerations up to that time is less than m times (for example, 2 times / min) within the specified time (step 106), and If the current shift position SN at that time is a shift position that is one step lower than the stored shift position SM or a higher shift position that is higher than the stored shift position SM (step 107), a change command is output after step 108. However, when the number of times of deceleration exceeds m times, the change command is stopped by operating the buzzer 82 as a notification means.
[0018]
Thus, when the current engine speed RN continues for about 10 seconds within the range of 65% or more and 75% or less of the rated speed RR (step 108), the main shift position is shifted to the deceleration side by one step. A change command is output so as to shift down (step 110). However, when the work load is further increased and the current engine speed RN becomes less than 65% of the rated speed RR, the main shift position is shifted down one step to the deceleration side when this state continues for about 3 seconds. The change command is output so as to do (step 109 → 110). Thereafter, the number of times of deceleration is counted (step 111). When the work load is still large, the change command is output again up to m times.
[0019]
Here, the range of 65% to 75% of the rated rotational speed RR in step 108 is the rotational speed at a position slightly above the maximum torque generation point of the engine. When the state of the rotation region continues for about 10 seconds, a change command is output so as to shift down by one stage as described above. Further, less than 65% of the rated speed RR in step 109 is the speed at a position slightly below the maximum torque point of the engine. When the state below the rotation region continues for about 3 seconds, a change command is output so as to shift down by one stage. The “10 seconds” and “3 seconds” may be changed according to engine characteristics.
[0020]
In this way, the number of times the shift position is commanded to change to the deceleration side when the work load is large, that is, the number of shift down stages is limited to about two stages, and the change command exceeding this limit is checked, so that the vehicle speed is perfectly adapted. It is possible to prevent unnecessary deceleration in the case where the load is not taken out or when the load is slowly removed in an unpredictable working state. In addition, since there are a plurality of conditions for outputting the change command and the engine speed RN is in the range of 75% or less to 65% of the rated speed RR which is the first limit value, there is relatively no possibility of engine stall. If the engine speed RN does not return to the original state after monitoring for 10 seconds, a downshift change command is output. On the other hand, if the engine speed RN is less than 65% of the rated speed RR, which is a second limit value lower than the first limit value, the danger of engine stall becomes extremely high, so immediately (about 3 Outputs a downshift change command. Thus, it is possible to reliably prevent engine stalls while avoiding excessive change commands as much as possible.
[0021]
On the other hand, as shown in FIG. 6, when the operation of the forward / reverse switching lever 35 is detected by a switch as forward / reverse switching operation detecting means and the detection signal is input to the controller 50 (step 203), the clutch pedal 40 is turned on. When the clutch pedal sensor 75 serving as the clutch connection operation detecting means detects the stepping operation and the detection signal is input to the controller 50 (step 204), the work implement 16 moves up and down and lifts as the work implement lifting operation detecting means. When the arm angle sensor 23 detects and the detection signal is input to the controller 50 (step 205), the PTO clutch sensor 76 as the PTO engagement operation detecting means detects the engagement operation of the PTO clutch 65 and the detection signal is detected. When input to the controller 50 (step 206), a shift down permission timer is set. (Step 207).
[0022]
In such a case, even if there is an automatic deceleration request due to a large work load (step 208), the shift down permission timer is set to 0 after waiting until the shift down permission timer finishes counting (step 209). Sometimes, a change command for shifting the main shift position down by one step to the deceleration side is output (step 210). This is because the vehicle body forward / reverse switching operation, clutch connection operation, each operation such as the lifting / lowering operation of the work implement and the operation of entering the PTO has a load fluctuation, so the change command is stopped at that time, or A slight delay time is provided to monitor the change in the load fluctuation, and the operator's operational feeling is improved by eliminating useless change commands.
[0023]
Further, as shown in FIG. 7, when an automatic deceleration request is made due to a large work load (step 303), a change command for shifting the main shift position down by one step to the deceleration side is output and the number of increases / decreases is counted ( Step 304 → 305). When the load is reduced and an automatic acceleration request is made (step 306), if the increase / decrease count is n times (for example, 5 times / min) or less (step 307), the acceleration operation is recognized by the operator. Accordingly, the buzzer 82 as the notification means is operated (step 308), a change command for shifting the main shift position to the speed increasing side by one step is output, and the number of increases / decreases is counted (step 309 → 305).
[0024]
Also, when there is an automatic acceleration request, if the number of accelerations / decelerations exceeds n times within the specified time, the vehicle speed is not suitable for the load at all, so unnecessary acceleration is avoided. Therefore, if there is no manual shift operation, the speed change command is not output (step 306 → 310). This prohibition of speed increase is canceled when the operator's intentional manual operation is performed (step 310), and the number of times of increase / decrease is initialized (step 311). When the switch button 29 of the shift lever 33 is operated manually by the operator, the buzzer 82 is activated to confirm the operation. The buzzer sound at the time of operating the switch button and the buzzer at the time of the automatic acceleration are operated. The sound can be discriminated with different operating intervals, timbres, and the like.
[0025]
Here, as shown in FIG. 8, the load control switch 32 is a rotary switch, and when the load control switch 32 is set to the “lift control mode”, the work implement is raised when the work load is large. Control to reduce the load. On the other hand, when the “shift down mode” is set, as described above, the control is performed to reduce the load by decelerating the transmission when the work load is large. On the other hand, when the “auto mode” is set, the slip ratio of the rear wheel is calculated from the detection value of the front wheel rotation sensor 80 and the detection value of the rear wheel rotation sensor 81, and when the slip ratio is large, the lift control is performed. The mode is executed, and when the slip ratio is small, the shift down mode is executed to reduce the load. Furthermore, when performing the loader work, the “loader mode” is set. In the loader work, since the loader is attached to the front part of the vehicle body, the vertical movement of the lift arm 22 at the rear part of the vehicle body is stopped. Therefore, only automatic deceleration is performed when the workload is large. In this way, by selectively executing the execution mode of load control, the control procedure can be simplified and the control accuracy can be improved.
[0026]
In the present embodiment, the description is made of checking the number of changed gears for the first and second main transmissions combined with gears. However, the shift position for a continuously variable transmission such as HST is checked. It can also be configured. Thus, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.
[0027]
【The invention's effect】
As described in detail in the above embodiment, the present invention provides the rotational power of the engine 13 to the rear wheels 12 via the main transmissions 46 and 48 and the auxiliary transmission 49 in the transmission case 14. The main transmissions 46 and 48 are configured to shift one step at a high speed side or a low speed side by the operation of a switch button 29 provided on the transmission lever 33, and the auxiliary transmission device 49 The gear is shifted by manual operation of the lever 33, and a means 20 for detecting the work load is provided . When the work load exceeds a predetermined value, the shift position of the main transmission is instructed in advance to change to the deceleration side. and a limit on reduction stages to change command to the speed reduction side from the storage shift position provided with, since so as to stop the change instruction that exceeds this limit, required in such a case where the vehicle speed is not adapted at all There is no deceleration of the above, it can contribute to the improvement of workability.
[0028]
According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, in addition to the effect of the first aspect of the invention, a change command to the deceleration side for the work load exceeding the limit is activated by detecting the work load exceeding the limit. This makes it possible for the operator to reliably recognize that the problem has been restrained.
[0029]
According to a third aspect of the present invention, when a work load is detected by a change in the engine speed, the engine speed drops below the first limit value, and a second limit where the engine speed is lower than the first limit value. In addition to the effect of the invention according to claim 1 or 2, an extra change command is avoided as much as possible according to the characteristics of the engine by providing a difference in the timing of outputting the change command when the value falls below the value. However, the engine stall can be reliably prevented.
[0030]
The invention according to claim 4 is the effect of the invention according to claim 1, 2 or 3 by stopping the change command for operations that cause load fluctuations reliably such as forward / reverse switching operation of the vehicle body and clutch connection operation. In addition, a useless change command is eliminated, and the operational feeling of the operator can be improved.
[Brief description of the drawings]
The figure shows an embodiment of the present invention.
FIG. 1 is a side view of a tractor.
FIG. 2 is a diagram of a power transmission system.
FIG. 3 is a hydraulic circuit diagram.
FIG. 4 is a block diagram of a load control system.
FIG. 5 is a flowchart showing a control procedure of the load control device.
FIG. 6 is a flowchart showing a control procedure of the load control device.
FIG. 7 is a flowchart showing a control procedure of the load control device.
FIG. 8 is a front view of a load control switch.
[Explanation of symbols]
10 Tractor
12 Rear wheel
13 engine
14 Mission case 20 Engine speed sensor 23 Lift arm angle sensor
29 Switch button
33 Transmission lever 35 Forward / reverse switching lever 46 First main transmission 48 Second main transmission
49 Sub transmission 50 Controller 75 Clutch pedal sensor 76 PTO clutch sensor 82 Buzzer

Claims (4)

The rotational power of the engine (13) is transmitted to the rear wheels (12) via the main transmission (46, 48) and the auxiliary transmission (49) in the transmission case (14), and the main transmission (46, 48) is configured such that the operation of the switch button (29) provided on the speed change lever (33) is shifted one step at a time toward the high speed side or the low speed side, and the sub-transmission device (49) includes the speed change lever (33). A means (20) for detecting the work load is provided , and when the work load exceeds a predetermined value, a command for changing the shift position of the main transmission (46 , 48) to the deceleration side is provided. In the work vehicle provided with the control means (50) for performing, a limit is set for the number of shift stages commanded to change from the previously stored stored shift position to the deceleration side, and the change command exceeding this limit is stopped. The memory shift Working vehicle location, characterized by being configured so that you can change the manual shift operation by the switch button (29). The work vehicle according to claim 1, wherein the work means (82) is activated when a work load exceeding the limit is detected. An engine speed sensor (20) is provided as means for detecting the work load. When the engine speed continuously falls below the first limit value for a predetermined time, the change command is output, while the engine speed is The work vehicle according to claim 1 or 2, wherein the change command is immediately output when the vehicle falls to a second limit value lower than the first limit value. The vehicle body forward / reverse switching operation detecting means (35), the clutch connection operation detecting means (75), the lifting / lowering operation detecting means (23) of the work implement, and the PTO entering operation detecting means (76) are provided. 4. The work vehicle according to claim 1, wherein the change command is stopped when the detection means is detected.

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