Continuously variable speed power transmission system for work vehicles and work vehicles

Abstract

To provide a technology which accurately and promptly determines an abnormality of a duplicated rotation detector for a continuously variable power transmission device including combination of a continuously variable transmission and a planetary transmission.SOLUTION: A continuously variable power transmission device for a work vehicle includes: a continuously variable transmission 28; a planetary transmission 31 where engine power and variable speed power are input and planetary power is output; a planetary clutch mechanism 32 which selects a shift level of the planetary transmission 31; a shift control unit 50 which generates control signals for controlling the continuously variable transmission 28 and the planetary clutch mechanism 32 by using an engine rotation number, a variable speed rotation number, a planetary rotation number, and a travel rotation number; a rotation detector group 70 comprising a plurality of rotation detectors configured to detect the engine rotation number, the variable speed rotation number, the planetary rotation number, and the travel rotation number; and a rotation detector determination unit 60 which determines an abnormality of the rotation detector group 70 by using a selection determination rule selected from abnormality determination rules based on a clutch operation state of the planetary clutch mechanism 32.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a continuously variable transmission power transmission device for a work vehicle including a continuously variable transmission and a planetary transmission, and a work vehicle including the continuously variable transmission power transmission device for a work vehicle.

Background Art

[0002] A continuously variable transmission power transmission device (also called HMT) combining a continuously variable transmission and a planetary transmission is used in the power transmission structure of work vehicles such as wheel loaders and tractors. For example, Patent Document 1 discloses a continuously variable transmission power transmission device in which power from an engine is branched to a hydraulic pump of a continuously variable transmission and a planetary transmission, and further, a continuously variable transmission output from a hydraulic motor shaft of the continuously variable transmission is input to the planetary transmission. In such a continuously variable transmission power transmission device, arbitrary transmission power can be obtained from the continuously variable transmission output of the continuously variable transmission input to the planetary transmission and the selected gear stage of the planetary transmission. In this continuously variable transmission power transmission device, engine output and continuously variable transmission output are input to the planetary transmission, and the output from the selected gear stage of the planetary transmission is transmitted to the subsequent stage. Therefore, in proper transmission control, detection of the engine output rotation speed, continuously variable transmission output rotation speed, and planetary transmission output rotation speed in real time is important. If a rotation detector (rotation speed sensor or speed sensor) that detects factors important for continuously variable transmission control, such as the engine output rotation speed, continuously variable transmission output rotation speed, and planetary transmission output rotation speed, fails, accurate continuously variable transmission control becomes impossible. For this reason, so-called fail-safe that duplicates rotation detectors using a plurality of rotation detectors is required.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even when using multiple rotation detectors to duplicate the rotation detectors, determining which rotation detector's detection signal is abnormal when an abnormality occurs requires examining the rotational speeds of other components in the continuously variable transmission power transmission system. Performing this determination accurately and quickly is not easy.

[0005] The object of the present invention is to provide a continuously variable speed power transmission system that combines a continuously variable transmission and a planetary transmission, and a technology for accurately and quickly determining abnormalities in a redundant rotation detector that detects the rotational speed required for continuously variable speed control in a work vehicle. [Means for solving the problem]

[0006] The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a running gear, and comprises: a continuously variable speed transmission that takes the engine power as input and outputs continuously variable speed power; a planetary transmission that takes the engine power and the continuously variable speed power as input and outputs planetary power; a planetary clutch mechanism that selects the gear of the planetary transmission; a forward / reverse switching device that takes the planetary power as input and outputs forward or reverse power to the running gear; and, based on a gear shift operation command, the engine speed of the engine, the continuously variable speed which is the rotational speed of the continuously variable speed power, and the rotation of the planetary power The system comprises: a gear shift control unit that generates control signals to control the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device using the planetary rotation speed, which is the rotation speed of the forward or reverse power, and the driving rotation speed, which is the rotation speed of the forward or reverse power; a group of rotation detectors consisting of a plurality of rotation detectors that detect the engine speed, the continuously variable transmission rotation speed, the planetary rotation speed, and the driving rotation speed; and a rotation detector determination unit that determines an abnormality in the group of rotation detectors using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operation state of the planetary clutch mechanism and the forward / reverse switching device. 、 The rotation detector group includes a main engine rotation detector for detecting the engine rotation speed, a redundant engine rotation detector for detecting the rotation speed of the input shaft that receives engine power as the engine rotation speed, a main continuously variable speed rotation detector for detecting the continuously variable speed rotation speed, a main planetary rotation detector for detecting the planetary rotation speed, a redundant planetary rotation detector for detecting the planetary rotation speed, a main travel rotation detector for detecting the travel rotation speed, and a redundant travel rotation detector for detecting the travel rotation speed. . The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a running gear, and comprises: a continuously variable speed transmission that takes the engine power as input and outputs continuously variable speed power; a planetary transmission that takes the engine power and the continuously variable speed power as input and outputs planetary power; a planetary clutch mechanism that selects the gear of the planetary transmission; a forward / reverse switching device that takes the planetary power as input and outputs forward or reverse power to the running gear; and, based on a gear shift operation command, the engine speed of the engine, the continuously variable speed which is the rotational speed of the continuously variable speed power, and the rotation of the planetary power The system comprises: a gear shift control unit that generates control signals to control the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device using the planetary rotation speed, which is a number, and the travel rotation speed, which is the rotation speed of the forward or reverse power; a group of rotation detectors consisting of a plurality of rotation detectors that detect the engine speed, the continuously variable transmission rotation speed, the planetary rotation speed, and the travel rotation speed; and a rotation detector determination unit that determines an abnormality in the group of rotation detectors using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operation state of the planetary clutch mechanism and the forward / reverse switching device. The abnormalities in the rotation detector group determined by the rotation detector determination unit are classified into three categories: a low-level abnormality state that only issues a warning, a moderate-level abnormality state that permits temporary driving, and a severe abnormality state that causes an emergency stop of driving. The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a running gear, and comprises: a continuously variable speed transmission that takes the engine power as input and outputs continuously variable speed power; a planetary transmission that takes the engine power and the continuously variable speed power as input and outputs planetary power; a planetary clutch mechanism that selects the gear of the planetary transmission; a forward / reverse switching device that takes the planetary power as input and outputs forward or reverse power to the running gear; and, based on a gear shift operation command, the engine speed of the engine, the continuously variable speed which is the rotational speed of the continuously variable speed power, and the rotation of the planetary power The system comprises: a gear shift control unit that generates control signals to control the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device using the planetary rotation speed, which is a number, and the travel rotation speed, which is the rotation speed of the forward or reverse power; a group of rotation detectors consisting of a plurality of rotation detectors that detect the engine speed, the continuously variable transmission rotation speed, the planetary rotation speed, and the travel rotation speed; and a rotation detector determination unit that determines an abnormality in the group of rotation detectors using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operation state of the planetary clutch mechanism and the forward / reverse switching device. When the clutch operation state of the planetary clutch mechanism is ON, the rotation detector determination unit determines that If the relationship between the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector is normal, the relationship between the detected values ​​of the main continuously variable speed rotation detector and the main planetary rotation detector is abnormal, and the relationship between the detected values ​​of the main continuously variable speed rotation detector and the redundant planetary rotation detector is abnormal, then it is determined that the main continuously variable speed rotation detector is abnormal. If the relationship between the detected values ​​of the main continuously variable speed rotation detector and the redundant planetary rotation detector is normal, the relationship between the detected values ​​of the main planetary rotation detector and the main continuously variable speed rotation detector is abnormal, and the relationship between the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector is abnormal, then it is determined that the main planetary rotation detector is abnormal. If the relationship between the detected values ​​of the main continuously variable speed rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant planetary rotation detector and the main continuously variable speed rotation detector is abnormal, and the relationship between the detected values ​​of the redundant planetary rotation detector and the main planetary rotation detector is abnormal, then it is determined that the redundant planetary rotation detector is abnormal. . The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a running gear, and comprises: a continuously variable speed transmission that takes the engine power as input and outputs continuously variable speed power; a planetary transmission that takes the engine power and the continuously variable speed power as input and outputs planetary power; a planetary clutch mechanism that selects the gear of the planetary transmission; a forward / reverse switching device that takes the planetary power as input and outputs forward or reverse power to the running gear; and, based on a gear shift operation command, the engine speed of the engine, the continuously variable speed which is the rotational speed of the continuously variable speed power, and the rotation of the planetary power The system comprises: a gear shift control unit that generates control signals to control the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device using the planetary rotation speed, which is a number, and the travel rotation speed, which is the rotation speed of the forward or reverse power; a group of rotation detectors consisting of a plurality of rotation detectors that detect the engine speed, the continuously variable transmission rotation speed, the planetary rotation speed, and the travel rotation speed; and a rotation detector determination unit that determines an abnormality in the group of rotation detectors using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operation state of the planetary clutch mechanism and the forward / reverse switching device. When the clutch operation state of the planetary clutch mechanism is in an incompletely coupled state, the rotation detector determination unit determines that both the main planetary rotation detector and the redundant planetary rotation detector are abnormal if the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector do not match. The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a running gear, and comprises: a continuously variable speed transmission that takes the engine power as input and outputs continuously variable speed power; a planetary transmission that takes the engine power and the continuously variable speed power as input and outputs planetary power; a planetary clutch mechanism that selects the gear of the planetary transmission; a forward / reverse switching device that takes the planetary power as input and outputs forward or reverse power to the running gear; and, based on a gear shift operation command, the engine speed of the engine, the continuously variable speed which is the rotational speed of the continuously variable speed power, and the rotation of the planetary power The system comprises: a gear shift control unit that generates control signals to control the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device using the planetary rotation speed, which is a number, and the travel rotation speed, which is the rotation speed of the forward or reverse power; a group of rotation detectors consisting of a plurality of rotation detectors that detect the engine speed, the continuously variable transmission rotation speed, the planetary rotation speed, and the travel rotation speed; and a rotation detector determination unit that determines an abnormality in the group of rotation detectors using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operation state of the planetary clutch mechanism and the forward / reverse switching device. When the clutch of the forward / reverse switching device is ON, the rotation detector determination unit determines: If the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is abnormal, and the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is abnormal, then it is determined that the main travel rotation detector is abnormal. If the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant travel rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is abnormal, then it is determined that the redundant travel rotation detector is abnormal. If the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is normal, the relationship between the detected values ​​of the main planetary rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the main planetary rotation detector and the redundant travel rotation detector is abnormal, then it is determined that the main planetary rotation detector is abnormal. .

[0007] In this configuration, the rotation detector determination unit, which determines abnormalities in the rotation detector group, has prepared multiple abnormality determination rules that are selected based on the clutch operation state in the planetary clutch mechanism and the clutch operation state of the forward / reverse switching device. The rotation detector determination unit applies the continuously variable speed rotation speed, planetary speed rotation speed, and travel speed obtained from the rotation detector group to the selected abnormality determination rule to determine abnormalities in the rotation detector group. By appropriately selecting the abnormality determination rule, abnormalities in the duplicated rotation detectors can be accurately and quickly determined regardless of the shift state of the continuously variable power transmission system.

[0008] In work vehicles, it is common to maintain a constant engine speed during operation, but the appropriate engine speed changes depending on the work content and the conditions of the workplace. Since the power initially input to the continuously variable transmission (CVT) is engine power, the engine speed is the basic rotational speed of the CVT. For this reason, the engine speed is important in determining abnormalities in the rotational speed detector group that detects rotational speed in each region of the CVT. Accordingly, in the present invention, the rotational speed detector determination unit takes the engine speed into consideration when selecting the selection determination rule.

[0009] In one preferred embodiment of the present invention, the rotation detector group includes a main engine rotation detector for detecting the engine rotation speed, a redundant engine rotation detector for detecting the rotation speed of the input shaft that receives the engine power as the engine rotation speed, a main continuously variable speed rotation detector for detecting the continuously variable speed rotation speed, a main planetary rotation detector for detecting the planetary rotation speed, a redundant planetary rotation detector for detecting the planetary rotation speed, a main travel rotation detector for detecting the travel rotation speed, and a redundant travel rotation detector for detecting the travel rotation speed.

[0010] Since the engine speed is strictly controlled by the engine control unit, the rotation detection function managed by the engine control unit can be used as the main engine speed detector. However, communication failures in the data transmission line from the engine control unit to the speed detector determination unit may cause the engine speed reading from the engine control unit to be interrupted. For this reason, among the components of the continuously variable transmission power transmission system, a speed detector that detects the rotation speed of the input shaft that receives engine power from the engine is provided as a redundant engine speed detector to back up the main engine speed detector (engine control unit).

[0011] The output rotational speed of the planetary gearbox can be calculated from the input rotational speed of the planetary gearbox (continuously variable speed rotational speed) and the clutch operation state of the planetary clutch mechanism. Therefore, abnormalities in each of the three rotational sensors—the main continuously variable speed rotational sensor, the main planetary rotational sensor, and the redundant planetary rotational sensor—can be determined by a logical operation such as majority voting. For this reason, the redundant continuously variable speed rotational sensor for detecting the continuously variable speed rotational speed is omitted here.

[0012] The rotational speed of the power input to the forward / reverse switching device (planetary rotational speed) and the rotational speed of the forward driving power output from the forward / reverse switching device (positive running rotational speed) or the rotational speed of the reverse driving power (negative running rotational speed) correspond in a certain relationship (depending on the gear ratio of the forward / reverse switching device) if the clutch transmission state of the forward / reverse switching device is ON (fully engaged state). However, if the clutch transmission state is OFF (incompletely engaged state), they do not correspond in a certain relationship and the relationship becomes unclear. From this, if the clutch transmission state is the fully engaged state, it is possible to determine each abnormality from the relationship between the rotational speeds of the three rotational detectors: the planetary rotation detector or redundant planetary rotation detector, the main running rotation detector, and the redundant running rotation detector.

[0013] Depending on the type and situation of the rotational detector determined to be abnormal, the abnormal countermeasures to be taken are different. Therefore, in the present invention, the abnormality of the rotational detector group determined by the rotational detector determination unit is classified into a low-abnormality state that only issues a warning notification, a medium-abnormality state that permits temporary running, and a high-abnormality state that performs an emergency stop of running.

[0014] A preferred example of the abnormality determination rule for determining the abnormality of the rotational detector by the rotational detector determination unit is as follows.

[0015] (1) When the clutch operating state of the planetary clutch mechanism is ON, if the relationship between the detection values between the main planetary rotation detector and the redundant planetary rotation detector is normal, the relationship between the detection values between the main continuously variable transmission rotation detector and the main planetary rotation detector is abnormal, and the relationship between the detection values between the main continuously variable transmission rotation detector and the redundant planetary rotation detector is abnormal, it is determined that the main continuously variable transmission rotation detector is abnormal. That is, if the detection values of the main planetary rotation detector and the redundant planetary rotation detector are substantially the same, the main planetary rotation detector and the redundant planetary rotation detector are regarded as normal. Furthermore, since the transmission ratio of the planetary transmission is defined by the planetary clutch mechanism, if a difference exceeding the transmission ratio of the planetary transmission is shown between the detection value of the main continuously variable transmission rotation detector and the detection value of the main planetary rotation detector, and a difference exceeding the transmission ratio of the planetary transmission is shown between the detection value of the main continuously variable transmission rotation detector and the detection value of the redundant planetary rotation detector, it can be determined that the main continuously variable transmission rotation detector is abnormal.

[0016] (2) When the clutch operating state of the planetary clutch mechanism is ON, if the relationship between the detection values between the main continuously variable transmission rotation detector and the redundant planetary rotation detector is normal, the relationship between the detection values between the main planetary rotation detector and the main continuously variable transmission rotation detector is abnormal, and the relationship between the detection values between the main planetary rotation detector and the redundant planetary rotation detector is abnormal, it is determined that the main planetary rotation detector is abnormal. That is, if there is no difference exceeding the transmission ratio of the planetary transmission between the detection value of the main continuously variable transmission rotation detector and the detection value of the redundant planetary rotation detector, the main continuously variable transmission rotation detector and the redundant planetary rotation detector are regarded as normal. In that state, if there is a difference exceeding the transmission ratio of the planetary transmission between the detection values of the main planetary rotation detector and the main continuously variable transmission rotation detector, and the detection values of the main planetary rotation detector and the redundant planetary rotation detector are substantially different, it can be determined that the main planetary rotation detector is abnormal.

[0017] (3) When the clutch operation state of the planetary clutch mechanism is ON, if the relationship between the detected values ​​of the main continuously variable speed rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant planetary rotation detector and the main continuously variable speed rotation detector is abnormal, and the relationship between the detected values ​​of the redundant planetary rotation detector and the main planetary rotation detector is abnormal, then the redundant planetary rotation detector is determined to be abnormal. In other words, if there is no difference between the detected value of the main continuously variable speed rotation detector and the detected value of the main planetary rotation detector that exceeds the gear ratio of the planetary transmission, then the main continuously variable speed rotation detector and the main planetary rotation detector are considered normal. In that state, if there is a difference between the detected value of the redundant planetary rotation detector and the detected value of the main continuously variable speed rotation detector that exceeds the gear ratio of the planetary transmission, and if the detected value of the redundant planetary rotation detector and the detected value of the main planetary rotation detector are substantially different, then the redundant planetary rotation detector can be determined to be abnormal.

[0018] (4) When the clutch of the planetary clutch mechanism is OFF, the relationship between the input rotational speed and the output rotational speed of the planetary transmission becomes unknown, making it impossible to calculate the output rotational speed from the input rotational speed (engine rotational speed and continuously variable transmission rotational speed). Even in this state, if the main planetary rotation detector and the redundant planetary rotation detector output substantially the same detection value, both the main planetary rotation detector and the redundant planetary rotation detector can be considered normal. However, if the detection value of the planetary rotation detector and the detection value of the redundant planetary rotation detector output substantially different detection values, one or both of them can be considered abnormal. Therefore, in the present invention, when the clutch of the planetary clutch mechanism is OFF, the rotation detector determination unit determines that both the main planetary rotation detector and the redundant planetary rotation detector are abnormal if the detection values ​​of the main planetary rotation detector and the redundant planetary rotation detector do not match.

[0019] (5) When the clutch of the forward / reverse gear changer is ON (fully coupled), if the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is abnormal, and the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is abnormal, then the main travel rotation detector is determined to be abnormal. When the clutch of the forward / reverse gear changer is fully coupled, the rotational speed of the power input to the forward / reverse gear changer (planetary rotation speed) and the rotational speed of the power output from the forward / reverse gear changer (travel rotation speed) correspond in a constant relationship (depending on the gear ratio of the forward / reverse gear changer). Therefore, if the redundant travel rotation detector and the main planetary rotation detector are normal, and the relationship between the detected value of the main travel rotation detector and the redundant travel rotation detector is abnormal, then the main travel rotation detector can be considered to be abnormal.

[0020] (6) For similar reasons, when the clutch of the forward / reverse switching device is ON (fully coupled), if the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant travel rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is abnormal, then the redundant travel rotation detector is determined to be abnormal.

[0021] (7) Furthermore, when the clutch operation state of the forward / reverse switching device is ON (fully coupled state), if the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is normal, the relationship between the detected values ​​of the main planetary rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the main planetary rotation detector and the redundant travel rotation detector is abnormal, then the main planetary rotation detector is determined to be abnormal.

[0022] (8) If the clutch transmission state of the forward / reverse switching device is in an incompletely coupled state, the rotational speed of the power input to the forward / reverse switching device (planetary rotational speed) and the rotational speed of the power output from the forward / reverse switching device (travel rotational speed) do not correspond in a constant relationship, and the relationship becomes unknown. In such a state, if the main travel rotation detector and the redundant travel rotation detector output substantially the same detection value, both the main travel rotation detector and the redundant travel rotation detector can be considered normal, and if the main travel rotation detector and the redundant travel rotation detector output substantially different detection values, one or both of them can be considered abnormal. Therefore, in the present invention, when the clutch operation state of the forward / reverse switching device is in an incompletely coupled state, the rotation detector determination unit determines that both the main travel rotation detector and the redundant travel rotation detector are abnormal if the detection values ​​of the main travel rotation detector and the redundant travel rotation detector do not match.

[0023] This invention also applies to work vehicles equipped with the above-described continuously variable power transmission device for work vehicles. Such work vehicles possess the operation and effects of the above-described continuously variable power transmission device for work vehicles. [Brief explanation of the drawing]

[0024] [Figure 1] This is a side view of the tractor. [Figure 2] This is a schematic diagram of a continuously variable transmission power transmission system. [Figure 3] This is a schematic diagram of the planetary gearbox. [Figure 4] This is a block diagram showing the input / output devices in a gear shift control unit. [Figure 5] This is a block diagram of the control functions of a continuously variable transmission power transmission system. [Figure 6] This is an explanatory diagram of vehicle speed shifting in a transmission control unit. [Modes for carrying out the invention]

[0025] Hereinafter, an embodiment of the present invention will be described based on the drawings. In the following explanation, with respect to the tractor (an example of a "work vehicle"), the direction of arrow F in Figure 1 is referred to as the "front of the vehicle," the direction of arrow B in Figure 1 is referred to as the "rear of the vehicle," the direction of arrow U in Figure 1 is referred to as the "top of the vehicle," the direction of arrow D in Figure 1 is referred to as the "bottom of the vehicle," the direction of the front side of Figure 1 is referred to as the "left side of the vehicle," and the direction of the back side of Figure 1 is referred to as the "right side of the vehicle."

[0026] [Overall view of the tractor] Figure 1 shows a tractor. This tractor has a vehicle body 3 supported by a pair of steerable and drivable front wheels 1 (running gear) and a pair of drivable rear wheels 2 (running gear). A drive unit 5 containing an engine 4 is provided at the front of the vehicle body 3. At the rear of the vehicle body 3 is a driver's compartment 6 where the operator sits and operates the vehicle, and a link mechanism 7 that connects to work equipment such as a rotary tiller so that it can be raised and lowered. The driver's compartment 6 is equipped with a driver's seat 8, a steering wheel 9 for steering the front wheels 1, and a cabin 10 that covers the passenger space. The vehicle body frame 11 of the vehicle body 3 is composed of an engine 4, a transmission case 12 whose front end is connected to the rear of the engine 4, and a front wheel support frame 13 connected to the bottom of the engine 4. At the rear of the transmission case 12 is a power take-off shaft 14 that extracts power from the engine 4 and transmits it to the work equipment connected by the link mechanism 7.

[0027] [Power transmission system for traction] As shown in Figure 2, the power transmission device 15 for driving, which transmits power from the engine 4 (engine power) to the front wheels 1 and rear wheels 2, includes a transmission 18 that changes the speed of the power from the engine 4 and transmits it to the rear differential mechanism 16 and the front differential mechanism 17. The transmission 18 is housed in a transmission case 12.

[0028] As shown in Figure 2, the transmission 18 includes an input shaft 20 located at the front of the transmission case 12 to which power from the output shaft 4a of the engine 4 is transmitted; a main transmission unit 21 that receives power from the input shaft 20 and outputs the input power after shifting the speed; a forward / reverse switching device 23 to which the output of the main transmission unit 21 is received; a gear mechanism 24 that transmits the output of the forward / reverse switching device 23 to the input shaft 16a of the rear wheel differential mechanism 16; and a front wheel transmission unit 25 that receives the output of the forward / reverse switching device 23 and outputs the input power after shifting the speed to the front wheel differential mechanism 17.

[0029] [Main transmission unit] As shown in Figure 2, the main transmission unit 21 includes a continuously variable transmission 28 to which the power from the input shaft 20 is input, a planetary transmission 31 to which the power from the input shaft 20 and the output of the continuously variable transmission 28 are input, and a planetary clutch mechanism 37 for selecting the gear of the planetary transmission 31.

[0030] As shown in Figure 2, the continuously variable transmission 28 comprises a variable displacement hydraulic pump P connected to a pump shaft 28a, which serves as a continuously variable input shaft and is connected to the input shaft 20 via a first gear mechanism 27 connected to the rear end of a rotating shaft 26 connected to the rear end of the input shaft 20, and a hydraulic motor M driven by pressurized oil from the hydraulic pump P. By changing the swash plate angle of the hydraulic pump P, the power from the input shaft 20 is changed into forward and reverse rotational power, and the rotational speed of the forward and reverse rotational power is changed steplessly and output from the motor shaft 28b, which serves as a continuously variable output shaft. The continuously variable transmission 28 is a hydrostatic continuously variable transmission called an HST (Hydraulic Static Transmission).

[0031] The planetary transmission 31 has a planetary transmission section 31A to which the power from the input shaft 20 and the output from the continuously variable transmission 28 are input. The planetary clutch mechanism 37 functions as the output section 31B of the planetary transmission 31, and outputs the output of the planetary transmission section 31A divided into four speed ranges.

[0032] As shown in Figures 2 and 3, the planetary gear shifting unit 31A includes a first planetary gear shifting unit 32 having a first sun gear 32a, a first planetary gear 32b that meshes with the first sun gear 32a, and a first ring gear 32c with internal teeth that meshes with the first planetary gear 32b. The planetary gear shifting unit 31A is provided with a second planetary gear shifting unit 33 located behind the first planetary gear shifting unit 32, and includes a second sun gear 33a, a second planetary gear 33b that meshes with the second sun gear 33a, a second ring gear 33c with internal teeth that meshes with the second planetary gear 33b, and a second carrier 33d that supports the second planetary gear 33b.

[0033] As shown in Figure 2, a second gear mechanism 30 is provided between the first sun gear 32a and the motor shaft 28b of the continuously variable transmission 28, and the output of the continuously variable transmission 28 is input to the first sun gear 31a via the second gear mechanism 30. A third gear mechanism 29 is provided between the first ring gear 32c and the input shaft 20, and the power of the input shaft 20 is input to the first ring gear 32c via the third gear mechanism 29. As shown in Figures 2 and 3, the first planetary gear shifting unit 32 is provided with an interlocking gear 32d that meshes with the first planetary gear 32b, and the interlocking gear 32d and the second planetary gear 33b are interlocked by a connecting member 33e. The first planetary gear shifting unit 32 and the second planetary gear shifting unit 33 constitute a so-called composite planetary gear shifting unit.

[0034] As shown in Figures 2 and 3, the planetary clutch mechanism 37 comprises a triple-shaft structure consisting of a first input shaft 34a, a second input shaft 34b, and a third input shaft 34c, and an output shaft 35 positioned parallel to the first input shaft 34a, etc. The first input shaft 34a is connected to a second ring gear 33c, the second input shaft 34b is connected to a second carrier 33d, and the third input shaft 34c is connected to a second sun gear 33a. A first range gear mechanism 36a is connected to the first input shaft 34a, and a first clutch CL1 is provided across the first range gear mechanism 36a and the output shaft 35. A second range gear mechanism 36b is connected to the third input shaft 34c, and a second clutch CL2 is provided across the second range gear mechanism 36b and the output shaft 35. A third range gear mechanism 36c is connected to the second input shaft 34b, and a third clutch CL3 is provided between the third range gear mechanism 36c and the output shaft 35. A fourth range gear mechanism 36d is connected to the third input shaft 34c, and a fourth clutch CL4 is provided between the fourth range gear mechanism 36d and the output shaft 35.

[0035] In the main transmission unit 21, power from the engine 4 is input to the hydraulic pump P via the input shaft 20, the rotating shaft 26, and the first gear mechanism 27, and is converted into forward and reverse power by the continuously variable transmission 28 and output from the motor shaft 28b, and the rotational speed of the output forward and reverse power is continuously varied. The output of the continuously variable transmission 28 is input to the first sun gear 32a of the first planetary transmission unit 32 via the second gear mechanism 30, and power from the engine 4 is input to the first ring gear 32c of the first planetary transmission unit 32 via the input shaft 20 and the third gear mechanism 29, and the power from the continuously variable transmission 28 and the power from the engine 4 are combined by the first planetary transmission unit 32 and the second planetary transmission unit 33 of the planetary transmission unit 31A, and the combined power is transmitted from the second planetary transmission unit 33 to the output unit 31B and output from the output shaft 35.

[0036] In the main transmission unit 21, when the continuously variable transmission 28 is shifted with the first clutch CL1 engaged, the combined power generated by the planetary transmission unit 31A is transmitted from the second ring gear 33c to the first input shaft 34a of the output unit 31B. In the output unit 31B, the first range gear mechanism 36a and the first clutch CL1 generate power that shifts continuously in the first gear range, which is then output from the output shaft 35.

[0037] When the continuously variable transmission 28 is shifted while the second clutch CL2 is engaged, the combined power generated by the planetary gear shifting unit 31A is transmitted from the second sun gear 33a to the third input shaft 34c of the output unit 31B. At the output unit 31B, the second range gear mechanism 36b and the second clutch CL2 convert the power into a continuously variable force in the second gear range, which is then output from the output shaft 35.

[0038] When the continuously variable transmission 28 is shifted while the third clutch CL3 is engaged, the combined power generated by the planetary gear shifting unit 31A is transmitted from the second carrier 33d to the second input shaft 34b of the output unit 31B. At the output unit 31B, the third range gear mechanism 36c and the third clutch CL3 generate power that shifts continuously in the third range, which is then output from the output shaft 35.

[0039] When the continuously variable transmission 28 is shifted while the fourth clutch CL4 is engaged, the combined power generated by the planetary gear shifting unit 31A is transmitted from the second sun gear 33a to the third input shaft 34c of the output unit 31B. At the output unit 31B, the fourth range gear mechanism 36d and the fourth clutch CL4 generate power that shifts continuously in the fourth gear range, which is then output from the output shaft 35.

[0040] [Forward / forward switching device] As shown in Figure 2, the forward / reverse switching device 23 comprises an input shaft 23a connected to the output shaft 35 of the planetary transmission 31, and an output shaft 23b provided parallel to the input shaft 23a. The input shaft 23a is provided with a forward clutch CLF and a reverse clutch CLR. A forward gear interlocking mechanism 23c is provided between the forward clutch CLF and the output shaft 23b, and a reverse gear interlocking mechanism 23d is provided between the reverse clutch CLR and the output shaft 23b.

[0041] When the forward clutch CLF is operated to the "engage" position, it connects the input shaft 23a to the forward gear interlocking mechanism 23c, creating a forward transmission state in which the power from the input shaft 23a is transmitted to the output shaft 23b via the forward gear interlocking mechanism 23c. When the reverse clutch CLR is operated to the "engage" position, it connects the input shaft 23a to the reverse gear interlocking mechanism 23d, creating a reverse transmission state in which the power from the input shaft 23a is transmitted to the output shaft 23b via the reverse gear interlocking mechanism 23d.

[0042] In the forward / reverse switching device 23, the output of the planetary transmission 31 is input to the input shaft 23a, and when the forward clutch CLF is operated to engage, the power of the input shaft 23a is converted into forward power by the forward clutch CLF and the forward gear interlocking mechanism 23c and transmitted to the output shaft 23b. When the reverse clutch CLR is operated to engage, the power of the input shaft 23a is converted into reverse power by the reverse clutch CLR and the reverse gear interlocking mechanism 23d and transmitted to the output shaft 23b. The forward and reverse power of the output shaft 23b are transmitted to the rear wheel differential mechanism 16 and the front wheel transmission unit 25 by the gear mechanism 24.

[0043] In the rear wheel differential mechanism 16, forward or reverse power transmitted from the forward / reverse switching device 23 is transmitted from the left and right output shafts 16b to the left and right rear wheels 2. Power from the left output shaft 16b is transmitted to the left rear wheel 2 via the planetary reduction mechanism 38B. A steering brake 38A is provided on the left output shaft 16b. Although not shown, the transmission system from the right output shaft 16b to the right rear wheel 2 is also provided with a planetary reduction mechanism 38B and a steering brake 38A, similar to the transmission system to the left rear wheel 2.

[0044] [Front wheel transmission] As shown in Figure 2, the front wheel transmission unit 25 includes an input shaft 25a connected to the output shaft 24a of the gear mechanism 24, and an output shaft 25b located parallel to the input shaft 25a. The input shaft 25a is provided with a constant-speed clutch CLT and a speed-increasing clutch CLH located behind the constant-speed clutch CLT. A constant-speed gear mechanism 40 is provided across the constant-speed clutch CLT and the output shaft 25b. A speed-increasing gear mechanism 41 is provided across the speed-increasing clutch CLH and the output shaft 25b. A parking brake 39 is provided on the output shaft 24a of the gear mechanism 24.

[0045] In the front wheel transmission unit 25, when the constant-velocity clutch CLT is operated to engage, the power from the input shaft 25a is transmitted to the output shaft 25b by the constant-velocity clutch CLT and the constant-velocity gear mechanism 40, and the constant-velocity transmission state is created by the constant-velocity gear mechanism 40, so that power to drive the front wheel 1 is output from the output shaft 25b when the peripheral speed of the front wheel 1 is the same as the peripheral speed of the rear wheel 2. When the speed-increasing clutch CLH is operated to engage, the power from the input shaft 25a is transmitted to the output shaft 25b by the speed-increasing clutch CLH and the speed-increasing gear mechanism 41, and the front wheel speed-increasing transmission state is created by the speed-increasing gear mechanism 41, so that power to drive the front wheel 1 is output from the output shaft 25b when the peripheral speed of the front wheel 1 is faster than the peripheral speed of the rear wheel 2. The output from the output shaft 25b is input to the front wheel differential mechanism 17 via the rotating shaft 42 that connects the output shaft 25b and the input shaft 17a of the front wheel differential mechanism 17.

[0046] When the constant-speed clutch CLT is engaged, the vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven at a speed equal to the average circumferential speed of the left and right front wheels 1, and when the speed-increasing clutch CLH is engaged, the vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven at a speed higher than the average circumferential speed of the left and right rear wheels 2. As a result, when the speed-increasing clutch CLH is engaged, the vehicle body 3 can be driven with a smaller turning radius than when the constant-speed clutch CLT is engaged.

[0047] [Regarding the rotation detector group] A rotation detector group 70 is provided in the power transmission device 15 to detect the engine speed, which is the rotational speed of the engine power; the continuously variable transmission speed (output of the continuously variable transmission 28), which is the rotational speed of the continuously variable transmission power (output of the planetary transmission 31), which is the rotational speed of the planetary drive system, and the travel speed, which is the rotational speed of the forward power (output of the forward / reverse switching device 23) or reverse power (output of the forward / reverse switching device 23). The rotation detector group 70 consists of multiple rotation detectors and includes, in particular, a main engine rotation detector 71 and a redundant engine rotation detector 72 for detecting the engine speed, a main continuously variable transmission rotation detector 73 for detecting the continuously variable transmission speed, a main planetary rotation detector 74 and a redundant planetary rotation detector 75 for detecting the planetary drive speed, and a main travel rotation detector 76 and a redundant travel rotation detector 77 for detecting the travel speed. The rotation detectors designated as "redundant" are backup rotation detectors for the rotation detectors designated as "main". In this embodiment, the only rotation detector used to detect the continuously variable speed rotation is the main continuously variable speed rotation detector 73, and no backup rotation detector is provided. Since the redundant rotation detector is a backup for the main rotation detector, an inexpensive rotation detector that cannot identify the direction of rotation (cannot detect the direction of rotation) is used to reduce costs.

[0048] The main engine speed detector 71 is a speed detector managed by the engine control unit EU, which controls the engine 4. The engine control unit EU strictly manages the engine speed, so the engine speed detected by the main engine speed detector 71 is highly reliable and can also identify the direction of rotation (forward or reverse). This engine speed is obtained from the engine control unit EU via the in-vehicle LAN. The redundant engine speed detector 72 is provided to detect the gear speed (corresponding to the engine speed) of the first gear mechanism 27, which is linked to the input shaft 20, and does not identify the direction of rotation. If the engine speed from the engine control unit EU is interrupted, the engine speed is calculated from the detection signal of the redundant engine speed detector 72.

[0049] The main continuously variable speed rotation detector 73 is provided to detect the gear rotation speed of the second gear mechanism 30 (corresponding to the output rotation speed of the continuously variable speed transmission 28), and can also identify the direction of rotation. When the continuously variable speed transmission 28 is in neutral, the rotation speed detected by the main continuously variable speed rotation detector 73 is zero.

[0050] The main planetary rotation detector 74 and the redundant planetary rotation detector 75 are rotation detectors that detect the input rotation speed of the forward / reverse switching device 23, which is the output rotation speed of the planetary transmission 31. The main planetary rotation detector 74 is provided to detect the rotation speed of the clutch housing (a type of first rotating body) that rotates integrally with the input shaft 23a of the forward / reverse switching device 23. The redundant planetary rotation detector 75 is provided to detect the rotation speed of the clutch housing (a type of second rotating body) of the planetary clutch mechanism 37 that rotates integrally with the output shaft 35 of the planetary transmission 31. The main planetary rotation detector 74 can also identify the direction of rotation, but the redundant planetary rotation detector 75 does not identify the direction of rotation.

[0051] The rotational speed on the input side (engine side) of the forward / reverse switching device 23 varies depending on the gear ratio of the planetary transmission 31. Furthermore, the input rotational speed of the forward / reverse switching device 23 can be calculated using the engine speed, the output speed of the continuously variable transmission 28, and the gear ratio of the planetary transmission 31. However, it is taken into consideration that rotational movement may occur even when all the clutches of the planetary clutch mechanism 37 are OFF.

[0052] The main travel rotation detector 76 and the redundant travel rotation detector 77 are rotation detectors that detect the travel rotation speed, which is the rotation speed of the component that determines the vehicle speed. The main travel rotation detector 76 is provided to detect the rotation speed of the clutch housing (a type of first rotating component) of the constant-speed clutch CLT, which is linked to the input shaft 25a of the front wheel transmission unit 25. The redundant travel rotation detector 77 is provided to detect the rotation speed of the clutch housing (a type of second rotating component) of the speed-increasing clutch CLH, which is linked to the input shaft 25a of the front wheel transmission unit 25. The main travel rotation detector 76 can also identify the direction of rotation, but the redundant travel rotation detector 77 does not identify the direction of rotation.

[0053] The rotational speed on the output side of the forward / reverse switching device 23 can be calculated from the detection signal of the main travel rotation detector 76 or the redundant travel rotation detector 77. However, the relationship between the rotational speed on the input side of the forward / reverse switching device 23 and the rotational speed on the output side of the forward / reverse switching device 23 changes based on the clutch engagement state of the forward / reverse switching device 23.

[0054] [Regarding the transmission control unit] The gear shift control in this continuously variable transmission is performed by the gear shift control unit 50 shown in Figures 4 and 5. Gear shifting by the driver is performed using the gear shift pedal 46 and forward / reverse lever 47, which are provided in the driver's unit 6 as gear shift control devices 45 that give gear shift operation commands. The amount of movement of the gear shift pedal 46 and forward / reverse lever 47 is input to the gear shift control unit 50. Detection signals (rotational speed) from the rotation detector group 70 are also input to the gear shift control unit 50. The gear shift control unit 50 generates control signals for hydraulically controlling the operation of the continuously variable transmission 28, planetary clutch mechanism 37, forward / reverse switching device 23, etc.

[0055] As shown in Figure 5, the gear shift control unit 50 is equipped with a gear shift control unit 51, a rotation detector determination unit 60, and a rotation speed acquisition unit 61. The gear shift control unit 51 includes a continuously variable transmission control unit 52, a planetary clutch control unit 53, and a forward / reverse clutch control unit 54. The continuously variable transmission control unit 52 generates a control signal to control the operation (swashplate angle adjustment) of the continuously variable transmission 28. The planetary clutch control unit 53 generates a control signal to control the ON (connect) / OFF (disconnect) of the four hydraulic clutches of the planetary clutch mechanism 37: the first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4. The forward / reverse clutch control unit 54 generates a control signal to control the ON (connect) / OFF (disconnect) of the two hydraulic clutches of the forward / reverse switching device 23: the forward clutch CLF and the reverse clutch CLR.

[0056] The rotation speed acquisition unit 61 includes an engine rotation speed acquisition unit 62, a continuously variable speed rotation speed acquisition unit 63, a planetary rotation speed acquisition unit 64, and a driving rotation speed acquisition unit 65. The engine rotation speed acquisition unit 62 acquires detection signals (a type of detection value), which are engine rotation speed signals, from the main engine rotation detector 71 and the redundant engine rotation detector 72, and determines the engine rotation speed (a type of detection value) of engine 4. The continuously variable speed rotation speed acquisition unit 63 acquires detection signals (a type of detection value, which is a continuously variable speed rotation speed signal) from the main continuously variable speed rotation detector 73, and determines the continuously variable speed rotation speed (a type of detection value). The planetary rotation speed acquisition unit 64 acquires detection signals (a type of detection value, which is a planetary rotation speed signal) from the main planetary rotation detector 74 and the redundant planetary rotation detector 75, and determines, for example, the planetary rotation speed (a type of detection value), which is the rotation speed of the planetary output shaft. The rotational speed acquisition unit 65 acquires detection signals from the main rotational speed detector 76 and the redundant rotational speed detector 77 (a type of detection value that indicates the rotation of the forward and reverse output shafts, for example) to determine the rotational speed (a type of detection value). In this embodiment, only the main continuously variable speed rotation detector 73 is provided for detecting the continuously variable speed rotation, and the redundant continuously variable speed rotation detector is not provided. However, in another embodiment, the redundant continuously variable speed rotation detector may be provided.

[0057] Figure 6 is an explanatory diagram of vehicle speed shifting by the shift control unit 51. The vertical axis of Figure 6 shows the gear ratio: G, which is the ratio (driving speed / engine speed) between the engine speed and the driving speed (vehicle speed), which is the rotational speed of the input shaft 16a to the running gear corresponding to the vehicle speed. The vertical axis also shows the driving speed (vehicle speed): V of the input shaft 16a. The horizontal axis of Figure 6 shows the shift state of the continuously variable transmission 28. [N] indicates the neutral state, and [-MAX] indicates the shift state that outputs the maximum reverse power. [+MAX] indicates the shift state that outputs the maximum forward power. [-K] indicates the shift state for clutch switching on the reverse side (the shift state just before [-MAX]), and [+K] indicates the shift state for clutch switching on the forward side (the shift state just before [+MAX]). [G1], [G2], [G3], and [G4] are preset gear ratios: G. The gear shift control unit 51 controls the rotational speed (vehicle speed): V of the input shaft 16a by switching the first clutch CL1, second clutch CL2, third clutch CL3, and fourth clutch CL4 based on the gear ratio: G and the shift state of the continuously variable transmission 28.

[0058] In other words, with the first clutch CL1 engaged, as the continuously variable transmission 28 shifts from [-MAX] to [+MAX], the vehicle speed (V) increases steplessly from zero [0] in the 1st gear range. When the continuously variable transmission 28 becomes [+K] and the gear ratio G becomes [G1], the shift control means 48 switches the first clutch CL1 to disengage and the second clutch CL2 to engage. With the second clutch CL2 engaged, as the continuously variable transmission 28 shifts towards [-MAX], the vehicle speed (V) increases steplessly in the 2nd gear range. When the continuously variable transmission 28 becomes [-K] and the gear ratio G becomes [G2], the shift control means 48 switches the second clutch CL2 to disengage and the third clutch CL3 to engage. When the continuously variable transmission 28 is shifted toward [+MAX] with the third clutch CL3 engaged, the vehicle speed (V) increases steplessly in the 3rd gear range. When the continuously variable transmission 28 becomes [+K] and the gear ratio G becomes [G3], the shift control means 48 switches the third clutch CL3 to disengage and the fourth clutch CL4 to engage. As the continuously variable transmission 28 shifts toward [-MAX] with the fourth clutch CL4 engaged, the vehicle speed (V) increases steplessly in the 4th gear range.

[0059] [Regarding abnormality detection of rotation detectors] The rotation detector determination unit 60 selects at least one selection determination rule from a plurality of abnormality determination rules based on the clutch operation state (ON / OFF state) of the planetary clutch mechanism 37 and the forward / reverse switching device 23, and uses this selection determination rule to determine abnormalities in each rotation detector.

[0060] The rotation detector abnormalities of the rotation detectors constituting the rotation detector group 70, as determined by the rotation detector determination unit 60, are classified into three categories: a low-level abnormality state that only issues a warning, a moderate-level abnormality state that permits temporary driving, and a severe abnormality state that causes an emergency stop of driving.

[0061] [Anomaly detection rule @1] If communication between the engine control unit EU and the in-vehicle LAN is interrupted, and the engine speed data from the main engine speed detector 71, which is sent periodically, is interrupted, the engine speed is calculated using the detection signal from the redundant engine speed detector 72, and the gear shift control continues. If the redundant engine speed detector 72 has been detected as abnormal in advance, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned OFF, power transmission from the engine 4 is cut off, and the vehicle stops. The engine control unit EU performs abnormality detection of the main engine speed detector 71 and also has a backup function. When the backup function of the engine control unit EU is enabled, gear shift control using the redundant engine speed detector 72 is not performed. The abnormality detection of the main engine speed detector 71 by the engine control unit EU is sent to the speed detector detection unit 60. In other words, in this case, the engine control unit EU functions as the speed detector detection unit 60 of the main engine speed detector 71.

[0062] [Anomaly detection rule @2] If, while engine speed data is being received smoothly from the engine control unit EU, a difference exceeding a threshold condition (mismatch in detected values) occurs between the engine speed from the engine control unit EU and the engine speed from the redundant engine speed detector 72, the redundant engine speed detector 72 is determined to be abnormal. While engine speed data from the engine control unit EU is interrupted, the redundant engine speed detector 72 is not deemed abnormal, and gear shift control is performed using the redundant engine speed detector 72. If only the redundant engine speed detector 72 is abnormal, vehicle operation continues without restriction. A warning that the redundant engine speed detector 72 is abnormal is issued.

[0063] [Anomaly detection rule @3] When the planetary clutch mechanism 37 is ON, the absolute value of the planetary rotation speed calculated from the engine speed and the continuously variable speed rotation speed, the absolute value of the main planetary rotation detector 74, and the redundant planetary rotation detector 75 are compared in pairs. If a difference exceeding a predetermined threshold condition (mismatch in detected values) occurs, an abnormality in the specific rotation detector is determined as follows. The rotation speed from the main continuously variable speed rotation detector 73 is denoted as "Nm", the rotation speed from the main planetary rotation detector 74 as "Ns_m", and the rotation speed from the redundant planetary rotation detector 75 as "Ns_r". (1) If Ns_m and Ns_r are normal, and Nm and Ns_m and Nm and Ns_r are abnormal, the main continuously variable speed rotation detector 73 is determined to be abnormal. (2) If Nm and Ns_r are normal, and Ns_m and Ns_m and Ns_r are abnormal, the main planetary rotation detector 74 is determined to be abnormal. (3) If Nm and Ns_m are normal, and Ns_r and Nm, and Ns_r and Ns_m are abnormal, the redundant planetary rotation detector 75 is determined to be abnormal. If only the main continuously variable speed rotation detector 73 malfunctions, or if only the main planetary rotation detector 74 malfunctions, the forward / reverse selector 23 is set to neutral (even if the forward / reverse selector 23 is not operated when the vehicle speed decreases, if the vehicle speed drops below a certain level, all clutches in the planetary clutch mechanism 37 and all clutches in the forward / reverse selector 23 are turned OFF, causing the vehicle to stop. If only the redundant planetary rotation detector 75 malfunctions, the vehicle continues to travel without restriction. If all three—the main continuously variable speed rotation detector 73, the main planetary rotation detector 74, and the redundant planetary rotation detector 75—malfunction, all clutches in the planetary clutch mechanism 37 and all clutches in the forward / reverse selector 23 are turned OFF (completely disengaged), and the vehicle stops.

[0064] [Anomaly detection rule @4] When the planetary clutch mechanism 37 is in the OFF state (incomplete coupling state), the absolute values ​​of the rotation speeds of the main planetary rotation detector 74 and the redundant planetary rotation detector 75 are compared. If there is a difference exceeding the threshold condition (mismatch in detected values), both the main planetary rotation detector 74 and the redundant planetary rotation detector 75 are determined to be abnormal. If only the main continuously variable speed rotation detector 73 malfunctions, or if both the main planetary rotation detector 74 and the redundant planetary rotation detector 75 malfunction, all clutches in the planetary clutch mechanism 37 and all clutches in the forward / reverse switching device 23 are turned OFF (completely disengaged), and the vehicle stops.

[0065] [Anomaly detection rule @5] When the clutch of the forward / reverse switching device 23 is fully engaged, the rotational speed measured by the main travel rotation detector 76, the rotational speed measured by the redundant travel rotation detector 77, and the rotational speed measured by the main planetary rotation detector 74 are compared in pairs. If a difference exceeding a predetermined threshold condition (mismatch in detected values) occurs, an abnormality in the specific rotation detector is determined as follows. The rotational speed measured by the main travel rotation detector 76 is denoted as "Nv_m", and the rotational speed measured by the redundant travel rotation detector 77 is denoted as "Nv_r". (1) If Nv_r and Ns_m are normal, and Nv_m and Nv_r, and Nv_m and Ns_m are abnormal, the main travel rotation detector 76 is determined to be abnormal. (2) If Nv_m and Ns_m are normal, and Nv_r and Nv_m, and Nv_r and Ns_m are abnormal, the redundant travel rotation detector 77 is determined to be abnormal. (3) If Nv_m and Nv_r are normal, and Ns_m and Nv_m or Ns_m and Nv_r are abnormal, the main planetary rotation detector 74 is determined to be abnormal. (4) If there is a discrepancy between Nv_m and Ns_m that exceeds the threshold condition, the main travel rotation detector 76, the redundant travel rotation detector 77, and the main planetary rotation detector 74 are all judged to be abnormal. If only the main planetary rotation detector 74 malfunctions, the forward / reverse selector 23 is set to neutral (even if the forward / reverse selector 23 is not operated when the vehicle speed decreases, if the vehicle speed drops below a certain level, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse selector 23 are turned OFF, causing the vehicle to stop. If only the main driving rotation detector 76 malfunctions, after the forward / reverse selector 23 is set to neutral, all clutches of the planetary clutch mechanism 37 are turned OFF. If only the redundant driving rotation detector 77 malfunctions, vehicle operation continues without restriction. If the main driving rotation detector 76, redundant driving rotation detector 77, and main continuously variable speed rotation detector 73 all malfunction, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse selector 23 are turned OFF (completely disengaged), and the vehicle stops.

[0066] [Anomaly detection rule @6] If the clutch of the forward / reverse switching device 23 is disengaged (incompletely engaged), the absolute values ​​of the rotational speed detected by the main travel rotation detector 76 and the rotational speed detected by the redundant travel rotation detector 77 are compared. If the difference exceeds a threshold condition, both the main travel rotation detector 76 and the redundant travel rotation detector 77 are determined to be abnormal. If only the main planetary rotation detector 74 is abnormal, all clutches in the planetary clutch mechanism 37 and all clutches in the forward / reverse switching device 23 are turned OFF (completely disengaged), and the vehicle stops.

[0067] Each rotation detector, under conditions where the object being detected is considered to be rotating, indicates a break in the circuit if the detected rotation count is zero. In particular, the main travel rotation detector 76 and the redundant travel rotation detector 77 cannot detect rotation normally unless either the planetary clutch mechanism 37 or the forward / reverse switching device 23 clutch is engaged. Therefore, the break in the circuit is checked only after it has been confirmed that the planetary clutch mechanism 37 and the forward / reverse switching device 23 are in a power transmission state.

[0068] The abnormality detection of the rotation detector group 70 is skipped under the following predetermined conditions. (1) When the vehicle speed is low and rotational speed accuracy decreases. (2) If the engine speed drops to near the point of engine stall due to the load, the abnormality detection is skipped in order to prioritize the control calculation for engine stall. (3) If the rotation speed detected by a specific rotation detector deviates from a predetermined threshold condition, the abnormality detection for the specific rotation detector is skipped.

[0069] [Another embodiment] (1) In the above-described embodiment, a hydrostatic continuously variable transmission 28 was used, but a belt-type continuously variable transmission or a friction-type continuously variable transmission may also be used. (2) The arrangement of each rotation detector constituting the rotation detector group 70 is not limited to the arrangement in the embodiment described above. The rotation detector group 70 can be arranged at any position in which substantially equivalent rotation speeds can be detected. (3) The control function unit included in the gear shift control unit 50 may be integrated with other control function units or may be divided into multiple units. In addition, a specific control function unit may be built into a control unit (ECU) other than the gear shift control unit 50. (4) In the above-described embodiment, the planetary gearbox 31 was shown as being configured to have four gear stages, but it may also be configured to have three or fewer gear stages or five or more gear stages.

[0070] (5) In the embodiments described above, an example with front wheels 1 and rear wheels 2 was shown, but the running gear may be a crawler running gear, or a combination of mini-crawlers and wheels.

[0071] (6) In the above-described embodiment, an example was shown in which a gear shift pedal 46 is provided, but the embodiment is not limited to this, and a gear shift lever may be used as the gear shift operating device 45.

[0072] (7) In the above-described embodiment, an example was shown in which a forward / reverse lever 47 is provided, but the embodiment is not limited to this, and a forward / reverse pedal may be used as the gear shifting device 45.

[0073] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Industrial applicability]

[0074] The present invention relates to a continuously variable speed power transmission system for work vehicles equipped with a continuously variable transmission and a planetary gearbox, and is applicable to various work vehicles equipped with said continuously variable speed power transmission system. [Explanation of Symbols]

[0075] 4: Engine 15: Power transmission device 18: Transmission 20: Input axis 21: Main transmission unit 23: Forward / forward switching device 23a: Input axis 23b: Output shaft 23c: Forward gear interlocking mechanism 23d: Reverse gear interlocking mechanism 28: Continuously Variable Transmission 31: Planetary gearbox 31A: Planetary gearbox 31B: Output section 32: First planetary gearbox 33: Second planetary gearbox 35: Output shaft 37: Planetary clutch mechanism 45: Gear shifter 46: Gear shift pedal 47: Forward / Reverse Lever 48: Gear shift control means 50: Gear shift control unit 51: Gear shift control unit 52: Continuously Variable Speed ​​Control Unit 53: Planetary clutch control unit 54: Forward / reverse clutch control unit 60: Rotation detector determination unit 61: Rotation speed acquisition unit 62: Engine speed acquisition unit 63: Continuously Variable Speed ​​Rotation Speed ​​Acquisition Unit 64: Planetary rotation speed acquisition unit 65: Unit for acquiring vehicle rotation speed 70: Rotation detector group 71: Main engine rotation detector 72: Redundant engine rotation detector 73: Main continuously variable speed control sensor 74: Main planetary rotation detector 75: Redundant planetary rotation detector 76: Main travel rotation detector 77: Redundant travel rotation detector EU: Engine control unit M: Hydraulic motor P: Hydraulic pump

Claims

1. A continuously variable speed power transmission system for a work vehicle that transmits engine power from the engine to the running gear, A continuously variable transmission that receives engine power and outputs continuously variable power, A planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power, A planetary clutch mechanism for selecting the gear ratio of the aforementioned planetary transmission, A forward / reverse switching device that receives the planetary power and outputs forward or reverse power to the running gear, A gear shift control unit generates a control signal that controls the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device based on a gear shift operation command, using the engine speed of the engine, the continuously variable transmission speed which is the rotational speed of the continuously variable transmission power, the planetary rotational speed which is the rotational speed of the planetary power, and the travel speed which is the rotational speed of the forward power or the reverse power. A group of rotation detectors comprising multiple rotation detectors that detect the engine speed, the continuously variable transmission speed, the planetary rotation speed, and the driving speed, The system includes a rotation detector determination unit that determines an abnormality in the rotation detector group using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operating state of the planetary clutch mechanism and the forward / reverse switching device, The rotation detector group includes a main engine rotation detector for detecting the engine rotation speed, a redundant engine rotation detector for detecting the rotation speed of the input shaft that receives engine power as the engine rotation speed, a main continuously variable speed rotation detector for detecting the continuously variable speed rotation speed, a main planetary rotation detector for detecting the planetary rotation speed, a redundant planetary rotation detector for detecting the planetary rotation speed, a main travel rotation detector for detecting the travel rotation speed, and a redundant travel rotation detector for detecting the travel rotation speed, all of which are part of a continuously variable speed power transmission system for work vehicles.

2. A continuously variable speed power transmission device for a work vehicle that transmits engine power from the engine to the running gear, A continuously variable transmission that receives engine power and outputs continuously variable power, A planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power, A planetary clutch mechanism for selecting the gear ratio of the aforementioned planetary transmission, A forward / reverse switching device that receives the planetary power and outputs forward or reverse power to the running gear, A gear shift control unit generates a control signal that controls the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device based on a gear shift operation command, using the engine speed of the engine, the continuously variable transmission speed which is the rotational speed of the continuously variable transmission power, the planetary rotational speed which is the rotational speed of the planetary power, and the travel speed which is the rotational speed of the forward power or the reverse power. A group of rotation detectors comprising multiple rotation detectors that detect the engine speed, the continuously variable transmission speed, the planetary rotation speed, and the driving speed, The system includes a rotation detector determination unit that determines an abnormality in the rotation detector group using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operating state of the planetary clutch mechanism and the forward / reverse switching device, A continuously variable speed power transmission device for a work vehicle, wherein abnormalities in the rotation detector group determined by the rotation detector determination unit are classified into three categories: a low-degree abnormality state that only issues a warning, a moderate-degree abnormality state that permits temporary driving, and a severe abnormality state that causes an emergency stop of driving.

3. A continuously variable speed power transmission device for a work vehicle that transmits engine power from the engine to the running gear, A continuously variable transmission that receives engine power and outputs continuously variable power, A planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power, A planetary clutch mechanism for selecting the gear ratio of the aforementioned planetary transmission, A forward / reverse switching device that receives the planetary power and outputs forward or reverse power to the running gear, A gear shift control unit generates a control signal that controls the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device based on a gear shift operation command, using the engine speed of the engine, the continuously variable transmission speed which is the rotational speed of the continuously variable transmission power, the planetary rotational speed which is the rotational speed of the planetary power, and the travel speed which is the rotational speed of the forward power or the reverse power. A group of rotation detectors comprising multiple rotation detectors that detect the engine speed, the continuously variable transmission speed, the planetary rotation speed, and the driving speed, The system includes a rotation detector determination unit that determines an abnormality in the rotation detector group using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operating state of the planetary clutch mechanism and the forward / reverse switching device, When the clutch operation state of the planetary clutch mechanism is ON, the rotation detector determination unit determines that If the relationship between the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector is normal, the relationship between the detected values ​​of the main continuously variable speed rotation detector and the main planetary rotation detector is abnormal, and the relationship between the detected values ​​of the main continuously variable speed rotation detector and the redundant planetary rotation detector is abnormal, then it is determined that the main continuously variable speed rotation detector is abnormal. If the relationship between the detected values ​​of the main continuously variable speed rotation detector and the redundant planetary rotation detector is normal, the relationship between the detected values ​​of the main planetary rotation detector and the main continuously variable speed rotation detector is abnormal, and the relationship between the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector is abnormal, then it is determined that the main planetary rotation detector is abnormal. A continuously variable speed power transmission device for a work vehicle, which determines that the redundant planetary rotation detector is abnormal if the relationship between the detected values ​​of the main continuously variable speed rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant planetary rotation detector and the main continuously variable speed rotation detector is abnormal, and the relationship between the detected values ​​of the redundant planetary rotation detector and the main planetary rotation detector is abnormal.

4. A continuously variable speed power transmission device for a work vehicle that transmits engine power from an engine to a running gear, A continuously variable transmission that receives engine power and outputs continuously variable power, A planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power, A planetary clutch mechanism for selecting the gear ratio of the aforementioned planetary transmission, A forward / reverse switching device that receives the planetary power and outputs forward or reverse power to the running gear, A gear shift control unit generates a control signal that controls the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device based on a gear shift operation command, using the engine speed of the engine, the continuously variable transmission speed which is the rotational speed of the continuously variable transmission power, the planetary rotational speed which is the rotational speed of the planetary power, and the travel speed which is the rotational speed of the forward power or the reverse power. A group of rotation detectors comprising multiple rotation detectors that detect the engine speed, the continuously variable transmission speed, the planetary rotation speed, and the driving speed, The system includes a rotation detector determination unit that determines an abnormality in the rotation detector group using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operating state of the planetary clutch mechanism and the forward / reverse switching device, When the clutch operation state of the planetary clutch mechanism is in an incomplete coupling state, the rotation detector determination unit determines: A continuously variable speed power transmission device for a work vehicle that determines that both the main planetary rotation detector and the redundant planetary rotation detector are malfunctioning if the detected values ​​of the main planetary rotation detector and the redundant planetary rotation detector do not match.

5. A continuously variable speed power transmission device for a work vehicle that transmits engine power from an engine to a running gear, A continuously variable transmission that receives engine power and outputs continuously variable power, A planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power, A planetary clutch mechanism for selecting the gear ratio of the aforementioned planetary transmission, A forward / reverse switching device that receives the planetary power and outputs forward or reverse power to the running gear, A gear shift control unit generates a control signal that controls the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device based on a gear shift operation command, using the engine speed of the engine, the continuously variable transmission speed which is the rotational speed of the continuously variable transmission power, the planetary rotational speed which is the rotational speed of the planetary power, and the travel speed which is the rotational speed of the forward power or the reverse power. A group of rotation detectors comprising multiple rotation detectors that detect the engine speed, the continuously variable transmission speed, the planetary rotation speed, and the driving speed, The system includes a rotation detector determination unit that determines an abnormality in the rotation detector group using a selection determination rule selected from a plurality of abnormality determination rules based on the clutch operating state of the planetary clutch mechanism and the forward / reverse switching device, When the clutch of the forward / reverse switching device is ON, the rotation detector determination unit determines that If the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is abnormal, and the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is abnormal, then it is determined that the main travel rotation detector is abnormal. If the relationship between the detected values ​​of the main travel rotation detector and the main planetary rotation detector is normal, the relationship between the detected values ​​of the redundant travel rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the redundant travel rotation detector and the main planetary rotation detector is abnormal, then it is determined that the redundant travel rotation detector is abnormal. A continuously variable speed power transmission device for a work vehicle that determines that the main planetary rotation detector is abnormal if the relationship between the detected values ​​of the main travel rotation detector and the redundant travel rotation detector is normal, the relationship between the detected values ​​of the main planetary rotation detector and the main travel rotation detector is abnormal, and the relationship between the detected values ​​of the main planetary rotation detector and the redundant travel rotation detector is abnormal.

6. When the clutch operation state of the forward / reverse switching device is in an incompletely coupled state, the rotation detector determination unit determines: The continuously variable speed power transmission device for a work vehicle according to claim 5, wherein if the detected values ​​of the main travel rotation detector and the redundant travel rotation detector do not match, it is determined that both the main travel rotation detector and the redundant travel rotation detector are abnormal.

7. A work vehicle equipped with a continuously variable speed power transmission device for work vehicles according to any one of claims 1 to 6.

Images