JP2004306956A - Controlling mechanism of vehicle running device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controlling mechanism for a vehicle running device of such a structure that the load of the driven side is sensed and automatic changing-over takes place from the two-wheel driving to the four-wheel driving, whereby the front wheel driving can check the acceleration due to the load of the driven side which enables stable running downward. <P>SOLUTION: The vehicle running device makes automatic changing-over of engine driving from the two-wheel driving to the four-wheel driving and vice versa, wherein the changing-over from the two-wheel driving to the four-wheel is performed in case such a condition is sensed that engine brake is applied and a minus torque as the load of the driven side is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to control for switching from two-wheel drive to four-wheel drive by detecting a driven load of an engine in a working vehicle such as a farming tractor.

In a conventional work vehicle, a power connection / disconnection unit for connecting / disconnecting power transmission to left and right front wheels for switching between a rear wheel drive state and a front / rear wheel drive state is provided.
A configuration in which the switching operation of the power connecting / disconnecting means is switched manually or automatically is disclosed in Japanese Patent Application Laid-Open No. 2-279467.
JP-A-2-279467

As disclosed in Japanese Patent Application Laid-Open No. 2-279467, the power connecting / disconnecting means can be automatically switched, but is switched to the front and rear wheel drive state in conjunction with the brake operation.
When the brake is operated in conjunction with the brake operation, an impact of switching from rear wheel drive to front and rear wheel drive frequently occurs each time the brake is operated, and this causes anxiety for the operator.
Also, particularly when pulling down a trolley loaded with heavy objects at the rear of the tractor, especially when the tractor is tow a cart with a rear wheel driven state, the load on the driven side is applied due to the weight of the cart, and the rear wheels are accelerated. The brake was not applied and running stability was poor.

The present invention uses the following means to solve such a problem.
In a traveling device capable of automatically switching the engine drive between two-wheel drive and four-wheel drive, when a state where the engine brake is applied and a negative torque that is a driven load is generated is detected, the two-wheel drive is performed. This is a traveling device control mechanism that automatically switches from driving to four-wheel drive.

With this configuration, the following effects can be obtained.
2. Description of the Related Art A traveling vehicle of a two-wheel / four-wheel drive switching type. For example, in a towing traveling vehicle (tractor), in the case of towing a wagon loaded with a heavy object and descending a hill, the driving of the wagon during the two-wheel drive is performed. Due to the weight, the driven wheels may be accelerated to generate a driven-side load and the engine brake may not be effective. However, the present invention detects the driven-side load and automatically switches from two-wheel drive to four-wheel drive. By doing so, the front-wheel drive stops acceleration due to the driven-side load, and enables stable downhill travel.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a plan view of a tractor T on which a rotary working machine R is mounted.
FIG. 2 is a plan view showing a driving force transmission configuration of the tractor T,
FIG. 3 is a block diagram showing a control structure of an engine with an electronic governor;
FIG. 4 is a flowchart for controlling the electronic governor by detecting a change in engine load;
FIG. 5 is a correlation diagram between the engine speed and the load factor under a certain working condition;
FIG. 6 is a diagram showing an output characteristic map of the engine.
FIG. 7 is a table showing the relationship between the rack position of the fuel injection pump and the engine speed.
FIG. 8 is a flowchart illustrating switching control from two-wheel drive to four-wheel drive.

  1 and 2, a power transmission configuration of the tractor T will be described. An engine E is disposed inside the hood 2 at the front of the tractor T, and an electronic governor G is attached to a side surface of the engine E. A traveling clutch 23 is disposed in a clutch housing portion on the rear surface of the engine E, and a multi-speed clutch type speed change traveling device TM is disposed in a rear portion thereof.

  A rear axle case is disposed at the rear of the transmission TM, and power is transmitted via a power transmission shaft 4. A gear-type auxiliary transmission and a differential gear device 5 are provided inside the rear axle case. The rear wheels 7, 7 are driven via the differential gear device 5, and a PTO shaft (not shown) projects from the rear surface of the differential gear device 7. Power is transmitted via a universal joint to an input shaft of a working machine such as a rotary cultivator R mounted on the lifting link 12 at the rear of the tractor T so as to be able to move up and down.

  A front wheel power transmission shaft 16 is driven through a gear mechanism 15 in the middle of the power transmission shaft 4 so as to transmit power to the front wheels 6 via a front wheel differential gear device 17. . A power connection / disconnection unit 18 is provided at an intermediate portion of the front wheel power transmission shaft 16. The power connecting / disconnecting means 18 is constituted by, for example, a hydraulic clutch, and a switching lever provided in the operating section turns ON / OFF an electromagnetic valve in the middle of a hydraulic oil supply path to the hydraulic clutch, thereby driving the front and rear wheels ( (4 wheel drive) and rear wheel drive state (2 wheel drive).

  In addition, a hydraulic cylinder for adjusting the tillage depth is arranged on the elevating link 12 to which the rotary tiller R is mounted, and an electromagnetic valve is operated in accordance with the setting of the tillage depth setting lever 21 to set the tillage. The rotary tiller R is driven down to the depth position. Further, an accelerator lever AL and an accelerator lever sensor S1 are arranged beside the steering wheel. The engine E is provided with a torque sensor S8 (not shown) for detecting a load, and detects a load applied to an output shaft of the engine E.

Next, a control method of the engine E with the electronic governor G will be described.
The fuel injection amount of the engine E is controlled by an electronic governor G. A control unit (controller) C is connected to the electronic governor G, and the output value of the rack actuator RA for adjusting the fuel injection amount is calculated based on various detected values. The control structure of the electronic governor G is, as shown in FIG. 3, an electronic governor G for controlling a rack actuator RA for adjusting a fuel injection amount connected to a fuel injection pump P, and a control unit C for: Output signals are issued to the electronic governor G based on input values of various sensors and various switches.

  The control unit C has a built-in ROM for storing an output control map for the engine speed, a RAM for writing a correction value of the accelerator setting speed described later, and a microcomputer CPU as arithmetic means, and has an input port IP and an output port. An OP is provided.

  Various sensors are also used as input means of the control unit C. The accelerator lever AL has an accelerator sensor S1 for detecting an accelerator setting rotational speed, and the electronic governor G has a rack position sensor S2 for detecting a position of a fuel injection amount adjusting rack. , A rotation sensor S3 for detecting an engine speed, and a temperature sensor S4 for detecting a temperature of a cooling system such as lubricating oil or water in the engine E, and a detection signal of these sensors is supplied to an input port of the control unit C. The microcomputer CPU calculates the output value of the rack actuator RA or the output value to the traveling transmission device TM by comparing the output value with the control map transmitted to the IP and stored in the ROM or the like. An output signal is launched to the TM.

  In the present invention, when it is determined that the working state is the working state by confirming that the working position is the working position of the working machine, that the body is running, and that the PTO drive shaft is driven, the rotary tiller R is used. The control is performed according to the flowchart shown in FIG. 4 so as to prevent a sudden change in the engine speed during the operation. That is, when the control unit C determines that the vehicle is in the working state, the electronic control unit G detects the load on the engine E. As means for detecting the engine load, a rack position sensor S2 is mainly used, and in addition, a rotation sensor S3, a temperature sensor S4, and the like are also used.

In the tractor according to the present embodiment, an average value of the engine load (load factor) is calculated at intervals of several seconds, and control for changing the accelerator setting rotational speed can be performed so that the average value is in an optimal state. .
The load factor indicates the ratio of the actual output value to the maximum output set for each set engine speed based on the output control map stored in the control unit C. Set to 0.

  This load is calculated based on the rack position (fuel injection amount), and indicates the ratio of the actual rack position to the rack maximum position set by the engine setting rotation speed. The maximum rack position and the actual rack position are based on the idling rack position at the engine speed.

First, a description will be given of a change in the accelerator setting rotation speed and a change in the load factor associated therewith with reference to FIG. The graph of FIG. 5 shows that certain working conditions (for example, the rotary tiller R is held at a certain plowing depth, and the main transmission lever ML, the sub transmission lever SL, and the PTO transmission lever PL are kept in a running state. Under (), how the load factor L changes by changing the engine speed N is illustrated.
The load factor fluctuates during the work even under the same engine speed (for example, fluctuates within the range of L _{1 to} L ₂ ). L _A in the figure indicates the variation of the average load factor for each engine setting rotational speed. As can be seen from this graph, the load factor (average load factor L _A ) under the same working conditions increases as the set engine speed increases.

In order to perform the work with the maximum efficiency with the tractor T, the rotation speed N ₀ at which the load factor becomes 100% may be set with the accelerator lever AL. However, when the load fluctuation is large (for example, when the soil is heterogeneous), in a high load state with a load factor of about 100% as described above, a measure is taken by torque control (that is, the rack in the electronic governor G). Since the position is kept at the maximum position, the engine speed is reduced.) Therefore, the actual engine speed frequently fluctuates with a considerable fluctuation width, and the vehicle speed becomes unstable.

In this embodiment, in order to avoid such a problem, control is performed to correct the accelerator setting rotation speed to a range in which constant speed control is possible, based on the average load factor during operation for a certain period. As shown in the flowchart of FIG. 4, the control unit C calculates an average load factor which is an average value of the engine load.
In this control, an appropriate average load factor is set between 85% and 95%. If the detected average load factor is in this range, the output is slightly low, but the vehicle speed is stable because constant speed control is performed. And the work efficiency is not so bad. Therefore, in this case, the accelerator setting rotation speed is kept at the current state (for example, the setting rotation speed N _{1 at} which the average load factor becomes 90% shown in FIG. 5).

When it is determined that the average load factor value is high, for example, when the load factor is 95% or more, the accelerator setting rotational speed (for example, the set rotational speed N ₀ at which the average load factor becomes 100% in FIG. 5) is set at the present time. Is corrected to a value lower than the number of rotations (95% of the current number of rotations). When the governor control is performed after the set rotation speed is corrected in this way, the average load factor falls within an appropriate range (85% to 95%), and the vehicle speed becomes stable.
In addition to or instead of the control for correcting the accelerator setting rotation speed, it is possible to perform a deceleration operation in order to secure a torque by increasing the reduction ratio of the traveling transmission TM, which is the conventional control. In addition, or instead of this, it is possible to reduce the speed of the PTO drive in order to increase the speed reduction ratio.

Also, if the average load factor is too low, the work efficiency deteriorates. Therefore, if it is determined that the average load is low, the accelerator setting rotational speed (for example, the set rotational speed N _{2 at} which the load factor becomes 85% or less in FIG. 5) is set at the present time. Is changed to a higher value (105% of the current number of revolutions) than the number of revolutions at. As a result, the average load factor is in an appropriate range (85% to 95%), and the work efficiency is improved while maintaining the vehicle speed stability by constant speed control. In addition to or instead of this control, it is also possible to operate the speed increasing side to reduce the reduction ratio of the traveling transmission TM which is the conventional control, and further to reduce the reduction ratio of the PTO drive. It is also possible to increase this.

Thereafter, the average load is detected at regular intervals, and this control is repeated.
However, even if the engine set speed is set lower than the actual accelerator set speed and the load ratio is maintained at 85% to 95%, when a high load is instantaneously applied, this load is output. And the engine speed may drop.
Therefore, the control unit C detects the instantaneous load at each time point separately from the average load, compares the instantaneous load at each time point of the fluctuating load with the maximum load at the set rotation speed, and determines that the instantaneous load is the maximum. Determine if it is greater than the load.

  When the instantaneous load is large (for example, when the rotary cultivator R hits an obstacle such as a stone and rapidly increases the load), the above-described lifting cylinder is used to reduce the load on the working machine. By switching the electromagnetic valve, the tillage depth of the rotary tiller R is increased by a certain distance (for example, 1 cm). Alternatively or simultaneously, a signal is sent to the rack actuator RA of the electronic governor G so that the engine output is increased at a fixed rate (for example, 10%), as shown by the dotted line in FIG. It is also possible to send. Since the constant speed control is originally performed at a lower output than the maximum output, there is a margin for increasing the output, and the output limit at the time of the instantaneous load excess shown in FIG. As a result, there is no possibility that the working machine will be subjected to excessive engine torque and lead to damage.

Next, the automatic switching control of two-wheel / four-wheel drive according to the fluctuation of the engine torque according to the present invention will be described.
According to the load (torque) of the engine E, the control unit C is used to operate the power connecting / disconnecting means 18 for connecting / disconnecting power transmission to the front wheels to perform 2WD / 4WD automatic switching control. A torque sensor S8 for detecting the torque of the engine E is connected to the control unit C. The torque sensor S8 is disposed on the crankshaft of the engine E, and when torque due to rotation of the drive wheels during downhill driving or the like is added to torque (drive-side load) for transmitting the engine output to the drive wheels. Is detected as a negative load (torque) (driven side load), and the detected value is input to the input port IP of the control unit C.

  As a condition for activating this control, in the 2WD / 4WD automatic switching state, after confirming that the vehicle is traveling by two-wheel drive, the engine torque is measured and the vehicle is switched to four-wheel drive. We need a way to check the status. As means therefor, first, as shown in FIG. 2, there is a mode sensor S5 as means for detecting that the 2WD / 4WD automatic changeover switch is ON. Further, as a means for confirming that the vehicle is traveling by two-wheel drive at the present time, there is a traveling sensor S6 for detecting that the power connecting / disconnecting means 18 is disconnected. Further, as means for confirming that the vehicle is traveling, a clutch sensor S7 for confirming that the traveling clutch 23 is connected is used. Each of the sensors S5, S6, S7 is connected to the input port IP of the control unit shown in FIG.

Control of 2WD / 4WD automatic switching performed based on the above-described confirmation means is controlled as shown in the flowchart of FIG. First, it is determined by the mode sensor S5 that the 2WD / 4WD automatic switch is operating in the automatic switching state. Then, it is determined whether the vehicle is in the two-wheel running state by using the running sensor S6.
Next, when it is determined by the travel sensor S6 that the travel clutch 23 is connected and the vehicle is in the traveling state, the control unit C detects the load of the engine E.

  Then, it is determined whether the value detected by the torque sensor S8 is negative. If it is determined that the torque is minus (power is transmitted to the engine from the drive wheel side, that is, a state in which the engine brake is operating), then a change in the engine speed is detected. When it is determined that the rotation speed is increasing (that is, the vehicle is traveling on a downhill), the control unit C transmits an output signal to connect the power by the power connection / disconnection unit 18. Further, even when it is determined that the rotational speed is not increasing, the rate of decrease in the rotational speed is determined, and the rate of decrease is small (that is, the engine brake does not work sufficiently and the deceleration is insufficient). When the judgment is made, the output signal is transmitted to connect the power by the power connection / disconnection means 18. Further, the torque sensor S8 has a built-in self-diagnosis function. Even when it is determined that the value detected by the torque sensor S8 is not negative, if the failure of the sensor S8 is diagnosed, the power is cut off. A control signal is transmitted so as to connect the power by the contact means 18, and the vehicle is switched to four-wheel drive so that the vehicle is driven. Can be.

Further, in order to perform 2WD / 4WD automatic switching control according to the load (torque) of the engine E, the torque sensor S8 is used to detect the negative torque. However, the rack position sensor S2 and the rotation sensor S3 are used. Alternatively, a configuration for detecting a negative torque may be adopted. The configuration will be described with reference to FIG.
FIG. 7 shows a map of the rack position R at the engine speed N. R _MAX in the figure, the maximum rack position in each rotational speed N corresponding to the output characteristic map.
R _IDL is a rack position (idling rack position) at which no engine load is applied, R _MIN is a minimum rack position at each rotation speed N, and the fuel injection amount is zero. An area Z surrounded by R _IDL and R _MIN is an area where the engine brake is applied by idling rotation, and at the same time, an area Z where the engine E is turned by the driving force from the driving wheels to generate a negative torque. It is with. (Note that, when the engine is cold, since the injection amount is required to be large even when there is no load when the engine is cold, it fluctuates as the idling rotation R _IDL is corrected upward.) In the case of lowering, if the rack position is set to the lower side along the map i (the accelerator lever AL is loosened to reduce the speed), the engine brake is normally applied from the X position in the figure due to idling rotation. However, when a negative torque is generated in this range, even when the rack position is lowered to the minimum position, that is, a position where the fuel injection amount is 0, the engine speed increases as shown in map j. It will do.

  Therefore, even if the rack position is at the minimum position where the fuel injection amount is 0, the rotational speed increases, or even if the rotational speed decreases, the decrease amount is small, and the negative torque Can be determined to occur, and 2WD / 4WD automatic switching control is performed in accordance with the load (torque) of the engine E without disposing the expensive torque sensor S8 for detecting a negative load (torque) in the engine. can do.

FIG. 3 is a plan view of a tractor T to which the rotary working machine R is mounted. FIG. 3 is a plan view showing a driving force transmission configuration of the tractor T. It is a block diagram showing a control structure of an engine with an electronic governor. It is a flowchart figure which detects the load fluctuation of an engine and controls an electronic governor. FIG. 4 is a correlation diagram between an engine speed and a load factor under a certain operation condition. FIG. 6 is a diagram showing an output characteristic map of the engine. 4 is a table showing a relationship between a rack position of a fuel injection pump and an engine speed. It is a flowchart figure which performs switching control from two-wheel drive to four-wheel drive.

Explanation of reference numerals

C control unit E engine G electronic governor L load factor R work machine T tractor

Claims (1)

  In a traveling device capable of automatically switching the engine drive between two-wheel drive and four-wheel drive, when a state where the engine brake is applied and a negative torque that is a driven load is generated is detected, the two-wheel drive is performed. A traveling device control mechanism which automatically switches from driving to four-wheel drive.

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