JP3955045B2 - Tractor engine brake control mechanism - Google Patents

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 farm tractor.

The conventional work vehicle is provided with power connection / disconnection means for connecting / disconnecting power transmission to the left and right front wheels in order to switch between the rear wheel drive state and the front and rear wheel drive state. A structure for switching the switching operation of the power connection / disconnection means by manual or automatic operation is known from JP-A-2-279467.
JP-A-2-279467

  As described in Japanese Patent Laid-Open No. 2-279467, the power connection / disconnection means can be switched automatically. However, it is configured to switch to the front and rear wheel drive state in conjunction with the brake operation. If the structure is made to be interlocked with the brake operation, the impact of switching from the rear wheel drive to the front and rear wheel drive frequently occurs every time the brake is operated, which makes the operator feel uneasy. Also, especially when towing a wagon loaded with heavy objects at the rear of the tractor when driving down a slope with the rear wheel driven, the load on the driven side is applied by the weight of the wagon and acceleration is applied to the rear wheel. The brakes were not applied and the running stability was poor.

The present invention uses the following means in order to solve such problems.
Power transmission / disconnection means (18) for performing automatic switching control of 2WD / 4WD by connecting / disconnecting power transmission to the front wheel according to the load torque of the engine (E), and having an electronic governor (G) of the engine (E) The control unit (C) includes a torque sensor (S8) that detects that a negative load torque, which is a driven load during downhill traveling, is applied to the crankshaft of the engine (E), and 2WD / 4WD automatic switching. A mode sensor (S5) which is a means for detecting that the switch is ON, a travel sensor (S6) of a power connection / disconnection means (18) for confirming that the vehicle is currently traveling by two-wheel drive, The clutch sensor (S7) of the traveling clutch (23) that confirms driving is connected, and it is confirmed that the control state is traveling by two-wheel drive with 2WD / 4WD automatic switching, and the engine (E ) When the load torque is measured and the engine braking state in which the negative torque that is the driven load is generated is detected, the fluctuation in the rotation speed of the engine (E) is detected next, and the rotation speed is increasing. In some cases, it is determined that the vehicle is traveling on a downhill, the two-wheel drive is automatically switched to the four-wheel drive, and the engine speed is also determined when it is determined that the engine (E) has not increased. The tractor engine brake control mechanism automatically switches from two-wheel drive to four-wheel drive. is there.

With this configuration, the following effects can be obtained.
Power transmission / disconnection means (18) for performing automatic switching control of 2WD / 4WD by connecting / disconnecting power transmission to the front wheel according to the load torque of the engine (E), and having an electronic governor (G) of the engine (E) The control unit (C) includes a torque sensor (S8) that detects that a negative load torque, which is a driven load during downhill traveling, is applied to the crankshaft of the engine (E), and 2WD / 4WD automatic switching. A mode sensor (S5) which is a means for detecting that the switch is ON, a travel sensor (S6) of a power connection / disconnection means (18) for confirming that the vehicle is currently traveling by two-wheel drive, The clutch sensor (S7) of the traveling clutch (23) that confirms driving is connected, and it is confirmed that the control state is traveling by two-wheel drive with 2WD / 4WD automatic switching, and the engine (E ) When the load torque is measured and the engine braking state in which the negative torque that is the driven load is generated is detected, the fluctuation in the rotation speed of the engine (E) is detected next, and the rotation speed is increasing. In some cases, it is determined that the vehicle is traveling on a downhill, the two-wheel drive is automatically switched to the four-wheel drive, and the engine speed is also determined when it is determined that the engine (E) has not increased. The tractor engine brake control mechanism automatically switches from two-wheel drive to four-wheel drive. because, a traveling vehicle 2 wheel-4-wheel drive switching type, for example, the tractor traveling vehicle (tractor), when such down the hill by pulling a cart for mounting heavy, two-wheel drive Sometimes on the weight of the cart Thus, the driven wheels are accelerated and a driven load is generated, and the engine brake may not be effective. However, in the present invention, the driven load is detected and automatically switched from two-wheel drive to four-wheel drive. As a result, the front-wheel drive prevents acceleration due to the driven load, and enables stable down-travel.

  Embodiments of the present invention will be described with reference to the accompanying drawings. 1 is a plan view of a tractor T on which a rotary work 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, and FIG. FIG. 5 is a flow chart for controlling the electronic governor by detecting the load fluctuation of FIG. 5, FIG. 5 is a correlation diagram between the engine speed and the load factor under a constant working condition, and FIG. 6 is a diagram showing an engine output characteristic map. 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 for switching control from two-wheel drive to four-wheel drive.

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

  A rear axle case is disposed at the rear of the speed change traveling device TM, and power is transmitted through the power transmission shaft 4. A gear-type sub-transmission device and a differential gear device 5 are housed inside the rear axle case, and the rear wheels 7 and 7 are driven via the differential gear device 5 to project a PTO shaft (not shown) from the rear surface of the differential gear device 7. Power is transmitted via a universal joint to the input shaft of a working machine such as a rotary tiller R mounted on the lifting link 12 so as to be movable up and down at the rear part of the tractor T.

  In the middle of the power transmission shaft 4, a front wheel power transmission shaft 16 is driven via a gear mechanism 15, and power is transmitted to the front wheels 6 and 6 via a front wheel differential gear device 17. Yes. A power connection / disconnection means 18 is interposed in the middle 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 is used to turn on and off an electromagnetic valve in the middle of the pressure oil supply path to the hydraulic clutch, thereby driving the front and rear wheels ( Switching between four-wheel drive) and rear-wheel drive state (two-wheel drive).

  The lifting link 12 to which the rotary tiller R is mounted is provided with a hydraulic cylinder for adjusting the tilling depth, and the tillage set by operating the electromagnetic valve according to the setting of the tilling depth setting lever 21. The rotary cultivator R is driven down to the depth position. Further, an accelerator lever AL and an accelerator lever sensor S1 are arranged beside the steering handle. The engine E is provided with a torque sensor S8 (not shown) that detects a load, and detects the load applied to the output shaft of the engine E.

  Next, a method for controlling 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 controller (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 detection values. As shown in FIG. 3, the electronic governor G has a control structure in which a fuel injection pump P is connected to an electronic governor G that controls a rack actuator RA for adjusting the fuel injection amount. An output signal is issued to the electronic governor G based on input values of various sensors and various switches.

  The control unit C includes a ROM for storing an output control map for the engine speed, a RAM for writing a correction value for an accelerator setting speed described later, and a microcomputer CPU as a calculation means. A port OP is provided.

  As the input means of the control unit C, the accelerator lever AL has an accelerator sensor S1 that detects the set speed of the accelerator, and the electronic governor G has a rack position sensor S2 that detects the position of the fuel injection amount adjustment rack. , A rotation sensor S3 for detecting the engine speed, and a temperature sensor S4 for detecting the temperature of a cooling system such as lubricating oil or water in the engine E are provided. The microcomputer CPU calculates the output value of the rack actuator RA or the output value to the travel transmission device TM by comparing with the control map transmitted to the IP and stored in the ROM or the like, and the rack actuator RA or the travel disguise device An output signal is launched to TM.

  And in this invention, when it is judged that it is a working state by confirming that it is a working position of a working machine, that the machine is traveling, and that the PTO drive shaft is driven, the rotary tiller R is used. In order to prevent sudden fluctuations in the engine speed during the operation, the control is performed according to the flowchart shown in FIG. That is, when the control unit C determines that it is in the working state, the electronic control unit G detects the load of the engine E. As a means for detecting the engine load, the rack position sensor S2 is mainly used, and a rotation sensor S3, a temperature sensor S4, and the like are also used.

  In the tractor of 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 set rotational speed can be performed so that this average value is in an optimum state. . The load factor indicates the ratio of the actual output value to the maximum output set for each engine setting speed based on the output control map stored in the control unit C. The load factor is in an idling state. 0.

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

First, the change in the accelerator set rotation speed and the accompanying change in the load factor will be described with reference to FIG. The graph of FIG. 5 holds constant working conditions (for example, the rotary tiller R is held at a fixed plowing depth, and the main transmission lever ML / sub transmission lever SL and the PTO transmission lever PL are held in a traveling state. ) Shows how the load factor L varies by changing the engine speed N. Since the load factor fluctuates during work even under the same engine speed (for example, fluctuates within the range of L _{1 to} L ₂ ), the average load factor due to work for a certain period under a constant engine speed N L _A in the figure indicates the fluctuation of this average load factor for each engine set rotational speed. As can be seen from this graph, it can be seen that the load factor (average load factor L _A ) under the same working condition increases as the engine set rotational speed increases.

In order to perform the maximum efficiency work with the tractor T, the rotation speed N ₀ at which the load factor is 100% may be set with the accelerator lever AL. However, when the load fluctuation is large (for example, when the soil is inhomogeneous), as described above, in the high load state where the load factor is around 100%, the torque control is used (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 range, and the vehicle speed becomes unstable.

In this embodiment, in order to avoid such a problem, control is performed to correct the accelerator set rotational speed to a range where constant speed control is possible based on the average load factor during work for a certain period of time. As shown in the flowchart of FIG. 4, the control unit C calculates an average load factor that 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 within this range, the output is slightly low, but the vehicle speed is stable because constant speed control is performed. And work efficiency is not so bad. Therefore, in this case, the accelerator set rotation speed is maintained at the current state (for example, the set rotation speed N _{1 at} which the average load factor is 90% shown in FIG. 5).

If it is determined that the average load factor value is high, for example, when the load factor is 95% or more, the accelerator set revolution number (for example, the set revolution number N ₀ at which the average load factor is 100% in FIG. 5) is The value is corrected to a value lower than the rotation number (95% of the current rotation number). When the governor control is performed after correcting the set rotational speed 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 in place of this accelerator setting rotation speed correction control, it is also possible to perform a deceleration operation in order to secure torque by increasing the reduction ratio of the traveling transmission apparatus TM which is a conventional control. In addition to this, or alternatively, it is possible to decelerate the PTO drive so as to increase the reduction ratio.

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 set rotation speed (for example, the set rotation speed N _{2 at} which the load ratio is 85% or less in FIG. The set rotational speed is changed to a value higher than the rotational speed at (105% of the current rotational speed). As a result, the average load factor falls within an appropriate range (85% to 95%), and the work efficiency is increased while maintaining the vehicle speed stability by the constant speed control. In addition to or instead of this control, it is possible to operate to the speed increasing side in order to reduce the speed reduction ratio of the conventional traveling transmission TM, and to further reduce the speed reduction ratio of the PTO drive. It is also possible to increase the speed.

  Thereafter, the average load is detected at regular intervals, and this control is repeated. However, even when the engine speed is set lower than the actual accelerator speed and maintained at a load factor of 85% to 95%, this load is output when a high load is applied instantaneously. There may be a case where the engine speed decreases. Therefore, in the control unit C, the instantaneous load at each time point is detected separately from the average load, and the instantaneous load at each time point of the fluctuating load is compared with the maximum load at the set rotational speed so 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 tiller R hits an obstacle such as a stone and increases the load suddenly), the above-described lifting cylinder is used to reduce the load on the working machine. By switching the electromagnetic valve, the tilling depth of the rotary tiller R is increased by a certain distance (for example, 1 cm). Instead, or at the same time, a signal is sent to the rack actuator RA of the electronic governor G to increase the engine output at a constant rate (for example, 10%), as in the case of the output limitation when the instantaneous load is excessive as indicated 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 to increase the output, and the output limit when the instantaneous load is excessive as shown in FIG. 6 is also set below the maximum output of this set rotation speed. As a result, excessive engine torque is not applied to the work equipment, which can lead to damage.

  Next, the automatic switching control of the two-wheel / four-wheel drive accompanying the fluctuation of the engine torque of the present invention will be described. In accordance with the load (torque) of the engine E, the control section C is used to operate the power connection / disconnection means 18 for connecting / disconnecting power transmission to the front wheels to perform 2WD / 4WD automatic switching control. A torque sensor S8 that detects the torque of the engine E is connected to the controller C. The torque sensor S8 is disposed on the crankshaft of the engine E, and the torque (drive-side load) that transmits the engine output to the drive wheels is added with the torque due to the rotation of the drive wheels during downhill travel. In addition, a negative load (torque) (driven load) is detected, and the detected value is input to the input port IP of the control unit C.

As a condition for operating this control, in the 2WD / 4WD automatic switching state, it is confirmed that the vehicle is traveling by two-wheel drive, and the engine torque is measured and switched to four-wheel drive. We need a way to check the status. As the means, first, as shown in FIG. 3, there is a mode sensor S5 as a 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 that detects that the power connection / disconnection means 18 is disconnected. Furthermore, a clutch sensor S7 for confirming that the traveling clutch 23 is connected is used as a means for confirming that the traveling drive is being performed. Each sensor S5, S6, S7 is connected to the input port IP of the control unit shown in FIG.

  The control of the 2WD / 4WD automatic switching performed based on the confirmation means as described above is controlled as shown in the flowchart of FIG. First, it is determined by the mode sensor S5 that the 2WD / 4WD automatic changeover switch is operating in the automatic changeover state. And it is judged whether it is a two-wheel driving state using driving sensor S6. Next, when it is determined by the traveling sensor S6 that the traveling clutch 23 is connected and the traveling clutch 23 is in the traveling state, the control unit C is used to detect the load of the engine E.

  And it is judged whether the detected value by torque sensor S8 is minus. If it is determined that the torque is negative (power is transmitted to the engine from the drive wheel side, so-called engine brake is in operation), then fluctuations in the engine speed are detected. When it is determined that the rotational speed is increasing (that is, traveling on a downhill), the control unit C transmits an output signal so that power is connected by the power connection / disconnection means 18. Further, even when it is determined that the rotational speed has not increased, 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 deceleration is insufficient). If it judges, the output signal is transmitted so that power may be connected by the power connection / disconnection means 18. Further, the torque sensor S8 has a built-in self-diagnosis function, and even if it is determined that the detection value by the torque sensor S8 is not negative, if a failure of the sensor S8 is diagnosed, A control signal is transmitted so that power is connected by the contact means 18, the vehicle is switched to four-wheel drive, and the acceleration by the load on the driven side is prevented by driving the front wheel which does not apply the weight of the cart pulled to the rear. Can do.

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, but the rack position sensor S2 and the rotation sensor S3 are used. Also, it can be configured to detect negative torque. 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 is the maximum rack position at each rotation speed N corresponding to the output characteristic map. R _IDL is the rack position (idling rack position) at which the engine load is unloaded, R _MIN is the minimum rack position at each rotational speed N, and the fuel injection amount is zero. A region Z surrounded by R _IDL and R _MIN is a region where the engine brake is applied by idling rotation, and at the same time, a region Z where the engine E is turned by the driving force from the drive wheels and negative torque is generated. It is also. (Note that this region Z fluctuates as the idling rotation R _IDL is corrected upward because a large injection amount is required even when there is no load when the engine is cold.) When descending, if the rack position is made smaller along the map i (decelerate the accelerator lever AL and decelerate), the engine brake is normally applied from the X position in the figure by idling rotation. However, when a negative torque is generated in this range, the engine speed increases as shown in the map j even when the rack position is lowered to the minimum position, that is, the position where the fuel injection amount becomes zero. It will be done.

  Therefore, if the rack position is at the minimum position where the fuel injection amount is 0 and the rotational speed increases, or if the rotational speed decreases but the downward speed is small, the negative torque 2WD / 4WD automatic switching control according to the load (torque) of the engine E without disposing an expensive torque sensor S8 for detecting a negative load (torque) in the engine. can do.

It is a top view of the tractor T which mounts the rotary working machine R. 3 is a plan view showing a driving force transmission configuration of a tractor T. FIG. It is a block diagram which shows the control structure of an engine with an electronic governor. It is a flowchart figure which detects the load fluctuation | variation of an engine and controls an electronic governor. FIG. 4 is a correlation diagram between engine speed and load factor under a constant work condition. FIG. 6 is a diagram showing an engine output characteristic map. It is a table | surface which shows the relationship between the rack position of a fuel injection pump, and an engine speed. It is a flowchart figure which performs switching control from 2 wheel drive to 4 wheel drive.

Explanation of symbols

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

Claims (1)

Power transmission / disconnection means (18) for performing automatic switching control of 2WD / 4WD by connecting / disconnecting power transmission to the front wheel according to the load torque of the engine (E), and having an electronic governor (G) of the engine (E) The control unit (C) includes a torque sensor (S8) that detects that a negative load torque, which is a driven load during downhill traveling, is applied to the crankshaft of the engine (E), and 2WD / 4WD automatic switching. A mode sensor (S5) which is a means for detecting that the switch is ON, a travel sensor (S6) of a power connection / disconnection means (18) for confirming that the vehicle is currently traveling by two-wheel drive, The clutch sensor (S7) of the traveling clutch (23) that confirms driving is connected, and it is confirmed that the control state is traveling by two-wheel drive with 2WD / 4WD automatic switching, and the engine (E ) When the load torque is measured and the engine braking state in which the negative torque that is the driven load is generated is detected, the fluctuation in the rotation speed of the engine (E) is detected next, and the rotation speed is increasing. In some cases, it is determined that the vehicle is traveling on a downhill, the two-wheel drive is automatically switched to the four-wheel drive, and the engine speed is also determined when it is determined that the engine (E) has not increased. The tractor is characterized by automatically switching from two-wheel drive to four-wheel drive when the rate of lowering is determined, and when the rate of lowering is small, and it is determined that engine braking does not work sufficiently and deceleration is insufficient. Engine brake control mechanism.

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