Working vehicle

A working vehicle includes a PTO shaft to transmit power of a propulsion shaft, a PTO clutch including a first rotor to be rotated by the power of the propulsion shaft, a second rotor to transmit the power to the PTO shaft, a press to be moved by a pressure of operation fluid between an engaging side on which the first rotor is engaged with the second rotor and a disengaging side, and a PTO brake to brake the PTO shaft when the press is positioned on the disengaging side, a control valve to control the pressure of the operation fluid to be applied to the PTO clutch, a rate setter to set a reducing rate at which the pressure of the operation fluid is reduced, and a controller to control the control valve based on the reducing rate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2019-109104 filed on Jun. 11, 2019. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a working vehicle.

2. Description of Related Art

As a technique for braking a PTO shaft in a working vehicle such as a tractor, a technique disclosed in Japanese Unexamined Patent Publication No. 2007-269061 is previously known. The working vehicle disclosed in Japanese Unexamined Patent Publication No. 2007-269061 includes a PTO brake configured to brake the revolving of a PTO shaft in synchronization with a PTO clutch, and the PTO brake has a friction plate and a braking plate.

SUMMARY OF THE INVENTION

A working vehicle includes: a PTO shaft to transmit, to a working device, power of a propulsion shaft through which power of a prime mover is transmitted; a PTO clutch including: a first rotor to be rotated by the power of the propulsion shaft; a second rotor to transmit the power to the PTO shaft; a press to be moved by a pressure of operation fluid between an engaging side on which the first rotor is engaged with the second rotor and a disengaging side on which the first rotor is disengaged from the second rotor; and a PTO brake to brake the PTO shaft when the press is positioned on the disengaging side; a control valve to control the pressure of the operation fluid to be applied to the PTO clutch; a rate setter to set, with the control valve, a reducing rate at which the pressure of the operation fluid is reduced; and a controller to control the control valve based on the reducing rate set by the rate setter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

FIG. 8is a side view showing a working vehicle1according to a first preferred embodiment of the present invention.FIG. 8is a plan view showing the working vehicle1according to the present preferred embodiment. In the present preferred embodiment, the working vehicle1is a tractor. However, the working vehicle1is not limited to the tractor, and may be an agricultural machine (an agricultural vehicle) such as a combine harvester or a transplanter.

Hereinafter, a front side of an operator sitting on an operator seat10of the tractor (the working vehicle)1is referred to as the front, a rear side of the operator is referred to as the rear, a left side of the operator is referred to as the left, and a right side of the operator is referred to as the right. In addition, a horizontal direction that is a direction orthogonal to the front-rear direction of the working vehicle1will be described as a machine width direction.

As shown inFIG. 8, the tractor1includes a vehicle body3having a traveling device7, a prime mover4, a transmission device5, and a steering device11. The traveling device7is a device having a front wheel7F and a rear wheel7R. The front wheel7F may be a tire type or a crawler type. In addition, the rear wheel7R may also be a tire type or a crawler type. The prime mover4is an internal combustion engine such as a gasoline engine or a diesel engine, an electric motor, or the like. In this preferred embodiment, the prime mover4is a diesel engine.

The transmission device5is configured to switch the propulsive force of the traveling device7by shifting speeds and to switch between the forward traveling and the reverse traveling of the traveling device7. A cabin9is provided in the vehicle body3, and an operator seat10is provided in the cabin9.

An lifting device8is provided at the rear portion of the vehicle body3. The working device2can be attached to and detached from the lifting device8. In addition, the lifting device8is configured to lift the attached working device2. The working device2is a tiller device for tilling, a fertilizer sprayer device for spraying fertilizer, a pesticide sprayer device for spraying pesticides, a harvester device for harvesting, a mower device for mowing grass and the like, a tedder device for tedding grass and the like, a raking device for raking grass and the like, a baler device for baling grass and the like, or the like. In addition, inFIG. 8, an example in which attached the tiller device is attached as the working device2is shown.

As shown inFIG. 1, the transmission device5includes a main shaft (a propulsion shaft)5a, a shuttle portion5b, a main transmission portion5c, a sub-transmission portion5d, a PTO clutch device5e, and a front transmission portion5f. The propulsion shaft5ais rotatably supported by a housing case of the transmission device5, and the power from the crankshaft of the prime mover4is transmitted to the propulsion shaft5a.

The shuttle portion5bincludes a shuttle shaft5b1and a forward/reverse switching portion5b2. Power supplied from the propulsion shaft5ais transmitted to the shuttle shaft5b1. The forward/reverse switching portion5b2includes, for example, a hydraulic clutch or the like, and switches the revolving direction of the shuttle shaft5b1, that is, switches between the forward traveling and the backward traveling of the tractor1by engaging and disengaging the hydraulic clutch.

The main transmission portion5cis a continuously variable transmission mechanism that continuously changes the input power. The continuously variable transmission mechanism includes a hydraulic pump5c1, a hydraulic motor5c2, and a planetary gear mechanism5c3. The hydraulic pump5c1revolves with the power supplied from the output shaft5b3of the shuttle portion5b. The hydraulic pump5c1is, for example, a variable displacement pump including a swash plate12, and is configured to change the flow rate of the operation fluid outputted from the hydraulic pump5c1by changing the angle of the swash plate12(a swash plate angle). The hydraulic motor5c2is a motor configured to be revolved by the operation fluid outputted from the hydraulic pump5c1through a fluid tube circuit such as piping. The revolving speed of the hydraulic motor5c2can be changed by changing the swash plate angle of the hydraulic pump5c1or changing the power to be inputted to the hydraulic pump5c1.

The planetary gear mechanism5c3includes a plurality of gears and a power transmission shaft such as an input shaft and an output shaft, and includes an input shaft13to which the power of the hydraulic pump5c1is inputted and includes an input shaft14to which the power of the hydraulic motor5c2is inputted. The planetary gear mechanism5c3combines the power of the hydraulic pump5c1and the power of the hydraulic motor5c2, and then transmits the combined power to the output shaft15.

Thus, according to the main transmission portion5c, the power to be outputted to the sub transmission portion5dcan be changed by changing the swash plate angle of the swash plate12of the hydraulic pump5c1, the revolving speed of the prime mover4, and the like. The main transmission portion5cis defined by the continuously variable transmission mechanism. However, the main transmission portion5cmay be defined by a transmission mechanism with stepped gears.

The sub-transmission portion5dis a transmission mechanism including a plurality of stepped gears that change the power, and changes and outputs the power inputted from the output shaft15of the planetary gear mechanism5c3to the sub-transmission portion5d(changes the speed) by appropriately changing the connection (engagement) between the plurality of gears. The sub-transmission portion5dincludes an input shaft5d1, a first transmission clutch5d2, a second transmission clutch5d3, and an output shaft5d4. The input shaft5d1is a shaft to which the power of the output shaft15of the planetary gear mechanism5c3is inputted, and inputs the inputted power to the first transmission clutch5d2and the second transmission clutch5d3through the gears or the like. By respectively engaging or the disengaging the first transmission clutch5d2and the second transmission clutch5d3, the inputted power is changed and outputted to the output shaft5d4. The power outputted to the output shaft5d4is transmitted to the rear wheel differential device20R. The rear wheel differential device20R rotatably supports a rear axle21R to which the rear wheel7R is attached.

The PTO clutch device5eincludes, for example, a hydraulic clutch or the like, and is switched, by turning the hydraulic clutch on and off, between a state in which the power of the propulsion shaft5ais transmitted to the PTO propulsion shaft5e2(an engaging state) and a state in which the power of the propulsion shaft5ais not transmitted to the PTO propulsion shaft5e2(a disengaging state). The power of the PTO propulsion shaft5e2is transmitted to the PTO shaft16through the gears or the like.

The front transmission portion5fincludes a first front transmission clutch5f1and a second front transmission clutch5f2. The first front transmission clutch5f1and the second front transmission clutch5f2are capable of transmitting the power that is supplied from the sub-transmission portion5d, and, for example, the power of the output shaft5d4is transmitted through the gears and the transmission shaft. The power supplied from the first front transmission clutch5f1and the second front transmission clutch5f2can be transmitted to the front axle shaft21F through the front power transmission shaft. In particular, the front transmission shaft is connected to the front wheel differential device20F, and the front wheel differential device20F rotatably supports the front axle21F to which the front wheels7F are attached.

Each of the first front transmission clutch5f1and the second front transmission clutch5f2is defined by a hydraulic clutch or the like. A fluid tube is connected to the first front transmission clutch5f1, and the fluid tube is connected to a control valve23to which the operation fluid outputted from the hydraulic pump is supplied. The first front transmission clutch5f1switches between the engaging state and the disengaging state in accordance with the opening aperture of the control valve23. A fluid tube is connected to the second front transmission clutch5f2, and the control valve24is connected to the fluid tube. The second front transmission clutch5f2switches between the engaging state and the disengaging state in accordance with the opening aperture of the control valve24. Each of the control valve23and the control valve24is defined by, for example, a two-position switching valve with a solenoid valve, and are switched to the engaging state or to the disengaging state by magnetizing or demagnetizing the solenoid of the solenoid valve.

When the first front transmission clutch5f1is in the disengaging state and the second front transmission clutch5f2is in the engaging state, the power of the sub-transmission portion5dis transmitted to the front wheel7F through the second front transmission clutch5f2. In this manner, the four-wheel drive (4WD) to drive the front wheels and the rear wheels with the power is established, and the front wheels and the rear wheels have substantially the same revolving speed (the 4WD constant velocity state). On the other hand, when the first front transmission clutch5f1is in the engaging state and the second front transmission clutch5f2is in the disengaging state, the four-wheel drive is established, and the revolving speeds of the front wheels become faster than the revolving speeds of the rear wheels (4WD speed-increasing state). In addition, when the first front transmission clutch5f1and the second front transmission clutch5f2are in the engaging state, the power of the sub transmission portion5dis not supplied to the front wheels7F, and thus the four-wheel drive (2WD) to drive the rear wheels with the power is established.

As shown inFIG. 2, the lifting device8includes a lift arm8a, a lower link8b, a top link8c, a lift rod8d, and a lift cylinder8e. A front end portion of the lift arm8ais supported by a rear upper portion of a case (a transmission case) accommodating the transmission device5so as to be swingable upward or downward. The lift arm8ais swung (moved up and down) by driving the lift cylinder8e. The lift cylinder8eis defined by a hydraulic cylinder. The lift cylinder8eis connected to the hydraulic pump through the control valve34.

The front end portion of the lower link8bis supported on the lower rear portion of the transmission device5so as to be swingable upward or downward. The front end portion of the top link8cis supported by the rear portion of the transmission device5so as to be swingable upward or downward above the lower link8b. The lift rod8dconnects the lift arm8aand the lower link8b. The working device2is connected to the rear portion of the lower link8band to the rear portion of the top link8c. When the lift cylinder8eis driven (stretched and shortened), the lift arm8ais moved up and down, and the lower link8bconnected to the lift arm8aby the lift rod8dis moved up and down. In this manner, the working device2swings upward or downward (moves up and down) with the front portion of the lower link8bas a fulcrum.

As shown inFIG. 3, the PTO clutch device5eincludes a first rotor member151, a second rotor member152, and a pressing member153. The first rotor member151is fixed to the propulsion shaft5aand rotates with the revolving of the propulsion shaft5a. The second rotor member152transmits the power to the PTO shaft16, and is defined by, for example, a circular disk. The pressing member153is a piston configured to be moved by the pressure of the operation fluid between the engaging side on which the first rotor member151is pressed to the second rotor member152and the disengaging side on which the first rotor member151is disengaged from the second rotor member152. The pressing member153is movably provided in the housing154and moves to the pressing side (the engaging side) G1side against the biasing force of the spring155, such that the first rotor member151is pressed to the second rotating member, and the pressing member153moves to the releasing side (the disengaging side) G2side with the biasing force of the spring155, such that the first rotor member151is separated from the second rotating member. That is, when the pressing member153moved to the pressing side G1, the engaging state in which the power of the propulsion shaft5ais transmitted to the PTO propulsion shaft5e2is established, and when the pressing member153is moved to the disengaging side G2, the disengaging state in which the power of the propulsion shaft5ais not transmitted to the PTO propulsion shaft5e2.

The PTO clutch device5eincludes a PTO brake157. The PTO brake157is configured to reduce the revolving of the PTO shaft16when the pressing member153is positioned on the disengaging side G2. The PTO brake157includes a first contact member157aconfigured to move in accordance with the movement of the pressing member153, and includes a second contact member157bconfigured to be fixed to the housing154or the like. The first contact member157ais fixed to the pressing member153. When the pressing member153moves to the engaging side G1, the first contact member157amoves in a direction separating away from the second contact member157b, and when the pressing member153moves to the disengaging side G2, the first contact member157amoves toward the second contact member157b. The first contact member157aand the second contact member157binclude facing surfaces that face each other. The facing surface of the first contact member157aand the facing surface of the second contact member157bare pressed to each other when the pressing member153moves to the disengaging side G2, the braking is applied. The facing surface of the first contact member157aand the facing surface of the second contact member157bare separated from each other when the pressing member153moves to the engaging side G1, the braking is released.

A supply chamber158to supply the operation fluid is provided in the housing154, and the pressing member153is moved in the housing154by the pressure of the operation fluid supplied to the supply chamber158. A fluid tube160is connected to the supply chamber158, and a control valve161is connected to the fluid tube160. The control valve161is a valve configured to control the PTO clutch device5e, that is, to control the pressure of the operation fluid in the supply chamber158. And, the control valve161is, for example, a proportional solenoid valve configured to switch between a first position161A and a second position162B. The operation fluid from the hydraulic pump162is supplied to the control valve161. When the control valve161is set to the first position161A, the operation fluid is supplied to the supply chamber158, and thus the pressure in the supply chamber158is increased. When the control valve161is set to the second position161B, the operation fluid in the supply chamber158passes through the control valve161and is discharged to the discharge portion such as the operation fluid tank, so that the pressure in the supply chamber158is reduced.

In this manner, the PTO clutch device5eis capable of being switched between the engaging state and the disengaging state by switching the control valve161to either the first position161A or the second position161B. In particular, the revolving of the PTO shaft16can be stopped by the braking of the PTO brake157simultaneously when the PTO clutch device5eis set to the disengaging state.

As shown inFIG. 3, the tractor1includes a controller device40. The controller device40is configured to perform various controls of the tractor1, and, for example, performs the lifting control, the PTO control, and the like. In the lifting control, the controller device40magnetizes the solenoid of the control valve34to switch the control valve34to the lifting position when a command for the lifting is issued through operation of the lifting operation tool171. In this manner, the lift cylinder8eis stretched, and the rear end portion of the lift arm8a(the end portion on the working device2side) is lifted.

In the lifting control, when the lifting operation tool171is operated in a lowering direction (a lowering side), the controller device40magnetizes the solenoid of the control valve34to switch the control valve34to the lowering position. In this manner, the lift cylinder8eis shortened, and the rear end portion of the lift arm8a(the end portion on the working device2side) is lowered.

In addition, the controller device40stops the lifting operation of the lifting device8when the angle of the lift arm8areaches the position of the working device2, that is, reaches the upper limit (the upper limit value of height) set by the upper limit setting dial172under the state where the working device2is moved upward by the lifting device8.

In addition, a PTO switching member164is connected to the controller device40. The PTO switching member164includes a seesaw switch, a button switch, a slide switch, or the like, and is configured to be switched on and off. In the PTO control, when the PTO switching member164is switched on, the controller device40magnetizes the solenoid161C of the control valve161to switch the control valve161to the first position161A. Additionally in the PTO control, when the PTO switching member164is switched off, the controller device40demagnetizes the solenoid161C of the control valve161to switch the control valve161to the second position161B.

In addition, a rate setting portion165A is connected to the controller device40. The rate setting portion165A is configured to set the reducing rate of the pressure of the operation fluid when the control valve61is switched to the second position161B, that is, when the operation fluid in the supply chamber158of the PTO clutch device5eis discharged to the outside to reduce the pressure of the operation fluid applied to the supply chamber158(a working pressure). The rate setting portion165A is, for example, a rate setting switch with which the operator manually sets the reducing speed. The rate setting switch is a hardware switch, and is a volume switch (a turn switch) including a cylindrical knob165acapable of turning about the vertical axis165b. As shown inFIG. 4, when the knob165ais turned in one direction, the reducing rate to be set becomes small, and when turned in the other direction, the reducing rate to be set becomes large.

The controller device40controls the control valve61based on the reducing rate set by the rate setting portion165A. In particular, when the reducing rate set by the rate setting portion165A is high, the controller device40increases the speed (a switching speed) at which the control valve161is switched from the first position161A to the second position161B, thus increasing the reducing rate of the working pressure in the supply chamber158. In addition, when the reducing rate set by the rate setting portion165A is small, the controller device40slows the switching speed at which the control valve161is switched from the first position161A to the second position161B, so that the reducing rate of the working pressure in the supply chamber158is increased. As described above, the controller device40and the rate setting portion165A change the reducing rate of the working pressure in the supply chamber158to adjust the braking force of the PTO brake157per unit time. According to this configuration, since the inertial force of the PTO shaft16differs depending on the type of the working device2, the braking force of the PTO brake157that works at the same time when the PTO brake157is disengaged can be weakened by decreasing the reducing speed with the rate setting portion165A in the case where the inertial force is large. And, it is possible to prevent the burn-in due to the pressured contact between the first contact member157aand the second contact member157b, thus extending the life of the PTO brake157. On the other hand, when the inertial force is small, the braking force of the PTO brake157can be increased by increasing the reducing rate with the rate setting portion165A, and thus the PTO shaft16can be stopped quickly. That is, the driver can change the reducing rate while predicting the inertial force, simultaneously confirming the type and state of the working device2, and thus it is possible to quickly rotate the PTO shaft16while preventing the burn-in.

Second Preferred Embodiment

FIG. 5is a view showing a PTO clutch device and a controller device according to a second preferred embodiment of the present invention. In the second preferred embodiment, the description of the configurations same as those of the first preferred embodiment will be omitted.

As shown inFIG. 5, the controller device40includes a rate setting portion165B. The rate setting portion165B includes an electric/electronic circuit provided in the controller device40, a computer program stored in the controller device40, or the like.

The rate setting portion165B sets the reducing rate based on the revolving speed of the PTO shaft16when the pressing member153of the PTO clutch device5eis moved to the engaging side. In particular, the controller device40is connected to a revolving detector device169configured to detect the revolving speed of the PTO shaft16.

As shown inFIG. 6, when the PTO switching member164is switched on at the point P10under the state where the working device2and the PTO shaft16are connected to each other, the controller device40(the rate setting portion165B) reduces the electric current value A1after instantaneously increasing the current value A1to be outputted to the solenoid161C of the control valve161(a one-shot section T1), and then gradually increases the current value A1(a modulation section T2). In addition, the rate setting portion165B monitors the increasing tendency of the revolving speed of the PTO shaft16detected by the revolving detector device169in the modulation section T2in which the current value Al is gradually increased, that is, in the modulation section T2in which the current (the control signal) outputted to the control valve61is gradually increased by the controller device40(the rate setting portion165B). For example, the rate setting portion165B obtains, with the least square method or the like, the increasing rate (inclination) A2based on the revolving speeds of the plurality of PTO shafts16in the modulation section T2. When the increasing rate (inclination) A2is smaller than a predetermined reference rate (inclination) A3, the rate setting portion165B reduces the reducing rate, and when the increasing rate (inclination) A2is larger than the reference rate (inclination) A3, the rate setting portion165A increases the reducing rate. That is, under the state where the working device2is driven by the PTO shaft16, it can be assumed that the inertial force generated when stopping the working device2is large when the increasing speed A2is small, and that the inertial force generated when stopping the working device2is small when the increasing speed A2is large. As described above, the reducing rate can be easily set according to the inertial force estimated in driving the working device2.

In addition, the setting of the reducing rate with the rate setting portion165B may be performed in initially driving the working device2with the power of the PTO shaft16, for example, when the working is started, that is, when the working device2is connected to the lifting device8and the PTO shaft16is connected to the working device2. And, the setting of the reducing rate with the rate setting portion165B may be performed in reengaging the PTO clutch device5eafter the disengaging of the PTO clutch device5e. In addition, the rate setting portion165B sets the reducing rate when the lifting device8is in the ascending position, that is, when the lifting device65B is positioned at the lifting position, that is when the lifting instruction is issued by the lifting operation tool171. In addition, the rate setting portion165B may set the reducing rate when the lifting device8is positioned at the lowered position.

The sensitivity (frequency) for setting the reducing rate with the rate setting portion165B may be arbitrarily changed. For example, as shown inFIG. 7, when a predetermined operation is performed on the display device45, the display device45displays the setting screen M17. The setting screen M17displays a sensitivity setting tool410. The sensitivity setting tool410includes a scale portion410aand an index portion410b. The scale portion410ais a portion for displaying the sensitivity (the frequency), the one side has high sensitivity and the other side has low sensitivity.

The index portion410bis movable with respect to the scale portion410a, and is a portion for selecting the sensitivity. According to the sensitivity setting tool410, when the sensitivity is increased, the setting frequency of the reducing rate by the rate setting portion165B is increased in reengaging the PTO clutch device5eafter disengaging once (when re-engaging), and when the sensitivity is decreased, the setting frequency is decreased in reengaging.

The working vehicle1includes: the PTO shaft16to transmit, to the working device2, the power of the propulsion shaft5athrough which the power of the prime mover4is transmitted; the PTO clutch device5eincluding: the first rotor member151to be rotated by the power of the propulsion shaft5a; the second rotor member152to transmit the power to the PTO shaft16; the pressing member153to be moved by the pressure of the operation fluid between the engaging side on which the first rotor member151is engaged with the second rotor member152and the disengaging side on which the first rotor member151is disengaged from the second rotor member152; and the PTO brake157to brake the PTO shaft16when the pressing member153is positioned on the disengaging side; the control valve (a pressure control valve)161to control the pressure of the operation fluid to be applied to the PTO clutch device5e; the rate-setting portions165A and165B to set, with the control valve161, a reducing rate at which the pressure of the operation fluid is reduced; and the controller device40to control the control valve161based on the reducing rate set by the rate-setting portions165A and165B. According to this configuration, it is possible to change the reducing rate with the rate setting portions165A and165B according to the working device2generating a large inertial force during operation and the working device2generating a small inertial force during operation. Thus, the braking of the PTO shaft can be appropriately performed depending on the type of the working device2.

The rate-setting portion is the rate-setting switch165A allowing the operator to manually set the reducing rate. According to this configuration, the reducing rate can be controlled while judging the situation where the operator operates the working device2, for example, the magnitude of the load or the inertial force.

The working vehicle1includes the revolving detector device169to detect a revolving speed of the PTO shaft16. The rate-setting portion165B sets the reducing rate based on the revolving speed of the PTO shaft16, the revolving speed being detected by the revolving detector device169when the pressing member153is moved to the engaging side. According to this configuration, the reducing rate can be set in accordance with the transition of the revolving speed of the PTO shaft16, the transition being caused when the working device2is connected to the vehicle body3to drive the PTO shaft16.

The rate-setting portion165sets the reducing rate based on a relation between the revolving speed of the PTO shaft16and a control signal outputted to the control valve161, the revolving speed and the control signal being provided at a timing when the pressing member153is moved to the engaging side. According to this configuration, the reducing rate can be set in accordance with the transition of the revolving speed of the PTO shaft16, the transition being caused when the control valve161is operated, for example, when the first rotor member151and the second rotor member152are engaged by the pressing member153. For example, in the case where the working is performed by the working device2, the reducing rate can be set depending on the increasing transition of the revolving speed of the PTO shaft16, the increasing transition being caused when the working device2is initially driven by the PTO shaft16.

The rate-setting portion165B lowers the reducing rate when the increasing rate of the revolving speed of the PTO shaft16is smaller than the reference rate preliminarily determined and raises the reducing rate when the increasing rate is larger than the reference rate, with respect to the electric current value outputted as the control signal to the control valve161. For example, it can be determined that the inertial force is large when the increasing rate of the revolving speed of the PTO shaft16is smaller than the reference speed, the increasing rate being caused when the working device2is initially driven by the PTO shaft16, and determined that the inertial force is small when the increasing rate of the revolving speed of the PTO shaft16is larger than the reference speed. And, when the inertial force is large, it is possible to reduce or prevent wear of the PTO brake157or the like by reducing the reducing rate.

The rate-setting portion165B includes the display device45configured to allow to set the sensitivity of the reducing rate. According to this configuration, the reducing rate can be set in accordance with various types of the working devices2by changing the frequency of setting the reducing rate, that is, by changing the sensitivity in automatically setting the reducing rate.