JP2007285313A - Clutch control device for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clutch control device for a work vehicle capable of smoothly engaging clutches having respective operating characteristics and frictionally engaged by accurate clutch control in which their engagement timings are matched with each other. <P>SOLUTION: This clutch control device for a work vehicle comprises a control part for controlling the drive pressure of the clutch selected from two forward and backward clutches at a forward/backward selection part for transmission control by an indication pressure according to the clutch pedal position. A drive pressure from the disengagement position to the engagement position of the clutch caused by the engagement operation of the clutch pedal is so set that, in a time range T1 before the engagement position, it is equivalent to a first pressure P1 and, in a subsequent time range T2 up to the engagement position, it is equivalent to a second pressure P2 smaller than the first pressure based on reference initial times Ts starting at the disengagement position to the engagement position obtained by the control part from the drive pressure when the clutch is engaged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work vehicle clutch control device for performing transmission control of travel power via a travel clutch of a work vehicle.

As shown in Patent Document 1, there is known a work vehicle including a speed change transmission unit in which a traveling clutch or the like by frictional connection is incorporated. The speed change transmission portion of the work vehicle includes a forward / reverse switching clutch and a transmission gear so as to change the forward / reverse movement and the gear ratio, and connects / disconnects driving power using the forward / reverse switching clutch as a travel clutch.
These clutches can be controlled with a certain accuracy by operating characteristics according to the design specifications of the clutch and drive control system.

However, due to variations in operation characteristics due to individual clutch components, assembly accuracy, and hydraulic drive system accuracy, unstable connection operations may be caused by variations in the connection position corresponding to the piston stroke in the clutch connection stroke in particular. As a result, an excessive load fluctuation of the transmission system is caused and the smoothness of the start of the aircraft is impaired.
JP-A-6-11023

  The problem to be solved by the present invention is to provide a clutch control device for a work vehicle that enables a smooth connection operation by high-precision clutch control that matches the connection timing of a clutch by friction connection having individual operation characteristics. There is.

  According to the first aspect of the present invention, there is provided a control unit that controls the driving pressure of the clutch on the selected side with the command pressure corresponding to the clutch pedal position for the forward and reverse clutches of the forward / reverse switching unit that performs transmission control. In the work vehicle clutch control device provided, the driving pressure from the clutch disengagement position to the engagement position when the clutch pedal is engaged is obtained from the drive pressure obtained when the clutch is engaged by the controller. Based on the respective reference initial times (Ts) from the position to the entry position, the time range (T1) before the entry position is set as a hydraulic drive corresponding to the first pressure (P1), and the subsequent entry position is reached. It is characterized by hydraulic control in which the time range (T2) is hydraulically driven corresponding to the second pressure (P2) smaller than the first pressure.

  The two forward and reverse clutches of the forward / reverse switching portion are driven at the selected pressure corresponding to the clutch pedal position to transmit power, and the motive power is transmitted from the clutch disengaged position by the clutch pedal engaging operation. In the stroke to reach, the reference initial time (Ts) from the cut position to the entry position obtained by the respective clutch operations is driven to the position just before the entry position with a relatively large first pressure, and then the relatively small first time is reached. Driven by the pressure of 2 to reach the entry position.

  According to a second aspect of the present invention, there is provided a work vehicle including a control unit that controls a driving pressure on a side selected by switching of a forward / reverse switching lever for two clutches of forward / reverse switching of the forward / reverse switching unit that performs transmission control. In the clutch control apparatus for driving, the driving pressure from the clutch disengagement position accompanying the switching operation of the forward / reverse switching lever extends from the disengagement position obtained from the drive pressure when the two clutches are operated by the control unit to the engagement position. Based on the respective reference initial times (Ts), the time range up to the entry position is set as the first pressure, the subsequent time range extending to the entry position is set as the second pressure smaller than the first pressure, In addition, the range after the entry position is based on a pressure characteristic that gradually increases the pressure from the second pressure.

  The two forward and reverse clutches of the forward / reverse switching portion are driven by the side selected by switching the forward / reverse switching lever to transmit power, and in the process from the clutch disengaged position to the engaged position by the switching operation, Driven by a relatively large first pressure to the position just before the engaged position by a reference initial time (Ts) from the cut position to the engaged position obtained by each clutch operation, and then driven by a relatively small second pressure. Then, it reaches the entry position, and thereafter the pressure is gradually increased from that pressure.

  In each of the first and second aspects, the respective configurations enable high-precision piston stroke control based on the reference initial time (Ts) measured by the clutch operation from the disengaged position to the engaged position. The clutch on the selected side can be driven quickly with high pressure until just before its engagement position, and the engagement position is reached with low pressure, so that the transmission power can be maintained while ensuring responsiveness without causing variations in individual clutch characteristics. Thus, a smooth clutch operation that suppresses sudden changes in the engine speed is possible, and excessive fluctuations in the transmission system load are suppressed, and smooth aircraft start-up control is possible.

Embodiments specifically configured based on the above technical idea will be described below with reference to the drawings.
Agricultural tractor 1 as an example of a work vehicle to which the present invention is applied is shown in a bonnet at the front part of a machine body having front wheels 2, 2 and rear wheels 3, 3 as shown in FIG. The engine 4 is mounted, the rotational power of the engine 4 is transmitted to the transmission gear transmission 5a in the transmission case 5, and the power appropriately decelerated by the transmission transmission gear 5a is transmitted to the front wheels 2, 2 and the rear wheels 3, 3. While transmitting, it is comprised so that it may output to the working machine 6a via the PTO shaft 6 of the rear part.
Further, for operation by an operator, a pilot seat 7 is provided at the upper part of the mission case 5 to constitute an operation unit, a forward / reverse switching lever 13 for forward / reverse switching near the steering handle 11, a clutch pedal 15 and the like at the base portion. It is arranged and configured to be capable of automatic shifting by the control unit C.

  The transmission transmission unit is a mechanism unit that controls the traveling power and the work machine power. As shown in the transmission system development diagram of FIG. 1, the traveling system includes a forward / reverse switching unit 21 that receives power from the engine 4, and a four-speed transmission mechanism. 22, a high speed transmission mechanism 23 and a sub transmission section 24 transmit to the rear wheels 3 and 3 through the differential mechanism 3 d, and a front wheel transmission clutch (two-wheel drive / four-wheel drive switching clutch) 25 is provided. Power is transmitted to the front wheels 2 and 2 via the differential mechanism 2d so that the switching control is possible. The work machine system includes a PTO clutch 26, a PTO transmission part 27, and the like that branch work power from the engine 4 and control transmission to the rear PTO shaft 6.

  The forward / reverse switching portion 21 includes a double-coupled clutch in which two forward / reverse clutches 21a and 21b are connected, and the forward and reverse gear trains are moved forward and backward from the neutral position N of the forward / reverse switching lever. It is configured to be selectable in accordance with a command from the control unit by an R selection operation. Further, the transmission of engine power is adjusted by the clutch on the selection side according to the clutch pedal operation.

  The four-speed transmission mechanism 22 includes two double clutches, ie, first-speed and third-speed switching clutches 22a and 22c and second-speed and fourth-speed switching clutches 22b and 22d, and the four clutches 22a to 22d start from the first speed. A gear train up to the fourth speed can be selected. The high / low speed transmission mechanism 23 includes a double clutch of two Lo / Hi clutches 23a and 23b so that a low-speed and high-speed gear train can be selected. The four-speed transmission mechanism 22 and the high-low speed transmission mechanism 23 are connected in series to form a main transmission unit that can be switched within an eight-speed transmission range in response to a command from the control unit using an accelerator pedal or an acceleration / deceleration button.

  The sub-transmission unit 24 is configured by a gear mechanism that can switch a gear ratio of high, middle, low and third speeds by a shift lever 18 operated by an operator. Three lever positions (shift positions) “H”, “M”, and “L” are set corresponding to the high, medium, and low speed ratios, and these lever positions are set as speed bands for work traveling, and neutral without power transmission. The speed band is selected by operating the speed change lever 18 from the position “N”.

  The gear ratios of all 24 speeds can be selected by the combination of the four-speed transmission mechanism 22, the high / low speed transmission mechanism 23, and the auxiliary transmission unit 24. The determination of the combination is selected by the control unit according to the condition through the shift operation of the shift lever 18, the accelerator operation, and the like, so that the vehicle body traveling speed can be adjusted.

  As shown in FIG. 2, the hydraulic control system of each device including the speed change transmission unit 5a has two clutches 21a and 21b of the forward / reverse switching unit 21 and a four-speed transmission mechanism 22 by a hydraulic pump 31p. The hydraulic oil is supplied to the four clutches 22a to 22d, the two clutches 23a and 23b of the high and low speed transmission mechanism 23, the PTO clutch 26, and other hydraulic equipment. The hydraulic oil supply amount distributes the flow rate per unit time of the clutches 21a and 21b of the forward / reverse switching unit 21 larger than that of the other clutches. With this flow rate distribution, it is possible to secure responsiveness to the operator's pedal operation and the like while suppressing the pump capacity.

  Regarding the operation control of these clutches, the switching valve 32 is provided in the two clutches 21a and 21b of the forward “F” and the reverse “R” of the forward / reverse switching unit 21 and the pressure control is performed using the proportional control valve 33a as a pilot. A relief valve 33b is provided, and a shuttle valve 34 with a pressure sensor 34p for detecting the hydraulic pressure on the operating side is provided between the clutches 21a and 21b.

  The operation control of the four-speed transmission mechanism 22 is performed by providing a switching valve 35a in the first-speed / third-speed switching clutches 22a, 22c, and providing a proportional control valve 36a for boosting control thereof. , 22c is provided with a shuttle valve 37a with a pressure sensor 37p, and similarly, a switching valve 35b, a proportional control valve 36b, and a shuttle valve 37b with a pressure sensor 37q are provided in the clutches 22b and 22d for switching between the second speed and the fourth speed.

  The operation control of the high and low speed transmission mechanism 23 is performed by providing switching valves 38a and 38b and pressure sensors 38p and 38q respectively in two clutches 23a and 23b of a low speed “Lo” and a high speed “Hi”. The operation control is performed via a proportional control valve 39a, a switching valve 39b, and a pressure sensor 39p.

Next, the control configuration of the hydraulic control system will be described.
As shown in FIG. 3, the control configuration of the hydraulic control system includes a clutch pedal depression detection switch 42p as a momentary operation unit on the input side of the control unit 41, a stroke sensor 42s for detecting the depression stroke, and an accelerator depression stroke. Operation devices such as an accelerator sensor 43 to detect, a sub-shift position sensor 24p, a forward / reverse switching lever 21p, a check switch 44 and the like are connected to input an operation signal, an oil temperature sensor 32t, a forward / reverse clutch pressure sensor 34p, and a first speed. Sensor signals from device operation sensors such as the pressure sensor 37p for the third speed clutch, the pressure sensor 37q for the second speed / fourth speed clutch, and the clutch sensors 38p, 38q for the high / low speed transmission mechanism 23 are input.

  On the output side of the control unit 41, a forward / reverse switching valve 32, a proportional control valve 33a for boost control thereof, a first speed / third speed switching valve 35a, a proportional control valve 36a for boost control thereof, and a second speed / fourth speed switching valve 35b. And a drive solenoid of the proportional control valve 36b for boosting control thereof are connected to each other so that drive control is possible.

Next, the adjustment mode control will be described.
The adjustment mode is a mode for performing initial clutch adjustment for setting the engagement position of each clutch necessary for clutch operation control. This clutch initial adjustment is processed by the control unit 41 in accordance with a check mode signal for instructing application of the adjustment mode, and the piston stroke of the clutch of the work vehicle including the traveling clutch is estimated by measuring its stroke operation.

  As shown in the pressure change characteristic diagram of FIG. 4, the control of the boost valve outputs a drive current corresponding to the maximum clutch pressure at the clutch disengaged position until a predetermined judgment pressure Ps set smaller than the maximum pressure is reached. Is measured as a reference initial time Ts.

  Based on the reference initial time Ts thus measured, the piston stroke of the clutch is estimated by an actual stroke operation. Accordingly, each piston stroke is estimated for each clutch, and based on this piston stroke, a smooth connection operation by high-precision clutch control in which the connection timing is matched becomes possible.

Next, clutch control based on clutch pedal operation will be described for the forward and reverse clutches 21a and 21b of the forward / reverse switching unit 21.
FIG. 5 is a characteristic diagram of the main part of the clutch control. As the clutch control based on the clutch pedal operation, an initial initial output is performed in correspondence with the engagement operation by the clutch pedal. This initial initial output exceeds the pressure indicated at the pedal position at a time T1 shorter than the specified pressure arrival time on the basis of the specified pressure arrival time (reference initial time Ts) on the forward side and the reverse side measured in the adjustment mode. The hydraulic control is performed by driving with a large current corresponding to the first pressure and then driving the control valve for a predetermined time T2 with a predetermined low driving current corresponding to the second pressure. This valve drive is performed only once after the clutch meet so that the pressure is once dropped just before the meet during actual running.

  By the above valve drive, the clutch piston is moved as close as possible to the vicinity of the meet point by hydraulic drive corresponding to a relatively large first pressure, and at the time of meet, it is surely met at low pressure by the hydraulic drive equivalent to the second pressure. Can do. Low pressure when pressure control is applied with pressure feedback because the drive current is reduced at a position corresponding to the front of the meet point based on the piston stroke equivalent time (measured value) considering individual variations in the adjustment mode. Can be controlled from.

  The hydraulic circuit of the two forward and reverse clutches 21a and 21b constitutes a hydraulic circuit so as to control the operation of at least two solenoid valves to the disconnection side in the disconnection operation. The solenoid valve is connected in series on the upper side, one is shut off from oil supply, and the other is switched to the oil drain side. In this way, the power can be reliably cut off by the circuit configuration having two or more cut-side actuators.

Regarding the clutch pedal position determination for detecting the clutch pedal operation, as shown in a sensor development view in FIG. 6, each position is developed corresponding to the clutch operation.
That is, each position of H1-H4 is determined along the process of returning the clutch pedal from the depression position H0. H1 is an ON → OFF position of the clutch pedal switch 42p or a corresponding clutch pedal sensor position, H2 is a clutch pedal sensor low pressure holding position, H3 is a clutch pedal sensor pressure maximum indicating position, and H4 is a clutch pedal sensor opening position.

  Specific output control according to clutch pedal operation based on this sensor development includes basic operation during clutch pedal disengagement determination, operation during clutch pedal disengagement → on disengagement, pressure check operation during initial driving of clutch pedal, clutch pedal ingress side There are operations at the time of judgment.

The clutch pedal turn-off (depression) position determination (off determination) is based on the establishment of either the clutch pedal switch = on or the clutch pedal sensor <H1. Based on this OFF determination, the operation when the clutch pedal is disengaged is performed.
Further, the clutch pedal on-side determination (on determination) is based on the establishment of both conditions of clutch pedal switch = off and clutch pedal sensor ≧ H1. By this ON determination, an operation corresponding to the pedal position is performed.

  More specifically, first, the basic operation during the clutch pedal disengagement determination is performed by changing the hydraulic circuit diagram of the main part to the clutch pedal valve 33c output on, the proportional pressure control valve 33a off and the switching valve 32 off as shown in FIG. The valves 38a and 38b are turned off, the double biting control and the clutch protection control of the main transmission switching unit are performed.

  Next, the clutch pedal turn-off / turn-on determination operation is performed as a switch-on / off determination condition in which the clutch pedal switch is turned on → off and a pedal sensor ≧ H1 is determined to output a pedal initial initial output.

  The initial initial operation output of the pedal is that when the forward / reverse operation lever F is on, the proportional pressure control valve with a small current that can secure the total flow rate for the time of F clutch piston ST reference value × 0.8 corresponding to a predetermined high pressure P1. After this time elapses, a specified time, for example, 0.1 second is driven with a specified low pressure P2 equivalent current. When the forward / reverse operation lever R in the reverse direction is ON, the R clutch is similarly driven according to the clutch piston ST reference value.

  Further, the valve on the main transmission side or the like at the time of clutch pedal on / off determination is based on the clutch pedal off to on / off determination, and the main transmission unit sets the target shift position to a high pressure such as 20 kgf / cm 2 and other shift positions off. The high / low switching unit turns on the target shift position.

  The “shorter time T1” based on the specified pressure arrival time is a short time of a constant ratio (for example, 0.8) of 1 or less with respect to the reference time (reference initial time Ts) of each clutch.

The specified pressure arrival time obtained by measurement varies depending on the amount of leaks and piston stroke variations that vary from clutch to clutch. Can be changed to current. Therefore, it is less likely that connection shock will occur due to high pressure applied by a large current during meet.
Further, the same effect as above can be obtained by setting the “shorter time” to a short time obtained by subtracting a predetermined time from the specified pressure arrival time.

  Regarding the check operation during the initial initial output, if the pressure sensor detects the occurrence of pressure above the specified pressure while driving at a current larger than the current equivalent to the pressure indicated at the pedal position during the initial initial output, immediately increase the Stop driving with current and always drive with a specified low drive current for a specified time.

  That is, when a pressure higher than a specified pressure is generated during driving with the clutch initial initial current, the initial initial current output is stopped, and driving corresponding to a low pressure is performed at a specified time after the initial time, for example, 1 kgf / square cm for 0.1 second. It drives with the pressure according to the pedal position after the driving of pressure. The specified pressure is set to a different value depending on the oil temperature.

  If the pedal is repeatedly turned on and off quickly with regard to the above clutch pedal operation, the clutch piston does not return to the initial position, and if the time corresponding to the measurement reference value is driven with a large current as it is, a high pressure at the time of meet And a connection shock is generated (half-clutch operation is not possible). However, by the check drive, even in such a case, the pressure can be instantaneously changed to a low pressure, so that the operability can be improved.

In addition, in the above, the “specified pressure” in the “pressure higher than the specified pressure” generated during driving with a larger current is higher as the oil temperature is higher according to the viscosity characteristics of the oil being used due to the oil temperature being measured. The judgment pressure is set high.
The viscosity of oil differs depending on the oil temperature, and if the pressure at the measurement site is determined by the same pressure due to the pressure loss due to the oil passage etc., a low pressure cannot be set (incorrect determination). Therefore, it is possible to make an appropriate determination by changing the detected pressure according to the oil temperature.

Next, with regard to the on-side determination operation, the clutch is initially initialized when the clutch pedal is turned off and then on, and the clutch pedal itself has a drive current that generates a specified pressure according to the operation position according to the pedal position. In the time zone during which the initial initial output operation is being performed, the initial initial output operation is preferentially output once regardless of the pedal position.
By configuring in this way, the initial feeling of the clutch can be connected with the same feeling regardless of how the pedal is operated.

  In this case, the specified pressure line corresponding to the pedal position is constituted by a line that differs depending on the main / sub shift position, that is, an inclined line in which the pressure in the latter half of the H2-H3 position is increased as the shift speed is faster. For example, the command pressure at the H3 position is set to a current equivalent to 5.5 kgf / sq.cm when the speed is medium or lower and the sub-shift is neutral, and a current equivalent to 10 kgf / sq.cm when the speed is medium and higher than the eighth speed. However, priority is given to the output during the initial pedal operation and the pressure check operation.

  With this configuration, the reduction ratio varies depending on the shift position, so even if the same pressure is applied, the driving force for the rear wheels differs, so the pedal stroke can be used effectively by changing the pressure according to the shift position. Thus, handling with an expanded half-clutch area is possible.

  For abnormality notification, the pressure of the forward / reverse switching clutch is controlled by the pressure according to the clutch pedal operation position, and the clutch pedal sensor includes a region in which the clutch is completely disengaged when the pedal is depressed and a control region such as a half clutch at the intermediate pressure. There are three areas, the area where high pressure is maintained with the pedal released, and when the clutch pedal sensor is continuously detecting the intermediate pressure area for more than the specified time during operation, an abnormality is displayed on the monitor. Configure as follows.

  That is, when the clutch pedal sensor is continuously positioned at the intermediate pressure designated position, the clutch pedal switch is turned off, and the condition that the clutch pedal sensor value is less than the maximum indicated position continues for 10 seconds or longer. A message such as “Sensor Abnormal” or “Have you put your foot on the clutch pedal” is displayed.

  With the above configuration, if the clutch is kept on the clutch pedal and the half-clutch state is continued due to poor adjustment or the like, the clutch will be worn early if left unattended. Can be solved. In this case, an alarm may be given as the clutch being disconnected.

  In addition, by configuring the above three areas so that the state other than the open position can be confirmed on the monitor, the pedal operation position can be easily determined, so the margin of the open position / cut position can be confirmed, and adjustment errors can be made. In addition, when there is a defective part of the opening position stopper, it can be prevented that the opening side is shipped without a margin. If displayed on the monitor of the meter panel, it can be confirmed at the user stage and problems can be prevented. In the case of a mechanically mechanically coupled clutch configuration, this can be confirmed by looking at the play of the pedal, but the same handling is possible for a system that does not mechanically interlock the clutch pedal and the clutch itself.

Next, clutch control based on the forward / reverse switching lever operation will be described.
When controlling the pressure of the two forward and reverse clutches 21a and 21b of the forward / reverse switching unit 21 in conjunction with the forward / reverse switching lever operation, release the foot from the clutch pedal and move the forward / reverse switching lever in the neutral position. The initial initial output is performed at the timing when the forward / reverse switching lever is switched to forward (reverse) from the stopped state.

  This initial initial output is driven with a higher current at a time T1 shorter than the specified pressure arrival time based on the specified pressure arrival time (reference initial time Ts) on the forward side and the reverse side measured in the adjustment mode, and thereafter A current lower than the initial current is supplied, and the current is gradually increased to boost the voltage.

  By the valve drive, the forward / reverse switching lever can be started by gradually connecting the clutch only by the forward F (reverse R) switching operation from the neutral N. At this time, the clutch piston can be moved as quickly as possible to the vicinity of the meet point, and at the time of meet, it can be reliably met at a low pressure. Low pressure when pressure control is applied with pressure feedback because the drive current drops at a position corresponding to the front of the meet point based on the piston stroke equivalent time (measured value) considering individual variations in the adjustment mode Can be controlled from.

  The control output by the forward / reverse switching lever will be described in detail. The basic operations during the neutral determination include the clutch pedal valve 33c output on, the proportional pressure control valve 33a off, and the forward / backward side of the switching valve 32 off. The high / low switching valves 38a and 38b are turned off, the double engagement control and the clutch protection control of the main transmission switching unit are performed.

  Next, in forward operation by the forward / reverse switching lever, the clutch pedal valve 33c output is turned off, the proportional pressure control valve 33a is turned on (controlled by a pressure increasing pattern according to the shift position), the forward side of the switching valve 32 is turned on, The shift target position side of 38a, 38b is turned on, the shift target position side of the main shift switching unit is turned on at, for example, 20 kgf / square cm, and the other shift positions are turned off. The reverse operation in the reverse direction is similarly performed on the reverse side. The output delay at the time of forward / reverse switching is set to 0 msec.

  As shown in FIG. 8, the pressure control when operating the forward / reverse switching lever is configured in two stages, initial output T1 and boost output T3, and the pressure increase control is performed after the main transmission unit completes shifting to the shift target position. Start. When the main shift is not in the target position at the timing when the forward / reverse switching lever is switched from OFF to ON, the pressure increase control is started after entering the target position.

  The initial output T1 is performed at the timing when the forward / reverse switching lever is operated from N → F or N → R. When the forward / reverse switching lever F is ON, for example, the proportional valve is driven with a current equivalent to F clutch piston ST × 0.8 (msec), 5 kgf / square cm. When the reverse direction forward / reverse switching lever R = on, the same operation is performed on the reverse side.

  The boosting pattern has a plurality of patterns according to the shift position, and a switch for changing the boosting sensitivity is provided on the operation panel unit so as to change the boosting pattern. The change method is to configure the same initial initial output and boost pattern output for each shift position, and provide a time to maintain a constant pressure during the transition from initial initial output to boost pattern output by switching the switch. Change the sensitivity.

  Specifically, as shown in FIG. 9 for the pressure diagram, the boost output sets a pattern according to the shift position, and when the shift sensitivity switch is on, the period from the end of the initial output to the start of the boost output. The aircraft is started by boosting the driving output corresponding to the specified pressure P4 at the specified time T4, for example, by applying a driving output of 100 msec at a current equivalent to 0.5 kgf / square cm.

  In general, when starting the aircraft, the pressure at which the aircraft starts to move is different depending on the state of the vehicle even if the pressure pattern is constant, and power is transmitted from a low pressure in a light state where the work machine is not worn, and the point becomes slightly higher when it becomes heavy Therefore, by adopting the above configuration, the necessary pressure increase pressure pattern remains unchanged for each shift position, and only the low pressure part is different. It can be changed with a simple configuration.

  In the above case, the “shorter time T1” determined based on the specified pressure arrival time is a constant ratio (for example, 0.8) of 1 or less with respect to the reference time (reference initial time Ts) of each clutch. Short time.

Such a fixed ratio setting is that the specified pressure arrival time obtained by measurement differs depending on the amount of leakage and piston stroke variations that differ from clutch to clutch. It can be changed from a large current to a small current at an equivalent position. Therefore, it is less likely that connection shock will occur due to high pressure applied by a large current during meet.
Further, the same effect as above can be obtained by setting the “shorter time” to a short time obtained by subtracting a predetermined time from the specified pressure arrival time.

  Explaining the checking operation to cope with abnormalities in the clutch control described above, when the pressure sensor detects the occurrence of pressure above the specified pressure during the initial initial output that is driven with a large initial current, the output by the large current due to the initial current is immediately output. It is configured to stop and shift to the boost pattern.

  If the lever operation is repeated rapidly with respect to the above-mentioned forward / reverse switching lever operation, the clutch piston does not return to the initial position, and if the time corresponding to the measurement reference value is driven with a large current as it is, a high pressure at the time of meet Although the connection shock occurs due to the connection, the operability can be improved because it is possible to instantaneously change the pressure to a low pressure even in such a case.

In addition, in the above, regarding the “specified pressure” in the “pressure higher than the specified pressure” generated during driving with a larger current, the determination pressure is changed depending on the oil temperature being measured, and the higher the oil temperature, the higher the determination pressure. Set higher.
The viscosity of the oil varies depending on the oil temperature. If the pressure at the measurement site is determined by the same pressure due to the pressure loss due to the oil passage or the like, a low pressure cannot be set (incorrect determination). Therefore, it is possible to make an appropriate determination by changing the detected pressure according to the oil temperature.

Next, the control at the time of a competitive operation of the clutch pedal and the forward / reverse switching lever will be described.
When the clutch pedal and the forward / reverse switching lever compete with each other, the priority is set as follows to control the pressure.
The clutch pedal and the forward / reverse switching lever have a priority when the pedal is operated first (a) and when the lever operation is advanced (b), as shown in FIG. The initial output by the operation is checked, and during the boost output by the lever, the low side of the clutch pedal command pressure and the boost output is preferentially driven.

Specifically, the case where the clutch pedal is operated during the pressure increasing operation by operating the forward / reverse switching lever is as follows.
For the change in pedal command pressure during the initial output due to lever operation, priority is given to the initial output of the lever operation, and after that output (including pressure check operation), it is driven by the lower pressure of clutch pedal command pressure and lever boost pressure To do. During lever boost output, the lever is driven at a lower pressure between the clutch pedal command pressure and the lever boost pressure. When there is a lever operation N → F or R during the clutch pedal intermediate pressure instruction, the control during the lever boost output is performed after the connection is started by lever boost control.

  With such a pressure control configuration, it is possible to obtain a good operability with less shock by giving priority to the algorithm that reliably operates to the meet point during initial output and then giving priority to the lower side.

It is a transmission system expansion | deployment figure of the transmission transmission part of a working vehicle. It is a hydraulic circuit diagram of a work vehicle. It is a control block diagram of a hydraulic control system. It is a pressure change characteristic view of a pressure | voltage rise valve. It is a clutch control principal part characteristic view. It is a sensor development view. It is a principal part hydraulic circuit diagram. It is a pressure diagram of the forward / reverse switching lever operation. It is a pressure diagram which shows sensitivity adjustment. It is a time chart of pedal operation precedence (a) and lever operation precedence (b). It is a side view of an agricultural tractor.

Explanation of symbols

2,3 Front and rear wheels 5a Transmission transmission unit 21 Forward / reverse switching unit 21a, 21b Clutch 21p Forward / reverse operation lever 22 Four speed transmission mechanism 23 High / low speed transmission mechanism 24 Sub transmission unit 32 Forward / reverse switching valve 33a Proportional pressure control valve 33b Relief valve 33c Clutch pedal valve 34p Forward / reverse pressure sensor 41 Control unit 42p Clutch pedal switch 42s Stroke sensor P1 High pressure P4 Specified pressure T1 Initial output T2 Specified time T3 Boosted output T4 Specified time Ts Standard initial time

Claims (2)

A clutch control device for a work vehicle having a control unit for controlling the driving pressure of the selected side clutch with the command pressure corresponding to the clutch pedal position for the forward and reverse clutches of the forward / reverse switching unit for performing transmission control In
The driving pressures from the clutch disengagement position to the engagement position in accordance with the clutch pedal engagement operation are the respective reference initials from the disengagement position to the engagement position obtained from the drive pressure during the clutch engagement operation by the control unit. Based on the time (Ts), the time range (T1) up to the position before the entry position is hydraulically driven corresponding to the first pressure (P1), and the time range (T2) extending to the entry position following this is the first range. A work vehicle clutch control device characterized by hydraulic control for hydraulic drive corresponding to a second pressure (P2) smaller than the pressure. In a work vehicle clutch control device including a control unit that controls a driving pressure of a clutch on a side selected by switching of a forward / reverse switching lever with respect to two clutches of forward and backward movement of a forward / reverse switching unit that performs transmission control,
The drive pressure from the clutch disengagement position accompanying the switching operation of the forward / reverse switching lever is the respective reference initial time from the disengagement position to the engagement position obtained from the drive pressure during the clutch engagement operation by the control unit. Based on (Ts), the time range (T1) before the entry position is hydraulically driven corresponding to the first pressure (P1), and the subsequent time range (T2) extending to the entry position is the first pressure. A clutch control device for a working vehicle characterized by hydraulic control corresponding to a smaller second pressure (P2) and a hydraulic control for gradually increasing the range after the entry position from the second pressure (P2). .

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