JP4744944B2 - Hydraulic transmission mechanism for traveling vehicles - Google Patents

Description

  The present invention relates to a hydraulic transmission mechanism for a traveling vehicle such as a tractor.

The hydraulic pressure of a traveling vehicle that automatically changes the traveling speed by automatically switching on and off of the hydraulic clutch and shifting operation of the gear transmission by operating the hydraulic cylinder by switching the electromagnetic valve for shifting based on the conventional shift command. A transmission mechanism is known (see, for example, Patent Document 1).
Japanese Patent No. 35733641

  The hydraulic transmission mechanism is switched to a hydraulic oil discharge state when the pilot pressure decreases below a predetermined pressure, and conversely, by a switching valve configured to switch to a hydraulic oil supply state when the pilot pressure rises above a predetermined pressure. The on / off of the hydraulic clutch is controlled.

  The pilot pressure is linked to the first on-off valve linked to the first hydraulic cylinder, the second on-off valve linked to the second hydraulic cylinder, the third on-off valve linked to the third hydraulic cylinder, and the fourth hydraulic cylinder. It changes based on the action | operation of the 5th on-off valve linked with the 4th on-off valve and the 1st switching lever which were made.

  For this reason, there is a large delay from when the shifting operation is performed until the hydraulic clutch is disengaged, and there is a case where the gear clutch is initially switched while the hydraulic clutch remains engaged. In this case, there is a drawback that an excessive load is temporarily applied to the gear switching mechanism, and the gear switching may not be performed smoothly.

The hydraulic transmission mechanism for a traveling vehicle according to the present invention for solving the above-described problems is a hydraulic cylinder that switches on and off of the hydraulic clutch 1 and switches the electromagnetic valves 41, 42, 43, 44, and 46 for shifting based on a shift command. In the hydraulic transmission mechanism of a traveling vehicle that automatically changes the traveling speed by operating the gear-type transmissions 3 and 6 by operating the gears 37, 38, and 39, the hydraulic transmission mechanism is based on a shift command. The switching valve 56 of the hydraulic clutch 1 is switched by the electromagnetic proportional pressure control valve 54, the hydraulic clutch 1 is disengaged and the shift operation of the gear transmissions 3 and 6 is completed, and the electromagnetic proportional pressure control valve 54 is turned on. controlling a control unit 50 for actuating enters the hydraulic clutch 1, during shifting operation of the gear type transmission 3, 6 and check oil passage LP through which oil drain, the hydraulic clutch 1 A clutch control oil passage LC that controls cutting-off is provided, and the clutch control oil passage LC and the check oil passage LP are allowed to flow only in the direction from the clutch control oil passage LC to the check oil passage LP. The first feature is that the valve 55 is connected .

Secondly, when the hydraulic clutch 1 is in the disengaged state, the check valve 55 is of a type that incorporates a spring so as to apply an initial pressure to the clutch control oil passage LC that reaches the switching valve 56 of the hydraulic clutch 1. .

  According to the structure of the present invention configured as described above, the hydraulic clutch is switched to the disconnected state with good response because it does not wait for the gear shifting device to start shifting operation in response to the shift command. Therefore, due to the delay (bad response) from when the shift command is input until the hydraulic clutch is disengaged, the gear-type transmission is started to shift while the hydraulic clutch is initially engaged, When an excessive load is applied to the gear due to traveling load, the inconvenience that the gear is not switched smoothly is prevented, and the gear shifting operation of the gear transmission can be smoothly performed. .

  On the other hand, a check oil passage for draining oil and a clutch control oil passage for controlling on / off of the hydraulic clutch are provided during gear switching, and the clutch control oil passage and the check oil passage are moved from the clutch control oil passage to the check oil passage. When the check oil passage is in the oil drain state during the gear change, the oil is drained from the clutch control oil passage through the check valve.

  Normally, before the check oil passage is in the oil drain state, the hydraulic clutch is switched to the disconnected state by the electromagnetic proportional pressure control valve. However, if the hydraulic clutch is not switched to the disengaged state in response to a shift command input due to a failure, etc., oil will still enter the hydraulic clutch via the clutch control oil passage even when the check oil passage is in the oil drain state. Supplied and the hydraulic clutch is kept engaged.

  In this case, as described above, oil is drained from the clutch control oil passage to the check oil passage, so that the hydraulic clutch is disengaged. As a result, even if the hydraulic clutch cannot be switched to the disengaged state due to a gear shift command input due to a failure or the like, the hydraulic clutch will be disengaged and the gear can be switched, and the gear can be switched while the hydraulic clutch is in the engaged state. Inconveniences such as damage to the transmission are prevented.

  In addition, when the hydraulic clutch is disengaged, the check valve is provided with a spring so that an initial pressure is applied to the clutch control oil passage leading to the hydraulic clutch switching valve. An initial pressure is applied to. Therefore, when the hydraulic clutch is switched to the engaged state, the operation of the switching valve is performed smoothly and speedily, and the response of the hydraulic clutch reaction (switching to the engaged state) is improved.

  FIG. 1 is a transmission diagram of a main part of a transmission in a tractor that is a work vehicle adopting the present invention. A transmission 2 including a hydraulic clutch 1 is formed in the center case of the transmission. The transmission 2 includes a four-stage main transmission 3 having gears for 1 to 4 speeds, a forward / reverse switching device 4 for switching between forward and backward, and a low speed (L) and a high speed having gears for low speed and high speed. (H) two-stage auxiliary transmission 6 is provided, and forward and reverse shifts of eight stages are possible.

  The main transmission 3 includes an input shaft 11 to which a driving force is input from the engine 7 via a main clutch 8 and a gear 9 and an output shaft 12 for outputting the driving force. A first drive gear 13, a second drive gear 14, a third drive gear 16, and a fourth drive gear 17 are mounted on the input shaft 11 so as to rotate together.

  The output shaft 12 includes a first driven gear 18 that meshes with the first drive gear 13, a second driven gear 19 that meshes with the second drive gear 14, and a third driven gear 21 that meshes with the third drive gear 16. The fourth driven gear 22 meshing with the fourth drive gear 17 is rotatably supported.

  The output shaft 12 includes a first speed position at which the output shaft 12 is linked to the first driven gear 18, a second speed position at which the output shaft 12 is linked to the second driven gear 19, and the output shaft 12 is connected to the first driven gear 18 and A synchromesh-type first shift member 23 that can be switched to a neutral position that is not interlocked with any of the second driven gears 19 is mounted between the first driven gear 18 and the second driven gear 19.

  The output shaft 12 includes a third speed position at which the output shaft 12 is linked to the third driven gear 21, a fourth speed position at which the output shaft 12 is linked to the fourth driven gear 22, and the output shaft 12 is connected to the third driven gear 21 and A synchromesh second shift member 24 that can be switched to a neutral position that is not interlocked with any of the fourth driven gears 22 is mounted between the third driven gear 21 and the fourth driven gear 22.

  When both the first shift member 23 and the second shift member 24 are switched to the neutral position, the main transmission 3 is in a neutral state in which the driving force of the input shaft 11 is not transmitted to the output shaft 12.

  When the first shift member 23 is switched to the first speed position while the second shift member 24 is switched to the neutral position, the first speed state is established in which the power of the input shaft 11 is transmitted to the output shaft 12 at a low speed. When the first shift member 23 is switched to the second speed position while the second shift member 24 is switched to the neutral position, the power of the input shaft 11 is transmitted to the output shaft at a higher speed than the first speed state 2. It becomes a speed state.

  When the first shift member 23 is switched to the neutral position and the second shift member 24 is switched to the third speed position, the power of the input shaft 11 is transmitted to the output shaft 12 at a higher speed than in the second speed state. It becomes a speed state. When the first shift member 23 is switched to the neutral position and the second shift member 24 is switched to the fourth speed position, the power of the input shaft 11 is transmitted to the output shaft 12 at a higher speed than in the third speed state. 4 speed state.

  The driving force of the output shaft 12 is transmitted to the input shaft 26 via the hydraulic clutch 1. The hydraulic clutch 1 is switched to an on state in which the driving force of the output shaft 12 is transmitted to the input shaft 26 when oil is supplied. The hydraulic clutch 1 is switched to a disconnected state in which the driving force of the output shaft 12 is not transmitted to the input shaft 26 by the oil drain.

  The driving force shifted by the main transmission 3 transmitted to the input shaft 26 is converted into a driving force in the forward or reverse direction by the forward / reverse switching device 4 and output to the transmission shaft 27. The auxiliary transmission 6 shifts the driving force input to the transmission shaft 27 to the output shaft 28 in two stages and outputs it. A low speed gear 29 and a high speed gear 31 of the auxiliary transmission 6 are rotatably mounted on the transmission shaft 27.

  The transmission shaft 27 has a synchromesh-type shift member 32 that can be switched between an L position for transmitting the driving force from the transmission shaft 27 to the low speed gear 29 and an H position for transmitting the driving force from the transmission shaft 27 to the high speed gear 31. Is installed.

  A low-speed driven gear 33 that meshes with the low-speed gear 29 and a high-speed driven gear 34 that meshes with the high-speed gear 31 are attached to the output shaft 28 so as to rotate integrally. When the shift member 32 is switched to the L position, the subtransmission 6 is switched to the low speed (L) state, and when the shift member 32 is switched to the H position, the subtransmission 6 is switched to the high speed (H) state. A high-speed driving force or a low-speed driving force is output. A driving force is output from the output shaft 28 to the rear wheel side or front wheel side of the tractor.

  As shown in FIGS. 2 to 4, the operation of the main transmission 3, the sub-transmission 6, and the hydraulic clutch 1 in the transmission is controlled by a control unit 36 that is a hydraulic operation unit attached to the transmission case.

  The control unit 36 includes a first hydraulic cylinder 37 that is an actuator that operates the first shift member 23 of the main transmission 3 and a second hydraulic cylinder 38 that is an actuator that operates the second shift member 24 of the main transmission 3. And a sub transmission hydraulic cylinder 39 as an actuator for operating the shift member 32 of the sub transmission 6.

  In the control unit 36, solenoid valves (solenoid valves) for operating the first hydraulic cylinder 37, the second hydraulic cylinder 38, and the auxiliary transmission hydraulic cylinder 39 are concentrated, and a piped transmission valve assembly 47 is attached. Yes.

  The transmission valve assembly 47 includes an auxiliary transmission solenoid valve 41 for controlling the operation of the auxiliary transmission hydraulic cylinder 39, a first speed solenoid valve 42 for operating the first hydraulic cylinder 37 to switch the main transmission 3 to the first speed state, A second speed solenoid valve 43 that operates the first hydraulic cylinder 37 to switch the main transmission 6 to the second speed state, and a third speed solenoid valve 44 that operates the second hydraulic cylinder 38 to switch the main transmission 6 to the third speed state. And a 4-speed solenoid valve 46 for operating the second hydraulic cylinder 38 to switch the main transmission 6 to the 4-speed state is attached and piped.

  The control unit 36 includes an oil temperature sensor 48, a hydraulic sensor 49, an auxiliary transmission check valve 51 operated by the operation of the auxiliary transmission hydraulic cylinder 39, a first check valve 52 operated by the operation of the first hydraulic cylinder 37, 2. A second check valve 53 operated by the operation of the hydraulic cylinder 38, a proportional pressure control solenoid valve 54 for operating the hydraulic clutch 1, a shuttle valve 56, a relay check valve 55, and a filter are integrally attached.

  As shown in FIG. 5, the first speed solenoid valve 42, the second speed solenoid valve 43, the third speed solenoid valve 44, the fourth speed solenoid valve 46, the auxiliary transmission solenoid valve 41, and the proportional pressure control solenoid valve 54 are provided. Is connected to the output side of a microcomputer unit 50 having a microcomputer as a hydraulic operation control means.

  On the input side of the microcomputer unit 50, a shift up switch 57 and a shift down switch 58 for detecting an instruction for upshifting and downshifting at the time of shifting are connected. A shift command is input to the microcomputer unit 56 by the upshift switch 57 and the downshift switch 58. A hydraulic pressure sensor 49, an oil temperature sensor 48, and the like are also connected to the input side of the microcomputer unit 50.

  The control unit 36 and the microcomputer unit 50 constitute a hydraulic transmission mechanism that automatically turns on and off the hydraulic clutch 1 and shifts the main transmission 3 and the auxiliary transmission 3 by hydraulic pressure.

  The operation of each solenoid valve 41, 42, 43, 44, 46 is controlled by the microcomputer unit 50 based on data from the shift up switch 57, the shift down switch 58, the hydraulic sensor 57, etc. by the hydraulic transmission mechanism. 50 controls the operation of the main transmission 3, the sub-transmission 6, and the hydraulic clutch 1, and shifts (shift-up, shift-down, etc.) are automatically performed.

  The shift-up switch 57 and the shift-down switch 58 are a main transmission lever for performing a switching operation of the main transmission 3 provided on the driver seat side of the tractor and a sub-transmission lever for performing a switching operation of the auxiliary transmission 6. In addition to being operated according to the operation, it can be configured to be operated by an operation button or the like for operating upshifting or downshifting. In addition, an automatic shift (automatic) can be achieved by automatically inputting a shift up / down shift command signal to the microcomputer in accordance with the traveling state of the traveling machine body.

  The hydraulic circuit of the microcomputer unit 50 will be described. As shown in FIG. 6, the oil from the hydraulic pump is supplied to the input line I of the transmission valve assembly 47 through the check valve 62 and the filter 63. The input line I includes an input port P1 of the auxiliary transmission solenoid valve 41, an input port P4 of the first speed solenoid valve 42, an input port P3 of the second speed solenoid valve 43, an input port P6 of the third speed solenoid valve 44, and a fourth speed solenoid valve. 46 input ports P5 are connected.

  The output port A1 of the auxiliary transmission solenoid valve 41 is connected to a port A on the piston push-out side in the two-position switching type auxiliary transmission hydraulic cylinder 39. Oil is supplied from the input line I to the port B on the piston push-back side in the auxiliary transmission hydraulic cylinder 39.

  To the output port A4 of the first-speed solenoid valve 42, a small-diameter piston push-back port E in the three-position switching type first hydraulic cylinder 37 is connected. The output port A3 of the second speed solenoid valve 43 is connected to the port C on the large-diameter piston extrusion side in the first hydraulic cylinder 37. A port D on the large-diameter piston push-back side (small-diameter piston push-out side) in the first hydraulic cylinder 37 is connected to an oil sump.

  The output port A6 of the third speed solenoid valve 44 is connected to a port H on the small diameter piston push-back side in the three-position switching type second hydraulic cylinder 38. The output port A5 of the 4-speed solenoid valve 46 is connected to the port F on the large-diameter piston extrusion side in the second hydraulic cylinder 38. A port G on the large-diameter piston push-back side (small-diameter piston push-out side) in the second hydraulic cylinder 38 is connected to an oil sump.

  The input port P1 and output port A1 of the auxiliary transmission solenoid valve 41, the input port P4 and output port A4 of the first speed solenoid valve 42, the input port P3 of the second speed solenoid valve 43, the output port A3 and the input port of the third speed solenoid valve 44 P6, output port A6, and input port P5 and output port A5 of the 4-speed solenoid valve 46 are connected with each solenoid valve 41, 42, 43, 44, 46 being OFF.

  When each solenoid valve is turned ON 41, 42, 43, 44, 46, the output port A 1 and switching port of the auxiliary transmission solenoid valve 41, the output port A 4 and switching port of the first speed solenoid valve 42, and the output port of the second speed solenoid valve 43 A3 is connected to the switching port, the output port A6 of the third speed solenoid valve 44 is connected to the switching port, and the output port A5 of the fourth speed solenoid valve 46 is connected to the switching port.

  The oil output from the filter 63 is also supplied to the input port P7 of the proportional pressure control solenoid valve 54 via another filter 64. An output port A7 of the proportional pressure control solenoid valve 64 is connected to a clutch control line LC for controlling on / off of the hydraulic clutch 1.

  The hydraulic clutch 1 is connected to the clutch control line LC via a filter 66 and a shuttle valve 56. The switching port of the proportional pressure control solenoid valve 54 is connected to an oil sump. The proportional pressure control solenoid valve 54 is connected to the output port A7 and the switching port in the OFF state.

  The proportional pressure control solenoid valve 54 is configured to change the oil pressure of oil output from the input port P7 to the output port A7 according to the voltage in the ON state. By controlling the voltage of the proportional pressure control solenoid valve 54, the input port P7 is connected to the output port A7, and oil whose oil pressure is controlled is supplied to the clutch control line D.

  The oil output from the filter 63 is also supplied to the pressure check line LP via another filter 66. A hydraulic sensor 49 is attached to the pressure check line LP. The oil pressure sensor 49 detects the oil pressure of the pressure check line LP.

  An auxiliary transmission check valve 51 corresponding to the auxiliary transmission hydraulic cylinder 39 and a first check valve 52 corresponding to the first hydraulic cylinder 37 are connected to the pressure check line LP. The pressure check line LP and the clutch control line LC are connected via a relay check valve 55.

  The other port of the auxiliary transmission check valve 51 is connected to an oil sump. A second check valve 53 corresponding to the second hydraulic cylinder 38 is connected in series to the other port of the first check valve 52. The other port of the second check valve 53 is connected to the oil sump.

  The auxiliary transmission check valve 51, the first check valve 52, the second check valve 53, and the relay check valve 55 are spring check valves. However, the auxiliary transmission check valve 51, the first check valve 52, and the second check valve 53 are pilot operated check valves. The temperature of the oil output from the filter 63 is controlled by the oil temperature sensor 48.

  The auxiliary transmission hydraulic cylinder 39 switches the shift member 32 to the L position when oil is drained from the port A when the auxiliary transmission solenoid valve 41 is turned ON and the piston rod is contracted. On the other hand, when the auxiliary transmission solenoid valve 41 is turned off and the oil is supplied to the port A and the piston rod is extended, the shift member 32 is switched to the H position to perform the auxiliary transmission.

  In the first hydraulic cylinder 37, when the second speed solenoid valve 43 is turned OFF and the first speed solenoid valve 42 is turned ON, the oil is discharged from the port E in a state where the oil is supplied to the port C, and the piston rod is extended. The first shift member 23 is switched to the first speed position.

  On the other hand, when the first speed solenoid valve 42 is turned off and the second speed solenoid valve is turned on, when the oil is supplied to the port E and the oil is discharged from the port C and the piston rod is contracted, the first shift member 23 is moved. Switch to the 2nd gear position.

  During the push-out of the piston to the extended state of the piston rod of the first hydraulic cylinder 37 and the push-back of the piston to the contracted state of the piston rod, the first shift member 23 is in the neutral position. When oil is supplied to the ports C and E by turning off the second speed solenoid valve 43 and turning off the first speed solenoid valve 42, the piston rod is positioned at an intermediate position between the extended state and the contracted state, and the first shift member 23 Is in the neutral position.

  In the second hydraulic cylinder 38, when the oil is supplied to the port F by the OFF of the 4-speed solenoid valve 46 and the ON of the 3-speed solenoid valve 44, the oil is discharged from the port H, and the piston rod is extended. Then, the second shift member 24 is switched to the third speed position. On the other hand, when the third speed solenoid valve 44 is turned off and the fourth speed solenoid valve 46 is turned on, when the oil is supplied to the port H and the oil is discharged from the port F and the piston rod is contracted, the second shift member 24 is moved. To the 4th gear position.

  During the push-out of the piston to the extended state of the piston rod of the second hydraulic cylinder 38 and the push-back of the piston to the contracted state of the piston rod, the second shift member 24 is in the neutral position. When oil is supplied to the port F and the port H by turning off the third speed solenoid valve 44 and turning off the fourth speed solenoid valve 46, the piston rod is positioned at an intermediate position between the extended state and the contracted state, and the second shift member 24 Is in the neutral position.

  With the above-described configuration, as shown in FIG. 7, the above-described 8-speed shift is performed from the first speed to the fourth speed, while the sub-speed solenoid valve 41 is ON, the first speed solenoid valve 42 or the second speed solenoid valve 43 or 3. The speed is changed by switching the high speed solenoid valve 44 or the fourth speed solenoid valve 46 to the ON state.

  5th to 8th speeds, when the sub-speed solenoid valve 41 is OFF and the 1st speed solenoid valve 42, the 2nd speed solenoid valve 43, the 3rd speed solenoid valve 44, or the 4th speed solenoid valve 46 are switched to the ON state, respectively. Shifted.

  In response to the shift command from the shift-up switch 57 and the shift-down switch 58, the microcomputer unit 50 causes the sub-shift solenoid valve 41, the first speed solenoid valve 42, the second speed solenoid valve 43, the third speed solenoid valve 44, and the fourth speed solenoid valve 46. ON / OFF is set, and the gear is automatically changed by hydraulic pressure.

  In this case, the 3rd speed solenoid valve 44 and the 4th speed solenoid valve 46 are always in the OFF state during the 1st speed and 2nd speed shifts and the 5th speed and 6th speed shifts, and the 3rd speed and 4th speed shifts and the 7th speed and 8th speed. During a speed change, the first speed solenoid valve 42 and the second speed solenoid valve 43 are always OFF.

  When the main transmission 3 is in the neutral state, the sub-transmission solenoid valve 41 is OFF. At this time, by turning the sub-transmission solenoid valve 41 ON, the shift from the neutral state to the first speed state is performed. Response is improved.

  A cam 67 is provided between the auxiliary transmission check valve 51 and the auxiliary transmission hydraulic cylinder 39. The auxiliary speed change check valve 51 is pilot-operated by the cam 67 and opened during the switching of the shift member 32 to the L position or H position by the auxiliary speed change hydraulic cylinder 39. Thereby, the oil of the pressure check line LP is drained. When the switching of the shift member 32 to the L position or the H position is completed, the auxiliary transmission check valve 51 is closed.

  A cam 68 is provided between the first check valve 52 and the first hydraulic cylinder 37. When the first shift member 23 is switched to the neutral position by the first hydraulic cylinder 37, the first check valve 52 is pilot operated by the cam 68 and opened. When the first shift member 23 is switched to the first speed position or the second speed position, the first check valve 52 is closed.

  A cam 69 is provided between the second check valve 53 and the second hydraulic cylinder 38. When the second hydraulic cylinder 38 sets the second shift member 24 to the neutral position, the pilot operation is performed by the cam 69 and the second check valve 53 is opened. When the second hydraulic cylinder 38 switches the second shift member 24 to the third speed position or the fourth speed position, the second check valve 53 is closed.

  When the main transmission 3 is in the neutral state, the first shift member 23 and the second shift member 24 are both in the neutral position, so that the oil in the pressure check line C is drained through the first check valve 52 and the second check valve 53. Is done.

  With the above structure, during the shift operation of the auxiliary transmission 6, the auxiliary shift check valve 51 is opened, the oil in the pressure check line LP is drained, and the hydraulic pressure in the pressure check line LP is reduced. During the 3rd and 4th speed shift operation and the 7th and 8th speed shift operation by the main transmission 3, the oil of the pressure check line LP is drained via the second check valve 53, and the pressure check line LP Hydraulic pressure decreases.

  Since the second check valve 53 is always open during the 1st and 2nd speed shift operations and the 5th and 6th speed shift operations by the main transmission 3, the first check valve 52 and the second check valve 53 are opened. Accordingly, the oil in the pressure check line LP is drained, and the hydraulic pressure in the pressure check line LP decreases.

  When the shift operation of the sub-transmission device 6 is completed and when the shift operation of the main transmission device 3 is completed, the pressure check line LP is closed, and the hydraulic pressure of the pressure check line LP increases and returns. A hydraulic pressure sensor 49 detects a decrease in hydraulic pressure and a return of the hydraulic pressure on the pressure check line LP, that is, a shift operation of the auxiliary transmission 6 or the main transmission 6 and completion of the shift operation. The oil pressure sensor 49 digitally detects the oil pressure drop and the oil pressure return of the pressure check line LP by turning OFF and ON.

  During the shifting operation, the hydraulic clutch 1 needs to be disengaged. For this reason, the proportional pressure control solenoid valve 54 is electrically switched off by the microcomputer unit 50 when the shift command is input to the microcomputer unit 50 side.

  As a result, oil in the clutch control line LC is drained, and supply of oil to the hydraulic clutch 1 via the shuttle valve 56 is stopped. As a result, the oil in the hydraulic clutch 1 is drained to the oil reservoir via the shuttle valve 56, and the hydraulic clutch 1 is turned off.

  When the completion of the speed change operation is detected by the hydraulic sensor 49 and input to the microcomputer unit 50 side, the proportional pressure control solenoid valve 54 is voltage-controlled by the microcomputer unit 50 and the hydraulic pressure is controlled from the proportional pressure control solenoid valve 54. Oil is supplied to the clutch control line LC.

  When the hydraulic pressure of the pressure check line LP rises and returns due to the completion of the shift operation, the proportional pressure control solenoid valve 54 increases the hydraulic pressure with respect to the hydraulic clutch 1 while gradually increasing the hydraulic pressure, as shown in FIG. Supply. As a result, the hydraulic clutch 1 is connected with reduced shock at the time of connection.

  However, after the proportional pressure control solenoid valve 54 is electrically turned off by an instruction from the microcomputer unit 50 based on the shift command, a predetermined time elapses before the completion of the shift operation is detected by the hydraulic sensor 49. The voltage is controlled by the microcomputer unit 50, and a predetermined oil pressure lead oil is supplied to the clutch control line LC (shuttle valve 56).

  The oil pressure of the lead oil is such that the shuttle valve 56 is not switched, the hydraulic clutch 1 is engaged and does not operate, and the relay check valve 55 is not opened against the biasing force of the spring. Thus, a certain amount of oil is supplied to the shuttle valve 56 in advance, and an initial pressure is applied.

  As described above, since the initial pressure is applied to the shuttle valve 56 (a certain amount of oil is supplied in advance), the normal hydraulic oil that enters and operates the hydraulic clutch 1 is supplied from the proportional pressure control solenoid valve 54 to the clutch control line LC. , The shuttle valve 56 is switched with good response, and the hydraulic clutch 1 is switched to the engaged state with speed and good response.

  Since the opening pressure of the relay check valve 55 is set to a pressure lower than the oil pressure discharged by the return spring of the hydraulic clutch 1, the sub-shift check valve 51, the first check valve 52, and the second check The state that the valve 53 is closed can be detected quickly, and oil is supplied to the clutch control line LC at an earlier timing than the operation of the auxiliary transmission hydraulic cylinder 39, the first hydraulic cylinder 37, and the second hydraulic cylinder 38 is completed. The response of the engagement operation of the hydraulic clutch 1 is higher.

  When the microcomputer unit 50 detects the electrical shift command as described above, the microcomputer unit 50 electrically turns off the proportional pressure control solenoid valve 54, so that the delay of the disconnection operation of the hydraulic clutch 1 is shortened, and the auxiliary transmission hydraulic cylinder The hydraulic clutch 1 can be disengaged before the operation of 39, the first hydraulic cylinder 37, and the second hydraulic cylinder 38.

  Since the hydraulic clutch 1 is turned off with good response without waiting for the movement of the pistons of the auxiliary transmission hydraulic cylinder 39, the first hydraulic cylinder 37, and the second hydraulic cylinder 38, the auxiliary transmission hydraulic cylinder 39 and the first hydraulic cylinder 37 When the piston of the second hydraulic cylinder 38 moves, the hydraulic clutch 1 is already disengaged, and the shift member 32, the first shift member 23, and the second shift member 24 are smoothly switched with a low load, and the sub-shift The sub-shift by the device 6 and the main shift by the main transmission 3 can be performed smoothly and with a small shift shock.

  On the other hand, even if an electrical shift command is given to the microcomputer unit 50, the proportional pressure control solenoid valve 54 may not be turned off due to a failure of the microcomputer unit 50 or the like. In this case, even if the shift operation is performed by the auxiliary transmission hydraulic cylinder 39, the first hydraulic cylinder 37, and the second hydraulic cylinder 38, the transmission cannot be performed or the gears of the auxiliary transmission 6 and the main transmission 3 are connected. It may be damaged.

  On the other hand, according to the hydraulic circuit of the present control unit 36, the sub-transmission check valve 51, the first check valve 52, and the second check valve 53 are operated when the sub-transmission 6 and the main transmission 3 are shifted. By opening, the hydraulic pressure of the clutch control line LC becomes higher than the hydraulic pressure of the pressure check line LP.

  As a result, the relay check valve 55 is opened against the biasing force of the spring of the relay check valve 55, and the oil in the clutch control line LC is drained. For this reason, the hydraulic pressure of the clutch control line LC is lowered, the oil of the hydraulic clutch 1 is drained to the oil reservoir via the shuttle valve 56, and the hydraulic clutch 1 is turned off.

  For this reason, even if the lifting / lowering control solenoid valve 54 is not turned off in response to the shift command, if the movement of the pistons of the sub-shift hydraulic cylinder 39, the first hydraulic cylinder 37, and the second hydraulic cylinder 38 is awaited, the shift member The hydraulic clutch 1 is in a disengaged state when switching between the first shift member 32, the first shift member 23, and the second shift member 24, and the shift members 23, 24, 32 can be switched. 3 can be performed.

  In the above-described embodiment, the transmission operation of the main transmission 3 and the auxiliary transmission 6 in the transmission is automatically performed by hydraulic pressure, but a gear-type transmission such as a forward / reverse transmission 4 or an ultra-low speed transmission is used. The shift operation of the apparatus may be automatically performed by hydraulic pressure, or all the shift operations in the transmission may be automatically performed by hydraulic pressure.

It is a transmission diagram of the transmission of a tractor. It is a side view of a control unit. FIG. 3 is a view as seen from an arrow A in FIG. 2. FIG. 4 is a view taken in the direction of arrow B in FIG. 3. It is a block diagram of a microcomputer unit part. It is a hydraulic circuit diagram of a control unit. It is a table | surface figure which shows the operating state of the solenoid valve with respect to each transmission. It is a graph which shows the relationship between a transmission command, a hydraulic pressure sensor, and the hydraulic pressure of a clutch control line.

1 Hydraulic clutch 3 Main transmission (gear-type transmission)
6 Sub-transmission (gear-type transmission)
37 Sub-transmission hydraulic cylinder (hydraulic cylinder)
38 1st hydraulic cylinder (hydraulic cylinder)
39 Second speed hydraulic cylinder (hydraulic cylinder)
41 Sub-transmission solenoid valve (solenoid valve)
42 1-speed solenoid valve (solenoid valve)
43 2-speed solenoid valve (solenoid valve)
44 3-speed solenoid valve (solenoid valve)
46 4-speed solenoid valve (solenoid valve)
50 Microcomputer unit (control means)
54 Proportional pressure control solenoid valve (Electromagnetic proportional pressure control valve)
55 Relay check valve (check valve)
56 Shuttle valve (switching valve)
LP pressure check line (check oil passage)
LC Clutch control line (Clutch control oil passage)

Claims (2)

On the basis of the shift command, the hydraulic clutch (1) is turned on and off, and the shift solenoid valves (41), (42), (43), (44), (46) are switched to switch the hydraulic cylinders (37), (38 ), (39) by operating the gear-type transmissions (3), (6) and automatically changing the travel speed, the hydraulic speed change mechanism includes a gear change mechanism. Based on the command, the switching valve (56) of the hydraulic clutch (1) is switched by the electromagnetic proportional pressure control valve (54), the hydraulic clutch (1) is disengaged, and the gear-type transmissions (3), (6) based on the shift operation is completed, Bei give a control means for actuating enters the hydraulic clutch (1) by controlling the electromagnetic proportional pressure control valve (54) (50), the gear type transmission (3), (6) Check that the oil drains during the shifting operation. An oil passage (LP) and a clutch control oil passage (LC) for controlling on / off of the hydraulic clutch (1) are provided. The clutch control oil passage (LC) and the check oil passage (LP) are connected to the clutch control oil passage (LP LC is a hydraulic transmission mechanism of a traveling vehicle connected by a check valve (55) that allows only the flow of oil in the direction from the LC to the check oil passage (LP) . A type in which a check valve (55) is provided with a spring so as to apply an initial pressure to the clutch control oil passage (LC) reaching the switching valve (56) of the hydraulic clutch (1) when the hydraulic clutch (1) is disengaged. The hydraulic transmission mechanism for a traveling vehicle according to claim 1 .

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