JP3887962B2 - Boost control method for tractor hydraulic clutch - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure control method for a hydraulic clutch, and in particular, hydraulic pressure that selectively supplies pressure oil to a plurality of hydraulic clutches by switching a direction control valve, and relieves the pressure oil to change the pressure increase characteristics. The present invention relates to a clutch boost control method.
[0002]
[Prior art]
Conventionally, pressure oil from a hydraulic pump is selectively supplied to a plurality of hydraulic clutches by a switching operation of a directional control valve, and a pressure relief characteristic is adjusted by adjusting a variable relief valve for pressure oil in an oil passage connected to the hydraulic clutch. There is a circuit to be changed, and a booster circuit such as a traveling forward / reverse switching clutch or a PTO forward / reverse switching clutch provided in a work vehicle such as a tractor, a rice transplanter, or a lawn mower is known.
[0003]
For example, a hydraulic clutch for forward / reverse switching is provided with a forward multi-plate clutch and a reverse multi-plate clutch on the front and rear of a drum that rotates integrally with a drive shaft, and an oil passage that leads from the hydraulic pump to the hydraulic clutch. A directional control valve is provided in the middle. By switching the direction control valve, pressure oil is selectively supplied to either the forward supply port or the reverse supply port, and the hydraulic clutch is operated forward or reverse. Further, the pressure oil in the oil passage leading from the hydraulic pump to the hydraulic clutch is adjusted by a variable relief valve.
[0004]
When the directional control valve is switched and the hydraulic clutch is operated, in order to smoothly increase the output rotation of the hydraulic clutch, a large current is applied to the solenoid when the directional control valve is switched, and the clutch piston is moved to the stroke end. Is controlled so as to move in a short time.
[0005]
[Problems to be solved by the invention]
However, the pressure boosting characteristic of pressure oil often changes due to variations in clutch accuracy and temperature characteristics of the direction control valve. If the time during which a large current flows during switching of the directional control valve is long, surge pressure is generated in the pressure of the hydraulic clutch, and the shock when the clutch is connected increases. On the other hand, if the time for passing a large current is short, the clutch piston does not move to the stroke end, the clutch connection is delayed, and the rise of rotation becomes worse.
[0006]
Therefore, in a hydraulic circuit that selectively supplies pressure oil to a plurality of hydraulic clutches by operating the directional control valve, in order to perform stable boost control regardless of variations in clutch accuracy and temperature characteristics of the directional control valve. A technical problem to be solved arises, and the present invention aims to solve this problem.
[0007]
[Means for Solving the Problems]
The present invention has been proposed in order to achieve the above object, and a branch oil passage (51) is provided in an oil passage (49) connecting the hydraulic pump (44) and the direction control valve (46). (51) is provided with a variable relief valve (52), and the pressure oil from the hydraulic pump (44 ) is switched to the forward / reverse switching clutch (31) by switching the direction control valve (46). In the booster circuit of the hydraulic clutch of the tractor (10) for changing the boosting characteristics by relieving the pressure oil in the oil passage connected to the forward / reverse switching clutch (31) , the forward / reverse switching clutch When the variable relief valve (52) is initially set so that the pressure oil supplied to (31) becomes the minimum operating pressure for moving the clutch piston, the direction control valve (46) is switched and the clutch piston starts to move. , Hydraulic clutch out Detecting a change in the rotational speed or output torque, per to boost the pressure oil supplied adjusted to to the hydraulic clutch said variable relief valve (52) according to the change,
Each sensor value is read, a change in the rotational speed or rotational torque of the clutch output shaft for forward / reverse switching (30) is detected, then a rise time Tr of the change in the rotational speed or rotational torque is calculated, and the rise time Tr is defined. Determine if it is within time,
When the rise time Tr is within a specified time and the rotational speed or the magnitude of the rotational torque of the forward / reverse switching clutch output shaft (30) is less than a specified value, a time for outputting a signal to the solenoid (58) the T ₂ is as per reference time, whereas when it becomes larger than the rotational speed or the magnitude of the rotational torque before even within the rise time Tr is defined time reverse switching clutch output shaft (30) is a specified value time, the solenoid (58) without a time than the time for outputting a signal T ₂ the reference time to, whereas, if the rise time Tr exceeds a predetermined time, for outputting the signal to the solenoid (58) T ₂ for a long time that there is no than the reference time,
Furthermore, when initializing the booster circuit, the time from when the forward / reverse lever (17) is operated until the rotation of the wheel is detected is counted, and the time obtained by subtracting a predetermined time from the counted time is the initial time T _1. The present invention provides a pressure control method for a hydraulic clutch of a tractor that uses this for pressure control .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a tractor 10 as an example of a work vehicle. An engine 11 is placed on the front of a vehicle body and is covered with a hood 12. A seat 14 is mounted inside the cabin 13, and a transmission lever 15 and various operation switches are provided. A steering handle 16 is provided in front of the seat 14, and a forward / reverse lever 17 is attached in the vicinity of the steering handle 16. The power of the engine 11 is transmitted to the rear wheel 19 via a gear transmission housed in a transmission case 18 and the power branched from the gear transmission is transmitted from the front wheel power transmission shaft 20 to the front wheel 21. It is configured to be able to.
[0009]
FIG. 2 shows the inside of the transmission case 18, and engine power is transmitted from the main clutch 25 to the first gear 28 of the input shaft 27 through the output gear 26. A drive shaft 30 is provided in parallel with the input shaft 27, and a forward / reverse switching clutch 31 is attached to the drive shaft 30. The forward / reverse switching clutch 31 is provided with a forward multi-plate clutch 33 and a reverse multi-plate clutch 34 respectively before and after a drum 32 that rotates integrally with the drive shaft 30. A forward gear 35 is loosely fitted in front of the forward multi-plate clutch 33, and a reverse gear 36 is loosely fitted in the rear of the reverse multi-plate clutch 34.
[0010]
A counter shaft 37 is provided in parallel with the input shaft 27 and the drive shaft 30, and a counter gear 38 is fixed to the rear end of the counter shaft 37. The counter gear 38 meshes with the second gear 29 provided at the rear end of the input shaft 27 and also meshes with the reverse gear 36. Accordingly, the rotation of the input shaft 27 is transmitted to the forward gear 35 via the first gear 28 and also transmitted to the reverse gear 36 via the second gear 29 and the counter gear 38. That is, the forward gear 35 idles on the drive shaft 30 in the forward direction, and the reverse gear 36 idles on the drive shaft 30 in the reverse direction.
[0011]
As will be described later, when pressure oil is introduced into the forward supply port 40 of the forward / reverse switching clutch 31 by the switching operation of the directional control valve, the clutch piston 41 moves and the forward multi-plate clutch 33 enters. Thus, the rotation of the forward gear 35 is transmitted to the drum 32 via the forward multi-plate clutch 33. Therefore, the drive shaft 30 rotates forward and the aircraft travels forward. On the other hand, when pressure oil is introduced into the reverse feed port 42, the clutch piston 43 moves and the reverse multi-plate clutch 34 is engaged, and the reverse gear 36 rotates via the reverse multi-plate clutch 34. It is transmitted to the drum 32. Accordingly, the drive shaft 30 rotates in the reverse direction and the aircraft travels backward.
[0012]
FIG. 3 shows a hydraulic circuit of a forward / reverse switching clutch 31 as an example of selectively supplying pressure oil to a plurality of hydraulic clutches. Pressure oil discharged from the hydraulic pump 44 passes through a pressure reducing circuit 45 and a part thereof. Is supplied to the forward / reverse switching clutch 31 via the solenoid type directional control valve 46. If the solenoid 47 or 48 is excited by the signal S _C from the controller 50 and the direction control valve 46 is switched from the neutral position (A) to the forward position (B) or the reverse position (C), the hydraulic pump 44 discharges. The pressurized oil is introduced into the supply port 40 or 42 through the oil passage 49, and the forward / reverse switching clutch 31 is operated to move forward or backward.
[0013]
Here, a throttle 61 is provided in an oil passage 49 connecting the hydraulic pump 44 and the direction control valve 47, and a branch oil passage 51 is provided downstream of the throttle 61 and a variable relief valve 52 is interposed. The spool of the variable relief valve 52 is biased by the hydraulic pressure of the spring 53 and the pilot port 54, and the hydraulic pressure on the inlet side is controlled by the combined pressure of the spring pressure and the pilot pressure.
[0014]
Now, when the pilot pressure of the pilot port 54 is low, the spool of the variable relief valve 52 is easy to open, and a large amount of oil in the oil passage 51 returns to the tank 55, so that the hydraulic pressure on the inlet side of the variable relief valve 52, The pressure oil flowing through the oil passage 49 becomes a low pressure. On the other hand, as the pilot pressure of the pilot port 54 increases, the spool of the variable relief valve 52 becomes difficult to open, and the oil pressure on the inlet side of the variable relief valve 52, that is, the pressure oil flowing through the oil passage 49 becomes high. . Thus, by increasing or decreasing the pilot pressure of the variable relief valve 52 controls the supply pressure P _C to the pressure or the forward-reverse switching clutch 31 of the oil passage 49.
[0015]
In the present embodiment, in order to control the pilot pressure of the variable relief valve 52, the oil passage 56 is branched from the front stage of the throttle 61 provided in the oil passage 49, and the pilot of the oil passage 56 and the pilot port 54 is branched. A solenoid type proportional pressure reducing valve 57 is provided between the oil passage 54a.
[0016]
When the solenoid 58 is excited by a signal S _R from the controller 50, the proportional pressure reducing valve 57 moves to reduce the opening of the oil passage 55a communicating with the pilot oil passage 54a and the tank 55, and the pilot oil passage. 54a and the opening of the oil passage 56 are made large. Therefore, by increasing or decreasing the signal S _R to the solenoid 58, it is possible to pressure output of the secondary side of the proportional pressure reducing valve 57 is changed to control the pilot pressure in the pilot port 54. The lubricating oil passage 59 is branched from the front stage of the throttle 61 of the oil passage 49 and connected to the lubricating port of the forward / reverse switching clutch 31.
[0017]
Thus, the pressure oil discharged from the hydraulic pump 44 passes through the pressure reducing circuit 45, and then is led to the oil passage 49 and the branch oil passage 51 that connect the direction control valve 46 through the throttle 61. The variable relief valve 52 provided in the branch oil passage 51 allows the branch oil passage 51 to be moved by the combined pressure of the spring pressure of the spring 53 provided between the relief poppet and the pilot spool and the pilot pressure of the pilot port 54. It is biased in the closing direction.
[0018]
On the other hand, the proportional pressure reducing valve 57 increases or decreases the pilot pressure of the pilot port 54 according to the signal S _R from the controller 50. That is, the pilot pressure in the pilot port 54 when increasing the signal S _R to the solenoid 58 is increased, making it difficult to open the relief poppet 52a spool of the variable relief valve 52, the hydraulic oil pressure in the oil passage 49 leading to the directional control valve 46 Rises.
[0019]
Thus, when the signal S _R is not output from the controller 50 to the solenoid 58 of the proportional pressure reducing valve 57 and the solenoid 58 is off, the pilot pressure of the pilot port 54 of the variable relief valve 52 is minimized. At this time, the pressure in the oil passage 49, that is, the supply pressure P _C to the forward / reverse switching clutch 31 is the minimum operating pressure P _C0 of the clutch piston (the supply port 40 or 42 is filled with pressure oil and the clutch piston 41 or 43 The variable relief valve 52 is initially set so that the pressure immediately before the movement starts.
[0020]
Next, the boost control method of the present invention will be described with reference to FIGS. When the signal S _C is output from the controller 50 and the solenoid 47 or 48 is turned on at time t ₁ , the directional control valve 46 is switched from the neutral position (A) to the forward position (B) or the reverse position (C). Thus, the pressure oil is introduced into the supply port 40 or 42 through the oil passage 49. During the predetermined time T ₁ when switching of the directional control valve 46 is temporarily large signal S _R to the solenoid 58 of the proportional pressure reducing valve 57, the short clutch piston 41 or 43 of the variable relief valve 52 to the stroke end Move in time.
[0021]
As described above, since the pressure of the oil passage 49 is the minimum operating pressure P _C0 of the clutch piston due to the initial setting of the variable relief valve 52, when the direction control valve 46 is switched, the forward / reverse switching is performed. The supply pressure P _C to the clutch 31 immediately becomes the minimum operating pressure P _C0 of the clutch piston, and in combination with temporarily increasing the signal S _R to the solenoid 58 of the proportional pressure reducing valve 57, the forward / reverse switching is performed. supply pressure P _C to use the clutch 31 is smoothly boosted, can be raised smoothly the output rotation of the forward-reverse switching clutch 31.
[0022]
At this time, the time T ₁ of the large signal output to the solenoid 58 becomes longer than necessary, since the surge pressure in the supply pressure P _C as shown in two-dot chain line in FIG. 4 occurs, the forward-reverse switching clutch 31 The output rotational speed or the output torque of the variable relief valve 52 is detected by a sensor, and the variable relief valve 52 is adjusted by changing the signal output to the solenoid 58 in accordance with the output change.
[0023]
FIG. 5 is a flowchart showing the boost control method of the present invention. First, each sensor value is read to detect a change in the rotational speed or rotational torque of the forward / reverse switching clutch output shaft (step 1). Next, the rise time _Tr of the change in the rotational speed or the rotational torque is calculated, and it is determined whether the rise time _Tr is within the specified time (step 2).
[0024]
When the rising time _Tr is within a specified time and the rotational speed or the rotational torque of the forward / reverse switching clutch output shaft is equal to or less than a predetermined value, a time T for outputting a signal to the solenoid 58 Set ₂ to the reference time (step 3 → 4). On the other hand, even if the rising time _Tr is within the specified time, when the rotational speed or rotational torque of the forward / reverse switching clutch output shaft is larger than a predetermined value, the solenoid 58 is returned to. The signal output time T ₂ is set shorter than the reference time (step 3 → 5). On the other hand, the rise time T _r is the case of overtime, to longer than the time for outputting a signal T ₂ the reference time to the solenoid 58 (Step 2 → 6).
[0025]
This eliminates the phenomenon that surge pressure is generated in the supply pressure to the hydraulic clutch and the shock at the time of clutch engagement increases, and the phenomenon that the hydraulic clutch is delayed and the start-up of rotation becomes worse, and stable boost control is achieved. It can be carried out.
[0026]
Here, when initializing the booster circuit, the time from when the forward / reverse lever is operated until the rotation of the wheel is detected is counted, and the time obtained by subtracting a predetermined time (for example, 10 msec) from this count time is initial. The time T ₁ can also be used for boost control, and by reducing variations in the electrical system, the operational feeling on different machines can be made substantially the same.
[0027]
In the present embodiment, the traveling forward / reverse switching clutch has been described. However, the present invention can also be applied to boost control of other hydraulic clutches including a PTO forward / reverse switching clutch.
[0028]
Thus, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.
[0029]
【The invention's effect】
As described in detail in the above embodiment, the present invention detects a change in the output speed or output torque of the hydraulic clutch when the clutch piston starts to move when the directional control valve is switched to connect the hydraulic clutch. Since the pressure oil supplied to the hydraulic clutch is boosted by adjusting the variable relief valve according to the change, surge pressure is generated in the supply pressure to the hydraulic clutch, and the shock at the time of clutch engagement increases. It is possible to prevent a phenomenon in which the connection of is delayed and the rise of rotation deteriorates.
Further, when initializing the booster circuit, the time from when the forward / reverse lever (17) is operated until the wheel rotation is detected is counted, and the time obtained by subtracting a predetermined time from the counted time is the initial time T _1. Since this is used for boost control, the operational feeling on different machines can be made substantially the same by reducing variations in the electrical system.
Thus, stable boost control can be performed regardless of variations in clutch accuracy and temperature characteristics of the direction control valve.
[Brief description of the drawings]
The figure shows an embodiment of the present invention.
FIG. 1 is a side view of a tractor as an example of a work vehicle.
FIG. 2 is a developed cross-sectional view showing the inside of a side surface of a mission case.
FIG. 3 is a hydraulic circuit diagram of a forward / reverse switching clutch.
FIG. 4 is a time chart of boost control.
FIG. 5 is a flowchart of boost control.
[Explanation of symbols]
31 Forward-reverse switching clutch 33 Forward multi-plate clutch 34 Reverse multi-plate clutch 41, 43 Clutch piston 44 Hydraulic pump 46 Direction control valve 47, 48 Solenoid 49 Oil path 50 Controller 51 Branch oil path 52 Variable relief valve 57 Proportional pressure reduction valve

Claims (1)

A branch oil passage (51) is provided in an oil passage (49) connecting the hydraulic pump (44) and the direction control valve (46) , and a variable relief valve (52) is interposed in the branch oil passage (51) , so that the hydraulic pressure is increased. oil connecting the hydraulic fluid from the pump (44) to alternatively supply to the front of the machine body backward switching clutch (31) by switching operation of the directional control valve (46), the front-reverse switching clutch (31) In the booster circuit of the hydraulic clutch of the tractor (10) that relieves the pressure oil on the road and changes the booster characteristic,
The variable relief valve ( 52) is initially set so that the pressure oil supplied to the forward / reverse switching clutch (31) becomes the minimum operating pressure for moving the clutch piston, and the direction control valve (46) is switched to change the clutch. when the piston begins to move, per the detecting a change in the output rotational speed or output torque of the hydraulic clutch, by adjusting the variable relief valve (52) for boosting the pressure oil supplied to the hydraulic clutch according to the change ,
Each sensor value is read, a change in the rotational speed or rotational torque of the clutch output shaft for forward / reverse switching (30) is detected, then a rise time Tr of the change in the rotational speed or rotational torque is calculated, and the rise time Tr is defined. Determine if it is within time,
When the rise time Tr is within a specified time and the rotational speed or the magnitude of the rotational torque of the forward / reverse switching clutch output shaft (30) is less than a specified value, a time for outputting a signal to the solenoid (58) the T ₂ is as per reference time, whereas when it becomes larger than the rotational speed or the magnitude of the rotational torque before even within the rise time Tr is defined time reverse switching clutch output shaft (30) is a specified value time, the solenoid (58) without a time than the time for outputting a signal T ₂ the reference time to, whereas, if the rise time Tr exceeds a predetermined time, for outputting the signal to the solenoid (58) T ₂ for a long time that there is no than the reference time,
Furthermore, when initializing the booster circuit, the time from when the forward / reverse lever (17) is operated until the rotation of the wheel is detected is counted, and the time obtained by subtracting a predetermined time from the counted time is the initial time T _1. As described above, the pressure control method for the hydraulic clutch of the tractor is provided for pressure control.

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