JPS6215135A - Hydraulic drive tractor - Google Patents

Abstract

PURPOSE:To eliminate error operation and improve sped change feeling,by operating an operation cylinder through a hydraulic control valve and electromagnetic valves, converted in a manual gear change or an automatic speed change. CONSTITUTION:Five electromagnetic valves S1-S5 are arranged connected in series or in parallel to a hydraulic control valve V which is linked to a gear shift lever 9. When running without automatic speed control responding to the load, the electromagnetic valve S1 is opened, while others S2-S5 are kept closed. The electromagnetic valves S1-S5 are operated by signals only in an automatic speed change control condition. In the automatic speed control operation, the valve S1 is closed to stop the operation of the hydraulic control valve V, while on/off of the pressure oil to the contraction side is through the electromagnetic valve S3 and that to the extension side through S2. The return oil is controlled by the electromagnetic valves S4 and S5. Moreover, the valves S4 and S5 can be driven by pulse signals to slow down the movement of the cylinder C, to improve the feeling of speed change.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention drives an agricultural tractor by a transmission equipped with an HST type transmission, thereby enabling continuously variable speed and reducing the number of revolutions of the engine. etc. to detect the load on the tractor, and use the feedback signal from the load to detect the HST.
The present invention relates to a technology for automatically operating a hydraulic pump swash plate of a type transmission to automatically increase or decrease vehicle speed.

(b) Prior art As for the technology related to an automatic increase/decrease device for tractor working speed, Japanese Patent Application Laid-Open No. 55-83619 and Japanese Patent Application Laid-Open No. 57-17
There was a technology such as that published in Publication No. 5428.

(c) Problems to be Solved by the Invention An object of the present invention is to provide a tractor equipped with an HST type transmission to enable continuously variable speed, and an operating cylinder C for rotating a swash plate of a hydraulic pump. is provided, and the operation cylinder C can be expanded and retracted by a hydraulic control valve (■) that is manually switched based on the operation of the gear shift lever, and when the hydraulic control valve V is used for automatic gear shifting based on load control, when the automatic gear shifting is activated, The gear shift lever rotates on its own even though the shift lever is not operated, giving the operator a sense of anxiety, and the mechanical mechanism from the gear shift lever to the hydraulic control valve has to be operated unnecessarily by the automatic control mechanism. Failure to do so results in a loss of operating force and can also cause malfunctions.

In the present invention, the manual hydraulic control valve (2) is limited to manual operation only, and in the case of automatic shifting, a group of solenoid valves operated by a feedback electric signal is arranged separately to control the hydraulic control valve (V). In addition to stopping the flow of pressure oil, multiple electromagnetic valves were used to feed and stop the pressure oil to the operating cylinder.

In addition, among the solenoid valves that perform automatic gear shifting, the solenoid valve that opens and closes the oil passage on the return oil side of the operating cylinder 〇 is driven by a pulse signal to limit the amount of return oil, and the swash plate 3 of the hydraulic pump 39
The rotational speed of 9a is slowed down to eliminate the impact caused by sudden gear changes and improve the feel of gear shifts.

(d) Means for Solving the Problems The objects of the present invention are as described above. Next, the structure for achieving the objects will be explained.

In an HST type transmission in which the swash plate of the hydraulic pump is configured so as not to be rotated by an operating cylinder, and the operation of the operating cylinder is further configured to be controlled by a manual hydraulic control valve, in addition to the hydraulic control valve. , multiple solenoid valves that automatically switch operating cylinders based on the tractor's load signal are arranged in series or parallel with the hydraulic control valve,
The system is configured to operate an operating cylinder by switching between a hydraulic control valve and a solenoid valve through manual and automatic speed changes.

Furthermore, among the solenoid valves for automatic gear shifting, the expansion and contraction speed of the operating cylinder can be changed by pulse-driving the solenoid valve that releases return oil from the oil chamber of the operating cylinder to the drain circuit.

(e) Embodiments and Functions The objects and structure of the present invention are as described above. Next, the structure of the embodiments shown in the attached drawings and the invention will be explained in detail.

Fig. 1 is a hydraulic circuit diagram of the hydraulically driven tractor of the present invention, Fig. 2 is a control operation diagram showing the working speed and the opening/closing state of the solenoid valve group, Fig. 3 is a diagram showing the relative relationship of each control position, and Fig. 4 is a diagram showing the relative relationship of each control position. The figures are side sectional views of the HST type transmission and the gear type transmission, FIG. 5 is a front view of the same, and FIG. 6 is a side sectional view of the hydraulic control valve V.

The overall hydraulic circuit configuration of this hydraulically driven tractor will be explained with reference to FIG. A is an HST type transmission, which transmits the rotation of the engine E through a hydraulic pump shaft 7 to drive a hydraulic pump 39 and an auxiliary hydraulic pump 53. The hydraulic motor 40 is driven by the pressure oil discharged from the hydraulic pump 39, and the pressure oil discharged by the auxiliary hydraulic pump 53 is sent to the pressure oil port a of the hydraulic control valve V via the relief valve 54. . Pressure oil from another high-pressure engine-mounted pump 43 is also sent to the pressure oil boat a via the solenoid valve S6. The solenoid valve S6 opens only in an emergency when the main clutch device 55 between the engine E and the hydraulic pump shaft 7 is disconnected and the discharge of pressure oil from the auxiliary hydraulic pump 53 is stopped, and the main clutch device 55 is disconnected. The structure is such that the swash plate 39a can be operated by the pressure oil from the engine-mounted pump 43 discharging pressure oil. With this configuration,
When the main clutch device 55 is disengaged, the hydraulic pump shaft 7 does not rotate and the auxiliary hydraulic pump 53 does not discharge pressure oil, but even at this time, the swash plate 39a of the hydraulic pump 39 can be rotated and Since the engine-mounted pump 43 is a high-pressure pump fixed to the engine E, by introducing the high-pressure oil, the swash plate 39a can be safely operated at high speed. The solenoid valve S6 is opened and closed in conjunction with the depression of the main clutch pedal 57 of the tractor. Under normal conditions, when the main clutch device 55 is connected, the solenoid valve S6 is closed. , auxiliary hydraulic pump 5
The operating cylinder C is operated by the pressure oil No. 3.

The essential part of the present invention is that the manual hydraulic control valve V linked to the gear shift lever 9 is provided with five sets of 85 solenoid valves from Sl, arranged in series or in parallel, and the solenoid valve S1 controls the hydraulic control valve (1). 4 of 84 from the other 82.
A set of solenoid valves allows pressure oil to be sent to the operating cylinder C.
This is a controlled stop.

When the vehicle speed is not automatically controlled based on the load, the solenoid valve S1 is fixed in an open state, and the solenoid valves S2, S3, S4, and S5 are fixed in a closed state.

The solenoid valves S1 to 86 are operated by electric signals only during automatic gear shift adjustment.

In other words, in the case of automatic transmission control, pressure oil is transferred to the hydraulic control valve■
The solenoid valve S1 that was sending pressure to the source side of the operating cylinder C closes, the hydraulic control valve V stops operating, and the solenoid valve S3 opens and closes the pressure oil to the source side of the operating cylinder C. The opening and closing are performed by the solenoid valve S2. The return oil from the oil chamber of the operating cylinder C is controlled by other solenoid valves S4 and 85, and the opening and closing of the solenoid valve 3 and the solenoid valve S
4 are opened and closed simultaneously, opening and closing of solenoid valve S2 and solenoid valve S
5 are opened and closed at the same time, and the operation cylinder C is smoothly expanded and contracted.

In addition, in the present invention, the operating cylinder C during automatic control
The solenoid valves S4 and S5 that open and close the drain circuit on the return oil side of the swash plate 39 can be opened and closed intermittently by pulses, and the operation cylinder C is moved at a slow speed.
This is because the rotation speed of a can be adjusted to change the feeling of shifting.

Next, control will be explained using control state diagrams shown in FIGS. 2 and 3.

Various signals are sent to a controller M that compares and calculates feedback signals and set values.

These include the depression of the main clutch pedal 57, the rotation angle of the axle lever 58, the operation of the manual/automatic changeover switch 59, the fluctuation in the rotational speed of the engine E, the rotation angle of the hydraulic lift lever 60, etc.

Further, by using a work setting switch 61 for selecting the work state desired by the operator, it is possible to select "fast", "slow" for "rotary tilling", "fast", "slow", "plow" for "plowing", etc. As a result, the rotation angle of the swash plate 39a of the hydraulic pump 39 is set from β1 to β5.

On the other hand, if the current rotation angle of the swash plate 39a is
It is input as β from 2. Further, the rotational position of the gear shift lever 9 is also input as α from the detection device 41.

Among the numbers indicating the operation of the solenoid valve group in FIG. 2, 1 indicates the "open" state of the solenoid valve, and 0 indicates the "closed" state of the solenoid valve.

In the "standby" mode, all the solenoid valves are "closed" and the speed cannot be changed using the speed change lever 9. "Auto"
In the mode, there are three positions: "speed increase", "hold", and "deceleration". In "speed increase", solenoid valves S1, 83, and 84 open, and "
Solenoid valve S1 opens in "Hold", and solenoid valve S1 opens in "Deceleration".
82 and 35 open.

In the "emergency" mode, the main clutch device 55 is disconnected, the solenoid valve S6 opens, and the high-pressure oil from the engine-mounted pump 43 is sent to the hydraulic control valve (2) or the solenoid valve group, and the auxiliary hydraulic pressure is This compensates for the drop in hydraulic oil pressure due to the stoppage of the pump 53.

With this configuration, when the operator sets a desired speed using the work setting switch 61, the values from β1 to β5 are determined, and the angle of the swash plate 39a is rotated to reach this value. be. In this state, when the load on the work equipment becomes large and the rotation of the engine E decreases, a deceleration signal is issued and the engine is "held" at a certain deceleration position, and when the rotation of the engine E returns, it returns to the original speed. If the rotation of the engine E further decreases, the speed is further reduced repeatedly.

Next, the specific structure will be explained using the configuration shown in FIG.

An HST type transmission is fixed to a lid N on the front side of the mission case M. In addition, on the front of the lid N, other than the part where the HST type transmission is installed, there is an operating cylinder C, a hydraulic control valve ■, and a solenoid valve S1 for controlling the vehicle speed.
・B2, B3, B4, B5, B6, etc. are attached.

The rotation of the tractor engine E is transmitted via the main clutch device 55 to the hydraulic pump shaft 7 of the hydraulic pump 39. The rear end of the hydraulic pump shaft 7 protrudes into the transmission case M and is transmitted to the PTO transmission shaft 4. The PT
PTO speed change is performed between the O speed change shaft 4 and the PTO counter shaft 5. That is, the pTof knee speed shaft 4 upper shaft 4 upper gears 17 and 18 are connected to the sliding gear 19 on the PTO counter shaft 5.
・Fixed gear 2 that is in mesh with 20 and is in constant mesh
3 and 24 gear trains are selected by the engagement of the engaging portions 24a and 25, and three PTO speeds are obtained. P after shifting
The rotation of the TO counter shaft 5 is transmitted from the gear 21 to the gear 22 on the PTO shaft 6.

The rotation after the speed has been changed by the 837 type transmission becomes the rotation of the hydraulic motor shaft 8 of the hydraulic motor 40 and is transmitted to the milk to be taken out and the speed change shaft 1. Sliding gear 11 on the speed change shaft 1.
12 and fixed gears 13 and 14 on the pinion shaft 2, a traveling sub-speed is performed.

The rotation of the pinion shaft 2 is transmitted from the pinion 26 to the differential device.

Further, power is transmitted from the fixed gear 15 on the pinion shaft 2 to the clutch gear 16 of the front wheel drive shaft 3, and the front wheel drive shaft 3 is rotated. 32 is a front wheel drive shaft cover.

In the transmission configuration as described above, the 837 type transmission is fixedly installed in the center on the front surface of the lid N of the minsion case M, and the hydraulic control valve V and the gear shift lever 9 are located on the right side when facing the direction of travel. On the left side, an operating cylinder C and solenoid valves 31 to S6 for automatic control are fixedly arranged.

As shown in FIG. 4, the operating cylinder C is composed of a cylinder case 38 and a piston 36, and the tip of the piston 36 is configured to rotate around the swash plate rotation axis 0 of the swash plate 39a of the hydraulic pump 39. That's what I'm doing. That is, a swash plate rotation arm 37 is fixed to the right end of the swash plate rotation wheel 10, and the tip of a piston 36 is fixed to the swash plate rotation arm 37. Further, the swash plate rotation arm 37 is provided with a detection device 42 composed of a potentiometer or the like for feeding back the rotation angle of the swash plate 39a. Further, the shift lever 9 is also provided with a detection device 41 for detecting the set angle of the shift lever 9.

Further, the configuration of the hydraulic control valve V will be explained with reference to FIG.

A valve case 33 is fixed to the front surface of the lid N, and the rear end of the valve case 33 is fitted to the far side of the lid N which is opened toward the inside of the mission case M. The returned oil is circulated into the mission case M via the drain circuit 26b and the like.

The hydraulic oil in the operating cylinder C is sent to the pressure oil boat a through the piping 50, and reaches the land 26a of the operating spool 26 through the oil hole 27a of the feedback spool 27. The land 26a is the feed bank spool 27
Due to its relative position, it is closed when in neutral, and when the operating cylinder C is extended, pressure oil port a communicates with port 82 on the right side in Fig. 6, and the check valve 35 is pushed open to open the operating cylinder C from the piping H1. It is on the growth side. The return oil from the piping Fl side of this express train is caused by the pressure oil pushing the check valve 35 pushing the slider 52 to the left, opening the check valve 34, and flowing into the B1 port connected to the drain circuit, and flowing into the transmission case M. Go back within.

When operating the operating cylinder C toward the source side, the operating spool 26 slides to the right, and the pressure oil from the pressure oil boat a enters the B1 port through the oil hole 27a of the feedback spool 27, pushing the check valve 34 open. It enters piping F1. At this time, the return oil in the piping H1 on the expansion side is slid to the right by the opposite force of the pressure oil that the slider 52 pushes against the check valve 34, so the check valve 35 is opened, and from here it returns to port 82, and then The oil is recycled into the mission case M through the drain oil passage 26b.

In the hydraulic control valve V, the operating spool 26 has a pin 29 at the tip of a rotating arm 28 that is linked to the gear shift lever 9, and is engaged with the pin 29 through an elongated hole, so that the gear lever 9 can be rotated in the speed increasing/decelerating direction. Then, the operation spool 26 slides relative to the stationary feedback spool 27, and the positions of the land 26a and the oil hole 27a overlap, and the operation cylinder 〇 is moved from the neutral position to the extension side or the source side. The operation cylinder C is expanded and contracted by shifting.

When the swash plate rotation shaft 10 rotates through the piston 36 and the swash plate rotation arm 37 due to the expansion and contraction, the rotation arm fixed to the swash plate rotation shaft 10 conversely rotates as shown in FIG. Since the bottle 30 at the tip of 31 is locked to the feedback spool 27 through a long hole, the feedback spool 27
moves toward the neutral direction that closes the land 26a and the oil hole 27a, and the positional relationship between both spools returns to the initial neutral position, and the rotation of the hydraulic motor 40 becomes stable at a position where the rotation is increased or decreased.

With this configuration, if the operator sets and fixes the shift lever 9 at a desired speed position, the shift lever 9 will remain in the same position and only the rotational speed of the hydraulic motor 40 will be fixed at the position where it will increase or decrease. .

When the feedback spool 27 and the operation spool 26 are in the neutral position after the control is completed, the pressure oil in the left and right oil chambers of the operation cylinder C is blocked by the check valves 34 and 35 because the pressure oil does not flow in enough to move the slider 52. , is completely closed, so the operating cylinder C and therefore the swash plate 3
9a is securely fixed.

(F) Effects of the Invention Since the present invention is constructed as described above, it has the following effects.

First, in a tractor equipped with an HST type transmission and capable of automatically changing gears, there is a hydraulic control valve ■ operated by turning the gear shift lever 9, and an automatic hydraulic control valve controlled based on feedback signals and setting signals. Since the solenoid valve group for control is placed side by side, the shift lever 9 does not rotate freely during automatic gear shifting, unlike in the conventional technology. As a result, there is no need to prepare a wasteful operating force for operating the mechanically configured operating mechanism of the shift lever 9 and the hydraulic control valve V during automatic gear shifting, and the mechanism of the shift lever 9 and the hydraulic control valve V is also unnecessary. This made it possible to eliminate the occurrence of malfunctions caused by movement.

Second, among the solenoid valve group, solenoid valves S4 and 85 open and close the oil passage for return oil discharged from the oil chamber of the operating cylinder C.
By pulse driving, the sliding speed of the operating cylinder C can be slowed down, and the impact caused by sudden gear changes can be alleviated.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram of the hydraulically driven tractor of the present invention, Fig. 2 is a control operation diagram showing the working speed and the opening/closing state of the solenoid valve group, Fig. 3 is a diagram showing the relative relationship of each control position, and Fig. 4 is a diagram showing the relative relationship of each control position. The figure is a side sectional view of the HSTHST type transmission, Figure 5 is the same front view, and Figure 6 is the hydraulic control valve V.
FIG. A...H5T type transmission C...Operating cylinder M...Mission case ■...Hydraulic control valves Sl, S2. S3. S4. S5. S6...Solenoid valve 9...Speed lever 26...Operation spool 27...Feedback spool 34.35...Check valve 39...Hydraulic pump 39a...Hydraulic pump swash plate 40...Hydraulic motor

Claims (2)

[Claims] (1) The swash plate of the hydraulic pump of the HST type transmission is configured to be rotated by an operating cylinder, and the operation of the operating cylinder is further configured to be controlled by a manual hydraulic control valve, in which the hydraulic pump is controlled by a manual hydraulic control valve. In addition to valves, multiple solenoid valves that automatically switch operating cylinders based on tractor load signals are placed in series or parallel with the hydraulic control valve, and the hydraulic control valve and solenoid valve can be controlled by manual or automatic gear shifting. A load control device for a hydraulically driven tractor, characterized in that it is configured to switch and operate an operating cylinder. (2) Among the electromagnetic valves for automatic gear shifting according to claim 1, the expansion and contraction speed of the operating cylinder is controlled by pulse-driving the electromagnetic valve that releases the return oil in the oil chamber of the operating cylinder to the drain circuit. A load control device for a hydraulically driven tractor characterized by being changeable.