JPS6218333A - Load controlling device for farming tractor - Google Patents

Abstract

PURPOSE:To improve operability by configurating a device in such a way that, while an automatic load control is being effected, when a working condition is selected by a work setting switch, a range for the movement of a cylinder for operating a swash plate of a hydraulic pump in a HST type speed change gear can be set depending on the working condition. CONSTITUTION:In a hydraulic pressure driven tractor, both a variable displacement hydraulic pump 39 and an auxiliary pump 53 are driven by an engine E, and a hydraulic motor 40 is driven by a discharge oil pressure from the pump 39. Discharge oil pressure from the auxiliary pump 53 is applied to both a hydraulic pressure control valve V which is linked with a speed change lever 9 and an engine mounted pump 43. And an operating cylinder C which controls a swash plate 39a of the said pump 39 is controlled by means of controlling both the valve V and solenoid valves V1 through V5. In this case, while an automatic load control is being effected, when a working condition is selected out of such ones as a rotary caltivation, a tilling a rice field in preparation for transplanting young rice plant, plowing and the like, a device is configurated in such a way that a rotating angle of the swash plate 39a of the hydraulic pump 39 can be set, that is, the maximum running speed can be set depending on the working condition.

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 A known technology that uses an HST type transmission as a tractor transmission and enables automatic adjustment of working speed is a technology such as that disclosed in Japanese Patent Application Laid-open No. 83619/1983. .

(c) Problems to be Solved by the Invention The object of the present invention is to provide an operating cylinder for rotating the swash plate of a hydraulic pump in a tractor that is equipped with an HST type transmission to enable continuously variable speed. C is provided, and the solenoid valve is turned on by the feedback signal of the increase or decrease in load detected by the increase or decrease in the engine rotation speed.
・In a device that turns off, expands and contracts, and changes the angle of the swash plate of the HST type transmission to control the speed according to the load, the work equipment attached to the agricultural tractor replaces the rotary tillage device with a plow. The speed ranges normally used are very different, and even though the load is light,
It is not possible to use a rotary tiller at the speed of a plow; on the other hand, if you reduce the pulling speed of the plow to the working speed of the rotary tiller just because the load is large, the work efficiency will decrease and you will not be satisfied. It cannot be said that load control is being implemented.

The object of the present invention is to set a control speed range for load control for each work state, in which each work machine has its own work speed range, and beyond which the speed will not become either high or low. be.

This is designed to prevent automatic gear shifting from occurring over a too wide range, reducing work efficiency, or shifting to a higher speed than expected, which could cause a runaway tractor accident.

(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.

The swash plate of the hydraulic pump of the HST type transmission is configured so that it cannot be rotated by an operating cylinder, and the expansion and contraction of the operating cylinder is further configured to be controllable by a solenoid valve for automatic control, during automatic load control. , the movement range of the operation cylinder for operating the swash plate is set by selecting a work state using a work setting switch.

(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 a hydraulically driven tractor of the present invention, and FIG. 2 is a control operation diagram showing working speed and opening/closing states of a group of solenoid valves.

The hydraulic circuit configuration of the present invention 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. A hydraulic motor 40 is driven by pressure oil discharged from the hydraulic pump 39.

Further, the pressure oil discharged by the auxiliary hydraulic pump 53 is passed through the relief valve 54 to the pressure oil boat a of the hydraulic control valve V.
It is sending oil to. Further, pressure oil from an engine-mounted pump 43 that discharges another high-pressure oil is also sent to the pressure oil boat via the electromagnetic valve S6.

The solenoid valve S6 is opened 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. It is linked to stepping. Even if the main clutch device 55 is disconnected, the swash plate 39a can be operated using the pressure oil from the engine-mounted pump 43, which is discharging pressure oil.

The engine-mounted pump 43 normally raises and lowers a working machine mounted on a tractor and supplies pressure oil for power steering.

With this configuration, when the main clutch device 55 is disengaged,
Although the hydraulic pump shaft 7 does not rotate and the auxiliary hydraulic pump 53 does not discharge pressure oil, the swash plate 39a of the hydraulic pump 39 can be rotated by the pressure oil from the engine-mounted pump 43.

Furthermore, since the engine-mounted pump 43 is a high-pressure pump fixed to the engine E, high-pressure oil is introduced, the swash plate 39a can be operated at high speed, and emergencies can be dealt with quickly and safely. The solenoid valve S6 is opened and closed in conjunction with the depression of the tractor's main clutch pedal 57. Normally, when the main clutch device 55 is connected, the solenoid valve S6 is closed and the auxiliary hydraulic pressure is The operating cylinder 〇 is operated only by the pressure oil from the pump 53.

In this embodiment, the S
5 sets of solenoid valves of 85 are installed from l, and the oil passage to hydraulic control valve ■ is cut off by solenoid valve S1, and 85
The four sets of solenoid valves control the supply and stop of pressurized oil to the operating cylinder 〇.

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 S2 to 85 are operated by electric signals only during automatic gear shift adjustment.

That is, in the case of automatic transmission control, pressure oil is transferred to the hydraulic control valve V.
The solenoid valve S1 that was sending pressure to the thin side of the operating cylinder C is closed, the hydraulic control valve ■ no longer operates, and the solenoid valve S3 opens and closes the pressure oil to the thin 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 〇 is controlled by separate solenoid valves S4 and 85.

That is, the opening and closing of the solenoid valve S3 and the opening and closing of the solenoid valve S4 are performed at the same time, and the opening and closing of the solenoid valve S2 and the opening and closing of the solenoid valve S5 are performed at the same time, thereby smoothly expanding and contracting the operating cylinder.

In addition, in this embodiment, the solenoid valves S4 and S5, which open and close the drain circuit on the return oil side of the operating cylinder C during automatic control, can be opened and closed intermittently by pulses, so that the operating cylinder C can be moved. Slow speed, swash plate 3
The rotating speed of 9a can be adjusted to change the feeling of shifting.

Next, the control will be explained using the control state diagram shown in FIG.

Various signals are sent to a feed bank signal and a controller M that compares and calculates 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.

In addition, a work setting switch 61 for selecting the work state desired by the operator can be used to select "rotary tilling slow" or "rotary tilling slow".
You can choose between "fast rotary plowing", "slow plowing", "fast plowing", and "plow". Depending on the working conditions of these R1 to R5, the rotation angle of the swash plate 39a of the hydraulic pump 39, that is, the maximum traveling speed, is set from β1 to R5. In contrast, the current swash plate 39
The rotation angle of a is input as β from the detection device 42. 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 "ON" state of the solenoid valve, and 0 indicates the [0FFJ state] of the solenoid valve.

In "standby" mode, all solenoid valves for automatic control are "closed".
The solenoid valve S1 for automatic/manual switching is "open", and the speed can be changed by the speed change lever 9. In the "auto" mode, the solenoid valve S1 for manual/automatic switching closes and becomes "auto", and there are three positions: "increase speed", "hold", and "decelerate", and in "increase speed", solenoid valves S3 and 84 opens, solenoid valves S2, S3, S4, and S5 close in "hold" mode, and solenoid valves S2 and 85 open in "deceleration" mode.

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 set values from R1 to R5 are determined, and the angle of the swash plate 39a is determined to reach these values. 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.

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.

Further, the operation cylinder 〇 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 rotating shaft 10 of the swash plate 39a of the hydraulic pump 39. That is, a swash plate rotation arm 37 is fixed to the right end of the swash plate rotation shaft 10, and the tip of a piston 36 is fixed to the swash plate rotation arm 37.

Also, let me explain the configuration of the hydraulic control valve ■.

The operation spool 26 and the feedback spool 27 constitute a double-structured spool within the valve case.
The operating spool 26 is slid by the rotation of the speed change lever 9, and is switched from a neutral position to a speed increasing or decelerating position between the still stationary feed bank spool 27 and the boat. As a result, the operating cylinder C is expanded and contracted, and the swash plate rotation shaft 1 of the swash plate 39a of the hydraulic pump 39
0 rotates, this causes the feedback spool 27 of the hydraulic control valve (2) to slide in the neutral direction, returning the operating spool 26 to the neutral position. 34 and 35 ensure the holding state of the operation cylinder C, and the oblique Fi39 a
This is a check valve designed so that the speed does not change due to rotation due to external impact. Further, 41 is a detection device for detecting the set position of the speed change lever 9.

In the above configuration, the present invention provides five setting positions of the work setting switch 61: "rotary tilling slow" and "rotary tilling slow".
Rotary plowing fast, plowing slow, plowing fast, and plowing stages R1, R2, R3, R4, and R5.
Then, for each stage, the maximum steering speed β1・
R2, R3, R4, and R5 are provided. In this example, the maximum speed is determined and the minimum speed is 0.
Although not determined, a minimum speed may be determined.

That is, when the "R1" state of "rotary tilling slow" is selected, the speed selected by the automatic shift is O to β.
The speed will be between 1 and 1.

For example, from the diagram showing the relationship between the work status set by the work setting switch 61 and each speed in FIG. 4, as an example, β1
If we show the value of R5, β1 is 0°401 m/s.

Next, the control state will be explained with reference to FIG. 3, which shows the relationship between engine rotational fluctuations and shift instruction signals.

The range of rotation speeds that can achieve maximum efficiency is determined for the rotation speed of engine E, and the range is defined as a lower limit NL and an upper limit NH.
Let's decide. For example, NL is 2LOOrpm, N
H is like 2500 rpm. Then, when the rotation speed N of the engine E during work under automatic control is between NL<N<NHO, R1 is set by the work setting switch 61.
The swash plate 39a is set to steer at a set speed of 5.

Next, if N<NL, then after a certain period of time TI, it will still be N<NL.
When , the traveling speed is reduced by a constant speed Δβ. After time T1, if N<NL, the speed is further reduced by a constant speed Δβ (and this is repeated. However, the speed does not become less than 0).

On the other hand, if N > NH, increase the speed by Δβ from the set speed, observe the situation for a certain period of time T1, and then N > NH.
In the case of , the speed is increased by Δβ again, and this process is repeated. However, the maximum speed is set for R1-R5 so that the maximum speed limit of β1 to β5 is not exceeded.

Figure 5 shows 0N-OFF, speed increase, deceleration, and
FIG. 6 is a flowchart showing the holding mode portion, and FIG. 6 is a flowchart showing the relationship between the change in the rotational speed of the engine E and the speed increase signal/deceleration signal.

The load control of the present invention is performed by repeating control according to the flowchart disclosed in the drawing.

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

First, in the present invention, the optimum working speed can be set for each work machine using the work setting switch 61, so the operator does not have to set the speed for each work by himself based on his experience. This made it possible to create a tractor that is easy to use even for beginners.

Second, each work M selected by the work setting switch 61
The maximum speed range β1, R2, R3, R4, and R5 is set for each set speed of RI, R2, R3, R4, and R5, so if the load suddenly becomes lighter, you can dash at an unexpectedly high speed. This eliminates the fear of personal injury.

[Brief explanation of the drawing]

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 electromagnetic valve group, and Fig. 3 is the relationship between fluctuations in engine rotation and signals for changing gears. FIG. 4 is a diagram showing the relationship between the work status set by the work setting switch 61 and each speed, and FIG. 5 is a diagram showing ON/OFF and speed increase/deceleration/holding modes of the solenoid valve of the present invention. Flowchart FIG. 6 is a flowchart showing the relationship between the change in the rotational speed of the engine E and the speed increase signal/deceleration signal. A...HST type transmission C...Operating cylinder M...Mission case ■...Hydraulic control pulp 31, 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 applicant Yanmar Diesel Co., Ltd. agent Patent attorney Toshikazu Yano℃

Claims (1)

[Claims] The swash plate of the hydraulic pump of the HST type transmission is configured to be rotated by an operating cylinder, and the expansion and contraction of the operating cylinder is further configured to be controllable by a solenoid valve for automatic control, during automatic load control. A load control device for an agricultural tractor, characterized in that the range of movement of the operation cylinder for operating the swash plate is set by selecting a work state using a work setting switch.