JPH05248511A - Hydraulic traveling vehicle - Google Patents

Abstract

PURPOSE:To prevent a prime mover from overrunning, switch over transmission stage responsively, and prevent a deceleration shock at the time of switch-over. CONSTITUTION:A travel hydraulic motor 4 is driven by an oil delivered from a hydraulic pump 2 driven by a prime mover 1. The output of the travel hydraulic motor 4 is changed by a transmission 5 to obtain a travel drive force. Cross- overload relief valves 9a and 9b for setting pressure in the input and output lines of the hydraulic motor 4 are used as variable relief valves and, when they are switched over from high-speed stage to low-speed stage, the set pressure of the relief valves 9a and 9b is controlled to low pressure and, after that, the set pressure is increased gradually. After changing, much of the return oil from the hydraulic motor 4 is flown into an inlet side line at low pressure, and the flow rate of pressure oil flown into the hydraulic motor 2 is reduced. As a result, rise of speed of the hydraulic pump 2 is prevented to prevent the prime mover 1 from overrunning. Also the return line pressure of the hydraulic motor 4 is reduced to reduce a shock generated when the valves are switched over from a high speed stage to a low speed stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic traveling vehicle in which the output of a hydraulic motor is changed by a transmission to obtain a traveling driving force.

[0002]

2. Description of the Related Art There is known a hydraulic traveling vehicle in which a traveling hydraulic motor is driven by oil discharged from a hydraulic pump driven by a prime mover and the vehicle is driven by rotation of the hydraulic motor. Such a hydraulic traveling vehicle generally has a transmission that can be switched to a plurality of gears, and reduces the rotation of the hydraulic motor at a reduction ratio corresponding to the gears and transmits the reduced speed to the wheels. However, when the vehicle is running, when the gear is switched from the high gear to the low gear, that is, when the gear ratio is increased, the gear does not immediately decelerate due to the inertia of the vehicle body.
That is, the hydraulic motor is rotated at high speed. Therefore, the oil discharged from the hydraulic motor causes the hydraulic pump to rotate at a high speed, and as a result, the so-called oh-
A balun may occur.

Therefore, in the device disclosed in Japanese Patent Laid-Open No. 62-242172, in order to solve such a problem, even if a switching operation from a high speed stage to a low speed stage is performed during traveling, the switching is not immediately performed. It waits until the vehicle speed is decelerated below a preset predetermined value, and then switches the shift speed. According to this, the input shaft of the transmission is not rotated at a high speed, so that the overrun of the prime mover can be prevented.

[0004]

However, when the vehicle speed becomes lower than the predetermined value, the gear shift operation means that the gear shift is performed only after waiting for a long time or braking the vehicle. It is performed, and the responsiveness is extremely poor. There is also a problem that a deceleration shock occurs due to a difference in the reduction gear ratio when the gear is changed, and the traveling feeling deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic traveling vehicle which prevents an overrun of a prime mover, changes gears with high responsiveness, and prevents a deceleration shock at the time of change. ..

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 showing an embodiment, the present invention is driven by a hydraulic pump 2 driven by a prime mover 1 and oil discharged from the hydraulic pump 2. From the traveling hydraulic motor 4, the transmission 5 that can be switched to a plurality of shift speeds, and decelerates the rotation of the hydraulic motor 4 at a reduction ratio according to the shift speeds and transmits the wheels 7; It is applied to a hydraulic traveling vehicle equipped with a switching means 13 for switching the gear position of the transmission 5 in accordance with the command of. Valve means (9a, 9b) provided in a conduit communicating with the input / output conduits 3a, 3b of the hydraulic motor 4 for controlling the amount of oil from the hydraulic motor output-side conduit to the input-side conduit, and this valve means The variable means (10a, 10) for varying the control oil amount by
b) and at least when the switching means 13 outputs a command to switch the shift stage from the high speed stage to the low speed stage, the variable means is controlled to control the oil amount from the hydraulic motor output side pipeline to the input side pipeline. The above object is achieved by providing the control means 11 for increasing the amount of oil and thereafter gradually reducing the amount of oil. The valve means is preferably a pair of crossover load relief valves 9a, 9b provided in opposite directions to a pair of pipelines connecting the input / output pipelines 3a, 3b. In this case, the variable means is a crossover load. Relief valve 9a,
A proportional solenoid 10a for variably controlling the set pressure of 9b,
10b can be used. In such a configuration, the set pressure of the crossover load relief valves 9a and 9b is lowered at least when a command to switch the shift speed from the high speed to the low speed is output by the switching unit 13, and thereafter,
The control means 11 is configured to gradually increase the set pressure.

[0007]

When the gear shift operation member 14 commands the gear shift to increase the speed reduction ratio during traveling, the valve means is controlled to control the amount of oil from the hydraulic motor output side pipe line to the input side pipe line. Is increased, and then the amount of oil is gradually reduced. At the time of the switching, the return oil from the traveling hydraulic motor 4 flows into the input side pipe line in a low pressure state, and the flow rate of the pressure oil flowing into the hydraulic pump 2 decreases. As a result, the hydraulic pump 2
The increase in the number of revolutions of the motor is suppressed and the overrun of the prime mover is prevented. Further, since the return line pressure of the hydraulic motor 4 becomes low, the shock at the time of shifting from the high speed stage to the low speed stage can be reduced.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a hydraulic traveling vehicle according to the present invention. A variable displacement hydraulic pump 2 driven by a prime mover 1 includes a hydraulic motor 4 via a pair of main pipelines 3a and 3b.
The hydraulic motor 4 is driven by the oil discharged from the hydraulic pump 2. The rotation of the hydraulic motor 4 is transmitted to the input shaft 5a of the transmission 5, and is transmitted to the differential gear 6 via the output shaft 5b of the transmission 5. Then, the wheels 7 are rotated by the output of the differential gear 6 to drive the vehicle. Reference numeral 8 is a regulator for controlling the tilting amount (displacement volume) of the hydraulic pump 2.

Reference numerals 9a and 9b are crossover load relief valves provided in the pipes connecting the main pipes 3a and 3b, respectively, and provided in opposite directions. The set pressures of the crossover load relief valves 9a and 9b are Proportional solenoid 10
It is variable by a and 10b. The proportional solenoids 10a and 10b are controlled by the controller 11,
The higher the applied voltage P is, the higher the pressure is set.

Here, the transmission 5 of this embodiment has a reduction ratio i1.
Of the clutches 5d and 5 shown in FIG. 2 can be switched to the first speed and the speed ratio i2 (i1> i2) to the second speed.
It is performed by connecting and disconnecting e. The engagement and disengagement of the clutches 5d and 5e is controlled by the hydraulic cylinder 5c, and the hydraulic cylinder 5c is controlled by switching the direction of the oil discharged from the hydraulic pump 12 by the solenoid valve 13.

That is, when the solenoid valve 13 is switched to the A position, the hydraulic cylinder 5c extends to the left in FIG. 2, the clutch 5d is connected and the clutch 5e is disengaged to set the first speed. When the solenoid valve 13 is switched to the B position, the hydraulic cylinder 5c extends to the right in FIG. 2, the clutch 5e is connected and the clutch 5d is disengaged to set the second speed. The solenoid portion 13a of the solenoid valve 13 is, as shown in FIG.
It can be connected to the battery 15 via a speed change switch 14 provided in the driver's seat. That is, shift switch 1
4 is opened as shown, the solenoid portion 13 of the solenoid valve 13
When a is in the non-excited state, the shift speed is set to the first speed, and when the shift switch 14 is closed, the solenoid portion 13a of the solenoid valve 13 is excited and the shift speed is set to the second speed. Gear switch 14
Is also connected to the controller 11.

Next, the operation of the embodiment will be described with reference to the flowchart of FIG. 3 showing the procedure executed by the controller 11. It is assumed that the forward / reverse switching operation member (not shown) is selected to move forward, the shift switch 14 commands the second speed, and the accelerator pedal (not shown) is depressed. At this time, the hydraulic pump 2 discharges pressure oil to the conduit 3a, and the vehicle is traveling forward at the second speed.

First, in step S1, the state of the speed change switch 14 is input, and in step S2, the speed change switch 14 is input.
It is determined whether the second gear has been switched to the first gear. If denied, the routine proceeds to step S3, where the voltage P applied to the proportional solenoids 10a, 10b of the crossover load relief valves 9a, 9b is set to the maximum value, and at step S4 the voltage P is applied to the proportional solenoids 10a, 10b. To do.
Therefore, the crossover load relief valves 9a, 9b
The set pressure of is the maximum value, and sufficient traveling driving force can be obtained during second speed traveling.

When the shift switch 14 is opened in this state, the solenoid portion 13a of the solenoid valve 13 is demagnetized and the solenoid valve 13 is demagnetized.
Is in the A position as shown in FIG. 2, and the clutch 5c is in the connected state.
The clutch 5d is disengaged and the first speed is set.

At this time, step S2 is affirmative and the process proceeds to step S5. In step S5, the voltage P applied to the proportional solenoids 10a and 10b is minimized, and in step S6, the set minimum voltage P is applied to the proportional solenoids 10a and 10b. Therefore, when the gear ratio is switched from the 2nd speed to the 1st speed and decelerated, the hydraulic motor 4 is driven by the traveling load, the rotation speed thereof increases, and a large amount of pressure oil is discharged to the return conduit 3b. The crossover load relief valve 9b opens at the set low pressure, and the pressure oil in the return side pipe line 3b flows out to the input side pipe line 3a while maintaining a low pressure. Therefore, the flow rate flowing into the hydraulic pump 2 is reduced, the rotational speed of the hydraulic pump 2 does not increase so much, and the overrun of the engine 1 can be suppressed. Further, at this time, since the pressure in the return line 3b of the hydraulic motor 4 is low, the hydraulic brake does not increase, and the shock at the time of gear shift is reduced.

In FIG. 3, when step S7 is followed by step S6, it is determined whether the applied voltage P is the maximum value. If it is not the maximum value, the process proceeds to step S8 to apply the applied voltage P by a predetermined unit amount ΔP. Only, and P + ΔP is set as a new applied voltage P, and the process proceeds to step S6. Therefore, according to such a procedure, the set pressure of the crossover load relief valves 9a and 9b when shifting from the 2nd speed to the 1st speed is gradually increased, the hydraulic brake is gradually increased, and the feeling is excellent. A hydraulic traveling vehicle is obtained.

In setting the above-mentioned minimum value, 2
It is possible to experimentally determine and determine the hydraulic brake, that is, the set pressure that does not impair the feeling when the speed is switched to the first speed. Further, it is preferable that the time for returning the set pressure from the minimum value to the maximum value is determined by similarly experimenting a jerk value (jerk) that does not impair the feeling when the hydraulic brake is applied. The minimum value of the set pressure of the crossover load relief valves 9a and 9b may be set to zero.

In the above description, the example in which only the first speed and the second speed can be switched has been shown, but it is also possible to switch to a larger number of gear stages. Furthermore, although the present invention is described as a closed circuit, the present invention can be applied to an open circuit, and can also be applied to a crawler type hydraulic traveling vehicle. Further, although the pressure of the crossover load relief valve is controlled, a variable throttle may be provided in the passage communicating between the input / output pipes 3a and 3b to variably control the throttle opening area. In this case, the control is such that the aperture area of the diaphragm is increased when the second speed is switched to the first speed, and then gradually decreased. Further, in this case, it is needless to say that the pressure oil is controlled to flow only from the return line of the hydraulic motor to the suction side line.

In the configuration of the above embodiment, the speed change switch 14 functions as a speed change operation member, the solenoid valve 13 functions as a switching means, the crossover load relief valves 9a and 9b function as valve means, and the proportional solenoids 10a and 10b function as variable means. The controller 11 constitutes a control means.

[0021]

As described in detail above, according to the present invention, when the speed is changed in the direction in which the reduction ratio increases during traveling, the set pressure of the crossover load relief valve is set to a low pressure. Since much of the return oil from the hydraulic motor for use in the low pressure is made to flow into the input side pipe while keeping the pressure low, the flow rate of the pressure oil flowing into the hydraulic pump is reduced, so that the rotation speed of the hydraulic pump is prevented from rising and the overrun of the prime mover is prevented. To be prevented.
Also, since the return line pressure of the hydraulic motor becomes low, the shock at the time of shifting from the high speed stage to the low speed stage can be reduced, and the hydraulic brake force is gradually increased to give a feeling of traveling brake. Is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the overall configuration of a hydraulic traveling vehicle according to the present invention.

FIG. 2 is a diagram showing details of a speed change mechanism.

FIG. 3 is a flowchart showing a procedure for controlling the set pressure of the crossover load relief valve at the time of gear changeover: 1: prime mover 2: variable displacement hydraulic pump 4: hydraulic motor 5: transmission 7: wheels 8: regulator 9a, 9b: Crossover load relief valve 10a, 10b: Proportional solenoid 11: Controller 13: Solenoid valve 14: Shift switch

Claims (2)

[Claims] 1. A hydraulic pump driven by a prime mover, a traveling hydraulic motor driven by oil discharged from the hydraulic pump, and a plurality of shift stages, and rotation of the hydraulic motor can be switched. A hydraulic traveling vehicle comprising: a transmission that decelerates at a speed reduction ratio corresponding to the transmission to a traveling drive system; and a switching unit that switches a gear stage of the transmission according to a command from a gear shift operation member. Valve means for controlling the amount of oil from the hydraulic motor output side pipeline to the input side pipeline provided in the pipeline communicating with the input / output pipeline, and variable means for varying the control oil volume by the valve means. , A control for increasing the oil amount by controlling the variable device at least when a command for switching the shift stage from the high speed stage to the low speed stage is output by the switching unit, and then gradually decreasing the oil amount means A hydraulic traveling vehicle comprising: 2. The hydraulic traveling vehicle according to claim 1, wherein the valve means is a pair of crossover load relief valves provided in opposite directions on a pair of pipelines connecting the input / output pipelines, The varying means is a proportional solenoid that variably controls the set pressure of the crossover load relief valve, and the varying means outputs at least a command for switching the shift stage from a high speed stage to a low speed stage by the switching means. A hydraulic traveling vehicle characterized in that the set pressure of the crossover load relief valve is lowered and then the set pressure is gradually increased.