JPS625375Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic drive device used as a drive means for self-propelled agricultural machines such as tractors and combines, or civil engineering machines.

Conventionally, this type of hydraulic drive device has been known to be a combination of a variable displacement hydraulic pump and a constant displacement hydraulic motor to adjust the output. The structure is complicated and expensive, and the transmission efficiency is poor.
Even when the neutral position is selected, there are drawbacks such as the risk of slight movement. In order to eliminate such drawbacks, the applicant of the present invention has proposed a system for switching between a neutral position where pressure oil is cut off to the hydraulic motor, a first position where the hydraulic motor rotates in the normal direction, and a second position where the hydraulic motor rotates in the reverse direction. By using a three-position electromagnetic directional control valve and repeatedly switching the control valve between a neutral position and a first position, or between a neutral position and a second position at high speed, the hydraulic motor can be controlled. We have already developed a hydraulic drive device that can control the rotation direction of a hydraulic motor by changing the direction of pressure oil supply to the hydraulic motor, and control the rotation speed of the hydraulic motor by changing the length of time that pressure oil is supplied to the hydraulic motor. (For example, Japanese Patent Application No. 54-92746 (see Japanese Unexamined Patent Publication No. 18155/1983)). However, since this device uses a 3-position switching valve as the control valve, the spool weight is large and the inertia force is correspondingly large, so there is a certain limit to the speed of switching, and there is a certain limit to the speed of switching. There were drawbacks such as high power consumption.

The present invention has been developed in view of the above circumstances, and its purpose is to provide pressure oil supply and discharge directions to the pressure oil supply side to the hydraulic motor and the pressure oil discharge side from the hydraulic motor, respectively. 2.
A position switching valve is installed, and the hydraulic motor can be rotated forward, reverse, or rotated by selectively or repeatedly switching the two switching valves.
It is an object of the present invention to provide a hydraulic drive device that can smoothly and accurately perform stopping, control, and rotational speed control with small electric power.

Hereinafter, the present invention will be specifically explained based on drawings showing embodiments thereof. Fig. 1 shows a hydraulic circuit diagram of a hydraulic drive device according to the present invention (hereinafter referred to as the device of the present invention) together with its control system. In the figure, 1 is a constant displacement hydraulic pump, and 2 is a constant displacement hydraulic motor. ,
3 and 4 are switching valves, and the hydraulic pump 1 is connected to the hydraulic pump 1 via the switching valve 3, the hydraulic motor 2, and the switching valve 4.
A closed circuit is formed that returns to .

The switching valves 3 and 4 are both 3-port, 2-position switching type electromagnetic directional control valves, and the pump-side port 3p of the switching valve 3 on the pressure oil supply side is connected to the oil discharge port of the hydraulic pump 1, and also to the pressure oil return port. The pump side port 4p of the side switching valve 4 is connected to the oil suction port of the hydraulic pump 1, and is further connected to the motor side ports 3a, 3b of the switching valve 3 and the switching valve 4.
Of the motor side ports 4a and 4b, port 3
a, 4a are connected to each other and the hydraulic motor 2
Oil port 2a to which pressure oil should be supplied when rotating normally
On the other hand, the ports 3b and 4b are also connected to each other and are connected to an oil port 2b to which pressurized oil is to be supplied when the hydraulic motor 2 is reversed.

When the solenoid 3s is demagnetized, the switching valve 3 on the pressure oil supply side is in the first position as shown in the figure, and the ports 3p and 3b are cut off.
Also, the ports 3p and 3a are communicated with each other, and the oil outlet side of the hydraulic pump 1 is connected to the oil outlet 2a of the hydraulic motor 2.
, and when the solenoid 3s is energized, it is set to the second position, and the ports 3p and 3a are cut off, and the ports 3p and 3b are communicated, and the discharge of the hydraulic pump 1 is set to the second position. The oil port side is connected to the oil port 2b of the hydraulic motor 2.

The switching valve 4 on the pressure oil return side is also set in the first position when the solenoid 4s is demagnetized, and is set in the first position when the solenoid 4s is in the demagnetized state, and is set in the first position when the solenoid 4s is in the demagnetized state. When the solenoid 4s is connected to the oil port 2a of the hydraulic motor 2 and the solenoid 4s is energized, it is set to the second position, and the ports 4p and 4b are connected to each other, and the oil discharge port side of the hydraulic pump 1 is connected to the oil outlet side of the hydraulic pump 1. It is connected to the oil port 2a of the motor 2.

The oil passage from the oil port 2a of the hydraulic motor 2 to the port 4a of the switching valve 4, and the oil path from the oil port 2b to the port 4
It is connected to the oil passage leading to b via check valves 5a, relief valves 6, and check valves 5b, which constitute pressure oil regulating means, and via check valves 5c, relief valves 6, and check valves 5d. They are short-circuited and connected to each other to prevent load shock and cavitation of the motor.

Reference numeral 7 is a charge pump, whose oil intake port is connected to an oil tank 8, and whose oil outlet port passes through a filter 9.
It is connected to the oil suction side of the hydraulic pump 1 with a check valve 10a interposed in the middle, and is connected to the mutually connected inlet side of the two check valves 5b and 5d with a check valve 10b interposed in the middle. . 11 is charge pump 7
This is a relief valve that connects the oil outlet and the oil tank 8.

CN is a switching control section for the switching valves 3 and 4, and is composed of an oscillation circuit activated by an external signal and a drive circuit for the solenoids 3s and 4s. The signals for stop, forward rotation, and reverse rotation are each given by a single-point selection type push button switch, etc., and when a stop signal is given, the switching valves 3 and 4 are demagnetized as shown in the figure. Both are set to the first position, as shown in FIG.

When a forward rotation (or reverse rotation) signal is given, the solenoid of the switching valve 3 (or switching valve 4) remains demagnetized; 3) is repeatedly switched at high speed. Specifically, the speed change signal is the resistance value of an external resistor for determining the duty ratio of the oscillation circuit mentioned above, and by adjusting this resistance value, the constant of the oscillation circuit is changed so that the duty ratio becomes continuously variable. There is.

In the device thus constructed, when a stop signal is given, the solenoids 3s and 4s of the switching valves 3 and 4 are demagnetized, and the switching valves 3 and 4 are both set at the first position as shown in the figure. When the hydraulic pump 1 is driven, the pressure oil is directly returned to the hydraulic pump 1 from the port 3a of the switching valve 3 via the port 4a of the switching valve 4, and the hydraulic motor 2 becomes non-driven.

When a forward rotation signal is applied, the switching valve 3 maintains its demagnetized state, while the oscillation circuit of the control unit CN emits a pulse signal with a period T as shown in FIG. 2, which is applied to the drive circuit of the switching valve 4. . If the time when this pulse signal is at high level is T ₁ and the time when it is at low level is T ₀ (T ₁ + T ₀ = T), its duty ratio is given by T ₁ /T ₁ + T ₀ . The ratio is determined by the shift signal, and as a result of the solenoid 4s of the switching valve 4 being energized while this pulse signal is at a high level, the switching valve 4 has one cycle of time T, during which time T ₁ (by the shift signal) is energized. variable) in the second position. While the switching valve 4 is in the first position, pressure oil flows and the hydraulic motor 2 is not driven, as in the case of the stop described above.
While the switching valve 4 is in the second position, pressure oil flows from the oil port 2a of the hydraulic motor 2 to the oil port 2b,
is rotated forward. Therefore, the rotational speed of the hydraulic motor 2 varies depending on the duty ratio.

When a reverse rotation signal is given, the switching valve 4 maintains a demagnetized state, while a pulse signal with a duty ratio determined by the shift signal is given to the drive circuit of the switching valve 3, and the solenoid 3s of the switching valve 3 is energized. As a result, the switching valve 3 repeatedly performs switching movements between the first position and the second position. While the switching valve 3 is in the first position, pressure oil flows from the port 3a of the switching valve 3 to the port 4a of the switching valve 4, and the hydraulic motor 2 is not driven. While the switching valve 3 is in the second position, pressure oil flows from the oil port 2b to the oil port 2a of the hydraulic motor 2, and the hydraulic motor 2 is reversely rotated at a speed corresponding to the duty ratio.

Note that when an excessive load is applied while the hydraulic motor 2 is being driven, or due to elliptical rotation of the hydraulic motor 2, the hydraulic motor 2 exhibits a pumping action, and the oil ports 2a, 2b on both sides of the hydraulic motor 2 are When the oil pressure difference between the two exceeds the relief pressure of the relief valve 6, the oil is transferred from the oil port 2a side of the hydraulic motor 2 to the 2b side via the path of the check valve 5a, the relief valve 6, and the check valve 5b. Pressure oil mutually flows back from the oil port 2b side to the oil port 2a side through the paths of the check valve 5c, the relief valve 6, and the check valve 5d, so that both oil ports 2a, 2
The oil pressure between points b is averaged, and the safety of hydraulic equipment can be ensured.

Further, when the oil pressure on the oil suction side of the hydraulic pump 1 or the oil pressure on both oil ports 2a and 2b of the hydraulic motor 2 drops below a predetermined value, the pressure oil from the charge pump 7 is applied to the check valve 10a, the check valve 10b, 5b,5
Since they are replenished through d, cavitation and the like can be prevented from occurring even when negative pressure is generated, and runaway can be reliably prevented.

As described above, in the present device, the switching valve is repeatedly switched between the two positions at high speed, and the speed change is controlled by changing the ratio of the time set in the first position and the second position. Because we are planning to do
It is possible to perform speed change control without the need for special hydraulic merging and separation circuits, and it is also possible to perform forward rotation, reverse rotation, stop control of the hydraulic motor, and speed change control of the hydraulic motor on the pressure oil supply side and pressure oil return side. By making each switching valve a 2-position switching valve, it is possible to speed up the switching operation, allowing smooth gear shifting, as well as reducing the size and weight, and significantly reducing the power consumption for switching operations. Furthermore, it is installed in parallel with the hydraulic motor between the oil passages connecting the two-position switching valve on the pressure oil return side and each oil port of the hydraulic motor, and when the pressure exceeds a predetermined pressure, the pressure oil is transferred to both oil passages. Since it has a pressure oil adjustment means that short-circuits between the two oil ports, when the oil pressure of both oil ports of the hydraulic motor exceeds a predetermined value, the pressure oil is short-circuited and flows from one oil path to the other oil path, The present invention has excellent effects, such as being able to adjust the oil pressure of each oil passage, preventing damage to each hydraulic device, and increasing the safety and reliability of the device itself.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of the device according to the present invention, and FIG. 2 is a diagram of pulse signals issued from a control section in the device according to the present invention. 1... Hydraulic pump, 2... Hydraulic motor, 3, 4
...Switching valve, 5a-5b...Check valve, 6...Relief valve, CN...Control unit.

Claims (1)

[Scope of utility model registration request] a hydraulic motor, and a two-position switching valve on the pressure oil supply side that is switched between a first position for supplying hydraulic pressure to one oil port side and a second position for supplying hydraulic pressure to the other oil port side; two positions on a pressure oil return side that are switched to a first position where pressure oil is introduced from the one oil port side of the hydraulic motor and a second position where pressure oil is introduced from the other oil port side of the hydraulic motor; A switching valve is provided in parallel with the hydraulic motor between both oil passages connecting the two-position switching valve on the pressure oil return side and each oil port of the hydraulic motor, and when a predetermined pressure is exceeded, the pressure oil is switched between the two oil passages. Pressure oil regulating means for short-circuiting between oil passages, a signal for repeatedly switching one of the switching valves between its first and second positions at high speed, and changing the speed of the hydraulic motor, A hydraulic drive device comprising: a control unit that issues a signal to the switching valve to change the time ratio set between the first position and the second position.