JPH056512Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention detects the high-pressure side of a pair of hydraulic circuits whose pressures change relative to each other by using the forward and backward movement of the spool, and transmits the results as an electrical signal. The present invention relates to a high voltage side detection device capable of outputting as follows.

[Prior Art] For example, as a hydraulic continuously variable transmission device used in agricultural tractors, etc., a hydraulic circuit pairs a hydraulic pump driven by an engine or the like with a hydraulic motor that operates a drive wheel. The hydraulic pump and the hydraulic motor are connected in a closed loop through the hydraulic pump and the hydraulic motor so that the speed ratio thereof can be adjusted steplessly by changing the capacity of at least one of the hydraulic pump and the hydraulic motor in accordance with the operation of the shift lever. It is known what has been done.

In many transmission devices of this type, the capacity of a hydraulic pump or the like is controlled over a wide range of positive and negative positions, thereby making it possible to continuously select whether the vehicle is moving forward, stopping, or reversing. . However, with this kind of device, when you try to stop the vehicle by operating the shift lever to the neutral position, if there is a slight positional deviation in the variable displacement control that accompanies the neutral operation, the vehicle may become unresponsive. On the contrary, it may move forward or backward slightly.
To prevent this behavior, it is necessary to detect which of the two hydraulic circuits connecting the hydraulic pump and the hydraulic motor is at high pressure, and to check the difference between the high pressure side and the low pressure side. It is conceivable to correct the neutral operation so that the pressure does not reach a value that would cause the vehicle to operate.

However, at present, there is no simple high-pressure side detection device that can be suitably used in such cases.
Therefore, conventionally, when performing the above-mentioned control, for example, a pressure sensor is provided in each of the hydraulic pressure circuits, and based on the signals from both pressure sensors, one of the hydraulic pressure circuits is set to high pressure. and whether the differential pressure between the two hydraulic pressure circuits is within an allowable range,
Based on the determination result, corrections to the neutral are made. Therefore, a plurality of high-grade pressure sensors that continuously detect pressure are required, and an electronic circuit that processes signals from the sensors and makes certain decisions is essential. Therefore, the system becomes complicated and it becomes difficult to improve reliability.

[Problems to be solved by the invention] The invention solves the above-mentioned problems, namely, it is difficult to accurately detect the high pressure side of the paired hydraulic circuits with a certain dead zone. The purpose is to simply and reliably solve the problem of the need for pressure sensors and complicated signal processing devices.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration. That is, the high pressure side detection device according to the present invention has a pair of pressure chambers each connected to a hydraulic circuit in which the pressure changes relatively, and a pressure chamber that can move back and forth in the axial direction based on the differential pressure between these two pressure chambers. A spool, a pair of locking surfaces formed on the fixed member facing each other in the axial direction, a pair of movable members movably disposed between these locking surfaces, and these movable members. a spring that is biased in a direction away from each other and brings it into elastic contact with a corresponding locking surface, and a corresponding lock provided on the spool side that locks one of the movable members when the spool attempts to operate in either direction. It is characterized by comprising a pressing surface that presses in a direction away from the surface, and a position detection means that detects when the spool advances or retreats while resisting the biasing force of the spring and outputs an electric signal. That is.

[Function] With this configuration, when the pressures of both hydraulic pressure circuits change relatively and a pressure difference occurs between the two pressure chambers connected to them, the spool is urged in the axial direction, but if the differential pressure is within a preset allowable range, the movable member cannot be actuated by the moving force of the spool, so the spool is in the neutral position. will be retained. Also, it will not leave the neutral position due to vibrations from the engine or the like.

On the other hand, if the differential pressure exceeds the allowable value, the axial moving force acting on the spool will exceed the biasing force of the spring. Therefore, the spool moves in the axial direction while pressing one of the movable members in a direction away from the locking surface. If the spool moves in any direction, an electrical signal to that effect is output from the position detection means.

Therefore, by knowing in which direction the spool is operated based on the signal, it is possible to detect which of the two hydraulic pressure circuits is on the high pressure side. Depending on whether a signal indicating that the spool has moved is output, it can be determined whether the differential pressure between the two hydraulic pressure circuits has exceeded a certain allowable range.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

The high pressure side detection device 1 of this embodiment is used, for example, by being installed between a pair of hydraulic circuits A and B connecting a variable displacement hydraulic pump and a hydraulic motor (not shown) in a closed loop. The hydraulic circuits A and B are designed to switch between high pressure side and low pressure side at any time by operating a shift lever that controls the capacity of the hydraulic pump, etc., and thereby the output shaft of the hydraulic motor changes. It is designed to rotate forward and backward.

This high-pressure side detection device 1 is for detecting the high-pressure side of the hydraulic circuits A and B whose pressures change relatively in this way.
A spool 4 is fitted inside the housing 2 so as to be slidable in the axial direction, and at one end of the housing 2 there is a first spool 4 into which hydraulic pressure is introduced to urge the spool 4 to the right in the figure. A pressure chamber 5 is formed at the other end of the housing 2, and a second pressure chamber 6 into which hydraulic pressure for biasing the spool 4 to the left is introduced.
is formed. However, these pressure chambers 5,
6 are connected to the hydraulic circuits A and B via circuit connection ports 7 and 8, respectively.

Specifically, the housing 2 includes a housing body 2a having the cylinder port 3 and a large-diameter hole 9 continuous thereto, and a lid on the large-diameter hole side opening of the housing body 2a. The body 2b is sealed liquid-tightly via a sealing material 2c. On the other hand, the spool 4 has a sliding part 4a that is slidably fitted into the cylinder port 3. One end of the sliding part 4a has a small diameter part 4b, and the other end has a medium diameter part 4b. The portions 4c are integrally provided with their axes aligned with each other. A bolt portion 4d is integrally protruded from the tip of the medium diameter portion 4c, and a cap nut 4e is screwed onto the tip of the bolt portion 4d. A spool holding mechanism 10 is provided in the large diameter hole 9 of the housing 2.

The spool holding mechanism 10 includes both the pressure chambers 5 and 6.
This is to hold the spool 4 in the neutral position when the differential pressure is within a set range (for example, within 5 kg/cm ² ). 11, 12, a pair of movable members 13, 14 freely movable between these locking surfaces 11, 12, and these movable members 1.
Spring 1 biases 3 and 14 in a direction away from each other and brings them into elastic contact with corresponding locking surfaces 11 and 12, respectively.
5 and the spool 4 provided on the spool 4 side.
When the movable member 13, 14 attempts to operate in either direction, the corresponding locking surface 11, 1
2, and pressing surfaces 16 and 17 that press in a direction away from 2. Both the locking surfaces 11 and 12
are provided facing each other in the axial direction of the spool 4, one locking surface 11 is formed on the housing body 2a, and the other locking surface 12 is formed on the lid body 2.
It is formed in b. Moreover, each movable member 1
Numerals 3 and 14 are cup-shaped parts that are slidably fitted onto the outer periphery of the bolt part 4d of the spool 4, and have flanges 13a and 14a at the open ends.
The outer surfaces of the flanges 13a, 14a are brought into contact with the locking surfaces 11, 12, and the spring 15 is brought into contact with the inner surfaces of the flanges 13a, 14a. The pressing surface 16 for pressing the one movable member 13 is formed at the tip of the medium diameter portion 4c of the spool 4, and the pressing surface 17 for pressing the other movable member 14 is formed at the tip of the medium diameter portion 4c of the spool 4. It is formed at the inner end of the cap nut 4e.

When the spool 4 moves back and forth in the axial direction against the holding force of the spool holding mechanism 10, the position detection means 18 outputs an electric signal to that effect. The position detection means 18 is
Magnet 2 fixed to the tip of small diameter portion 4b of spool 4
1, and a pair of reed switches 22 and 23 buried near the cylinder port 3 of the housing 2.
When the spool 4 moves forward and backward and the magnet 21 approaches a specific reed switch 22, 23, a signal is output from the reed switch 22, 23. It's getting old. Specifically, the magnet 21 is annular and magnetized in the axial direction of the spool 4, and is fixed from both sides by pole plates 24 and 25 made of magnetic material attached to the tip of the spool 4. . On the other hand, the pair of reed switches 22 and 23 provided in the housing 2 are ordinary switches that have magnetic tongue pieces that also serve as contacts housed in an elongated case made of a non-magnetic material, and absorb magnetism acting in the longitudinal direction. It is designed to sense this and close the contact. These reed switches 22 and 23 are connected to the magnet 2 when the spool 4 is in the neutral position.
1 is buried at a predetermined interval in the axial direction so as to be located between the reed switches 22 and 23. Note that these reed switches 22, 23
is inclined at a certain angle with respect to the axis, and is turned on only when the magnet 21 approaches extremely. Then, connect the lead wire 28 to the terminal of each reed switch 22, 23, and connect the lead wire 28 to the notch 2.
9 to the outside.

With such a configuration, if the pressures of both hydraulic pressure circuits A and B change relatively and a differential pressure occurs between the two pressure chambers 5 and 6 connected to them, the differential pressure will change. Therefore, the spool 4 is urged in the axial direction, but if the differential pressure shows a value within a preset tolerance range, that is, a value within 5 kg/cm ² , the spool 4 is forced to move. Since neither of the movable members 13, 14 can be actuated by force, the spool 4 is held in a neutral position.

On the other hand, if the differential pressure exceeds the above-mentioned allowable value, the moving force in the axial direction acting on the spool 4 will exceed the biasing force of the spring 15. Therefore, the spool 4 moves in the axial direction while pressing one of the movable members 13, 14 in a direction away from the locking surfaces 11, 12.
If the spool 4 moves in any direction, an electrical signal to that effect is output from the position detection means 18. That is, when the spool 4 is held at the neutral position, the reed switches 22 and 23 of the position detection means 18 are both in the OFF state. In this state, for example, if the hydraulic pressure in one hydraulic pressure circuit A becomes higher than the hydraulic pressure in the other hydraulic pressure circuit B by exceeding a permissible value, the spool 4 engages one movable member 13. While pressing in the direction away from the stop surface 11, it slides to the right in the figure.
As a result, the magnet 21 held on the spool 4
One of the reed switches 22 is approached, and this reed switch 22 is switched to the ON state. Conversely, when the hydraulic pressure in the other hydraulic pressure circuit B becomes higher than the hydraulic pressure in the hydraulic pressure circuit A by exceeding the allowable value, the spool 4 removes the other movable member 14 from the locking surface 12. While pressing in the direction of separation, slide to the left in the figure. As a result, the magnet 21 held on the spool 4
approaches the other reed switch 23, and this reed switch 23 is switched to the ON state.

Therefore, by knowing in which direction the spool 4 operates based on the ON/OFF signal, it is possible to detect which of the two hydraulic pressure circuits A and B is on the high pressure side. can. Then, depending on whether an ON signal indicating that the spool 4 has moved is output, it is possible to know whether the differential pressure between the two hydraulic pressure circuits A and B has exceeded a certain tolerance range. can. Therefore, with such a device, the above-mentioned demands can be met without using any precise pressure sensor or complicated signal processing device. In other words, if this is the case, if the allowable value is set to a value lower than the differential pressure required for the vehicle to start running, it will be possible to prevent the vehicle from moving slightly when the vehicle is in neutral. The reed switches 22 and 23 are turned on. Therefore, by correcting the displacement control error of the hydraulic pump or the like based on the signal, it becomes possible to reliably stop the vehicle at the neutral position. Moreover, in this case, the dead zone can be easily set by selecting the strength of the spring 15, so that control can be stabilized.

The application of the high pressure side detection device according to the present invention is as follows:
Of course, the present invention is not limited to the embodiments described above, and can be used by being incorporated into various fluid machines.

Further, the position detecting means is not limited to that of the illustrated embodiment, and may be, for example, a Hall element, an SND, or the like configured to detect the operating state of the spool.

[Effects of the invention] Since the present invention has the above-described configuration, it is possible to create a certain dead zone on the high pressure side of the paired hydraulic circuits without using any high-grade pressure sensors or complicated signal processing devices. Therefore, it is possible to provide a high-voltage side detection device that can accurately detect the high-voltage side.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing an embodiment of the present invention. 1...High pressure side detection device, 4...Spool, 5,
6... Pressure chamber, 11, 12... Locking surface, 13, 1
4...Movable member, 15...Spring, 16,1
7... Pressing surface, 18... Position detection means.

Claims (1)

[Scope of utility model registration request] A pair of pressure chambers each connected to a hydraulic circuit in which the pressure changes relatively, a spool that can move forward and backward in the axial direction due to the pressure difference between these two pressure chambers, and a fixed member facing in the axial direction. a pair of locking surfaces formed on the locking surfaces, a pair of movable members movably disposed between these locking surfaces, and corresponding locking surfaces that bias these movable members in a direction away from each other. a spring that makes elastic contact with the surface; a pressing surface that is provided on the spool side and presses one of the movable members away from the corresponding locking surface when the spool is about to operate in either direction; A high-voltage side detection device comprising: position detection means for detecting when the spool advances or retreats while resisting the biasing force of the spring and outputting an electric signal.