Transmission System

Abstract

To provide a transmission system that can transmit information in a mode other than an electric signal.SOLUTION: A transmission system comprises a pump for discharging liquid to a liquid passage, a transmission device including at least one transmitter for transmitting a transmission signal by changing a state quantity of the liquid flowing through the liquid passage, and a reception device including at least one receiver for receiving the transmission signal transmitted from the transmitter by detecting the state quantity of the liquid flowing through the liquid passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a transmission system for transmitting and receiving a transmission signal between a transmitting device and a receiving device. [Background technology]

[0002] Electric signals are used to transmit information and the like in various fields, including industrial machinery such as marine machinery and construction machinery. Electric signals are transmitted from a transmitter to a receiver by passing electricity through an electrical wiring structure such as that described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-135381 Summary of the Invention [Problem to be solved by the invention]

[0004] Electrical signals require electricity to flow through electrical wiring, making them unsuitable for use in explosion-proof areas. Furthermore, in hydraulic equipment and other devices, the number of components increases if new electrical wiring is required to transmit information. Therefore, in the aforementioned cases, it is not always desirable to install electrical wiring, and it is necessary to transmit information in a manner other than electrical signals.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a transmission system that can transmit information in a form other than an electrical signal. [Means for solving the problem]

[0006] The transmission system of the present invention comprises a pump that discharges liquid into a liquid passage, a transmitting device including at least one transmitter that transmits a transmission signal by changing the state quantity of the liquid flowing through the liquid passage, and a receiving device including at least one receiver that receives the transmission signal transmitted from the transmitter by detecting the state quantity of the liquid flowing through the liquid passage.

[0007] According to the present invention, a signal can be transmitted from a transmitter to a receiver via the liquid flowing through the liquid passage, thereby enabling information to be transmitted in a form other than an electrical signal. [Effects of the Invention]

[0008] According to the present invention, information can be transmitted in a form other than an electrical signal. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing a transmission system according to a first embodiment of the present invention. [Figure 2] 2 is a circuit diagram showing a transmitter provided in the transmission system of FIG. 1. [Figure 3] 2 is a graph showing changes over time in the hydraulic pressure in the hydraulic passage when a transmission signal is transmitted in the transmission system of FIG. 1. [Figure 4] FIG. 10 is a circuit diagram showing a transmitter provided in a transmission system according to a second embodiment of the present invention. [Figure 5] FIG. 10 is a circuit diagram showing a transmitter provided in a transmission system according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a circuit diagram showing a transmitter provided in a transmission system according to a fourth embodiment of the present invention. [Figure 7] FIG. 10 is a circuit diagram showing a transmission system according to a fifth embodiment of the present invention. [Figure 8] FIG. 10 is a circuit diagram showing a transmission system according to a sixth embodiment of the present invention. [Figure 9] FIG. 10 is a circuit diagram showing a transmission system according to a seventh embodiment of the present invention. [Figure 10]FIG. 13 is a circuit diagram showing a transmission system according to an eighth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, transmission systems 1, 1A to 1G according to first to eighth embodiments of the present invention will be described with reference to the drawings mentioned above. Note that the concept of direction used in the following description is used for convenience of explanation and does not limit the orientation of the configuration of the invention to that direction. Furthermore, the transmission systems 1, 1A to 1G described below are merely one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and additions, deletions, and modifications are possible within the scope of the invention.

[0011] First Embodiment The transmission system 1 is provided in industrial machinery such as marine machinery and construction machinery, as well as in machinery and equipment in various fields. The transmission system 1 transmits information and the like in the aforementioned machinery and equipment via liquids such as oil and water. More specifically, the aforementioned machinery and equipment includes hydraulic equipment 2 and a hydraulic drive unit 3 as shown in FIG. 1. The hydraulic equipment 2 operates by supplying and discharging a liquid, such as a hydraulic fluid. This enables the machinery and equipment to perform various tasks. The hydraulic equipment 2 is, for example, a hydraulic cylinder and a hydraulic motor. In this embodiment, the hydraulic equipment 2 is the hydraulic cylinder 2. The hydraulic cylinder 2 extends upon receiving a supply of hydraulic fluid, which is an example of a liquid. The hydraulic drive unit 3 extends and retracts the hydraulic cylinder 2 by supplying hydraulic fluid to the hydraulic cylinder 2. The hydraulic drive unit 3 is provided in the transmission system 1. Below, the hydraulic drive unit 3 will first be described in detail.

[0012] <Hydraulic drive unit> The hydraulic drive unit 3 includes a hydraulic pump 11, a fluid passage 12, and a directional control valve 13. The hydraulic pump 11 discharges hydraulic fluid as will be described in detail later. The hydraulic pump 11 is connected to the hydraulic equipment 2 via the fluid passage 12. The directional control valve 13 is disposed in the fluid passage 12. The directional control valve 13 controls the flow of hydraulic fluid discharged from the hydraulic pump 11 to the hydraulic cylinder 2 in response to an input command signal. That is, the hydraulic drive unit 3 extends or contracts the hydraulic cylinder 2 by controlling the flow of hydraulic fluid with the directional control valve 13. In this embodiment, the directional control valve 13 is a normally closed shutoff valve. However, the directional control valve 13 is not limited to a shutoff valve. The directional control valve 13 may be a directional control valve that switches the flow direction of the hydraulic fluid to either the rod side port or the head side port of the hydraulic cylinder 2, or may be a rotary valve, etc.

[0013] <Transmission system> As described above, the transmission system 1 transmits information and the like via hydraulic fluid. More specifically, the transmission system 1 includes the hydraulic pump 11 and fluid passage 12 described above, a transmitter 14, and a receiver 15. The transmission system 1 also includes a throttle 16, a relief valve 17, and a controller 18.

[0014] The hydraulic pump 11 discharges hydraulic fluid as described above. In this embodiment, the hydraulic pump 11 is a variable displacement swash plate pump. However, the hydraulic pump 11 may also be a fixed displacement swash plate pump, bent axis pump, gear pump, piston pump, etc. In other words, the hydraulic pump 11 may be any hydraulic pump that can discharge hydraulic fluid. As described above, the hydraulic pump 11 is connected to the hydraulic cylinder 2 via the fluid passage 12 in which the directional control valve 13 is interposed.

[0015] The transmitting device 14 includes a transmitter 21. The transmitter 21 transmits a transmission signal by changing the state quantity of the hydraulic fluid flowing through the fluid passage 12. More specifically, the transmitter 21 transmits a transmission signal by changing the hydraulic pressure of the hydraulic fluid in the fluid passage 12. In this embodiment, the transmitter 21 is a shutoff type transmitter as shown in FIG. 2 and has a shutoff valve 21a. The shutoff valve 21a is interposed in the fluid passage 12. More specifically, the shutoff valve 21a is provided upstream of the directional control valve 13 in the fluid passage 12. The shutoff valve 21a is, for example, a piezoelectric actuator type valve. However, the shutoff valve 21a may also be an electromagnetic shutoff valve.

[0016] The shutoff valve 21a switches between open and closed states of the liquid passage 12 in response to an input command signal. The shutoff valve 21a changes the liquid pressure in the liquid passage 12 by switching between open and closed states of the liquid passage 12. As a result, a transmission signal corresponding to the command signal is applied to the liquid pressure in the liquid passage 12 (see the graph in FIG. 3). For example, the shutoff valve 21a reduces the liquid pressure in the liquid passage 12 by closing the liquid passage 12. In FIG. 3, the solid line represents the liquid pressure in the liquid passage 12, and the two-dot chain line represents the discharge pressure. The shutoff valve 21a then restores the liquid pressure in the liquid passage 12 by opening the liquid passage 12. This allows the transmitter 21 to apply a passive fluid digital signal to the liquid pressure in the liquid passage 12. The modulation method for the applied digital signal includes, for example, pulse density modulation. However, the modulation method for the digital signal may also include, for example, a convergence method or a gain method. The transmission signal may also be an analog signal.

[0017] The receiving device 15 has a receiver 31. The receiver 31 receives the transmission signal transmitted from the transmitter 21 by detecting the state quantity of the hydraulic fluid flowing through the fluid passage 12. More specifically, the receiver 31 receives the transmission signal by detecting the hydraulic pressure in the fluid passage 12. In this embodiment, the receiver 31 is a pressure sensor. The receiver 31 is connected to the fluid passage 12. More specifically, the receiver 31 is connected to the fluid passage 12 downstream of the shut-off valve 21a. The receiver 31 receives the transmission signal applied to the hydraulic pressure by detecting the hydraulic pressure in the fluid passage 12 downstream of the shut-off valve 21a.

[0018] In addition, in this embodiment, the receiver 31 is electrically connected to the directional control valve 13. The receiver 31 outputs a switching signal to the directional control valve 13. More specifically, the receiver 31 outputs a switching signal to the directional control valve 13 in response to the received transmission signal (see "Open" in FIG. 3).

[0019] The orifice 16, which is a signal removal section, is interposed in the fluid passage 12. More specifically, the orifice 16 is provided in the fluid passage 12 downstream of the transmitter 14 and the receiver 15 and upstream of the hydraulic cylinder 2. In this embodiment, the orifice 16 is provided between the connection point 12a with the receiver 31 and the directional control valve 13. The orifice 16 is, for example, a variable orifice. However, the orifice 16 may also be a fixed orifice. The orifice 16 throttles the flow rate of the hydraulic fluid flowing through the fluid passage 12.

[0020] The relief valve 17 is connected to the fluid passage 12. More specifically, the relief valve 17 is provided in the fluid passage 12 between the throttle 16 and the directional control valve 13. The relief valve 17 discharges the hydraulic fluid to a drain 19 when the pressure downstream of the throttle 16 in the fluid passage 12 reaches or exceeds a predetermined pressure. The relief valve 17, together with the throttle 16, removes the transmission signal applied from the hydraulic pressure in the fluid passage 12 downstream of the throttle 16.

[0021] The control device 18 is electrically connected to the transmitting device 14, and the control device 18 causes the transmitting device 14 to transmit a transmission signal. More specifically, the control device 18 is electrically connected to a transmitter 21. The control device 18 operates the transmitter 21 in accordance with a predetermined program or an operation on an operating device (not shown) (hereinafter referred to as a "program, etc."). For example, the control device 18 outputs a command signal to the shutoff valve 21a of the transmitter 21 in accordance with the program. This causes the shutoff valve 21a of the transmitter 21 to switch between connecting and blocking the fluid passage 12. Therefore, the control device 18 can apply the transmission signal to the hydraulic fluid in the fluid passage 12, as shown in FIG. 3.

[0022] <Transmission system operation> In the hydraulic drive unit 3, the directional control valve 13 is in a closed state, closing the fluid passage 12. In the closed state, the transmission system 1 sends a transmission signal, causing the directional control valve 13 to open the fluid passage 12. This activates the hydraulic cylinder 2. More specifically, the control device 18 of the transmission system 1 outputs a command signal to the shutoff valve 21a according to a program or the like. This activates the shutoff valve 21a, switching the fluid passage 12 between open and closed. Therefore, the transmission signal is applied to the hydraulic pressure in the fluid passage 12 downstream of the shutoff valve 21a. The transmission signal propagates through the hydraulic fluid in the fluid passage 12 and reaches the receiver 31. The receiver 31 receives the transmission signal as a fluctuation in the hydraulic pressure in the fluid passage 12. When the receiver 31 receives the transmission signal, it outputs a switching signal to the directional control valve 13. This activates the directional control valve 13, opening the fluid passage 12. This causes the hydraulic cylinder 2 to extend.

[0023] The transmission system 1 of the first embodiment includes a transmitting device 14 including a transmitter 21 that changes the hydraulic pressure of the hydraulic fluid flowing through the hydraulic passage 12, and a receiving device 15 including a receiver 31 that detects the hydraulic pressure of the hydraulic fluid flowing through the hydraulic passage 12. Therefore, a signal can be transmitted from the transmitting device 14 to the receiving device 15 via the hydraulic fluid flowing through the hydraulic passage 12. This makes it possible to transmit information in a form other than an electrical signal.

[0024] Furthermore, in the transmission system 1 of the first embodiment, the pressure of the hydraulic fluid flowing downstream of the shutoff valve 21a can be changed by shutting off the fluid passage 12 with the shutoff valve 21a, thereby enabling the shutoff type transmitter 21 to transmit a transmission signal.

[0025] In the transmission system 1 of the first embodiment, a diaphragm 16 that removes the transmission signal transmitted from the transmitter 14 is provided downstream of the receiver 15 in the liquid passage 12. This makes it possible to prevent the transmission signal transmitted from the transmitter 14 from affecting devices downstream in the liquid passage 12.

[0026] Second Embodiment The transmission system 1A of the second embodiment has a similar configuration to the transmission system 1 of the first embodiment. Therefore, the configuration of the transmission system 1A of the second embodiment will be mainly described in terms of differences from the transmission system 1 of the first embodiment, and the same components will be assigned the same reference numerals and descriptions thereof will be omitted. Similarly, the same components will be assigned the same reference numerals and descriptions thereof will be omitted for the transmission systems 1B to 1F of the third to seventh embodiments.

[0027] The transmission system 1A of the second embodiment is provided in a hydraulic drive unit 3 and includes a hydraulic pump 11, a hydraulic passage 12, a transmitting device 14A, a receiving device 15, a restrictor 16, a relief valve 17, and a control device 18. The transmitting device 14A includes a transmitter 21A as shown in FIG. 4. The transmitter 21A is a drain-type transmitter and includes a drain passage 21b and an on-off valve 21Aa. In this embodiment, the transmitter 21A further includes a resistor 21d.

[0028] The drain passage 21b branches off from the liquid passage 12 and connects the liquid passage 12 to the drain 19. More specifically, the drain passage 21b is connected to the liquid passage 12 upstream of the throttle 16. In this embodiment, the drain passage 21b is connected to the liquid passage 12 upstream of the connection point 12a. Note that the drain passage 21b may also be connected to the liquid passage 12 downstream of the connection point 12a. The drain passage 21b can discharge the working fluid in the liquid passage 12 to the drain 19.

[0029] The on-off valve 21Aa is interposed in the drain passage 21b. The on-off valve 21Aa is, for example, a piezoelectric actuator valve. However, the on-off valve 21Aa may also be an electromagnetic shut-off valve. The on-off valve 21Aa switches between discharging and discharging the working fluid from the fluid passage 12 to the drain 19 by opening and closing the drain passage 21b in response to an input command signal. This allows the hydraulic pressure in the fluid passage 12 to be changed, and a transmission signal corresponding to the command signal can be applied to the fluid passage 12. For example, the on-off valve 21Aa opens the drain passage 21b to discharge a portion of the working fluid from the fluid passage 12. This causes the on-off valve 21Aa to reduce the hydraulic pressure in the fluid passage 12. Thereafter, the on-off valve 21Aa closes the drain passage 21b to stop discharging the working fluid from the fluid passage 12. This causes the on-off valve 21Aa to restore the hydraulic pressure in the fluid passage 12. Therefore, the transmitter 21A can apply a passive fluid digital signal to the fluid pressure in the fluid passage 12.

[0030] The resistor 21d is disposed in the drain passage 21b. More specifically, the resistor 21d is disposed in the drain passage 21b closer to the drain 19 than the on-off valve 21Aa. The resistor 21d can maintain pressure in the drain passage 21b. This prevents the hydraulic pressure in the hydraulic passage 12 from decreasing excessively when the on-off valve 21Aa opens the drain passage 21b. In this embodiment, the resistor 21d is a restrictor. However, the resistor 21d may be a check valve or a relief valve, as long as it is capable of generating a predetermined hydraulic pressure in the drain passage 21b. Furthermore, the resistor 21d is not necessarily required in the transmission system 1A and may not be included.

[0031] In the transmission system 1A of the second embodiment, by opening the on-off valve 21Aa, a portion of the working fluid flowing through the fluid passage 12 can be discharged to the drain 19. This allows the pressure of the working fluid flowing through the fluid passage 12 to be changed, and therefore a transmission signal can be transmitted from the drain-type transmitter 21A.

[0032] In addition, the transmission system 1A of the second embodiment has the same effects as the transmission system 1 of the first embodiment.

[0033] Third Embodiment The transmission system 1B of the third embodiment is provided in a hydraulic drive unit 3, and includes a hydraulic pump 11, a hydraulic passage 12, a transmitting device 14B, a receiving device 15, a throttle 16, a relief valve 17, and a control device 18. The transmitting device 14B includes a transmitter 21B as shown in Fig. 5. The transmitter 21B is a pressure-source type transmitter, and includes a pressure-source passage 21Bb, a pressure hydraulic source 21e, and an on-off valve 21Ba.

[0034] The pressure source passage 21Bb is connected to the liquid passage 12 so as to branch off. More specifically, the pressure source passage 21Bb is connected to the liquid passage 12 upstream of the throttle 16. In this embodiment, the pressure source passage 21Bb is connected to the liquid passage 12 upstream of the connection point 12a. Note that the pressure source passage 21Bb may also be connected to the liquid passage 12 downstream of the connection point 12a.

[0035] The pressurized fluid source 21e is connected to the fluid passage 12 via a pressure source passage 21Bb. The pressurized fluid source 21e stores pressurized fluid and can supply pressurized fluid to the fluid passage 12 via the pressure source passage 21Bb. Here, the pressurized fluid is the same liquid as the hydraulic fluid. The pressurized fluid source 21e stores pressurized fluid at a pressure higher than the discharge pressure of the hydraulic pump 11. In this embodiment, the pressurized fluid source 21e is an accumulator. Note that the pressurized fluid source 21e may also be a hydraulic cylinder.

[0036] The on-off valve 21Ba is interposed in the pressure source passage 21Bb. More specifically, the on-off valve 21Ba is provided in the pressure source passage 21Bb closer to the fluid passage 12 than the pressure fluid source 21e. The on-off valve 21Ba is, for example, a piezoelectric actuator valve. However, the on-off valve 21Ba may also be an electromagnetic shut-off valve. The on-off valve 21Ba opens and closes the pressure source passage 21Bb in response to an input command signal. This allows the fluid pressure in the fluid passage 12 to be changed, and a transmission signal in response to the command signal can be applied to the fluid passage 12. For example, the on-off valve 21Ba opens the pressure source passage 21Bb to supply pressure fluid from the pressure fluid source 21e to the fluid passage 12. This increases the fluid pressure in the fluid passage 12. Thereafter, the on-off valve 21Ba closes the pressure source passage 21Bb to stop the supply of pressure fluid to the fluid passage 12. This reduces the fluid pressure in the fluid passage 12. This allows an active fluid digital signal to be applied to the fluid pressure in the fluid passage 12.

[0037] In the transmission system 1B of the second embodiment, by opening the pressure source passage 21Bb with the on-off valve 21Ba, the hydraulic fluid can be supplied from the pressure fluid source 21e to the fluid passage 12. This makes it possible to change the pressure of the hydraulic fluid flowing through the fluid passage 12. This makes it possible to transmit a transmission signal from the pressure source type transmitter 21B.

[0038] In addition, the transmission system 1B of the third embodiment has the same effects as the transmission system 1 of the first embodiment.

[0039] <Fourth embodiment> The transmission system 1C of the fourth embodiment is provided in a hydraulic drive unit 3, and includes a first hydraulic pump 11, a hydraulic passage 12, a transmitter 14C, a receiver 15, a throttle 16, a relief valve 17, and a control device 18. The transmitter 14C includes a transmitter 21C as shown in Fig. 6. The transmitter 21C is a supply-type transmitter, and includes a supply passage 21Cb, a second hydraulic pump 21f, and an on-off valve 21Ca.

[0040] The supply passage 21Cb is connected to the liquid passage 12 so as to branch off. More specifically, the supply passage 21Cb is connected to the liquid passage 12 upstream of the throttle 16. In this embodiment, the supply passage 21Cb is connected to the liquid passage 12 upstream of the connection point 12a. Note that the supply passage 21Cb may also be connected to the liquid passage 12 downstream of the connection point 12a.

[0041] The second hydraulic pump 21f, which is an example of a pressurized fluid supply source, is connected to the fluid passage 12 via a supply passage 21Cb. The second hydraulic pump 21f discharges hydraulic fluid. More specifically, the second hydraulic pump 21f discharges hydraulic fluid at a higher discharge pressure than the first hydraulic pump 11. The second hydraulic pump 21f supplies hydraulic fluid to the fluid passage 12 via the supply passage 21Cb. In this embodiment, the second hydraulic pump 21f is a variable displacement swash plate pump. However, the second hydraulic pump 21f may also be a fixed displacement swash plate pump, bent axis pump, gear pump, etc.

[0042] The on-off valve 21Ca, an example of a signal generator, is interposed in the supply passage 21Cb. More specifically, the on-off valve 21Ca is located in the supply passage 21Cb closer to the liquid passage 12 than the second hydraulic pressure pump 21f. The on-off valve 21Ca opens and closes the supply passage 21Cb in response to an input command signal. This allows the hydraulic pressure in the liquid passage 12 to be changed, thereby applying a transmission signal to the liquid passage 12 in response to the command signal. For example, the on-off valve 21Ca opens the supply passage 21Cb to supply hydraulic fluid from the second hydraulic pressure pump 21f to the liquid passage 12. This increases the hydraulic pressure in the liquid passage 12. Thereafter, the on-off valve 21Ca closes the supply passage 21Cb to stop the supply of pressurized fluid to the liquid passage 12. This returns the hydraulic pressure in the liquid passage 12 to its original state. This allows an active-type fluid digital signal to be applied to the hydraulic pressure in the liquid passage 12. The on-off valve 21Ca is, for example, a piezoelectric actuator valve. However, the on-off valve 21Ca may be an electromagnetic cutoff valve.

[0043] The transmission system 1C of the fourth embodiment can change the hydraulic pressure of the hydraulic fluid flowing through the fluid passage 12 by changing the hydraulic pressure of the hydraulic fluid supplied from the second hydraulic pump 21f using the on-off valve 21Ca. This allows a transmission signal to be transmitted from the supply-type transmitter 21C.

[0044] In addition, the transmission system 1C of the fourth embodiment has the same effects as the transmission system 1 of the first embodiment.

[0045] In the transmission system 1C of the fourth embodiment, the transmitter 21C does not necessarily have to include the on-off valve 21Ca. For example, if the second hydraulic pump 21f of the transmitter 21C is a variable displacement swash plate pump, the tilt angle of the swash plate is changed by a regulator device, which is an example of a signal generator. This changes the discharge pressure of the second hydraulic pump 21f, thereby increasing the hydraulic pressure in the hydraulic passage 12. Therefore, a transmission signal can be applied to the hydraulic pressure in the hydraulic passage 12.

[0046] Fifth Embodiment A transmission system 1D of the fifth embodiment includes a hydraulic pump 11, a fluid passage 12, a transmitting device 14D, a receiving device 15, and a control device 18. The transmitting device 14D includes a transmitter 21D as shown in FIG. 7. The transmitter 21D is an actuator-type transmitter and includes an actuator 21g and a driving device 21h. The actuator 21g is, for example, a hydraulic device 2 and is connected to the hydraulic pump 11 via a fluid passage 12. The actuator 21g is driven by hydraulic fluid supplied from the hydraulic pump 11. The actuator 21g can vary the hydraulic pressure in the fluid passage 12 by operating it. Note that the actuator 21g does not necessarily have to be the same as the hydraulic device 2, and may be another hydraulic device, a piezoelectric element, or the like.

[0047] The drive unit 21h is connected to the actuator 21g. The drive unit 21h is also electrically connected to the control unit 18. The drive unit 21h operates the actuator 21g in response to a command signal output from the first control unit 18. For example, if the actuator 21g is a hydraulic cylinder, the drive unit 21h extends or contracts the actuator 21g in response to the command signal output from the first control unit 18. This allows the hydraulic pressure in the fluid passage 12 to fluctuate, and a transmission signal in response to the command signal can be applied to the fluid passage 12. In this embodiment, the drive unit 21h is a linear actuator. However, the drive unit 21h may be another hydraulic cylinder, an air cylinder, or the like. In other words, the drive unit 21h may be any device that can drive the actuator 21g.

[0048] <Transmission system operation> In the transmission system 1D, the control device 18 outputs a command signal to the drive device 21h in response to the information transmitted. The drive device 21h then operates the actuator 21g in response to the command signal. In this embodiment, the drive device 21h expands or contracts the actuator 21g in response to the command signal. This causes the hydraulic pressure in the hydraulic passage 12 to oscillate, and a transmission signal in response to the command signal is applied to the hydraulic pressure in the hydraulic passage 12. The transmission signal reaches the receiver 31 by propagating through the hydraulic fluid in the hydraulic passage 12. The receiver 31 receives the transmission signal as a fluctuation in the hydraulic pressure in the hydraulic passage 12. This allows the above-mentioned information to be transmitted to the receiver 31. Note that in the transmission system 1D, the transmission signal can be transmitted from the actuator 21g whether the actuator 21g is being operated by the hydraulic pump 11 or is stopped.

[0049] The transmission system 1D of the fifth embodiment can transmit a transmission signal by changing the pressure of the hydraulic fluid in the fluid passage 12 using the actuator 21g.

[0050] In addition, the transmission system 1D of the fifth embodiment has the same effects as the transmission system 1 of the first embodiment.

[0051] Sixth Embodiment A transmission system 1E of the sixth embodiment is provided with a hydraulic drive unit 3, and as shown in Fig. 8, includes a hydraulic pump 11, a fluid passage 12, a transmitter 14E, a receiver 15, a throttle 16, a relief valve 17, and a control device 20. For ease of explanation, the throttle 16 and the relief valve 17 are omitted from Fig. 8. Similarly, the throttle 16 and the relief valve 17 are omitted from transmission systems 1F and 1G of seventh and eighth embodiments, which will be described later.

[0052] As described above, the hydraulic pump 11 is a variable displacement pump and includes a regulator device 11a. The regulator device 11a changes the discharge capacity of the hydraulic pump 11 in response to an input capacity signal. More specifically, as described above, the hydraulic pump 11 is a swash plate pump, and the regulator device 11a changes the tilt angle of the swash plate 11b of the hydraulic pump 11 in response to the capacity signal. This changes the discharge capacity of the hydraulic pump 11.

[0053] The transmitting device 14E includes a transmitter 21A similar to the transmitting device 14A of the second embodiment. The transmitter 21A is a drain-type transmitter and includes a drain passage 21b, an on-off valve 21Aa, and a resistor 21d. In the transmitting device 14E, the drain passage 21b is provided in the liquid passage 12 downstream of the receiving device 15 and upstream of the throttle 16.

[0054] The transmission system 1E also includes a pressure sensor 41, a position sensor 42, and a signal generator 43. The pressure sensor 41 detects the hydraulic pressure of the hydraulic cylinder 2. The position sensor 42 detects the position of the rod 2a of the hydraulic cylinder 2. The signal generator 43 is electrically connected to the pressure sensor 41 and the position sensor 42. The signal generator 43 generates a command signal based on detection results including the cylinder pressure detected by the pressure sensor 41 and the rod position detected by the position sensor 42. The signal generator 43 then outputs the generated command signal to the on-off valve 21Aa. As a result, a transmission signal indicating the cylinder pressure and the rod position is applied to the hydraulic pressure in the hydraulic passage 12 by the transmitter 21A. Note that in this embodiment as well, the hydraulic cylinder 2 is merely one example of the hydraulic device 2, and the hydraulic device 2 may be another device such as a hydraulic motor.

[0055] The control device 20 is electrically connected to the receiver 31 of the receiving device 15. The control device 20 controls the discharge capacity of the hydraulic pump 11 based on the transmission signal received by the receiver 31 of the receiving device 15. More specifically, the control device 20 acquires the cylinder pressure and rod position of the hydraulic cylinder 2 based on the transmission signal. The control device 20 also compares the acquired cylinder pressure and rod position with the cylinder pressure and rod position obtained, for example, based on a program. The control device 20 then outputs a capacity signal to the regulator device 11a based on the comparison result, thereby changing the discharge capacity of the hydraulic pump 11. This controls the cylinder pressure, rod position, etc. of the hydraulic cylinder 2 to desired values. The control device 20 can also display the acquired cylinder pressure and rod position on a display device (not shown).

[0056] In the transmission system 1 of the sixth embodiment, status values ​​(e.g., cylinder pressure and rod position) detected in the hydraulic cylinder 2 can be transmitted from the transmitting device 14 to the receiving device 15 by a transmission signal. Then, the operation of the hydraulic pump 11 can be controlled based on the transmitted status values. Therefore, the hydraulic pump 11 can be controlled by transmitting information in a form other than an electrical signal.

[0057] In addition, the transmission system 1E of the sixth embodiment has the same effects as the transmission system 1 of the first embodiment.

[0058] Seventh Embodiment A transmission system 1F of the seventh embodiment is provided with a hydraulic drive unit 3F, and as shown in FIG. 9, includes a hydraulic pump 11, a fluid passage 12, a transmitter 14, a receiver 15F, a throttle 16, a relief valve 17, and a control unit 18. The hydraulic drive unit 3F is connected to multiple hydraulic cylinders 2. In this embodiment, the hydraulic drive unit 3F is connected to three hydraulic cylinders 4-6. However, the hydraulic drive unit 3F may be connected to two or four or more hydraulic cylinders, and may be connected to hydraulic equipment other than the hydraulic cylinders 4-6. More specifically, the hydraulic drive unit 3F includes a hydraulic pump 11, a fluid passage 12F, and multiple directional control valves 25-27.

[0059] The fluid passage 12F is connected to the three hydraulic cylinders 4-6 in parallel with one another. That is, the fluid passage 12F includes a plurality of branch passages (three branch passages in this embodiment) 12b-12d. The hydraulic cylinders 4-6 are connected to the branch passages 12b-12d, respectively. A plurality of directional control valves 25-27 are interposed in the branch passages 12b-12d, respectively, corresponding to the hydraulic cylinders 4-6. Each of the plurality of directional control valves 25-27 is configured similarly to the directional control valve 13 in other embodiments, and controls the flow of hydraulic fluid to the corresponding hydraulic cylinders 4-6.

[0060] The receiving device 15F includes a plurality of receivers 32-34. Each of the plurality of receivers 32-34 is associated with a respective one of the plurality of directional control valves 25-27. In this embodiment, the receiving device 15F includes three receivers 32-34, the same number as the number of directional control valves 25-27. The three receivers 32-34 are respectively connected to the liquid passage 12F. More specifically, the three receivers 32-34 are respectively connected to branch passages 12b-12d through which the corresponding directional control valves 25-27 are interposed. However, the three receivers 32-34 may be connected to any position in the liquid passage 12F. As described above, the receivers 32-34 are pressure sensors that receive transmission signals by detecting the hydraulic pressure of the hydraulic fluid in the liquid passage 12F.

[0061] In this embodiment, each of the receivers 32 to 34 is electrically connected to a corresponding directional control valve 25 to 27. Based on the transmitted signal, each receiver 32 to 34 outputs a switching signal to the corresponding directional control valve 25 to 27. This allows the corresponding hydraulic cylinder 4 to 6 to be operated.

[0062] The transmitting device 14 includes a transmitter 21. Note that the transmission system 1F is not limited to the transmitting device 14 and may include any of the transmitting devices 14A to 14E and a transmitting device 14G described later. The control device 18 causes the transmitter 21 of the transmitting device 14 to transmit a transmission signal. More specifically, the control device 18 causes the transmitter 21 to transmit a multiplexed transmission signal corresponding to each of the multiple receivers 32 to 34. For example, the control device 18 causes the transmitter 21 to apply a transmission signal multiplexed based on a predetermined multiplexing method to the hydraulic pressure of the fluid passage 12. The multiplexed transmission signal includes information and commands for each of the receivers 32 to 34. The control device 18 can send information and commands corresponding to each of the receivers 32 to 34 by transmitting the multiplexed transmission signal from the transmitter 21. Note that the multiplexing method may be, for example, a frequency division multiplexing method, a time division multiplexing method, a code division multiplexing method, or a wavelength division multiplexing method.

[0063] <Transmission system operation> In the transmission system 1F, the control device 18 outputs a command signal to the transmitter 21, which then applies the multiplexed transmission signal to the hydraulic pressure in the hydraulic passage 12. The three receivers 32-34 receive corresponding information and commands in the multiplexed transmission signal. For example, a case will be described in which the multiplexed transmission signal includes a command to operate the hydraulic cylinders 4 and 5 and a command to stop the hydraulic cylinder 6. In this case, two of the three receivers 32-34, the receivers 32 and 33, output a switching signal to the directional control valve 25. This allows the two hydraulic cylinders 4 and 5 to be operated.

[0064] The transmission system 1F of the seventh embodiment can transmit a transmission signal from the transmitting device 14 to a plurality of receivers 31.

[0065] In addition, the transmission system 1F has the same effects as the transmission system 1 of the first embodiment.

[0066] Eighth Embodiment A transmission system 1G of the eighth embodiment is provided in a hydraulic drive unit 3F, and as shown in Fig. 10, includes a hydraulic pump 11, a hydraulic passage 12, a transmitter 14G, a receiver 15, a throttle 16, a relief valve 17, and a control device 20. In addition, position sensors 44-46 are provided in the hydraulic cylinders 4-6, respectively, which enable the positions of the rods 4a-6a of the hydraulic cylinders 4-6 to be detected.

[0067] The transmitting device 14G has a plurality of transmitters 22-24. The plurality of transmitters 22-24 are configured similarly to, for example, the transmitter 21. The plurality of transmitters 22 may have the same configuration as any of the transmitters 21A-21C, as long as they can apply a transmission signal to the hydraulic pressure in the hydraulic passage 12 by varying the hydraulic pressure in the hydraulic passage 12. In this embodiment, the transmitting device 14G includes three transmitters 21. The three transmitters 22-24 are associated with the hydraulic cylinders 4-6, respectively. The three transmitters 22-24 are electrically connected to position sensors 44-46 of the corresponding hydraulic cylinders 4-6. The position sensors 44-46 detect the rod position. Each of the transmitters 22-24 can output an individual signal representing the rod position detected by the corresponding position sensor 44-46.

[0068] The transmitting device 14G transmits a transmission signal in which the individual signals are multiplexed using a predetermined multiplexing method. More specifically, the transmitting device 14G applies the transmission signal, which is multiplexed by, for example, each of the three transmitters 22 to 24 changing the frequency of the individual signal (frequency division multiplexing), to the hydraulic pressure in the liquid passage 12. However, the transmitting device 14G applies the transmission signal, which is multiplexed by each of the three transmitters 22 to 24 transmitting the individual signal at different timings (time division multiplexing), to the hydraulic pressure in the liquid passage 12. Alternatively, the multiplexing method may be code division multiplexing or wavelength division multiplexing.

[0069] The receiver 31 of the receiving device 15 receives the multiplexed transmission signals by detecting the hydraulic pressure in the hydraulic passage 12. The receiver 31 outputs the received transmission signals to the control device 18, which extracts each individual signal from the transmission signals. This allows the control device 18 to obtain the rod positions of each hydraulic cylinder 4-6 contained in the individual signals transmitted from each transmitter 22-23.

[0070] <Transmission system operation> In the transmission system 1G, a transmission signal obtained by multiplexing individual signals by each transmitter 22-24 from a transmitting device 14G is applied to the hydraulic pressure in the hydraulic passage 12. A receiver 31 receives the multiplexed transmission signal. Then, a control device 18 obtains individual signals from the transmission signal received by the receiver 31. The control device 18 can obtain the rod positions of each hydraulic cylinder 4-6.

[0071] The transmission system 1G of the eighth embodiment can receive transmission signals transmitted from a plurality of transmitters 21 at a receiver 31.

[0072] In addition, the transmission system 1G has the same effects as the transmission system 1 of the first embodiment.

[0073] <Other embodiments> The transmission systems 1, 1A-1G of the first to eighth embodiments do not necessarily need to be included in the hydraulic drive unit 3, but may be included in machines and equipment as stand-alone devices. Furthermore, the hydraulic pump 11 of the transmission systems 1, 1A-1G does not necessarily need to be connected to the hydraulic equipment 2. For example, the hydraulic pump 11 may be connected to a resistor, such as a throttle, check valve, or relief valve, via the fluid passage 12. That is, the hydraulic pump 11 may be connected to anything that can generate a predetermined pressure in the fluid in the fluid passage 12. Furthermore, the fluid to which the transmission systems 1, 1A-1G apply a transmission signal is not limited to hydraulic fluid. Furthermore, in the transmission systems 1, 1A-1G, the state quantity of the fluid that is changed to transmit a transmission signal is not limited to pressure, but may also be flow rate. In this case, the receivers 31-34 receive the transmission signal by detecting the flow rate. Furthermore, the transmitters 21, 21A-21C of the transmission systems 1, 1A-1G are merely examples, and any configuration that can change the hydraulic pressure in the fluid passage 12 is acceptable.

[0074] Furthermore, the directional control valve 13 of the transmission systems 1, 1A to 1G of the first to eighth embodiments may be a directional switching valve as described above. In this case, a transmission signal including a command regarding the position of the directional control valve 13 is applied to the hydraulic fluid in the fluid passage 12. This allows the directional control valve 13 to switch the flow of hydraulic fluid to the hydraulic cylinder 2, thereby allowing the hydraulic cylinder 2 to expand or contract. Furthermore, the orifice 16 may be a signal removal unit that can remove the applied transmission signal. The signal removal unit may be, for example, a signal removal space that is sufficiently larger than the cross-sectional area of ​​the fluid passage 12, or a Holm-Hertz type silencer.

[0075] Exemplary Embodiments A transmission system according to a first aspect includes a pump that discharges liquid into a liquid passage, a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage, and a receiving device including at least one receiver that receives the transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage. According to this aspect, a signal can be transmitted from the transmitting device to the receiving device via the liquid flowing through the liquid passage. This allows information to be transmitted in a form other than an electrical signal.

[0076] In a second aspect, the transmission system is the transmission system of the first aspect, wherein the transmitting device includes at least one shutoff type transmitter that is the transmitter including a shutoff valve that shuts off the liquid passage, and the receiver is connected to the liquid passage downstream of the shutoff valve. According to this aspect, by shutting off the liquid passage with the shutoff valve, it is possible to change the state quantity of the liquid flowing downstream of the shutoff valve. This allows the transmission signal to be transmitted by the shutoff type transmitter.

[0077] In a third aspect, the transmission system is the transmission system of the first or second aspect, wherein the transmitter includes at least one drain-type transmitter, the transmitter including an on-off valve that opens and closes a drain passage that branches off from the liquid passage and connects the liquid passage to a drain. According to the above aspect, by opening the on-off valve, a portion of the liquid flowing through the liquid passage can be discharged to the drain. This changes the state quantity of the liquid flowing through the liquid passage, allowing the drain-type transmitter to transmit a transmission signal.

[0078] In a fourth aspect, the transmission system is the transmission system of any one of the first to third aspects, wherein the transmitter includes at least one pressure-source transmitter, the transmitter including a pressure fluid source connected to the fluid passage via a pressure-source passage and storing pressure fluid, and an on-off valve that opens and closes the pressure-source passage. According to the above aspect, liquid can be supplied from the pressure fluid source to the fluid passage by opening the pressure-source passage with the on-off valve. This allows the quantity of state of the liquid flowing through the fluid passage to be changed. This allows a transmission signal to be transmitted from the pressure-source transmitter.

[0079] In a fifth aspect, the transmission system is the transmission system of any one of the first to fourth aspects, wherein the transmitting device includes at least one supply-type transmitter, the transmitter including a pressurized liquid supply source that supplies liquid to the liquid passage, and a signal generator that changes a state quantity of the liquid supplied from the pressurized liquid supply source. According to the above aspect, by changing the state quantity of the liquid supplied from the pressurized liquid supply source using the signal generator, it is possible to change the state quantity of the liquid flowing through the liquid passage to which it is supplied. This allows a transmission signal to be transmitted from the supply-type transmitter.

[0080] In a sixth aspect, the transmission system is the transmission system of any one of the first to fifth aspects, wherein the transmitting device has at least one actuator-type transmitter that is the transmitter including an actuator connected to the pump via the liquid passage, and the actuator is actuated to change a state quantity of the liquid in the liquid passage and transmit a transmission signal. According to the above aspect, the transmission signal can be transmitted by changing the state quantity of the liquid in the liquid passage with the actuator.

[0081] In a seventh aspect, the transmission system of any one of the first to sixth aspects further includes a signal removal unit that is provided downstream of the receiving device in the liquid passage and that removes a transmission signal transmitted from the transmitting device. According to the above aspect, the signal removal unit that removes a transmission signal transmitted from the transmitting device is provided downstream of the receiving device in the liquid passage. This makes it possible to prevent the transmission signal transmitted from the transmitting device from affecting devices downstream of the liquid passage.

[0082] In an eighth aspect of the present invention, in the transmission system of any one of the first to seventh aspects, the receiving device includes a plurality of the receivers, and the transmitting device transmits multiplexed transmission signals corresponding to each of the plurality of receivers. According to the above aspect, the transmission signal can be transmitted from the transmitting device to a plurality of receivers.

[0083] In a ninth aspect, in the transmission system of any one of the first to eighth aspects, the transmitting device has a plurality of the transmitters connected to the liquid passages, respectively, and transmits a transmission signal obtained by multiplexing individual signals transmitted from the plurality of transmitters. According to the above aspect, the transmission signals transmitted from the plurality of transmitters can be received by a receiver. [Explanation of symbols]

[0084] 1,1A~1G transmission system 11 Hydraulic pump 12,12F liquid passage 14, 14A to 14G transmitter 15,15F receiving device 19 Drain 21, 21A~21D Transmitters 21a Shut-off valve 21Aa On-off valve 21b Drain passage 21Ba On-off valve 21Bb Pressure source passage 21Ca On-off valve (signal generator) 21e Pressure fluid source 21f Second hydraulic pump (pressure fluid supply source) 21g actuator 22~24 Transmitter 31~34 Receiver

Claims

1. a pump that discharges liquid into the liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; the transmitting device has at least one shut-off type transmitter, which is the transmitter including a shut-off valve that shuts off the liquid passage; The receiver is a transmission system connected to the fluid passage downstream of the shutoff valve.

2. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; The transmission system includes at least one drain-type transmitter, the transmitter including an on-off valve that opens and closes a drain passage that branches off from the liquid passage and connects the liquid passage to a drain.

3. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; The transmission system includes at least one pressure-source type transmitter, wherein the transmitting device is a transmitter that includes a pressure fluid source that is connected to the fluid passage via a pressure source passage and stores pressure fluid, and an on-off valve that opens and closes the pressure source passage.

4. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; a transmission system, wherein the transmitting device includes at least one supply-type transmitter, the transmitter including a pressurized liquid supply source that supplies liquid to the liquid passage, and a signal generator that changes a state quantity of the liquid supplied from the pressurized liquid supply source.

5. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; a signal removal unit that is provided downstream of the receiving device in the liquid passage and that removes a transmission signal transmitted from the transmitting device;

6. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; the receiving device has a plurality of the receivers, A transmission system in which the transmitting device transmits a multiplexed transmission signal corresponding to each of the plurality of receivers.

7. A pump that discharges liquid into a liquid passage; a transmitting device including at least one transmitter that transmits a transmission signal by changing a state quantity of the liquid flowing through the liquid passage; a receiving device including at least one receiver that receives a transmission signal transmitted from the transmitter by detecting a state quantity of the liquid flowing through the liquid passage; The transmission device has a plurality of the transmitters respectively connected to the liquid passages, and transmits a transmission signal obtained by multiplexing individual signals transmitted from each of the plurality of transmitters.

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