JP5416419B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine such as a hydraulic excavator, and more particularly to a construction machine that enables an efficient operation of a hydraulic pump coupled to an output shaft of a prime mover.

In a construction machine such as a hydraulic excavator, a variable displacement piston pump that is directly connected to an output shaft of a prime mover supplies pressure oil according to the operating state of various hydraulic actuators during operation of the construction machine. In that case, when the load of the actuator (not limited to one) increases, the discharge side pressure of the pump increases. As the pressure rises, the absorption torque of the hydraulic pump also increases proportionally. When the maximum output torque of the prime mover is exceeded, the swash plate in the hydraulic pump is driven to reduce the discharge amount, which corresponds to the increase in the load. ing. Further, when the load on the actuator becomes small, the reverse operation is performed. In general, the characteristic of the theoretical absorption torque T _th of the hydraulic pump is expressed by the following equation (1).
T _th (Nm) = P (MPa) × V _th (ml / rev) / 2π (1)
Here, _Vth is a discharge amount per one rotation.

However, the actual absorption torque T _act is expressed by the following equation (2), that is,
T _act (Nm) = T _th / η _m (2)
Here, the mechanical efficiency η _m varies depending on the discharge pressure P, the theoretical absorption torque T _{th, the} rotational speed, the viscosity of the hydraulic oil, and the temperature, and these can be expressed in the form of an accurate equation. It is difficult and is expressed by an approximate expression.

Therefore, there is a difference between the value obtained by the calculation based on the general formula and the actual torque. Moreover, if _Vth is detected using a swash plate angle sensor of a pump or the like, a sensor or the like is often not used from the viewpoint of the cost and reliability of the detector. In that case, _Vth is calculated as a function of P. FIG. 8 is a characteristic diagram of a general variable pump that explains this situation. That is, generally, the control of the variable pump uses a hyperbolic constant torque diagram Q approximated by two tangents l1 and l2, as shown in FIG.

These two tangents are made with a spring. _Vth is determined from the pressure P based on this diagram. Since the control diagrams L1 and L2 are theoretical values, the calculation is actually performed by adding efficiency. However, since there are variations in the dimensions of the component parts during mass production, _Vth should be on the safe side in consideration of the variations. Has been decided. Therefore, there is a drawback that the difference from the actual torque is further increased.

  FIG. 6 of Patent Document 1 discloses a hydraulic servomechanism using pump self-pressure (discharge side pressure) for controlling the swash plate.

  Patent Document 2 discloses an optimum output characteristic of the engine-pump system by matching the absorption horsepower of the pump and the output horsepower of the engine to the horsepower used depending on the working environment and work characteristics of the hydraulic construction machine. In the engine-pump control method of a hydraulic construction machine to obtain the pump, the absorption torque of the pump is calculated based on the pump discharge pressure detected by the pump discharge pressure detector, and the reference horsepower and pump set inside the microcomputer A technique for performing a predetermined control operation using the absorbed horsepower and outputting the result to a horsepower adjuster is disclosed.

  Further, in Patent Document 3, in paragraph 0025, “the engine speed control device of this embodiment shown in FIG. 6 detects the absorption torque of the hydraulic pump 4 as compared with the case of the first embodiment described above. As the torque detection means, the microcomputer 12 is provided with a pressure sensor 14 for measuring the pressure of the hydraulic oil discharged from the hydraulic pump 4 and a tilt angle sensor 15 for measuring the tilt angle of the hydraulic pump 4. A point is provided that calculates an absorption torque Tp of the hydraulic pump 4 based on the measured hydraulic oil pressure P and the tilt angle of the hydraulic pump 4, and determines whether the absorption torque Tp is greater than a predetermined torque T1. 7 differs mainly in that the output characteristic data of the engine 1 shown in Fig. 7 is stored in advance by the microcomputer 12, and the other configuration is basically the same as that of the first embodiment. hand In the equation, the absorption torque Tp is calculated using the equation Tp = f (P, Q), where P is the pressure of the hydraulic oil, Q is the flow rate of the hydraulic oil, and the flow rate is the hydraulic pressure. As described in “It is proportional to the tilt angle of the pump 4”, a technique for detecting the pump discharge pressure and calculating it by a microcomputer is disclosed.

  These Patent Documents 1, 2, and 3 all use the discharge pressure of the pump as a control signal in order to control the absorption torque of the pump, and have the above-described difficulties.

  On the other hand, in order to directly detect torque by electrically measuring the torsion and strain of the shaft, it is possible to attach a strain gauge, which is a conventional technique, to the outer peripheral surface of the pump drive shaft. Since the motor rotates, a hole must be formed in the central part of the shaft, and a lead wire must be inserted through it, and an electrical signal must be taken out from the end of the shaft via the slip ring. There is a drawback that it involves an increase in costs.

  Patent Document 4 discloses that a steel beam is formed by irradiating a laser beam on the outer peripheral surface of a steel material in a ring shape to make the ring-shaped irradiated portion nonmagnetic, and in that case, a large number of rings are formed at equal intervals in the axial direction. A technique for forming a scale for position measurement in the axial direction of the surface is disclosed. In this example, the change of the magnetic field in the axial direction is detected in a non-contact manner, and therefore the detection of the twist of the shaft cannot be performed.

JP 2008-232307 A Japanese Patent Laid-Open No. 10-141110 JP 09-273183 A Japanese Patent Publication No. 06-76894

  As a result of intensive investigation and examination in view of the above points, the present inventor forms a magnetically altered portion on a part of the surface of the pump drive shaft, and rotates by detecting the magnetically altered portion in a non-contact manner. It was noticed that the torsion acting on the shaft, that is, the torque can be directly detected.

  Accordingly, an object of the present invention is to directly detect the absorption torque acting on the rotating shaft of the variable displacement piston pump coupled to the output drive shaft of the prime mover as the torque acting on the rotating shaft, thereby An object of the present invention is to provide a construction machine that controls the tilt angle position of a plate and thereby enables efficient operation.

  In order to achieve the above object, a construction machine according to the present invention is a construction machine that directly detects a torsion acting on a rotating shaft of a variable displacement piston pump coupled to a prime mover as a physical quantity corresponding to an absorption torque, thereby improving work efficiency. A magnetically altered portion formed on a part of the surface of the rotating shaft, and disposed opposite to the magnetically altered portion at a predetermined interval, and the absorption torque acting on the rotating shaft during operation of the construction machine is electrically It comprises a detection unit including a sensor that detects as a signal, and a hydraulic servo unit that controls a swash plate tilt angle position of the pump based on a signal from the detection unit.

  In this case, the hydraulic servo unit includes: a power amplifying unit that amplifies an electric signal from the detection unit; and an electromagnetic proportional solenoid that presses and displaces one end of the spool of the servo unit in response to the output of the amplifying unit. Can be.

  In this case, the magnetically altered portion can be arranged inside the casing of the pump.

  In this case, the magnetically altered portion may be formed as a ferromagnetic region on the entire circumference with a predetermined length in the axial direction of the rotating shaft.

  In this case, the magnetically altered portion can be formed as a streak-like nonmagnetic region having a predetermined width and a predetermined length in the axial direction of the rotating shaft by irradiation with a laser beam.

  Furthermore, a plurality of the streaky non-magnetic regions can be formed at equal intervals on the outer periphery of the rotating shaft.

  The sensor of the detection unit detects the presence or absence of the streak-like non-magnetic material region passing in the rotation direction of the rotation shaft as a pulse waveform, and is provided with a predetermined interval in the rotation axis direction. And a second sensor, and the detection unit detects the phase difference between the pulse waveforms of the first and second sensors and the amount of twist of the rotating shaft corresponding to the absorption torque acting on the rotating shaft. As a means for detecting as, it can be configured.

  In this case, the first sensor and the second sensor can be configured to be shifted in the circumferential direction.

According to the construction machine of the present invention as set forth in claim 1, the magnetically altered portion formed on a part of the surface of the rotary shaft of the variable displacement piston pump is disposed opposite to the magnetically altered portion with a predetermined interval. During operation of the construction machine, a detection unit including a sensor that detects an absorption torque acting on the rotating shaft as an electric signal, and a hydraulic pressure that controls a swash plate tilt angle position of the pump based on a signal from the detection unit Because it has a servo unit, the absorption torque can be detected directly and non-contact as an electrical signal, and the theoretical discharge amount _Vth can be derived from the pump discharge pressure as before, and the variation on the components can be taken into consideration. The deviation from the theoretical hyperbola due to selection / determination can be significantly reduced.

  According to the construction machine of the present invention described in claim 2, the hydraulic servo unit includes an amplifier that amplifies an electric signal from the detection unit and a spool of the servo unit in response to the output of the amplifier. Since the electromagnetic proportional solenoid that presses and displaces the one end is provided, in addition to the effect of the first aspect, the hydraulic circuit configuration of the hydraulic servo unit can be simplified. Furthermore, according to the construction machine according to the third aspect of the present invention, since the magnetically altered portion is arranged inside the casing of the pump, the axial length of the pump is longer than that of the conventional device. Never become.

  Furthermore, according to the construction machine according to the present invention as set forth in claim 4, the magnetically altered portion is formed as a ferromagnetic region on the entire circumference with a predetermined axial length of the rotating shaft. The pair of sensors arranged opposite to the ferromagnetic region can directly detect the absorption torque acting on the shaft as a change in magnetic flux in a non-contact manner and take it out as an electric signal. Ferromagnetic properties do not change with use and constitute a semi-permanent sensor.

  According to the construction machine of the present invention as set forth in claim 5, the magnetically altered portion is formed as a streaky nonmagnetic material region having a predetermined width and a predetermined length in the axial direction of the rotating shaft by irradiation with a laser beam. As a result, the pair of sensors disposed opposite to the streaky nonmagnetic material region need only detect the presence or absence of the streaky nonmagnetic material region passing in the rotation direction, and face the ferromagnetic material region. The detection structure is simpler than a pair of sensors arranged, and the streaky nonmagnetic material region only needs to be irradiated with a laser beam along the axial direction. Compared to the above, the manufacturing is simple and the film can be formed with high accuracy.

  According to the construction machine of the present invention as set forth in claim 6, a plurality of the streaky nonmagnetic material regions are formed at equal intervals on the outer periphery of the rotating shaft. The rotational speed of the rotating shaft can be calculated from the detection time interval, and thus the phase difference between the pulse waveforms from the pair of sensors can be correctly detected even when the rotational speed changes.

  According to the construction machine of the present invention as set forth in claim 7, the sensor of the detection unit detects the presence or absence of the streaky nonmagnetic material region passing in the rotation direction of the rotating shaft as a pulse waveform. The first sensor and the second sensor are arranged at a predetermined interval in the rotation axis direction, and the detection unit is configured to detect a phase difference between the pulse waveforms of the first and second sensors. Since a means for detecting the amount of twist of the rotating shaft corresponding to the absorption torque acting on the rotating shaft is provided, the distance between the first sensor and the second sensor in the axial direction can be an appropriate distance. The detection accuracy and resolution can be improved by increasing the distance, and even when the adjacent arrangement of a pair of sensors is restricted due to the presence of a bearing or the like, it can be easily handled.

  According to the construction machine of the present invention described in claim 8, since the first sensor and the second sensor are arranged to be shifted in the circumferential direction, the rotation shaft is not rotated. A given amount of torsion can be detected.

It is a figure which shows the axial direction cross section of the variable displacement type piston pump rotationally driven by a motor. It is a figure which expands and shows the part of the hydraulic servo unit SV and the power piston unit PW. It is a figure explaining the self-pressure port according to the spool position of a hydraulic servo unit, and the communication state to a power cylinder piston chamber, (a) shows the spool position of an equilibrium state, (b) exceeded setting torque (C) shows the spool position when the set torque is too low. It is a figure which shows the streaky nonmagnetic material area | region formed in the axial direction of the rotating shaft surface as other of a magnetically altered part. FIG. 4 shows a part of the streaky non-magnetic material region in which the circumferential surface of the rotating shaft shown in FIG. 4 is flattened, and FIG. 4A shows a state where a torsional moment, that is, no torque acts on the rotating shaft, b) shows a state in which a torsional moment, that is, torque is applied to the rotating shaft. It is a wave form diagram which shows the change of the magnetic flux detected as a streaky nonmagnetic material area | region passes each sensor as a pulse-like electric signal, when the rotating shaft is rotating to the direction of an arrow. It is a figure explaining the example in the case of measuring the relationship with the torque at the time of giving a twist, without rotating a rotating shaft, Comprising: (a) is the state where there is no torque, and each sensor shifts the distance d in the rotation direction. And (b) is an example in which there is torque in (a). A detection part is shown. It is a diagram which shows the characteristic of a general variable displacement pump.

  Hereinafter, examples based on the embodiment of the present invention will be described in detail with reference to FIGS. 1 to 7 of the accompanying drawings.

  FIG. 1 shows an axial sectional view of a variable displacement piston pump PM that is rotationally driven by a prime mover 10. Although the thing using a diesel engine is normally used for the motor | power_engine 10, an electric motor may be sufficient. Reference numeral 12 denotes a driving shaft of the prime mover 10, and reference numeral 12a denotes a coupling portion, which is spline-coupled to a rotating shaft (driven shaft) 14 of the pump PM. The pump PM, when functionally divided, includes a rotation mechanism including the rotation shaft 14 formed inside the casing 16 and surrounded by a front lid 16a on the left end side and a rear lid 16b on the right end side, and the rotation mechanism. And a power piston unit PW for controlling the tilt angle of the swash plate 18 and a hydraulic servo unit SV for supplying predetermined pressure oil to the power piston unit PW. .

  The details of the rotation mechanism are well known in the art, but the main part will be described here. That is, on the right side of the swash plate 18, a spline 38 is formed on the outer peripheral surface of the rotary shaft 14, and a cylinder case 40 in which a female spline that engages with the spline 38 is formed. A plurality of pistons PS are equally arranged in the cylinder case 40 so that hydraulic oil is supplied to and discharged from the oil chamber CH at the right end of each piston PS via the supply / discharge plate 108. It has become.

  The left end head portion of each piston PS is slidably fitted in the shoe 110 that is slidably in contact with the swash plate 18, so that the shoe 110 rotates together with the cylinder case 40. Reference numerals BR1 and BR2 are bearings for the rotating shaft 14.

  The swash plate 18 is coupled to rods rd1 and rd2 in which the left end head is fitted in the upper and lower portions. The right end of the lower rod rd2 is in contact with a piston RE36 slidable in a hole formed in the lid 16b, and the piston RE36 is urged to the left by a spring 36a on the right end surface. . Since the pressure oil from the self-pressure port 34, which is the discharge port of the pump PM, is supplied to the hole in which the spring 36a is disposed through the broken line passage 104, the swash plate 18 always tilts clockwise, that is, discharges. The amount is always configured to be maximum.

On the other hand, the right end portion of the upper rod rd1 is in contact with the power piston 32 slidable in the hole formed in the lid 16b, and the right end surface of the power piston 32 faces the piston chamber 30. It is urged to the left with an oil pressure corresponding to the pressure in the room.
In addition, since the cross-sectional area of the power piston 32 is larger than the cross-sectional area of the lower piston RE 36, the power piston 32 can be sufficiently controlled even at a control pressure lower than the discharge pressure.

  A hydraulic servo unit SV is mounted on the upper surface of the rear lid 16b. The hydraulic servo unit SV is provided with a passage 100 indicated by a broken line for drain, a passage 102 indicated by a broken line from the self-pressure port 34, and a passage 106 communicating with the piston chamber 30.

  A spool 22 is provided in the hydraulic servo unit SV so as to be slidable in the axial direction within the sleeve 20, and a spring 24 is disposed on the right end side of the spool 22, and always urges the spool 22 to the left. doing. The left end side of the spool 22 is pressed by the drive pin SP of the electromagnetic solenoid SL.

  The reference sign PA is a power amplifying unit that supplies driving power to the electromagnetic solenoid SL, and is supplied with necessary power via the wiring L3.

  Reference symbol S is a sensor that detects an electric torque as an absorption torque corresponding to the torsion of the rotating shaft 14 via an electrical signal L1, and reference symbol CT is a control circuit thereof. An output signal of the control circuit CT is transmitted via an electrical wire L2. To the power amplifier PA. In the present invention, the sensor S and the control circuit CT are collectively referred to as an absorption torque detection unit.

  The sensor S is disposed so as to face the magnetically altered portion MD formed on the outer peripheral surface of the rotary shaft 14 in a non-contact manner, and when the absorption torque acting on the rotary shaft 14 is generated, the magnetic S corresponding thereto is generated. A change in magnetic flux distribution and density of the altered portion MD is detected.

  An example of such a magnetically altered portion MD for electrically detecting torque acting on the rotating shaft is introduced in Japanese Patent Publication No. 2007-517205.

  There, a first current is applied to flow in a first direction along the longitudinal direction of the sensor element, and by applying a first current pulse, the sensor element has a magnetically encoded ferromagnetic material. This area is generated.

  In addition, US Pat. No. 5,052,232 discloses that a ferromagnetic layer is formed on the circumferential surface of the shaft as suitable for detecting the torque acting on the rotating shaft. In each of these, a sensor facing the ferromagnetic layer is arranged in a non-contact manner, and an electric signal corresponding to the torque is generated.

  In the present invention, the contents described in Japanese Patent Publication No. 2007-517205 and US Pat. No. 5,052,232 are cited and incorporated herein, so that an example of the magnetically altered portion MD in the present invention is such a production method. It shall be manufactured by. Therefore, description of the detailed contents is omitted.

  FIG. 2 shows an enlarged view of the hydraulic servo unit SV and the power piston unit PW.

  In the figure, reference numeral 20 a is a horizontal hole formed in the sleeve 20, and reference numeral 22 a is a small diameter portion of the spool 22.

  FIG. 3 is a diagram for explaining a communication state between the self-pressure port 34 and the piston chamber 30 according to the position of the spool 22 of the hydraulic servo unit SV. In the figure, (a) shows the spool position in an equilibrium state, (b) shows the spool position when the set torque is exceeded, and (c) shows the spool position when the set torque is too small.

  In FIG. 3, (a) shows a balance between the spool 22 and the biasing force of the spring 24 to the left corresponding to the position of the solenoid pin SP when the absorption torque TQ of the rotating shaft 14 and the set torque are in an equilibrium state. In this case, the passage 102 from the self-pressure port 34 reaches the small diameter portion 22a, but is close to the lateral hole 20a of the sleeve 20 but is not in communication therewith, so that no pressure oil is supplied to the piston chamber 30.

  On the other hand, in (b), the absorption torque TQ is generated beyond the set torque, and the solenoid pin SP is displaced to the right from the state of (a). In this state, the passage 102 from the self-pressure port 34 reaches the small diameter portion 22 a and further communicates with the lateral hole 20 a of the sleeve 20, and pressure oil is supplied to the piston chamber 30. As a result, the rod rd1 is displaced leftward by the power piston 32, and the swash plate 18 is tilted. When the absorption torque is reduced due to a decrease in the flow rate from the discharge port of the pump PM due to the tilt of the swash plate 18, the detection signal from the sensor S decreases and becomes the set torque, so that the solenoid pin SP Returns to the balanced state of (a), and communication between the lateral hole 20a and the small diameter portion 22a is prevented.

  In (c), the absorption torque is less than the set torque. Contrary to (b), the solenoid pin SP moves to the left from the position in the balanced state of (a). Retract. In this case, the small diameter portion 22a remains disconnected from the horizontal hole 20a, and the pressure oil in the piston chamber 30 passes through the small hole provided in the center portion of the spool 22 from the horizontal hole 20a via the passage 106. The spring 24 is arranged and led to a chamber 24a communicating with the drain. Accordingly, the pressure in the piston chamber 30 decreases, and as a result, the bias of the lower rod rd2 in FIG. 1 becomes dominant, and then the solenoid pin SP returns to the balance position.

  FIG. 4 shows a structure in which a ferromagnetic region is formed on the circumferential surface of the rotating shaft as the magnetically altered portion MD described in FIG. 1 (disclosed in JP-T-2007-517205 and US Pat. No. 5,052,232). Unlike other examples, a non-magnetic streak region is formed in the axial direction of the rotation axis as another example of the magnetically altered portion MD.

  4, on the surface of the rotating shaft 14, streaky magnetically altered portions MD1, MD2,... MD4 are formed in the axial direction. The number of magnetically altered portions MD may be one, but a plurality may be provided in an equidistant manner at an angle θ as described later, and as illustrated as MD4, they are on the same line and are discontinuous. There may be.

  In general, the material of the rotary shaft 14 of the pump PM is a magnetic steel material, and the magnetically altered portion MD irradiates a laser beam or the like having a relatively high energy so that the magnetically altered portion becomes a surface of the rotary shaft. It forms in the irradiation part. In this case, the irradiated region becomes a non-magnetic material from the surrounding magnetic material and generates a magnetically altered portion.

  Such a technique is disclosed in Japanese Patent Publication No. 6-76894. In Japanese Patent Publication No. 6-76894, an example in which a laser beam is irradiated in a ring shape on the outer peripheral surface of the shaft is shown in order to form a scale for detecting the position in the axial direction. A streaky non-magnetic region is formed on the directional surface.

  FIG. 5 shows some streaky nonmagnetic regions MD1 and MD2 in which the circumferential surface of the rotating shaft 14 shown in FIG. FIG. 6A shows a state where a torsional moment, that is, a torque is not acting on the rotating shaft 14, and the squares indicate the magnetic flux detection regions of the sensors S1 and S2.

  Reference symbol L is a distance between the sensors S1 and S2, and reference symbol Z is an interval between the streak-like non-magnetic regions MD1 and MD2. FIG. 2B shows a state where a torsional moment, that is, torque is applied to the rotating shaft 14.

  FIG. 6 shows that when the rotating shaft 14 rotates in the direction of arrow R, the change in magnetic flux detected when the streak-like nonmagnetic material region MD1 passes through the sensors S1 and S2 is used as a pulsed electric signal. Show. That is, in the figure, the sensor S1 detects the arrival of MD1 at time t1, the pulse waveform rises, and falls at time t3. On the other hand, in the sensor S2, when there is no torque, the waveform is the same as the pulse waveform of the sensor S1, as indicated by the chain line, but when there is torque, the waveform rises at time t2 and falls at time t4.

  In this case, the time difference T of the rise between the times t1 and t2, that is, the waveform phase difference is provided in the control circuit CT (see FIG. 1) as the number N of the clock pulses by interpolating high frequency clock pulses. It can be counted with a counter or the like. When the rotational speed of the rotary shaft 14 changes, the number N changes even with the same torque, so N is inversely proportional to the rotational speed. The rotation speed can be determined based on the time interval (t5-t1) until the next streak-like nonmagnetic material region MD2 is detected at time t5. Alternatively, it can be determined based on the waveform interval (t3-t2).

  It is considered that the torque acting on the rotating shaft 14 is not generated when the prime mover 10 and the pump PM are in operation and are stationary. However, there is a case where it is desired to test the torsional characteristics of the rotating shaft in advance before calibration or when the rotating shaft 14 is assembled to the pump PM. In such a case, that is, the torsion is applied without rotating the rotating shaft 14. An example in the case of measuring the relationship with the torque in this case is shown in FIG.

  In FIG. 7, (a) is a case where the sensors S1 and S2 are arranged with a distance d shifted in the rotation direction in the absence of torque, and between the width h in the rotation direction of the streak-like nonmagnetic material region MD1. In this example, the detection units S1a and S2a of the sensors S1 and S2 are provided. (B) shows detection part S1a, S2a in a state with a torque in (a).

  As can be seen from the above (a) and (b), in (a), when S1a = S2a, the difference is zero, but in (b), S2a> S1a, and the difference is regarded as a change in magnetic flux. It is possible to take out.

  In summary, in a hydraulic pump driven by a diesel engine in a conventional hydraulic excavator of a construction machine, the discharge pressure of the hydraulic pump is sensed by a pressure sensor, and the swash plate tilt angle of the hydraulic pump is determined according to the pressure. Alternatively, the shaft tilt angle is changed so that the absorption torque does not exceed the engine torque. In general, the tilt angle of a hydraulic pump according to pressure varies individually even with the same model. Since engine stall due to increased load is a fatal functional defect, the absorption torque of the hydraulic pump is set below the maximum output of the engine in consideration of the aforementioned variations. Could not be converted to. However, according to the present invention, the absorption torque is directly detected by an electric signal, and such a problem is solved, and all the maximum output of the engine can be converted into hydraulic energy.

  Further, when the maximum output of the engine changes due to aging or environmental conditions and the output decreases, it is necessary to reset the absorption torque of the hydraulic pump in order to avoid engine stall.

  On the other hand, in the present invention, by inputting a signal from the engine to the power amplifying unit, the absorption torque of the pump can be easily changed by a program or the like, and further, the maximum output of the engine is reduced. When the signs of engine stall appear, it is possible to easily change the absorption torque of the hydraulic pump by providing a learning function to the built-in program, thereby achieving an improvement in maintenance.

  The preferred embodiments of the present invention have been described above. However, those skilled in the art can make various modifications based on the above-described embodiments.

10 Motor 12 Drive shaft 12a Coupling portion 14 Rotating shaft 16 Casing 16a, 16b Lid 18 Swash plate 20 Sleeve 20a Side hole 22 Spool 22a Small diameter portion 24 Spring 24a Chamber 30 Piston chamber 32 Sleeve 34 Self-pressure port 36 Sleeve 36a Spring 38 Spline 40 Cylinder case 100 Drain 102 Passage 104 Passage 106 Communication passage 108 Supply / discharge plate 110 Shoe BR1, BR2 Bearing CH chamber CT Control circuit PW Power piston unit L1, L2, L3 Wiring MD Magnetic alteration part MD1, MD2, MD3, MD4 Muscle Non-magnetic region PA Power amplifier PM Variable displacement piston pumps rd1, rd2 Rod S Sensor SL Linear solenoid SP Solenoid drive pin SV Hydraulic servo unit

Claims (7)

A construction machine that directly detects a torsion acting on a rotating shaft of a variable displacement piston pump coupled to a prime mover as a physical quantity corresponding to an absorption torque to increase work efficiency,
A magnetically altered portion formed on a part of the surface of the rotating shaft;
It is opposed with a predetermined interval in the magnetic alteration unit, during the operation of the construction machine, a detection unit including a sensor for detecting the absorption torque acting on the rotary shaft as an electrical signal
The sensor of the detection unit detects the presence or absence of a ferromagnetic region as the magnetically altered portion passing through in the rotation direction of the rotation shaft as a pulse waveform, and is provided with a predetermined interval in the rotation axis direction. And a second sensor, the phase difference between the pulse waveforms of the first and second sensors is detected in the detection unit of the rotation axis corresponding to the absorption torque acting on the rotation axis. Means for detecting the torsional amount, and the first sensor and the second sensor are arranged to be shifted in the circumferential direction ;
A construction machine comprising: a hydraulic servo unit that controls a swash plate tilt angle position of the pump based on a signal from the detection unit. A construction machine that directly detects a torsion acting on a rotating shaft of a variable displacement piston pump coupled to a prime mover as a physical quantity corresponding to an absorption torque to increase work efficiency,
A magnetically altered portion formed on a part of the surface of the rotating shaft;
A detection unit including a sensor that is disposed opposite to the magnetically altered portion at a predetermined interval and that detects an absorption torque acting on the rotating shaft as an electric signal during operation of the construction machine.
The sensor of the detection unit detects the presence or absence of a streaky nonmagnetic material region as the magnetically altered portion passing in the rotation direction of the rotation axis as a pulse waveform, and provides a predetermined interval in the rotation axis direction. A first sensor and a second sensor are arranged, and the detection unit rotates a phase difference between the pulse waveforms of the first and second sensors corresponding to an absorption torque acting on the rotation shaft. Means for detecting the amount of torsion of the shaft, and the first sensor and the second sensor are arranged to be shifted in the circumferential direction ;
A construction machine comprising: a hydraulic servo unit that controls a swash plate tilt angle position of the pump based on a signal from the detection unit. The hydraulic servo unit includes a power amplifying unit that amplifies an electric signal from the detection unit, and an electromagnetic proportional solenoid that presses and displaces one end of the spool of the hydraulic servo unit in response to the output of the amplifying unit. The construction machine according to claim 1 or 2 . The construction machine according to any one of claims 1 to 3, wherein the magnetically altered portion is disposed inside a casing of the pump. Said magnetic alteration unit according to any one of claims 1, 3 or 4, characterized in that it is formed as a ferromagnetic region to the entire circumference in the axial direction by a predetermined length of said rotary shaft Construction machinery. It said magnetic alteration unit, according to claim 2, 3 or 4, characterized in that it is formed as a stripe-shaped non-magnetic region of a predetermined length in the axial direction of the rotary shaft at a predetermined width by irradiation of the laser beam The construction machine described in any one of the items. The construction machine according to claim 6 , wherein a plurality of the streaky nonmagnetic regions are formed at equal intervals on the outer periphery of the rotating shaft.

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