JPH0454835B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electro-hydraulic servomechanism that drives a hydraulic pump according to the deviation between the amount of tilting of its displacement variable mechanism and the amount of operation of a control lever. Regarding a control device.

[Background of the Invention] Various working machines, such as hydraulic excavators, are equipped with a hydraulic pump, and this hydraulic pump is driven by an engine mounted on the hydraulic excavator and is controlled by a servo mechanism. Power for these engines and servomechanisms is supplied from a battery mounted on the hydraulic excavator via a starter switch. This starter switch is the first
As shown in the figure.

FIG. 1 is a front view of the starter switch. In the figure, 1 is a starter switch, and 1a is its operating knob. Starter switch 1 is in the "OFF" position, "ON" position and "START" position as shown in the figure.
It is possible to switch between three positions. Knob 1
When a is set to the "OFF" position, all power is cut off, and when the knob is switched from the "OFF" position to the "ON" position, the power to the servo mechanism and accessories (car radio, interior lights, etc.) is turned on. moreover,
When you turn knob 1a from the "ON" position to the "START" position and release your hand, the engine starts and knob 1a automatically returns to the "ON" position. In this state, the servo mechanism and accessories are The power is still on. That is, when knob 1a is in the "ON" position, the servomechanism is powered on even if the engine is running, or even if the engine is not running and the car radio is simply listening. be. Here, the servo mechanism will be explained with reference to FIGS. 2 and 3.

FIG. 2 is a system diagram of a conventional servo mechanism. In the figure, 2 is an engine, 3 is a variable displacement hydraulic pump driven by the engine 2, 3a is a displacement variable mechanism (hereinafter, this will be represented by a swash plate) that controls the discharge amount of the variable displacement hydraulic pump 3, 4 is swash plate 3
A tilt amount detector detects the tilt amount of a, and 5 is a constant displacement hydraulic pump. Reference numeral 6 denotes an operating lever for controlling the variable displacement hydraulic pump 3, and 6a indicates an operating amount detector for detecting the operating amount of the operating lever 6. 7 is the swash plate 3a
The servo cylinder 8 is a servo piston with different pressure receiving areas at both ends. The servo piston 8 is driven by pressure oil from the constant displacement hydraulic pump 5. 9 is a relief valve that defines the maximum pressure of the hydraulic circuit of the constant displacement hydraulic pump 5. 10 and 11 are electromagnetic valves that control the servo cylinder 7, respectively, and 10a and 11a are electromagnetic valves 10 and 11, respectively.
Solenoid shown. Reference numeral 12 denotes a control device which inputs the tilting signal Y detected by the tilting amount detector 4 and the operation signal X detected by the operation detector 6a, and controls the solenoid 10a, based on the deviation between both signals X and Y.
11a is output. 13 is the control device 1
2 is an arithmetic circuit, and 14 is an output circuit of the control device 12, the details of which are shown in FIG.

FIG. 3 is a block diagram of the arithmetic circuit and output circuit shown in FIG. 2. In the figure, the same parts as those shown in FIG. 2 are given the same reference numerals. Reference numeral 18 denotes an adder which inputs the operation signal X and the tilting signal Y and outputs the deviation signal ε. 19 is a comparator which inputs the deviation signal ε from the adder 18 and compares it with the set value δ; when the deviation signal ε is greater than the set value δ, its output signal Z ₁ becomes high level, and the deviation signal When ε is less than the set value δ, the output signal Z ₁ is at a low level. 20 is a comparator that compares the deviation signal ε with the set value -δ, and the deviation signal ε is the set value -δ.
When the deviation signal ε exceeds the set value -δ, _{the output signal Z 2 becomes} a high level. Adder 18, comparator 1
9 and 20 constitute an arithmetic circuit 13.

21 is a buffer amplifier, 22 is a resistor, and 23 is a transistor. When the output signal _Z1 of the comparator 19 is at a high level, the buffer amplifier 21 outputs a signal that makes the transistor 23 conductive. 11a is excited. 24 is a buffer amplifier, 25 is a resistor, 26
is a transistor, and the output signal Z ₂ of the comparator 20
When is at a high level, buffer amplifier 24 outputs a signal that makes transistor 26 conductive, and the conduction of transistor 26 energizes solenoid 10a. Buffers 21, 24, resistances 22, 2
5. Output circuit 14 by transistors 23 and 26
is configured.

Next, the operation of the above servo mechanism will be explained. When the engine 2 is operating and the variable displacement hydraulic pump 3 is driven to discharge pressure oil according to the amount of tilting of the swash plate 4, operate the control lever 6 to discharge the amount of discharge from the variable displacement hydraulic pump 3. As a result, the deviation signal ε output from the adder 18 becomes equal to or less than the set value -δ (X-Y=ε<-δ). In this case, the output signal of comparator 19
Since Z ₁ is at a low level and the output signal Z ₂ of the comparator 20 is at a high level, solenoid 10a is energized and solenoid 11a is de-energized. Then, the solenoid valve 10 becomes conductive, the solenoid valve 11 becomes closed, and the right side port of the servo cylinder 7 is connected to the constant displacement hydraulic pump 5, and the left side port is connected to the tank. As a result, the servo piston 8 moves to the left, the tilting of the swash plate 3a decreases, and the tilting signal Y
also becomes smaller, and the deviation signal ε approaches the set value -δ. When the deviation signal ε exceeds the set value -δ, the output signal Z ₂ of the comparator 20 becomes a low level, so the solenoid valve 10 returns to the cutoff state and the servo piston 8
is held in that position. That is, the swash plate 3a is tilted according to the amount of operation of the operating lever 6.

The operating lever 6 is operated in the direction of increasing the discharge amount of the variable displacement hydraulic pump 3, and the deviation signal ε output from the adder 18 is greater than or equal to the set value δ (X-Y=
When ε>δ), the output signal Z ₁ of the comparator 19 becomes high level, and the output signal Z ₂ of the comparator 20 becomes low level. Therefore, the solenoid 11a is energized, the solenoid 10a is de-energized, the solenoid valve 11 is conductive, and the solenoid valve 10 is in a cutoff state. As a result,
Both ports of the servo cylinder 7 are connected to the constant displacement hydraulic pump 5, but due to the difference in pressure receiving area, the servo piston 8 moves to the right, increasing the tilting of the swash plate 3a, and the tilting signal Y is The deviation signal ε decreases and approaches the set value δ. When the deviation signal ε becomes less than the set value δ, the output signal Z ₁ of the comparator 19 becomes a low level, and both the solenoid valves 10 and 11 are shut off, and the servo piston 8 and therefore the swash plate 3a are held in that position. .

Now, as mentioned above, the servo mechanism is operable even when the engine 2 is not running and the starter switch 1 is simply switched to the "ON" position. By the way, the tilting of the swash plate 3a is as follows.
Even if the operating lever 6 is placed in the neutral position, it may not always be in the neutral position depending on the state of the actuator and the like. Also, depending on the neutral position of the operating lever 6, the swash plate 3
Even if the lever a is in the neutral position, the operating lever 6 may be moved from the neutral position for some reason. In these cases, a deviation occurs between the operating amount of the operating lever 6 and the amount of tilting of the swash plate 3a, a deviation signal ε is output, one of the transistors 23 and 26 becomes conductive, and one of the solenoids 10a and 11a becomes conductive. will be energized. However, since the engine 2 is not being operated, no pressure oil is supplied from the constant displacement hydraulic pump 5, and therefore the servo piston 8 and the swash plate 3a remain in the same state.
Therefore, the deviation signal ε does not decrease,
A large current is continuously supplied to the transistor 23 or the transistor 26 and the solenoid 10a or the solenoid 11a. If this state is left for a long period of time, the transistors 23 and 26 will generate heat and rise to a temperature close to the junction temperature, leading to a situation where they will be destroyed. Also, the solenoid 10a,
Since the current consumption of the battery 11a is large, the potential of the battery decreases, and a situation may arise in which it becomes impossible to drive various devices that use the battery as a power source.

Furthermore, apart from these shortcomings, in the conventional device, after repairs or periodic inspections of the variable displacement hydraulic pump 3 and the control lever 6 are completed, the operation of the control lever 6 and the control device is checked, and the tilting of the swash plate 3a is carried out. In order to adjust the turning angle, it was necessary to rotate the variable displacement hydraulic pump 3. The rotational drive of the variable displacement hydraulic pump 3 for such confirmation and adjustment is different from the rotational drive during work, and may not be expected by the operator, which may pose a danger.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to prevent the destruction of transistors and decrease in battery potential, and to check and adjust the operation of the servo mechanism without rotating the variable displacement hydraulic pump. Electricity that can perform
The present invention provides a control device for a hydraulic servomechanism.

[Summary of the invention]

In order to achieve the above object, the present invention includes a rotation detection device that detects the rotation of a prime mover that drives a hydraulic pump, and switches a switching means in accordance with a detection signal of this rotation detection device. When the prime mover is rotating, the servo mechanism is actuated by the deviation signal between the operation signal of the control lever and the tilting signal of the variable displacement mechanism, and when the prime mover is stopped, the deviation signal is activated. It is characterized in that the indicating mechanism is activated by.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 4 is a system diagram of a servo mechanism according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 2 are given the same reference numerals, and explanations thereof will be omitted. 30 is a rotation detector that detects the rotation speed of the engine 2;
A rotation signal N is output in response to the rotation of the engine 2. That is, the rotation signal N indicates that the rotation speed of the engine 2 is 0.
It is at a low level when the engine 2 is rotating, and it is at a high level when the engine 2 is rotating. 31 is a control device.
32 is a switching device that is switched by the rotation signal N. The switching device 32 switches so that the arithmetic circuit 13 and the output circuit 14 are connected when the engine 2 is rotating and the rotation signal N is at a high level, and when the engine 2 is stopped and the rotation signal N is at a low level. Sometimes, the arithmetic circuit 13 and another output circuit 34 described later
Perform switching so that the two are connected. For the switching device 32, a well-known means such as a relay or a switching transistor is used. 33A and 33B are light emitting diodes driven by the power supply voltage Vc.c.; 34
is an output circuit that controls driving of the light emitting diodes 33A and 33B. The output circuit 34 is connected to the arithmetic circuit 13 by the switching device 32 when the engine 5 is stopped.

FIG. 5 is a block diagram of the control device shown in FIG. 4. In the figure, the same parts as those shown in FIGS. 3 and 4 are given the same reference numerals. 35 is a buffer amplifier which inputs the output signal _Z1 of the comparator 19 via the switching device 32, 36 is a resistor, and 37 is the comparator 2.
The buffer amplifier 38, which receives the zero output signal _Z2 via the switching device 32, is a resistor.

Next, the operation of this embodiment will be explained. engine 2
is rotating and the variable displacement hydraulic pump 3 and constant displacement hydraulic pump 5 are being driven, the rotation signal N of the rotation detector 30 is at a high level. Therefore, the switching device 32 connects the arithmetic circuit 13 to the output circuit 14, the transistors 23 and 26 of the output circuit 14 are controlled according to the deviation signal ε, and the servo mechanism operates in the same manner as before.

When the engine 2 is stopped and the variable displacement hydraulic pump 3 and constant displacement hydraulic pump 5 are not driven, the rotation signal N of the rotation detector 30 is at a low level. Therefore, the switching device 32 disconnects the arithmetic circuit 13 and the output circuit 14, and connects the arithmetic circuit 13 and the output circuit 34. In this way, since the arithmetic circuit 13 and the output circuit 14 are cut off, even if the adder 18 outputs the deviation signal ε when the engine 2 is stopped, the transistor 23 of the output circuit 14 , 26 are not electrically connected, and the solenoids 10a and 11a are not energized. As a result, the transistor 23,
26 is prevented from being destroyed, and there is no power consumption by the solenoid 10a, and a drop in battery potential is prevented.

On the other hand, by connecting the arithmetic circuit 13 and the output circuit 34, the output signals Z ₁ ,
Z ₂ can be input to the output circuit 34. Therefore,
After repairs or periodic inspections of the variable displacement hydraulic pump 3 and the operating lever 6, for example, to adjust the neutral position of the swash plate 3a, set the operating lever 6 to the neutral position and watch the light emitting diodes 32A and 32B emit light. Adjust while doing so. That is, when the swash plate 3a is not in the neutral position, a difference occurs between the tilt amount signal Y of the tilt amount detector 4 and the operation signal X of the operation amount detector 6a, and the adder 18 outputs the deviation signal ε. The light emitting diode 32A or the light emitting diode 32B emits light according to the deviation signal ε. Therefore, it is sufficient to adjust the swash plate 3a until this light emission disappears. In this adjustment, it is not necessarily necessary to adjust the swash plate 3a, and the attachment of the tilt amount detector 4 may be adjusted, or various elements within the control device 31 may be adjusted. Furthermore, the operation lever 6, the operation amount detector 6a or the control device 31, especially the arithmetic circuit 1
3. To check the operation of the output circuit 34, operate the operating lever 6. At this time, the operating lever 6
Light emitting diodes 33A, 3 corresponding to the operating direction of
If 3B emits light, it can be confirmed that these devices are working normally, and the light emitting diodes 33A and 33
If B does not emit light, it can be determined that one of the devices is malfunctioning. Adjustment of the swash plate 3a and other checks and confirmation of various devices can be carried out by stopping the engine 2 and each hydraulic motor 3, 5, thereby preventing danger to workers and the like.

In this way, in this embodiment, the switching device connects the arithmetic circuit to the output circuit for the solenoid valve when the engine is running, and connects the arithmetic circuit to the output circuit for the light emitting diode when the engine is stopped. This prevents damage to the transistor in the output circuit and a drop in battery potential due to power consumption of the solenoid valve solenoid.Furthermore, it is possible to adjust the swash plate, control lever, and check the operation of the control device using the variable displacement hydraulic pump. This can be done without rotating the constant displacement hydraulic pump, thereby preventing danger.

In the above embodiments, an example using a light emitting diode has been described, but an indicator lamp, another indicator, or a buzzer may be used instead of the light emitting diode.

〔Effect of the invention〕

As described above, in the present invention, a switching means is provided which is switched by a signal from a rotation detection device that detects the rotation of the prime mover, and when the prime mover is rotating, the servo mechanism is switched to the operable state. Since the instruction mechanism, which is activated by the deviation signal, is switched to enable operation when the variable displacement hydraulic pump is stopped, it is possible to prevent damage to the transistor and decrease in battery potential, and to rotate the variable displacement hydraulic pump. The operation of the servo mechanism can be checked and adjusted without any trouble.

[Brief explanation of the drawing]

Fig. 1 is a front view of a starter switch, Fig. 2 is a system diagram of a conventional servo mechanism, Fig. 3 is a block diagram of the control device shown in Fig. 2, and Fig. 4 is a servo mechanism according to an embodiment of the present invention. FIG. 5 is a block diagram of the control device shown in FIG. 4. 2...engine, 3...variable displacement hydraulic pump,
3a... Swash plate, 4... Tilt amount detector, 5... Fixed capacity hydraulic pump, 6... Operation lever, 6a... Operation detector, 7... Servo cylinder, 10, 11...
Solenoid valve, 13... Arithmetic circuit, 14, 34... Output circuit, 30... Rotation detector, 32... Switching device,
33A, 33B... Light emitting diode.

Claims (1)

[Claims] 1 A hydraulic pump driven by a prime mover, a variable displacement mechanism that controls the discharge amount of the hydraulic pump, an operating lever that drives the hydraulic pump, a tilting amount signal of the variable displacement mechanism, and a displacement variable mechanism that controls the displacement volume of the operating lever. A servo mechanism comprising: a drive means for driving the variable displacement mechanism based on a deviation value from an operation signal; a rotation detection device for detecting rotation of the prime mover; The electric motor is characterized by further comprising a switching means for enabling the servo mechanism to operate when rotation of the prime mover is detected by a rotation detection device and for enabling the indicating mechanism to operate when rotation of the prime mover is not detected. - Control device for hydraulic servomechanism.