JP2022148933A - Vehicle speed detection system - Google Patents

Abstract

To appropriately receive a vehicle speed signal according to a vehicle type.SOLUTION: A vehicle speed detection system 50 is one that detects speed of a vehicle, and includes: a vehicle speed signal detection circuit 52 having a receiving unit 60 connected to an output terminal 21 that outputs a vehicle speed signal according to the speed of the vehicle and a switching unit 64 that switches a connection state of the circuit; and a switching control unit 54 that controls the switching of the connection state of the circuit by the switching unit 64 according to the reception status of the vehicle speed signal of the receiving unit 60 while the vehicle is travelling and thereby enables the receiving unit 60 to receive the vehicle speed signal.SELECTED DRAWING: Figure 5

Description

The present invention relates to a vehicle speed detection system.

A technique for electronically controlling the rotation of a mixer drum of a mixer vehicle is known. For example, Patent Literature 1 describes a control system having a controller for a mixer drum and a display device connected to the controller. Patent Literature 1 describes that when a controller receives a vehicle speed signal from a vehicle speed sensor and determines that the vehicle is running, automatic stirring of the mixer drum is started.

In such a mixer vehicle, the specifications of the vehicle speed sensor differ depending on the vehicle type. The operator manually changed the dip switch.

JP 2020-168954 A

However, when manually switching the DIP switches, there is a risk that the number of man-hours required for the operator increases, or that the circuit configuration suitable for the vehicle type cannot be achieved due to operator error or the like. If the circuit configuration is not suitable for the type of vehicle, the vehicle speed signal cannot be properly received, making it impossible to determine whether the vehicle is running. Therefore, it is required to be able to appropriately switch the circuit configuration according to the vehicle type and to appropriately receive the vehicle speed signal.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vehicle speed detection system capable of appropriately receiving a vehicle speed signal according to the type of vehicle.

In order to solve the above-described problems and achieve the object, a vehicle speed detection system according to the present disclosure is a vehicle speed detection system that detects the speed of a vehicle, and includes an output terminal that outputs a vehicle speed signal corresponding to the speed of the vehicle. and a switching unit for switching the connection state of the circuit; a switching control unit that controls switching of the connection state of the circuit by the switching unit so that the receiving unit can receive the vehicle speed signal.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to receive a vehicle speed signal appropriately according to a vehicle type.

FIG. 1 is a schematic plan view of a mixer vehicle according to this embodiment. FIG. 2 is a schematic rear view of the mixer truck according to this embodiment. FIG. 3 is a block diagram showing the hardware configuration of the mixer truck according to this embodiment. FIG. 4 is a graph showing an example of a vehicle speed signal. FIG. 5 is a schematic circuit diagram of the vehicle speed detection system. FIG. 6 is a flow chart for explaining the switching processing flow of the connection state of the vehicle speed signal detection circuit.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In addition, this invention is not limited by embodiment described below.

FIG. 1 is a schematic plan view of a mixer vehicle according to this embodiment, FIG. 2 is a schematic rear view of the mixer vehicle according to this embodiment, and FIG. 3 is a mixer according to this embodiment. 1 is a block diagram showing the hardware configuration of a vehicle; FIG.

(Overall configuration of mixer truck)
Hereinafter, the overall configuration of a mixer truck 1 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. The mixer truck 1 according to the present embodiment is a vehicle for transporting so-called ready-mixed concrete such as mortar and ready-mixed concrete (hereinafter referred to as “ready-mixed concrete”) put into the mixer drum 2 . In the following description, a case where the mixer truck 1 loads ready-mixed concrete as a load will be described.

As shown in FIG. 1, the mixer drum 2 is a cylindrical container with a bottom that is rotatably mounted on a base 3, and has an opening 2a at its rear end through which ready-mixed concrete is charged and discharged. The mixer drum 2 is mounted with an inclination such that its rotational axis O gradually rises from the front to the rear of the vehicle. Inside the mixer drum 2, drum blades (not shown) are spirally arranged along the inner wall surface of the drum. will be

As shown in FIG. 2, a hopper 16 is provided in the rear upper portion of the opening 2a of the mixer drum 2. As shown in FIG. In a ready-mixed concrete factory, the ready-mixed concrete put into the mixer truck 1 is guided by the hopper 16 to the opening 2a. A flow guide 17 and a chute 18 are provided at the lower rear portion of the opening 2a of the mixer drum 2. As shown in FIG. The ready-mixed concrete discharged from the opening 2a is guided to a chute 18 by a flow guide 17 and discharged in a predetermined direction by the chute 18. As shown in FIG.

The mixer drum 2 is driven to rotate via a driving device 4 shown in FIG. The drive device 4 is a fluid pressure device that is driven by the rotation of the engine 10 and rotates the mixer drum 2 by the fluid pressure of the working fluid.

As shown in FIG. 3, the engine 10 has a throttle valve 10a for adjusting the output and speed of the engine 10. As shown in FIG. The opening degree of the throttle valve 10a is controlled by the controller 20 via an actuator (not shown) when the driving device 4 is driven by the engine 10. As shown in FIG. Further, the engine 10 is provided with a rotation sensor 10b that detects the rotational speed of the engine 10 and outputs a signal corresponding to the detected rotational speed to the controller 20 .

The rotation speed of the engine 10 when driving the driving device 4 is controlled by the controller 20 via the throttle valve 10a so that the rotation speed detected by the rotation sensor 10b becomes a predetermined magnitude. The rotation sensor 10b may detect the rotational speed of the PTO shaft 9 or the drive shaft 8, which are the input shafts of the driving device 4, or may detect the rotational speed of the hydraulic pump 5, which will be described later. may be

The rotation of the engine 10 is transmitted to the driving device 4 via a PTO shaft 9 (PTO: Power take-off), which always takes power from the engine 10, and a drive shaft 8 connecting the PTO shaft 9 and the driving device 4. be done.

The driving device 4 includes a hydraulic pump 5 that is driven by the engine 10 and discharges hydraulic oil OI as a working fluid, and a hydraulic motor 6 that is operated by the hydraulic oil OI supplied from the hydraulic pump 5 and drives the mixer drum 2 to rotate. have. In addition, in the drive device 4, other incompressible fluid may be used as the working fluid instead of the working oil OI.

The hydraulic pump 5 is a swash plate type axial piston pump whose discharge amount is changed according to the tilt angle of a swash plate (not shown). 5a, a tilt angle adjustment mechanism 5b that adjusts the discharge amount of the hydraulic pump 5 by changing the tilt angle of the swash plate, and a pressure sensor 5c that detects the pressure of the hydraulic oil OI supplied to the hydraulic motor 6. , have

The hydraulic pump 5 is rotationally driven by power constantly extracted from the engine 10 via the PTO shaft 9 . The drive source for rotationally driving the hydraulic pump 5 is not limited to the engine 10 for traveling, and may be an auxiliary engine or an electric motor that is not used for traveling.

The control valve 5a has a first position that directs the hydraulic fluid OI to the hydraulic motor 6 so as to rotate the mixer drum 2 in one direction, and a first position that directs the hydraulic fluid OI to the hydraulic motor 6 so as to rotate the mixer drum 2 in the other direction. It is a three-position switching valve having a second position and a blocking position blocking the flow of hydraulic oil OI from the hydraulic pump 5 to the hydraulic motor 6 . A controller 20 electrically controls the position of the control valve 5a.

The tilt angle adjusting mechanism 5b has a hydraulic actuator (not shown) that changes the tilt angle of the swash plate, and a solenoid valve (not shown) that controls the working oil pressure guided to the hydraulic actuator. The tilt angle adjustment mechanism 5b changes the tilt angle of the swash plate according to the magnitude of the drive current supplied from the controller 20 to the solenoid valve, and adjusts the hydraulic pump 5 according to the change in the tilt angle of the swash plate. The discharge amount is changed.

The pressure sensor 5c outputs to the controller 20 a signal corresponding to the detected pressure of the hydraulic oil OI. The pressure sensor 5c may be provided anywhere as long as it can detect the pressure of the hydraulic oil OI supplied from the hydraulic pump 5 to the hydraulic motor 6, which is the pressure of the hydraulic oil in the drive device 4. 6 may be provided.

It should be noted that the hydraulic pump 5 is not limited to the type of pump described above, and may be any type of pump as long as the pump can have a variable discharge capacity. For example, the hydraulic pump 5 may be a swash plate type axial piston pump whose discharge amount and discharge direction are changed according to the tilt angle of the swash plate. Alternatively, a fixed displacement pump with a fixed swash plate may be used. In this case, the discharge amount may be changed according to the degree of opening of a switching valve provided in the pump.

The hydraulic motor 6 is a swash plate type axial piston motor whose capacity is changed according to the tilt angle of a swash plate (not shown). 6a and a tilt angle adjustment mechanism 6b for adjusting the tilt angle of the swash plate.

The rotation sensor 6a outputs a signal to the controller 20 according to the detected rotation direction and rotation speed of the output shaft. The rotation speed and rotation direction of the hydraulic motor 6 detected by the rotation sensor 6a are correlated with the rotation speed and rotation direction of the mixer drum 2 as described later.

The tilt angle adjusting mechanism 6b has a hydraulic actuator (not shown) that changes the tilt angle of the swash plate, and a solenoid valve (not shown) that controls the working oil pressure guided to the hydraulic actuator. The tilting angle of the swash plate changes according to the current value supplied from the controller 20 to the solenoid valve, and the capacity of the hydraulic motor 6 is changed.

In addition, the hydraulic motor 6 is not limited to the motor of the above type, and may be any type of hydraulic motor. For example, the hydraulic motor 6 may be a swash plate type axial piston motor whose capacity is switched between a small capacity for high-speed rotation and a large capacity for normal rotation.

In the drive device 4 configured as described above, the hydraulic motor 6 is rotated by supplying the hydraulic oil discharged from the hydraulic pump 5 to the hydraulic motor 6, and the amount of oil supplied and the tilt angle of the swash plate of the hydraulic motor 6 are measured. , the rotational speed of the hydraulic motor 6 is changed. Further, the rotation direction of the hydraulic motor 6 is switched by switching the position of the control valve 5a of the hydraulic pump 5. FIG.

The output shaft of the drive device 4 , that is, the output shaft of the hydraulic motor 6 is connected to the rotating shaft O of the mixer drum 2 via the reduction gear 7 . Therefore, by increasing or decreasing the rotational speed of the hydraulic motor 6, the rotational speed of the mixer drum 2 can be increased or decreased. It is possible to switch between one agitation direction and a counter-rotating discharge direction.

As described above, since the rotation speed and rotation direction of the mixer drum 2 are correlated with the rotation speed and rotation direction of the hydraulic motor 6, the rotation speed and rotation direction of the mixer drum 2 can be grasped from the detection value of the rotation sensor 6a of the hydraulic motor 6. It is possible to It should be noted that the rotation sensor 6a may detect the number of revolutions and the direction of rotation of the mixer drum 2 instead of the hydraulic motor 6 .

When the mixer drum 2 is rotationally driven in the stirring direction, the ready-mixed concrete in the mixer drum 2 moves forward while being stirred by the drum blades. On the other hand, when the mixer drum 2 is rotationally driven in the discharging direction, the ready-mixed concrete in the mixer drum 2 moves backward while being stirred by the drum blades.

By rotating the mixer drum 2 in the discharge direction opposite to the stirring direction in this way, the ready-mixed concrete can be discharged from the opening 2 a of the mixer drum 2 . The ready-mixed concrete discharged from the mixer drum 2 is guided to a predetermined position through the flow guide 17 and the chute 18 .

When the ready-mixed concrete is charged into the mixer drum 2 via the hopper 16, the mixer drum 2 is rotated in the stirring direction at a higher speed than during stirring, so that the charged ready-mixed concrete is quickly moved to the front of the mixer drum 2. move.

(control system)
The mixer truck 1 is provided with a control system 100 that controls the mixer drum 2 of the mixer truck 1 . As shown in FIG. 3, the control system 100 has a controller 20, a display device 30, a first operating panel 41, a second operating panel 42, a third operating panel 43, and a fourth operating panel 44. .

(controller)
The controller 20 is a computer that controls the operation of the mixer drum 2 by controlling the driving device 4 . The controller 20 is composed of, for example, a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an I/O interface (input/output interface), and the like. The RAM stores data in CPU processing, the ROM stores CPU control programs and the like in advance, and the I/O interface is used for inputting and outputting information with connected devices. The operation of the driving device 4 is controlled by causing the CPU, RAM, etc. to operate according to the programs stored in the ROM.

As described above, the controller 20 is connected with the rotation sensor 6a of the hydraulic motor 6, the rotation sensor 10b of the engine 10, and the pressure sensor 5c of the hydraulic pump 5, and the detection values detected by these sensors are is entered. As described above, the controller 20 is connected to the solenoid valve of the tilt angle adjusting mechanism 5b, the solenoid valve of the tilt angle adjusting mechanism 6b, the control valve 5a, and the throttle valve 10a. A command value for actuation is output from the controller 20 . The controller 20 is connected to the rotation sensor 6a, the rotation sensor 10b, the pressure sensor 5c, each solenoid valve, the control valve 5a, and the throttle valve 10a by wire (wiring), and transmits and receives information by wire communication. However, it is not limited to this, and may be connected wirelessly, and information may be transmitted and received by wireless communication.

(Display device)
The display device 30 is a display that displays images, and displays the operating state of the mixer drum 2, for example. The display device 30 is arranged in the operator's cab 11 and is preferably installed at a position within the operator's cab 11 that is easy for the operator to see. For example, in addition to a monitor for displaying images, the display device 30 includes a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), and an I/O interface ( input/output interface) and the like.

The display device 30 is connected to the controller 20 and transmits and receives information (signals) to and from the controller 20 . In this embodiment, the display device 30 is connected to the controller 20 via a CAN (Controller Area Network), and image data generated by the CPU of the controller 20 is transmitted to the display device 30 via the CAN, An image is displayed on the monitor of the display device 30 . Note that image data may be generated by the CPU of the display device 30 based on a signal transmitted from the controller 20 . The display device 30 is connected to the controller 20 by wire (wiring), and transmits and receives information by wire communication. You may send and receive. Moreover, the display device 30 and the controller 20 may be connected via a communication network using a communication standard other than CAN.

The display device 30 is connected to an output terminal 21 for outputting a vehicle speed signal corresponding to the speed of the mixer truck 1 and a parking brake switch 22 for detecting the operating state of the parking brake. is entered. That is, in this embodiment, the controller 20 is not directly connected to the output terminal 21 and the parking brake switch 22, but is connected to the output terminal 21 and the parking brake switch 22 via the display device 30. The output terminal 21 is provided on the engine 10 side and is an interface for connecting with the control system 100 side. The output terminal 21 is connected to a vehicle speed sensor 21A provided on the engine 10 . The vehicle speed sensor 21A detects the rotation of the engine 10 as a vehicle speed signal, and the output terminal 21 outputs the vehicle speed signal detected by the vehicle speed sensor 21A to a connection destination. The display device 30 is connected to the output terminal 21 and the parking brake switch 22 by wire (wiring), and transmits and receives information by wire communication. , information may be transmitted and received wirelessly.

As described above, in the present embodiment, the devices for obtaining vehicle-related data, such as the output terminal 21 and the parking brake switch 22 , are not directly connected to the controller 20 but are connected to the display device 30 . As a result, the number of connections (here, the number of wires) between the devices that acquire vehicle-related data and the controller 20 can be reduced, which is preferable. In particular, when a device that acquires vehicle-related data is connected to the controller 20 by wire, the length of the wire becomes long, so reducing the number of wires is particularly effective. Transmission and reception of information between a device that acquires vehicle-related data and the controller 20 is collectively performed between the display device 30 and the controller 20 .

Moreover, the display device 30 may have only a display function without having a microcomputer. In addition, the installation position of the display device 30 is not limited to the inside of the driver's cab 11, and any place that is easy for the operator to see, for example, the vicinity of the rear of the vehicle where the second control panel 42 (described later) is arranged. good too. Also, a plurality of display devices 30 may be provided in the vehicle.

(First control panel)
The first operation panel 41 is an input device that receives an operator's input (operation) for controlling the operation of the mixer drum 2 . The first operation panel 41 is connected to the controller 20 and transmits and receives information (signals) to and from the controller 20 . The first operation panel 41 is directly connected to the controller 20 without going through the display device 30 . The first operation panel 41 is connected to the controller 20 by wire (wiring), and transmits and receives information by wire communication. Information may be sent and received.

In this embodiment, the first operation panel 41 is provided with a potentiometer 41a and an emergency stop switch 41b.

The potentiometer 41a is a user interface for changing the rotational direction and rotational speed of the mixer drum 2, and receives a rotation control input for controlling the rotation of the mixer drum 2 by the operator. The potentiometer 41a is of a dial knob type in this embodiment. The first operation panel 41 detects a rotation control input to the potentiometer 41 a by the operator and outputs information indicating the contents of the rotation control input to the controller 20 . The controller 20 controls the operation of the mixer drum 2 based on information indicating the content of the rotation control input.

The emergency stop switch 41b is a user interface for stopping the rotation of the mixer drum 2, and receives an emergency stop input, which is an input for stopping the rotation of the mixer drum 2 by the operator. The first operation panel 41 detects an emergency stop input to the emergency stop switch 41b by the operator, and outputs information to the controller 20 that the emergency stop input has been detected. The controller 20 stops the rotation of the mixer drum 2 when it acquires the information indicating that the emergency stop input has been detected.

(Second control panel)
The second operation panel 42 is an input device that receives an operator's input (operation) for controlling the operation of the mixer drum 2 . The second operation panel 42 is connected to the controller 20 and transmits and receives information (signals) to and from the controller 20 . The second operation panel 42 is directly connected to the controller 20 without going through the display device 30 . The second operation panel 42 is connected to the controller 20 by wire (wiring), and transmits and receives information by wire communication. Information may be sent and received.

In this embodiment, the second operation panel 42 is provided with a potentiometer 42a and an emergency stop switch 42b.

The potentiometer 42a, like the potentiometer 41a of the first operation panel 41, receives a rotation control input by the operator. The second operation panel 42 detects a rotation control input to the potentiometer 42 a by the operator and outputs information indicating the content of the rotation control input to the controller 20 . The controller 20 controls the operation of the mixer drum 2 based on information indicating the content of the rotation control input.

The emergency stop switch 42b, like the emergency stop switch 41b of the first operation panel 41, receives an emergency stop input by the operator. The second operation panel 42 detects an emergency stop input to the emergency stop switch 42b by the operator and outputs information to the controller 20 to the effect that the emergency stop input has been detected. The controller 20 stops the rotation of the mixer drum 2 when it acquires the information indicating that the emergency stop input has been detected.

The second operation panel 42 is provided outside the driver's cab 11 in this embodiment. Furthermore, as shown in FIG. 1, the second operation panel 42 is provided to allow the mixer truck 1 to be operated while observing the amount of ready-mixed concrete discharged through the chute 18 to the right side of the vehicle. It is provided on the right rear of the For example, when discharging ready-mixed concrete in a state in which two mixer trucks 1 are arranged side by side, while operating the second operation panel 42 provided on the right rear of one vehicle, the second operation panel 42 provided on the left rear of the other vehicle is operated. By operating the 1 operation panel 41, the ready-mixed concrete can be supplied continuously or a large amount of ready-mixed concrete can be supplied. However, the installation position of the second operation panel 42 is not limited to the right rear of the vehicle, and may be any position. Further, the second operation panel 42 may be of an installation type that is fixed to the vehicle, or may be of a detachable type that is connected to the vehicle via a cable and can be removed.

(Third control panel)
The third operation panel 43 is an input device that receives an operator's input (operation) for controlling the operation of the mixer drum 2 . The third operation panel 43 is connected to the display device 30 and transmits and receives information (signals) to and from the display device 30 . That is, the third operation panel 43 is not directly connected to the controller 20 but connected to the controller 20 via the display device 30 . The third operation panel 43 is connected to the display device 30 by wire (wiring), and transmits and receives information by wire communication. You may send and receive information with. By transmitting the operation signal of the third operation panel 43 to the controller 20 via the display device 30 in this way, the wiring for connecting the third operation panel 43 and the controller 20 is not required. Since the number of wires routed from the controller 20 is reduced, the degree of freedom in arranging the display device 30 and the third operation panel 43 is improved, and the display device 30 and the third operation panel 43 are arranged at positions where the operator can easily work. can be placed. As a result, it is possible to improve the operability of the mixer drum 2 by the operator.

In this embodiment, the third operation panel 43 is provided with a potentiometer 43a, an emergency stop switch 43b, and an automatic stirring switch 43c.

The potentiometer 43a, like the potentiometer 41a of the first operation panel 41, receives a rotation control input by the operator. The third operation panel 43 detects a rotation control input to the potentiometer 43 a by the operator and outputs information indicating the contents of the rotation control input to the display device 30 . The display device 30 transmits information indicating the content of the rotation control input acquired from the third operation panel 43 to the controller 20 . The controller 20 controls the operation of the mixer drum 2 based on the information indicating the content of the rotation control input acquired from the display device 30 .

The emergency stop switch 43b, like the emergency stop switch 41b of the first operating panel 41, receives an emergency stop input from the operator. The third operation panel 43 detects an emergency stop input to the emergency stop switch 43b by the operator, and outputs information to the display device 30 to the effect that the emergency stop input has been detected. The display device 30 transmits to the controller 20 information indicating that an emergency stop input has been detected, which is acquired from the third operation panel 43 . The controller 20 stops the rotation of the mixer drum 2 when it acquires the information indicating that the emergency stop input has been detected from the display device 30 .

The automatic stirring switch 43c is a user interface for automatically stirring the mixer drum 2, and receives automatic stirring input, which is an input for executing automatic stirring of the mixer drum 2 by the operator. The execution procedure of automatic stirring will be described later.

In this embodiment, the third operation panel 43 is provided inside the driver's cab 11 in order to enable operation of the mixer drum 2 even while the vehicle is running. However, the installation position of the third operating panel 43 is not limited to the interior of the operator's cab 11 and may be any position. Further, the third operation panel 43 may be of an installation type that is fixed to the vehicle, or may be of a detachable type that is connected to the vehicle via a cable and can be removed.

(4th control panel)
The fourth operation panel 44 is an input device that receives an operator's input (operation) for controlling the operation of the mixer drum 2 . The fourth operation panel 44 is connected to the controller 20 and transmits and receives information (signals) to and from the controller 20 . The fourth operation panel 44 is directly connected to the controller 20 without going through the display device 30 . The fourth operation panel 44 is connected to the controller 20 by wire (wiring), and transmits and receives information by wire communication. Information may be sent and received.

In this embodiment, the fourth operation panel 44 is provided with a potentiometer 44a and an emergency stop switch 44b.

The potentiometer 44a, like the potentiometer 41a of the first operation panel 41, receives a rotation control input by the operator. The fourth operation panel 44 detects a rotation control input to the potentiometer 44 a by the operator and outputs information indicating the content of the rotation control input to the controller 20 . The controller 20 controls the operation of the mixer drum 2 based on information indicating the content of the rotation control input.

The emergency stop switch 44b, like the emergency stop switch 41b of the first operation panel 41, receives an emergency stop input by the operator. The fourth operation panel 44 detects an emergency stop input to the emergency stop switch 44b by the operator, and outputs information to the controller 20 to the effect that the emergency stop input has been detected. The controller 20 stops the rotation of the mixer drum 2 when it acquires the information indicating that the emergency stop input has been detected.

The fourth operating panel 44 is provided outside the driver's cab 11 in this embodiment. Further, as shown in FIG. 1, the fourth operation panel 44 is provided around the hopper 16, i.e., above the vehicle, so that the mixer drum 2 can be operated while checking the remaining amount of ready-mixed concrete in the mixer drum 2. provided in However, the installation position of the fourth operating panel 44 is not limited to above the vehicle, and may be any position. Further, the fourth operation panel 44 may be of an installation type that is fixed to the vehicle, or may be of a detachable type that is connected to the vehicle via a cable and can be removed.

In this embodiment, four operation panels, ie, the first operation panel 41, the second operation panel 42, the third operation panel 43, and the fourth operation panel 44 are provided. It is arbitrary without being limited to the above description.

The control system 100 is configured as described above. The control of the mixer drum 2 by the control system 100 will be described below.

When the operator inputs a rotation control input to the potentiometers 41a to 44a provided on the operation panels 41 to 44, the controller 20 controls the driving device 4 according to the rotation control input to control the rotation of the mixer drum 2. do. The potentiometers 41a to 44a provided on the respective operation panels 41 to 44 are variable resistors whose electric resistance value changes according to the amount of rotation operation, and the potentiometers 41a to 44a are rotated by the operator to control rotation. When the input is detected, the controller 20 adjusts the tilt angle of the swash plate of the hydraulic pump 5 and the rotation of the hydraulic motor 6 so that the rotation state of the mixer drum 2 is in accordance with the electrical resistance values of the potentiometers 41a to 44a. It controls the tilting angle of the swash plate, the control valve 5 a of the hydraulic pump 5 , and other mechanisms that make up the driving device 4 .

For example, when the operator rotates the potentiometer 43a in the clockwise direction on the third operation panel 43, the controller 20 rotates the mixer drum 2 in the stirring direction at a rotational speed corresponding to the electrical resistance value of the potentiometer 43a. . Conversely, when the operator rotates the potentiometer 43a counterclockwise, the controller 20 rotates the mixer drum 2 in the discharge direction at a rotational speed corresponding to the electrical resistance value of the potentiometer 43a. Thus, the rotation control input is an input by the operator when the operation (rotation direction and rotation speed) of the mixer drum 2 is performed by the operator, and when the mixer drum 2 performs an operation other than automatic stirring described later. can be said to be input by the operator.

As described above, the mixer truck 1 is provided with a plurality of operation panels 41 to 44. When the potentiometers 41a to 44a of the respective operation panels 41 to 44 are operated simultaneously, the controller 20 determines which operation should be prioritized. Since it cannot be determined, the operation of the mixer drum 2 may be set to be performed by one operation panel that has acquired the operation right.

Specifically, for example, when the potentiometer 42a of the second operation panel 42 is once rotated to the maximum position and then returned to the neutral position, the operation right is given to the second operation panel 42, and the mixer drum 2 is operated thereafter. can be performed by the second operation panel 42. While the potentiometer 42a of the second operation panel 42 to which the operation right is given is being operated, it becomes impossible to operate it with other operation panels. With the potentiometer 42a of the second operation panel 42 returned to the neutral position, another operation panel, for example, the potentiometer 43a of the third operation panel 43, is once rotated to the maximum position and then returned to the neutral position. The right to operate is transferred to the third operation panel 43 .

Information on the operation panel that has the right to operate and the operation status of the mixer drum 2 may be displayed on the display device 30 .

Further, the controller 20 performs automatic stirring by rotating the mixer drum 2 in the stirring direction when the parking brake is not activated and the vehicle speed signal indicates that the mixer truck 1 is running. More specifically, when the operator wishes to perform automatic stirring, the operator operates the automatic stirring switch 43c of the third control panel 43 in the operator's cab 11 to turn on the automatic stirring switch 43c. When the automatic stirring switch 43c is turned on, the third operation panel 43 detects an automatic stirring input indicating that automatic stirring can be executed, and transmits information to the display device 30 to the effect that the automatic stirring input has been obtained. do. When the mixer truck 1 is driven, the operator turns off the parking brake (a state in which the parking brake is not operated) and drives the mixer truck 1 . The parking brake switch 22 detects that the parking brake has been turned off, and the display device 30 acquires from the parking brake switch 22 parking-off information indicating that the parking brake is not operating. Further, the vehicle speed sensor 21A sequentially detects the vehicle speed of the mixer truck 1, and the display device 30 acquires a vehicle speed signal indicating the vehicle speed of the mixer truck 1 via the output terminal 21. FIG. The display device 30 transmits to the controller 20 the information indicating that the automatic stirring input has been acquired from the automatic stirring switch 43c, the parking-off information acquired from the parking brake switch 22, and the vehicle speed signal acquired from the output terminal 21. do. When the controller 20 acquires the information indicating that the automatic stirring input has been acquired and the parking-off information, and the acquired vehicle speed signal indicates that the mixer truck 1 is running, the controller 20 performs automatic stirring. to start.

In addition, when the controller 20 determines that the mixer truck 1 is running, it is preferable in principle to prohibit operation of the potentiometers by the operation panels 41 to 44 in order to prevent the discharge of ready-mixed concrete. That is, when the mixer truck 1 is running, the controller 20 does not accept rotation control inputs to the operation panels 41 to 44, and even if the potentiometers of the operation panels 41 to 44 are operated, It is preferable not to rotate the mixer drum 2 accordingly.

(vehicle speed detection system)
Here, the vehicle speed signal is acquired via the output terminal 21 as described above. However, since the specifications of the output terminal 21 and the vehicle speed sensor 21A may vary depending on the vehicle type of the mixer truck 1, it is required to appropriately receive the vehicle speed signal according to the vehicle type. On the other hand, in the present embodiment, a vehicle speed detection system 50 capable of switching the connection of the detection circuit for the vehicle speed signal is provided in order to appropriately receive the vehicle speed signal according to the vehicle type. The vehicle speed detection system 50 will be described below.

First, the vehicle speed signal will be explained. FIG. 4 is a graph showing an example of a vehicle speed signal. As shown in FIG. 4, in the example of this embodiment, the vehicle speed signal is a pulse-shaped waveform signal. The frequency of the vehicle speed signal changes according to the rotational speed of the engine 10, and the higher the rotational speed, the higher the frequency (that is, the shorter the cycle T).

FIG. 5 is a schematic circuit diagram of the vehicle speed detection system. As shown in FIG. 5 , the vehicle speed detection system 50 has a vehicle speed signal detection circuit 52 and a switching control section 54 . In this embodiment, the vehicle speed detection system 50 is provided in the display device 30 . However, the vehicle speed detection system 50 is not limited to being provided in the display device 30 and may be hardware separate from the display device 30 .

A vehicle speed signal detection circuit 52 is a circuit connected to the output terminal 21 . The vehicle speed signal detection circuit 52 has a receiving section 60 , a power supply 62 and a switching section 64 .

The receiver 60 is a circuit (detection circuit) connected to the output terminal 21 and can receive the vehicle speed signal output from the output terminal 21 . The receiving section 60 is connected to the output terminal 21 by the wiring L1. In this embodiment, the receiver 60 is provided in the display device 30, but may be a circuit provided separately from the display device 30. FIG.

The switching unit 64 is a switch unit that switches connection of the vehicle speed signal detection circuit 52, and is a multiplexer in this embodiment. The switching section 64 has a first switching section 64A and a second switching section 64B. The switching unit 64 is provided in the display device 30 , but may be a multiplexer circuit provided separately from the display device 30 .

The first contact 64AS1 of the first switching section 64A is connected to the receiving section 60 via the wiring L2. A resistor R2 is provided on the wiring L2. In the first switching section 64A, the second contact 64AS2 is grounded through the wiring L3, and the third contact 64AS3 is connected to the power supply 62 through the wiring L4. The power supply 62 is a supply source that supplies electric power, such as a battery. The power source 62 is a power source for the display device 30 that also supplies power to the display device 30 , but is not limited to being a power source for the display device 30 .

The first switching section 64A has a switch section 64A1 and an input section 64A2. The switch part 64A1 connects the first contact 64AS1 and the second contact 64AS2, disconnects the first contact 64AS1 and the third contact 64AS3, and connects the first contact 64AS1 and the third contact 64AS3. It is a switch capable of switching between a second state in which the first contact 64AS1 and the second contact 64AS2 are disconnected. The input unit 64A2 is a mechanism that operates the switch unit 64A1 under the control of the switching control unit 54 to switch the switch unit 64A1 between the first state and the second state. The first state is a state in which the receiving section 60 (output terminal 21) and the power source 62 are disconnected, and the second state is a state in which the output terminal 21 and the power source 62 are connected via the receiving section 60. It can also be said. In the present embodiment, the circuit configuration is such that the output terminal 21 and the power supply 62 are connected via the receiving section 60 in the second state, but the circuit configuration is not limited to the above description, and the output in the first state Any circuit configuration may be employed in which the terminal 21 and the power source 62 are connected and the output terminal 21 and the power source 62 are disconnected in the second state.

In the second switching section 64B, the first contact 64BS1 is connected to the point P between the output terminal 21 of the wiring L1 and the receiving section 60 by the wiring L5. In the second switching portion 64B, the second contact 64BS2 is grounded by the wiring L6, and the third contact 64BS3 is not connected (floats) to the wiring or circuit. A resistor R3 is provided on the wiring L6. It can also be said that the resistor R3 is provided in parallel with the output terminal 21 and the receiving section 60 .

The second switching section 64B has a switch section 64B1 and an input section 64B2. The switch part 64B1 connects the first contact 64BS1 and the second contact 64BS2 and connects the first contact 64BS1 and the third contact 64BS3 to a third state in which the first contact 64BS1 and the third contact 64BS3 are disconnected. It is a switch capable of switching between a fourth state in which the first contact 64BS1 and the second contact 64BS2 are disconnected. The input unit 64B2 is a mechanism that operates the switch unit 64B1 under the control of the switching control unit 54 to switch the switch unit 64B1 between the third state and the fourth state. The third state is a state in which the point P is connected to the resistor R3, and the fourth state can be said to be a state in which the point P is not connected to the resistor R3.

The switching control unit 54 is a computer (microcomputer) including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), an I/O interface (input/output interface), and the like. The switching control unit 54 is a computer provided in the display device 30 , but may be a computer separate from the display device 30 .

The switching control unit 54 controls the switching of the connection state of the vehicle speed signal detection circuit 52 by the switching unit 64 so that the receiving unit 60 can receive the vehicle speed signal. The switching control section 54 operates the switch section 64A1 via the input section 64A2 of the first switching section 64A to switch between the first state and the second state. Also, the switching control section 54 operates the switch section 64B1 via the input section 64B2 of the second switching section 64B to switch between the third state and the fourth state.

(switching process)
The switching process of the connection state of the vehicle speed signal detection circuit 52 by the switching control unit 54 will be described below.

When the switching process is performed, the control system 100 including the vehicle speed detection system 50 is attached to the truck mixer 1 . That is, the wiring L1 of the vehicle speed signal detection circuit 52 is connected to the output terminal 21 of the mixer truck 1, and the receiving section 60 and the output terminal 21 are connected via the wiring L1. When performing the switching process, as shown in FIG. 5, the vehicle speed signal detection circuit 52 is in the first state in which the receiving section 60 is grounded and not connected to the power source 62, and the point P is the resistor R3. is in the third state in which it is connected to . Note that the point P may be in a fourth state in which it is not connected to the resistor R3. Then, with the vehicle speed signal detection circuit 52 connected to the output terminal 21 as shown in FIG. 5, the mixer truck 1 is run for test. The switching control unit 54 detects the reception state of the vehicle speed signal of the receiving unit 60 while the mixer truck 1 is running for test, and changes the connection state of the vehicle speed signal detection circuit 52 according to the reception state of the vehicle speed signal. switch. The process of running the mixer truck 1 for test driving and switching the connection state of the vehicle speed signal detection circuit 52 is performed, for example, before shipment of the mixer truck 1, for example, as a calibration.

Here, for the mixer truck 1, there is a vehicle type that cannot output a vehicle speed signal from the output terminal 21 unless a current is supplied to the output terminal 21, and a vehicle type that can output a vehicle speed signal from the output terminal 21 without supplying a current to the output terminal 21. There is a car model. For vehicles that cannot output a vehicle speed signal from the output terminal 21 without supplying current, the output terminal 21 has an open-collector specification. 21 can be said to have emitter follower specifications. In the open collector specification, even if the mixer truck 1 is run for test in the first state, the output terminal 21 is not connected to the power source 62 , so the vehicle speed signal is not output from the output terminal 21 to the receiver 60 . Therefore, when the mixer vehicle 1 is running for a test run, if the receiving unit 60 does not receive the vehicle speed signal, the output terminal 21 is of open collector specification, and if the receiving unit 60 receives the vehicle speed signal, , it can be determined that the output terminal 21 is of the emitter follower specification. In this embodiment, using this principle, the switching control unit 54 switches to the first state or the second state based on whether or not the receiving unit 60 receives the vehicle speed signal while the mixer truck 1 is running for a test run. decide whether to A specific description will be given below.

If the receiving unit 60 does not receive the vehicle speed signal while the mixer truck 1 is running for test, the switching control unit 54 switches the first switching unit 64A to the second state and switches the second switching unit 64B to the second state. Switch to the fourth state. As a result, the power supply 62 is connected to the output terminal 21 via the receiving section 60 , so that the output terminal 21 can output the vehicle speed signal to the receiving section 60 . That is, when the receiver 60 does not detect the vehicle speed signal while the mixer truck 1 is running for test, the switching control unit 54 determines that the open collector specification is used, and connects the power source 62 and the output terminal 21 . do. As a result, the receiving unit 60 can appropriately receive the vehicle speed signal in the open-collector vehicle type. Although the second switching section 64B is set to the fourth state here, the state of the second switching section 64B is not limited to the fourth state and may be any state. Further, the switching of the first switching section 64A and the second switching section 64B may be performed during the test run or after the test run.

On the other hand, if the receiving unit 60 receives the vehicle speed signal while the mixer truck 1 is running for test, the switching control unit 54 keeps the first switching unit 64A in the first state. That is, when the receiver 60 detects the vehicle speed signal while the mixer truck 1 is running for a test run, the switching control unit 54 sets the power supply 62 and the output terminal 21 to a non-connected state assuming that the emitter follower specification is used. to As a result, the receiving unit 60 can appropriately receive the vehicle speed signal in the emitter follower vehicle type.

Furthermore, in the mixer vehicle 1 whose output terminal 21 is of emitter follower specification, it is necessary to connect an intermediate resistor between the output terminal 21 and the receiving section 60 in order to appropriately output the vehicle speed signal from the output terminal 21. There may be some vehicle models that do not require an intermediate resistor to be connected. The specifications of the vehicle speed sensor 21A differ between vehicle types that require an intermediate resistance and vehicle types that do not require an intermediate resistance. Furthermore, the number of pulses generated by the vehicle speed sensor 21A per engine revolution for vehicles requiring intermediate resistance is greater than the number of pulses generated by the vehicle speed sensor 21A per engine revolution for vehicles requiring no intermediate resistance. , is increasing. In the present embodiment, utilizing this point, the switching control unit 54 switches the second switching unit 64B to the third state based on the frequency of the vehicle speed signal received by the receiving unit 60 during test running of the truck mixer 1. It is determined whether the state should be the fourth state. A specific description will be given below.

Specifically, the switching control unit 54 controls the vehicle speed signal received by the receiving unit 60 after a predetermined time has elapsed since the mixer truck 1 started test driving (in this example, the speed is faster than 0 km/h and less than 10 km/h). Based on the frequency of , an estimated value of the speed of the mixer truck 1 after a predetermined time has passed since the start of the test run is calculated. The predetermined time may be set arbitrarily, such as one second. Further, the switching control unit 54 is not limited to using the frequency of the vehicle speed signal received by the receiving unit 60 after a predetermined time has passed since the mixer truck 1 started the test run. , the frequency of the vehicle speed signal at a predetermined speed may be used. In this case, when the vehicle reaches a predetermined speed, a switch or the like may be used to obtain the frequency of the vehicle speed signal at the predetermined speed. The speed of the mixer truck 1 can be calculated from the number of pulses per revolution of the engine 10 and the frequency, for example, using the following equation (1).

V=3600H/(nN) (1)

In equation (1), V is the speed (km/h), 3600 is 60 seconds x 60 (km/h), H is the frequency (Hz), and n is the engine drive shaft per rotation. is the number of pulses of the vehicle speed sensor 21A, and N is the vehicle speed sensor drive rotation speed (rpm) when the vehicle speed is 60 km/h.

Here, since the number of pulses per engine revolution differs for each vehicle type as described above, in calculating the estimated value of the speed of the mixer truck 1, a predetermined number of pulses used for the calculation is set in advance. Based on the frequency of the vehicle speed signal received by the receiving unit 60 after a predetermined period of time has passed since the mixer truck 1 started test running, and the predetermined number of pulses, the switching control unit 54 determines whether the vehicle mixer 1 has started the test running for a predetermined period of time. An estimated value of the speed of the mixer truck 1 after the passage of time is calculated. Then, the switching control unit 54 determines whether the third state or the fourth state should be set based on the calculated estimated value of the speed of the mixer truck 1 .

Specifically, when the estimated value of the speed of the mixer truck 1 is lower than a predetermined threshold value, the switching control unit 54 determines that the vehicle type requires an intermediate resistance (that is, the vehicle type has a large number of pulses per engine rotation). , the second switching unit 64B is set to the third state. As a result, the point P between the output terminal 21 of the wiring L1 and the receiving section 60 is connected to the intermediate resistor R3. Therefore, even in a vehicle model that requires an intermediate resistance, the receiving unit 60 can appropriately receive the vehicle speed signal. When calculating the estimated speed with a fixed number of pulses, the number of pulses per engine revolution is higher than that of vehicle models that do not require intermediate resistance (vehicles that require more pulses per engine revolution). The estimated value of the speed tends to be calculated higher for a vehicle type with a smaller number of pulses. Therefore, by making a judgment based on the fact that the estimated value of the speed of the mixer truck 1 is lower than a predetermined threshold value, it is possible to appropriately judge that the vehicle type requires an intermediate resistance. It should be noted that the threshold value may be set to a speed that the vehicle type that does not require intermediate resistance reliably exceeds the speed during running, and may be set arbitrarily, for example, 10 km/h.

On the other hand, when the estimated value of the speed of the mixer truck 1 is equal to or greater than the predetermined threshold value, the switching control unit 54 determines that the vehicle type requires an intermediate resistance (that is, the vehicle type requires a small number of pulses per engine rotation). The second switching section 64B is set to the fourth state. That is, for example, when the speed one second after the start of the test run is several tens of km/h or the like, which is higher than the generally assumed speed, the speed is calculated by fixing the predetermined number of pulses. Therefore, it is determined that the vehicle type does not require an intermediate resistance, assuming that the estimated value of the speed is calculated as a value higher than the actual value. As a result, the point P between the output terminal 21 of the wiring L1 and the receiving section 60 is disconnected from the intermediate resistor R3. Therefore, even in a vehicle type that does not require an intermediate resistance, the receiving unit 60 can appropriately receive the vehicle speed signal.

It should be noted that the criterion for determining whether to set the third state or the fourth state is not limited to the estimated value of the speed as described above. For example, it may be determined whether the third state or the fourth state should be set based on the frequency of the vehicle speed signal, the number of pulses in a predetermined period of time, or the like. In this case, for example, when the number of pulses at the frequency or at the predetermined time is equal to or greater than the threshold value, the switching control unit 54 determines that the vehicle model requires an intermediate resistance, and sets the second switching unit 64B to the third state. If the number of pulses is less than the threshold, the second switching unit 64B may be set to the fourth state, assuming that the vehicle type does not require an intermediate resistance.

Next, a flow of processing for switching the connection state of the vehicle speed signal detection circuit 52 described above will be described. FIG. 6 is a flow chart for explaining the switching processing flow of the connection state of the vehicle speed signal detection circuit. When switching the connection state, the vehicle speed signal detection circuit 52 is connected to the output terminal 21 and the first switching unit 64A is set to the first state (the power source 62 is disconnected), and the mixer truck 1 is operated. Make a test run. Then, the switching control section 54 determines whether or not the receiving section 60 has detected the vehicle speed signal during the test run (step S10). When the receiving unit 60 does not detect the vehicle speed signal (step S10; No), the switching control unit 54 sets the first switching unit 64A to the second state (the state in which the power supply 62 is connected) assuming that the open collector specification is used. The second switching section 64B is set to the fourth state (disconnected to the resistor R3) (step S12). On the other hand, if the receiving unit 60 detects the vehicle speed signal (step S10; Yes), the switching control unit 54 estimates the vehicle speed from the frequency of the vehicle speed signal and the predetermined number of pulses after a predetermined period of time has passed since the start of the test run. A value is calculated (step S14). The switching control unit 54 determines whether the estimated value of the vehicle speed is equal to or higher than the threshold value (step S16), and if the estimated value of the vehicle speed is lower than the threshold value (step S16; No), it is determined that the vehicle type requires intermediate resistance. , the first switching section 64A is set to the first state (the power supply 62 is disconnected), and the second switching section 64B is set to the third state (connected to the resistor R3) (step S18). On the other hand, if the estimated value of the vehicle speed is equal to or greater than the threshold (step S16; Yes), the switching control unit 54 sets the first switching unit 64A to the first state (the power supply 62 is state), and the second switching unit 64B is set to the fourth state (the state in which it is not connected to the resistor R3) (step S20). This processing ends by executing steps S12, S18, and S20. Note that once the connection state of the vehicle speed signal detection circuit 52 is determined, it does not need to be changed. In step S16, determination is made based on whether the estimated value of the vehicle speed is equal to or greater than the threshold, but the determination is not limited to this. For example, step S20 may be executed when the estimated value of the vehicle speed is higher than the threshold value in step S16, and step S18 may be executed when the estimated value of the vehicle speed is equal to or less than the threshold value in step S16.

(effect)
As described above, the vehicle speed detection system 50 according to this embodiment detects the speed of the mixer truck 1 and has the vehicle speed signal detection circuit 52 and the switching control section 54 . The vehicle speed signal detection circuit 52 has a receiving section 60 connected to the output terminal 21 that outputs a vehicle speed signal corresponding to the speed of the mixer truck 1 and a switching section 64 that switches the connection state of the vehicle speed signal detection circuit 52 . The switching control unit 54 controls the switching of the connection state of the mixing vehicle 1 by the switching unit 64 according to the reception status of the vehicle speed signal of the receiving unit 60 while the mixing vehicle 1 is running. is ready to receive the vehicle speed signal.

Here, since the specifications of the output terminal 21 and the vehicle speed sensor 21A may vary depending on the vehicle type of the mixer truck 1, it is required to appropriately receive the vehicle speed signal according to the vehicle type. On the other hand, the vehicle speed detection system 50 according to the present embodiment is provided with a vehicle speed signal detection circuit 52 connected to the output terminal 21, and receives the vehicle speed signal of the receiver 60 when the mixer truck 1 is actually run for a test run. The connection of the vehicle speed signal detection circuit 52 is switched according to the situation. Therefore, according to the present embodiment, the vehicle speed signal detection circuit 52 can be brought into a connected state according to the vehicle type, and the vehicle speed signal can be appropriately received according to the vehicle type. In addition, according to the vehicle speed detection system 50, the circuit configuration is automatically set so that the vehicle speed signal can be properly received according to the vehicle type. It is also possible to suppress the setting.

The vehicle speed signal detected by the vehicle speed detection system 50 is used to determine whether the mixer truck 1 is stopped or running when automatic stirring or the like is started as described above. Further, for example, the vehicle speed signal may be used to calculate the recommended timing for maintenance. In this case, for example, the controller 20 or the display device 30 calculates the integrated value of the traveling distance of the mixer truck 1 from the vehicle speed calculated based on the vehicle speed signal and the traveling time. Then, when the accumulated value of the traveled distance exceeds a predetermined time, it is determined that the recommended time for maintenance has been reached. For example, the display device 30 may display a notification to the effect that maintenance is recommended on the monitor.

The switching unit 64 can switch between a first state in which the output terminal 21 and the power source 62 are disconnected and a second state in which the output terminal 21 and the power source 62 are connected. When the receiving unit 60 does not receive the vehicle speed signal while the mixer truck 1 is running for test in the first state, the switching control unit 54 sets the switching unit 64 to the second state so that the mixer truck 1 is running for test. When the receiving unit 60 receives the vehicle speed signal while the vehicle is on, the switching unit 64 is set to the first state. According to this embodiment, it is possible to appropriately receive the vehicle speed signal both in the case of the open collector specification and in the case of the emitter follower specification.

The switching section 64 can switch between a third state in which the resistor R3 provided in parallel between the output terminal 21 and the receiving section 60 is connected, and a fourth state in which the resistor R3 is disconnected. The switching control unit 54 determines whether the switching unit 64 should be in the third state or the fourth state based on the frequency of the vehicle speed signal received by the receiving unit 60 while the mixer truck 1 is running in the first state. to decide. According to this embodiment, it is possible to appropriately receive the vehicle speed signal in both vehicle types that do not require an intermediate resistance and vehicles that require an intermediate resistance.

Further, the switching control unit 54 calculates an estimated value of the speed of the mixer truck 1 based on the frequency of the vehicle speed signal when the mixer truck 1 starts running and a predetermined number of pulses set in advance. When the estimated value is lower than the threshold, the switching unit 64 is set to the third state, and when the estimated value is equal to or greater than the threshold, the switching unit 64 is set to the fourth state. According to this embodiment, it is possible to appropriately receive the vehicle speed signal in both vehicle types that do not require an intermediate resistance and vehicles that require an intermediate resistance.

Although the vehicle speed detection system 50 according to the present embodiment is mounted on the mixer truck 1 and detects the vehicle speed of the mixer truck 1, the vehicle speed detection system 50 is not limited to the mixer truck 1 and detects the vehicle speed of any vehicle. It's okay.

Although the embodiments and examples of the present invention have been described above, the embodiments are not limited by the contents of these embodiments and the like. In addition, the components described above include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the components described above can be combined as appropriate. Further, various omissions, replacements, or modifications of components can be made without departing from the scope of the above-described embodiments.

1 mixer truck 20 controller 21 output terminal 21A vehicle speed sensor 22 parking brake switch 30 display device 50 vehicle speed detection system 52 vehicle speed signal detection circuit 54 switching control unit 60 receiving unit 62 power source 64 switching unit

Claims (4)

A vehicle speed detection system for detecting the speed of a vehicle,
a vehicle speed signal detection circuit having a receiving unit connected to an output terminal for outputting a vehicle speed signal corresponding to the speed of the vehicle; and a switching unit for switching a connection state of the circuit;
The receiving unit can receive the vehicle speed signal by controlling the switching of the connection state of the circuit by the switching unit according to the reception status of the vehicle speed signal by the receiving unit while the vehicle is running. a switching control unit that switches to a state;
having
Vehicle speed detection system. The switching unit is capable of switching between a first state in which the output terminal and the power supply are disconnected and a second state in which the output terminal and the power supply are connected,
The switching control unit sets the switching unit to the second state when the receiving unit does not receive the vehicle speed signal while the vehicle is running in the first state, and the vehicle is running. 2. The vehicle speed detection system according to claim 1, wherein the switching unit is set to the first state when the receiving unit receives the vehicle speed signal while the vehicle is moving. The switching unit is capable of switching between a third state in which a resistor provided in parallel between the output terminal and the receiving unit is connected and a fourth state in which the resistor is not connected,
The switching control unit switches the switching unit to the third state or the fourth state based on the frequency of the vehicle speed signal received by the receiving unit while the vehicle is running in the first state. 3. The vehicle speed detection system according to claim 2, which determines whether to The switching control unit calculates an estimated value of the speed of the vehicle based on the frequency of the vehicle speed signal when the vehicle starts running and a predetermined number of pulses, and the estimated value is greater than a threshold. 4. The vehicle speed detection system according to claim 3, wherein the switching unit is set to the third state when the estimated value is lower, and the switching unit is set to the fourth state when the estimated value is equal to or greater than the threshold value.

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